CA2310533A1 - Apparatus and method for automatically adjusting the path of a scintillation camera - Google Patents
Apparatus and method for automatically adjusting the path of a scintillation camera Download PDFInfo
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- CA2310533A1 CA2310533A1 CA 2310533 CA2310533A CA2310533A1 CA 2310533 A1 CA2310533 A1 CA 2310533A1 CA 2310533 CA2310533 CA 2310533 CA 2310533 A CA2310533 A CA 2310533A CA 2310533 A1 CA2310533 A1 CA 2310533A1
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- detector head
- patient
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- support
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
Abstract
Disclosed is a method and apparatus for automatically adjusting the path of a scintillation camera. The scintillation camera comprises a light source for projecting a beam of light across the detector head surface and a light detector for sensing the beam of light. A mirror reflects the beam of light into at least one set of perpendicular optical bars. When the beam of light is broken, the detector head stops moving towards the patient.
Description
APPARATUS AND METHOD FOR AUTOMATICALLY ADJUSTING THE
PATH OF A SCINTILLATION CAMERA
Field The present invention relates to the field of scintillation cameras, and specifically to a method and apparatus for automatically adjusting the path of a scintillation camera.
Background In the human body, increased metabolic activity is associated with an increase in emitted radiation. In the field of nuclear medicine, increased metabolic activity within a patient is detected using a radiation detector such as a scintillation camera.
Scintillation cameras are well known in the art, and are used for medical diagnostics. A patient ingests, or inhales or is injected with a small quantity of a radioactive isotope. The radioactive isotope emits photons that are detected by a scintillation medium in the scintillation camera. The scintillation medium is commonly a sodium iodide crystal, BGO or other. The scintillation medium emits a small flash or scintillation of light, in response to stimulating radiation, such as from a patient. The intensity of the scintillation of light is proportional to the energy of the stimulating photon, such as a gamma photon. Note that the relationship between the intensity of the scintillation of light and the gamma photon is not linear.
A conventional scintillation camera such as a gamma camera includes a detector which converts into electrical signals gamma rays emitted from a patient after radioisotope has been administered to the patient. The detector includes a scintillator and photomultiplier tubes. The gamma rays are directed to the scintillator which absorbs the radiation and produces, in response, a very small flash of light. An array of photodetectors, which are placed in optical communication with the scintillation crystal, converts these flashes into electrical signals which are subsequently processed. The processing enables the camera to produce an image of the distribution of the radioisotope within the patient.
PATH OF A SCINTILLATION CAMERA
Field The present invention relates to the field of scintillation cameras, and specifically to a method and apparatus for automatically adjusting the path of a scintillation camera.
Background In the human body, increased metabolic activity is associated with an increase in emitted radiation. In the field of nuclear medicine, increased metabolic activity within a patient is detected using a radiation detector such as a scintillation camera.
Scintillation cameras are well known in the art, and are used for medical diagnostics. A patient ingests, or inhales or is injected with a small quantity of a radioactive isotope. The radioactive isotope emits photons that are detected by a scintillation medium in the scintillation camera. The scintillation medium is commonly a sodium iodide crystal, BGO or other. The scintillation medium emits a small flash or scintillation of light, in response to stimulating radiation, such as from a patient. The intensity of the scintillation of light is proportional to the energy of the stimulating photon, such as a gamma photon. Note that the relationship between the intensity of the scintillation of light and the gamma photon is not linear.
A conventional scintillation camera such as a gamma camera includes a detector which converts into electrical signals gamma rays emitted from a patient after radioisotope has been administered to the patient. The detector includes a scintillator and photomultiplier tubes. The gamma rays are directed to the scintillator which absorbs the radiation and produces, in response, a very small flash of light. An array of photodetectors, which are placed in optical communication with the scintillation crystal, converts these flashes into electrical signals which are subsequently processed. The processing enables the camera to produce an image of the distribution of the radioisotope within the patient.
Gamma radiation is emitted in all directions and it is necessary to collimate the radiation before the radiation impinges on the crystal scintillator. This is accomplished by a collimator which is a sheet of absorbing material, usually lead, perforated by relatively narrow channels. The collimator is detachably secured to the detector head, allowing the collimator to be changed to enable the detector head to be used with the different energies of isotope to suit particular characteristics of the patient study. A
collimator may vary considerably in weight to match the isotope or study type.
Scintillation cameras are used to take four basic types of pictures: spot views, whole body views, partial whole body views, SPELT views, and whole body SPELT
mews.
A spot view is an image of a part of a patient. The area of the spot view is less than or equal to the size of the field of view of the gamma camera. In order to be able to achieve a full range of spot views, a gamma camera must be positionable at any location relative to a patient.
One type of whole body view is a series of spot views fitted together such that the whole body of the patient may be viewed at one time. Another type of whole body view is a continuous scan of the whole body of the patient. A partial whole body view is simply a whole body view that covers only part of the body of the patient. In order to be able to achieve a whole body view, a gamma camera must be positionable at any location relative to a patient in an automated sequence of views.
The acronym "SPELT" stands for single photon emission computerized tomography. A SPELT view is a series of slice-like images of the patient. The slice-like images are often, but not necessarily, transversely oriented with respect to the patient.
Each slice-like image is made up of multiple views taken at different angles around the patient, the data from the various views being combined to form the slice-like image. In 3 0 order to be able to achieve a SPELT view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken.
A whole body SPELT view is a series of parallel slice-like transverse images of a patient. Typically, a whole body SPELT view consists of sixty four spaced apart SPELT views. A whole body SPELT view results from the simultaneous generation of whole body and SPELT image data. In order to be able to achieve a whole body SPELT
view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken.
Therefore, in order that the radiation detector be capable of achieving the above four basic views, the support structure for the radiation detector must be capable of positioning the radiation detector in any position relative to the patient.
Furthermore, the support structure must be capable of moving the radiation detector relative to the patient in a controlled manner along any path.
In order to operate a scintillation camera as described above, the patient should be supported horizontally on a patient support or stretcher.
The detector head of the scintillation camera must be able to pass underneath the patient. Therefore, in order for the scintillation camera to generate images from underneath the patient, the patient support must be thin. However, detector heads are generally supported by a pair of arms which extend from a gantry. Thus, the patient support generally must be cantilevered in order for the detector head to be able to pass underneath the patient without contacting any supporting structure associated with the patient support. The design of a cantilevered patient support that is thin enough to work properly with a scintillation camera is exceedingly difficult. Expensive materials and materials that are difficult to work with, such as carbon fibre, are often used in the design of such cantilevered patient supports.
collimator may vary considerably in weight to match the isotope or study type.
Scintillation cameras are used to take four basic types of pictures: spot views, whole body views, partial whole body views, SPELT views, and whole body SPELT
mews.
A spot view is an image of a part of a patient. The area of the spot view is less than or equal to the size of the field of view of the gamma camera. In order to be able to achieve a full range of spot views, a gamma camera must be positionable at any location relative to a patient.
One type of whole body view is a series of spot views fitted together such that the whole body of the patient may be viewed at one time. Another type of whole body view is a continuous scan of the whole body of the patient. A partial whole body view is simply a whole body view that covers only part of the body of the patient. In order to be able to achieve a whole body view, a gamma camera must be positionable at any location relative to a patient in an automated sequence of views.
The acronym "SPELT" stands for single photon emission computerized tomography. A SPELT view is a series of slice-like images of the patient. The slice-like images are often, but not necessarily, transversely oriented with respect to the patient.
Each slice-like image is made up of multiple views taken at different angles around the patient, the data from the various views being combined to form the slice-like image. In 3 0 order to be able to achieve a SPELT view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken.
A whole body SPELT view is a series of parallel slice-like transverse images of a patient. Typically, a whole body SPELT view consists of sixty four spaced apart SPELT views. A whole body SPELT view results from the simultaneous generation of whole body and SPELT image data. In order to be able to achieve a whole body SPELT
view, a scintillation camera must be rotatable around a patient, with the direction of the detector head of the scintillation camera pointing in a series of known and precise directions such that reprojection of the data can be accurately undertaken.
Therefore, in order that the radiation detector be capable of achieving the above four basic views, the support structure for the radiation detector must be capable of positioning the radiation detector in any position relative to the patient.
Furthermore, the support structure must be capable of moving the radiation detector relative to the patient in a controlled manner along any path.
In order to operate a scintillation camera as described above, the patient should be supported horizontally on a patient support or stretcher.
The detector head of the scintillation camera must be able to pass underneath the patient. Therefore, in order for the scintillation camera to generate images from underneath the patient, the patient support must be thin. However, detector heads are generally supported by a pair of arms which extend from a gantry. Thus, the patient support generally must be cantilevered in order for the detector head to be able to pass underneath the patient without contacting any supporting structure associated with the patient support. The design of a cantilevered patient support that is thin enough to work properly with a scintillation camera is exceedingly difficult. Expensive materials and materials that are difficult to work with, such as carbon fibre, are often used in the design of such cantilevered patient supports.
A certain design of gantry or support structure for a scintillation camera includes a frame upon which a vertically oriented annular support rotates. Extending out from the rotating support is an elongate support. The elongate generally comprises a pair of arms.
The pair of arms generally extends through a corresponding pair of apertures in the rotating support. One end of the pair of arms supports the detector head on one side of the annular support. The other end of the pair of arms supports a counter balance weight.
Thus, the elongate support is counterbalanced with a counterweight on the opposite side of the detector head.
I 0 With such a design of support structure for a scintillation camera, a patient must lie on a horizontally oriented patient support. The patient support must be cantilevered so that the detector head can pass underneath the patient. If the detector head must pass underneath only one end of the patient, such as the patient's head, the cantilevered portion of the patient support is not long enough to cause serious difficulties in the design of the cantilevered patient support. However, if the camera must be able to pass under the entire length of the patient, the entire patient must be supported by the cantilevered portion of the patient support. As the cantilevered portion of the patient support must be thin so as not to interfere with the generation of images by the scintillation camera, serious design difficulties are encountered.
Among the advantages associated with such as design of support structure is that a patient may be partially pass through the orifice defined by the annular support so that the pair of arms need not be as long. However, the patient support must be able to support the patient in this position relative to the annular support, must be accurately positionable relative to the annular support, and must not interfere either with the rotation of the annular support or with the cables which will inevitably extend from the detector head to a nearby computer or other user control.
The detector head must also be positioned at a certain height relative to the patient. It is commonly known in the art that when the collimator to patient distance is minimized, the better the image resolution develops. However, many patients do not feel comfortable with the detector head too close to them. An ideal position must be found to ensure a good quality view is taken and to provide patient comfort.
A common method to find this position is to mount light emitters and detectors 5 to the camera. The camera is lowered toward the patient, and when a light beam produced by the emitter is broken by patient interference, the detector head is in good proximity to the patient, but still is not in the ideal position. It is common in the art for the detector to have to lower and rise relative to the patient in order to pinpoint the exact ideal height location. This 'trial and error' method is inefficient as well as hazardous.
Another problem in state of the art systems is that the light emitter and detector pairs are mounted to the collimator plate. It is known in the art that different collimator plates must be used to produce different views in varying circumstances.
Therefore, every time, the collimator plate must be changed, the light emitter and detector apparatus must be removed from the plate and mounted and reconnected to the new plate.
This is very inefficient and time consuming.
Also, commonly, the apparatus includes a plurality of light emitters and detectors mounted along the detector head to produce an array of light beams across the detector head surface. It then becomes necessary to disconnect and reconnect the plurality of emitters and detectors each time the collimator plate is changed. This design is also costly and complex to manufacture. In addition, because the apparatus is mounted to the outermost portion of the collimator plate, this design increases the collimator to patient distance.
Other system designs do not scan a patient's profile accurately since the detector head detects only one height relative to the patient. These binary systems do not allow the detector head to adjust in height according to the position of the detector head along the patient's profile. For example, the detector head tends to rise as it travels over the profile of a patient when it encounters the feet. The detector head then stays at the elevated height for the remainder of the profile scan. Since the collimator to patient distance is increased for the remainder of the scan, a view of less quality is produced.
It is therefore necessary to provide a detector head adapted for precise height determination without the use of a complicated apparatus. It would be useful if the apparatus did not contain multiple connections for light emitters and detectors. It would also be beneficial if the apparatus did not have to be removed with each change of collimator plates. It would also be an asset if the detector head did not have to rise and lower in succession in order to locate the ideal height. Finally it would be beneficial if the detector head could scan a patients' profile accurately.
Summary An object of the invention is to provide an improved method and apparatus for automatically adjusting the path of a scintillation camera.
A second object of the invention is to provide a method and apparatus that effectively meets the needs mentioned in the above statements. The invention relates to a method and apparatus for determining the ideal height of a detector head with respect to a patient's profile. The apparatus includes a laser light source for projecting a light beam across the detector head surface; a CCD for detecting the light beam, the CCD
preferably being unidirectional so that it can read the depth of beam breakage at a multiple of depths; a multiple of optical bars extending perpendicularly from the CCD;
and a mirror for reflecting the light beam as detected by the CCD element into the corresponding optical blocks for the element. In a preferred embodiment, the apparatus comprises external parts to the detector head. That apparatus is mounted across opposite sides of the detector head and not to the collimator plate. The mounting means is anything common in the art.
The light source may oscillate back and forth, or may rotate a full 360 degrees.
The CCD element to optical bar ratio may be 1:1 or any other suitable ratio.
The method includes the steps of scanning a light beam across the face of the detector head surface, detecting the light beam, reflecting the beam into corresponding optical bars, detecting light beam breakage at the ideal height of the detector head and sensing the depth of the breakage at a number of depths.
In one embodiment, the depth preferred by a patient can be preselected so that the detector head automatically stops at the height without lowering closer to the patient.
This is useful in cases where the patient simply does not want the detector head in too close a proximity to their profile.
In one embodiment of the invention, the height detection apparatus comprises external parts to the camera that are mounted to the side of the camera.
Advantageously, the invention provides: a detector head that allows for precise height determination without the use of complicated apparatus, an apparatus that does not contain multiple connections of light emitters and detectors; an apparatus that does not have to be removed with each change of collimator plates; a detector head for scanning a patients' profile accurately; and a detector head that does not have to rise and lower in succession to locate the ideal height of the detector head with respect to a patient.
According to the invention, there is provided a method of adjusting the path of a scintillation camera, the scintillation camera including a detector head and a detector head surface, the method comprising the steps of: moving the detector head with respect to a patient; projecting a beam of light across the detector head surface from a single light source; sensing the beam of light at multiple depths; reflecting the beam of light into at least one optical bar; detecting when the beam of light is broken; and stopping movement of the detector head when beam breakage is detected.
According to the invention, there is provided a method of adjusting the path of a scintillation camera, the scintillation camera including a detector head, the detector g head having a position relative to a patient, the method comprising the steps of moving the detector head position with respect to the patient; projecting a beam of light across the detector head from a single light source; sensing the beam of light at a multiple of depths; reflecting the beam of light into at least one optical bar; detecting when the beam of light is broken; stopping movement of the detector head when beam breakage is detected at a first depth; and when beam breakage is no longer detected at the first depth, adjusting the detector head position until beam breakage is detected at a second depth.
According to the invention, there is provided an apparatus for adjusting the path of a scintillation camera, the camera comprising a detector head and a detector head surface, the apparatus comprising: a light source for projecting a beam of light across the detector head surface; a light detector for sensing the beam of light; at least one optical;
a mirror for reflecting the beam of light into the at least one optical bar;
means to detect when the beam of light is broken; and means to stop movement of the detector head when beam breakage is detected.
According to an aspect of the invention, the apparatus for adjusting the path of a scintillation camera is mounted to the side of the detector head.
According to an aspect of the invention, there is provided a method of adjusting the height of a scintillation camera automatically, the scintillation camera including a detector head, the method comprising the steps of: presetting at least one height condition for the detector head relative to a patient; moving the detector head with respect to the patient; and stopping movement of the detector head when the detector head reaches preset height condition.
Other advantages, objects and features of the present invention will be readily apparent to those skilled in the art from a review of the following detailed description of preferred embodiments in conjunction with the accompanying drawings and claims.
Brief Description of the Drawings The embodiments of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a scintillation camera including a detached patient support in accordance with the invention;
Figure 2 is a perspective view of the guide of a scintillation camera;
Figure 3 is a front elevation view of a scintillation camera;
Figure 4 is a side elevation view of a scintillation camera;
Figure 5 is a side elevation view of a scintillation camera;
Figure 6 is a front elevation view of a scintillation camera;
Figure 7 is a top plan view of a scintillation camera;
Figure 8 is a perspective view of the scintillation camera of Figure 1, including the detached patient support and engaged patient support, with the stretcher removed;
Figure 9 is a side view of a portion of the patient support apparatus;
Figure 10 is a perspective view of the positioner;
Figure 11 is a side elevation view of the positioner;
Figure 12 is a front elevation view of the positioner;
Figure 13a is a plan view of an embodiment of the present invention;
Figure 13b is a perspective view of the embodiment of Figure 13a;
5 Figure 13c illustrates an alternative embodiment;
Figure 14 illustrates the defining axes in which the present invention operates in;
and Figure 15 illustrates the computer processing means of the present invention.
Similar references are used in different figures to denote similar components.
Detailed Description The preferred embodiment of the present invention includes an apparatus and method for determining the ideal height of a scintillation camera with respect to a patient for producing optimal views. The present invention is described below in conjunction with a preferred environment. However, it should be understood that the invention could be used in any medical camera environment requiring height determination.
The following description does not delve into matters common in the art. In particular, it shall be understood that the computer processing means for processing the collected height determination data and the controlling means for controlling the adjustment of the camera are common in the art, and the configuration of which is irrelevant to the present invention.
Referring to Figures 1 to 12, a nuclear camera 5 is supported and positioned relative to a patient by a support structure 10. Nuclear cameras are heavy, usually weighing approximately three to four thousand pounds. Thus, the support structure 10 should be strong and stable in order to be able to position the camera 5 safely and accurately. The support structure 10 includes a base 15, an annular support 20, an elongate support 25, and a guide 30.
The base 15 includes a frame 35. The frame 35 includes twelve lengths of square steel tubing welded together in the shape of a rectangular parallelepiped. The frame 35 has a front square section 37 and a rear square section 38. In the illustrated embodiment, the frame 35 is approximately five feet wide, five feet high, and two feet deep. The frame 35 also includes eight triangular corner braces 40 welded to the front square section 37, that is, each corner of the front square section 37 has two corner braces 40, one towards the front of the front square section 37, and one towards the rear of the front square section 37. In the illustrated embodiment, the corner braces 40 are in the shape of equilateral right angle triangles.
Attached to the underside of the frame 35 are two horizontal legs 45. Attached to each leg 45 are two feet 50. An alternative to the use of feet 50 is to attach the base 15 to a floor by way of bolts set into the floor. The legs 45 extend beyond the frame 35 so as to position the feet 50 wider apart to increase the stability of the base 15. The feet 50 are adjustable so that the base 15 may be levelled. Thus constructed, the base 15 is strong, stable, rigid, and capable of supporting heavy loads.
The annular support 20 is vertically oriented, having an inner surface 55 defining an orifice 60, an outer surface 65, a front surface 70, and a rear surface 75.
The annular support 20 is constructed of a ductile iron casting capable of supporting heavy loads. In the illustrated embodiment, the annular support 20 has an outside diameter of about fifty two inches. The annular support 20 is supported by upper rollers 80 and lower rollers 85 which are mounted on the base 15. The upper rollers 80 and lower rollers 85 roll on the outer surface 65, thus enabling the annular support 20 to rotate relative to the base 15 in the plane defined by the annular support 20. Each of the upper rollers 80 and lower rollers 85 are mounted onto a pair of corner braces 40 by way of axles with deep groove bearings. The bearings should be low friction and be able to withstand heavy loads. The axles of the upper rollers 80 are radially adjustable relative to the annular support 20, so that the normal force exerted by the upper rollers 80 on the outer surface 60 is adjustable.
The curved surfaces of the upper rollers 80 and lower rollers 85 (i.e. the surfaces that contact the outer surface 60) should be tough so as to be able to withstand the pressures exerted by the annular support 20, and should have a fairly high coefficient of friction so as to roll consistently relative to the annular support 20.
Attached to each pair of corner braces 40 is a stabilizing arm (not shown) oriented perpendicularly to the plane of the annular support 20. A pair of small stabilizing rollers (not shown) are mounted onto each stabilizing arm. Each pair of stabilizing rollers is positioned such that one stabilizing roller rolls on the front surface 70, and the other stabilizing roller rolls on the rear surface 75. The stabilizing rollers maintain the annular support 20 in the vertical plane.
The elongate support 25 includes a pair of support arms 100, each of which extends through an aperture in the annular support 20. The nuclear camera 5 is rotatably attached to one end of the pair of support arms 100, such that the nuclear camera 5 faces the front surface 70. A counter weight 105 is attached to the other end of the pair of support arms 100, such that the counterweight 105 faces the rear surface 75.
The counter weight 105 includes a pair of parallel counter weight members 110, each of which is pivotally attached to one of the support arms 100. A first weight 115 is attached to one end of the pair of counter weight members 110, and a second weight 120 is attached to the other end of the pair of counter weight members 110. A
pair of counter weight links 121 connect the counter weight members 110 to the annular support 20. Each counter weight link 121 is pivotally attached at one end to its corresponding counter weight member 110. Each counter weight link 121 is pivotally attached at its other end to a counter weight bracket 122 which is rigidly attached to the annular support 20. The counter weight links 121 are attached to the counterweight members 110 and counter weight brackets 122 using bolts and tapered roller bearings. Each counter weight link 121 is pivotable relative to the annular support 20 in a plane perpendicular to and fixed relative to the annular support 20.
The guide 30 attaches the elongate support 25 to the annular support 20, and controls the position of the elongate support 25, and hence the scintillation camera 5, relative to the annular support 20. A pair of brackets 125 is rigidly attached to the annular support 20. A pair of rigid links 130 is pivotally attached at support arm pivot points 135 to the support arms 100. The pair of links 130 is also pivotally attached at bracket pivot points 140 to the brackets 125. At the support arm pivot points 135 and bracket pivot points 140 are tapered roller bearings mounted with bolts. Each link 130 is pivotable relative to the annular support 20 in a plane perpendicular to and fixed relative to the annular support 20. Thus, as the annular support 20 rotates relative to the base 15, the respective planes in which each link 130 and each support arm 100 can move remain fixed relative to the annular support 20.
A pair of linear tracks 145 are rigidly attached to the front surface 70 of the annular support 20. The tracks 145 are oriented such that they are parallel to the respective planes in which each link 130 and each support arm 100 can move. A
pair of rigid sliding arms 1 SO (not shown in Figure 1 ) include camera ends 155 and straight ends 160. Each camera end 155 is pivotally attached to one of the support arms 100 at the point of attachment of the scintillation camera 5. Each straight end 160 includes a pair of spaced apart cam followers or guides 165 slidable within the corresponding track 145.
Thus, movement of the scintillation camera 5 relative to the annular support 20 (i.e. we are not concerned, at this point, with rotational movement of the scintillation camera 5 relative to the elongate support 25) is linear and parallel to the plane of the annular support 20. Note that if the camera ends 155 were pivotally attached to the support arms 100 between the nuclear camera 5 and the annular support 20, the movement of the nuclear camera 5 relative to the annular support 20 would not be linear.
Movement of the scintillation camera 5 relative to the annular support 20 is effected by an actuator 170. The actuator 170 includes a fixed end 175 pivotally attached to the annular support 20, and a movable end 180 pivotally attached to the elongate support 25. The actuator 170 is extendable and retractable, and is thus able to move the elongate support 25 relative to the annular support 20.
Movement of the annular support 20 relative to the base 15 is effected by a drive unit 185. The drive unit 185 includes a quarter horsepower permanent magnet DC
motor and a gearbox to reduce the speed of the output shaft of the drive unit 185.
Alternatively, other types of motors could be used, such as hydraulic or pneumatic motors.
The output shaft of the drive unit 185 is coupled, by means of a toothed timing belt 195 and two pulley wheels 200, to the axle of a drive roller 190, which is simply one of the lower rollers 85, thus driving the drive roller 190. Power is then transferred from the drive roller 190 to the annular support 20 by friction between the drive roller 190 and the outer surface 65 of the annular support 20.
The support structure 10 of the illustrated embodiment is designed to operate with an apparatus for supporting and positioning a patient, such apparatus including a detached patient support 205, an engaged patient support 210, and a cylinder 21 S.
The detached patient support 205 includes rigid patient frame 215 supported by four casters 220. Mounted near the top of the patient frame 215 are first support wheels 225 for supporting a stretcher 227 upon which a patient is lying. Two parallel, spaced apart side rails 230 are rigidly attached to the patient frame 215. The first support wheels 225 and the side rails 230 are arranged to enable the stretcher 227 to roll lengthwise on the detached patient support 205. Thus, if the patient support 205 faces the front surface 70 such that the patient support is central and perpendicular relative to the annular support 20, the stretcher 227 is movable on the first patient support wheels substantially along the axis of the annular support 20. A gear box and motor unit 237 driving at least one of the first patient support wheels 225 moves the stretcher 227 as described. A 0.125 horsepower permanent magnet DC motor has been found to be adequate.
The detached patient support 205 can be used both for transporting a patient to and from the scintillation camera 5 and support structure 10 therefor, and for supporting and positioning a patient relative to the base 15 during operation of the scintillation camera 5 and support structure 10. To ensure that the detached patient support 1$
remains stationary during operation of the scintillation camera $, four stabilizers 233 can be lowered. Thus lowered, the stabilizers 233 ensure that the detached patient support remains stationary relative to the floor.
$ The engaged patient support 210 includes second support wheels 23$. The second support wheels 23 $ are positioned such that the stretcher 227 rolled along the first support wheels 22$ can roll onto the second support wheels 23$ until the stretcher 227 is either fully or partially supported by the second support wheels 23$. The engaged patient support 210 also includes four transverse wheels 240.
The cylinder 21$ is rigidly mounted to the annular support 20. The cylinder 21$
is aligned with the orifice 60 of the annular support 20 such that the cylinder is coaxial with the annular support 20. The cylinder 21$ includes a smooth inner surface 24$ upon which rest the transverse wheels 240 of the engaged patient support 210. Thus, the 1$ arrangement is such that the patient remains stationary substantially along the axis of the annular support 20 as the annular support 20 rotates relative to the base 1$, regardless of whether the board or stretcher is supported by the first support wheels 22$, the second support wheels 23 $, or both.
The engaged patient support 210 also includes a stabilizer 24$. The stabilizer 24$
includes outside wheels 2$0 to maintain the engaged patient support 210 horizontal, that is, to stop the engaged patient support from tipping relative to the cylinder 21$. The outside wheels 2$ 0 roll on the outside surface 243 of the cylinder 21$. The stabilizer 24$
also includes end wheels 2$$ to prevent the engaged patient support 210 from moving 2$ in a direction parallel to the axis ofthe cylinder 21$. The end wheels 2$$
roll on the ends 244 of the cylinder 21$.
A detector head 30$ of the nuclear camera $ is supported between the two support arms 100 by a positioner 320. The detector head 30$ includes a casing 310 in which is contained a scintillation crystal and photomultiplier tubes. Attached to the underside of the casing 310 is a collimator plate 31$. The collimator plate 31$ is made of lead perforated by narrow channels, and includes a collimator support 325 extending from the two edges of the collimator plate adj acent the support arms 310. The collimator plate 315 is attached to the casing 310 by way of bolts 311. By removing the bolts 311, the collimator plate 315 can be removed from the casing 310 and replaced by another S collimator plate 315. A particular design and weight of collimator is selected depending on the isotope being used or the type of study being conducted. Thus, the collimator plate 315 must be changed from time to time. Since the collimator plates 315 vary considerably in weight from one to another, the location centre of gravity of the detector head 305 is dependent upon the weight of the collimator plate 315 attached to the casing 310. Since the angle of the detector head 305 relative to the patient must be adjusted by an operator of the nuclear camera 5, the detector head 305 must be rotatable relative to the arms 100. If the centre of gravity of the detector head 305 is positioned approximately on the axis of rotation of the detector head relative to the support arms 100, then the detector head 305 will be balanced, and the angle of the detector head 305 relative to the support arms 100 will be adjustable by hand. However, changing the collimator plates moves the centre of gravity of the detector head. Since collimator plates 315 are so heavy, it becomes inconvenient or impossible to adjust the angle of the detector head 305 by hand. The positioner 320 enables the operator to adjust the position of the centre of gravity of the detector head 305 to be approximately aligned with the point of rotation of the detector head 305, which passes through the support arms 100.
The positioner 320 attaches the detector head 305 to the support arms 100 and includes a pair of rigid elongate detector head links 330 for aligning the centre of gravity of the detector head 305 relative to the support arms 100. Each detector head link 330 is rotatable relative to the support arms 100 in a plane substantially parallel to its adj acent support arm 100. Each detector head link 330 includes an arm end 335 rotatably attached to the adjacent support arm 100 by way of an arm axle 340. Each detector head link 330 also includes a head end 345 rotatably attached to the detector head 305 by way of a head axle 350.
The positioner 320 also includes a pair of locks 355 for selectively preventing rotation of the detector head 305 relative to the detector head links 330.
Each lock 355 includes the collimator support 325 extending from the detector head 305 from the collimator plate 315. Each lock 355 also includes a block 360 for supporting the detector head link 330 on the collimator support 325. Each block 360 includes a pair of pins 365 located either side of the head axle 350.
As previously discussed, the detector head should be positioned at an ideal height relative to the patient for producing a clear view while maintaining patient comfort. The detector head includes a height detection apparatus for determining this height.
Application of the apparatus allows for practical and efficient height determination.
For the purposes of discussion, it will be assumed that three axes exist in the operating environment. Refernng to Figure 14, the X and Y axes lie in the plane of the detector head surface 570, while axis Z runs through the surface. The Z axis is the axis along which the detector head moves along during height determination. It is possible for the detector head to move and rotate along all three axes, resulting in the Z plane to be angled with respect to the patient. This is necessary in order to obtain the different views previously explained. For the time being however, it will be assumed, for simplification, that the detector head is not rotating along any axis.
Referring to Figures 13a and 13b, the height detection apparatus will now be described. Light source 500 is mounted to camera 5. The light source is preferably an accurate point source of light adjustable in beam width. The light source is ideally a laser, but could consist of any light emitting device.
Mounted to camera 5 diagonally from the light source is a charged coupled device or CCD 510. The CCD is preferably a unidirectional, light sensitive CCD. A
unidirectional CCD is preferable because it can detect beam breakage along multiple depths as the detector head lowers toward the patient (ie: the light beam is detected in multiple planes parallel to the Z plane). The CCD can include any number of detection elements, but preferably includes at least 256 elements for optimal detection.
The number of optical bars used in the apparatus is dependent upon the number of CCD
elements. In a preferred embodiment, there is one set of perpendicular optical bars, 530 and 540, for each CCD element (1:1 ratio). However, any number of CCD elements can correspond to a set of optical bars. For example, for every 2 CCD elements, one set of bars could be used (2:1 ratio) as seen in Figure 13c. The optical bars are preferably plexiglass.
Positioned to CCD 510 is mirror 550 angled such as to reflect light into the optical bars 530 and 540.
The mounting means for the apparatus is any conventional means, such as mounting plates and pins or the apparatus can be screwed to the camera. In one embodiment, the height detection apparatus comprises external parts to the camera, and is mounted to the side of the detection head, thereby eliminating the need to mount it to the collimator plate, as done with prior art. The collimator plates are more easily removed and replaced without having to remove the height detection apparatus.
In one other embodiment, the minor could be fixed to the collimator if it was so desired.
Light source 500 projects light beam 560 along detector head surface 570. The light source is capable of sweeping a light beam along the surface of the detector head surface, while the CCD collects the beam energy. In a preferred embodiment the light source oscillates back and forth to sweep the light beam along the surface.
Alternatively, the light source could rotate 360 degrees around to produce a similar effect across the surface. In this case, an absorber could be mounted to the back of the light source to prevent the light beam from projecting into the room.
However, in either configuration, a motor (not shown) can be used to power the light source movement. The motor, preferably, is mounted to the detector head, and not the collimator plate.
As projected light beam 560 sweeps across the detector head surface 570, it is detected by CCD element 520 at a number of depths. The element that detects the light corresponds with a set of optical bars 530 and 540 as described above. When CCD
element 520 detects light beam 560, mirror 550 reflects to the light beam 90 degrees into the corresponding light bars.
During this, the camera may lower towards the patient along the Z axis. As the camera lowers, the beam will eventually be broken by patient interference along a particular depth of the CCD. At this point, the camera is automatically controlled not to lower any further. Since the CCD detects breakage at a number of depths, there is no need for the detection head to lower and rise in order to locate the ideal height.
For different body scans, the camera may move along the X and/or the Y axis along the profile of the patient. For whole body scans, usually rotation of the detector head is not required during the scanning. Since it is desired to maintain the camera at a minimum distance from the patient at all times, it is beneficial to provide means to allow the camera to constantly and automatically adjust its height as it moves over the patient's profile. When a whole body view is desired, the camera will automatically adjust to the ideal height as it moves along the profile of the patient. For example, as the camera scans along the feet of the patient, the camera would be higher and as it scans along the legs of the patient, the camera automatically adjusts to a lower position. The detector head to patient distance remains fixed during the entire scan. And since the camera is in an ideal position over the entire profile, a better view is produced.
2 S As the camera 5 travels over the patient's profile, light beam breakage is detected in real time. Therefore, continuing with the above example, as the camera travels over the feet at a higher height relative to the ground, beam breakage is detected at that level.
As the camera moves over the legs, a lower portion of the patient's profile relative to the feet, beam breakage is no longer detected. In real time, the camera will adjust (lower) until beam breakage is again detected. While the height of the detector head relative to the ground changes, its height with respect to the patient may remain constant. This is accomplished by virtue of the unidirectional CCD which detects light in a number of depths. When beam breakage is no longer detected at a first height, the camera lowers until beam breakage is detected at a second height.
5 In some instances, the detector head may rotate to scan different views of the patient's body. The present invention still allows for height detection with respect to the patient. Assuming that the Z plane still lies along the detector head surface, the projected light beam on the surface may change from a sweep to an area of fixed size;
the smallest size being when the detector head is at 90 degrees to the light beam. The CCD
is still 10 capable of detecting the light and reflecting the beam into the optical blocks. The same mechanisms are at work in these situations for detecting where the beam is broken by patient interference.
When the camera is taking a view at a single spot, the detector head lowers until 15 beam breakage is detected. The camera will then stop lowering towards the patient and take the required view. The detector head is able to located the ideal height without any trial and error movements.
Some patients are uncomfortable in having the detector head close to their profile.
20 With the present invention, the depth preferred by the patient can be preset so that the detector head stops at the preferred height without getting too close to the patient (ie:
without waiting for beam breakage to be detected). For example, if it is known that the patient is most comfortable when the detector head is at a preferred height corresponding to element 240 (out of 256 elements of the CCD), but breakage will not occur until element 250, then this preferred height can be preset. In this way, the apparatus does not have to lower only until beam breakage is detected. The detection system can be overridden by a preset condition. The preset condition will allow the detector head to stop lowering towards the patient at any level.
When a preset condition is used, the camera will adjust as if beam breakage is detected at the preset condition. So, in the above example, if beam breakage will be detected at element 250, but the preferred height is at element 240, then the camera will stop movement at the position where beam breakage would be detected at element 240.
This preset override can also be used in total body views. For example, if the detector head travels along the X axis for the profile view, and the Z axis for height relative to the patient, a number of preset conditions can be entered such that the detector head automatically adjusts its height along the Z axis at particular locations along the X
axis. This again, prevents the camera from lowering as close as possible to the patient (the point of beam breakage). These scenarios are useful in cases where the patient is extremely uncomfortable in having the detector head too close.
Referring to Figure 15, the present invention also includes a computer processing means 600, with processor 610 for processing the data received by the height detection apparatus and for controlling the automatic adjustment of the camera. The height detection information is processed in real time and fed to a motion control unit 620 which is capable of adjusting the position of the camera, thereby minimizing the distance between the camera and the patient. The scintillation camera 5 also includes an interface 630 with on screen menus and function input means for selecting a variety of scintillation camera functions, including preset conditions for controlling the height of the detector head. The operator 640 may enter the preset conditions at interface 630, which is fed to motion control unit 620 which is capable of adjusting the camera to the preferred height or heights set.
While the invention has been described according to what is presently considered to be the most practical and preferred embodiments, it must be understood that the invention is not limited to the disclosed embodiments. Those ordinarily skilled in the art will understand that various modifications and equivalent structures and functions may be made without departing from the spirit and scope of the invention as defined in the claims. Therefore, the invention as defined in the claims must be accorded the broadest possible interpretation so as to encompass all such modifications and equivalent structures and functions.
The pair of arms generally extends through a corresponding pair of apertures in the rotating support. One end of the pair of arms supports the detector head on one side of the annular support. The other end of the pair of arms supports a counter balance weight.
Thus, the elongate support is counterbalanced with a counterweight on the opposite side of the detector head.
I 0 With such a design of support structure for a scintillation camera, a patient must lie on a horizontally oriented patient support. The patient support must be cantilevered so that the detector head can pass underneath the patient. If the detector head must pass underneath only one end of the patient, such as the patient's head, the cantilevered portion of the patient support is not long enough to cause serious difficulties in the design of the cantilevered patient support. However, if the camera must be able to pass under the entire length of the patient, the entire patient must be supported by the cantilevered portion of the patient support. As the cantilevered portion of the patient support must be thin so as not to interfere with the generation of images by the scintillation camera, serious design difficulties are encountered.
Among the advantages associated with such as design of support structure is that a patient may be partially pass through the orifice defined by the annular support so that the pair of arms need not be as long. However, the patient support must be able to support the patient in this position relative to the annular support, must be accurately positionable relative to the annular support, and must not interfere either with the rotation of the annular support or with the cables which will inevitably extend from the detector head to a nearby computer or other user control.
The detector head must also be positioned at a certain height relative to the patient. It is commonly known in the art that when the collimator to patient distance is minimized, the better the image resolution develops. However, many patients do not feel comfortable with the detector head too close to them. An ideal position must be found to ensure a good quality view is taken and to provide patient comfort.
A common method to find this position is to mount light emitters and detectors 5 to the camera. The camera is lowered toward the patient, and when a light beam produced by the emitter is broken by patient interference, the detector head is in good proximity to the patient, but still is not in the ideal position. It is common in the art for the detector to have to lower and rise relative to the patient in order to pinpoint the exact ideal height location. This 'trial and error' method is inefficient as well as hazardous.
Another problem in state of the art systems is that the light emitter and detector pairs are mounted to the collimator plate. It is known in the art that different collimator plates must be used to produce different views in varying circumstances.
Therefore, every time, the collimator plate must be changed, the light emitter and detector apparatus must be removed from the plate and mounted and reconnected to the new plate.
This is very inefficient and time consuming.
Also, commonly, the apparatus includes a plurality of light emitters and detectors mounted along the detector head to produce an array of light beams across the detector head surface. It then becomes necessary to disconnect and reconnect the plurality of emitters and detectors each time the collimator plate is changed. This design is also costly and complex to manufacture. In addition, because the apparatus is mounted to the outermost portion of the collimator plate, this design increases the collimator to patient distance.
Other system designs do not scan a patient's profile accurately since the detector head detects only one height relative to the patient. These binary systems do not allow the detector head to adjust in height according to the position of the detector head along the patient's profile. For example, the detector head tends to rise as it travels over the profile of a patient when it encounters the feet. The detector head then stays at the elevated height for the remainder of the profile scan. Since the collimator to patient distance is increased for the remainder of the scan, a view of less quality is produced.
It is therefore necessary to provide a detector head adapted for precise height determination without the use of a complicated apparatus. It would be useful if the apparatus did not contain multiple connections for light emitters and detectors. It would also be beneficial if the apparatus did not have to be removed with each change of collimator plates. It would also be an asset if the detector head did not have to rise and lower in succession in order to locate the ideal height. Finally it would be beneficial if the detector head could scan a patients' profile accurately.
Summary An object of the invention is to provide an improved method and apparatus for automatically adjusting the path of a scintillation camera.
A second object of the invention is to provide a method and apparatus that effectively meets the needs mentioned in the above statements. The invention relates to a method and apparatus for determining the ideal height of a detector head with respect to a patient's profile. The apparatus includes a laser light source for projecting a light beam across the detector head surface; a CCD for detecting the light beam, the CCD
preferably being unidirectional so that it can read the depth of beam breakage at a multiple of depths; a multiple of optical bars extending perpendicularly from the CCD;
and a mirror for reflecting the light beam as detected by the CCD element into the corresponding optical blocks for the element. In a preferred embodiment, the apparatus comprises external parts to the detector head. That apparatus is mounted across opposite sides of the detector head and not to the collimator plate. The mounting means is anything common in the art.
The light source may oscillate back and forth, or may rotate a full 360 degrees.
The CCD element to optical bar ratio may be 1:1 or any other suitable ratio.
The method includes the steps of scanning a light beam across the face of the detector head surface, detecting the light beam, reflecting the beam into corresponding optical bars, detecting light beam breakage at the ideal height of the detector head and sensing the depth of the breakage at a number of depths.
In one embodiment, the depth preferred by a patient can be preselected so that the detector head automatically stops at the height without lowering closer to the patient.
This is useful in cases where the patient simply does not want the detector head in too close a proximity to their profile.
In one embodiment of the invention, the height detection apparatus comprises external parts to the camera that are mounted to the side of the camera.
Advantageously, the invention provides: a detector head that allows for precise height determination without the use of complicated apparatus, an apparatus that does not contain multiple connections of light emitters and detectors; an apparatus that does not have to be removed with each change of collimator plates; a detector head for scanning a patients' profile accurately; and a detector head that does not have to rise and lower in succession to locate the ideal height of the detector head with respect to a patient.
According to the invention, there is provided a method of adjusting the path of a scintillation camera, the scintillation camera including a detector head and a detector head surface, the method comprising the steps of: moving the detector head with respect to a patient; projecting a beam of light across the detector head surface from a single light source; sensing the beam of light at multiple depths; reflecting the beam of light into at least one optical bar; detecting when the beam of light is broken; and stopping movement of the detector head when beam breakage is detected.
According to the invention, there is provided a method of adjusting the path of a scintillation camera, the scintillation camera including a detector head, the detector g head having a position relative to a patient, the method comprising the steps of moving the detector head position with respect to the patient; projecting a beam of light across the detector head from a single light source; sensing the beam of light at a multiple of depths; reflecting the beam of light into at least one optical bar; detecting when the beam of light is broken; stopping movement of the detector head when beam breakage is detected at a first depth; and when beam breakage is no longer detected at the first depth, adjusting the detector head position until beam breakage is detected at a second depth.
According to the invention, there is provided an apparatus for adjusting the path of a scintillation camera, the camera comprising a detector head and a detector head surface, the apparatus comprising: a light source for projecting a beam of light across the detector head surface; a light detector for sensing the beam of light; at least one optical;
a mirror for reflecting the beam of light into the at least one optical bar;
means to detect when the beam of light is broken; and means to stop movement of the detector head when beam breakage is detected.
According to an aspect of the invention, the apparatus for adjusting the path of a scintillation camera is mounted to the side of the detector head.
According to an aspect of the invention, there is provided a method of adjusting the height of a scintillation camera automatically, the scintillation camera including a detector head, the method comprising the steps of: presetting at least one height condition for the detector head relative to a patient; moving the detector head with respect to the patient; and stopping movement of the detector head when the detector head reaches preset height condition.
Other advantages, objects and features of the present invention will be readily apparent to those skilled in the art from a review of the following detailed description of preferred embodiments in conjunction with the accompanying drawings and claims.
Brief Description of the Drawings The embodiments of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a scintillation camera including a detached patient support in accordance with the invention;
Figure 2 is a perspective view of the guide of a scintillation camera;
Figure 3 is a front elevation view of a scintillation camera;
Figure 4 is a side elevation view of a scintillation camera;
Figure 5 is a side elevation view of a scintillation camera;
Figure 6 is a front elevation view of a scintillation camera;
Figure 7 is a top plan view of a scintillation camera;
Figure 8 is a perspective view of the scintillation camera of Figure 1, including the detached patient support and engaged patient support, with the stretcher removed;
Figure 9 is a side view of a portion of the patient support apparatus;
Figure 10 is a perspective view of the positioner;
Figure 11 is a side elevation view of the positioner;
Figure 12 is a front elevation view of the positioner;
Figure 13a is a plan view of an embodiment of the present invention;
Figure 13b is a perspective view of the embodiment of Figure 13a;
5 Figure 13c illustrates an alternative embodiment;
Figure 14 illustrates the defining axes in which the present invention operates in;
and Figure 15 illustrates the computer processing means of the present invention.
Similar references are used in different figures to denote similar components.
Detailed Description The preferred embodiment of the present invention includes an apparatus and method for determining the ideal height of a scintillation camera with respect to a patient for producing optimal views. The present invention is described below in conjunction with a preferred environment. However, it should be understood that the invention could be used in any medical camera environment requiring height determination.
The following description does not delve into matters common in the art. In particular, it shall be understood that the computer processing means for processing the collected height determination data and the controlling means for controlling the adjustment of the camera are common in the art, and the configuration of which is irrelevant to the present invention.
Referring to Figures 1 to 12, a nuclear camera 5 is supported and positioned relative to a patient by a support structure 10. Nuclear cameras are heavy, usually weighing approximately three to four thousand pounds. Thus, the support structure 10 should be strong and stable in order to be able to position the camera 5 safely and accurately. The support structure 10 includes a base 15, an annular support 20, an elongate support 25, and a guide 30.
The base 15 includes a frame 35. The frame 35 includes twelve lengths of square steel tubing welded together in the shape of a rectangular parallelepiped. The frame 35 has a front square section 37 and a rear square section 38. In the illustrated embodiment, the frame 35 is approximately five feet wide, five feet high, and two feet deep. The frame 35 also includes eight triangular corner braces 40 welded to the front square section 37, that is, each corner of the front square section 37 has two corner braces 40, one towards the front of the front square section 37, and one towards the rear of the front square section 37. In the illustrated embodiment, the corner braces 40 are in the shape of equilateral right angle triangles.
Attached to the underside of the frame 35 are two horizontal legs 45. Attached to each leg 45 are two feet 50. An alternative to the use of feet 50 is to attach the base 15 to a floor by way of bolts set into the floor. The legs 45 extend beyond the frame 35 so as to position the feet 50 wider apart to increase the stability of the base 15. The feet 50 are adjustable so that the base 15 may be levelled. Thus constructed, the base 15 is strong, stable, rigid, and capable of supporting heavy loads.
The annular support 20 is vertically oriented, having an inner surface 55 defining an orifice 60, an outer surface 65, a front surface 70, and a rear surface 75.
The annular support 20 is constructed of a ductile iron casting capable of supporting heavy loads. In the illustrated embodiment, the annular support 20 has an outside diameter of about fifty two inches. The annular support 20 is supported by upper rollers 80 and lower rollers 85 which are mounted on the base 15. The upper rollers 80 and lower rollers 85 roll on the outer surface 65, thus enabling the annular support 20 to rotate relative to the base 15 in the plane defined by the annular support 20. Each of the upper rollers 80 and lower rollers 85 are mounted onto a pair of corner braces 40 by way of axles with deep groove bearings. The bearings should be low friction and be able to withstand heavy loads. The axles of the upper rollers 80 are radially adjustable relative to the annular support 20, so that the normal force exerted by the upper rollers 80 on the outer surface 60 is adjustable.
The curved surfaces of the upper rollers 80 and lower rollers 85 (i.e. the surfaces that contact the outer surface 60) should be tough so as to be able to withstand the pressures exerted by the annular support 20, and should have a fairly high coefficient of friction so as to roll consistently relative to the annular support 20.
Attached to each pair of corner braces 40 is a stabilizing arm (not shown) oriented perpendicularly to the plane of the annular support 20. A pair of small stabilizing rollers (not shown) are mounted onto each stabilizing arm. Each pair of stabilizing rollers is positioned such that one stabilizing roller rolls on the front surface 70, and the other stabilizing roller rolls on the rear surface 75. The stabilizing rollers maintain the annular support 20 in the vertical plane.
The elongate support 25 includes a pair of support arms 100, each of which extends through an aperture in the annular support 20. The nuclear camera 5 is rotatably attached to one end of the pair of support arms 100, such that the nuclear camera 5 faces the front surface 70. A counter weight 105 is attached to the other end of the pair of support arms 100, such that the counterweight 105 faces the rear surface 75.
The counter weight 105 includes a pair of parallel counter weight members 110, each of which is pivotally attached to one of the support arms 100. A first weight 115 is attached to one end of the pair of counter weight members 110, and a second weight 120 is attached to the other end of the pair of counter weight members 110. A
pair of counter weight links 121 connect the counter weight members 110 to the annular support 20. Each counter weight link 121 is pivotally attached at one end to its corresponding counter weight member 110. Each counter weight link 121 is pivotally attached at its other end to a counter weight bracket 122 which is rigidly attached to the annular support 20. The counter weight links 121 are attached to the counterweight members 110 and counter weight brackets 122 using bolts and tapered roller bearings. Each counter weight link 121 is pivotable relative to the annular support 20 in a plane perpendicular to and fixed relative to the annular support 20.
The guide 30 attaches the elongate support 25 to the annular support 20, and controls the position of the elongate support 25, and hence the scintillation camera 5, relative to the annular support 20. A pair of brackets 125 is rigidly attached to the annular support 20. A pair of rigid links 130 is pivotally attached at support arm pivot points 135 to the support arms 100. The pair of links 130 is also pivotally attached at bracket pivot points 140 to the brackets 125. At the support arm pivot points 135 and bracket pivot points 140 are tapered roller bearings mounted with bolts. Each link 130 is pivotable relative to the annular support 20 in a plane perpendicular to and fixed relative to the annular support 20. Thus, as the annular support 20 rotates relative to the base 15, the respective planes in which each link 130 and each support arm 100 can move remain fixed relative to the annular support 20.
A pair of linear tracks 145 are rigidly attached to the front surface 70 of the annular support 20. The tracks 145 are oriented such that they are parallel to the respective planes in which each link 130 and each support arm 100 can move. A
pair of rigid sliding arms 1 SO (not shown in Figure 1 ) include camera ends 155 and straight ends 160. Each camera end 155 is pivotally attached to one of the support arms 100 at the point of attachment of the scintillation camera 5. Each straight end 160 includes a pair of spaced apart cam followers or guides 165 slidable within the corresponding track 145.
Thus, movement of the scintillation camera 5 relative to the annular support 20 (i.e. we are not concerned, at this point, with rotational movement of the scintillation camera 5 relative to the elongate support 25) is linear and parallel to the plane of the annular support 20. Note that if the camera ends 155 were pivotally attached to the support arms 100 between the nuclear camera 5 and the annular support 20, the movement of the nuclear camera 5 relative to the annular support 20 would not be linear.
Movement of the scintillation camera 5 relative to the annular support 20 is effected by an actuator 170. The actuator 170 includes a fixed end 175 pivotally attached to the annular support 20, and a movable end 180 pivotally attached to the elongate support 25. The actuator 170 is extendable and retractable, and is thus able to move the elongate support 25 relative to the annular support 20.
Movement of the annular support 20 relative to the base 15 is effected by a drive unit 185. The drive unit 185 includes a quarter horsepower permanent magnet DC
motor and a gearbox to reduce the speed of the output shaft of the drive unit 185.
Alternatively, other types of motors could be used, such as hydraulic or pneumatic motors.
The output shaft of the drive unit 185 is coupled, by means of a toothed timing belt 195 and two pulley wheels 200, to the axle of a drive roller 190, which is simply one of the lower rollers 85, thus driving the drive roller 190. Power is then transferred from the drive roller 190 to the annular support 20 by friction between the drive roller 190 and the outer surface 65 of the annular support 20.
The support structure 10 of the illustrated embodiment is designed to operate with an apparatus for supporting and positioning a patient, such apparatus including a detached patient support 205, an engaged patient support 210, and a cylinder 21 S.
The detached patient support 205 includes rigid patient frame 215 supported by four casters 220. Mounted near the top of the patient frame 215 are first support wheels 225 for supporting a stretcher 227 upon which a patient is lying. Two parallel, spaced apart side rails 230 are rigidly attached to the patient frame 215. The first support wheels 225 and the side rails 230 are arranged to enable the stretcher 227 to roll lengthwise on the detached patient support 205. Thus, if the patient support 205 faces the front surface 70 such that the patient support is central and perpendicular relative to the annular support 20, the stretcher 227 is movable on the first patient support wheels substantially along the axis of the annular support 20. A gear box and motor unit 237 driving at least one of the first patient support wheels 225 moves the stretcher 227 as described. A 0.125 horsepower permanent magnet DC motor has been found to be adequate.
The detached patient support 205 can be used both for transporting a patient to and from the scintillation camera 5 and support structure 10 therefor, and for supporting and positioning a patient relative to the base 15 during operation of the scintillation camera 5 and support structure 10. To ensure that the detached patient support 1$
remains stationary during operation of the scintillation camera $, four stabilizers 233 can be lowered. Thus lowered, the stabilizers 233 ensure that the detached patient support remains stationary relative to the floor.
$ The engaged patient support 210 includes second support wheels 23$. The second support wheels 23 $ are positioned such that the stretcher 227 rolled along the first support wheels 22$ can roll onto the second support wheels 23$ until the stretcher 227 is either fully or partially supported by the second support wheels 23$. The engaged patient support 210 also includes four transverse wheels 240.
The cylinder 21$ is rigidly mounted to the annular support 20. The cylinder 21$
is aligned with the orifice 60 of the annular support 20 such that the cylinder is coaxial with the annular support 20. The cylinder 21$ includes a smooth inner surface 24$ upon which rest the transverse wheels 240 of the engaged patient support 210. Thus, the 1$ arrangement is such that the patient remains stationary substantially along the axis of the annular support 20 as the annular support 20 rotates relative to the base 1$, regardless of whether the board or stretcher is supported by the first support wheels 22$, the second support wheels 23 $, or both.
The engaged patient support 210 also includes a stabilizer 24$. The stabilizer 24$
includes outside wheels 2$0 to maintain the engaged patient support 210 horizontal, that is, to stop the engaged patient support from tipping relative to the cylinder 21$. The outside wheels 2$ 0 roll on the outside surface 243 of the cylinder 21$. The stabilizer 24$
also includes end wheels 2$$ to prevent the engaged patient support 210 from moving 2$ in a direction parallel to the axis ofthe cylinder 21$. The end wheels 2$$
roll on the ends 244 of the cylinder 21$.
A detector head 30$ of the nuclear camera $ is supported between the two support arms 100 by a positioner 320. The detector head 30$ includes a casing 310 in which is contained a scintillation crystal and photomultiplier tubes. Attached to the underside of the casing 310 is a collimator plate 31$. The collimator plate 31$ is made of lead perforated by narrow channels, and includes a collimator support 325 extending from the two edges of the collimator plate adj acent the support arms 310. The collimator plate 315 is attached to the casing 310 by way of bolts 311. By removing the bolts 311, the collimator plate 315 can be removed from the casing 310 and replaced by another S collimator plate 315. A particular design and weight of collimator is selected depending on the isotope being used or the type of study being conducted. Thus, the collimator plate 315 must be changed from time to time. Since the collimator plates 315 vary considerably in weight from one to another, the location centre of gravity of the detector head 305 is dependent upon the weight of the collimator plate 315 attached to the casing 310. Since the angle of the detector head 305 relative to the patient must be adjusted by an operator of the nuclear camera 5, the detector head 305 must be rotatable relative to the arms 100. If the centre of gravity of the detector head 305 is positioned approximately on the axis of rotation of the detector head relative to the support arms 100, then the detector head 305 will be balanced, and the angle of the detector head 305 relative to the support arms 100 will be adjustable by hand. However, changing the collimator plates moves the centre of gravity of the detector head. Since collimator plates 315 are so heavy, it becomes inconvenient or impossible to adjust the angle of the detector head 305 by hand. The positioner 320 enables the operator to adjust the position of the centre of gravity of the detector head 305 to be approximately aligned with the point of rotation of the detector head 305, which passes through the support arms 100.
The positioner 320 attaches the detector head 305 to the support arms 100 and includes a pair of rigid elongate detector head links 330 for aligning the centre of gravity of the detector head 305 relative to the support arms 100. Each detector head link 330 is rotatable relative to the support arms 100 in a plane substantially parallel to its adj acent support arm 100. Each detector head link 330 includes an arm end 335 rotatably attached to the adjacent support arm 100 by way of an arm axle 340. Each detector head link 330 also includes a head end 345 rotatably attached to the detector head 305 by way of a head axle 350.
The positioner 320 also includes a pair of locks 355 for selectively preventing rotation of the detector head 305 relative to the detector head links 330.
Each lock 355 includes the collimator support 325 extending from the detector head 305 from the collimator plate 315. Each lock 355 also includes a block 360 for supporting the detector head link 330 on the collimator support 325. Each block 360 includes a pair of pins 365 located either side of the head axle 350.
As previously discussed, the detector head should be positioned at an ideal height relative to the patient for producing a clear view while maintaining patient comfort. The detector head includes a height detection apparatus for determining this height.
Application of the apparatus allows for practical and efficient height determination.
For the purposes of discussion, it will be assumed that three axes exist in the operating environment. Refernng to Figure 14, the X and Y axes lie in the plane of the detector head surface 570, while axis Z runs through the surface. The Z axis is the axis along which the detector head moves along during height determination. It is possible for the detector head to move and rotate along all three axes, resulting in the Z plane to be angled with respect to the patient. This is necessary in order to obtain the different views previously explained. For the time being however, it will be assumed, for simplification, that the detector head is not rotating along any axis.
Referring to Figures 13a and 13b, the height detection apparatus will now be described. Light source 500 is mounted to camera 5. The light source is preferably an accurate point source of light adjustable in beam width. The light source is ideally a laser, but could consist of any light emitting device.
Mounted to camera 5 diagonally from the light source is a charged coupled device or CCD 510. The CCD is preferably a unidirectional, light sensitive CCD. A
unidirectional CCD is preferable because it can detect beam breakage along multiple depths as the detector head lowers toward the patient (ie: the light beam is detected in multiple planes parallel to the Z plane). The CCD can include any number of detection elements, but preferably includes at least 256 elements for optimal detection.
The number of optical bars used in the apparatus is dependent upon the number of CCD
elements. In a preferred embodiment, there is one set of perpendicular optical bars, 530 and 540, for each CCD element (1:1 ratio). However, any number of CCD elements can correspond to a set of optical bars. For example, for every 2 CCD elements, one set of bars could be used (2:1 ratio) as seen in Figure 13c. The optical bars are preferably plexiglass.
Positioned to CCD 510 is mirror 550 angled such as to reflect light into the optical bars 530 and 540.
The mounting means for the apparatus is any conventional means, such as mounting plates and pins or the apparatus can be screwed to the camera. In one embodiment, the height detection apparatus comprises external parts to the camera, and is mounted to the side of the detection head, thereby eliminating the need to mount it to the collimator plate, as done with prior art. The collimator plates are more easily removed and replaced without having to remove the height detection apparatus.
In one other embodiment, the minor could be fixed to the collimator if it was so desired.
Light source 500 projects light beam 560 along detector head surface 570. The light source is capable of sweeping a light beam along the surface of the detector head surface, while the CCD collects the beam energy. In a preferred embodiment the light source oscillates back and forth to sweep the light beam along the surface.
Alternatively, the light source could rotate 360 degrees around to produce a similar effect across the surface. In this case, an absorber could be mounted to the back of the light source to prevent the light beam from projecting into the room.
However, in either configuration, a motor (not shown) can be used to power the light source movement. The motor, preferably, is mounted to the detector head, and not the collimator plate.
As projected light beam 560 sweeps across the detector head surface 570, it is detected by CCD element 520 at a number of depths. The element that detects the light corresponds with a set of optical bars 530 and 540 as described above. When CCD
element 520 detects light beam 560, mirror 550 reflects to the light beam 90 degrees into the corresponding light bars.
During this, the camera may lower towards the patient along the Z axis. As the camera lowers, the beam will eventually be broken by patient interference along a particular depth of the CCD. At this point, the camera is automatically controlled not to lower any further. Since the CCD detects breakage at a number of depths, there is no need for the detection head to lower and rise in order to locate the ideal height.
For different body scans, the camera may move along the X and/or the Y axis along the profile of the patient. For whole body scans, usually rotation of the detector head is not required during the scanning. Since it is desired to maintain the camera at a minimum distance from the patient at all times, it is beneficial to provide means to allow the camera to constantly and automatically adjust its height as it moves over the patient's profile. When a whole body view is desired, the camera will automatically adjust to the ideal height as it moves along the profile of the patient. For example, as the camera scans along the feet of the patient, the camera would be higher and as it scans along the legs of the patient, the camera automatically adjusts to a lower position. The detector head to patient distance remains fixed during the entire scan. And since the camera is in an ideal position over the entire profile, a better view is produced.
2 S As the camera 5 travels over the patient's profile, light beam breakage is detected in real time. Therefore, continuing with the above example, as the camera travels over the feet at a higher height relative to the ground, beam breakage is detected at that level.
As the camera moves over the legs, a lower portion of the patient's profile relative to the feet, beam breakage is no longer detected. In real time, the camera will adjust (lower) until beam breakage is again detected. While the height of the detector head relative to the ground changes, its height with respect to the patient may remain constant. This is accomplished by virtue of the unidirectional CCD which detects light in a number of depths. When beam breakage is no longer detected at a first height, the camera lowers until beam breakage is detected at a second height.
5 In some instances, the detector head may rotate to scan different views of the patient's body. The present invention still allows for height detection with respect to the patient. Assuming that the Z plane still lies along the detector head surface, the projected light beam on the surface may change from a sweep to an area of fixed size;
the smallest size being when the detector head is at 90 degrees to the light beam. The CCD
is still 10 capable of detecting the light and reflecting the beam into the optical blocks. The same mechanisms are at work in these situations for detecting where the beam is broken by patient interference.
When the camera is taking a view at a single spot, the detector head lowers until 15 beam breakage is detected. The camera will then stop lowering towards the patient and take the required view. The detector head is able to located the ideal height without any trial and error movements.
Some patients are uncomfortable in having the detector head close to their profile.
20 With the present invention, the depth preferred by the patient can be preset so that the detector head stops at the preferred height without getting too close to the patient (ie:
without waiting for beam breakage to be detected). For example, if it is known that the patient is most comfortable when the detector head is at a preferred height corresponding to element 240 (out of 256 elements of the CCD), but breakage will not occur until element 250, then this preferred height can be preset. In this way, the apparatus does not have to lower only until beam breakage is detected. The detection system can be overridden by a preset condition. The preset condition will allow the detector head to stop lowering towards the patient at any level.
When a preset condition is used, the camera will adjust as if beam breakage is detected at the preset condition. So, in the above example, if beam breakage will be detected at element 250, but the preferred height is at element 240, then the camera will stop movement at the position where beam breakage would be detected at element 240.
This preset override can also be used in total body views. For example, if the detector head travels along the X axis for the profile view, and the Z axis for height relative to the patient, a number of preset conditions can be entered such that the detector head automatically adjusts its height along the Z axis at particular locations along the X
axis. This again, prevents the camera from lowering as close as possible to the patient (the point of beam breakage). These scenarios are useful in cases where the patient is extremely uncomfortable in having the detector head too close.
Referring to Figure 15, the present invention also includes a computer processing means 600, with processor 610 for processing the data received by the height detection apparatus and for controlling the automatic adjustment of the camera. The height detection information is processed in real time and fed to a motion control unit 620 which is capable of adjusting the position of the camera, thereby minimizing the distance between the camera and the patient. The scintillation camera 5 also includes an interface 630 with on screen menus and function input means for selecting a variety of scintillation camera functions, including preset conditions for controlling the height of the detector head. The operator 640 may enter the preset conditions at interface 630, which is fed to motion control unit 620 which is capable of adjusting the camera to the preferred height or heights set.
While the invention has been described according to what is presently considered to be the most practical and preferred embodiments, it must be understood that the invention is not limited to the disclosed embodiments. Those ordinarily skilled in the art will understand that various modifications and equivalent structures and functions may be made without departing from the spirit and scope of the invention as defined in the claims. Therefore, the invention as defined in the claims must be accorded the broadest possible interpretation so as to encompass all such modifications and equivalent structures and functions.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of adjusting the path of a scintillation camera, the scintillation camera including a detector head and a detector head surface, the method comprising the steps of:
moving the detector head with respect to a patient;
projecting a beam of light across the detector head surface from a single light source;
sensing the beam of light at multiple depths;
reflecting the beam of light into at least one optical bar;
detecting when the beam of light is broken; and stopping movement of the detector head when beam breakage is detected.
moving the detector head with respect to a patient;
projecting a beam of light across the detector head surface from a single light source;
sensing the beam of light at multiple depths;
reflecting the beam of light into at least one optical bar;
detecting when the beam of light is broken; and stopping movement of the detector head when beam breakage is detected.
2. A method of adjusting the path of a scintillation camera, the scintillation camera including a detector head, the detector head having a position relative to a patient, the method comprising the steps of:
moving the detector head position with respect to the patient;
projecting a beam of light across the detector head from a single light source;
sensing the beam of light at a multiple of depths;
reflecting the beam of light into at least one optical bar;
detecting when the beam of light is broken;
stopping movement of the detector head when beam breakage is detected at a first depth; and when beam breakage is no longer detected at the first depth, adjusting the detector head position until beam breakage is detected at a second depth.
moving the detector head position with respect to the patient;
projecting a beam of light across the detector head from a single light source;
sensing the beam of light at a multiple of depths;
reflecting the beam of light into at least one optical bar;
detecting when the beam of light is broken;
stopping movement of the detector head when beam breakage is detected at a first depth; and when beam breakage is no longer detected at the first depth, adjusting the detector head position until beam breakage is detected at a second depth.
3. An apparatus for adjusting the path of a scintillation camera, the camera comprising a detector head and a detector head surface, the apparatus comprising:
a light source for projecting a beam of light across the detector head surface;
a light detector for sensing the beam of light;
at least one optical bar;
a mirror for reflecting the beam of light into the at least one optical bar;
means to detect when the beam of light is broken; and means to stop movement of the detector head when beam breakage is detected.
a light source for projecting a beam of light across the detector head surface;
a light detector for sensing the beam of light;
at least one optical bar;
a mirror for reflecting the beam of light into the at least one optical bar;
means to detect when the beam of light is broken; and means to stop movement of the detector head when beam breakage is detected.
4. The apparatus for adjusting the path of a scintillation camera as claimed in claim 3, wherein the apparatus is mounted to the side of the detector head.
5. A method of adjusting the height of a scintillation camera automatically, the scintillation camera including a detector head, the method comprising the steps of:
presetting at least one height condition for the detector head relative to a patient;
moving the detector head with respect to the patient; and stopping movement of the detector head when the detector head reaches preset height condition.
presetting at least one height condition for the detector head relative to a patient;
moving the detector head with respect to the patient; and stopping movement of the detector head when the detector head reaches preset height condition.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2310533 CA2310533A1 (en) | 2000-06-02 | 2000-06-02 | Apparatus and method for automatically adjusting the path of a scintillation camera |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2310533 CA2310533A1 (en) | 2000-06-02 | 2000-06-02 | Apparatus and method for automatically adjusting the path of a scintillation camera |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2310533A1 true CA2310533A1 (en) | 2001-12-02 |
Family
ID=4166368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2310533 Abandoned CA2310533A1 (en) | 2000-06-02 | 2000-06-02 | Apparatus and method for automatically adjusting the path of a scintillation camera |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2310533A1 (en) |
-
2000
- 2000-06-02 CA CA 2310533 patent/CA2310533A1/en not_active Abandoned
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