WO2004002315A2

WO2004002315A2 - Method for changing the sighting devices of isotope scanning sensors

Info

Publication number: WO2004002315A2
Application number: PCT/EP2003/050254
Authority: WO
Inventors: Jean-Claude Geay
Original assignee: Sopha Medical Vision International
Priority date: 2002-06-26
Filing date: 2003-06-24
Publication date: 2004-01-08
Also published as: FR2841457A1; FR2841457B1; AU2003255517A1; WO2004002315A3; AU2003255517A8

Abstract

In order to facilitate the changing of sighting devices (11) in a nuclear medicine machine (1), a bed (2) is raised in order to bring a patient towards the machine in order to examine said patient. When the bed is raised, a space is easily created between a leg (3) of the bed upon which the bed rests upon the ground and a frame (4) of the machine. This space is used to bring forward the carriage of a sighting device holder and to carry out all necessary maintenance operations.

Description

Method for changing the collimators of scintigraphy detectors

The present invention relates to a compact nuclear medicine machine, that is to say capable of acquiring an image of nuclear medicine in a reduced space. The invention also relates to the use of this machine. The use of such a compact machine is justified in particular when the customer with whom it is installed has a normal room in his office to receive this machine. A normal room is a small room compared to an examination room as found in hospitals. An examination room is generally large to accommodate large machines.

The nuclear medicine machine of the invention is preferably a nuclear medicine machine with absorption distortion correction but not necessarily. These machines can also be used in so-called intermodal sets for which images of different types are merged, and compared, in order to improve the diagnoses advanced by practitioners.

There are two types of image acquisition machines in medicine: on the one hand, there are anatomical machines, and on the other hand, functional machines. The purpose of anatomical machines is to show the shape of organs, and their arrangement in the human body. The best known anatomical machines are conventional radiology machines, CT scanners, ultrasound scanners and NMR machines. Among the functional machines, the ANGER gamma cameras are essentially known as well as the so-called PET (Positron emission tomography - positron emission tomography) machines.

These functional machines, also called nuclear medicine machines in this case, require the injection into the body of a patient of a radioactive isotope. The isotope is associated with a biological product which is metabolized in various selected places of the human body. At the time of this metabolism, the isotopes are fixed in the chosen organ and emit gamma rays. These gamma rays are captured by gamma ray detectors, preferably after being collimated. Among these gamma ray emissions certain emissions are particular. They relate to positron emissions for which two gamma photons are emitted in opposite directions from each other, simultaneously. We therefore know how to manufacture on the one hand conventional machines detecting gamma rays, and on the other hand so-called PET machines measuring the occurrence of these positrons. In both cases, by the number and distribution of sources of detected radiation, the activity of the chosen organ is measured.

Nuclear medicine machines therefore have the particularity of offering images of radioelectric events which arise inside the human body. For this reason, they are also called transmitting machines.

For the acquisition of tomography images, in nuclear medicine as well as in tomodensitometry, it is known to acquire a series of images in projection, according to incidences offset from each other by a small difference. The smaller the difference, the better the resolution of the tomographic image. In practice, in order to be able to thus carry out acquisitions according to incidences varying progressively over at least 180 ° around the patient's body, a detector, or several detectors, is placed in a mobile device, rotating around the patient's body.

The examination of the body of a patient is carried out in the following manner in such machines. The patient is placed, with an area to be examined of his body opposite the detection area of the nuclear medicine machine. While the patient is in this position, the machine acquires emission images for different incidences of the detectors around the patient's body. For example, the acquisition of images can take 20 seconds for each, and, by taking them with incidences offset by 5 °, we arrive at an examination duration of 12 minutes. For a cardiac examination, the duration thus considered would correspond to a state of the heart. By synchronization methods, one could also measure other images for other states of the heart, leading for example to an examination time of one hour if one wants to have five states. The patient therefore spends some time in the machine.

The gamma ray detectors, according to a variant, are carried by arms describing around the patient's body a circular path. A stand from which these arms come out is a massive stand. The patient's body is brought opposite these arms until the head of the patient's support bed, also said sometimes tray or patient support panel, come up against this stand. These arm machines have the advantage, for the patient, of not feeling confined in a machine. An arm machine is however complex to produce and therefore expensive. Other machines called tunnel machines in principle have a crown carrying detectors. When turning with this crown, the detectors describe a tunnel. For the examination, the patient is brought to pass normally in the crown in a horizontal position, and if necessary in the tunnel if the movement of the detectors occurs in a casing forming this tunnel. The examination with such a tunnel machine can more easily be a whole body tomographic examination than with an arm machine.

Intermediate machines have a circular crown portion which, on the one hand, supports the detectors and which, on the other hand, can slide in a stand to produce all the desired incidences. These intermediate machines are much less expensive and do not cause claustrophobia. In addition they allow examinations where the patient is vertical or seated. These exams are, for example, stress exams: the patient has to make an effort during the exam, for example pedaling on a fixed velocipede.

The improvement of the invention is more particularly intended for machines of the tunnel type, but it can be applied just as well to machines with arms and to intermediate machines. Its interest can be proven in all cases. The detectors used in nuclear medicine machines require the interposition of a collimator on the path of propagation of the detected gamma rays. A collimator is formed by a thick plate, generally made of tungsten, pierced by a multitude of parallel or converging holes, perpendicular or inclined obliquely on the surface of the detector. The number, diameter and distribution of these holes depends on the examination to be performed, typically the injected isotope, and on the organ to be examined. To make the nuclear medicine machine flexible, it is therefore planned to provide it with a certain number of different collimators and to change collimator for a given examination. The sights are heavy. In one example, they weigh around 70 kilograms each. Their manual positioning is nevertheless facilitated by the use of a collimator carriage with which they are transported, presented for hanging on the detectors, or with which they are removed. The handling of this trolley is however hampered by the presence of the examination bed which must accommodate the patient, and which is waiting opposite the detectors. The change of a collimator, which involves the manipulation of the collimator carriage, must therefore also include the prior and subsequent manipulation of the examination bed by rolling on the ground to free it from the proximity of the detectors. This manipulation is not very easy in a small room. Therefore the size of the room must at least correspond to the space necessary for these manipulations of the examination bed. However, this is not always possible.

In the invention, to remedy these problems, rather than moving the bed on the ground by translation, provision is made to use a bed which can be lifted vertically, by tilting around a foot of this bed. For example, the examination bed has a tray carrying at least one end on a footboard. The carrying mechanism at the location of this foot comprises in one example a shaft held at the top of the foot of the bed, and a bearing formed in the body of the bed, preferably at one end of the body of the bed. The assembly is such that the bearing can rotate on the shaft, carrying with it the body of the bed, part of which, one end, rotates directly on the shaft, and the other end of which then approaches the ceiling of the room. The foot which comprises the tilting shaft is preferably a foot remote from the machine if the bed comprises several feet. A space is then left free opposite the detectors for approaching the collimator carriage, or even for manually changing certain collimators directly into two parts, each part weighing half the weight.

The subject of the invention is therefore a method for changing the collimators of scintigraphy detectors of a nuclear medicine machine to acquire a nuclear medicine image of a body of a patient under examination, characterized in that it includes the following steps:

- an examination bed is tilted into a vertical position opposite a frame carrying the scintigraphy detectors, by means of a mechanism provided with a horizontal tilting axis, to release a space opposite of these detectors,

- we approach a collimator between the frame and the base,

- we remove or hang a collimator on a detector. The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are presented for information only and in no way limit the invention. The figures show:

- Figures 1a to 1d: schematic representations of the nuclear medicine machine of the invention;

- Figures 2a and 2b: representations of two stable states of the bed of the invention, in the examination position and in the tilting position respectively;

- Figure 3: a top view of a base of the bed of the machine of the invention occupying two positions.

Figures 1a to 1d show a nuclear medicine machine 1. The machine 1 is intended to acquire nuclear medicine images of the body of a patient under examination (not shown). The machine 1 has an examination bed 2 and a foot 3 for carrying this bed. The bed 2 is cantilevered with respect to the foot 3. The machine 1 also has a frame 4 carrying two scintigraphy detectors 5 and 6. In one example, the two detectors 5 and 6 have rectangular and planar detection fields. For example, a normal 7 in the center of the detection plane of the detector 5 is oriented in the direction of the observer looking at FIG. 1a. The detector 6 is tilted on the detector 5 so that a normal 8 to the detection plane of this detector 6 intersects the normal 7. Preferably, the normals 7 and 8 intersect at an angle of approximately 90 °.

The detectors 5 and 6 are carried by the frame 4 by means of a crown 9 which can rotate in rotation in the frame 4 around an axis of rotation 10. The axis 10 is perpendicular to the plane of the normals 7 and 8. In one example, the detectors 5 and 6 are fixedly mounted on the crown 9. It would however be conceivable that they are mounted on this crown 9 with tangential and or radial translation possibilities relative to the axis 10, or still with orientation possibilities to modify the cutting angle of the two normals. Alternatively also, there could be more than two detectors. The axis of rotation 10 is offset above the horizontal plane of the bed 2. The crown 9 and the frame 4 at the location of the axis 10 are hollow. Under these conditions, as shown in FIGS. 1a to 1c, the foot 3 can approach the machine and cause the passage of the bed 2, by its cantilever end, through the body of the machine 1 Therefore, different parts of the patient's body are presented opposite detectors 5 and 6.

As shown in the figures, each detector such as 5 has a collimator 11 on its detection face. This collimator 11 is for example fixed to the detector 5 by bolts 12.

In FIGS. 1a to 1c, with the incidence shown, the detector 6 occupies a position overhanging the bed 2 while the detector 5 is placed laterally to this bed. It is easy to see that the presence of bed 2 is a hindrance for changing the collimators 1 1 and that it requires being able to remove this bed 2. If a wall 13 of the room in which the machine 1 is placed is too close to this machine 1, moving bed 2 will be difficult and changing the collimators will be laborious.

To solve this problem, in the invention, provision has been made to tilt the bed as shown in FIG. 1d. For this purpose, first of all the foot 3 is moved back so that the latter occupies a position similar to that of FIG. 1a, for example very close to the wall 13. Secondly, if the machine 1 is a nuclear medicine machine of the type with a crown, the detectors are rotated so that the detector 5 occupies a position under the bed 2 while the detector 6 is placed laterally on the bed 2. To obtain this result, it suffices to turn the crown 9 a quarter turn relative to the position of Figure 1a. The bed has two ends. A first end 14, cantilevered, is intended to enter the crown and into the frame 4. A second end 15 is opposite the end 2, and is that by which the bed 2 is hooked to the foot 3 Removal of the foot 3 is carried out in such a way that the end 14 can easily rise out of the crown 9, and if necessary as shown in FIG. 1d, in the space freed by the rotation of the detectors 5 and 6. In doing so, it is noted firstly that the access space to detectors 5 and 6 is completely freed. Secondly, in the example, the detector 5 is already in place so that its input collimator 11 can be directly removed from it (oriented towards the field to be detected, that is to say upwards). In a known manner the carriage which can approach between the frame 4 and foot 3 will simply raise this collimator 11 using a gantry. Thirdly, the space required for this operation is small, of the order of 1.50 m between the detectors 5 and 6 and the wall 13. Preferably the body of the bed is constituted by a light structure, typically made of wood (in plywood or glued laminated material) and its manual lifting by manipulation of the end 14 is within the reach of an operator who is not particularly muscular, an operator.

The two positions of the bed, examination position and raised position, are preferably stable positions. This can be achieved in different ways. In particular, a shaft 16 for rotation of the end 15 of the bed 2 can be provided with a brake preventing tilting. Otherwise, the cantilever offset of the end 14 of the bed on the one hand and of a mechanism 17 for hooking the bed close to the end 15 on the other hand can allow this double stability. For example, FIG. 1a where the bed 2 is horizontal, its length is such and the end 14 is sufficiently distant from the shaft 16 so that the counterweight formed by the mechanism 17 is insufficient to raise the bed 2.

By cons, Figure 1d, in the position where the bed 2 and the mechanism 17 are located on the same side relative to the shaft 16, the bed 2 is in a stable position against the wall 13. If necessary the stable position can be obtained by hooking the bed 2 against the wall 13 when it is raised. Support for the end 14 in the frame 4 on the one hand and against the wall 13 on the other hand can be used to limit the movement of the bed 2 so that it is stable in the two positions.

FIGS. 2a and 2b show construction details of the bed 2 and of the foot 3. At the end 15 and with the mechanism 17, the bed 2 is mounted integral with a spacer 18 of trapezoidal shape, with small base at the bottom, and having in this small base a bearing 19. The foot 3 having a certain thickness (measured perpendicular to the plane of the figure), the tilting mechanism may include another spacer, parallel and of the same type as the spacer 18 also provided a landing, and located in correspondence on the other side of the thickness of the foot 3. This thickness is of the order of the width of the bed 2, or even greater. These two spacers are interconnected by an angle iron 20, one of the wings 21 of which is fixed to the end 15. The wing 21 and the other wing 22 of the angle iron 20 are fixed, in particular by mechanical welding to the spacers 18 and thus form a tilting bell. The wing 22 does not extend to the base 23 of the spacer 18 so that in the raised position, FIG. 2b, this wing 22 does not come up against an upright of the foot 3.

The nuclear medicine examinations envisaged with the machine of the invention are preferably examinations of the tomography type, in particular of the cardiac tomography type. In these examinations, it is necessary that the position of the bed relative to the axis 10 can be modified both in height, vertically, and laterally, in a horizontal plane perpendicular to the plane of the figure. For this purpose, the foot 3 which carries the cantilever bed has at the location of the end 15 attachment a jack system allowing the top 24 of the foot 3 to rise above the ground. The bearing 19 of the spacers 18 allows the passage of the shaft 16 secured or mounted in free rotation at the top of the foot 3. The shaft 16 is horizontal and allows tilting, passage of Figures 2a to 2b. It is this shaft 16 which is rotated when the bed is tilted to the vertical.

The tilting system 18-22 also has another mechanism allowing lateral translation. For this purpose, the end 15 is embellished with an end rail 25 parallel to the width of the bed 2 (perpendicular to the planes in FIGS. 2a and 2b). This rail 25 extends over the entire width of the end 15 of the bed 2. This rail 25 slidably receives a head 26 fixed to the wing 21. The head 26 has, in the upper part remote from the wing 21, extensions 27 and 28 sliding above the edges 29 of the rail 25 and ensuring the solidarity of the bed 2 to the angle 20, while allowing the lateral movement of this bed 2 parallel to the axis 10. For this purpose the wing 22 of the angle iron 20 also carries a motor 30 driving by means of an endless screw 31 gears 32 causing the displacement of the rail 25 along the head 26. The base of the foot 3 has a wheel 33 which rolls on the ground. The wheel 33 allows the bed 2 to move in order to occupy with respect to the frame the positions shown in FIGS. 1a to 1d. Furthermore, so that the movements of the bed relative to the frame are made in an aligned manner, the base 34 of the foot 3 is guided by a guide 35 sliding in this base 34. Figure 3 shows for two positions, for example the positions of Figures 1a and 1c, the position of the base 34 of the foot 3 of the bed. Typically, a shaft 35 forming a guide is supported by brackets 36 and 37 above a base plate 38. This shaft 35, rigid, is sufficiently thick, for example with a diameter of two centimeters, and is also wedged relative to the frame 4 of the machine 1. The base 34 has a horizontal spar 39 provided at one end 40 with a bush 41 which receives the shaft 35. At its other opposite end, the spar 39 carries the wheel 33. This is only shown here symbolically. The spar 39 also carries a mast 42 of the foot 3. This mast 42 has the particularity of being able to rise in height to cause the elevation of the bed 2. The bed 2 is not shown in FIG. 3 but it is understood that 'It is carried, cantilevered, from the top of the mast 42, in the direction of the frame 4, parallel to the axis 10.

With such a solution, the stiffness of the bed 2 may be insufficient to carry the weight of a patient 43. For this purpose, the frame 4 may include a jack 44 which takes up the force and prevents the bending of the bed 2.

In position 45, where the end 15 of the bed 2 has been approached to the frame 4, a stop can be provided in the console 36 so that the spar 39 does not come to abut at 46 against one of the two detectors but that these can continue to rotate with the crown 9 in the frame 4.

The means which are provided so that the bed 2 occupies a distant position at the time of the tilting of FIG. 1 d can be of several types. First simply the frame may have been placed at such a distance from the wall 13 that it suffices to come into abutment with the horizontal bed against the partition 13 to know that this position corresponds to the position in which the tilting of the bed 2 is possible . If necessary, at the corresponding places of the wall 13, rubber stops will be provided to avoid scratching the paint. Otherwise, the console 37 can be arranged in such a way that it forms a limit stop and that the lifting of the bed 2 is possible when the spar 39 is in abutment against it. If necessary, a mark will be made on the ground to indicate the (imitates beyond which the tilting is possible, or on the contrary not possible.

In the example shown, the detectors 5 and 6 are cantilevered with respect to the frame 4. In this case, in particular as shown in FIG. 1d, prior to lifting, the crown 9 so as to clear the space above the end 14 so that the bed can straighten. However, it is possible that the frame 4 is provided with two crowns placed on either side of the detectors and that this frame 4 itself is located on either side of the detectors. The detectors are no longer overhanging. In this case, this preliminary operation will no longer be useful since a casing of the frame will in any event prevent the end 14 from rising. In this case, it is necessary to provide a distance from the foot of the machine 1 such that the end 14 can be extracted from the tunnel of this machine. However, in all cases, raising the bed provides a good solution because it makes it possible to free up a space between the frame 4 and the foot 3 of the bed and this for a reduced dimension of the examination room.

As much as the invention is particularly suitable with a single-legged bed, it would also be possible to envisage it with a two-legged bed. In this case, the second leg which would be located near the end 14 could have a device to be able to be folded along the bed 2 when the latter is vertical.

The motorization of the bed 2 and of the foot 3 so that the bed 2 passes through the machine can be obtained by motorizing the wheel 33, or else by arranging in the lower part of the bed 2 a rack which meshes in a motorized pinion carried by the frame 4.

Claims

1 - Method for changing collimators (11) of detectors (5, 6) of scintigraphy of a machine (1) of nuclear medicine to acquire a nuclear medicine image of a body (43) of a patient under examination, characterized in that it comprises the following stages:

- An examination bed (2) is tilted into a vertical position opposite a frame (4) carrying the scintigraphy detectors (5, 6), by means of a mechanism (17) provided with an axis (16) horizontal tilting, to clear a space facing these detectors,

- we approach a collimator between the frame and the base,

- we remove or hang a collimator on a detector.

2 - Method according to claim 1, characterized in that:

- Rotating a crown (9) carrying the detectors to clear a space located at the location of the detectors, above one end (14) of the bed before tilting the bed.

3 - Method according to one of claims 1 to 2, characterized in that:

- a foot (3) carrying the bed is moved back from a position where the bed allows the examination of the patient to a position where the bed is very close to a wall (13) distant from the frame carrying the scintigraphy detectors ,

4 - Method according to claim 3, characterized in that

- The bed is moved relative to the frame by rolling a wheel (33) with a base of the foot. 5 - Method according to one of claims 1 to 4, characterized in that:

- One end (24) of the foot is raised above the ground by means of a jack system.

6 - Method according to one of claims 1 to 5, characterized in that:

- The bed is laterally translated parallel to an axis (10) of rotation of the machine, by means of a sliding mechanism (25-29).

7 - Method according to one of claims 1 to 6, characterized in that: - the lateral movement of the bed is electrically actuated (30) top of the foot.

8 - Method according to one of claims 1 to 7, characterized in that:

- a collimator is approached or removed using a cart placed between the bed and the detectors.