JP2008029647A - Laser pointer apparatus, its system and calibration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically and highly precisely focus the aim of a light projection unit on a fixed position. <P>SOLUTION: This laser pointer is provided with a laser-light projection unit 61 provided on a certain face in a room storing a medical radiation apparatus and emitting a crossline laser, a light sensor unit 62 provided on an opposite face to the certain face and receiving the crossline laser from the laser-light projection unit, and a control means executing a feedback-control of the laser-light projection unit based on the detection output of the light sensor unit so that the crossline laser is irradiated from the laser-light projection unit to the prescribed position on the light sensor unit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser pointer device, a system thereof, and a calibration method, and more particularly to a laser pointer device, a system thereof, and a calibration method for positioning a subject in a medical system including a radiotherapy device.

  In stereotactic irradiation (STI) using a gamma knife or linac, normal surroundings can be achieved by concentrating radiation from various directions to the lesion (brain tumor, arteriovenous malformation, etc.) located by CT imaging. The dose to tissues is reduced as much as possible. For this reason, it is necessary that the reference positions (coordinates) managed by the X-ray CT apparatus and the radiation therapy apparatus are exactly the same in units of mm or less.

  In order to accurately specify the position of the patient's lesion by CT imaging, it is necessary to perform CT imaging with the patient fixed in advance at the reference position of the system. Conventionally, a laser cross mark is projected from three upper and left projectors, usually 2 m or more away from the patient on the bed, and the laser cross mark is irradiated to the mark on the patient's body surface. There is known a patient positioning device that specifies accurate position information of a lesion by aligning with a position (system reference position) (Patent Document 1).

  However, the beam emission direction of the laser projector changes slightly (about several microns) due to changes in temperature and humidity and changes over time, and the influence of shake due to this change reaches several mm or more at the position of a patient 2 m or more away. This positional error cannot be ignored. For this reason, the user has to perform troublesome operations such as confirmation and adjustment (calibration) of the positional deviation of the laser pointer before using the apparatus or at least once a day.

Specifically, this adjustment operation is performed by first performing CT imaging of the dedicated phantom for alignment, and setting the dedicated phantom to the CT imaging reference position (the ISO center and a predetermined position in the body axis direction) based on the reconstructed image. After alignment, the aim of the laser projector was adjusted to the dedicated phantom after the alignment.
JP 2000-287966 (paragraph “0003”, FIG. 6)

  However, since the distance between the laser projector and the dedicated phantom is usually 2 m or more, it is extremely difficult to aim alone. In addition, in a laser projector that irradiates a cross line laser (cross mark) with a single light source, the effect of minute adjustments on the horizontal line laser also affects the vertical line laser. It was difficult.

  The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to provide a laser pointer device capable of automatically aligning the aim of the laser projection unit at a fixed position with high accuracy, and its It is to provide a system and a calibration method.

The above problem is solved by the configuration of FIG. That is, the laser pointer device of the present invention (1) is a laser pointer device for positioning a subject in a medical system including a radiotherapy device, and is provided on a certain surface in a room that houses the radiotherapy device. A laser projection unit 61 for emitting a crossline laser, a photosensor unit 62 for receiving a crossline laser from the laser projection unit provided on an opposite surface of the certain surface, and a detection output of the photosensor unit And a control means for performing feedback control of the laser projection unit so that the cross-line laser from the laser projection unit is irradiated to a predetermined position on the optical sensor unit.

  In the present invention (1), the beam emission direction of the laser projection unit 61 is slightly changed due to the influence of temperature, humidity, distortion, etc. in the light source unit. ) Occurs, almost no displacement (offset) occurs at the light receiving position of the facing optical sensor unit 62, so that the control means can calibrate the irradiation position of the cross-line laser with extremely high accuracy.

  In addition, since it is not necessary to perform a troublesome adjustment work using a dedicated phantom as in the past, a highly accurate laser pointer function can be easily maintained.

  In this invention (2), in the said invention (1), the said laser projection unit is comprised so that the projection attitude | position of the vertical line laser and horizontal line laser which comprise a cross line laser can be controlled mutually independently. . High-accuracy alignment adjustment for each single-line laser is relatively easy, and an extremely high-accuracy cross-line laser can be easily obtained by adjusting the alignment of the horizontal and vertical line lasers.

  In the present invention (3), in the above-mentioned present invention (2), in the optical sensor unit, the arrangement direction of each detection element is orthogonal to each end line of the vertical line laser and horizontal line laser constituting the cross line laser. The four photosensor arrays provided as described above are provided. Therefore, highly accurate alignment control can be efficiently performed using a small number and size of optical sensor arrays.

  In the present invention (4), in the above-mentioned present invention (3), the control means is arranged on each photosensor array based on a detection signal received in advance by a cross-line laser from a laser projection unit directed in a predetermined direction. Initial setting means for obtaining a light receiving position and storing the obtained light receiving position in a memory as a reference position is provided. Therefore, even if the mounting position of each photosensor array is not strict, it is possible to accurately specify the reference position and store the position, and thereafter easily perform highly accurate alignment adjustment of the cross-line laser.

  In the present invention (5), in the present invention (4), the control means may be configured such that one end of the line laser is not irradiated to the reference position on the optical sensor array, so that the one end of the line laser is The laser projection unit is feedback-controlled so as to be displaced by a certain amount in the direction of the position, and irradiation position calibration means for alternately performing the feedback control for both ends of the line laser is provided. Therefore, the single line laser can be driven to an accurate irradiation position by a simple adjustment algorithm with two-point control.

  A laser pointer system of the present invention (6) is a laser pointer system comprising a plurality of laser pointer devices according to claim 1 in a room of a medical system provided with a radiation therapy device, wherein the ceiling laser projection unit and the floor surface are provided. First and second laser pointer devices each including a photosensor unit, and second and third pairs provided on opposite wall surfaces so that a pair of each laser projection unit and the photosensor unit facing each other face each other. The laser pointer device is provided so that the cross line lasers from the first to third laser pointer devices intersect at one point in the room. Therefore, the position of the patient's lesion can be accurately adjusted to one point in the room.

  Preferably, the cross-line lasers from the first to third laser pointer devices are provided so as to be orthogonal at one point in the room, but are not necessarily orthogonal. Four or more such laser pointer devices may be provided according to the purpose of the medical system.

  A calibration method for a laser pointer device according to the present invention (7) is a calibration method for a laser pointer device in a medical system comprising an X-ray CT device and the laser pointer device according to claim 3, A step of imaging a dedicated phantom arranged in the direction of the dimensional coordinate axis with an X-ray CT apparatus, and matching a reference position where each needle line of the dedicated phantom is orthogonal to a reference position managed by the X-ray CT apparatus based on the reconstructed image; Adjusting the projection posture of the laser projection unit so as to irradiate the crossline laser toward the reference position of the dedicated phantom after the alignment; and the crossline laser from the laser projection unit after the adjustment Light received by the facing photosensor array and obtained on the basis of each detection signal on each photosensor array Those comprising the steps of: storing in the memory the optical position as the reference position.

  Such initial setting work may be performed at least once at the time of introduction of the medical system, and thereafter, based on information on a reference position (an ISO center on the xy plane and a predetermined position in the body axis direction) stored in the memory. The reference position of the system can be easily maintained (maintained).

  According to the calibration method of the laser pointer device of the present invention (8), the laser projection unit is configured so that the cross-line laser from the laser projection unit after the calibration is irradiated to the reference position on the facing optical sensor unit. The method further includes a step of feedback-controlling the light projection posture. Therefore, the reference position of the medical system can be accurately and easily reproduced at any time.

  As described above, according to the present invention, by automating the calibration work of the laser pointer device, it is possible to reduce the burden on the operator work and prevent accidents due to human calibration errors, and to operate the medical system safely and efficiently. The place that contributes to is extremely large.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.

  1 to 4 are views (1) to (4) showing a configuration of a radiotherapy system according to the embodiment, and FIG. 1 shows a case where a treatment room accommodating the radiotherapy system is viewed from one direction. This system is a system in which a radiotherapy apparatus (not shown) and an X-ray CT apparatus 100 are combined. Here, reference numeral 10 denotes a scanning gantry for collecting projection data of an axial / helical scan of a subject by an X-ray fan beam. , 30 is an operation console for performing remote control of the scanning gantry 10 and a couch table 20 (not shown), reconstructing a CT tomogram, and performing various setting operations by the operator. A rail 41 is embedded in the floor surface, and the scanning gantry 10 is provided so as to be movable on the rail 41.

A laser projecting unit 61T that emits a cross-line laser (a cross mark by a laser beam) is embedded in the ceiling, and an optical sensor unit 62B that receives the cross-line laser from the laser projecting unit 61T is disposed on the floor surface facing the laser projecting unit 61T. Is buried with its light-receiving surface facing the ceiling. Further, a set of laser projection unit 61L and optical sensor unit 62R and a set of laser projection unit 61R and optical sensor unit 62L are embedded in the left and right wall surfaces so as to face each other. Are provided so as to be orthogonal to each other at one point in the room.

  Although not shown, four or more laser pointer devices may be provided according to the treatment purpose of the medical system, or each cross line laser may be provided to cross (non-orthogonal) at a plurality of points in the room. good.

  FIG. 2 shows a side view of the treatment room of FIG. 1 as viewed from the right wall. The scanning gantry 10 includes an X-ray tube 11 facing each other with a subject (not shown) interposed therebetween, and an X-ray detector 12 that detects transmitted X-rays from the subject, and these are arranged around the subject body axis. The transmission data of the subject is collected by rotating.

  A bed table 20 on which a subject is mounted is provided in front of the scanning gantry 10 so as to be movable on a rail 41. Here, 21 is a top plate (cradle) for mounting the subject and moving it in the body axis direction, 22 is an intermediate support part (IMS: Inter Midiate Support) for moving the top plate 21 in the body axis direction, and 23 is the IMS 22. An upper structure 24 that is moved in the body axis direction is a support structure that supports the upper structure 23 so that it can be raised and lowered on the floor surface and is rotatable about the rotation axis AT. In addition, the top plate 21 shown in the figure shows a state in which it is rotated by 90 ° around the rotation axis AT so as not to obstruct the cross line laser.

  Furthermore, a radiation therapy apparatus 200 is provided on the opposite side of the bed table 20 so as to be movable on the rail 41. An example of the radiotherapy apparatus 200 is a linac therapy apparatus, 51 is a collimator that collects radiation (X-rays) irradiated to a subject, 52 is a head that supports the collimator 51 at the tip, and 53 is a rotation axis of the head 52. It is a gantry that is supported so as to be rotatable around AH.

  The laser pointer system according to the present embodiment is provided in the middle of the X-ray CT apparatus 100 and the radiation therapy apparatus 200, and three cross-line lasers can be accurately used at any time with respect to a reference point in a three-dimensional space in the medical system. Can be crossed (orthogonal). This will be described below.

  FIG. 5 is a diagram for explaining a laser pointer device according to the embodiment, showing a case where a cross-larin laser (cross mark) is irradiated from the laser projection unit 61L on the left wall surface to the optical sensor unit 62R on the right wall surface. Yes. The laser projection unit 61L includes a vertical line laser and a horizontal line laser light source section constituting a cross line laser, and can control the projection posture (emission position, direction, etc.) independently. Yes. Such a laser projection unit 61 can be realized by combining two known single-line laser generation sources horizontally and vertically so as not to interfere with each other's optical path.

  The inset (b) schematically shows the structure of the laser generation source as an image in which displacement (force) is applied to the horizontal line laser and vertical line laser in the emission direction. Now, when focusing on the horizontal line laser, both ends of the line laser can be finely adjusted up and down by the line laser emission posture (position, direction, etc.) by (force) FL, FR through a minute passage generated by an actuator (not shown). Has been. The minute change in the emission direction in the laser light source section is a large offset amount of several mm or more on the facing wall 4m to 5m away, so the actuator for fine adjustment of the emission direction can control the displacement with high accuracy. A geared motor or a piezoelectric element (such as a piezo element) is used. The same applies to the light source unit of the vertical line laser.

On the other hand, four light beams are provided on the facing wall so that the arrangement directions of the detection elements are orthogonal to the end lines of the vertical and horizontal line lasers, corresponding to the irradiation positions of the end portions of the cross line laser. Sensor arrays 63T, 63B, 63L, and 63R are provided. The dimensions of the cross line laser irradiated on the wall surface are, for example, 2 m for the vertical line laser, 4 m for the horizontal line laser, and about 1 mm for the laser width. Accordingly, a cross-line laser having a vertical length of 1 m, a horizontal level of 2 m, and a width of 0.5 m can be applied to the subject in the middle part.

  In each photosensor array 63, photodetection elements (cells) such as photodiodes are arranged in a line at several tens to several hundreds of micro pitches. Virtual numbers 0 to m (or 0 to n) are assigned to the respective cells, so that it is possible to easily identify which cell is irradiated with the line laser. In the illustrated photosensor array, each cell is arranged on an arc centered on the cross-line center, but the present invention is not limited to this. The photosensor array may be arranged in a straight line.

  In each cell, as shown in the inset (a), by comparing the light reception output of the detection surface with a predetermined threshold value TH, a detection signal = 0 is output in a cell not irradiated with laser light, and is irradiated. The detection signal = 1 is output in the cell in which the signal is present. An example of the detection signal is “1” at the positions of the cell numbers p to q. Detection signals from such cells of the optical sensor array 63R are input in parallel to the data multiplexer (DMX) 654 of the pointer controller 65. The same applies to the optical sensor array 63L.

  The pointer control unit 65 emits light from the horizontal line laser so that the horizontal line laser is irradiated to a predetermined position (reference position described later) on the photosensor arrays 63L and 63R based on the detection outputs of the photosensor arrays 63L and 63R. Perform feedback control for the unit. This will be described below.

  In the pointer controller 65, the counter (CTR) 651 repeatedly counts 0 to m. The DMX 654 scans each input light detection signal by the count input of the CTR 651, and outputs an output signal = 1 at the timing of the input detection signal = 1. The LP correction processing unit 652 reads the count output of the CTR 651 at the timing of the output signal = 1, thereby identifying the cell number (address). When the scan for one time is completed, the LP correction processing unit 652 obtains a substantial detection position as the photosensor array 63R based on the address of each cell in which the photodetection signal = 1. As shown in the inset (a), if the detection signal = 1 from the cell address p to q, the actual detection position HRr = (p + q) / 2 of the photosensor array 63R is obtained. The same applies to the detection position HLl of the optical sensor array 63L.

  When the LP correction processing unit 652 detects that the horizontal line laser has a positional deviation or inclination from the reference position based on the obtained detection positions HLl and HRr, the LP correction processing unit 652 moves in a direction to eliminate the positional deviation or inclination. Feedback control is performed on the light source unit of the horizontal line laser via the actuator driving unit 653. The state of an example in which the horizontal line laser is displaced from the reference position is indicated by a wavy line in the figure. The same applies to the feedback control for the light source unit of the vertical line laser. Details of the feedback control will be described later with reference to FIG.

  6 and 7 are flowcharts (1) and (2) of the laser pointer control process according to the embodiment, and FIG. 6 determines a reference position to which position on each optical sensor array should be irradiated with the line laser. The laser pointer initialization process is shown. This process may be performed once at the time of system introduction and if necessary thereafter at regular intervals. This process is started in accordance with an instruction from the manual operation unit 656. In step S11, the dedicated phantom is scanned by the X-ray CT apparatus, and the dedicated phantom is positioned at the reference position of the X-ray CT apparatus (ISO center on the xy plane and a predetermined position in the z-axis direction) based on the reconstructed image. Match. An inset (a) in FIG. 2 shows a perspective view of the dedicated phantom. An example dedicated phantom is one in which three needle wires orthogonal to the xyz axis direction are housed in an acrylic case.

  Returning to FIG. 6, in step S12, the scanning gantry 10 is retracted, and the aim of each cross-line laser is adjusted by manual operation with respect to the reference position (intersection of each needle line) of the dedicated phantom after alignment. As a result, each laser projection unit 61T, 61L, 61R is initialized (calibrated) so as to be irradiated toward one point in the three-dimensional space serving as a reference of the medical system. In step S13, the dedicated phantom after initialization is removed, and the detection output of each photosensor array is read in a state where each crossline laser is incident on the corresponding photosensor unit. In step S14, the initial irradiation position (reference position) of the cross line laser is obtained based on the detection output of each photosensor array, and stored in the memory.

  FIG. 7 shows a laser pointer calibration process for maintaining the laser pointer device after the initialization in a correct aiming state. Each time the counter 651 scans (reads) the optical sensor array, this process is interrupted. In step S21, a substantial detection position HL is obtained based on the detection signal of the photosensor array 63L. In step S22, it is determined whether or not HL> HL1 (reference position stored in the initialization process). If HL> HL1, the displacement (force) FL applied to the laser projection unit 61L in step S23 is reduced by −1 (1 minute). Unit). If HL> HL1 is not satisfied, the process of step S23 is skipped. In step S24, it is determined whether or not HL <HLl. If HL <HLl, the displacement FL applied to the laser projection unit 61L in step S25 is incremented by 1 (unit). If HL <HL1, the process of step S25 is skipped.

  In step S26, the detection position HR is obtained based on the detection signal of the photosensor array 63R. In step S27, it is determined whether or not HR> HRr (reference position stored in the initialization process). If HR> HRr, the displacement FR applied to the laser projection unit 61L in step S28 is set to -1 (unit). If HR> HRr is not satisfied, step S28 is skipped. In step S29, it is determined whether or not HR <HRr. If HR <HRr, +1 (unit) is added to the displacement (force) FR applied to the laser projection unit 61L in step S30. If HR <HRr is not satisfied, the process of step S30 is skipped.

  In step S31, it is determined whether or not HL = HLl. If HL = HLl is not satisfied, the process is directly terminated. If HL = HLl, it is further determined in step S32 whether HR = HRr or not. If HR = HRr is not satisfied, the process is directly terminated. In the case of HR = HRr, the calibration is completed because the horizontal line laser is above the reference position (HL = HL1, HR = HRr) stored in advance. In step S33, the calibration process is locked, and the process exits. When the calibration process is locked, no further interruption occurs, and the light projection posture of the horizontal line laser light source unit of the laser light projection unit 61L is thereby fixed. If the cell pitch of the photosensor array is sufficiently smaller than the line laser width, some error may be allowed between the detection positions HL and HR and the reference positions HLl and HRr. The same applies to the calibration process of the vertical line laser.

  FIG. 3 shows a case in which CT imaging of a subject (lesion) is performed by the medical system after the initialization (or calibration) in order to accurately grasp the lesion position of the patient. The patient 1 mounted on the bed table 20 has its head directed toward the scanning gantry 10, and the top plate 21 is placed so that the mark placed on the position where the patient surface does not move coincides with the irradiation position of the cross line laser. Lift and transport. Inset (a) shows a perspective view of the patient being irradiated with a cross-line laser. In this state, the scanning gantry 10 is moved on the rail 41 and the lesion of the patient is imaged together with the mark. Thus, the position of the lesion from the system reference position where the patient marm is reflected can be accurately grasped.

FIG. 4 shows a case where radiation therapy using linac is performed on the lesion of the patient after the CT imaging. Although not shown, it is assumed that the X-ray irradiation position by the radiotherapy apparatus 200 is also calibrated in advance based on the reference position of the system. In this radiotherapy, a treatment plan such as a treatment X-ray irradiation position and irradiation dose is created by computer processing of the control console 60 based on the captured CT tomogram.

  On the other hand, the bed table 20 after the scanning gantry 10 is retracted is rotated 180 degrees around the rotation axis AT, so that the patient's head is directed toward the radiation therapy apparatus 200. Furthermore, the top plate 21 is moved up and down so that the mark on the patient's body surface coincides with the irradiation position of the cross line laser. In this state, the gantry 53 of the radiation therapy apparatus is moved to the patient side, and radiation therapy of the lesion is performed based on the created treatment plan. The irradiation of radiation is performed by a method of concentrating on a fixed position (lesion) from various directions while rotating the head 52.

  In the above-described embodiment, information on the reference position where the line laser crosses the optical sensor array is obtained and stored in the memory. However, the present invention is not limited to this. The generation pattern of each position information in which the detection signal = 1 of the optical sensor array is stored in the memory as it is, and a matching test is performed with the generation pattern of each position signal detected later, and a required ratio (for example, 80 to 90%) You may determine with a match by having matched above.

  Moreover, although the case where there was one laser pointer system was described in the said embodiment, it is not restricted to this. A plurality of laser pointer systems may be provided in one medical system.

  Moreover, although the preferred embodiment of the present invention has been described, it goes without saying that various changes in the configuration, control, processing, and combination of each part can be made without departing from the spirit of the present invention.

It is a figure (1) which shows the composition of the radiation therapy system by an embodiment. It is FIG. (2) which shows the structure of the radiotherapy system by embodiment. It is FIG. (3) which shows the structure of the radiotherapy system by embodiment. It is a figure (4) which shows the structure of the radiotherapy system by embodiment. It is a figure explaining the laser pointer apparatus by embodiment. It is a flowchart (1) of the laser pointer control process by embodiment. It is a flowchart (2) of the laser pointer control process by embodiment.

Explanation of symbols

10 Scanning gantry 20 Sleeper table 21 Top board (cradle)
DESCRIPTION OF SYMBOLS 30 Operation console 41 Rail 51 Collimator 52 Head 53 Gantry 60 Control console 61 Laser projection unit 62 Optical sensor unit 65 Pointer control part 100 X-ray CT apparatus 200 Radiation therapy apparatus

Claims (8)

A laser pointer device for positioning a subject in a medical system including a radiotherapy device,
A laser projection unit that is provided on a certain surface in a room that accommodates the radiation medical device and emits a cross-line laser;
An optical sensor unit that is provided on an opposite surface of the certain surface and receives a cross-line laser from the laser projection unit;
Control means for performing feedback control of the laser projection unit so that a cross-line laser from the laser projection unit is irradiated to a predetermined position on the optical sensor unit based on the detection output of the optical sensor unit. Laser pointer device. 2. The laser pointer device according to claim 1, wherein the laser projection unit is configured to be able to control the projection postures of the vertical line laser and the horizontal line laser constituting the cross line laser independently of each other. The optical sensor unit includes four optical sensor arrays provided so that the arrangement directions of the detection elements are orthogonal to the end line of the vertical line laser and the horizontal line laser constituting the cross line laser, respectively. The laser pointer device according to claim 2. The control means obtains a light receiving position on each photosensor array based on a detection signal received by a cross-line laser from a laser projecting unit directed in a predetermined direction in advance, and stores the obtained light receiving position as a reference position in a memory. 4. The laser pointer device according to claim 3, further comprising an initial setting means for storing the initial value. The control means includes a laser projection unit so that one end of the line laser is not irradiated to the reference position on the optical sensor array, so that the one end of the line laser is displaced by a certain amount in the direction of the reference position. 5. The laser pointer device according to claim 4, further comprising irradiation position calibration means for performing feedback control of the laser beam and alternately performing feedback control for both ends of the line laser. A laser pointer system comprising a plurality of laser pointer devices according to claim 1 in a room of a medical system comprising a radiation therapy device,
In the first laser pointer device including the laser projector unit on the ceiling and the optical sensor unit on the floor, and the opposing wall surfaces, a pair of each laser projector unit and the optical sensor unit facing each other faces each other. The second and third laser pointer devices are provided so that the cross-line lasers from the first to third laser pointer devices cross each other at one point in the room. Laser pointer system. A calibration method for the laser pointer device in a medical system comprising an X-ray CT device and the laser pointer device according to claim 3,
While imaging a dedicated phantom with needle lines arranged in the three-dimensional coordinate axis direction using an X-ray CT apparatus, the reference position where each needle line of the dedicated phantom is orthogonal to the reference position managed by the X-ray CT apparatus based on the reconstructed image Step
Adjusting the projection posture of the laser projection unit to irradiate the cross-line laser toward the reference position of the dedicated phantom after the alignment;
Receiving the cross-line laser from the adjusted laser projecting unit by a facing optical sensor array and storing the received position on each optical sensor array obtained based on the detection signal in a memory as a reference position; A calibration method for a laser pointer device, comprising: The method further comprises a step of feedback-controlling the light projection posture of the laser projection unit so that the cross-line laser from the laser projection unit after calibration is irradiated to a reference position on the facing optical sensor unit. The calibration method according to claim 7.

Images