EP4619095A1

EP4619095A1 - Simulator of rotational movements of a linear accelerator

Info

Publication number: EP4619095A1
Application number: EP23848483.6A
Authority: EP
Inventors: Pawel KUKULOWICZ; Adam MALKIEWICZ; Dariusz SZALKOWSKI; Mikolaj TARCHALSKI
Original assignee: Naviration Spolka Z Ograniczona Odpowiedzialnoscia
Current assignee: Naviration Spolka Z Ograniczona Odpowiedzialnoscia
Priority date: 2022-11-16
Filing date: 2023-11-15
Publication date: 2025-09-24
Also published as: PL442832A1; WO2024107073A1

Abstract

A simulator of rotational movements of a linear accelerator characterized by the fact that it has a rotation system with a rotation disc and a boom with a vision set (1). The rotation system has three arms, where the vertical arm (4) is placed perpendicular to the lower arm (2), and the horizontal arm (3) is located on the lower arm (2). The planes of the lower arm (2) and the horizontal arm (3) are parallel to each other, and the axes of the lower arm (2) and the horizontal arm (3) are perpendicular to each other. The rotation system has a base (5) with adjustable feet (6), a level (10) and a table (8). The rotation disc (11) of the vertical arm with the target rotation disc (12) is attached to the vertical arm (4). A target beam (13) is attached to the rotation disc of the vertical arm (11), parallel to the plane of the target rotation disc (12), on which there is at least one target in the form of a flat plate with at least two markers (16). The rotation system has a drive. The vision set has at least two cameras (23).

Description

Simulator of rotational movements of a linear accelerator

The subject of the invention is a device for simulating rotational movements of a linear accelerator. The invention can be used in radiotherapy, and in particular in radiosurgery, to simulate the rotational movements of the components of a linear accelerator, i.e. the accelerator arm, collimator and treatment table.

The axes of rotation of the arm, collimator, and treatment table are expected to remain constant throughout the rotation and intersect at a single point known as the isocenter. However, due to the high weight of the arm, the method of mounting the column of the treatment table and the load of the table on which the patient lies during irradiation, the current position of the individual axes of rotation depends on the angle of position of these elements and these axes do not have to intersect at one point. Changes in the position of the rotation axis may adversely affect the effects of radiotherapy, especially radiotherapy of small tumors with large single doses, i.e. radiosurgery.

Isocenter measurement is one of the geometric tests that must be performed for every medical accelerator used for radiotherapy, which is a legal requirement in Poland. It is also recommended by international scientific societies. According to metrological principles, each measuring device should be subject to operational verification at designated time intervals. In the case of the optical measuring system of the linear accelerator isocenter, there is no device in the state of the art that allows checking the correct operation of the device. Verification of the correctness of the measurement is performed manually, using graph paper, which causes significant difficulties because possibility to check the designated centers of the rotation axis performed in a plane set at any angle to the vertical plane with an accuracy of not less than 0.1 mm is expected. The need to measure rotational movement performed in an axis set at any angle relative to the vertical direction results from the range of rotational movements performed by the rotating elements of the medical accelerator for radiotherapy. Therefore, it is necessary to measure the isocenter (more precisely, the isocenter sphere, i.e. changes in the position of individual axes of rotation of the arm, collimator and treatment table) for each rotating component of the accelerator.

Currently, the measurement of the position of the mechanical isocenter is performed using very simple methods (millimeter paper, sharpened pencil), which do not ensure sufficiently high precision and the condition of measurement consistency required by law. Regardless of what measuring device would be used to verify the position of the isocenter, in accordance with metrological principles, it should be checked at designated time intervals. Such a device to verify the position of the isocenter for currently used tools and methods is not currently available. The subject of the invention solves the problem of verifying the measurement of the isocenter of a mechanical linear accelerator.

The simulator of rotational movements of a linear accelerator is characterized in that it has a rotation system with a rotation disc and a boom with a vision set. The rotation system has three arms, wherein the vertical arm is arranged perpendicularly to the lower arm and the horizontal arm is located on the lower arm. The planes of the lower arm and the horizontal arm are parallel to each other, and the axes of the lower arm and the horizontal arm are perpendicular to each other. The rotation system has a base with adjustable feet, a level and a table. A rotation disc of the vertical arm with a target rotation disc is attached to the vertical arm. A target beam is attached to the rotation disc of the vertical arm, parallel to the plane of the target rotation disc, on which there is at least one target in the form of a flat plate with at least two markers. The rotation system has a drive. The vision set has at least two cameras.

Preferably, the base is made of metal.

Preferably, the base has three adjustable feet.

Preferably, simulator has two targets.

Preferably, there are five markers on the target.

Preferably, the cameras in the video set are placed at a distance of 60 cm from each other.

Preferably, the boom has at least one foldable arm.

The invention is presented in the drawing, in which Fig. 1 shows the rotation system, Fig. 2 - an arm with a rotation disk, Fig. 3 - a rotation disk with a beam and attached targets, Fig. 4 - the whole invention.

The arm of the linear accelerator rotates in a vertical plane (perpendicular to the ground on which the accelerator is located), the treatment table in a horizontal plane (parallel to the ground plane), and the collimator in a plane set at any angle to the vertical plane. In an ideal situation, for a properly calibrated accelerator, these planes should intersect at one point. In a real situation, most often the planes are shifted from each other by a certain distance. The subject of the invention makes it possible to verify the correctness of determining the relative position of the rotation axis in relation to the specified initial position of the rotation axis. The position of the rotation axis should be understood as a straight line representing the rotation axis and the point designated as the intersection of the rotation axis and the flat plane of the simulator's rotation disk.

The simulator of rotational movements of the linear accelerator consists of a rotation system with rotation discs and a boom 1 with a vision set. In this example, the supporting structure of the rotation system is made of high-stiffness aluminum-steel elements with an electrolytic coating.

The rotation system consists of three arms: the lower arm 2, the horizontal arm 3 and the vertical arm 4. The rotation system is mounted on a square-shaped metal base 5, supported on three adjustable feet 6 enabling precise leveling of the system. A movable horizontal target arm 7 is attached to the vertical arm 4. The device includes a table 8 with a granite top 9 on which the simulator structure is placed. Before performing the verification measurement, the metal base 5 is leveled using a digital level 10. The electronic level ensures an accuracy of less than 0.05° During leveling, the digital level 10 is placed successively parallel to the two sides of the metal base 5, which allows the adjustable feet 6 to be positioned in such a way that so that the base 5 is placed horizontally. The level is determined with an accuracy of 0.1⁰ In this embodiment, the rotation system is made of aluminum profiles. Two rotation discs are attached to the end of the vertical arm 4, on the horizontal movable target arm 7, the rotation disc of the vertical arm 1 1 and the target rotation disc 12. The target rotation disc 12 is attached to the target beam 13, at the end of the horizontal target arm 7, perpendicular to the arm vertical 4, which ensures rotation in the vertical plane. The target rotation disc 12 is attached to the rotation disk of the vertical arm 11 , so that the plane of the rotation disk of the targets 12 can be set at any angle with respect to the plane parallel to the plane of the base 5.

After releasing the locking system, the target rotation disc 12 is rotated manually by a given angle. After completing this rotation, the operator blocks the possibility of further changing the angle of inclination of the target rotation disc 12. The target rotation disc 12 can rotate continuously around its own axis. The rotational movement is achieved thanks to an electric drive. The rotation speed is set by the operator. The rotation speed is determined by the operator before starting the rotation movement of the device. The rotational movement control allows the rotation disc of the targets 12 to be stopped in the angular position set by the operator. It is through the rotation of the rotation disk of the targets 12 that the rotation of the components of the linear accelerator is simulated - in the case of the arm in the vertical plane, and in the case of the table and collimator in the horizontal plane.

A target beam 13 is attached to the target rotation disc 12, parallel to its plane, in the embodiment made of high-stiffness aluminum-steel elements, with an electrolytic coating, with a square cross-section, enabling the target to be mounted in any position on the target beam 13. Two targets are attached to the target beam 13, the proximal target 14 and the distal target 15, with which the displacement is measured using an optical measurement system. A target is a flat, square-shaped board, measuring 10x10 cm in the embodiment, with five markers 16 on it. The dimensions of the targets are adjusted so that individual targets do not overlap. The targets are attached with screws to the target beam 13, which ensures their constant position relative to the target rotation disc 12 during rotation. The target beam 13 with the targets mounted on it is electronically controlled and can rotate at an angular speed, for example, from 0.1 revolution to 5 revolutions per minute. The proximal target 14 is placed so that the center of the target is located in relation to the axis of rotation of the target rotation disc 12 at a distance of no more than 1 cm, and the distal target 15 is placed at any point on the target beam 13, but so as not to obscure the proximal target 14.

The target beam 13 together with the proximal target 14 and the distal target 15 on the target rotation disc 12 is mounted on the rotation support 17. The target rotation disc 12 is rotated around the OT axis by means of an electric motor located inside the target rotation disc 12. On the vertical arm 4 there is also a pivotally mounted rotation support 17, rotatable around the Op axis, to the movable target arm 7. The movable target arm 7 is attached to the vertical arm 4 by means of a guide rail 18 of the vertical arm 4, which allows vertical movement along the OA axis. The vertical arm 4 is attached by means of a vertical support 19 and a guide rail 20 of the horizontal arm 3 to the horizontal arm 3, which guide rail 20 allows horizontal movement in the direction of the OB axis. The horizontal arm 3 is attached to the lower arm 2 by means of a guide rail 21 of the lower arm 2, which rail allows horizontal movement in the direction of the Oc axis.

The lower arm 2 is attached to a metal base 5, supported on adjustable feet 6. TheOp and Oy axes are perpendicular to each other, the Op and Coaxes are also perpendicular to each other, and the OA, OB and Oc axes are perpendicular to each other, creating a Cartesian coordinate system. Precise shifts take place in the directions of the OA, OB and Oc axes thanks to the use of precise optical rulers 22, with an accuracy of 0.01 mm in the example embodiment, thanks to which the proximal target 14 and the distal target 15 change their position in the Cartesian system by a given vector.

An electronically controlled rotary motor is located inside the system of the target rotation disc 12, enabling precise setting of the rotation angle of the target rotation disc in the full range of 360°. The reading of the rotation angle is a direct reading from the radial scale on the engine body and the digital scale in the engine control system.

The position of the arms 2, 3, 4 can be changed relative to the base 5 of the rotation system in three perpendicular axes: vertical, horizontal and in the axis perpendicular to the horizontal and vertical axes. The target rotation disc 12 is mounted on the rotation disk 1 1 of the vertical arm, which is a rotary joint that can change the angle of inclination of the target rotation disc 12 relative to the base of the entire rotation system, which enables the simulation of the position of the linear accelerator collimator between two extreme positions, horizontal and vertical. The rotation disc 11 of the vertical arm determines the angle of inclination of the target beam 13 for mounting targets relative to the vertical plane. The rotation of the target rotation disc 12 is electrically controlled and causes the targets to rotate. The range of longitudinal changes in the position of the target rotation disc 12 is +/-7.5 cm in the horizontal and vertical axes, relative to the centers of the horizontal and vertical axes. In the axis perpendicular to the horizontal and vertical axes, the range of changes is +/- 5.0 cm.

The vision set, for verification of which the simulator was built, consists of a system of two cameras 23 with lenses operating in a stereo system. In the embodiment, the cameras 23 are mounted at a distance of 60 cm from each other on a horizontal mounting beam 24, which is attached to a boom 1 having one foldable arm. The boom 1 allows changing the position of the cameras 23 in relation to the simulator of rotational movements of the linear accelerator.

The mounting beam 24 of the cameras 23 and the boom 1 are mounted on a mobile platform in which the workstation is located. The workstation consists of a PC device with peripheral devices, a UPS emergency power supply system and an electronic system responsible for powering and synchronizing the operation of cameras 23. Cameras 23 have a matrix of at least 5 Mpix and the size of a single pixel not exceeding 5 gm x 5 gm. The dynamics of the system allows image acquisition with a frequency of up to 22 Hz (mono image, 8 bit per pixel). The vision set allows to determine the position of the moving parts of the accelerator by measuring the position of the target using images recorded synchronously by two optical cameras 23. An integral part of the invention is software enabling detection in the image and tracking the position of the target. The software reads the synchronized signal from stereo cameras 23 and, by analyzing the images, determines the position of the marker.

The operation of the simulator of rotational movements of the linear accelerator is performed by determining the position of the isocenter (a point on the surface of the distal target 15 in its geometric center) in two known, determined with high accuracy, positions of the center of rotation of the target rotation disc 12. After setting up the simulator together with the mounted targets, a measurement of the center of the distal target 15 is performed. Then the position of the target rotation disc 12 is changed by moving the lower arm 2, the horizontal arm 3 and the target arm 7 by a set value. After changing the position, the position of the center of the distal target 15 is measured again. As a result, two results are obtained, one determining the actual change in the position of the isocenter and the other determining the same value determined using the optical measurement system. The measurement of the position of the rotation isocenter can be repeated many times, for different positions of the target rotation disc 12, both for rotations in the vertical plane, which corresponds to the rotation of the accelerator arm, and in the horizontal plane, which corresponds to the rotation of the collimator and the accelerator treatment table. Measurement in these two planes exhausts the possible planes of rotation of the accelerator components.

The present invention enables the measurement of the current isocenter with high precision. The simulator of rotational movements of the linear accelerator ensures verification of the operation of the optical measurement system designed to determine the isocenter of the linear accelerator, i.e. the position of the center of rotation of the arm, collimator and treatment table. The subject of the invention makes it possible to introduce and simulate a change in the position of the isocenter of the linear accelerator in the range of 0100 mm with an accuracy of up to 2 pm.

Claims

1 . A simulator of rotational movements of a linear accelerator, characterized in that it has a rotation system with a rotation disc and a boom (1 ) with a vision set, wherein the rotation system has three arms, wherein the vertical arm (4) is arranged perpendicularly to the lower arm (2), and the horizontal arm (3) is located on the lower arm (2) and the planes of the lower arm (2) and the horizontal arm (3) are parallel to each other, and the axes of the lower arm (2) and the horizontal arm (3) are perpendicular to each other wherein the rotation system has a base (5) with adjustable feet (6), a level (10) and a table (8), wherein a rotation disc (11 ) of the vertical arm with a target rotation disc (12) is attached to the vertical arm (4), wherein a target beam (13) is attached to the rotation disc (11 ) of the vertical arm, parallel to the plane of the target rotation disc (12), on which there is at least one target in form of a flat plate with at least two markers (16) wherein the rotation system has a drive, wherein the vision set has at least two cameras (23).

2. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that the base (5) is made of metal.

3. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that the base (5) has three adjustable feet (6).

4. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that it has two targets.

5. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that there are five markers (16) on the target.

6. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that the cameras (23) in the video set are placed at a distance of 60 cm from each other.

7. Simulator of rotational movements of a linear accelerator according to claim 1 , characterized in that the boom (1 ) has at least one foldable arm.