FI79458B - OVER ANCHORING FOER STYRNING AV EN BEHANDLINGSANORDNING. - Google Patents

Description

1 79458

Method and apparatus for controlling a treatment device

The invention relates to a method and an apparatus for controlling a treatment device, more particularly to a method and an apparatus for eliminating an error caused by a patient's movement, for example a breathing movement, in a treatment situation. The method generates a mark on the patient's treatment area, and monitors the current position of the mark by continuously determining the position coordinates of the mark.

In radiotherapy, involuntary movements of the patient interfere with the relevance of the treatment, i.e., the movements of the patient cause the treatment not to hit exactly the desired target, e.g., a tumor. Various fixation systems have been used to prevent such unintentional movements, such as, for example, gypsum or polyurethane molds, which aim to keep the position of the patient stable. Despite the arrangements, all movements of the patient, e.g. the movement cannot be deleted. In addition to external movement, 20 breaths involve movement of internal organs in the thoracic and diaphragmatic region. Due to this, the amount and quality of the medium through which the treatment beam passes to its target (e.g. a tumor) varies, thus the amount of the radiation dose in question. area varies. Due to the movement of the subject, 25 unnecessarily healthy tissue around it is also destroyed.

The above-mentioned problems are not only related to radiotherapy, but the movement also causes an error in, for example, isotope and magnetic resonance imaging (NMR). In isotope imaging, the internal organs act as radiation sources, creating inaccuracies in the images. In magnetic resonance imaging (NMR), motion similarly causes motion blur in images.

It is therefore an object of the present invention to overcome the above-mentioned disadvantages of patient movement and to provide a method and apparatus in which errors in treatment or imaging caused in particular by respiratory movement can be eliminated. This is achieved by the method according to the invention by giving the treatment device a gating signal for its use when the location coordinates correspond to predetermined reference coordinates within the given limits. The apparatus according to the invention, in turn, is characterized by the features described in the characterizing part of claim 5. Thus, when referring in this connection to a treatment device, it refers not only to, for example, a radiotherapy device, but also to an imaging device or other similar device, the use of which causes an error in the patient's movement and can be triggered sufficiently quickly, e.g.

The basic idea according to the invention is thus to "stop" the movement, e.g. breathing movement, tremor, etc., so that the treatment or imaging is carried out periodically at the same stage of movement, whereby e.g. in the case of radiotherapy the position of the treatment object can be determined in advance.

According to the invention, the apparatus can also be used to identify a patient by means of the shape of the mark.

Above all, the arrangement according to the invention achieves more precise accuracy and better dosing accuracy in radiotherapy. In isotope and magnetic resonance imaging, image accuracy can be improved because inaccuracies caused by breathing motion are eliminated.

The mark to be formed on the patient's treatment area is, for example, a light line provided by a light source, such as a laser, the instantaneous position of which is monitored by means of an image recognition device, e.g. a video camera. Such an arrangement provides several additional benefits. The light line can easily detect the current stage of the breathing movement and identify the patient, because the current location and shape of the light line 35 depends on 3 79458 patients, for example the patient's breathing pattern. By using the above-mentioned combination of the image recognition device and the light source, the respective coordinates of the light line can be simply determined, so that they can be utilized in further processing. The video signal of the camcorder can be input directly to the TV monitor and track the position of the light line. According to a preferred embodiment of the invention, the x-coordinates of the light line are determined for each line-10 of every other half-frame of the video signal, wherein the sequence number of the line in said half-frame corresponds to the y-coordinate.

Other advantages of the invention will be explained in the following more detailed description, in which the invention is explained with reference to Example 15 according to the accompanying drawings, in which Figure 1 shows partly in perspective and partly in block diagram form the apparatus according to the invention, Figure 2 shows in more detail the digital unit 20 and Figure 1. Fig. 3 illustrates the logical operations performed by the central unit on the basis of which the gating signal is applied to the treatment device.

In Fig. 1, the patient 1 lies on a treatment table 2, next to which there is a treatment device 3 schematically shown, which can be, for example, a radiation treatment or imaging device, as mentioned above. The HeNe laser 11a 4 provides a light line 5 in the area of the patient's chest and diaphragm. To provide a planar beam, the laser has a cylindrical lens 6. The typical length of the light line 30 is about 25 cm. The light line 5 is monitored by means of a video camera 7 which is at a certain angle α with respect to the laser 5. The camera has a filter 8, which transmits only radiation having a laser wavelength, whereby only a light line 5 is shown on the monitor 8 connected to the camera.

4 79458 newvidicon type cameras. Figure 1 does not show the mounting of the laser 4 and the camera 7 for the sake of clarity. This can, of course, be done in several ways. The video signal is fed from the camera not only to the monitor 8 but also to the actual signal processing unit 5, where the first stage is the digitizing unit 9. In the digitizing unit, the current position of the light line 5 is calculated, i.e. its location and shape are determined. The digitizing unit is connected to a central processing unit 10 which contains a program memory 10 (ROM) 10a. The central processing unit 10 can be, for example, a Z 80 type processor.

The central unit 10 compares the position and shape of the light line 5 determined by the digitizing unit with a predetermined reference curve, and outputs a gating pulse GP which starts the treatment device when the patient's position has remained unchanged or the patient is back in a predetermined lie, i.e. the position and shape of the light line and the reference curve correspond to each other at predetermined limits. The reference curve is one measurement result made in advance for each patient. The description defines in advance the positions of the viscera with respect to the measurement curve. The rise time of the treatment device 3 is three orders of magnitude shorter than, for example, the time of the breathing cycle, so that the triggering performed by the central unit 10 is sufficiently fast.

A keyboard and display unit 11 is connected to the central unit 10. This unit handles the programming of the central unit and the setting of the operating mode of the hardware. The mode of operation may be the mode of operation described above, in which the treatment device 30 is gated based on the measurements and comparisons made, or it may be only a part of this, e.g., only measuring position 5 of the light line but not gating the treatment device 3. used to control the location of the patient 35. The operating mode can also be the reading of 5 79458 reference curves in the memory of the central unit. The tolerances used in the comparison are also entered from the keyboard. Tolerances are determined for each patient individually and depend, for example, on the extent of the breathing pad 5. The so-called normal breathers have a magnitude of 1 cm of breathing movement, while the diaphragm breathers have a magnitude of 2-3 cm.

Also connected to the central processing unit 10 is a microcomputer 12, which is used to document the measurement data. Figure 2 shows in more detail the structure of the digitizing unit 9. From the camera 7, a video signal VS is applied to the connector 13, which is connected to the second input of the comparator 14. A potentiometer 15 is connected to the second input, with which a reference voltage-15 te Vref is set on the comparator 14, to which the amplitude of the video signal VS is compared. The output of the comparator 14 is connected to a three-position switch 16 which is controlled by the output of the comparator. The output of the switch 16 is connected to the input 18 of the counter 17, whereby the switch 16 connects the output 18 of the counter 20 to either the output of the oscillator 19 or the divider 20 or to ground. These positions are marked with the numbers I, II and III, respectively. Connected to the reset input 21 of the counter 17 via the line 22 are the line sync pulses LSYNC of the video signal, which are also connected to the input 24 of the second counter 25 23. The reset input 25 of the counter 23 is always after 312 lines of the half image. The counter 17 is connected to the switch 27 and the counter 23 to the switch 28. The switches 27 and 28 are in two positions so that each counter 17 and 23 can be connected either to the memory 29 or the memory 29 can be connected via the bus circuit 30 and the bus 31 to the central processing unit 10. The counter 17 is 27 is connected to the data input 32 of the memory 29 and the counter 35 23 is respectively connected via a switch 28 to the address input 33 of the memory 29.

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The operation of the digitizing unit 9 will be explained in more detail below. At the beginning of each line of the video signal VS, the switch 16 is in position I, whereby the counter 17 starts counting the pulses coming from the oscillator 19 at the beginning of each line.

5 The frequency of the oscillator is 12 MHz. When the level of the video signal exceeds the reference voltage Vr.f set by the potentiometer 15, i.e. when the light line 5 starts to appear on that line, the switch 16 moves to position II, whereby the input 18 of the counter 17 is connected to the output of the divider 20 10. The divider 20 divides the frequency of the oscillator 19 by two. The counter 17 counts the pulses coming from the divider 20 as long as the level of the video signal exceeds the reference level Vref, that is, as long as the light line 5 appears on that line. When the light line 5 ceases to be visible on line 15, the switch 16 moves to position III, where the input 18 of the counter 17 is grounded. The reading reached by the counter 17 now corresponds to the position of the center of the light line 5 on that line. That is, the number of pulses received directly from the oscillator 19 corresponds to the position of the leading edge 20 of the light line on the line, and when the pulses received from the divider 20 are added during the duration of the light line, the reading corresponds to the center of the light line 5 on that line. This reading thus serves as the x-coordinate of the light line, and the y-coordinate is directly the sequence number of that line. When the switch 16 is engaged in the position III, the x-coordinate is stored in the memory 29 in a memory location whose address corresponds to the line sequence number calculated by the counter 23. At the beginning of the next line, the line synchronization pulse LSYNC from the terminal 22 resets the counter 17 and at the same time increases the reading of the counter 23 by one. At the same time, the switch 16 moves to position I, and the x-coordinate of the next line is calculated in the same manner as above, after which this pair of coordinates is again stored in memory. When all 312 lines of the half-image have been traversed, the coordinates of the 312 points are stored in the memory 29 so that the y-coordinate of each point is the sequence number (1-312) of the line 7 79458 and the x-coordinate corresponds to the counter 17 obtained on each line. readings. At the end of the half-picture, the counter 23 is reset by the pulse RES H fed through the terminal 26. During the next half-picture, no 5 measurements are made, but the coordinates are determined only with every other half-picture.

The CPU 10 compares the measurement results of each half image with a reference curve previously stored in the CPU's memory 10a. The desired number of reference points is selected from the reference curve 10, and for each reference point it is determined separately whether the coordinates of the light line 5 are within a certain tolerance from the coordinates of the reference point. In the following, this will be explained by way of example, assuming that eight reference points have been selected from the reference curve at approximately equal intervals so that they are the points of the reference curve corresponding to lines 15, 55, 95, 135, 175, 215, 255 and 295. Through the bus 31, the bus circuit 30, and the switches 28 and 27, the CPU retrieves the x-coordinate of each line from the eight memory locations corresponding to the respective sequence numbers 20 of the memory 29 and compares this with the x-coordinate of the corresponding line of the reference curve. Each comparison results in a binary value of 1 if the x-coordinate of that line is within the given tolerance of the x-coordinate of the corresponding line in the reference curve, and otherwise 0. The eight binary values thus obtained perform logical operations depending on whether the therapy device is gated or No.

Figure 3 illustrates logical operations with an example in which the comparison results corresponding to eight points are divided into four pairs, each of which is input to the inputs of the OR gate. The binary results of the comparisons corresponding to lines 15 and 55 are thus input to the inputs of OR gate 32a, the results of comparisons 35 corresponding to lines 95 and 135 to the inputs of OR gate 32b, and so on.

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The output of each OR gate is connected to the corresponding of AND gate 33; input. The output of the AND gate thus corresponds to the gating signal GP, i.e. the treatment device 3 is triggered if; The output of AND gate 33 has a logic value of 5 "1". With a logic value of "0", no trigger is performed. Thus, a trigger is performed only when at least one of each pair of points is within tolerance.

Figure 3 shows logical operations by means of wired logic for illustrative purposes only. In practice, these procedures are performed programmatically in the central processing unit 10, and the criteria on the basis of which the triggering is decided can be changed on a patient-by-patient basis depending on the movement characteristics of the treatment area.

The device according to the invention can also be used as such for positioning the patient. Since radiotherapy is given repeatedly, it is important that the patient is at the correct position on the examination table 2 for each treatment. By using the apparatus according to the invention so that the treatment device is not yet switched on, the gate signal 20 can be used to position the patient. In addition, the device can be used to ensure that the patient remains stationary for the time it takes for the caregiver to leave the treatment room and start the treatment device.

Although the invention has been described above with reference to the examples according to the accompanying drawings, it is clear that the invention is not limited thereto, but can be modified within the scope of the appended claims and the knowledge obvious to a person skilled in the art. Thus, the device 30 may include two cameras that observe the same line of light from different angles so that the areas they see partially overlap. This ensures that the patient does not move at an angle that would not be detected by the camera. Similarly, although in the above Example 35, the comparison was performed by comparing only the x-coordinates, the comparison could just as well be made in the direction of the rubber coordinate.

Instead of a normal video camera with a picture tube, it is also possible to use a so-called CCD camera.

5 matrix cameras, whereby digitization takes place in the normal manner described above. The above-mentioned cameras can also be replaced by a digital camera, in which case the output of the camera is the x, y-coordinates directly and the brightness z. In this case, the image is read into the computer's memory and identification is performed programmatically. Furthermore, the cameras can be replaced by a series of line element cameras, whereby one camera corresponds to a fixed value of x and the y-coordinate is obtained in the digitizing unit as described above by means of counters.

Claims (7)

10 79458 A method for eliminating an error caused by the movement of a patient (1) in a treatment situation, the method comprising: 5. forming a marker (5) in the treatment area of the patient (1), and - monitoring the current position of the marker (5) by continuously determining the position coordinates of the marker (5); 10. A gating signal (GP) is provided to the treatment device (3) to trigger it when the location coordinates correspond to predetermined reference coordinates within the given limits. A method according to claim 1, wherein a light line is used as the sign (5), characterized in that the x-coordinates of the light line (5) are determined on each line of every other half-frame of the video signal, the line sequence number corresponding to the y-coordinate. Method according to claim 2, characterized in that the desired number of reference points is selected from the reference curve to compare the determined position coordinates and the predetermined reference coordinates, and for each reference point *: 25 it is determined whether the coordinates of the light line (5) are within a certain tolerance. vertailukoordi-carbonates. Method according to claim 3, characterized in that at each reference point, operations are performed on the binary values representing the result of the determination, the result of which depends on whether a gating signal (GP) is given to start the treatment device (3). ► '5. An apparatus for eliminating 35 errors caused by the movement of a patient (1) in a treatment situation, the apparatus 11 79458 comprising - means (4, 6) for forming a mark (5) on the patient's treatment area, and - means (7, 8, 9) for the current position of the mark 5 for determining continuously, characterized in that it further comprises means (10) for actuating the treatment device (3) when the position of the marker (5) within the given limits corresponds to a predetermined reference position. Apparatus according to claim 5, characterized in that the means for starting the treatment device (3) comprise a central unit (10) connected to the digitizing unit (9), which compares the coordinates calculated by the digitizing unit to determine the starting time of the treatment device (3). Use of an apparatus according to claim 5 or 6 for identifying a patient by means of the shape of the mark (5). i2 79458