A method, a radiation monitoring device, and a system

Abstract

The present invention relates to a method (200) of a control unit (108) of a radiation monitoring device (100) for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit (101, wherein the method (200) comprises: sampling (S10) a sensor signal from the sensor unit (101); storing (S20) the sampled sensor signal in a data buffer with length S; calculating (S30) a second derivative of the sampled sensor signal in the data buffer; determining (S40) if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer; calculating (S50) the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer, wherein the data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions; and sum (S60) the integrated value of the pulse IP to a delivered radiation dose

Description

[0001] A METHOD, A RADIATION MONITORING DEVICE, AND A SYSTEM

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to the field of monitoring radiation and more specifically to the field of monitoring radiation from a plurality of pulses. The present disclosure more particularly relates to a radiation monitoring device suitable for use in connection with a radiation therapy device, such as a linear accelerator (LINACC).

[0004] BACKGROUND

[0005] In modern radiation therapy, a radiation source in form of a linear accelerator is often employed for delivering a pulsed beam of radiation to a target region in a target body. The radiation therapy involves precise dose planning in order to achieve the desired effect in the target region. The precise position of the target region relative the radiation therapy device is of utmost importance in order to provide the desired dose to the target region. However, during radiation treatment it is desirable to minimize the dose delivered to tissue close to the target region. In some cases, it might be necessary to abort the treatment or change the angle of the radiation therapy device in order to protect vital tissue from radiation damages. In some cases, it would be advantageous to monitor the dose delivered to the region of treatment precisely. In some cases, it would be advantageous to monitor the received dose in vital tissue close to the target region. One example of such a situation is the radiation therapy for treating prostate cancer. In this type of therapy, it is of great importance to minimize the dose delivered to urethra.

[0006] The above discussed monitoring is within the art called in vivo dosimetry (ID). For example, in US2020376299A1 an ID device is disclosed.

[0007] Bloemen-van Gurp EJ, Murrer LH, Haanstra BK, van Gils FC, Dekker AL, Mijnheer BJ, Lambin P. In vivo dosimetry using a linear Mosfet-array dosimeter to determine the urethra dose in 1251 permanent prostate implants. Int J Radiat Oncol Biol Phys. 2009 Jan 1;73(1):314-21. doi: 10.1016 / j.ijrobp.2008.08.040. PMID: 19100925. In this article, an ID device using a linear MOSFET array is disclosed. Semiconductor diodes are commonly used for ID in various configurations. The practitioner faces many problems in real use of an ID device in a clinical setting. In real ID measurements, the signals from a semiconductor diode operable as a sensor in the ID system is hampered with noise and galvanic currents. The detection of a current generated in a semiconductor diode by the radiation emitted from the radiotherapy device proves to be very difficult in general and in particular in a diode subjected to a pulsed beam from a radiotherapy device comprising a linear accelerator (LINAC). It is generally acknowledged that the problem associated with small signals in bursts from a semiconductor diode in a noisy environment is problematic to solve using conventional filtering techniques.

[0008] It is therefore a large need for an improved device and a system for precise characterization and measurement of a signal from a diode for dosimetry purposes, and especially for ID.

[0009] SUMMARY

[0010] An object of the present disclosure is to provide a radiation monitoring device which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and to provide an improved method.

[0011] This object is obtained by a method of a control unit of a radiation monitoring device for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit. The method comprises sampling a sensor signal from the sensor unit, storing the sampled sensor signal in a data buffer with length S, calculating a second derivative of the sampled sensor signal in the data buffer, determining if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer, calculating the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer. The data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions, and sum the integrated value of the pulse IP to a delivered radiation dose. The object is also obtained by a radiation monitoring device for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit. The radiation monitoring device comprises a sensor unit operable to detect the radiation dose and to generate a sensor signal indicative of the detected radiation dose, a control unit comprising a sampling unit arranged to sample the sensor signal, a data buffer with length S arranged to store the sampled sensor signal, a pulse detector unit operable to calculate a second derivative of the stored sampled sensor signal. The pulse detector unit is further operable to determine if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer, an integration unit operable to calculate the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer, a sum unit arranged to sum the integrated value of the pulse IP to a delivered radiation dose buffer. The data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions. The control unit is configured to execute the method according to embodiments.

[0012] The above method and device provides a robust way to calculate the delivered radiation dose to the target body, while avoiding noise due to galvanic currents and other sources.

[0013] The above method and device is especially useful if varying bias exists on the sensor signal.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing will be apparent from the following more particular description of the example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

[0016] Figure 1 is a schematic block drawing of a radiation monitoring system according to one embodiment of the present invention.

[0017] Figure 2 is flow diagram illustrating a method for a radiation monitoring system according to one embodiment of the present invention. Figure 3 is a schematic drawing of a target body and a radiation monitoring system according to one embodiment of the present invention.

[0018] Figure 4 shows an exemplary hardware implementation of a control unit shown in Figure 1.

[0019] DETAILED DESCRIPTION

[0020] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The apparatus and method disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0021] The terminology used herein is for the purpose of describing particular aspects of the disclosure only, and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0022] Some of the example embodiments presented herein are directed towards a radiation monitoring system for In-vivo dosimetry (ID). As part of the development of the example embodiments presented herein, a problem will first be identified and discussed. In-vivo dosimetry (ID) may be of great importance in many applications of radiotherapy. However, the small size of a radiation sensor suitable for ID makes it hard to achieve a good signal-to- noise ratio and often the signal from the sensor is affected by a galvanic voltages and floating DC voltages. Conventionally, the signal processing is performed by amplifying the sensor signal and filter the signal before digital signal processing. This proves to be very difficult and too much filtering may destroy some information from the signal of the sensor.

[0023] The present inventors realized that these problems might be minimized or even eliminated by understanding that the radiation therapy linear accelerator delivers the dose to the target body in pulse trains with specific duration and duty cycle. By storing samples of the signal in a buffer and use, the second derivative of the sampled signal to determine if the buffer contains a valid pulse a much more reliable method and system for ID is obtained. Furthermore, the present inventors realized that by dividing the buffer into at least two partitions. One partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions. This proves to be a very efficient way to remove a varying bias of the signal. Instead of having to resort to elaborate filtering a simple subtraction of the partitions removes the bias without distorting the signal.

[0024] Now with reference made to figure 1 in which a radiation monitoring device, generally designated 100, for determining a delivered radiation dose from a plurality of radiation pulses 301 sensed by a sensor unit 101 is disclosed.

[0025] The radiation monitoring device 100 comprises a sensor unit 101 operable to detect the radiation dose and to generate a sensor signal indicative of the detected radiation dose, a control unit 108 comprising a sampling unit 103 arranged to sample the sensor signal, a data buffer 104 with length S arranged to store the sampled sensor signal, a pulse detector unit 107 operable to calculate a second derivative of the stored sampled sensor signal. The pulse detector unit 107 is further operable to determine if a valid pulse is stored in the data buffer 104 based on the calculated second derivative of the sampled sensor signal in the data buffer, an integration unit 105 operable to calculate the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer, a sum unit 106 arranged to sum the integrated value of the pulse IP to a delivered radiation dose buffer. The data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions. The control unit 108 is configured to execute the method according to embodiments disclosed herein.

[0026] The sampling unit 103 samples the sensor signal with a sampling speed such that the buffer is filled with streaming data. After each sample is stored in the buffer, the pulse detection unit calculates the second derivative of the sampled signal in the buffer.

[0027] The pulse detector unit may further be operable to determine if a valid pulse is stored in the data buffer if all of the following conditions are fulfilled: a maximum value of the second derivative of the sensor signal is above a first threshold, and the second derivative of the sensor signal is below a second threshold at a first position in the data buffer before the maximum value of the second derivative of the sensor signal; and the second derivative of the sensor signal is below a third threshold at a second position in the data buffer after the maximum value of the second derivative of the sensor signal.

[0028] The maximum value of the second derivative may be centered in the data buffer.

[0029] The data buffer may be divided into a first partition, Pl, of a first length, a second partition, P2, of a second length, and a third partition, P3, of a third length, and when the second partition contains a valid pulse, the integrated value of the pulse IP is calculated as: IP =EP2-EP1-EP3, where EPn is the sum of all measurements in the n'th partition.

[0030] The sum of the first length and the third length may be equal to the second length. This way the calculation of the integrated value becomes a simple subtraction. Furthermore, the first length may be equal to the third length. This allows a fast calculation of the integrated value IP of the pulse in the buffer.

[0031] The pulse detector unit may also comprise an input 110 operable to receive a signal from the radiation therapy device indicative of a radiation pulse. This way an extra safeguard against erroneous triggering of the pulse detection is provided.

[0032] The control unit may further comprise a pulse timer 109 being operable to determine the time between valid pulses, and discard valid pulses from being added to the delivered radiation dose, if the time between valid pulses is outside a valid pulse interval. This way the pulse detection unit may be operable only during activation of the beam of the radiation therapy device.

[0033] In some cases, the control unit 108 may further comprise a matching circuit 102 operable to adjust the sensor signal, which comprises stretching the sensor signal by means of a low pass filter. Since the radiation therapy device often delivers pulses with a duration of 100 microseconds it might be useful to extend the pulse such that more samples covers the pulse.

[0034] The sensor unit may comprise a diode arranged to detect the radiation dose. The diode arranged to detect the radiation dose may preferably be a pin-diode. In one embodiment, the sensor unit comprises a plurality of pin-diodes arranged on a small printed circuit board.

[0035] Now, with reference made to figure 2 which discloses in a flowchart a method 200 of a control unit 108 of a radiation monitoring device 100 for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit 101. The method 200 comprises:

[0036] S10: Sampling a sensor signal from the sensor unit 101.

[0037] S20: Storing the sampled sensor signal in a data buffer with length S;

[0038] S30: Calculating a second derivative of the sampled sensor signal in the data buffer;

[0039] S40: Determining if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer;

[0040] S50: Calculating S50 the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer. The data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse. The integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions.

[0041] S60: Sum the integrated value of the pulse IP to a delivered radiation dose.

[0042] Optionally, the maximum value of the second derivative may be centered in the data buffer.

[0043] The data buffer may be divided into a first partion, Pl, of a first length, a second partition, P2, of a second length, and a third partition, P3, of a third length, and when the second partition contains a valid pulse, the integrated value of the pulse IP is calculated as: IP =£P2- 2P1-SP3, where £Pn is the sum of all measurements in the n'th partition.

[0044] The sum of the first length and the third length may be equal to the second length. The first length may be equal to the third length.

[0045] Optionally, the step of determining if a valid pulse is stored in the data buffer may further comprise receiving a signal from the radiation therapy device indicative of a radiation pulse. This way an additional safeguard against accidental triggering of the pulse detection is provided.

[0046] Optionally, the method further comprises determining the time between valid pulses, and discard valid pulses from being added to the delivered radiation dose, if the time between valid pulses is outside a valid pulse interval. This way an additional safeguard against accidental triggering of the pulse detection is provided.

[0047] Optionally, in some cases where the sampling speed of the sampling unit is not sufficient in order to capture enough samples of the sampled signal in the buffer, the method further comprises adjusting the sensor signal, which comprises stretching the sensor signal by means of a low pass filter.

[0048] Now with reference made to Figure 3 in which a radiation monitoring system, generally designated 310, is disclosed. The radiation monitoring system is provided for determining the delivered radiation dose to a target body 302 from a radiation therapy device 300 which provides a radiation dose in a plurality of pulses 301, wherein said radiation monitoring system 310 comprises a radiation monitoring device 100 according to embodiments disclosed herein.

[0049] The body 302 receives a beam 301 of pulsed radiation from a LINACC 300. A sensor unit 101 is arranged within the body 302 and is electrically connected to the control unit 108 with a cable. In this embodiment, the sensor unit comprises two pin diodes for sensing the pulsed radiation and for determining the delivered dose to the body 302. A matching circuit may be arranged within the sensor unit or within the control unit 108. The control unit 108 samples the signal from the LINACC and stores the sampled signal in the buffer. The control unit comprises a pulse detector, which is configured to calculate the second derivative of the sampled signal and to detect if a pulse is stored in the buffer according to the method disclosed herein.

[0050] Figure 4 shows an exemplary implementation of the control unit 108, in programmable signal processing hardware. The signal processing apparatus 400 shown in Fig. 4 comprises an input / output (I / O) section 410 for receiving the sensor signal and transmitting the determined delivered radiation dose. The signal processing apparatus 400 further comprises a processor 420, a working memory 430 and an instruction store 440 storing computer-readable instructions which, when executed by the processor 420, cause the processor 420 to perform the processing operations hereinafter described to control a radiation monitoring system. The instruction store 440 may comprise a ROM, which is pre- loaded with the computer-readable instructions. Alternatively, the instruction store 440 may comprise a RAM or similar type of memory, and the computer readable instructions can be input thereto from a computer program product, such as a computer-readable storage medium 450 such as a CD-ROM, etc. or a computer-readable signal 460 carrying the computer-readable instructions.

[0051] In the present embodiment, the combination 470 of the hardware components shown in Figure 4, comprising the processor 420, the working memory 430 and the instruction store 440, is configured to implement the functionality of the aforementioned control unit, which have been described in detail with reference made to Fig. 1

[0052] The disclosure relates to method of a control unit of a radiation monitoring device for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit comprises: sampling a sensor signal from the sensor unit the sampled sensor signal in a data buffer with length S; calculating a second derivative of the sampled sensor signal in the data buffer; determining if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer, calculating the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer, wherein the data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions; and sum the integrated value of the pulse IP to a delivered radiation dose.

[0053] According to some embodiments, the step of determining if a valid pulse is stored in the data buffer comprises determining that a valid pulse is stored in the data buffer if: a maximum value of the second derivative of the sensor signal is above a first threshold; and the second derivative of the sensor signal is below a second threshold at a first position in the data buffer before the maximum value of the second derivative of the sensor signal; and the second derivative of the sensor signal is below a third threshold at a second position in the data buffer after the maximum value of the second derivative of the sensor signal. According to some embodiments, the maximum value of the second derivative is centered in the data buffer.

[0054] According to some embodiments, the data buffer is divided into a first partion, Pl, of a first length, a second partition, P2, of a second length, and a third partition, P3, of a third length, and when the second partition contains a valid pulse, the integrated value of the pulse IP is calculated as: IP =£ P2-SP1-2P3, where SPn is the sum of all measurements in the n'th partition.

[0055] According to some embodiments, the sum of the first length and the third length is equal to the second length.

[0056] According to some embodiments, the first length is equal to the third length.

[0057] According to some embodiments, the step of determining if a valid pulse is stored in the data buffer further comprises receiving a signal from a further sensor indicative of a radiation pulse.

[0058] According to some embodiments, the method further comprises: determining the time between valid pulses; discard valid pulses from being added to the delivered radiation dose, if the time between valid pulses is outside a valid pulse interval.

[0059] According to some embodiments, the method further comprises adjusting the sensor signal, which comprises stretching the sensor signal by means of a low pass filter.

[0060] The present disclosure also relates to a radiation monitoring device for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit, wherein said radiation monitoring device comprises a sensor unit operable to detect the radiation dose in a target body and to generate a sensor signal indicative of the detected radiation dose, a control unit comprising: a sampling unit arranged to sample the sensor signal; a data buffer with length S arranged to store the sampled sensor signal; a pulse detector unit operable to calculate a second derivative of the stored sampled sensor signal; wherein the pulse detector unit is further operable to determine if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer; an integration unit operable to calculate the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer; a sum unit arranged to sum the integrated value of the pulse IP to a delivered radiation dose buffer, wherein the data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions; and wherein the control unit is configured to execute the method according to embodiments.

[0061] According to some embodiments, the sensor unit comprises a diode arranged to detect the radiation dose.

[0062] According to some embodiments, the diode arranged to detect the radiation dose is a pin-diode.

[0063] The disclosure relates to a radiation monitoring system for determining the delivered radiation dose to a target body from a radiation therapy device which provides a radiation dose in a plurality of pulses comprises a radiation monitoring device according to embodiments.

[0064] The disclosure relates to a computer program comprising computer-readable instructions which, when executed by a processor to perform the method according to embodiments.

[0065] The disclosure relates to a computer readable storage medium storing the computer program.

Claims

CLAIMS1. A method (200) of a control unit (108) of a radiation monitoring device (100) for determining a delivered radiation dose from a plurality of radiation pulses sensed by a sensor unit (101), wherein the method (200) comprises: sampling (S10) a sensor signal from the sensor unit (101); storing (S20) the sampled sensor signal in a data buffer with length S; calculating (S30) a second derivative of the sampled sensor signal in the data buffer; determining (S40) if a valid pulse is stored in the data buffer based on the calculated second derivative of the sampled sensor signal in the data buffer; calculating (S50) the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer, wherein the data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions; and sum (S60) the integrated value of the pulse IP to a delivered radiation dose.

2. The method according to claim 1, wherein the step of determining (S30) if a valid pulse is stored in the data buffer comprises determining that a valid pulse is stored in the data buffer if: a maximum value of the second derivative of the sensor signal is above a first threshold; and the second derivative of the sensor signal is below a second threshold at a first position in the data buffer before the maximum value of the second derivative of the sensor signal; and the second derivative of the sensor signal is below a third threshold at a second position in the data buffer after the maximum value of the second derivative of the sensor signal.

3. The method according to claim 2, wherein the maximum value of the second derivative is centered in the data buffer.

4. The method according to any one of the preceding claims, wherein the data buffer is divided into a first partion, Pl, of a first length, a second partition, P2, of a second length, and a third partition, P3, of a third length, and when the second partition contains a valid pulse, the integrated value of the pulse IP is calculated as: IP =2 P2-SP1-SP3, where SPn is the sum of all measurements in the n'th partition.

5. The method according to claim 4, wherein the sum of the first length and the third length is equal to the second length.

6. The method according to claim 4 or 5, wherein the first length is equal to the third length.

7. The method according to any one of the preceding claims, wherein the step of determining if a valid pulse is stored in the data buffer further comprises: receiving a signal from a further sensor indicative of a radiation pulse.

8. The method according to any one of the preceding claims, wherein the method further comprises: determining the time between valid pulses; discard valid pulses from being added to the delivered radiation dose, if the time between valid pulses is outside a valid pulse interval.

9. The method according to any one of the preceding claims, wherein the method further comprises adjusting the sensor signal, which comprises stretching the sensor signal by means of a low pass filter.

10. A radiation monitoring device (100) for determining a delivered radiation dose from a plurality of radiation pulses (301) sensed by a sensor unit (101), wherein said radiation monitoring device (100) comprises: a sensor unit (101) operable to detect the radiation dose and to generate a sensor signal indicative of the detected radiation dose; a control unit (108) comprising:a sampling unit (103) arranged to sample the sensor signal; a data buffer (104) with length S arranged to store the sampled sensor signal; a pulse detector unit (107) operable to calculate a second derivative of the stored sampled sensor signal; wherein the pulse detector unit (107) is further operable to determine if a valid pulse is stored in the data buffer (104) based on the calculated second derivative of the sampled sensor signal in the data buffer; an integration unit (105) operable to calculate the integrated value of the pulse, IP, in the buffer, upon determining that a valid pulse is stored in the data buffer; a sum unit (106) arranged to sum the integrated value of the pulse IP to a delivered radiation dose buffer, wherein the data buffer comprises at least two partitions, one partition for storing the valid pulse and the other partition for storing the sensor signal without the valid pulse, wherein the integrated value of the pulse, IP, in the buffer is calculated as the difference between these at least two partitions;; and wherein the control unit (108) is configured to execute the method according to any one of claims 1 to 9.

11. The radiation monitoring device (100) according to claim 10, wherein the sensor unit (101) comprises a diode arranged to detect the radiation dose.

12. The radiation monitoring device (100) according to claim 11, wherein the diode arranged to detect the radiation dose is a pin-diode.

13. A radiation monitoring system (310) for determining the delivered radiation dose to a target body (302) from a radiation therapy device (300) which provides a radiation dose in a plurality of pulses (301), wherein said radiation monitoring system (310) comprises a radiation monitoring device (100) according to any one of claims 10 to 12.

14. A computer program comprising computer-readable instructions which, when executed by a processor (420), cause the processor (420) to perform the method according to any of the claims 1 to 9.

15. A computer readable storage medium (440) storing the computer program of claim

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