NL2026670B1 - System and assembly for measuring an ionizing radiation dose - Google Patents
System and assembly for measuring an ionizing radiation dose Download PDFInfo
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- NL2026670B1 NL2026670B1 NL2026670A NL2026670A NL2026670B1 NL 2026670 B1 NL2026670 B1 NL 2026670B1 NL 2026670 A NL2026670 A NL 2026670A NL 2026670 A NL2026670 A NL 2026670A NL 2026670 B1 NL2026670 B1 NL 2026670B1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
Abstract
The present invention relates to a system, and assembly of a measurement device, for measuring ionizing radiation. The system is characterized in that the system further comprises a first shell mounted to an outside of the housing during the first measurement and a second shell mounted to the outside of the housing during the second measurement, wherein the first shell and the second shell are configured such that attenuation levels of the ionizing radiation associated with paths from the radiation source to the sensor elements during the second measurement are substantially identical to attenuation levels of the ionizing radiation associated with those paths during the first measurement. By using the first shell during the first measurement and the second shell during the second measurement, an attenuation between the radiation source and a position inside the measurement device can be made substantially identical in the first and second measurement, thereby preventing the abovementioned measurement error. Therefore, the applied treatment plan can be more accurately and reliably verified using the correctly measured ionizing radiation dose. Additionally, the resolution of the measured treatment plan is increased without using a detector unit with a larger sensor density, which would otherwise result in higher costs.
Description
SYSTEM AND ASSEMBLY FOR MEASURING AN IONIZING RADIATION DOSE The present invention relates to a system, and an assembly of a measurement device, for measuring ionizing radiation.
Radiation therapy, or radiotherapy, commonly forms at least a part of cancer treatment, wherein malignant cells localized in a particular area of a subject are controlled or killed using ionizing radiation, such as x-rays. During a radiotherapy session, the subject is generally exposed to the ionizing radiation from a plurality of directions. In addition to treating malignant cells, regular cells inside the body, typically surrounding the area containing malignant cells, may also be damaged due to exposure to the ionizing radiation, which is an undesirable side-effect of the treatment. For this reason, a treatment plan is typically developed prior to the treatment, for example based on CT scan data of the subject acquired before the treatment, in which the delivered dose distribution of the ionizing radiation is determined. The treatment plan should ensure that the delivered dose is mostly concentrated in the localized area containing the malignant cells and has a steep gradient in areas outside of the localized area containing malignant cells to prevent excessive damage to healthy cells of the subject.
Treatment planning is generally performed on dedicated computers using specialized treatment planning software which determines how parts of the radiation system, such as an ionizing radiation source or a collimator, should be controlled. For example, the treatment plan may determine the required exposure and intensity of the ionizing radiation for each angle of incidence relative to the subject.
In order to validate if a calculated or predicted delivery dose distribution is correct, and in order to determine whether the radiation system is in fact capable of performing the generated treatment plan, the treatment plan is generally first applied to a measurement device, by exposing said measurement device to the radiation system similar to how the subject would be exposed to said radiation system. The measurement device is then configured to measure the dose distribution of the ionizing radiation delivered to the measurement device when a treatment plan under test is applied to the radiation system. Based on the measurement, the physical treatment plan, i.e., the dose distribution, observed by the measurement device is acquired.
A system for measuring ionizing radiation generally comprises a radiation system configured to emit ionizing radiation and comprising a stationary frame and a radiation source mounted to the stationary frame, a measurement device for measuring the emitted ionizing radiation, and a reading combining unit for obtaining measurements from the measurement device.
Devices for measuring an ionizing radiation dose are known from the art. An example of such a measurement device comprises a housing filled with a material configured to attenuate the ionizing radiation emitted by the radiation source, and a detector unit arranged inside the housing, the detector unit comprising a plurality of mutually fixedly positioned sensor elements that are each configured to measure a dose of ionizing radiation emitted by the radiation source.
In order to measure a dose distribution with sufficient accuracy, a high resolution is required. The resolution of the above measurement device is generally determined by the relative distance between sensor elements in the detector unit. Therefore, a straightforward approach for increasing the resolution of the measurement device is to physically increase the number of sensor elements in the detector unit. However, a disadvantage of this approach is that the cost of a measurement device comprising a detector unit with a high sensor density can be exceedingly high.
Furthermore, due to the physical size of the sensor elements in the detector unit, it may not be possible to increase the resolution using this approach, for example in the case that the dimensions of each of the sensor elements limit the maximum number of sensors which can physically be arranged in the detector unit.
Alternatively, the resolution can be artificially increased by performing a first measurement of ionizing radiation emitted from the radiation source using the measurement device positioned at a first position relative to the stationary frame to thereby acquire a first low resolution reading of the detector unit, and performing a second measurement of ionizing radiation emitted from the radiation source using the measurement device positioned at a second position relative to the stationary frame different from the first position to thereby acquire a second low resolution reading of the detector unit. The reading combining unit can then combine the low resolution reading corresponding to the first and second measurement into a high resolution reading of the detector unit. By displacing the measurement device in the second measurement relative to the first measurement, an artificial, combined measurement is created in which a number of measurement points is increased, thereby increasing the resolution of the measurement.
However, a problem that occurs with this approach is that a mismatch between the first measurement and the second measurement may occur, resulting in a measurement error during the second measurement, because attenuation levels of the ionizing radiation associated with paths from the radiation source to the sensor elements during the second measurement is different from attenuation levels of the ionizing radiation associated with those paths during the first measurement. In other words, the second low resolution reading acquired from the second measurement cannot be accurately combined with the first low resolution reading acquired from the first measurement, because the plurality of sensors, when the measurement device is in the second position during the second measurement, observe a different dose of ionizing radiation with respect to what actual sensor elements would have observed at those positions during the first measurement. This measurement error may result in the accuracy of the measured ionizing radiation dose being insufficient for verifying whether the treatment plan applied to the radiotherapy device matches the calculated or predicted treatment plan, or whether the desired treatment plan can be correctly executed by the radiotherapy device.
Fig. 1 is a cross-sectional view of a measurement device known from the art, in which the measurement error is illustrated. The measurement device 1 comprises a housing 2, and a planar first detector member 3A arranged inside housing 2. First detector member 3A comprises a plurality of sensor elements including a first sensor element. Although not explicitly shown in Fig. 1, housing 2 is filled with a material configured to mimic a human body, such that an attenuation of ionizing radiation inside the housing is similar to that in a human body. Furthermore, Fig. 1 shows aradiation source 5 and part of a stationary frame 5’ to which the radiation source is mounted, which are part of a radiation system.
In order to increase the resolution, a first and a second measurement are made at a respective first and second position of measurement device 1 relative to stationary frame 5’. In Fig. I, measurement device | and its components are shown at a first position relative to a stationary frame 5° using solid lines, and at a second position relative to stationary frame 5° using dashed lines. During the first and second measurement, each sensor element of the plurality of sensor elements is at a respective first and second sensor position, respectively. For example, at a first position of measurement device 1, the first sensor element is at a first sensor position 4A relative to stationary frame 5’, and at a second position of measurement device 1, the first sensor element is at a second sensor position 4B relative to stationary frame 5°. For simplicity, in Fig. 1, reference is made only to the first sensor element of first detector member 3A. It is noted that, since stationary frame 5° is stationary, various positions, for example positions of measurement device 1, first detector member 3A and first and second sensor position 4A and 4B, are defined in relation to stationary frame 5°.
Ideally, by combining the first and second low resolution reading, a high resolution reading is acquired in which detector unit readings are obtained from first sensor position 4A as well as second sensor position 4B, wherein, when, for example, the first sensor element is positioned at second sensor position 4B, the same ionizing radiation dose is measured at second sensor position 4B during the second measurement as a physical sensor element at said second sensor position 4B would have measured during the first measurement.
However, due to the difference in position of measurement device 1 relative to stationary frame 5° during the first and second measurement, the total attenuation of ionizing radiation between radiation source 5 and the first sensor element at the second sensor position 4B during the second measurement may be different from that of what a sensor element at a second position 4B during a first measurement would observe. For example, the path from second sensor position 4B to an edge of housing 2 in a direction towards radiation source 5 during the second measurement, i.e., to the housing represented with a dashed line, is different from a path from second sensor position 4B to an edge of housing 5 during the first measurement, i.e., to the housing represented with a solid line. In other words, as indicated in Fig. 1, line segment m-m’’, which is the desired path travelled by ionizing radiation through measurement device 1, is different from line segment m-my’, the actual path travelled by the ionizing radiation during the second measurement. As a result, a measurement error is made. In the particular example of Fig. 1, the measurement error is seen as the measured ionizing radiation dose at second sensor position 4B being lower than the true value, since the ionizing radiation travelling along the dashed line is not being attenuated while propagating on line segment m’-m’’ during the second measurement.
It is an object of the present invention to provide a system, and an assembly of a measurement device, in which the abovementioned problems do not or hardly occur.
This object is achieved with the measurement device according to claim 1, which is characterized in that the system farther comprises a first shell mounted to an outside of the housing during the first measurement and a second shell mounted to the outside of the housing during the second measurement, wherein the first shell and the second shell are configured such that attenuation levels of the ionizing radiation associated with a plurality of paths from the radiation source to the sensor elements during the second measurement are substantially identical to attenuation levels of the ionizing radiation associated with those paths during the first measurement.
It will be appreciated by a skilled person that attenuation of ionizing radiation may correspond to at least one of scattering of the ionizing radiation and absorption of the ionizing radiation, For example, attenuation levels may correspond to attenuation levels due to scattering and/or absorption of ionizing radiation. Furthermore, attenuation properties of a material may correspond to scattering properties and/or absorption properties of said material.
A path is defined herein as a line segment having a fixed length and direction. The length of each of the plurality of paths is defined by the relative distance between the radiation source and respective sensor elements of the detector unit during the second measurement. The plurality of paths extend from the radiation source towards respective sensor elements, which determines the direction of said plurality of paths. Then, attenuation levels associated with said paths during the second measurement are substantially equal to attenuation levels associated with those same paths, i.e., paths extending from the radiation source and having the same respective length and direction, during the first measurement.
By using the first shell during the first measurement and the second shell during the second measurement, an attenuation between the radiation source and a position inside the measurement device can be made substantially identical in the first and second measurement, thereby preventing the abovementioned measurement error. Therefore, the applied treatment plan can be more accurately and reliably verified using the correctly measured ionizing radiation dose. Additionally, the resolution of the measured treatment plan is increased without using a detector unit with a 5 larger sensor density, which would otherwise result in higher costs.
Each path among the plurality of paths may extend from a common first position, corresponding to a position of the radiation source during both the first and second measurement, to a respective second position, said respective second position corresponding to a position of a respective sensor element among the plurality of sensor elements during the second measurement and corresponding to a position that is in between adjacent sensor elements among the plurality of sensor elements during the first measurement.
The radiation source may be movably mounted to the stationary frame. Furthermore, the radiation source may be configured to move at least partially around the measurement device in a circomferential direction with respect to a longitudinal axis of the housing, which axis is parallel to a first direction. In other words, the radiation source may emit the ionizing radiation towards the measurement device in a direction perpendicular to the first direction.
The radiation source may be configured to be positioned at a plurality of different positions relative to the stationary frame, and the system may be configured to perform a respective first and second measurement for each respective position of the radiation source relative to the stationary frame.
Alternatively, during the first and second measurement, the radiation source may move at least partially around the measurement device. Such movement may be continuous or intermittent. Furthermore, during each of the first and second measurement, each sensor element may measure the combined ionizing radiation that is irradiated to that sensor element during the path of the radiation source around the measurement device. For example, each sensor element may integrate the ionizing radiation incident on said sensor element during the first and second measurement. The first shell and second shell are in this case configured such that for each position of the radiation source during the first and second measurement, attenuation levels of the ionizing radiation associated with a plurality of paths from the radiation source at that position to the sensor elements during the second measurement are substantially identical to attenuation levels of the ionizing radiation associated with those paths daring the first measurement.
The first shell and the second shell, when mounted on the outside of the housing during the first and second measurement, respectively, may be configured to surround the housing in a circumferential direction with respect to the longitudinal axis of the housing. In doing so, the measurement error is prevented regardless of the position of the radiation source relative to the measurement device.
The system may further comprise a movable platform onto which the measurement device can be arranged, wherein the movable platform is configured to move the measurement device relative to the stationary frame for positioning the measurement device in the first position or second position. Therefore, the measurement device can be easily and accurately moved to the first or second position.
The system may further comprise a first controller configured to control the movable platform and the radiation system, and a second controller for controlling the measurement device.
19 Using the first controller, the system can be controlled easily from, for example, a user terminal, or may even be controlled automatically.
The first controller may comprise a first sub-controller that is configured for controlling a motion of the radiation source relative to the stationary frame during the first measurement and the second measurement, and a second sub-controller for controlling the movable platform.
Alternatively, the first and second sub-controllers are embodied as separate units. Furthermore, the reading combining unit may be incorporated into the second controller or into the measurement device. In other embodiments, the reading combining unit is incorporated in or formed by an external device, such as a personal computer or laptop.
A first part of the plurality of sensor elements may be arranged in or on a substantially planar first detector member that extends in the first direction and a second direction different from the first direction.
The first and second position may differ only in the first direction, only in the second direction, or in both the first and second direction. In doing so, the resolution of the detector unit, more in particular the first detector member, can be increased in the first direction, in the second direction, or simultaneously in the first and second direction. The second direction may be perpendicular to the first direction.
A second part of the plurality of sensor elements may be arranged in or on a substantially planar second detector member that extends in the first direction and a third direction different from the first and second direction.
The first and second position may differ only in the third direction, only in the first and third direction, only in the second and third direction, or in the first, second, and third direction. In doing so, the resolution of the detector unit, more in particular the first and second detector member, can be increased in at least one of the first, second and third direction. The third direction may be perpendicular to the first and second direction.
The second detector member may comprise a first part and a second part, wherein the first part of the second detector member extends from the first detector member in the third direction, and wherein the second part of the second detector member extends in a direction opposite to the first part of the second detector member.
A cross-section of the housing, when viewed from the first direction, may have one of a rectangular shape, a rounded rectangular shape, a circular shape and an elliptical shape.
The system may be configured to perform a plurality of respective second measurements of ionizing radiation emitted from the radiation source using the measurement device positioned at respective second positions relative to the stationary frame and using respective second shells to thereby acquire respective second low resolution readings of the detector unit. The reading combining unit may be configured to combine the first low resolution reading and each respective second low resolution reading to acquire the high resolution reading of the detector unit. In doing so, the resolution can be increased in a plurality of directions. Furthermore, the resolution can be arbitrarily further increased in the same direction by performing a plurality of measurements in the same direction but at different respective second positions and using different respective second shells.
Each respective second position may differ from the first position in a different direction than the other second position(s). Additionally or alternatively, at least one respective second shell may differ from the other second shells.
The first and second shell may be made from a uniform material having identical attenuation properties for the ionizing radiation as the material arranged inside the housing. Furthermore, the first and second shell may be shaped such that attenuation levels of the ionizing radiation associated with paths from the radiation source to the sensor elements during the second measurement are substantially identical to the attenuation levels of the ionizing radiation associated with those paths during the first measurement. In other words, the thickness of the second shell with respect to the first shell along the circumference of the housing can be varied such that the attenuation levels corresponding to respective paths is identical in the first measurement and the second measurement(s). For example, the first shell may have a uniform thickness along its circumference, and the thickness of the first shell may be equal to or greater than a difference between the first and second position.
Alternatively, the first and second shell may have an identical and uniform thickness along their respective circumference, and a material density and/or material composition of the first and second shell along their circumference may be configured such that attenuation levels of the ionizing radiation associated with paths from the radiation source to the sensor elements during the second measurement are substantially identical to the attenuation levels of the ionizing radiation associated with those paths during the first measurement.
Each of the first shell and the second shell(s) may comprise a primary shell part and a secondary shell part that are configured to be fixedly connected to each other or to the housing using coupling means so as to form the first and second shell, respectively. In doing so, the production of the shells, as well as the process of mounting the shell to the housing, can be facilitated.
For example, the coupling means may comprise one of magnetic coupling means and mechanical coupling means. In a preferred embodiment, the coupling means are arranged at or near opposing ends of the measurement device. The coupling means can therefore be conveniently placed such that it does not affect the measurements or hardly so. Furthermore, in some embodiments, the primary and secondary shell parts of the first shell and the second shell(s) may be shell halves. However, the present invention is not limited thereto. For example, at least one of the first shell and the second shell(s) may comprise three or more shell parts which are configured to be fixedly connected to each other using coupling means to form the first and second shell.
At least one of the first shell, the second shell(s), and the material arranged inside the housing are made of a water-equivalent material suitable for mimicking a human body, such as poly-methyl methacrylate, ‘PMMA’, polystyrene, acrylonitrile butadiene styrene, ‘ABS’, Plastic Water™ or Solid Water“.
According to another aspect, an assembly is provided, comprising the measurement device, the first shell, and the second shell(s) as defined above.
According to another aspect, an assembly is provided, comprising the first shell and the second shell(s) as defined above.
Next, the present invention will be described with reference to the appended drawings, wherein: Fig. 1 is a cross-sectional view of a measurement device known in the art; Fig. 2 is a cross-sectional view of a measurement device according to an embodiment of the present invention; Figs. 3A and 3B are a cross-sectional view of a measurement device according to an embodiment of the present invention during a first and second measurement, respectively; Fig. 4 is a cross-sectional view of a measurement device according to another embodiment of the present invention; Figs. 5A and 5B are a cross-sectional view of a measurement device according to another embodiment of the present invention during a first and second measurement, respectively;
Fig. 6 is a cross-sectional view of a measurement device according to another embodiment of the present invention; Figs. 7A and 7B are a cross-sectional view of a measurement device according to another embodiment of the present invention during a second and third measurement, respectively; Figs. 8A and 8B are a cross-sectional view of a first and second shell according to an embodiment of the present invention; Fig. 9 is a cross-sectional view of a measurement device according to another embodiment of the present invention; and Fig 10 is a schematic representation of a system for measuring ionizing radiation according to an embodiment of the present invention.
Hereinafter, reference will be made to the appended drawings. It should be noted that identical reference signs may be used to refer to identical or similar components.
Fig. 2 shows a cross-sectional view, when viewed from the first direction, of measurement device 1. Measurement device 1 comprises housing 2 and planar first detector member 3A which comprises a plurality of sensor elements with a first sensor element, similarly to measurement device 1 in Fig. 1. However, Fig. 2 additionally shows a shell 6.
In Fig. 2, housing 2 of measurement device 1 is shown at a first position relative to stationary frame 5’ using a solid line, and at a second position relative to stationary frame 5’ using a dashed line. In Fig. 2, the second position differs from the first position in the second direction.
Furthermore, the first sensor element of first detector member 3A is indicated in first sensor position 4A relative to stationary frame 5° with a solid shape, and in second sensor position 4B relative to stationary frame 5° with a dashed shape. The first and second sensor position of an additional sensor element of first detector member 3A, respectively, is also shown in Fig. 2. Finally, a path travelled by ionizing radiation from radiation source 5 towards second sensor position 4B and a second sensor position of an additional sensor element of first detector member 3A is indicated with a dashed line.
With the addition of shell 6, the measurement error previously shown in Fig. 1 is prevented, since line segment n-n’ corresponding to the path travelled by ionizing radiation inside measurement device 1 towards second sensor position 4B is now identical, irrespective of whether measurement device 1 is placed at a first position or a second position relative to stationary frame 5’. In other words, shell 6 ensures that the attenuation of ionizing radiation between radiation source 5 and second sensor position 4B during the first and second measurement is identical.
In Fig. 2, the plurality of sensor elements in a cross-section of measurement device 1 are shown to be uniformly distributed along the second direction of first detector member 3A.
However, the present invention is not limited thereto. For example, a sensor density near a center of housing 2 may be larger than a sensor density away from the center of housing 2.
In a preferred embodiment, second sensor position 4B is spaced apart from first sensor position 4A by substantially half of a distance between adjacent sensor elements of first detector member 3A. Therefore, when the first and second measurements are combined, a high resolution reading of first detector member 3A is acquired in which the measurement points remain uniformly distributed along the second direction.
Figs. 3A and 3B show an example of how to acquire a first and second low resolution reading at a first and second position of measurement device 1, respectively, in accordance with Fig. 2. More in particular, Fig. 3A shows a configuration of measurement device 1 during a first measurement, and Fig. 3B shows a configuration of measurement device 1 during a second measurement. Furthermore, Figs. 3A and 3B both show paths travelled by ionizing radiation from radiation source 5 towards second sensor position 4B and an additional second sensor position of another sensor, said paths being indicated with dashed lines.
In Fig. 3A, housing 2 and first detector member 3A are at a first position relative to stationary frame 5°. Therefore, the first sensor element of first detector member 3A is at first sensor position 4A. During the first measurement, a first shell 7 comprising a first shell element 7’ is attached to an outside of housing 2. In this configuration, a first measurement of ionizing radiation is made. For example, the first measurement may include measuring an ionizing radiation dose from various positions of radiation source 5 relative to measurement device 1. More in particular, radiation source 5 may be configured to move around measurement device 1 in a circumferential direction during the first measurement so as to measure an ionizing radiation dose from a plurality of angles with respect to the cross-section of the housing. The movement of radiation source 5 may be executed in steps, measuring the ionizing radiation dose at each step, or may be continuously moved instead while performing the measurement.
In Fig. 3B, housing 2 and first detector member 3A are at a second position relative to radiation source 3. Therefore, the first sensor element of first detector member 3A is at second sensor position 4B. During the second measurement, a second shell 8 comprising a second shell element 8’ is attached to the outside of housing 2. The first measurement and the second measurement are performed in a similar manner, and therefore, a detailed description thereof is therefore omitted. After performing the first and second measurement, a first and second low resolution reading of first detector member 3A is acquired, respectively. The low resolution readings may be combined to acquire a high resolution reading of first detector member 3A.
First shell element 7’ and the second shell element 8’ are configured such that, for the first sensor element of first detector member 3A, an attenuation of the ionizing radiation between radiation source 5 and second sensor position 4B during the first measurement i.e., Fig. 3A, is substantially identical to an attenuation of the ionizing radiation between radiation source 5 and second sensor position 4B during the second measurement, i.e., Fig. 3B. In other words, if the attenuation of ionizing radiation inside housing 2 is uniform throughout housing 2, then first shell element 7° and second shell element 8’ are configured such that line segment a-a’ during the first measurement has the same length as line segment b-b’ during the second measurement. For example, as shown in Figs. 3A and 3B, this may be achieved by appropriately selecting the thickness of first shell element 7’ and second shell element 8’. Alternatively, the material density and/or material composition of the shells may be varied along the circumference of the cross- 19 section of housing 2. Then, matching the attenuation of the paths in the first and second measurement is achieved by appropriately providing the required material density and/or material composition of the shell elements. For a fixed position of radiation source 5, as illustrated in Figs. 3A and 3B, only first shell element 7° and second shell element 8’ are required to prevent the measurement error for the first sensor element at second sensor position 4B. In some embodiments, the desired attenuation properties for the first and second shell element 7’ and 8” can be acquired by appropriately selecting both the thickness of first and second shell element 7’ and 8’ as well as the material density and/or material composition of first and second shell element 7° and 8’.
First shell element 7’ and second shell element 8’ may provide the above function not just for the first sensor element, but instead for at least one other sensor element of first detector member 3A. In other words, first and second shell elements 7’ and 8’ must then be configured such that, for each sensor element of first detector member 3A, the attenuation of ionizing radiation between radiation source 5 and the second sensor position of each sensor element of first detector member 3A during the first measurement and the second measurement is substantially identical. As shown in Figs. 3A and 3B., first and second shell elements 7’ and 8’ are wide enough with respect to acircumference of housing 2 such that, additionally to line segment a-a’ having the same length as line segment b-b’, line segment c-c’ is has the same length as line segment d-d’. This concept may be further extended such that the measurement error for every sensor element of the plurality of sensor elements of first detector member 3A is entirely prevented. In other words, the shell elements need to extend wide enough along the circumference of housing 2 such that the measurement error is prevented for each sensor element.
Furthermore, radiation source 5 may be configured to move around measurement device | in circumferential direction. In that case, first and second shell elements 7’ and 8’ must extend across the entire circumference of the cross-section of housing 2. Alternatively, first and second shell 7 and 8 may comprise a plurality of first and second shell elements, respectively, which are configured to be fixedly connected to each other using coupling means in order to form first and second shell 7 and 8. When fixedly connected and mounted to housing 2, the plurality of first shell elements and the plurality of second shell elements completely surround housing 2, respectively. For example, first and second shell 7 and 8 may each comprise two shell elements, such that attaching first and second shell 7 and 8 during the first and second measurement, respectively, is facilitated.
Although first shell 7 is shown to have a uniform thickness around a circumference of the cross-section of housing 2, the present invention is not limited thereto. First shell 7 or second shell 8 may have any particular thickness, as long as the other of first shell 7 and second shell 8 is configured such that the attenuation of ionizing radiation on respective paths during the first and second measurement is identical, such that no mismatch occurs between the first and second measurement.
In Figs. 2, 3A and 3B, measurement device 1 is shown only at a first and second position relative to stationary frame 5°, such that the resolution of first detector member 3A in the second direction is increased. However, measurement device 1 may also be displaced in a first direction, that is, the direction from which measurement device 1 is viewed in Fig. 2, for performing another measurement in order to increase the resolution of first detector member 3A in the first direction as well.
Furthermore, the resolution of the combined measurements can be arbitrarily further increased by performing further measurements at further sensor positions in order to acquire further low resolution readings, which may then be combined to form a single high resolution reading. For example, additionally to the first and second measurement, a further second measurement may be performed at a further second position, requiring a further second shell for said measurement which corresponds to preventing a measurement error at the further second sensor position similarly to second shell 8 for the second measurement. For example, the mutual distance between first sensor position 4A, second sensor position 4B and the further second sensor position may be one third of the distance between adjacent sensor elements of first detector member 3A in the second direction. Thus, by combining the first, second and further second measurement, a high resolution reading of first detector member 3A is acquired in which the resolution of the measurement in the second direction is increased by a factor three with respect to the resolution of first detector member 3A. Similarly, the resolution can be further increased by performing additional further second measurements and changing the mutual distance between respective sensor positions accordingly.
Fig. 4 shows an alternative configuration of measurement device 1, in which said measurement device further comprises a second detector member 3B comprising a plurality of sensor elements. Second detector member 3B comprises a first and second part, wherein the first part extends from first detector member 3A in a third direction, and wherein the second part extends from first detector member 3A in an opposite direction with respect to the first part. Similarly to Fig. 2, housing 2 in Fig. 4 is shown in a first position relative to stationary frame 5° using a solid line, and in a second position relative to stationary frame 5° using a dashed line. The first sensor element of first detector member 3A is shown in first sensor position 4A using a solid line, and in second sensor position 4B using a dashed line. First detector member 3A may is similar to second detector member 3B. Therefore, a detailed description of second detector member 3B is omitted.
With the addition of second detector member 3B, measurements of ionizing radiation doses are also obtained in the third direction. In the embodiment of Fig. 4, the resolution of first and second detector member 3A and 3B can simultaneously be increased by performing first measurement from a first position of measurement device 1 relative to stationary frame 5°, and a second measurement at a second position of measurement device 1 relative to stationary frame 5°, wherein said second position differs from the first position in both the second and third direction.
Therefore, the first sensor element of first detector member 3A is at first sensor position 4A relative to stationary frame 5° during the first measurement and at second sensor position 4B relative to stationary frame 5’ during the second measurement. Again, shell 6 is used to prevent a measurement error due to mismatch between the positions of measurement device 1. The first and second measurement provide a first and second low resolution reading of the first and second detector member 3A and 3B. The low resolution readings are then combined to form a high resolution reading of first and second detector member 3A and 3B.
In a preferred embodiment, the distance between first sensor position 4A and second sensor position 4B in the second direction and in the third direction is equal to substantially half of the distance between adjacent sensor elements of the first and second detector member 3A and 3B, respectively.
Figs. 5A and 5B show an example of how to acquire a first and second low resolution reading at a first and second position of measurement device 1, respectively, in accordance with Fig. 4. Similarly to Fig. 3A and 3B, first shell 7 comprising first shell element 7’ is attached to housing 2 during the first measurement, and a second shell 9 comprising a second shell element 9’ is attached to housing 2 during the second measurement.
First shell element 7’ and the second shell element 9’ are configured such that, for the first sensor element of first detector member 3A, an attenuation of the ionizing radiation between radiation source 5 and second sensor position 4B during the first measurement i.e., Fig. 5A, is substantially identical to an attenuation of the ionizing radiation between radiation source 5 and second sensor position 4B during the second measurement, i.e., Fig. 5B. In other words, if the attenuation of ionizing radiation inside housing 2 is uniform throughout housing 2, then first shell element 7’ and second shell element 9’ are configured such that line segment e-e’ during the first measurement has the same length as line segment f-f’ during the second measurement.
Figs. 6, 7A and. 7B show an alternative approach for acquiring a high resolution reading of first and second detector members 3A and 3B. Instead of performing a second measurement at a second position which differs from the first position in the second and third direction, Fig. 6 shows a configuration in which a second measurement is performed at a second position which differs from the first position only in the second direction. Additionally, a third measurement is performed at a third position which differs from the first position only in the third direction. The low resolution readings resulting from the first through third measurement can then be combined to acquire a high resolution reading of first and second detector members 3A and 3B.
For clarity purposes, the position of housing 2 relative stationary frame 5° in the second and third position is omitted. During the first measurement, the first sensor element of first detector member 3A is at first sensor position 4A. During the second measurement, the first sensor element is at second position 4B, and during the third measurement, the first sensor element is at a third position 4C. Therefore, Fig. SA corresponds to the configuration of measurement device 1 during the first measurement, and Figs. 7A and 7B correspond to the configuration of measurement device 1 during the second and third measurement, respectively. Furthermore, during the second measurement, second shell 8 is mounted to the outside of housing 2, and during the third measurement, a third shell 10 is mounted to the outside of housing 2. By using each respective shell during each respective measurement, a measurement error at second sensor position 4B and third sensor position 4C is prevented.
In embodiments wherein measurement device 1 is symmetric about an axis parallel to the second direction as well as about an axis parallel to the third direction, third shell 10 may be identical to second shell 8. For example, during the third measurement, second shell 8 may be mounted to housing 2 of measurement device 1 and may be rotated by 90 degrees with respect to second shell 8 when mounted to housing 2 during the second measurement. In such embodiments, the resolution can be improved in the second and third direction while only requiring first shell 7 and second shell 8.
Although Figs. 2-7B show configurations in which the second position of measurement device 1 differs from the first position in the second direction and/or the third direction, the present invention is not limited thereto. The second position corresponding to the second measurement or the further second position(s) corresponding to further second measurements may, additionally or alternatively, differ from the first position in the first direction, such that a high resolution reading is obtained for which the resolution is improved in at least the first direction.
Figs. 8A shows a cross-section of a first and second shell element 7° and 7° of first shell 7, when viewed from the first direction. Similarly, Fig. 8B shows a cross-section of a first and second shell element 8’ and 8°" of second shell 8, when viewed from the first direction.
First and second shell element 7° and 7°” of first shell 7 are configured to be fixedly connected to each other using coupling means provided in said shell elements. For example, first shell element 7’ of first shell 7 comprises coupling means 11A and 11B provided at ends thereof in circumferential direction with respect to the housing of the measurement device. Similarly, second shell element 7°" comprises coupling means 12A and 12B provided at ends thereof in circumferential direction. Coupling means 13A and 13B of first shell element 8’ of second shell 8 and coupling means 14A and 14B of second shell element 8” of second shell 8 may similarly be arranged at respective ends of the shell elements in circumferential direction with respect to the housing of the measurement device.
The coupling means form pairs which are configured to couple to each other. For example, coupling means 11A is configured to couple to coupling means 12A, and coupling means 11B is configured to couple to coupling means 12B, such as to fixedly couple first shell element 7’ to second shell element 7°" to form first shell 7.
The coupling means may comprise magnetic coupling means, such as permanent magnets. Alternatively, the coupling means may comprise mechanical coupling means. For example, for each pair of coupling means, one of the pair of coupling means may comprise a protrusion, and another of the pair of coupling means may comprise a recess configured to receive the protrusion.
The coupling means of first and second shell element 7° and 7°” are preferably arranged at or near a first and/or second end of first and second shell element 7’ and 7°’ in the first direction.
The above description in relation to first shell 7 similarly applies to the second shell 8 and, if applicable, any of the third shell used during the third measurement or further shells used during further measurements.
Fig. 9 shows an alternative configuration of measurement device 1 wherein a cross-section of housing 2, when viewed from the first direction, has a rounded rectangular shape. Measurement device 1 of Fig. 9 similarly comprises housing 2, first detector member 3A arranged in housing 2 and comprising a plurality of sensor elements. Furthermore, shell 6 is mounted to an outside of housing 2 of measurement device 1. For example, a first shell is mounted to an outside of housing 2 during the first measurement and a second shell is mounted to the outside of housing 2 during the second measurement. Using the first and second shell, the measurement error is prevented in a similar fashion to the embodiments of Figs. 2-7B.
Fig. 10 shows a system 100 for measuring ionizing radiation, comprising measurement device |, radiation system 40, a movable platform 20, a reading combining unit 50, a first controller 30, and a second controller 31. Measurement device 1 is arranged on top of movable platform 20, such that movable platform 20 is able move measurement device 1 into various positions relative to radiation source 5. Radiation system 40 comprises stationary frame 5’ and radiation source 5 mounted to the stationary frame.
First controller 30 comprises a first sub-controller 30A and a second sub-controller 30B. Second sub-controller 30B is configured to control movable platform 20 to move measurement device 1 in the first, second and/or third direction so as to place measurement device 1 in the position required for a particular measurement. Second controller 31 is configured to control measurement device 1 to perform a measurement as described in relation to Figs. 2-7B. First sub- 19 controller 30A is configured to control radiation system 40 to move radiation source 5 and/or to emit ionizing radiation using radiation source 5 towards measurement device 1 according to a pre- determined treatment plan which is applied to radiation system 40.
It will be appreciated that, although sub-controllers 30A, 30B are described as parts of a first controller 30, they can be formed by separate controllers. However, sub-controllers 30A, 30B may also be combined with second controller 31 as a single controller. Furthermore, reading combining unit 50 can be part of or be formed by a computer system, such as a personal computer or laptop.
An exemplary process of acquiring a high resolution reading is as follows. First, sub- controller 30B controls movable platform 20 to move measurement device 1 in the first position relative to stationary frame 5°. For the first measurement, the first shell is mounted to the housing of measurement device 1, which may be done either manually or automatically. Then, sub- controller 30A controls radiation system 40 according to the pre-determined treatment plan, while controller 31 controls measurement device 1 to perform the first measurement. After performing the first measurement, a first low resolution reading of the first and, if applicable, second detector member of measurement device 1 is obtained by reading combining unit 50.
After obtaining the first low resolution reading, controller 30B controls movable platform 20 to move measurement device 1 in the second position relative to stationary frame 5’. Similarly, for the second measurement, the second shell is mounted to the housing of measurement device 1. Then, controller 30A controls radiation system 40 according to the pre-determined treatment plan, while controller 31 controls measurement device 1 to perform the second measurement. After performing the second measurement, a second low resolution reading of the first and, if applicable, second detector member of measurement device 1 is obtained by reading combining unit 50.
In this embodiment, radiation source 5 is moved around measurement device 1 and the combined ionizing radiation that is irradiated towards the sensor elements during this movement is measured during the first and second measurement. Alternatively, radiation source 5 is controlled to be at a number of separate positions. For each of these positions, a respective first measurement and a respective second measurement is obtained. By combining the respective first and second measurements for a given position of the radiation source, a high resolution reading is obtained for that position. This process can be performed for each of the positions of radiation source 5.
The above process of moving measurement device 1 and performing a measurement can similarly be performed until all desired low resolution readings have been obtained, after which reading combining unit 50 combines the plurality of low resolution readings and the high resolution reading corresponding to a measurement of the pre-determined treatment plan applied to radiation system 40 is obtained. The high resolution reading can then be used to analyze whether the measured treatment plan sufficiently corresponds to the calculated or predicted treatment plan. In the above, the present invention has been explained using detailed embodiments thereof. However, it should be appreciated that the invention is not limited to these embodiments and that various modifications are possible without deviating from the scope of the present invention as defined by the appended claims.
Claims (28)
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| NL2026670A NL2026670B1 (en) | 2020-10-13 | 2020-10-13 | System and assembly for measuring an ionizing radiation dose |
| PCT/NL2021/050620 WO2022081008A1 (en) | 2020-10-13 | 2021-10-12 | System and assembly for measuring an ionizing radiation dose |
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| US20090166541A1 (en) * | 2007-12-28 | 2009-07-02 | Katsutoshi Tsuchiya | Radiation imaging system, nuclear medicine diagnosis apparatus and positioning adjusting mechanism |
| WO2020183733A1 (en) * | 2019-03-14 | 2020-09-17 | 株式会社島津製作所 | X-ray imaging device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20090166541A1 (en) * | 2007-12-28 | 2009-07-02 | Katsutoshi Tsuchiya | Radiation imaging system, nuclear medicine diagnosis apparatus and positioning adjusting mechanism |
| WO2020183733A1 (en) * | 2019-03-14 | 2020-09-17 | 株式会社島津製作所 | X-ray imaging device |
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