Patent Application
20170003403
The invention relates to the field of radiation dosimetry. More specifically it relates to a dosimetry device for determining a spatial distribution of a quantity of radiation such as an ionization chamber array for quality assurance and/or online verification in radiotherapy or particle therapy, e.g. proton or carbon therapy. The invention also provides a related system and method for determining a spatial distribution of a quantity of radiation.
In radiation dosimetry, dosimeters such as ionization chambers are used for performing measurements in order to calculate the radiation dose received by matter, e.g. tissue, due to the exposure to indirect and/or direct ionizing radiation. Radiation dosimetry is particularly important in the fields of medical physics, e.g. for monitoring the required treatment dose and any collateral dose. Air-filled ionization chambers can be considered as the gold standard for dosimetric detection in medical physics due to similarity between radiation interaction with air and organic tissues.
For radiation therapy, arrays of ionization chambers may be particularly useful for determining or monitoring a spatial distribution of a radiation field, e.g. a high-energy photon beam shaped to correspond to a target dose distribution in a patient. Ionization chamber arrays as known in the art may comprise for example air-vented cubic ionization chambers, air-vented cylindrical chambers, covering a squared area with a pitch of 5 mm or higher, e.g. a pitch of 7.6 mm or a pitch of 10 mm. The number of ionization chambers in such array may for example be 251 or higher, e.g. 729 chamber elements, or even higher, e.g. 1020 chamber elements.
An ionization chamber array as known in the art may comprise a plurality of individual ionization chambers placed side by side in an array geometry, for example as described by Martell et al. in “A flatness and calibration monitor for accelerator photon and electron beams”, International Journal of Radiation Oncology-Biology-Physics 12, pages 271-275. However, manufacturing such composite arrays of ionization chambers with high spatial resolution and/or a large number of pixel elements, e.g. hundreds or even thousands of pixels, may be unpractical and expensive.
Other ionization chamber arrays known in the art, for example as disclosed in U.S. Pat. No. 8,044,364, may comprise a segmented planar electrode and a common planar electrode arranged in a parallel plane geometry, in which the distance between the electrodes is fixed by an external insulating frame running along the array perimeter, such that a large air-filled cavity is formed between the electrodes. An example of this type of prior-art ionization chamber array 90 is shown in
This design enables a more efficient manufacture of the ionization chamber array compared to a composite array of individual ionization chambers, however such integrated ionization chamber array may be prone to mechanical instability. The top electrode is supported on its external edge by the spacer frame, and therefore can bend in the central region, which may be especially disadvantageous in the case of a large area array and/or in applications which requires a particularly thin electrode. Furthermore, mechanical instability may couple to ambient vibrations, such that a noise component can be induced thereby in the measured signal, e.g. a signal component similar to microphone transduction. Another disadvantage of this integrated design may be blurring of the measured spatial dosimetric distribution, e.g. the generated dosimetric image, due to secondary electrons generated by the interaction of the incident beam with the medium in the cavity and/or the top electrode walls. In the common cavity, secondary electrons may freely migrate, even in a direction transverse to the beam. Therefore, photons or high-energy particles entering in the cavity volume portion corresponding to a certain pixel may generate a signal in an adjacent one, thus leading to image blurring.
Yet other ionization chamber arrays are known in the art in which a segmented electrode and a common electrode are separated by an insulating layer with holes. An example thereof has been described in international patent application WO 2012/168601 and in U.S. Pat. No. 7,476,867. Each hole may be centered on a pixel, thus defining the volume of the corresponding ionization chamber. An example of this design is illustrated in
It is an object of embodiments of the present invention to provide means and methods for determining an accurate spatial distribution of photon or particle radiation. It is an advantage of embodiments of the present invention that detectors and methods can be obtained wherein little or no cross-talk occurs, resulting in accurate and clear images of the spatial distribution of photon or particle radiation.
It is an advantage of embodiments of the present invention that a high spatial resolution and/or a large number of pixel elements can be easily and cost-efficiently manufactured.
It is an advantage of embodiments of the present invention that good mechanical stability can be achieved in an ionization chamber array. It is a further advantage of such embodiments that no substantial microphone transduction noise component is present in the radiation measurement signal acquired by a device or method according to embodiments.
It is an advantage of embodiments of the present invention that little blurring of the measured spatial dosimetric distribution due to inter-pixel diffusion of secondary electrons in the cavity volume, and therefore little blurring of the generated dosimetric image, occurs.
It is an advantage of embodiments of the present invention that small ionization chambers may be provided in a dosimetric array, e.g. providing high spatial resolution and improved performances in high dose rate condition.
It is an advantage of embodiments of the present invention that good long term stability of a dosimetry device according to embodiments can be achieved.
It is an advantage of particular embodiments of the present invention that even better spatial resolution and/or angular dependence can be achieved by coupling two common electrodes to the top and bottom surfaces of the same PCB. The above objective is accomplished by a method and device according to the present invention.
The present invention relates to a dosimetry device for determining a spatial distribution of a quantity of radiation incident on the dosimetry device, the dosimetry device comprising
a segmented electrode assembly comprising an electrically non-conducting substrate having a plurality of electrode elements provided thereon, the segmented electrode assembly comprising a plurality of guard electrodes, each guard electrode being arranged around a corresponding electrode element of the plurality of electrode elements and
an electrically conducting sheet comprising a protrusion arranged for forming a plurality of ionization chamber cavities, said electrically conducting sheet being coupled with said segmented electrode assembly such that each of said plurality of ionization chamber cavities corresponds to one electrode element of the plurality of electrode elements and the plurality of ionization chamber cavities fillable with a fluid, and
a voltage applying means for applying a voltage difference between the electrically conducting sheet and the plurality of electrode elements and a routing means for routing a plurality of ionization currents corresponding to the plurality of electrode elements to a processing means.
It was surprisingly found that by using the above specified arrangement, cross-talk between different pixels was drastically reduced and/or avoided. Furthermore, the specified arrangement still allows for cost-efficient and simple manufacturing of the device.
The protrusion may comprise a perimetral protrusion arranged in mechanical contact with said segmented electrode assembly such as to define a plurality of ionization chamber cavities.
The protrusion may comprise non-perimetral protrusions for defining a plurality of ionization chamber cavities.
The segmented electrode assembly may comprise a printed circuit board having said plurality of electrode elements defined thereon.
It is an advantage of embodiments of the present invention that the arrangement can be used for transparent detectors, e.g. detectors that can be installed between the radiation machine and the patient) as well as for non-transparent detectors. The thickness of the PCT may in some embodiments be restricted to equal or less than 5 mm.
The plurality of electrode elements may be printed on the printed circuit board using a carbon-based material.
The height of one, more or preferably each of the plurality of ionization chamber cavities can be equal or less than 3 mm, advantageously equal or less than 2 mm. It is an advantage of embodiments of the present invention that a thin detector can be obtained.
The electrically conducting sheet may comprise a material with a low atomic number such as carbon, conductive plastic and/or aluminum.
The fluid medium may comprise air.
The electrically conducting sheet may comprise a plurality of concave surface regions corresponding to the plurality of electrode elements defined by further protrusions of the electrically conducting sheet for forming the plurality of ionization chamber cavities.
The plurality of electrode elements may be arranged along at least a one dimensional or two dimensional regular grid on said electrically non-conducting substrate.
The plurality of electrode elements may extend into its ionization chamber cavity and each electrode element may be adapted in shape for tailoring the electric field in its ionization chamber cavity.
The plurality of electrode elements may comprise a first plurality of electrode elements provided on a first major surface of the electrically non-conducting substrate and a second plurality of electrode elements provided on a second major surface of the electrically non-conducting substrate. The perimetral protrusion may be arranged in mechanical contact with the first major surface of the electrically non-conducting substrate. The dosimetry device further may comprise a second electrically conducting sheet comprising a protrusion, e.g. a perimetral protrusion arranged in mechanical contact with the second major surface of the electrically non-conducting substrate, such as to define at least one ionization chamber cavity between the segmented electrode assembly and the electrically conducting sheet.
The first plurality of electrode elements and the second plurality of electrode elements may be arranged according to the same pattern on respectively the first major surface and the second major surface, and the device may comprise means for electrically connecting each electrode of the first plurality of electrodes to the corresponding electrode of the second plurality of electrodes.
The first plurality of electrode elements and the second plurality of electrode elements may be arranged according to the same pattern, the first plurality of electrode elements being spatially offset in the plane of the substrate with respect to the second plurality of electrode elements.
The dosimetry device may further comprise at least one further segmented electrode assembly comprising a further electrically non-conducting substrate having a further plurality of electrode elements provided thereon, and at least one further electrically conducting sheet comprising a further perimetral protrusion arranged in mechanical contact with said at least one further segmented electrode assembly such as to define at least one further ionization chamber cavity between the at least one further segmented electrode assembly and the at least one further electrically conducting sheet.
The present invention also relates to a dosimetry system comprising a dosimetry device as described above and a processing means for receiving the plurality of ionization currents corresponding to the plurality of electrode elements via the routing means, the processing means being adapted for determining a spatial distribution of radiation dose, radiation dose rate or radiation fluence corresponding to a radiation quantity incident on the dosimetry device taking into account the plurality of ionization currents.
The present invention also relates to a method for determining a spatial distribution of a quantity of radiation, the method comprising:
applying a voltage difference between a plurality of electrode elements provided on an electrically non-conducting substrate and an electrically conducting sheet having a protrusion arranged for forming a plurality of ionization chamber cavities, said electrically conducting sheet being coupled with said segmented electrode assembly such that each of said plurality of ionization chamber cavities corresponds to one electrode element of the plurality of electrode elements, the plurality of electrode elements furthermore each being shielded by a guard electrode being arranged around a corresponding electrode element of the plurality of electrode elements and determining a plurality of ionization currents corresponding to the plurality of electrode elements generated by interaction of radiation within a fluid medium in said plurality of ionization chamber cavities.
The protrusion may be a perimetral protrusion arranged in mechanical contact with the electrically non-conducting substrate. The protrusion may define a plurality of ionization chamber cavities between the electrically non-conducting substrate and the electrically conducting sheet. The method may further comprise positioning the electrically non-conducting substrate and the electrically conducting sheet between a source of the radiation and a target, such that the radiation travels through the plurality of ionization chamber cavities prior to delivering the radiation to the target.
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.
The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.
Any reference signs in the claims shall not be construed as limiting the scope.
In the different drawings, the same reference signs refer to the same or analogous elements.
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
Moreover, the terms top, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.
It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
In a first aspect, the present invention relates to a dosimetry device for determining a spatial distribution of a quantity of radiation incident on the dosimetry device. The dosimetry device may also be referred to as a radiation dosimeter or as an ionization chamber array. The radiation incident on the dosimetry device may for example comprise uncharged radiation, e.g. high energetic photon radiation or neutron radiation, and/or charged radiation, e.g. proton radiation, electron radiation, charged hadron radiation or ion radiation. Determining the spatial distribution of a quantity of the radiation may thus comprise determining in a plurality of regions in space, e.g. regions distributed along a line, on a plane or in a volume, a measure associated with the radiation. Such measure may for example comprise a radiation dose, dose rate, or fluence, e.g. a measure for kinetic energy released per unit mass (kerma). The device according to embodiments of the present invention may for example be suitable for determining a spatial radiation dose distribution generated by for example an incident photon beam comprising energies in the range of 1 MeV to 20 MeV, or an incident proton beam comprising energies in the range of 50 MeV to 250 MeV. A device according to embodiments may advantageously achieve a high spatial resolution, e.g. may have an effective pixel pitch of less than 5 mm, for example 3.5 mm or even less, for example 2 mm. It was furthermore found that by selecting a specific arrangement according to embodiments of the present invention devices with surprisingly very little or no cross-talk between different pixels can be obtained.
The dosimetry device comprises a segmented electrode assembly which comprises an electrically non-conducting substrate having a plurality of electrode elements provided thereon. The dosimetry device further comprises an electrically conducting sheet which comprises a protrusion a protrusion arranged for forming a plurality of ionization chamber cavities. The protrusion may comprise a perimetral protrusion arranged in mechanical contact with the segmented electrode assembly and non-perimetral protrusions such as to define a plurality of ionization chamber cavities between the segmented electrode assembly and the electrically conducting sheet. The plurality of ionization chamber cavities thereby is arranged such that each ionization chamber cavity corresponds to one electrode element of the plurality of electrode elements. The dosimetry device further comprises a voltage applying means for applying a voltage difference between the electrically conducting sheet and the plurality of electrode elements, e.g. for applying a bias potential to the electrically conducting sheet with respect to a pixel element potential. The voltage applying means may be any type of voltage applying means, such as for example a voltage source. The voltage applying means also may comprise a set of electrodes connected to the voltage source for applying a voltage to certain nodes. The dosimetry device also comprises a routing means for routing a plurality of ionization currents corresponding to the plurality of electrode elements to a processing means. Such a routing means may for example correspond with a plurality of electrodes. According to embodiments of the present invention, the segmented electrode assembly also comprises a plurality of guard electrodes, each guard electrode being arranged around a corresponding electrode element of the plurality of electrode elements. Different standard and optional features in exemplary embodiments will be discussed in further detail with reference to the drawings.
Referring to
The dosimetry device 10 comprises a segmented electrode assembly 12. The segmented electrode assembly 12 comprises an electrically non-conducting substrate 13, e.g. a substrate comprising an electrically insulating material, e.g. a plastic substrate, a ceramic substrate, a substrate comprising a fiber-glass based material commonly used for PCB's, a material having a relative permittivity of at least 2.0, for example silicon dioxide, etc. Particularly, the electrically non-conducting substrate 13 may be a planar electrically non-conducting substrate.
The electrically non-conducting substrate 13 has a plurality of electrode elements 14 provided thereon. Thus, a segmented electrode, e.g. the plurality of electrode elements 14, may be defined on the insulating surface of a planar support, e.g. a major surface of the non-conducing substrate 13.
The plurality of electrode elements 14 may be arranged along at least one straight line on the electrically non-conducting substrate 13. For example, a one-dimensional array of electrode elements 14 may be provided on the electrically non-conducting substrate 13. The plurality of electrode elements 14 may be configured as a grid, e.g. a regular grid such as an equidistantly spaced Cartesian grid, on the electrically non-conducting substrate 13. However, other arrangements of the plurality of electrode elements 14 lie well within the scope of the present invention, for example a polar grid arrangement.
The segmented electrode assembly 12 also comprises a plurality of guard electrodes 24, e.g. annular guard electrodes, in which each guard electrode is arranged around a corresponding electrode element of the plurality of electrode elements 14. Thus, each of the pixel electrodes may be substantially encircled by a corresponding conductive guard ring, for example the pixel electrodes may be encircled by a conductive guard ring. Alternatively, the guard electrodes may comprise separate electrodes that are positioned around the pixel electrodes.
The active volume of each pixel within its ionization chamber cavity, e.g. within the air-filled cavities, may be defined by the lines of electric field. The charge ionized by radiation close to the guard electrodes will flow through this electrode, thus reducing the blurring of dosimetric images formed by the device.
The plurality of electrode elements 14, e.g. the pixel electrodes, may provide charge readout for the individual pixels, e.g. by supplying an ionization current via the routing means to a processing means. Each pixel electrode may be surrounded by a guard electrode kept at the same potential to avoid the flow of surface current from the conducting sheet, e.g. the common electrode, to pixels. All the guard electrodes may be connected together, e.g. may be maintained at the same electrical potential. Where in embodiments of the present invention reference is made to guard electrodes surrounding a pixel electrode, the latter does not require full encircling of the pixel electrode. Different portions of guard electrodes may be positioned at different sides of the pixel electrode. In some embodiments therefore, instead of having circular guard electrodes, a number of segments may be positioned at different sides.
The segmented electrode assembly 12 may comprise a printed circuit board (PCB) having the plurality of electrode elements 14 defined thereon. The plurality of electrode elements, e.g. the pixel electrodes, may be preferably printed on the printed circuit board with a carbon-based material, such that a better quality of dosimetric measurements can be achieved compared to conventional copper printing. Likewise, the plurality of guard electrodes and/or at least a portion of the voltage applying means 28 and/or the routing means 25 (shown schematically in
The dosimetry device 10 further comprises an electrically conducting sheet 16 which comprises a perimetral protrusion 17 arranged in mechanical contact with the segmented electrode assembly 12 such as to define a plurality of ionization chamber cavities 18 between the segmented electrode assembly and the electrically conducting sheet. Thus, a plurality of ionization chamber cavities between the segmented electrode assembly and the electrically conducting sheet is defined. According to embodiments of the present invention, the plurality of ionization chamber cavities are arranged such that each ionization chamber cavity corresponds to one electrode element of the plurality of electrode elements.
In embodiments of the present invention, the electrically conducting sheet 16 may be directly connected, e.g. mechanically connected, to the segmented electrode assembly 12 via at least the perimetral protrusion 17. For example, the electrically conducting sheet 16 may be connected to the segmented electrode assembly 12 by conventional means such as gluing or soldering. Furthermore, small gaps or channels may be defined in the perimetral protrusion in order to allow venting of the ionization chamber cavity, e.g. in the case of an air-filled cavity, without substantially affecting the mechanical stability of the device.
In the conductive material of the electrically conducting sheet 16, electrons may move freely, such that charge trapping induced by radiation can be compensated in the sheet 16. Therefore, embodiments of the present invention may advantageously exhibit good resistance to radiation damage.
The device may also comprise a fluid medium filling the plurality of ionization chamber cavities 18, e.g. the plurality of ionization chamber cavities 18 may be gas-filled ionization chamber cavities. For example, the fluid medium may comprise air. However, other media may also be encompassed by the scope of the present invention, for example noble gases or liquids suitable for ionization chambers.
The electrically conducting sheet 16 may be a common top electrode of an array of ionization chambers, in which the plurality of electrode elements 14 may form the bottom electrodes corresponding to the common top electrode. The electrically conducting sheet 16 may comprise a graphite material. The electrically conducting sheet 16 may comprise an electrically conductive plastic, e.g. an intrinsically conducting polymer, and/or low atomic weight metals or metal alloys, e.g. aluminum.
Thus, the common top electrode may be advantageously produced from a single slab of conductive material, and the plurality of ionization chamber cavities may be formed by carving, milling or machining the surface of the conductive plate facing the segmented electrode assembly. Other processing techniques nevertheless also may be made.
In order to improve the ionization chamber energy dependence, such a material may also have preferably a low atomic number, such as conductive plastic or graphite, in order to reproduce radiation-matter interaction in organic tissues or water. Aluminium, or other light metals or metal alloys, may also be used to achieve a good mechanical accuracy of production. Combinations of such materials may also be used, e.g. homogeneous compounds or mixtures thereof and/or layered structures formed by such materials.
The dosimetry device 10 may also comprise a voltage applying means for applying a voltage difference between the electrically conducting sheet and the plurality of electrode elements 14 and a routing means for routing a plurality of ionization currents corresponding to the plurality of electrode elements 14 to a processing means. For example, the voltage applying means and/or the routing means may comprise conductive paths arranged in, on and/or through the electrically non-conducting substrate, e.g. printed on a printed circuit board. The routing means may comprise multiplexers and/or addressing means for routing the plurality of ionization currents to the processing means. The device 10 may comprise routing means, e.g. printed circuit board connections, wires and/or multiplexing or addressing means as commonly used in the art, the implementation of such routing means requiring mere application of common knowledge and skill. The processing means may be an external processing means, e.g. the routing means may provide a signal output port for connecting the processing means to. The processing means may for example comprise an integrated circuit adapted for processing signals representative of the ionization currents. The processing means may comprise a general purpose processor programmed for processing such signals. The processing means may also be entirely or in part implemented in or on the electrically conducting substrate, e.g. processing of the signals may take place in an integrated circuit provided on the electrically conducting substrate, for example in an edge region of the substrate such that interaction of the incident radiation being measured and the integrated circuit is substantially avoided. Methods for the processing of signals representing ionization currents acquired by ionization chamber arrays are well-known in the art.
In advantageous embodiments, the mechanical connection of the electrically conducting sheet 16 to the segmented electrode assembly 12 via the perimetral protrusion may also provide a conductive path to a portion of the voltage applying means arranged on the electrically non-conducting substrate, such that the connection for applying a voltage difference between the electrically conducting sheet and the plurality of electrode elements 14 does not require a separate wire connection to the electrically conducting sheet 16. For example, the common top electrode may sit on a conductive ring (an example thereof being shown in
In the particular example shown in
An additional advantage is that the thickness h of the cavities may be independent of the overall thickness h+d of the electrode. More particularly, as the thickness of the cavities can be selected by the processing of the cavity in the electrically conducting sheet, it becomes possible to construct chambers with a very thin active volume, e.g. h smaller than or equal to 1 mm, while retaining a good mechanical stability by selecting a sufficiently high thickness d of the remaining part.
Overall, in embodiments of the present invention, the height of the cavities may be equal to or smaller than 3 mm, e.g. equal to or smaller than 2 mm.
In other embodiments, e.g. as shown in
While in particular embodiments the pixel electrode elements may be substantially flat, e.g. merely obtained by printing, in other embodiments the electrode elements extending into the ionization chamber cavities may provide an additional degree of freedom to tailor the electric field lines, e.g. for increasing the maximum bias and chamber charge collection efficiency. In embodiments according to the present invention, the plurality of electrode elements 14 may extend into the plurality of ionization chamber cavities 18. Particularly, the plurality of electrode elements 14 may be adapted in shape for tailoring the electric field in the ionization chamber cavities. For example, as illustrated in
As depicted in
An alternative arrangement is shown in
In embodiments according to the present invention, the dosimetry device may also comprise at least one further segmented electrode assembly comprising a further electrically non-conducting substrate having a further plurality of electrode elements provided thereon, and at least one further electrically conducting sheet comprising a further perimetral protrusion arranged in mechanical contact with the at least one further segmented electrode assembly such as to define at least one further ionization chamber cavity between the at least one further segmented electrode assembly and the at least one further electrically conducting sheet. Thus, a segmented electrode assembly 12, an electrically conducting sheet 16 and a voltage applying means and/or routing means as described previously may form a module, in which a device according to embodiments may comprise several such modules arranged to cover a wider area in a plane, e.g. for simplifying service operations on the device, or may be arranged in more complex arrangements, e.g. to determine a three-dimensional spatial distribution of radiation, for example by stacking the modules.
In a second aspect, the present invention also relates to a dosimetry system, e.g. as illustrated in
In a third aspect, the present invention also relates to a method 80 for determining a spatial distribution of a quantity of radiation. Referring to
The method 80 may also comprise positioning 83 the electrically non-conducting substrate 13 and the electrically conducting sheet 16 between a source of the radiation and a target, such that the radiation travels through the at least one ionization chamber cavity 18 prior to delivering the radiation to the target.
As an example for illustrating embodiments according to the present invention, experimental results achieved with a linear array of 32 pixels according to embodiments is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 13195217.8 | Nov 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/076034 | 11/30/2014 | WO | 00 |
