REFERENCE TO RELATED PATENT APPLICATION
This application claims priority to European Patent Application No. 23158167.9 filed on Feb. 23, 2023, which is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
The present disclosure concerns a dynamic shaping device for shaping the Spread-Out Bragg Peaks (=SOBP) of pencil beams, that can be adjusted to adapt to the geometry of any target volume comprising tumoural cells or other conditions requiring irradiation. The shaping device comprises a dynamic ridge filter and/or a dynamic range shifter. The dynamic shaping device of the present disclosure comprises a number of identical rows formed by a number of modules of different predefined geometries. Each row is configured to translate independently along a Y-axis to define a string formed by a selection of one module of each row aligned along an X-axis (X L Y) and configured to shape the dose deposited onto the specific volume facing the string.
The dynamic shaping device of the present disclosure has the advantage that a single dynamic shaping device can be used to shape the pencil beams for treating different tumours of different geometries. It allows substantial time and cost saving as it is not necessary to produce a new shaping device for every patient and, also, for different irradiation sessions to a same patient, as the geometry of a tumour and patient can evolve with time. Having a dynamic shaping device allows for immediate treatment plan adaptation.
BACKGROUND
Radiation therapy with particles or waves, such as electron beams, protons beams, heavy ions beams, x-rays, γ-rays, and the like, has become an essential tool for treating patients with tumours.
Since both tumoural cells and healthy cells comprised in a volume are irradiated, a first challenge in cancer treatment is to define a treatment plan ensuring that defined doses are deposited into the tumoural cells to effectively destroy or kill them, while limiting the doses deposition into healthy cells to spare them as much as possible. A second challenge is to actually deposit the defined doses onto the tumoural cells whilst limited doses are actually deposited onto the healthy cells as planned.
Different radiation modalities deposit their energies in different patterns. For example, X-rays deposit most of their energy near the level of the skin, and the deposited energy decreases with penetration depth into the tissues. Healthy tissues located upstream of a treatment volume of tumoural cells therefore receive a higher dose than the cells located in the treatment volume. By contrast, charged particle beams, such as protons and carbon ions, deposit most of their energy close to the end of their beam path, forming a so-called Bragg peak.
The charged particles emerging from a nozzle of a particle accelerator form a narrow pencil beam. To cover a treatment volume of practical size, the pencil beam must be spread laterally either by introducing scattering material in the beam path or by scanning the beam over the desired area. Pencil beam scanning (PBS) and double scattering (DS) proton therapy are two techniques allowing physicians to deliver a precise, powerful dose of radiation that covers the tumour with minimal radiation exposure to healthy tissues.
PBS is very advantageous because it optimizes the geometrical distribution of the dose deposition to match it with the geometry of the treatment volume enclosing the tumour. PBS treatment time can, however, be long as the PBS-beams must scan over each spot and over multiple mono-energetic layers. Moving a PBS-beam from onemono-energectic layer to the next one with different energies is time consuming, of the order of 500 ms. It is therefore advantageous, when irradiation time is a factor, such as in FLASH-RT, to reduce the number of layers, optimally to a single layer.
Saving treatment time reduces the operation time of a particle accelerator by each patient. It is also more comfortable for the patient. It is also advantageous if the treatment plan comprises FLASH irradiation, wherein doses are deposited into the cells at high dose rates (HDR), of at least 1 Gy/s or even up to at least 40 Gy/s. A given high dose (e.g., 5 to 10 Gy) deposited at HDR has shown to better spare healthy cells relative to the same dose deposited at lower conventional dose rates (CDR). Where FLASH irradiation is particularly interesting, is that a given dose deposited into tumoural cells has the same killing effect irrespective of whether it was deposited at HDR or at CDR.
“Painting” a target volume in depth with a single layer can be achieved by shaping the pencil beams delivered towards the volume to be treated by means of a shaping device intersecting the pencil beam path. A shaping device is a device positioned between a source of accelerated particles and a treatment volume, changing the energy profile and/or the geometry of the beam traversing it. It is designed for absorbing a portion of the required energy of a portion of the protons from the pencil beams to control the specific volumes where doses are deposited onto by each pencil beam. The present disclosure concerns more particularly ridge filters and range shifters and shaping devices composed of at least one ridge filter and at least one range shifter.
A CT-scan image of a patient is produced, which values are converted to proton stopping power. A treatment plan is established by a practitioner defining the doses to be deposited onto specific volumes. One or more shaping devices are designed by a treatment planning system (TPS) which shapes the beam to match a geometry of the treatment volume comprising tumoral cells, for depositing specific doses onto specific locations within the treatment volume according to the treatment plan while minimizing the dose deposited onto healthy tissues
A ridge filter allows shaping the Spread-Out Bragg Peak (SOBP) along the corresponding pencil beam axis (Zj). As illustrated in FIGS. 3(b) and 3(c). Ridge filters are known in the art and comprise energy spreading units distributed on a base. They are in the form of smooth-pins or step pyramids, or crests extending along the beam axes (Zj) of the individual pencil beams. For example, EP21208699 describes a ridge filter comprising a plurality of energy spreading units in the form of orifices or pins arranged side by-side according to the-array of spots in a support base. Each energy spreading unit is formed by one or more spreading subunits in the form of orifices or pins having a generalized cylindrical geometry of cross-sectional areas and extending along the corresponding beam axis (Zj) from the-support block. The spreading subunits can for example be stacked on top of one another along the corresponding irradiation axis (Zj). The superposition of spreading subunits forming each energy spreading unit allows shaping and varying the width of the Spread-Out Bragg Peak (SOBP) along the corresponding beam axis (Zj).
A range shifter consists of slabs of stopping material inserted between the nozzle and the treatment volume and is used to reduce the residual range of the incident beam so that the treatment ranges can be extended to shallow depths. In particular, a range shifter allows limiting the region where doses are deposited at a downstream (or distal) end of the treatment volume, relative to the particles' propagation direction. For a material of given particle stopping capacity, varying the thickness of the slabs facing each pencil beams allows match the boundary where doses are deposited to the geometry of the downstream surface of the target volume.
When used for HDR irradiation using a single mono-energetic layer, ridge filters and range shifters are unique devices usable once only for one patient and are tailor-made according to the corresponding planned device design to match the type and geometry of tumour to be treated. They can be produced by machining, but they are generally produced by 3D-printing, which is still time-consuming and relatively expensive (although less than by machining). The shaping devices could also need replacement by new ones for treatment of a same tumour of a same patient in different irradiation sessions because, as shown in CT-scan images, the geometry of the tumour or patient varies with time and with the preceding irradiation sessions leading to a dose distribution unacceptable by clinicians if the shaping devices are unchanged.
The present disclosure proposes a dynamic shaping device, including a dynamic ridge filter and/or a dynamic range shifter, that can be re-used several times and adapted for the treatment of tumours of different geometries. These and other advantages of the present disclosure are described in continuation.
SUMMARY
The present disclosure is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims. In particular, the present disclosure concerns a dynamic ridge filter, a dynamic range shifter, and a dynamic shaping device comprising the dynamic ridge filter and the dynamic range shifter, each of them being configured for shaping a dose deposition zone by radiation with charged particles beams, preferably with proton or other light ion beams, and for depositing doses (Dj) applied by pencil beams (Bj) propagating along corresponding irradiation axes (Zj) fanning out of a central irradiation axis (Z) by a pencil beam scanning (PBS) system and delivered in sequence to specific volumes (Vj) along a X-axis to form specific volume stripes distributed next to one another along a Y-axis transverse, preferably normal, to the X-axis, the specific volumes (Vj) defining in combination a target volume (Vt) comprising the tumoral cells,
The dynamic ridge filter comprises a number of energy spreading units, each energy spreading unit being characterized by a corresponding energy spreading capacity for spreading the dose deposited along the irradiation axis (Zj) by the corresponding pencil beams (Bj) traversing one or more energy spreading units. The gist of the dynamic ridge filter is that the energy spreading units are distributed in filter modules, each filter module supporting one or more energy spreading units and having an area normal to the central irradiation axis (Z) compatible with a cross-section of the corresponding pencil beam (Bj). The filter modules are arranged in different filter rows, each extending along the row-direction (Y).
Each filter row comprises a number of dissimilar filter modules. Each filter module of a filter row has a different energy spreading capacity from the other filter modules of the same filter row. Each filter row can be displaced independently to form a filter string along the X-axis and the filter string is configured to shape the dose deposition in the specific volumes (vj) forming the specific volume stripe facing the filter string along the irradiation axes (Zj). All filter rows are preferably identical and comprise a same selection of filter modules, to be combined to form a corresponding filter string.
In an embodiment, the energy spreading units are in the form of spikes of generalized cylindrical, preferably prismatic geometry, or of conical geometry, truncated or not, preferably a pyramidal geometry. The spikes are supported on a base of the filter modules and are configured in use for having a major axis of the spikes extending parallel to the corresponding pencil beam axes (Zj).
In an alternative embodiment, the energy spreading units are in the form of orifices of generalized cylindrical or conical geometry penetrating in a support base of the filter modules. Each orifice extends from an aperture opening at a surface of the support base and penetrating to a given depth leaving a resulting thickness of material of the support base. The orifices are configured in use for having a major axis of the cavities extending parallel to the corresponding pencil beam axes (Zj).
Each filter module can comprise one or more energy spreading units, each formed by a plurality of spreading subunits having differing cross-sectional areas (Ai) normal to the irradiation axis (Zj). They can be stacked on top of one another along a major axis of the energy spreading unit configured in use for extending parallel to the irradiation axis (Zj), wherein all spreading subunits of the stack have different energy spreading capacities.
The dynamic range shifter has a thickness of material varying over an area of the range shifter, the area being configured for being substantially normal to the irradiation axis (Zj) in use, wherein a value of the thickness determines a corresponding amount of absorbed energy (ΔE) of the pencil beam (Bj) of the charged particles traversing the thickness. A topography of the range shifter approximates a topography of a downstream portion of the target volume (Vt), wherein “downstream” is defined relative to the particle irradiation direction.
The gist of the range shifter of the present disclosure is that the range shifter comprises shifter modules arranged side-by-side to form shifter rows, wherein each shifter row comprises a selection of shifter modules having a constant or almost constant thickness different from the other shifter modules of the same shifter row, and configured for absorbing different amounts of reference absorbed energy (ΔE) from the pencil beam (Bj). The shifter row has a step-geometry. Alternatively, the shifter row can have a continuous geometry, forming a continuous slope from a high thickness to a low thickness, wherein each shifter module has a varying thickness, whose high and low values are equal to the low and high values of the thicknesses of the shifter modules adjacent thereto on either side. This geometry can be defined as an infinite number of infinitely thin slices of decreasing height measured along the central irradiation axis (Z) aligned side by side along the Y-axis.
The range shifter, with step- or continuous-geometry is such that,
- each shifter row can be displaced independently to form a shifter string along the X-axis,
- the shifter string is configured to shape along the irradiation axes (Zj) the dose deposition in the specific volumes (Vj) forming the specific volume stripe facing the shifter string along the irradiation axes (Zj).
All shifter rows are preferably identical comprising a same selection of shifter modules.
The dynamic shaping device comprises at least a dynamic ridge filter as defined supra and at least a dynamic range shifter as defined supra disposed in a sequence along a beam path of a pencil beam (Bj), such that the filter string and the shifter string face each other along a direction, which in use is parallel the irradiation axis (Zj), to form in combination a radiation string.
The present disclosure also concerns a treatment station comprising,
- a source of pencil beams (Bj) of accelerated charged particles, preferably of protons,
- a nozzle for directing the pencil beams (Bj) of accelerated charged particles towards the target volume (Vt), the nozzle comprising electromagnetic elements configured for deviating the pencil beam (Bj) to scan along at least the X-axis as the nozzle remains static,
- a dynamic ridge filter a defined supra
- a dynamic range shifter as defined supra,
- a couch or chair for receiving the patient in supine, prone, seated or standing position,
- one or more processors configured for controlling various components of the treatment station,
wherein the dynamic ridge filter (1) and dynamic range shifter are arranged such as to form a shaping device as defined supra.
In a preferred embodiment of the treatment station of the present disclosure,
- the electromagnetic elements are configured for deviating the pencil beam (Bj) to scan also along the Y-axis as the nozzle remains static, and
- the shaping device is provided with a translation system configured for following a translation of the pencil beam along the Y-axis such that the filter string and the shifter string move together with the shaping device keeping in alignment with the pencil beam along the Y-axis, or
- the filter string and the shifter string move along the Y-axis relative to the shaping device which preferably remains static relative to the target volume (Vt), in order to keep in alignment with the pencil beam along the Y-axis, or
- The couch is provided with a translation system configured for translating the couch along the Y-axis to align the specific volumes (Vj) with the corresponding pencil beams (Bj), whilst the shaping device and the filter string and shifter string preferably remain static relative to the target volume, or.
- a combination of the foregoing options.
the one or more processors are preferably configured for:
- moving the filter rows and the shifter rows along the Y-axis to yield a sequence of filter modules forming an ith filter string and of an ith shifter string extending along the X-axis to yield an ith radiation string according to a predefined treatment plan, such that the beam paths of the pencil beams (Bj) of an ith scanning string traverse corresponding radiation modules of the sequence of radiation modules forming the ith radiation string (32i) before attaining the target volume (Vt), wherein a radiation module is formed by a filter module and a shifter module aligned along the irradiation axis (Z),
- controlling the electromagnetic elements (4) for orienting the pencil beam (Bj) through a first radiation module formed by a first filter module (12) of the ith filter string and a first shifter module of the ith shifter string, and towards a first spot (Sj) of an ith scanning string formed by a sequence of spots (Sj) distributed along the X-axis, the spots being arranged in a plurality of scanning strings (i, i+1 . . . ) distributed along the Y-axis to define an array of spots arranged on a plane (X, Y) representative of a projection onto the plane (X, Y) of the treatment volume (Vt),
- after the pencil beam (Bj) traversing the first spot (Sj) of the ith scanning string delivered a predefined dose (Dj), the electromagnetic elements are controlled for sequentially orienting the pencil beams (Bj) of the ith scanning string through the sequence of radiation modules forming the ith radiation string (32i), and towards the sequence of spots (Sj) of the ith scanning string,
- for all filter modules forming the ith filter string and for all shifter modules forming the ith shifter string, after the pencil beam (Bj) has traversed an xth radiation module and moves to a next (x+1)th radiation module along the X-axis, moving along the Y-axis the jth filter row and the xth shifter row to yield the radiation module (32) required for irradiating the xth radiation module of the next (i+1)th radiation string required for irradiating a next (i+1)th scanning string of spots (Sj) according to the predefined treatment.
In an embodiment of the present disclosure, after the pencil beam (Bj) traversing a last spot (Sj) of the ith scanning string delivered a predefined dose (Dj) into a corresponding last specific volume (Vj), the one or more processors are configured for,
- controlling the electromagnetic elements or the translation system of the couch as defined supra for orienting the pencil beam (Bj) through a first spot of an (i+1)th scanning string adjacent along the Y-axis to the ith scanning string, and
- repeating the foregoing steps for the spots on the (i+1)th scanning string,
- repeating the foregoing steps for all of the plurality of scanning strings forming the array of spots (Sj) which have not yet received the dose according to the predefined treatment plan.
In an embodiment, the couch is static and, to ensure that the beam paths followed by the pencil beams (Bj) always cross a corresponding filter module of the filter string and a corresponding shifter module of the shifter string, the one or more processors are configured for synchronizing the electromagnetic elements and
- the translation system of the shaping device for ensuring that as the pencil beam is deviated along the Y-axis, the shaping device or the radiation string is also translated along the Y-axis, or
- a moving of the filter string and the shifter string along the Y-axis relative to the shaping device which remains static relative to the target volume (Vt), in order to keep in alignment with the pencil beam along the Y-axis.
BRIEF DESCRIPTION OF THE FIGURES
For a fuller understanding of the nature of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1(a) shows pencil beams irradiating a target volume after passing through a range shifter and a ridge filter to define SOBP's matching the dose deposition pattern onto the target volume as defined in a treatment plan.
FIG. 1(b) shows a spot pattern on plane P0, defining the positions of the different pencil beams.
FIGS. 1(c)&1(d) show two examples of SOBP's defining the dose within two specific volumes as desposited by pencil beams Bi and Bm, respectively, as defined in FIG. 1(a).
FIG. 2(a) shows a simplified view of the depth dose deposition around a typical Bragg peak of a mono-energetic beam of given energy. The abscissa axis represents the depth in water. The maximum beam range (W0) in water is defined as the depth beyond the maximum of the Bragg peak and corresponding to an energy equal to 80% of the maximum of the Bragg peak, wherein W0 must be at least equal to or larger than dj (dj<W0).
FIG. 2(b) shows the depth dose profile of the Bragg peak of the beam of FIG. 2(a) with an energy shifting unit intersecting the path of the beam.
FIGS. 2(c) to 2(e) show the effect of one or more spreading units on the construction of a SOBP of desired shape.
FIG. 3(a) shows an example of sequence of spots irradiated by successive pencil beams.
FIG. 3(b) shows an example of monolithic manufactured ridge filter and range shifter of the prior art interposed between a source of irradiation and a target volume.
FIG. 3(c) schematically shows the SOBP's obtained by pencil beams successively irradiating a series of spots aligned along the X-axis, with the corresponding dose deposition distributions formed by intersecting Gaussian distribution curves.
FIGS. 4(a)&4(b) show perspective views of a single row of a dynamic ridge filter and of a dynamic range shifter, respectively, according to the present disclosure, each formed by a succession of modules of standard dimensions aligned along the Y-axis.
FIG. 4(c) shows side views of the single rows of a dynamic ridge filter and of a dynamic range shifter of FIGS. 4(a) and 4(b) forming in combination of dynamic shaping device.
FIGS. 5(a)&5(b) show an irradiation treatment station comprising a dynamic shaping device according to the present disclosure.
FIGS. 6(a)&6(b) show the example of FIGS. 3(b)&3(c) with the monolithic ridge filter and range shifter of the prior art replaced by a dynamic ridge filter and range shifter according to the present disclosure. The resulting SOBP's illustrated in FIGS. 3(c) and 6(b) are identical.
FIGS. 7(a)&7(b) show the required sequence of energy spreading units forming sequential filter strings for treating a given target volume, wherein the codes A, B . . . are defined in FIG. 7(b).
FIG. 7(c) shows the required sequence of shifter modules forming sequential shifter strings for treating a given target volume, wherein the codes a, b . . . are defined in FIGS. 7(d) & 7(e).
FIGS. 7(d) & 7(e) show two embodiments of range shifters defining the codes a, b . . . indicated in FIG. 7(c). The range shifter of FIG. 7(d) is formed of discrete modules of constant thickness, whereas the range shifter of FIG. 7(e) has a continuous slope, with the boundaries of the modules a, b, . . . being defined by the diameter of the pencil beam.
FIGS. 7(f)&7(g) show the required sequence of energy spreading units and shifter modules of the dynamic range shifter forming sequential radiation strings for treating a given target volume with a combination [Ba] to be applied to the spot (i, j) in FIG. 7(f), wherein the codes Aa, Bb . . . are defined in FIG. 7(f).
FIGS. 8(a) to 8(d) show the translation of rows as the pencil beams successively pass from one spot to the next one along a first scanning string parallel to the X-axis.
FIGS. 9(a) to 9(d) show the translation of rows as the pencil beams successively pass from one spot to the next one along a second scanning string parallel to the X-axis.
FIG. 10(a) to 10(e) show different embodiments of ridge filter modules.
FIGS. 11(a) to 11d) show different embodiments of ridge filter modules, with energy spreading units formed by a superposition of various energy spreading subunits.
FIG. 12(a) to 12(c) show different spots irradiation sequences along both X-axis and Y-axes.
FIGS. 13(a) & 13(b) schematically show an irradiation station wherein the nozzle is configured for scanning the pencil beams along both X- and Y-axes, and wherein the shaping device is configured to translate along the Y-axes to maintain the scanning string aligned with the pencil beams as they shift along the Y-axis.
FIGS. 14(a) & 14(b) schematically show an irradiation station wherein the nozzle is configured for scanning the pencil beams along both X- and Y-axes, and wherein the shaping device is configured for translating the radiation string along the Y-axes to maintain it aligned with the pencil beams as they shift along the Y-axis.
FIGS. 15(a) & 15(b) schematically show an irradiation station wherein the nozzle is configured for scanning the pencil beams along the X-axis, and wherein the couch is configured to translate along the Y-axis to allow the target volume to be scanned along the Y-axis by the pencil beams.
DETAILED DESCRIPTION
The present disclosure concerns a dynamic shaping device (30) that can be re-used and re-configured to shape the SOBP's of pencil beams matching the dose deposition patterns defined by treatment plans for the treatment of target volumes (Vt) of different geometries. A target area (At) is defined by projecting the target volume (Vt) onto a plane P0 defined by an X-axis and a Y-axis perpendicular to a central irradiation axis (Z). An array of spots (Sj) is defined, distributed on the plane (P0) covering at least the whole of the target area (At) as illustrated in FIGS. 1(b), 3(a), and 12(a) to 12(c). The dynamic shaping device (30) of the present disclosure comprises a dynamic ridge filter (1) and/or a dynamic range shifter (2).
Ridge Filter (1)
The dynamic ridge filter (1) of the present disclosure is configured for shaping a dose deposition zone by radiation with charged particles pencil beams, preferably with proton pencil beams, and for depositing doses (Dj) applied by pencil beams (Bj) propagating along corresponding irradiation axes (Zj) fanning out of a central irradiation axis (Z) with a pencil beam scanning (PBS) system. The pencil beams are delivered into a sequence of specific volumes (Vj) along an X-axis to form specific volume stripes, which are distributed next to one another along a Y-axis transverse, preferably normal, to the X-axis. The specific volumes (Vj) define in combination the target volume (Vt) comprising the tumoral cells.
The dynamic ridge filter (1) comprises a number of energy spreading units (11), each energy spreading unit (11) being characterized by a corresponding energy spreading capacity for spreading the dose deposited along the irradiation axis (Zj) by the corresponding pencil beams (Bj) traversing one or more energy spreading units (11).
The gist of the present disclosure is that the ridge filter is dynamic, in that a topography of the ridge filter can be varied according to the requirements of the treatment plan. This result is achieved as follows. The energy spreading units (11) are distributed in filter modules (12). Each filter module (12) supports one or more energy spreading units (11) and has an area normal to the central irradiation axis (Z) compatible with a cross-sectional diameter (D100) of the corresponding pencil beam (Bj). As shown in FIGS. 4(a) and 4(c), the filter modules (12) are arranged in different filter rows (10), each extending along the row-direction (Y). Each filter row (10) comprises a number of dissimilar filter modules (12), each filter module of a filter row (10) having a different energy spreading capacity than the other filter modules (12) of the same filter row (10).
The ridge filter of the present disclosure is dynamic because each filter row can be displaced independently to form a filter string (12i) along the X-axis as shown in FIG. 6(a). With this construction, the filter string is configured to shape the dose deposition in the specific volumes (Vj) forming the specific volume stripe facing the filter string along the irradiation axes (Zj).
All filter rows (10) are preferably identical to one another and comprise a same selection of filter modules (12). Each module is to the filter string (12i) what letters are to a word. They can be combined in different arrangements to define different “words”. As shown in FIGS. 6(a) and 6(b), each module (12) preferably has dimensions of the same order of magnitude as the diameter (D100) of the pencil beams.
Energy Spreading Units (11)
Each filter module (12) comprises one or more energy spreading units (11) supported on a base of the filter modules (12). As shown in FIGS. 2(a) and 2(b), by interposing an energy spreading unit (11) on the path of a hadron beam, the energy thereof can be controlled for shortening the propagation distance thereof through a body (e.g., water or tissues of a patient). It is thus possible to displace the position of the Bragg Peak of hadron particles where the full dose (Dj) of each particle is deposited, without varying the energy of the hadron beam emitted out of the nozzle (3). FIGS. 2(c) to 2(e) show how the positions of the Bragg peaks of one or more pencil beam can be controlled by passing them through different embodiments of energy spreading units (11). A pencil beam (Bj) has a diameter (D100), which can be defined, e.g., as a function of the variance of the Gaussian distribution of particles of the pencil beam (Bj) (for example, in FIGS. 2(c) to 2(e), D100=4σ, wherein σ2 is the variance of the Gaussian distribution). If the pencil beam traverses different thicknesses of the material forming the energy spreading units (11), as many different Bragg peaks are obtained which, put together form an SOBP. By calculating precisely the contribution of each shifted pencil beam, a smooth SOBP can be obtained.
In an embodiment shown in FIGS. 10(b) and 10(c), the energy spreading units (11) can be in the form of spikes of generalized cylindrical, preferably prismatic geometry. A generalized cylindrical geometry is defined by parallel lines (=a generatrix) passing by the perimeter of a planar base of any geometry, preferably albeit not necessarily circular. A prismatic geometry is herein defined as a cylindrical geometry whose planar base is polygonal. Alternatively, as shown in FIGS. 10(d) and 10(e), the energy spreading units (11) can have a conical geometry, truncated or not, preferably a pyramidal geometry. A conical geometry is defined by straight lines passing by an apex and by the perimeter of a planar base of any geometry, preferably albeit not necessarily circular. A pyramidal geometry is a conical geometry whose planar base is polygonal.
As shown in FIGS. 5(a) and 5(b), the pencil beams (Bj) exit out of a nozzle (3) which can be considered as forming the apex of a scanning triangle in a (X, Z) plane and of a scanning cone whose base encloses at least the target area (At) on the patient 6, depending on whether the electromagnetic elements (4) are configured for deviating the pencil beams (Bj) along the X-axis only or along both X- and Y-axes. The central irradiation axis (Z) is defined by the axial axis of the nozzle. In the case of scanning along both X- and Y-axes, the pencil beams can scan within the scanning cone and thus cover the whole target area (At). If the tumour is too large to allow the beamlets to scan over the whole corresponding target area (At), the irradiation session must be carried out in two or more stages, including moving the nozzle to cover the whole target area. Since the distance of the nozzle to the plane (P0) is substantially larger than a diameter of the target area (At), the pencil beams (Bj) can be approximated to be about parallel to the central irradiation axis (Z), albeit this is not strictly true, because of the aperture of the scanning cone. This aperture is, however, very small and the irradiation axes (Zj) can be considered as approximately parallel to the central irradiation axis (Z). This issue is well known to the skilled person. For sake of clarity and conciseness, in continuation, it is approximated that the irradiation axes are parallel to the central irradiations axis (Z).
In an alternative embodiment illustrated in FIG. 10(a), the energy spreading units (11) can be in the form of orifices of generalized cylindrical or conical geometry penetrating in a support base of the filter modules (12). Each orifice extends from an aperture opening at a surface of the support base and penetrating to a given depth leaving a resulting thickness of material of the support base. As for the spikes discussed supra, it is preferred that the orifices be configured in use for having a major axis of the cavities extending parallel to the corresponding irradiation axes (Zj).
As illustrated in FIGS. 11(a) to 11(d), each filter module (12) can comprise one or more energy spreading units (11), each formed by a plurality of spreading subunits (11a-11c) having differing cross-sectional areas (Ai) normal to the irradiation axis (Zj). The spreading subunits (11a-11c) are stacked on top of one another along a major axis of the energy spreading unit (11) configured in use for extending parallel to the irradiation axis (Zj). By using energy spreading units formed by stacking spreading subunits (11a-11c) having different energy spreading capacities, a corresponding SOBP can be defined as described in EP2021/208699.
Dynamic Range Shifter (2)
The dynamic shaping device (30) of the present disclosure also includes a range shifter (2) configured for shaping a dose deposition zone by radiation with charged particles beams, preferably with proton beams, and for depositing doses (Dj) applied by pencil beams (Bj) propagating along corresponding irradiation axes (Zj) fanning out of a central irradiation axis (Z) with a pencil beam scanning (PBS) system and delivered into a sequence of specific volumes (Vj) along a X-axis to form specific volume stripes distributed next to one another along a Y-axis transverse, preferably normal, to the X-axis. The specific volumes (Vj) define in combination the target volume (Vt) comprising the tumoral cells.
The range shifter (2) has a thickness of material measured along the central irradiation axis (Z) which varies over an area of the range shifter (2). In use, the area is preferably planar and preferably configured for being substantially normal to the corresponding irradiation axes (Zj). The thickness of range shifting material determines the corresponding amount of absorbed energy (ΔE) of the pencil beam (Bj) of the charged particles traversing the thickness
The gist of the present disclosure is that the range shifter (2) is dynamic, in that a topographic thickness of the range shifter can be varied according to the requirements of the treatment plan. This result is achieved as follows. The range shifter comprises shifter modules (22) arranged side by side to form shifter rows (20), as illustrated in FIG. 4(b). Each shifter row (20) comprises a selection of shifter modules (22) having a constant thickness different from the other shifter modules (22) of the same shifter row (20) and configured for absorbing different amounts of energy (ΔE) from the pencil beam (Bj).
As shown in FIG. 6(a), all shifter rows (20) can be displaced independently to form a shifter string (22i) along the X-axis. As shown in FIG. 6(b), the shifter string is configured to shape along the irradiation axes (Zj) the dose deposition in the specific volumes (Vj) forming the specific volume stripe facing the shifter string along the irradiation axes (Zj). In particular, the range shifter defines the geometry of the furthest downstream end of the dose deposition profile.
All shifter rows (20) are preferably identical and comprise a same selection of shifter modules (22). Each shifter module is formed by a plate of preferably constant thickness and of dimensions on the plane (X, Y) of the same order of magnitude as the pencil beam diameter (D100) and as the filter modules (12).
Dynamic Shaping Device (30) and Treatment Station
As shown in FIGS. 5(a)&5(b) and 6(a)&6(b), the combination of at least a dynamic ridge filter (1) as defined supra and at least a dynamic range shifter (2) as defined supra. disposed in a sequence along a beam path of a pencil beam (Bj) forms a dynamic shaping device (30). The dynamic ridge filter (1) and range filter (2) are superimposed such that the filter string (12i) and the shifter string (22i) face each other along a direction, which in use is parallel the irradiation axis (Zj), to form in combination a radiation string (32i). This is illustrated in FIG. 6(a) with the shaded filter string (12i) and shifter string (22i).
The ridge filter (1) can indifferently be positioned upstream or downstream of the range shifter (2) relative to the particles flow direction. The filter rows (10) and shifter rows (20) must be translated along the Y-axis such as to bring the right sequence of filter modules (12) and shifter modules (22) aligned along the X-axis to define the required radiation string (32i) matching the dose deposition pattern onto the corresponding specific volume stripe as defined in the treatment plan. The filter rows (10) and shifter rows (20) must be translated again to define the required radiation string (32i) matching the dose deposition pattern onto a next corresponding specific volume stripe adjacent to the first one along the Y-axis, as defined in the treatment plan.
The present disclosure also concerns a treatment station for shaping a dose deposition zone by radiation with charged particles beams, preferably with proton beams, and for depositing doses (Dj) applied by pencil beams (Bj) propagating along corresponding irradiation axes (Zj) fanning out of a central irradiation axis (Z) with a pencil beam scanning (PBS) system and delivered into a sequence of specific volumes (Vj) along a X-axis to form specific volume stripes distributed next to one another along a Y-axis transverse, preferably normal, to the X-axis, the specific volumes (Vj) defining in combination a target volume (Vt) comprising the tumoral cells. As illustrated in FIGS. 5(a) and 5(b), the treatment station comprises,
- a source of pencil beams (Bj) of accelerated charged particles, preferably of protons, and
- a nozzle (3) for directing the pencil beams (Bj) of accelerated charged particles towards the target volume (Vt), the nozzle comprising electromagnetic elements (4) configured for deviating the pencil beam (Bj) to scan along at least the X-axis as the nozzle remains static, and
- a couch (5) for receiving the patient (6), and
- a dynamic ridge filter according to the present disclosure, and/or
- a range shifter (2) according to the present disclosure, and
- one or more processors configured for controlling various components of the treatment station,
Preferably, the treatment station comprises both dynamic ridge filter (1) and dynamic range shifter (2) according to the present disclosure and are aligned such that the filter string (12i) and the shifter string (22i) face each other along a direction, which in use is parallel the irradiation axis (Zj), to form in combination a radiation string (32i).
Use of the Treatment Station
The PBS system is configured for pointing a pencil beam (Bj) over each spot (Sj) in a given sequence. The spot sequence is preferably composed of a series of scans along the X-axis repeated over i=1 to m radiation strings (32i) distributed along the Y-axis. As moving the nozzle is most time consuming, it is preferred to carry out a whole portion of a radiation sequence with the nozzle (3) remaining static. As shown in FIGS. 5(a)&5(b) and 13(a)&13(b) to 15(a)&15(b), the nozzle (3) is provided with electromagnetic elements (4) configured for deviating the pencil beams (Bj) at least along the X-axis, preferably along both X-axis and Y-axis.
To carry out a radiation treatment session with a radiation station according to the present disclosure, the one or more processors can be configured for controlling the actions illustrated in FIGS. 7(a), 7(c), 7(f), 8(a) to 8(d) and 9(a) to 9(d) discussed in continuation.
FIG. 7(a) shows an example of a spot pattern covering a target area (At), with a series of filter strings (12i) for different positions (i=1 to . . . ) along the Y-axis. The letters A, B, C, D refer to a specific filter module (12) as defined in FIG. 7(b). FIG. 7(c) shows the same spot pattern as in FIG. 7(a), with series of shifter strings (22i) for different positions (i=1 to . . . ) along the Y-axis, wherein the letters a, b, c, . . . refer to specific shifter modules (22) as defined in FIGS. 7(d) and 7(e). As shown in FIGS. 4(b), 4(c), 6(a), and 7(d), the shifter row (20) is preferably formed of discrete shifter modules (22) each of substantially constant thickness. In alternative embodiments, the shifter row (20) can have a continuous slope as illustrated in FIG. 7(e). The size of a shifter module is defined by the diameter of the pencil beam (Bj) as can be deduced from FIG. 7(g). A radiation string (32i) is formed by the combination of a filter string (12i) and a shifter string (22i) as shown in FIG. 7(f). A radiation module (32) is obtained by sliding along the Y-axis each filter row (10) and shifter row (20) of the dynamic shaping device (30) to align the required filter modules (12) and shifter modules (22) with the corresponding pencil beams (Bj). In FIGS. 7(a) and 7(c), the modules of a filter row (10) are identified by letters A, B, C, D and the ones of a shifter row are identified by letters, a, b, c, d. The radiation modules (32) can be formed by any combinations of the filter modules (12) and shifter modules (22), with a total of 16 combinations Aa, Ab, Ac, Ad, Ba, Bb, Bc . . . For example, FIG. 7(g) shows the alignment of the filter row (10) and shifter row (20) to align filter module (12=B) with shifter module (22=a) to yield the radiation module (32=[Ba]) required at spot (Sj) located at (i, j) in FIG. 7(f).
As shown in FIG. 8(a), the filter rows (10) and the shifter rows (20) are moved independently along the Y-axis to yield a sequence of filter modules (12) and shifter modules (22) forming in combination an ith radiation string (32i) composed of an ith filter string (12i) and of an ith shifter string (22i) along the X-axis according to a predefined treatment plan illustrated in FIGS. 7(a), 7(c), and 7(f).
The beam paths of the pencil beams (Bj) of an ith scanning string sequentially traverse the corresponding radiation modules (32) of the ith radiation string (32i) before attaining the target volume (Vt). This corresponds to any one sequence defined in line i, i+1, i+2 . . . in FIG. 7(f).
The electromagnetic elements (4) are controlled for orienting the pencil beam (Bj) through a first filter module (12) of the ith filter string (12i) and through a first shifter module (22) of the ith shifter string (22i), and towards a first spot (Sj) of the ith scanning string formed by a sequence of spots (Sj) distributed along the X-axis. After the pencil beam (Bj) traversing the first spot (Sj) of the ith scanning string delivered a predefined dose (Dj), the electromagnetic elements (4) are controlled for sequentially orienting the pencil beams (Bj) of the ith scanning string through each one of the sequence of filter modules (12) forming the ith filter string and through each one of the sequence of shifter modules (22) forming the ith shifter string, and towards the sequence of spots (Sj) of the ith scanning string. As shown in FIG. 8(a), the radiation sequence starts by pointing a jth pencil beam (Bj) to a jth spot (Sj) on the ith scanning string (i) of spots distributed along the X-axis. The radiation string (32i) formed by a combination of the filter string (12i) and the shifter string (22i) is defined by the ith scanning string (32i)=[Ba]-[Cb]-[Db]-[Aa] illustrated in FIG. 7(f). The jth pencil beam (Bj) passes through the radiation module (12)=[Ba] to deposit a first predefined fraction of the dose (Dj) to be deposited onto the specific volume (vi) associated with the jth spot (Sj). As shown in FIGS. 8(b) to 8(d), the electromagnetic elements (4) are activated to deviate the pencil beam towards a (i+1)th spot (S(j+1)) adjacent to the jthspot (Sj) along the X-axis. As the (j+1)th pencil beam passes trough the radiation module (32)=[Cb] a first predefined fraction of the dose (Dj) is deposited onto the specific volume (vi) associated with the (j+1)th spot (Sj). During this time, the previous filter row (12) and shifter row (22) facing the first spot (Sj) are translated to bring the radiation module (32)=[Cb] as defined in FIG. 7(f) for the first spot of the (i+1)th scanning string adjacent to the ith scanning string along the Y-axis.
These operations are repeated for each spot of the ith filter string (12i) until the last spot (S(j+3)) thereof is irradiated by a (j+3)th pencil beam (B(j+3)), to deposit a first predefined fraction of the dose (Dj) to be deposited onto the specific volume (vi) associated with the (j+3)th spot (S(j+3)). Each time, after a spot of the ith scanning string was irradiated, the filter row (10) and shifter row (20) facing the last irradiated spot are translated to bring the radiation module (32) as defined in FIG. 7(f).
The next pencil beam is oriented towards a first spot of a next scanning string (i+1) of spots. This can be achieved in different manners described below with reference to FIGS. 13(a)&13(b) to 15(a)&15(b). The previous steps are repeated for all the spots aligned along the (i+1)th string as shown in FIGS. 9(a) to 9(d). And so on, until all spots aligned along all scanning strings (i, i+1 . . . ) extending along the X-axis and distributed along the Y-axis have been irradiated. Moving the filter rows (10) (and shifter rows (20)) to their respective positions required by the corresponding spot of the next scanning string as soon as the corresponding spot has been irradiated is advantageous in that the shaping device (30) is sequentially modifying the radiation string (32i) for the radiation string required for shaping the pencil beams pointed at the spots of the next scanning string. This way, the flow of accelerated particles needs not be interrupted until the new radiation string has been formed before starting scanning along an (i+1)th scanning string. This is illustrated by comparing FIGS. 8(a) to 8(d) showing the ith radiation string [Ba]-[Cb]-[Db]-[Aa] with FIGS. 9(a) to 9(d) showing the (i+1)th scanning string [Cb]-[Ac]-[Cd]-[Bb] as defined in FIG. 7(f), ready for irradiating the target volume along the (i+1)th scanning string. When the jth spot (Sj) of the ith scanning string has been irradiated through the radiation string (32)=[Aa], the one or more processing units control the electromagnetic elements (4) to move the beam (Bj) to the (j+1)th spot (S(j+1)) and control the dynamic shaping device (30) to move the xth filter row (10) and the xth shifting row (20) along the Y-axis, such as to align the filter and shifting modules (12, 22) to yield the radiation module (32)=[Cb] required for the jth spot of the (i+1)th scanning string as defined in FIG. 7(f). The same process is applied after a dose has been deposited in the specific volumes associated with each successive spot (Sj, S(j+1), . . . ) of the ith scanning string.
Passing from an ith to an (i+1)th Scanning String
FIGS. 12(a) to 12(c) show three possible embodiments of spots irradiation sequences, all including a scan comprising at least a component along the X-axis. FIG. 12(a) illustrates a reading sequence wherein as a scan along the X-axis is completed, the pencil beam is returned to the initial position one string below, as when reading a document. Alternatively, FIG. 12(b) illustrates a scarf-sequence wherein as a scan along the X-axis is completed, the pencil beam jumps to the closest spot located on the next string. The choice between the reading sequence or the scarf sequence depends on many parameters which extend beyond the scope of the present disclosure, including the geometry of the target volume, the position of the spots to be irradiated at ultra-high dose deposition rates, the performance of the source of accelerated particles, the performance of the scanning system, and the like.
FIG. 12(c) shows a reading sequence obtained when the couch (5) supporting the patient (6) translates along the Y-axis. The combination of the scanning of the pencil beam along the X-axis at an X-rate (vx) and the translation of the couch (5) and patient (6) along the Y-axis at a couch rate (v5, with vx>>v5) yields a scanning direction (xs) at a resulting scanning rate (vs=(vx2+v52)1/2). The angle formed by the scanning direction (xs) with the X-axis illustrated in FIG. 12(c) is therefore largely exaggerated. Note that the return rate (vr) from the last spot of a given scanning string to the first spot of a next scanning string is much higher than the X-rate (vx).
Scanning from spot to spot along a scanning string parallel to the X-axis is controlled by the electromagnetic elements (4) at the level of the nozzle (3). Passing from an ith scanning string to an (i+1)th scanning string can be carried out in different ways illustrated in FIGS. 13(a)&13(b) to 15(a)&15(b).
In a first embodiment illustrated in FIGS. 13(a)&13(b) and 14(a)&14(b), to allow the whole of the target area (At) to be scanned by the pencil beams (Bj), the electromagnetic elements (4) are configured for deviating the pencil beam (Bj) to scan also along the Y-axis as the nozzle remains static. State of the art ridge filters and range shifters (i.e., non-dynamic) are designed to intercept the pencil beams (Bj) as they scan along both X- and Y-axes. This is not the case with the dynamic ridge filter (1), range shifter (2), and resulting shaping device (30) of the present disclosure, since only the modules aligned along the radiation string (32i) are arranged to yield SOBP's according to the treatment plan. As the pencil beams shift along the Y-axis they do not face the radiation string (32i) anymore. Two solutions are proposed to ensure that the pencil beams traverse the dynamic shaping device through the radiation string with the right arrangement of modules (12, 22) to yield the defined SOBP's over the whole target volume. Either the whole shaping device (30) moves along the Y-axis together with the radiation string (32i) and the pencil beams (Bj) or the radiation string (32i) moves relative to the shaping device (32) along the Y-axis with pencil beams (Bj).
FIGS. 13(a)&13(b) illustrate two scanning sequences at a first scanning string (i=1 in FIG. 13(a)) and a last scanning string (i=m in FIG. 13(b)). The electromagnetic elements (4) are configured to deviate the pencil beam (Bj) from the first (i=1) to the last (i=m) scanning strings. To ensure that the pencil beams traverse the radiation string (32i) for all scanning strings distributed along the Y-axis, the whole shaping device (30) can move along the Y-axis together with the pencil beams (Bj). The filter rows (10) and shifter rows (20) can be moved independently to ensure that the right arrangement of modules (12, 22) is present as a pencil beam (Bj) traverses the radiation string (32i) which is always aligned with the pencil beams (32i). This solution is quite straightforward and requires little processing power to coordinate the translations along the Y-axis of the shaping device (30) and of the pencil beams (Bj).
In an alternative solution illustrated in FIGS. 14(a) & 14(b) which, like FIGS. 13(a) and 13(b), show two scanning sequences at a first scanning string (i=1 in FIG. 14(a)) and a last scanning string (i=m in FIG. 14(b)). The electromagnetic elements (4) are configured to deviate the pencil beam (Bj) from the first (i=1) to the last (i=m) scanning strings. To ensure that the pencil beams traverse the radiation string (32i) for all scanning strings distributed along the Y-axis, the radiation string (32i) (illustrated with a rectangular window in FIGS. 13 to 15) moves relative to the shaping device along the Y-axis together with the deviation of the pencil beams (Bj) along a new scanning string. This is quite simple to achieve and requires little processing power to coordinate the movements of the filter/shifter rows (10, 20) to align the right arrangements of modules along radiations strings that move together with the pencil beams along the Y-axis.
In an alternative embodiment illustrated in FIGS. 15(a) and 15(b), the electromagnetic elements (4) do not deviate the pencil beams (Bj) along the Y-axis. The shaping device (30) does not move. The couch (5) supporting the patient (6), however, is provided with a translation system configured for translating the couch along the Y-axis to align the specific volumes (Vj) with the corresponding pencil beams (Bj). The movement of the couch (5) can be continuous at a couch rate (v5) or it can be sequential, moving only when the pencil beams are deviated along the Y-axis. It is preferred that the couch moves continuously at a couch rate (v5) yielding a scanning sequence as for example, illustrated in FIG. 13(c).
A combination of the solutions illustrated in FIGS. 13(a) & 13(b) to 15(a) & 15(b) can also be envisaged to ensure that the pencil beam traverse the right sequence of modules (12, 22) at each spot (Sj) covering the whole target area (At).
Advantages of the Disclosed Embodiments
The dynamic shaping device (30) of the present disclosure comprises a dynamic ridge filter and a dynamic range shifter comprising a number of filter rows (10) and a number of shifter rows, respectively. Each filter row is composed of a same selection of filter modules (12) of different energy spreading properties distributed along a length of the filter row parallel to the Y-axis. Similarly, each shifter row (20) is composed of a same selection of shifter modules (22) of different range shifting properties distributed along a length of the shifter row parallel to the Y-axis.
The filter rows and shifter rows can be translated along the Y-axis independently of one another to yield radiation modules (32) formed by a filter module and a shifter module aligned along a corresponding irradiation axis (Z). By translating the filter rows and shifter rows during scanning of the pencil beams, the dynamic shaping device (30) adapts dynamically to a predefined treatment plan.
The present disclosure is very advantageous over the prior art shaping devices because a single dynamic shaping device (30) according to the present disclosure can be used several times to treat different patients, or a same patient at different moments in time corresponding to different radiation sessions. The dynamic shaping device of the present disclosure can be adapted to match the treatment plans associated with the treatment of target volumes of different geometries. It can also be adapted for us with particles accelerators of different performance. Not having to manufacture a new ridge filter and a new range shifter before every radiation session is a substantial time saving factor.
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REF #
Feature
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|
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1
Dynamic ridge filter
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2
Dynamic range shifter
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3
Nozzle
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4
Electromagnetic element
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5
Couch
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6
Patient
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10
Filter row
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11
Energy degrading element
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11a-11c
Spreading subunit
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12
Filter module
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12i, i = 1 − k
Filter string
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20
Shifter row
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22
Shifter module
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22i, i = 1 − k
Shifter string
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30
Shaping device
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32
Radiation module
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32i, i = 1 − k
Radiation string
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Pz
Beam
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Si. j
Spot
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SOBP
Spread Out Bragg Peak
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Vt
Target volume
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X
X-axis defining the scanning direction
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Xs
Stripe direction
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Y
Y-axis defining the row direction
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Ys
Column direction
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Z
Direction normal to plane (X, Y)
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Zj
Irradiation axis
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Patent Application
20240285974
