JP4384897B2 - Phantom element and water phantom - Google Patents

Description

  The present invention relates to a phantom element and a water phantom. According to the water phantom of the present invention, it is possible to obtain a more accurate radiation dose than a conventional solid phantom when creating a treatment plan in radiation therapy.

  Radiation cancer treatment plays an important role in cancer therapy along with surgery and administration of anticancer drugs. Radiation therapy is not only advantageous in that it is a local treatment that treats only the cancer tissue and its surroundings, as is the case with surgical treatment, but it also eliminates the need for organ removal like surgery and preserves the organ. Excellent in terms. However, in order to achieve ideal radiotherapy, the cancer tissue is irradiated with the optimal radiation dose and damaged, while the surrounding normal tissue is irradiated with as little radiation as possible. To reduce damage.

For example, Intensity Modulated Radio Therapy (IMRT), which is one of the radiation therapies, is adapted to the position and shape of the cancer tissue of the patient being treated, and the shape of the radiation field and the radiation The incident direction is adjusted to irradiate the patient's cancer tissue with radiation, and the accumulated absorbed dose due to the radiation irradiation is optimized. Therefore, radiation therapy can be effectively performed by accurately concentrating the radiation on the affected area. When performing such IMRT, it is necessary to create a treatment plan first and set irradiation conditions that can accurately perform radiation irradiation with a predetermined absorbed dose distribution on the affected part. It is necessary to experimentally verify the validity of a proper treatment plan.
In this case, since it is impossible to insert a dosimeter into the human body and perform experimental dosimetry, a human body model composed of a human body equivalent substance, that is, a phantom is used. As a human body equivalent substance, dosimetry using water equivalent to muscle, which is the main tissue of the human body, is recommended (Non-Patent Document 1). However, since the contour of the human body is curved or has projections with complicated shapes such as ears and nose, it is curved in the same way as this, and it is a container having the outer shape of complex projections. Since filling with water without forming a void containing air, and positioning and loading the dosimeter accurately and carrying out dosimetry involves various difficulties, it has been equivalent to water in the past. Solid phantoms using a resin (water equivalent) have been used.

For example, FIG. 9 shows a solid phantom 6 formed by stacking a large number of plate-like solid phantoms. The solid phantom 6 is formed by stacking a plurality of plate-like phantoms 61 and passing a fixing bar (not shown) through a fixing bar hole 62 provided in each plate-like phantom 61. The photosensitive film 63 can be provided between desired positions. In the case of FIG. 9, the photosensitive film 63 can be provided between the plate-like phantom 61a and the plate-like phantom 61b. Since each plate-like phantom 61 has a predetermined accurate thickness (for example, 1 cm), the irradiation distance of radiation can be set accurately. The solid phantom thus formed is inserted into an outer solid phantom 4 shown in FIGS.
However, this solid phantom 6 has various drawbacks in addition to the use of resin instead of water. First, since an air layer exists between each plate-like phantom 61 and the adjacent plate-like phantoms 61, radiation passes through those air layers, which affects the accumulated absorbed dose in the photosensitive film 63. . Further, since radiation generates Cherenkov light when passing through the resin layer, its influence cannot be ignored.

On the other hand, water phantoms are also known (Patent Document 1 and Patent Document 2). However, each of the water phantoms described in Patent Document 1 and Patent Document 2 is provided with a movable radiation sensor inside a simple water tank, and the complicated outer shape of the human body is completely considered. Absent. There are also commercially available water phantoms, all of which are radiation phantom calibration phantoms, not water phantoms used to create a radiation treatment plan.
That is, a water phantom designed in consideration of the complex external shape of a human body when creating a radiation treatment plan has not been known at all.
Japanese Society of Medical Radiology Physics Subcommittee "Standard Measurement Method for Absorbed Dose of High Energy X-rays and Electrons in Radiation Therapy" 80-82, 1989, Tsusho Sangyo Kenkyusha JP-A-11-64530 JP 2003-47666 A

  Therefore, the problem of the present invention is that it can be used to create a radiation treatment plan instead of a conventional solid phantom that has been designed in consideration of the external shape of the human body for use in creating a radiation treatment plan. The object is to provide a water phantom that can be designed in consideration of the external shape of the human body.

The above problems are solved by the present invention.
(A) a columnar box that is open on the entire upper surface and can be filled with water, and (b) a lid that can seal the opening upper surface of the box in a state filled with water in a water-tight manner. ,
The columnar box has at least a pair of grooves extending in the axial direction of the columnar box on the inner side wall surface, and the axial direction is a direction of an axis extending from the lid to the columnar box, each of the pair of grooves, by inserting both ends of the water Seitaira shaped line amount measuring means, the water resistance tabular dosimetry means in a direction parallel to the axial direction of the columnar main body It can be solved by a phantom element, characterized in that it can be detachably mounted.

In a preferred embodiment of the phantom element of the present invention, a plurality of pairs of grooves to which a plurality of the water-resistant flat plate dose measuring means can be detachably attached are arranged at a predetermined interval.
In another preferred embodiment of the phantom elements of this invention, before Kifuta unit, or the side wall or the bottom of the front Symbol posts Jobako body, at least one perforated bubble outlet.

The present invention, before in the groove of the columnar main body of notated Antomu elements fitting the waterproof flat dosimetry means, said water-resistant flat dosimetry means mounted inside the columnar main body, and sealing the opening upper surface of the columnar main body by the lid portion inside of the columnar box body from completely filled with water in a watertight also relates to a water phantom.
In a preferred embodiment of the water phantom of the present invention, the water-resistant flat plate dose measuring means is a glass dose plate or a dose measuring film having a peripheral portion sandwiched between two frames, at least one of which has a central opening. is there.

Unlike the conventional solid phantom, the water phantom of the present invention uses water close to a living body, so that more accurate dose measurement can be performed. In the water phantom of the present invention, since there is no air layer formed between the plate-like phantoms in the conventional solid phantom, more accurate dose measurement can be performed. Furthermore, the water phantom of the present invention does not generate Cherenkov light that occurs in a conventional solid phantom.
As described above, since the water phantom of the present invention can perform more accurate dose measurement than the conventional solid phantom, it can be accurately combined with the recent development of radiotherapy equipment and the development of radiation biology and computers. A radiation treatment plan can be created, and as a result, it is possible to irradiate the cancer tissue with the optimum radiation dose, and to irradiate the surrounding normal tissue with as little radiation as possible, with few side effects. Radiation therapy can be realized.

Preferred embodiments of the phantom element according to the present invention and the water phantom of the present invention using the same will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view showing a state in which a water phantom 10 according to the present invention is mounted on an outer solid phantom 4, FIG. 2 is a perspective view showing a part thereof cut away, and FIG. 3 is an exploded view thereof. It is.
A phantom element 100 according to the present invention includes a cubic box 1 and a square lid 2 (see FIG. 3). The state in which the square dose measuring means 3 is inserted and inserted (inserted) into the inside of the storage chamber 15 of the cubic box 1 constituting the phantom element 100 is shown together with the square lid 2 in an unmounted state. 4 shows. Moreover, the dose measuring means 3 used in the embodiment shown in FIGS. 1 to 4 is a square type irradiation in which the peripheral part is sandwiched between two square type frames 32 and 35 as shown in FIG. 5 (disassembled perspective view). This is a dose measurement film 31. The frames 32 and 35 have square-shaped frame portions 34 and 37 and square-shaped opening windows 33 and 36 surrounded by them, respectively. The irradiation dose measuring film 31 is sandwiched between the frame portions 34 and 37. The four sides are fixed and exposed at the opening windows 33 and 36. Since it is sufficient that the central portion of the dose measuring film 31 on the side irradiated with radiation is exposed, the frame on the side irradiated with radiation has a square opening window as shown in FIG. It is also possible to use a square frame 32 having 33 and a frame having no opening window as the opposite frame. In the present invention, a fluorescent glass dose plate 3A can also be used as the dose measuring means 3, as shown in FIG.

  The cubic box 1 constituting the phantom element 100 according to the present invention has an open upper surface, and the dose measuring means 3 can be inserted and water can be filled from the upper surface opening. The cubic box 1 has at least a pair of grooves 11 extending in the axial direction of the cubic box 1 (the direction of the arrow X in FIGS. 3 and 4) on the surface of the opposing inner side wall. By inserting both end portions 30 </ b> A and 30 </ b> B of the water-resistant flat plate-shaped square dose measuring means 3 into each of the grooves 11, the square dose measuring means 3 is moved in the axial direction X of the cubic box 1. It can be detachably mounted in a parallel direction.

  The grooves 11 are provided on the surfaces of two opposing inner side walls of the cubic box 1, respectively. At this time, a predetermined interval (for example, 1 cm) is provided on the surfaces of the opposing inner side walls, and is provided over the entire length from the upper end (the point in contact with the upper surface) to the lower end (the point in contact with the bottom). Further, when the both side end portions 30A and 30B of the dose measuring means 3 are inserted into (inserted into) the pair of grooves 11 facing each other, the dose measuring means 3 has the remaining two sets of the two opposing inner portions. It is provided so as to be parallel to the side wall surface (inner side wall surface not provided with the groove 11). By providing a plurality of grooves 11 at the same interval on the two opposing inner side wall surfaces of the cubic box 1, the single dose measuring means 3 can be inserted into various positions, It is possible not only to perform dose measurement at the position, but also to perform dose measurement three-dimensionally by inserting a plurality of dose measurement means 3 simultaneously. Moreover, although the groove | channel 11 does not need to be provided in the inner surface of the bottom face of the cubic box 1, it can also be provided in the inner surface of the bottom face. Furthermore, not only two opposing inner side wall surfaces of the cubic box 1 but also another set of two opposing inner side wall surfaces can be provided with grooves.

  After the dose measuring means 3 is inserted into the cubic box 1, the inside of the accommodation chamber 15 of the cubic box 1 is filled with water, and then the cubic box 1 is filled with the square lid 2. Seal the upper surface of the opening in a watertight manner. For filling the water, the entire cubic box 1 having the dose measuring means 3 inserted therein is completely submerged in water in a water tank (not shown), and the interior of the storage chamber 15 of the cubic box 1 is water. From the through screw hole 23 for the bolt, which is covered with the square-shaped lid 2 in the water, covers the upper surface of the opening in the water, and is provided at an appropriate interval in the peripheral edge of the square-shaped lid 2. This can be done by passing bolts (not shown) through screw holes 13 provided at the upper edge of the box-like box 1 and tightening each bolt to seal it watertight. The bolt is preferably made of resin (non-metallic) because it does not affect radiation irradiation.

  For example, as shown in FIG. 4 (perspective view of the outer surface) and FIG. 7 (perspective view of the inner surface), the square lid 2 includes a base 21 that is exposed to the outside when watertightly sealed, and its base The center protrusion part 24 which protrudes in the center part of the inner surface of 21 and the rubber packing 22 as a shock absorbing material provided in the peripheral part of the center protrusion part 24 are included. The protrusion of the central protrusion 24 matches the shape of the upper inner wall surface of the storage chamber 15 of the cubic box 1, and the central protrusion 24 enters the storage chamber 15. By inserting the protruding portion of the central protruding portion 24 into the accommodating chamber 15 of the cubic columnar box 1, the dose measuring means 3 inserted into the accommodating chamber 15 of the cubic columnar box 1 is provided. It is preferable to fix from above. The rubber packing 22 matches the shape of the square exposed surface 17 on the upper surface of the cubic box 1. Accordingly, when the bolt passing through the screw hole 13 is tightened from the bolt through screw hole 23, the rubber packing 22 is tightened, so that the water filled in the storage chamber 15 of the cubic box 1 can leak out. Absent. Since the central projecting portion 24 enters the inside of the storage chamber 15 of the cubic box 1, the dimension of the square dose measuring means 3 is shortened by a length corresponding to the entering distance (strictly). Is a rectangular dose measuring means 3).

As shown in FIGS. 4 and 7, the square lid 2 can have a bubble outlet 26 and a plug 25 for closing the bubble outlet 26. After filling the inside of the storage chamber 15 of the cubic box 1 in the water tank and sealing it in a watertight manner with the square lid 2, bubbles may remain inside the storage chamber 15. The plug 25 can be opened in a state where it is completely immersed in water, and the air bubbles can be removed to the outside, followed by sealing again. The cubic box 1 is first completely immersed in the water in the water tank to fill the interior of the storage chamber 15, and then the dose measuring means 3 is inserted into the pair of grooves 11 (inserted). Then, it can be sealed watertight with the square lid 2.

  The water phantom 10 according to the present invention formed in a watertight manner with the square lid 2 is attached to the outer solid phantom 4 as shown in FIGS. The outer solid phantom 4 has a water phantom accommodating portion 41 inside thereof, and the outer surface is formed in the same shape as the outer shape of the human body. Moreover, it is preferable to provide the reference line 43 and the intersection 42 which become a visible mark in the case of performing radiation irradiation on the outer surface of the outer solid phantom 4.

  Irradiation is performed on the outer solid phantom 4 with the water phantom 10 included, and after the completion, the water phantom 10 is taken out, then the dose measuring means 3 is taken out, and the irradiation dose recorded in the dose measuring means 3 is measured. can do.

  In the water phantom or phantom element of the present invention, the external shape of the columnar box is not particularly limited. For example, the cubic box 1 shown in FIGS. 1 to 4 or a rectangular box, Alternatively, as shown in FIG. 8, it may be a cylindrical box 1A or an elliptic cylinder box. In FIG. 8, a state where the square or rectangular dose measuring means 3 is inserted and inserted into (inserted into) the cylindrical storage chamber 15 of the cylindrical box 1 </ b> A is an unmounted circular shape. Shown with lid 2A.

  When the columnar box used in the present invention is the cubic box 1 shown in FIGS. 1 to 4, the columnar box is rotated by 90 ° when attached to the water phantom accommodating portion 41 inside the outer solid phantom 4. Thus, the direction of the dose measuring means 3 inserted in the cubic box 1 can be rotated by 90 °. Further, when the columnar box used in the present invention is a cylindrical box 1A as shown in FIG. 8, when the columnar box is attached to the cylindrical water phantom accommodating portion 41 inside the outer solid phantom 4, The direction of the dose measuring means 3 inserted into the cylindrical box 1A can be rotated at an arbitrary angle by rotating at an angle.

  The outer shape of the outer solid phantom that houses the water phantom of the present invention is preferably formed in the same manner as the outer shape of the human body. As the material of the solid phantom, polystyrene (density = 1.05), acrylic resin (density = 1.18), or “Mid Dp” (density = paraffinic composition), which is conventionally used as a water equivalent, is used. 1.00; paraffin 50.0%, polyethylene 25.0%, pine yarn 16.2%, magnesium oxide 6.4%, titanium oxide 2.4%). Further, among the solid outer phantoms, a correction phantom, for example, polytetrafluoroethylene (density = 1.85) as a bone phantom, polyethylene (density = 0.93) as a fat phantom, or cork as a lung phantom (Density = 0.3-0.4) can also be contained.

  The radiation applied to the water phantom of the present invention is not particularly limited as long as it is radiation used for radiotherapy, and is an electromagnetic wave (for example, X-ray or γ-ray) or particle beam (for example, electron beam, proton beam, or neutron). Any of these may be used. Usually, X-rays, γ-rays, or electron beams are mainly used, and proton beams or heavy particle beams can also be used.

  In the water phantom of the present invention, the glass dose plate that can be used as a dose measuring means is preferably a fluorescent glass dose plate, which is made of, for example, silver activated phosphate glass. Silver activated phosphate glass has been widely used as a rod-shaped glass dosimeter. In the present invention, this silver activated phosphate glass can be formed into a flat plate shape. When silver activated phosphate glass is irradiated with radiation, free electrons and holes are generated, and these are captured by silver atoms to generate fluorescent centers. When the irradiated glass is excited by ultraviolet rays of about 320 nm, orange fluorescence is emitted. This phenomenon is called radio photoluminescence (RPL). The radiation dose can be measured by reading the emitted fluorescence with a reader. The RPL center is stored extremely stably for a long time and does not disappear by a reading operation. Furthermore, the accumulated dose can also be measured quantitatively. Further, when heating (annealing) at a high temperature (for example, about 400 ° C.), the fluorescence center disappears, and the radiation dose can be newly accumulated from the beginning.

  In the water phantom of the present invention, the irradiation dose measuring film that can be used as a dose measuring means includes, for example, an active layer between a transparent yellow polymer layer and an opaque white polymer layer (or transparent yellow polymer layer). It is a layer structure. The active layer contains, for example, a diacetylene monomer as a radiation active substance. When this active substance is irradiated with radiation, it is converted into a cyan blue polydiacetylene colorant by a solid phase polymerization reaction. The transparent yellow polymer layer and the white polymer layer (or transparent yellow polymer layer) disposed outside the active layer have a function of protecting the active layer from UV light and blue light, and a visible polydiacetylene colorant formed in the active layer. Has a function of improving the water resistance and a function of imparting water resistance. The irradiation dose measuring film does not contain silver particles, does not require a development process, and is not sensitive to normal indoor light, and thus can be used in a bright room. Furthermore, since the color develops immediately when irradiated with radiation, and the degree of color development is proportional to the irradiation dose, quantitative dose measurement is possible. A commercially available film for measuring radiation dose (GAFCHROMIC; manufactured by Nuclear Associates) has a composition close to that of the soft tissue of the human body, and no change in performance occurs even when immersed in water.

  As described above, the water phantom of the present invention is preferably irradiated with radiation while attached to the outer solid phantom. However, the water phantom should not be attached to the outer solid phantom, but should be used as a calibration phantom for the radiation generator. You can also. In this case, it is preferable to provide a reference line that becomes a visible mark and an intersection thereof on the outer surface of the columnar box and / or the lid when radiation irradiation is performed.

  The water phantom according to the present invention can be used when preparing a treatment plan in radiation therapy or as a calibration phantom of a radiation generator.

It is a perspective view which shows the state which mounted | wore the outer solid phantom with the water phantom of this invention. It is a perspective view which notches and shows a part of water phantom of FIG. It is a disassembled perspective view of the water phantom of FIG. It is a disassembled perspective view which shows the state which inserted the square type dose measuring means in the inside of the storage chamber of the cubic box body which comprises the phantom element of this invention with the square type cover part of a non-wearing state. It is a disassembled perspective view of the dose measurement means containing the film for irradiation dose measurement used with the water phantom of this invention. It is a perspective view of the fluorescent glass dose plate used as a dose measurement means with the water phantom of this invention. It is a perspective view of the inner surface of the square type cover part used with the water phantom of this invention. It is a disassembled perspective view which shows the state which inserted the square type dose measuring means in the inside of the storage chamber of the cylindrical box body which comprises the phantom element of this invention with the circular cover part of a non-wearing state. It is a perspective view of the solid phantom of the prior art formed by stacking many plate-shaped solid phantoms.

Explanation of symbols

1 ... Cubic box; 1A ... Cylinder box;
2 ... square lid; 2A ... circular lid;
3 ... dose measuring means; 3A ... fluorescent glass dose plate;
4 ... outer solid phantom; 6 ... solid phantom;
10 ... water phantom; 11 ... groove; 13 ... screw hole;
15 ... storage chamber; 17 ... square exposed surface;
21 ... base; 22 ... rubber packing;
23 ... Bolt through screw hole; 24 ... Center protrusion;
25 ... stopper; 26 ... bubble outlet; 30A, 30B ... both side ends;
31 ... Film for measuring radiation dose; 32, 35 ... Frame;
33, 36 ... opening window; 34, 37 ... frame part;
41 ... Water phantom housing part; 42 ... Intersection; 43 ... Reference line;
61, 61a, 61b ... plate-like phantoms;
62: fixing bar hole; 63 ... photosensitive film;
100 ... phantom element;
X ... Axial direction

Claims (5)

(A) a columnar box that is open on the entire upper surface and can be filled with water, and (b) a lid that can seal the opening upper surface of the box in a state filled with water in a water-tight manner. ,
The columnar box has at least a pair of grooves extending in the axial direction of the columnar box on the inner side wall surface, and the axial direction is a direction of an axis extending from the lid to the columnar box, each of the pair of grooves, by inserting both ends of the water Seitaira shaped line amount measuring means, the water resistance tabular dosimetry means in a direction parallel to the axial direction of the columnar main body A phantom element characterized by being detachably mounted.   2. The phantom element according to claim 1, wherein a plurality of pairs of grooves into which the plurality of water-resistant flat plate dose measuring means can be detachably mounted are arranged at a predetermined interval. Before Kifuta unit, or the side wall or the bottom of the front Symbol posts Jobako body, at least one perforated bubble outlet, phantom element according to claim 1 or 2. By fitting the waterproof flat dosimetry means to the groove of the columnar main body of the phantom element according to any one of claims 1 to 3, wherein the water-resistant flat dose inside the columnar main body the measuring means is mounted, and sealing the opening upper surface of the columnar main body in a watertight manner by the lid portion inside of the columnar box body from completely filled with water, the water phantom. Before Ki耐 aqueous tabular dosimetry means, glass dose plate, or at least one of which is dosimetry film sandwiched between two frames having a central opening, water phantom of claim 4.

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