JP6537470B2 - Calibration map, method for creating or updating calibration map, recording medium including calibration map, and dose verification method for radiation treatment plan - Google Patents

Description

  The present invention provides a calibration map of the optical density of a chromic film used in a radiation dose verification method of a radiation treatment plan, a method of creating or updating the calibration map, a recording medium containing the calibration map, and a radiation treatment plan using the calibration map. The present invention relates to a dose verification method.

  Cancer treatment with radiation plays an important role in cancer therapy, as well as surgery and anti-cancer drug administration. Radiation therapy, like surgery, is not only advantageous in that it is a local treatment that treats only the cancer tissue and its surroundings, but it also does not require organ removal like surgery and can preserve the organ It is excellent in point. However, in radiation therapy, it is necessary to irradiate a large amount of radiation to the lesion, so in order to reduce or prevent side effects, the cancer tissue is irradiated with an optimal radiation dose to cause damage, while the surrounding For normal tissue, it is required to minimize the radiation dose to minimize damage.

  For example, in intensity modulation therapy (IMRT), which is one type of radiation therapy, it is necessary to first create a treatment plan and set irradiation conditions that can accurately perform irradiation of a predetermined absorbed dose distribution to the affected area. Furthermore, the validity of such a treatment plan needs to be verified experimentally in advance. In this case, since it is not possible to insert a dosimeter inside the human body and perform experimental dosimetry, for example, insert a two-dimensional dosimeter into a human body model (that is, a phantom) composed of human equivalent materials. And analyze the dose distribution.

  For use in dose distribution analysis, a chromic film is widely used as a two-dimensional dosimeter inserted into a phantom. This chromic film has an advantage of forming a radiation image without development when exposed to X-rays. It becomes possible to acquire optical density data with an image scanner from the radiographic image obtained in this way, and to determine radiation exposure amount from the optical density data.

  In order to determine the radiation dose from the optical density data, it is necessary to create in advance a calibration curve (standard curve) of the optical density and the radiation dose. Since the chromic film is relatively expensive, its calibration curve is prepared, for example, by the following method. That is, radiation images are formed one after another with a plurality of radiation doses at a plurality of locations of one chromic film, the optical densities of the radiation images are read by a scanner, and calibration curves of the radiation doses and the optical densities are formed. can do.

  However, in the optical density data obtained by scanning a radiation image formed on a transmission type chromic film with a transmission type image scanner, it is reported that an error of the measured value occurs depending on the difference of the reading position. Means for correcting the error (non-flatness) generated in the direction perpendicular to the scanning direction have also been proposed (for example, Non-Patent Documents 1 and 2). Moreover, in the chromic film, the inclination of the trend component (non-flatness component) changes with the increase of the irradiation amount, so that the base component (background value) at the time of non-irradiation is simply subtracted from the trend component. It is also known that flat density information can not be obtained with respect to an illuminated image.

  As the cause of the error, unevenness of particles of photosensitive material in the chromic film, coating unevenness of photosensitive material for each lot, nonuniformity of the scanner light source, or displacement of the film position at the time of scanning are estimated. , The cause of the error has not been clarified yet. Further, in the above non-patent documents 1 and 2, errors (non-flatness) generated in the direction (scanning light source direction) perpendicular to the scanning direction are specifically pointed out, and it is complicated with respect to the error in one direction. A correction with an approximate polynomial has been proposed. However, there is no report quantitatively dealing with the presence of an error occurring in the other scanning direction or the error, and thus there is no quantitative report about the error in the entire two-dimensional plane. By the way, means for correcting these errors have not been proposed at all.

Uehara Ryuzo, et al., "An approach to improve the accuracy of radiochromic film dosimetry in dose distribution analysis-Combination of correction method of flatbed scanner effect and correction method using color component-", Japan Society for Radiation Technology Magazine, June 2013, Vol. 69, No. 6, p. Shigeyoshi Shibata, et al., "Improvement of flatness characteristics when using a Flat Bed scanner", [online], November 19, 2015, The 7th Gafchromic Film Study Group, [March 4, 2016] Search], Internet <URL: http://www.veritastk.co.jp/attached/5875/2_gafchromic. Pdf # search = 'flatbed% E5% 9E% 8B% E3% 82% B9% E3% 82% AD% E3% 83% A 3% E 3% 83% 8 A% E 4% BD% BF% E 7% 94% A 8 +% E 5% AE% AE% E 6% B 2% A 2 '>

  The inventor of the present invention measured the optical density of the transmission type chromic film uniformly irradiated on the entire surface with radiation, as shown in the following confirmation experiment, and the film on the scanner document table was measured. It was found that the measured value changes depending on the arrangement position and the arrangement direction of and the means for calibrating an error generated in the whole of the two-dimensional scanning plane, including the change in the measured value, was found.

  Accordingly, the object of the present invention is to provide a means for calibrating an error occurring in the whole of a two-dimensional scanning plane with respect to optical density data obtained by a transmission type image scanner from a radiation image formed on a transmission type chromic film The purpose is to improve the verification accuracy of radiation dose in radiation treatment planning.

The above problem is achieved by the present invention.
Regarding the radiation image formed on each of the transmission type chromic films belonging to the transmission type chromic film group considered to have the same physical properties, the actual radiation exposure dose to the transmission type chromic film from the optical density obtained by the transmission type image scanner A method of creating an original calibration map used to determine
(1) a step of selecting one non-irradiated standard film and at least two irradiated standard films as standard films from the transmission-type chromic film group considered to have the same physical properties as described above;
(2) For each of the above-mentioned irradiation standard films, the irradiation dose differs from one film to another, and in the case of each film, the entire surface is uniformly irradiated with the same radiation irradiation amount, Forming a radiation image on the
(3) obtaining optical density data for each pixel across the entire surface of the standard film from each of the standard films under the same scanning arrangement condition in the transmission type image scanner, and (4) the above From the optical density data obtained in step (3) and the radiation exposure data of each standard film, a calibration curve of optical density and radiation exposure is created in association with each pixel and recorded. , And can be solved by the method of creating an original calibration map described above.

Also, the present invention is
Although different physical properties are considered to be identical but different physical properties may be different from the physical properties of the transmissive chromic film group used to create the above-mentioned original calibration map, it was created by the above method A method of modifying an original calibration map to create an updated calibration map,
(1) A step of selecting one non-irradiated update film and at least one irradiated update film as update films from the different transmission type chromic films described above,
(2) The irradiation update films described above have different radiation doses among the respective films, and in the individual films, the entire surface is uniformly irradiated with the same radiation irradiation dose, and the irradiation update films are on each other. Forming a radiation image,
(3) acquiring optical density data for each pixel across the entire surface of the irradiated film from each of the update films under the same scanning arrangement conditions as the scanning arrangement conditions in the method of creating the original calibration map;
(4) From the optical density data obtained in the step (3) and the radiation exposure dose data of each irradiation film, a step of creating a corrected calibration curve of the optical density and the radiation exposure dose in association with each pixel. ,
(5) The method also relates to the method for creating an updated calibration map, including the step of updating the modified calibration curve created in the step (4) along the calibration curve of the original calibration map and recording the updated calibration curve.

  The invention also relates to a method of generating an updated calibration map, which further corrects said updated calibration map by said method of generating an updated calibration map.

Furthermore, the present invention
A method of updating the calibration map of a transmission image scanner different from the transmission image scanner used to create the calibration map (the original calibration map or the updated calibration map),
(1) selecting one non-irradiated update film and at least one irradiated update film as update films from the transmission-type chromic films used to create the calibration map;
(2) The irradiation update films described above have different radiation doses among the respective films, and in the individual films, the entire surface is uniformly irradiated with the same radiation irradiation dose, and the irradiation update films are on each other. Forming a radiation image,
(3) In the different transmission type image scanner described above, each of the updated films under the same scanning arrangement conditions as the scanning arrangement conditions in the method of creating the calibration map (the original calibration map or the updated calibration map) Acquiring optical density data for each pixel across the entire surface of the update film;
(4) From the optical density data obtained in the step (3) and the radiation exposure data of each updated film, a step of creating a corrected calibration curve of the optical density and the radiation exposure in association with each pixel. And (5) updating the modified calibration curve generated in the step (4) along the calibration curve of the calibration map to be updated, and recording the updated calibration curve. Also related.

  The invention also relates to a calibration map obtained by the method of creating a calibration map (original calibration map or updated calibration map) as described above.

Furthermore, the present invention is
Regarding the radiation image formed on each of the transmission type chromic films belonging to the transmission type chromic film group considered to have the same physical properties, the actual radiation exposure dose to the transmission type chromic film from the optical density obtained by the transmission type image scanner A calibration map used to determine
In each of the pixels across the entire surface of the transmissive chromic film, a plurality of irradiated radiation doses and an optical density measured by a transmissive image scanner from an image obtained by the irradiation of the radiation Having a calibration curve associated with each of the pixels across the entire surface of the film, and the radiographic image formed on the transmissive chromic film being measured by the transmissive image scanner at a predetermined specific scanning arrangement condition It also relates to the above calibration map, characterized in that it comprises a command of

  The invention also relates to a computer readable recording medium having the above calibration map (original calibration map or updated calibration map).

Furthermore, the present invention is
(1) A step of irradiating a therapeutic chromic film belonging to the transmissive chromic films belonging to the group of transmissive chromic films for which the above calibration map (original calibration map or updated calibration map) has been created to form a radiation image ,
(2) measuring an optical density from the radiation image formed on the transmission type chromic film by a transmission type image scanner under a predetermined specific scanning arrangement condition specific to the calibration map; and (3) the above The present invention also relates to a dose verification method for a radiation treatment plan, including the step of calculating a radiation dose from the optical density using the calibration map with respect to all pixels of a radiation image.

The calibration map according to the present invention comprises, independently of one another, a calibration curve (function) of the radiation image optical density of the chromic film and the radiation dose, for each of all the pixels covering the entire surface of the chromic film. Therefore, the new problem found by the present inventor (ie, the non-flatness generated based on the arrangement condition on the image scanner document table) is accurately corrected and used for the radiation dose verification method of the radiation treatment plan. The radiation dose corresponding to the optical density of the chromic film can be calibrated very accurately.
In addition, the calibration map according to the present invention can be implemented by a method that is extremely easy to generate and update, and the recording medium containing the calibration map, and further, the analysis system and analysis apparatus including the calibration map are also very easy. It can be manufactured.
Furthermore, the calibration map according to the invention can be used to verify the dose based on the radiation treatment plan very accurately.

It is explanatory drawing which shows each part, area | region, etc. of a transmission-type chromic film. FIG. 6 is an explanatory view schematically showing portions of a document table of the transmission type image scanner. It is a schematic diagram which shows the relationship between the preparation method of an original calibration map, and a calibration curve. It is a schematic diagram which shows the relationship between the preparation method of an update calibration map, and an update calibration curve. FIG. 5 (a) is an explanatory view showing four arrangement positions of the transmission type chromic film on the transmission type image scanner document table in the unevenness confirmation experiment of the optical density measurement value, and FIG. 5 (a) is an arrangement position in the first experiment. 5 (b) shows the arrangement position 2 rotated 90 ° from the arrangement position 1 of FIG. 5 (a), and FIG. 5 (c) further shows the arrangement position 2 of FIG. 5 (b). The arrangement position 3 rotated 90 degrees is shown, and FIG. 5 (d) shows the arrangement position 4 rotated 90 degrees further from the arrangement position 3 in FIG. 5 (c).

The film targeted by the present invention is a transmissive chromic film and does not include a reflective chromic film. Here, the transmission type means that the film transmits the light from the scanner light source (xenon lamp). Therefore, the scanner used in the present invention is also a transmission type image scanner. The scanner may be flat bed type or sheet feed type. In a flatbed scanner, a scanner light source (xenon lamp) and a CCD image sensor move across the top and bottom of a document table on which a chromic film is placed. In the sheet feed type, the chromic film passes while moving between a fixed scanner light source (xenon lamp) and a CCD image sensor.
In the present invention, the film is not limited as long as it is a transmissive chromic film, and the scanner is not limited as long as it is a transmissive image scanner.

  The calibration map according to the present invention includes an original calibration map and an updated calibration map. The original calibration map is a calibration map created by acquiring all the data for map creation from the beginning, and the updated calibration map uses data of the already created original calibration map and newly acquired data. Is a calibration map to be created. First, a method of creating an original calibration map will be described, followed by a method of creating an updated calibration map.

The method of creating an original calibration map includes the following steps.
(1) Standard film selection process,
(2) radiation image forming process,
(3) Optical density data acquisition process, and (4) Calibration curve recording process.

  In the standard film selection step, one non-irradiated standard film and at least two irradiated standard films are selected as standard films from the transmission-type chromic films which are considered to have the same physical properties. Here, the transmission-type chromic films whose physical properties are considered to be the same are, for example, films having the same production lot number. If the production lot number is the same, it is considered that the composition of the photosensitive material, the application / production conditions, the application unevenness, etc. are the same and the cutting direction is also aligned and packaged, so the films belonging to the film group have the same physical properties. Is considered to have.

  The non-irradiated standard film is used as a blank sample in the absence of irradiation and is necessary for obtaining data of the base component and the trend component in the non-irradiated state. It is necessary to select 2 or more sheets of the irradiation standard film which irradiates radiation, and usually 4 to about 7 sheets are selected. Since the maximum dose in a radiation treatment plan is generally about 200 cGy, the dose applied to the irradiation standard film is, for example, about 20 cGy (about 1/10 times the maximum dose) to about 400 cGy. A calibration map can be created by dividing the range of (approximately twice the maximum dose) at appropriate intervals. When six irradiated standard films are selected, the irradiated standard films are used for 25 cGy, 50 cGy, 100 cGy, 150 cGy, 200 cGy, and 350 cGy, for example.

  In the radiation image forming step, the entire irradiated standard film is uniformly irradiated with a predetermined amount of radiation and the entire surface is uniformly irradiated to form an image corresponding to each predetermined amount of radiation on the individual irradiated standard film. For example, when six irradiation standard films are selected as described above, the irradiation images of 25 cGy, 50 cGy, 100 cGy, 150 cGy, 200 cGy, and 350 cGy are uniformly irradiated on the entire surface of each irradiation standard film and the radiation image is Form on the entire surface of the irradiated standard film. Generally, the radiation dose verification of the radiation treatment plan is performed in the phantom, so the irradiation of the irradiation standard film is also the same condition in the same phantom as the phantom used for the radiation dose verification of the radiation treatment plan. It is preferred to carry out below.

  In the optical density data acquisition step, optical density data is acquired from each of the standard films under the same scanning arrangement conditions by a transmission type image scanner. Here, under the same scanning arrangement conditions, specifically, when the standard film is placed on the scanner document table, the placement position and the placement direction of each standard film should be completely the same. Means

Specific identical scanning arrangement conditions will be described with reference to FIGS. 1 and 2.
FIG. 1 is an explanatory view showing each portion, region, and the like of the transmission type chromic film 1, and FIG. 2 is an explanatory view schematically showing each portion of a document table 10 of the transmission type image scanner.
The film 1 shown in FIG. 1 has four sides S1 to S4 and four apex angles V1 to V4, and midpoints M1 to M4 exist on the sides S1 to S4, respectively. In addition, the whole surface of the film 1 is divided | segmented into division R1-R9 of nine equal areas for the facilities of description of the confirmation test mentioned later. The boundaries of these sections are imaginary lines not present in the film 1. Moreover, central regions r1 to r9 of the respective sections R1 to R9 are regions used in the unevenness confirmation experiment described later.
Further, in the scanner document table 10 shown in FIG. 2, as the scan area 11, the scan start end 12 to the end 13 in the scan direction indicated by the arrow X, and the scanner light source direction indicated by the arrow Y (and the CCD arrangement direction A region from the right end edge 15 to the left end edge 16 is prepared, and the scanning start end 12 has a right end corner RE and a left end corner LE, and a center marker CE is provided at the center thereof.

  In the optical density data acquisition step, the same setting direction of the standard films means that the film 1 is mounted on the scanner document table 10 in a predetermined predetermined direction. For example, the direction of the short sides S2 and S4 of the film 1 is parallel to the scanning direction (arrow X in FIG. 2), and one long side S3 of the film 1 is on the scanning start end 12 side of the scanner document table 10. By placing the other long side S1 of the film 1 on the end 13 side, it is possible to perform the operation of acquiring optical density data from all the standard films in the completely same direction. Further, for example, the direction of the long sides S1 and S3 of the film 1 is parallel to the scanning direction (arrow X in FIG. 2), and one short side S2 of the film 1 is the scanning start end 12 of the scanner document table 10. By placing it on the side and placing the other short side S4 of the film 1 on the end 13 side, it is possible to carry out the acquisition operation of the optical density data from all the standard films in the completely same direction.

  Furthermore, in the optical density data acquisition step, making the mounting position of each standard film the same means, for example, mounting the film 1 at a predetermined predetermined position of the scanner document table 10. For example, by placing the apex angle V3 of the film 1 in alignment with the right end corner RE of the scanner document table 10, the acquisition operation of optical density data from all the standard films can be performed at the completely same position. An arbitrary apex angle of the film 1 can be placed, for example, in alignment with an arbitrary point (for example, the right end corner RE, the left end corner LE, and the center marker CE) of the scanner document table 10. Furthermore, any midpoint of the film 1 can be placed on an arbitrary point (e.g., the center marker CE) of the scanner platen 10.

Thus, by performing scanning, optical density data at a specific radiation exposure dose can be obtained at each of all the pixels distributed over the entire surface of each standard film. Specifically, optical density data of red (R) component, blue (B) component, and green (G) component is obtained for each pixel, and for example, for one pixel, radiation irradiation in that pixel is performed. It is possible to obtain a standard curve (three standard curves) showing the relationship between the dose and the optical density (R, G, B), that is, a calibration curve (three calibration curves) for determining the radiation exposure dose from the optical density. In the transmission type chromic film which is an object of the present invention, since the optical density of the green (G) component is low, the data of the green (G) component can be ignored, and the red (R) component and blue (B) Accurate calibration can be performed using only two calibration curves of the component, and almost accurate calibration can be performed using only the calibration curve of red (R) component. That is, for each individual pixel, calibration curves (one to three calibration curves) unique to those pixels can be obtained independently of each other. In the calibration curve recording step, the calibration curve for each pixel thus obtained is recorded in association with each pixel.
Thus, an original calibration map can be created for a particular set of transmissive chromic films.

  FIG. 3 (a) is a schematic view showing a method of creating an original calibration map, and FIG. 3 (b) is a schematic view showing a relationship between the creation method shown in FIG. 3 (a) and a calibration curve. In the example shown in FIG. 3A, four standard films F1 to F4 are selected, the standard film F1 is a non-irradiated standard film, and the standard films F2, F3 and F4 are irradiated with 100 cGy, 200 cGy and 300 cGy, respectively. . Subsequently, when optical density data is measured by the transmission type image scanner under the same scanning arrangement condition, for example, measured values S0, S1, S2, S3 of red (R) component at each irradiation amount are obtained in the pixel A. From these data, the calibration curve S shown in FIG. 3 (b) can be obtained. Next, if the optical density data Sw of the red (R) component at the pixel A of the radiation image obtained by the irradiation of therapeutic radiation according to the radiation treatment plan is measured, the calibration curve S of FIG. The dose W (cGy) can be determined.

When using an original calibration map, when using a film group of a production lot number different from the film group to which the original calibration map is applied (hereinafter, may be referred to as a new film group), the original calibration map The calibration map can be easily updated from the map.
The method of creating the updated calibration map includes the following steps.
(1) Update film selection process,
(2) Radiographic imaging process of update film,
(3) Optical density data acquisition process,
(4) correction calibration curve creation process, and (5) update calibration curve recording process.

  In the renewal film selection step, one non-irradiated renewal film and at least one radiation renewal film are selected as renewal films from the new film group. The non-irradiated update film is used as a blank sample in the absence of radiation. One to three irradiation update films are sufficient for irradiation, for example, only one irradiation update film can be used.

  In the radiation image forming step of the update film, when the number of irradiation update films is one, the entire surface is uniformly irradiated with a specific same radiation dose to form a radiation image on the irradiation update film. When two or more irradiated update films are used, the irradiation dose differs from one film to another, and the entire film is uniformly irradiated with the same irradiation dose for each film, and each irradiated updated film Form a radiographic image. The radiation dose emitted in the radiation imaging step may be the same as or different from the radiation dose used to create the original calibration map to be updated. When, for example, 25 cGy, 50 cGy, 100 cGy, 150 cGy, 200 cGy, and 350 cGy are used in creating the original calibration map to be updated, any one of 150 cGy, 200 cGy, and 350 cGy, for example, can be used for the irradiation updated film. Irradiation can be performed with three or more species.

  In the optical density data acquisition process, scan arrangement conditions that are completely the same as the scan arrangement conditions used to create the original calibration map to be updated are used. Here, completely identical means the same as the conditions described in the optical density data acquisition step of the original calibration map creation method. That is, the non-irradiated updated film and the irradiated updated film are completely made identical to the mounting direction and the mounting position at the time of creation of the original calibration map to be updated, with respect to the scanner document table.

  By performing scanning under the above conditions, optical density data [red (R) component, blue (red (R) component, at a specific radiation exposure dose, for each of all pixels (all pixels) distributed on the entire surface of each of the update films) Optical density data of the B) component and the green (G) component can be obtained. For example, for one pixel, a modified standard curve (three standard curves) showing the relationship between the radiation dose and the optical density at that pixel, that is, the modified calibration curve (3 for determining the radiation dose from the optical density) One calibration curve) can be obtained. That is, for each individual pixel, a correction calibration curve (one to three calibration curves) specific to those pixels can be obtained.

  Since the corrected calibration curve thus obtained has a smaller number of radiation doses when compared with the calibration curve in the original calibration map to be updated, this corrected calibration curve is respectively drawn along the calibration curve at each pixel of the original calibration map. It can be updated and an updated calibration curve can be generated. The updated calibration curve thus obtained can be recorded in the update calibration curve recording step to create an updated calibration map.

  Fig.4 (a) is a schematic diagram which shows the method to produce an update calibration map from the original calibration map shown to Fig.3 (a), and FIG.4 (b) is the original calibration curve S shown to FIG.3 (b). And the corrected calibration curve T. FIG. In the example shown in FIG. 4A, two update films G1 and G2 are selected, the update film G1 is a non-irradiated update film, and the update film G2 is irradiated at 200 cGy. Subsequently, when optical density data is measured by the transmission type image scanner under the same scanning arrangement condition, for example, measurement data T0, T2 of the red (R) component of the pixel A at the same position are obtained. The original calibration curve S can be corrected to the corrected calibration curve T from the comparison with the corresponding measurement data S0, S2 of The data T1 and T3 corresponding to the measurement data S1 and S3 obtained when creating the original calibration curve S need not be measured when obtaining the corrected calibration curve T, and can be calculated by calculation. . The corrected calibration curve T thus obtained is also the optical of the red (R) component in the pixel A of the radiation image obtained by the irradiation of the therapeutic radiation according to the radiation treatment plan, similarly to the calibration curve S of FIG. 3 (b). From concentration data, it can be used in determining the actual dose.

  The update calibration map can be repeatedly updated by the same method even for another new film group, and the update calibration map can be created one after another in a simple manner.

Even if the transmission image scanner to be used is changed, an original calibration map can be created, or an already existing calibration map (original or updated calibration map) can be updated. The method of updating when the film group is not changed and the scanner is changed will be briefly described below.
The method of creating the updated calibration map in this case also includes the following steps.
(1) Update film selection process,
(2) Radiographic imaging process of update film,
(3) Optical density data acquisition process,
(4) correction calibration curve creation process, and (5) update calibration curve recording process.

  The update film selection process is the same as the update film selection process in the case of changing the film group, except that the update film is selected from the film group used to create the calibration map to be updated. Moreover, the radiation image formation process of the update film implements the completely same operation as the radiation image formation process of the update film at the time of changing a film group. Next, in the optical density data acquisition process, the scanning arrangement conditions are the same as the optical density data acquisition process when the film group is changed, except that the scanning process is performed in the newly used transmission type image scanner. is there. Furthermore, the subsequent correction calibration curve creation step and the updated calibration curve recording step are the same as the optical density data acquisition step when the film group is changed.

  As described above, the calibration map according to the present invention can be created by the above generation method or update method. That is, the calibration map according to the present invention is a transmission image of radiation images formed on individual transmission chromic films belonging to transmission chromic films (for example, films having the same production lot number) whose physical properties are considered to be identical. From the optical density obtained by the scanner, it can be used to determine the actual radiation exposure to the transmission chromic film.

  In addition, the calibration map according to the present invention is measured by the transmission image scanner from the plurality of radiation doses irradiated in each of the pixels across the entire surface of the transmission type chromic film and the images obtained by the radiation irradiation. A calibration curve derived from the optical density obtained is provided independently of one another for each pixel and associated with each of the pixels across the entire surface of the film.

  Furthermore, the calibration map according to the present invention is created by measuring the radiation image formed on the transmission type chromic film by a transmission type image scanner under predetermined specific scanning arrangement conditions, so that according to the present invention The calibration map contains instructions (or information) of the specific scan placement conditions described above. That is, when this calibration map is used, for example, in the radiation dose verification method of a radiation treatment plan, the transmission type chromic film irradiated with the treatment plan is specified according to the above-mentioned instruction (or information). It is necessary to scan in the scan arrangement condition.

The calibration map according to the invention can be stored on any known computer readable recording medium. The recording medium can be used for an analysis system or an analysis device. The present invention also provides the recording medium, and their analysis system and analysis apparatus.
The computer readable recording medium may be, for example, a compact disc, a flexible disc, a hard disc, a magneto-optical disc, a digital video disc, a magnetic tape, or a semiconductor memory.

Furthermore, the calibration map according to the present invention can be used for the dose verification method of a radiation treatment plan. Specifically, the dose verification method is
(1) The transmission chromic films belonging to the transmission chromic films, for which the calibration map according to the present invention (i.e., the original calibration map or the updated calibration map) is created, are irradiated with therapeutic radiation according to the radiation treatment plan to obtain a radiation image Forming process,
(2) measuring an optical density from the radiation image formed on the transmission type chromic film by a transmission type image scanner under a predetermined specific scanning arrangement condition specific to the calibration map; and (3) the above Calculating the radiation dose from the optical density using the calibration map for all pixels of the radiation image.

  Since the radiation imaging step of the step (1) is generally carried out in a phantom, it is preferable that the calibration map according to the present invention be prepared in advance using the same phantom. Further, in the optical density measurement step of the step (2), it is necessary to place the radiation imaging film on the scanner base and carry out scanning in accordance with the scanning arrangement condition included in the calibration map of the present invention as attached information. . By calculating the radiation dose according to the step (3), data of the radiation dose calibrated from the measured optical density can be obtained over the whole surface of the radiation imaging film, and extremely accurate verification can be performed. .

  In the method of creating a calibration map of the present invention or the dose verification method of the present invention, it is necessary to place the chromic film under a specific scanning arrangement condition in the step of measuring the optical density with a transmission image scanner. That is, the arrangement position and the arrangement direction of each film at the time of creating the original calibration map or the updated calibration map are made the same, and further, in the irradiation amount verification method, the placement conditions of the chromic film are made the same as the conditions at the time of calibration map creation. There is a need to. In commercially available chromic films, films provided with small holes in the same corner may be provided by being stacked in a packaging box. In this case, the arrangement conditions of the chromic films may be made the same as marks for the small holes. it can. When using a film without marks such as the above-mentioned small holes, before opening the packaging box and taking out the first chromic film, the same apex angle or the same apex angle of all the chromic films stacked in the packaging box It is preferable to put a mark or the like at a specific position on the side and to record the laminating direction at the time of delivery on all the films.

[Confirmation experiment of unevenness]
When the optical density of a transmission type chromic film uniformly irradiated on the entire surface with radiation is measured by a transmission type image scanner, the measurement value changes depending on the arrangement direction and the arrangement position of the film on the document table by the following method. confirmed.

  As the film, a transmissive chromic film [8 inches × 10 inches (20.3 cm × 25.4 cm): Gafchromic EBT3: manufactured by ASHLAND Co., Ltd.] was used. As a scanner, a flatbed scanner (ES-10000G: manufactured by EPSON) was used. Two transmissive chromic films A and B having the same production lot number were prepared, and the entire surface of one film A was irradiated with sunlight for 30 minutes and uniformly irradiated with parallel ultraviolet light over the entire film surface. . The next day, the entire surface of the other film B was similarly exposed to sunlight for 30 minutes, and was uniformly irradiated with parallel ultraviolet light over the entire film.

  The film A (and B) used in the confirmation experiment has four sides S1 to S4 and four apex angles V1 to V4 as shown in FIG. The central regions r1 to r9 of the sections R1 to R9 each have a total number of pixels of 7056 (about 30 mm × about 30 mm). Moreover, as a scanner, the scanner of the structure shown in FIG. 2 was used.

  The irradiated film A was placed on the document table 10 of the scanner as shown in FIG. 5 (a). At that time, the apex angle V2 of the irradiation film A was made to exactly coincide with the right end corner RE of the document table 10, and the side S2 of the irradiation film A was made to coincide exactly with the scanning start end 12 of the document table 10. In order to distinguish the position of the apex angle V2 used for alignment from the other apex angles, it is indicated by the mark ● in FIG. 5 (a), which is entered for the convenience of explanation, It is not a mark actually attached.

  The optical density was measured in the state shown in FIG. 5A (arrangement state 1). The results are shown in Table 1. Table 1 shows scanner read values (ADC value: Analog-to-Digital Converter) of the red component (Red), the blue component (Blue), and the green component (Green) in each of the central regions r1 to r9.

Next, the irradiation film A was rotated 90 ° clockwise on the document table 10 to be in the state (arrangement state 2) shown in FIG. 5 (b). Even in this arrangement state 2, the apex angle V1 of the irradiation film A is made to exactly coincide with the right end corner RE of the document table 10, and the side S1 of the irradiation film A is made to exactly coincide with the scanning start end 12 of the document table 10. The optical density was measured in the dry state. The scanner readings in each of the central regions r1 to r9 are shown in Table 1.
Furthermore, the irradiation film A was rotated 90 ° clockwise on the document table 10 to be in the state shown in FIG. 5C (arrangement state 3). Even in this arrangement state 3, the apex angle V4 of the irradiation film A is exactly matched with the right end corner RE of the document table 10, and the side S4 of the irradiation film A is exactly matched with the scanning start end 12 of the document table 10. The optical density was measured in the dry state. The scanner readings in each of the central regions r1 to r9 are shown in Table 1.
Finally, the irradiation film A was rotated by 90 ° clockwise on the document table 10 to be in the state shown in FIG. 5D (arrangement state 4). Even in this arrangement state 4, the apex angle V3 of the irradiation film A is exactly matched with the right end corner RE of the document table 10, and the side S3 of the irradiation film A is exactly matched with the scanning start end 12 of the document table 10. The optical density was measured in the dry state. The scanner readings in each of the central regions r1 to r9 are shown in Table 1.

  Subsequently, the optical density of the irradiation film B was also measured in the arrangement states 1 to 4. Table 2 shows scanner reading values in each of the central regions r1 to r9 of the irradiated film B.

  The calibration map according to the present invention can be used to verify the radiation dose irradiated to the chromic film according to the radiation treatment plan, and correct the non-flatness generated based on the arrangement condition on the image scanner document table And very accurate verification can be performed.

1 · · · film · 10 · · · Scanner original plate
12 ··· Scanning start end; 13 · · · Terminal end; 15 · · · Right edge;
16 ··· Left edge; M1, M2, M3, M4 · · · Mid point;
R1, R2, R3, R4, R5, R6, R7, R8, R9 ... divisions;
r1, r2, r3, r4, r5, r6, r7, r8, r9 ... central region;
S1, S3 ... long side; S2, S4 ... short side;
V1, V2, V3, V4 ... apex angle;
X: Scanning direction; Y: Scanner light source direction;
RE ... right end corner; LE ... left end corner; CE ... center marker.

Claims (8)

Regarding the radiation image formed on each of the transmission type chromic films belonging to the transmission type chromic film group considered to have the same physical properties, the actual radiation exposure dose to the transmission type chromic film from the optical density obtained by the transmission type image scanner A method of creating an original calibration map used to determine
(1) a step of selecting one non-irradiated standard film and at least two irradiated standard films as standard films from the transmission-type chromic film group considered to have the same physical properties as described above;
(2) For each of the above-mentioned irradiation standard films, the irradiation dose differs from one film to another, and in the case of each film, the entire surface is uniformly irradiated with the same radiation irradiation amount, Forming a radiation image on the
(3) obtaining optical density data for each pixel across the entire surface of the standard film from each of the standard films under the same scanning arrangement condition in the transmission type image scanner, and (4) the above From the optical density data obtained in step (3) and the radiation exposure data of each standard film, a calibration curve of optical density and radiation exposure is created in association with each pixel and recorded. , How to create the original calibration map described above. Regarding different transmission type chromic film groups whose physical properties are considered to be identical but whose physical properties may be different from the physical properties of the transmission type chromic films used to create the original calibration map according to claim 1 A method of correcting an original calibration map created by the method described in item 1 to create an updated calibration map,
(1) A step of selecting one non-irradiated update film and at least one irradiated update film as update films from the different transmission type chromic films described above,
(2) The irradiation update films described above have different radiation doses among the respective films, and in the individual films, the entire surface is uniformly irradiated with the same radiation irradiation dose, and the irradiation update films are on each other. Forming a radiation image,
(3) obtaining optical density data for each pixel across the entire surface of the irradiation film from each of the update films under the same scanning arrangement condition as the scanning arrangement condition according to claim 1;
(4) From the optical density data obtained in the step (3) and the radiation exposure dose data of each irradiation film, a step of creating a corrected calibration curve of the optical density and the radiation exposure dose in association with each pixel. ,
(5) The method of creating an updated calibration map, including the steps of updating the modified calibration curve created in the step (4) along the calibration curve of the original calibration map and recording the updated calibration curve.   A method of creating an updated calibration map, further modifying the updated calibration map generated by the method of claim 2 by the method of claim 2. A method of updating the calibration map of a transmission image scanner different from the transmission image scanner used to create the calibration map according to any one of claims 1 to 3,
(1) selecting one non-irradiated update film and at least one irradiated update film as update films from the transmission-type chromic films used to create the calibration map;
(2) The irradiation update films described above have different radiation doses among the respective films, and in the individual films, the entire surface is uniformly irradiated with the same radiation irradiation dose, and the irradiation update films are on each other. Forming a radiation image,
(3) In the different transmission type image scanner described above, each of the respective update films under the same scan arrangement condition as the scan arrangement condition according to claim 1 to each pixel extending over the entire surface of the update film Obtaining optical density data,
(4) From the optical density data obtained in the step (3) and the radiation exposure data of each updated film, a step of creating a corrected calibration curve of the optical density and the radiation exposure in association with each pixel. And (5) updating the modified calibration curve created in the step (4) along the calibration curve of the calibration map to be updated, and recording the updated calibration curve. Regarding the radiation image formed on each of the transmission type chromic films belonging to the transmission type chromic film group considered to have the same physical properties, the actual radiation exposure dose to the transmission type chromic film from the optical density obtained by the transmission type image scanner A calibration map used to determine
In each of the pixels across the entire surface of the transmissive chromic film, a plurality of irradiated radiation doses and an optical density measured by a transmissive image scanner from an image obtained by the irradiation of the radiation Having a calibration curve associated with each of the pixels across the entire surface of the film, and the radiographic image formed on the transmissive chromic film being measured by the transmissive image scanner at a predetermined specific scanning arrangement condition Calibration map, characterized in that it comprises instructions for   A calibration map obtained by the method according to any one of the preceding claims.   A computer readable recording medium comprising the calibration map according to claim 5 or 6. (1) forming a radiation image by irradiating a therapeutic radiation according to a radiation treatment plan on a transmission-type chromic film belonging to a transmission-type chromic film group in which the calibration map according to claim 5 or 6 is created;
(2) measuring an optical density from the radiation image formed on the transmission type chromic film by a transmission type image scanner under a predetermined specific scanning arrangement condition specific to the calibration map; and (3) the above A radiation dose verification method for a radiation treatment plan, comprising the step of calculating a radiation dose from the optical density using the calibration map for all pixels of a radiation image.