RU2684567C2 - Method for reconstructive dosimetric control of proton therapy by scanning beam - Google Patents

Method for reconstructive dosimetric control of proton therapy by scanning beam Download PDF

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RU2684567C2
RU2684567C2 RU2018128413A RU2018128413A RU2684567C2 RU 2684567 C2 RU2684567 C2 RU 2684567C2 RU 2018128413 A RU2018128413 A RU 2018128413A RU 2018128413 A RU2018128413 A RU 2018128413A RU 2684567 C2 RU2684567 C2 RU 2684567C2
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dose
surface
scanning beam
image
patient
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Александр Евгеньевич Чернуха
Ольга Геннадьевна Лепилина
Степан Евгеньевич Ульяненко
Алексей Николаевич Соловьев
Сергей Николаевич Корякин
Ольга Юрьевна Голованова
Марина Вячеславовна Трошина
Андрей Дмитриевич Каприн
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Федеральное государственное бюджетное учреждение "Национальный медицинский исследовательский центр радиологии" Министерства здравоохранения Российской Федерации (ФГБУ "НМИЦ радиологии" Минздрава России)
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00Radiation therapy
    • A61N5/10X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01TMEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation

Abstract

FIELD: medicine.SUBSTANCE: invention refers to medicine, namely to radiology and medical biophysics, and can be used for reconstructive dosimetric monitoring in a proton therapy by a scanning beam. Radiochromic film is placed on the patient's body surface. Proton focus therapy is performed. In the interactive viewing mode of the accepted treatment plan with the prescribed dose (D), scanning by layers a patient's tomogram with one constant dose line, which value is changed during viewing, determining maximum dose on surface (D) at the scanning beam input point. Further, in therapy, maximum dose on surface is measured (D) in the same place with a radiochromic film fixed on the patient's body. That is followed by reconstructing the dose in the lesion by the formula: D=D/(D/D), where Dis design maximum surface dose, Dis the measured maximum surface dose, Dis a prescribed dose. Cross-section of the secant planes on the edge of the image of the surface is established, at least in the coronary and sagittal sections at the point of entry of the scanning beam. Indicator values are varied so that some part of the isodose line, at least in the coronary and sagittal sections, passes along the edge of the image of the surface at the point of entry of the scanning beam. Irradiated film is scanned using a scanning device and an image of optical density is obtained. Image of optical density is processed with a software package for obtaining an image which contains a pixel value with a maximum dose on the surface at the point of entry of the scanning beam, the value of which is found in the title by an indicator.EFFECT: method provides fast, immediately after irradiation, reconstructive control of the dose supplied to the lesion and evaluation of possible reactions from the skin by calculating the dose supplied using the values of the prescribed dose, as well as calculated and measured maximum doses on surface.5 cl, 2 dwg, 1 ex

Description

The invention relates to nuclear medicine, namely to: technologies for planning proton therapy, technologies for medical x-ray tomography, technologies for measuring radiation fields with radiochrome films, and related fields of technology.

State of the art

Providing quick dosimetric control of the administered dose and reactions from the skin of the patient during radiation therapy of cancer tumors includes the use of planning systems - a package of applied programs that provide calculation of the absorbed dose when various types of radiation are exposed to living tissue; dosimetric systems and equipment measuring the dose absorbed by tissue; appropriate computing tools to visualize the distribution and absorption of radiation energy.

Dosimetric monitoring of the therapy process can be carried out in real time, during the treatment sessions, which is associated with the use of high-tech equipment and the development of the corresponding mathematical apparatus.

Currently, there is a known method of dosimetric monitoring, in particular, proton range verification (Hsin-Hon Lin, at al. A comparison of two prompt gamma imaging techniques with collimator-based cameras for range verification in proton therapy. Http: // dx. doi.org/10.1016/j.radphyschem.2016.04.0.020; Yunhe Xie, at al. Prompt gamma imaging for in vivo range verification of pencil beam scanning proton therapy.http: //dx.doi.org/10.1016/j.ijrobp .2017.04.027), based on measuring the dose of gamma radiation (photons) of proton nuclear reaction products during the implementation of the plan of radiotherapy (irradiation) with a scanning beam. The specified method is carried out by measuring the distal part of the photon dose profile by a collimated gamma camera, including a linear chain of scintillation detectors and located near the lesion, perpendicular to the beam axis; visualization of the dose profile of photons on the same line with the patient's tomogram; approximation of the dose profile of photons in three linear sections — the proximal portion of the dose increase, the dose attenuation section starting at the maximum and the distal section of the profile characterized by a lower angular coefficient of the straight portion; estimates of the proton mean free path as the depth of half attenuation of the measured dose of photons in the second linear section of the profile.

One of the disadvantages of the method can be attributed to the inaccessibility for wide medical practice of complex and expensive real-time dosimetric monitoring technologies.

The dose administered to the tumor can be controlled indirectly, by constructing model tasks that are close in the sense of medical physics to the real process of radiation therapy, using phantoms that mimic the human body in the sense of radiation physics. These include the dosimetric control method used in radiotherapy with a passive proton beam (Ryosuke Kohno, at al. In Vivo Dosimetry of an Anthropomorphic Phantom Using the RADPOS for Proton Beam Therapy. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 2016, 5, 177-183. Japan.). The method includes real-time dose measurement using MOSFET dosimeters and their RADPOS positioning system, as well as an anthropometric Salem head phantom (The Phantom Laboratory, Salem, CA, USA). To conduct dosimetry in this way, MOSFET dosimeters are placed in special holes located axially in the upper part of the Salem phantom. The RADPOS system determines the position of dosimeters in the holes with an accuracy of 1 mm. The exposure conditions of the PTV (planning target volume) of the real patient, transferred to the phantom and the correction factor for the LET dependence of the MOSFET dosimeters, are calculated using the Monte Carlo planning software package. The results of measurements on a proton beam with an energy of 190 MeV and a width of the distributed Bragg peak of 60 mm were compared with the corresponding calculations of the volumetric dose distribution. They turned out to be comparable in terms of gamma index within the tolerance range of 3 mm and 3%.

In this case, the disadvantage of this method lies in its invasiveness, which limits the clinical application.

Relatively quick control of the administered dose can be carried out by measuring the surface dose with or without reconstruction of the dose absorbed in the tumor, especially in cases close to the surface of the tumor. For example, there is a known method of postradiation monitoring used in photon beam radiotherapy (V. Rudat et al. In vivo surface dose measurement using GafChromic film dosimetry in breast cancer radiotherapy: comparison of 7-field IMRT, tangential IMRT and tangential 3D-CRT. Radiation Oncology 2014, 9: 156. Saad Specialist Hospita.), Including the measurement of surface dose by a GAFCHROMIC® type radiochromic film. In accordance with this method, 3x3 cm film fragments are placed on the body surface at the location of the tumor. Planning for radiotherapy with a photon beam is performed by the XIO 4.4 planning software package (CMS, Inc. of St. Louis, Mo, USA). On the CT image of the pathology zone and the zone of interest, “skin integuments” are depicted with an indentation of 3 mm into the depth of the PTV (Planning Target Volume) from the body surface. The average dose calculated in the course of planning in the area of interest is considered the surface dose. Post-radiation control in this way was performed in 50 patients for several treatment sessions. The differences between the calculated surface dose and the dose measured by the film in the case of counter-treatment and several central bundles relative to the tumor did not exceed 4.2% and 18.8% in the first and second cases, respectively.

The disadvantage of this method is a rather rough interpretation of the surface dose at the planning stage.

In the sense of rapid post-radiation dosimetric monitoring of the process of proton therapy, a method can be noted that includes measuring the surface dose and reconstructing the uncertainty in the range of protons (this is the prototype of the proposed method) when radiotherapy is performed with a passive proton beam of lung tumors with localization at the far surface of the body (Zheng Y. SU- ET-449: In-Vivo Dosimetry and Range Verification for Proton Therapy. Med Phys. 2013 Jun; 40 (6 Part 17): 308. doi: 10.1118 / 1.4814882. Oklahoma City). In accordance with this method, a radiochromic film is placed on the far surface of the body and the average value of the surface dose is measured during therapy. The XIO 2.0 radiation therapy planning software package (CMS, Inc. of St. Louis, Mo, USA), at the stage of radiotherapy preparation, calculates the depth distribution of the dose (dose curve) from the entrance of the beam to its exit to the surface (calculated surface dose). The magnitude of the uncertainty in the range of protons is estimated by the difference in positions on the dose curve, the values of the calculated and measured surface doses. Testing the method on phantoms, on laboratory animals and subsequent clinical application showed that the measured and calculated values of the surface dose differ by no more than 2%, and the uncertainties in the range of protons are about 2 mm.

However, in some cases, the proton beam exiting the tumor may be unacceptable and dosimetric monitoring using this method will be impossible.

Disclosure of the invention.

The technical result consists in providing quick reconstructive control of the administered dose into the lesion and assessing possible reactions from the skin during proton therapy with a scanning beam.

The specified technical result is achieved due to the fact that as well as in the known method, the average value of the surface dose is measured.

A feature of the proposed method is that in the interactive viewing mode of the accepted treatment plan with the prescribed dose

Figure 00000001
and viewing the tomogram of the patient with layers with one line of a constant dose, the value of which is changed during the viewing, determine the maximum dose on the surface
Figure 00000002
at the entrance to the scanning beam, then during the treatment, measure the maximum dose on the surface
Figure 00000003
in the same place with a radiochromic film fixed on the patient’s body, after which a dose is reconstructed at the lesion site using the formula:

Figure 00000004

Where:

Figure 00000005
- estimated maximum dose on the surface,

Figure 00000006
- measured maximum dose on the surface,

Figure 00000007
- prescribed dose.

Set the cross-section of the secant planes at the edge of the surface image, at least in the coronary and sagittal sections at the entrance to the scanning beam. The pointer values are changed so that some part of the isodose line, at least in the coronary and sagittal sections, passes along the edge of the image of the surface at the entrance to the scanning beam. The irradiated film is scanned using a scanner device and an optical density image is obtained. The optical density image is processed by the image processing software package to obtain an image that contains the pixel value with the maximum dose on the surface at the entrance to the scanning beam, the value of which is found in the title by the pointer.

One of the advantages is that the maximum dose on a small surface area is calculated and measured on the surface of the patient’s body under conditions of significant gradients of the radiation field at the entrance of the scanning beam, which reduces the uncertainties of the geometric reconstruction.

The invention is illustrated by a detailed description, clinical example and illustrations, which depict:

FIG. 1 - Window for interactive viewing of the adopted treatment plan with three sections of the patient's tomogram: 1 - coronary section of the tomogram; 2 - sagittal section; 3 - frontal section; 4 - line of constant dose (isodose); 5 - cross-section of cross planes; 6 - isodose level indicators (relative, absolute from left to right); 7 - the entrance point of the scanning beam with a fragment of the radiochrome film placed on the surface; 8 - focus lesion dose.

FIG. 2 - Image of the radiation field on the surface measured by a radiochromic film: 9 - image of the isodoses of the radiation field on the surface at the entrance to the scanning beam; 10 is a pointer to the maximum dose measured on the surface at the entrance of the scanning beam.

The method is as follows.

At the time of the invention, it is believed that the specialist has a calculated dose distribution in the lesion and a patient tomogram - a treatment plan with a prescribed dose

Figure 00000001
, an application package for interactive viewing of the treatment plan, a radiochrome film (for example, GAFCHROMIC®), a device for acquiring a digital image of the optical density of the film (scanner), and an application package for obtaining a digital image of the dose distribution on the film.

The determination of the estimated maximum dose on the surface at the entry point of the scanning beam is indicated in FIG. 1. The window for interactive viewing of the treatment plan contains at least images of tomogram sections (layers): coronary section 1, sagittal section 2 and frontal section 3 with the image of a constant dose line 4 (isodoses) on them. Images of sections 1, 2, 3 correspond to the position of the crosshairs of 5 secant planes. The values of the isodose level 6 indicators are set as a percentage of the prescribed dose and are automatically converted in absolute units of the dose (from left to right, respectively), while the prescribed dose is determined as 100%. The entry point of the scanning beam 7 or the location of the radiochromic film is shown illustratively. The lesion focus 8 is circled by a contour that is applied by clinicians to the patient's tomogram.

To determine the maximum dose on the surface at the entrance to the scanning beam, proceed as follows. The intersection of 5 secant planes is set on the edge of the surface image in at least two of sections 1, 2, 3 at the entrance of the scanning beam 7. Additionally, by changing the values of the pointer 6, the maximum dose on the surface is found. Shown in FIG. 1, the isodose line 4 corresponds to the maximum dose on the surface. The pixel size of sections 1, 2, 3 provides clinical resolution in determining the position of the isodose. The position of the crosshair of 5 secant planes is controlled by scrolling and clicking the mouse.

Next, an additional procedure is carried out to find the measured maximum dose on the surface at the entrance to the scanning beam (Fig. 1, 2). The image (Fig. 1) illustratively shows the location of a fragment of a radiochromic film mounted on the patient’s body at the entrance (7) of the scanning beam. In FIG. Figure 2 shows the image of the isodoses (9) of the radiation field on the surface at the inlet of the scanning beam, measured by a millimeter scale radiochromic film. To obtain an image, the isodose (9) is initially scanned using the scanner device and an image (not shown) is obtained, each pixel of which contains a numerical value of the optical density of the radiosensitive layer of the film, then, proceeding from this image, during further processing by the mathematical processing software package images receive an image (9), each pixel of which contains a numerical value of the absorbed dose. This image (Fig. 2) also contains the title with the maximum dose indicator (10) and isodose levels (30, 50, 60, 70, 75, 80), indicated as a percentage of the maximum dose, which are automatically generated by the mathematical image processing software package . The resolution of the image (9) is set during scanning and is usually 150 Dpi (pixels per inch).

The value of the level (6) of isodose (4) (Figs. 1 and 2), corresponding to the maximum dose on the surface at the entrance to the scanning beam, is used to reconstruct the applied dose D into the lesion (8), which is carried out according to the formula:

Figure 00000008

in which the symbol

Figure 00000009
the calculated maximum dose on the surface is indicated in accordance with the level indicator (6), the symbol
Figure 00000010
the measured maximum dose on the surface is indicated in accordance with the level indicator (10) and the symbol
Figure 00000011
The prescribed dose is indicated.

The value of the measured maximum dose on the surface, in accordance with the level indicator (10), can be used by clinic specialists to monitor possible reactions from the skin during proton therapy with a scanning beam.

Clinical example.

Patient B. was in the hospital department of proton and photon therapy MRRC them. A.F. Tsyba is a branch of the Federal State Budgetary Institution Scientific Research Center for Radiology of the Ministry of Health of Russia with a diagnosis of esthesiuroblastoma of the nasal cavity. PCT. Lesion focus: nasal cavity and ethmoid labyrinth. Focal dose: 63 Gy (Gray), single dose: 1.8 Gy, number of fractions 35, with two fields in each fraction - 80, 100 degrees, weight (number of particles) 49.62% and 50.38% respectively. A fragment of the radiochromic film was fixed on the patient's thermoplastic mask in the nose.

After carrying out the radiation fraction, the interactive viewing window of the patient treatment plan is used as described with reference to FIG. 1, to determine the estimated maximum dose on the surface as the value of the level indicator (6). The image of the radiation field (Fig. 2) on the surface was used to determine the maximum dose on the surface, which is taken equal to the value of the level indicator (10). Reconstruction of the administered dose is obtained as the ratio:

Figure 00000012

Additionally, we evaluated the possible reactions from the skin at the maximum dose on the surface. In this case, with a maximum dose on the surface of 1.37 Gy, the degree of tolerance on the part of the skin was assessed as Grade 2 (Grade 1, 2, 3 by increasing tolerance).

The use of this invention will allow for quick (immediately after irradiation) reconstructive control of the administered dose to the lesion and assessment of possible reactions from the skin at the maximum dose.

Claims (10)

1. The method of reconstructive dosimetric control in proton therapy with a scanning beam, comprising placing a radiochromic film on the surface of the patient’s body and, during therapy, measuring the average value of the surface dose, characterized in that in the interactive mode of viewing the accepted treatment plan with the prescribed dose (
Figure 00000013
), viewing the tomogram of the patient with layers with one line of a constant dose, the value of which is changed during the viewing, determine the maximum dose on the surface (
Figure 00000014
) at the point of entry of the scanning beam, then during the treatment, measure the maximum dose on the surface (
Figure 00000015
) in the same place with a radiochromic film fixed on the patient’s body, after which a dose is reconstructed at the lesion site using the formula:
Figure 00000016
Where
Figure 00000017
- estimated maximum dose on the surface,
Figure 00000015
- measured maximum dose on the surface,
Figure 00000013
- prescribed dose.
2. The method according to p. 1, characterized in that the crosshair of the secant planes is mounted on the edge of the surface image, at least in the coronary and sagittal sections at the entrance to the scanning beam.
3. The method according to p. 1, characterized in that the pointer values are changed so that some part of the isodose line, at least in the coronary and sagittal sections, passes along the edge of the surface image at the entrance to the scanning beam.
4. The method according to p. 1, characterized in that the irradiated film is scanned using a scanner device and an optical density image is obtained.
5. The method according to p. 1, characterized in that the optical density image is processed by a processing software package to obtain an image that contains a pixel value with a maximum dose on the surface at the entrance to the scanning beam, the value of which is found in the title by pointer.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2360716C2 (en) * 2003-08-12 2009-07-10 Лома Линда Юниверсити Медикал Сентер Patient-aid modular system
RU2605998C2 (en) * 2010-06-11 2017-01-10 Конинклейке Филипс Электроникс Н.В. Simultaneous multi-modality inverse optimization for radiotherapy treatment planning

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2360716C2 (en) * 2003-08-12 2009-07-10 Лома Линда Юниверсити Медикал Сентер Patient-aid modular system
RU2605998C2 (en) * 2010-06-11 2017-01-10 Конинклейке Филипс Электроникс Н.В. Simultaneous multi-modality inverse optimization for radiotherapy treatment planning

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
Kohno R. et al. In vivo dosimetry of an anthropomorphic phantom using the RADPOS for proton beam therapy // IJMPCERO. 2016; 5 (3): 177-83. *
Rudat V. et al. In vivo surface dose measurement using GafChromic film dosimetry in breast cancer radiotherapy: comparison of 7-field IMRT, tangential IMRT and tangential 3D-CRT // Radiat Oncol. 2014; 9: 156. *
Xie Y. et al. Prompt gamma imaging for in vivo range verification of pencil beam scanning proton therapy // Int J Radiat Oncol Biol Phys. 2017; 99 (1): 210-8. *
Xie Y. et al. Prompt gamma imaging for in vivo range verification of pencil beam scanning proton therapy // Int J Radiat Oncol Biol Phys. 2017; 99 (1): 210-8. Kohno R. et al. In vivo dosimetry of an anthropomorphic phantom using the RADPOS for proton beam therapy // IJMPCERO. 2016; 5 (3): 177-83. Rudat V. et al. In vivo surface dose measurement using GafChromic film dosimetry in breast cancer radiotherapy: comparison of 7-field IMRT, tangential IMRT and tangential 3D-CRT // Radiat Oncol. 2014; 9: 156. *
Zheng Y. SU-E-T-449: In-Vivo Dosimetry and Range Verification for Proton Therapy // Med Phys. 2013; 40 (6 Part 17): 308. *

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