High-energy accelerators are often used in oncological practice, but the information on the small-field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( kQclin,Qreffclin,fref$k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ ) for solid-state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte-Carlo method using EGSnrc toolkit for six field sizes (from 0.5×0.5cm2$0.5 \times 0.5\ {\rm{cm}}^2$ to 10×10cm2$10 \times 10\ {\rm{cm}}^2$ ) for isocentric and constant source-to-surface distance (SSD) techniques. The decrease in the field size led to an increase in kQclin,Qreffclin,fref$k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ for ionization chambers, while for solid-state detectors and radiochromic film, kQclin,Qreffclin,fref$k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm3 PTW 31010) versus up to 1.183 (16 mm3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte-Carlo simulation did not exceed 3% in the fields from 1.0×1.0cm2$1.0 \times 1.0\ {\rm{cm}}^2$ to 4.0×4.0cm2$4.0 \times 4.0\ {\rm{cm}}^2$ for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small-field dosimetry of high-energy photons.

The paper analyzes the features of the spatial and energy distributions of photons in depth, in radius and in energy for small fields created in water by narrow beams of high-energy bremsstrahlung radiation from medical accelerators and mono-directional, monoenergetic beams of photons. In particular, the relationship between the spatial dependences of the absorbed dose, total kerma, and ionization kerma is discussed. Using numerical simulation, the features of photon spectra in small fields at a depth of 10 cm in a water phantom for bremsstrahlung beams with maximum energies of 10, 15, 18 and 20 MeV were determined as applied to the design of Varian accelerator heads. It is shown that, in contrast to wide fields, the energy distribution of photons in these fields practically does not change within the central region of the field and strongly softens when leaving this region. With a decrease in the size of small fields from 4.04.0 to 0.50.5 cm, a certain hardening of the spectra is observed in the central region (the average energy increases by 2–4 %) and is much more significant outside this region. The work also determined the values of the clinical dimensions of small fields generated by high-energy beams of Varian accelerators of different energies in a water phantom at a depth of 10 cm, depending on the settings of the collimation system. This work was carried out with the financial support of the Russian Foundation for Basic Research and SITMA within the framework of scientific project No. 18-52-34008.

Purpose: Critical analysis of existing and obtaining more accurate data on the spatial dose distributions created in the water phantom by pencil beams (PB) of monoenergetic and bremsstrahlung photons with energies from 0.25 to 20.0 MeV, and approximation of these distributions for the purpose of calculating doses in radiation therapy. Material and Methods: Using the Monte Carlo method, the EGSnrc program and the MATLAB mathematical package, these distributions were calculated for monoenergetic photons in the energy range from 0.25 to 19.75 MeV in increments of 0.5 MeV, for bremsstrahlung photons with a maximum energy of 4.0, 6.0, 10.0, 15.0, 18.0 MeV and for the gamma-radiation spectrum of the therapeutic apparatus ROCUS. The calculation results are converted into the so-called dose kernel of photon pencil beam. The obtained dose kernel values are compared with previously published data and the observed discrepancies are discussed. Depths in water were studied from 1.0 to 40 cm in increments of 0,5 cm and along the radius from 0.02 to 46.0 cm with an uneven grid. For bremsstrahlung and photons with the spectrum of the Rocus apparatus, the possibility of approximating dose kernel values using approximation formulas convenient for calculating doses in radiation therapy has been investigated. Results: On the basis of the results obtained, a new version of the library of dose kernels of a pencil photon beam for water was created, which differs from previous versions by the use for calculating a better description and modeling of the physical processes of the interaction of photons and charged particles with matter, more adequate data on the interaction cross sections and significantly lower values of statistical uncertainties of the results. For bremsstrahlung and photons with the spectrum of the Rocus apparatus, a mathematical model of dose kernels of a pencil beam is proposed, which includes decomposition of the dose kernels into components of the primary and scattered doses, approximation formulas and empirical coefficients convenient for integration. The values of empirical coefficients are determined by fitting to the results of the calculation of dose kernels using a combination of the random search method and the nonlinear regression method. Conclusion: The results obtained in this work will improve the algorithms and increase the accuracy of dose calculation when planning remote therapy with photon beams.

This paper analyzes the current state of clinical application of proton radiation therapy (PRT) for the treatment of cancer. In particular, the indications for the use of PRT for the treatment of specific pathologies, the results and condition of randomized clinical studies of PRT compared to photon radiation therapy (PhRT) are considered, the cost of PRT is compared with the cost of PhRT. The focus is on discussing the results of PRT using in advanced countriesand Russia for the treatment of several common tumor sites. In the conclusion of the work, the ways of further improvement of radiobiology, dose delivering technology and dosimetric support of PRT are considered.

Purpose: Research of the relationships between spatial distributions in water of the main dosimetric values, namely the absorbed dose, kerma and ionization kerma, for small-size fields with a circular cross section created by divergent beams of bremsstrahlung spectrum with a maximum energy of 6 MeV. Material and methods: Using the Monte-Carlo method with the codes EGSnrc and MCNP4C2, calculations were carried out for these distributions in a water phantom for beam radii on the phantom surface from 0.1 to 3.0 cm and for depths up to 40 cm. The ratio at depths up to 5 cm, where there is a so-called build-up area, is studied in particular detail. Results: The results of calculations show that the ratio of ionization kerma to kerma for such beams at depths up to 40 cm is practically constant and equal to 0.9930 ± 0.0005. The ratio of the absorbed dose to the ionization kerma, in contrast to conventional square beams with a cross-sectional area  20 cm2, is much less than unity at radii of 1 cm at all the depths considered. Conclusion: The data obtained show that the relationship between absorbed dose, kerma and ionization kerma for photon fields produced by beams of small cross sections is very different from that for traditional beams. This circumstance should be taken into account when conducting dosimetry of small fields.

A new version of dose kernels library of photon pencil beams for water has been created to calculate a more perfect description and modelling of the physical processes of photons and charged particles' interaction with matter, with more adequate data on the interaction cross sections and significantly lower values of the statistical uncertainties of the results. The library includes data for monoenergetic photons in the energy range of 0.25-19.75 MeV, data for bremsstrahlung photons with a maximum energy of 4.0 MeV, 6.0 MeV, 10.0 MeV, 15.0 MeV, 18.0 MeV, and data for the spectrum of the ROKUS therapeutic apparatus. Dose kernels were calculated using the Monte-Carlo method by the EGSnrc code. Depths in water from 1.0 to 40 cm and along the radius from 0.02 to 46.0 cm were studied. A convenient mathematical approximation model of dose kernel of a pencil beam is proposed.

The most important stage of radiation therapy of oncological diseases is the planning of radiation treatment. In this work, this complex process in relation to proton therapy is proposed to be divided into medical and physical planning. In conventional therapy with photons and electrons, the latter is usually called dosimetric planning, however, when applied to proton radiation therapy, this stage involves a significantly wider range of tasks related to the modification and scanning of the proton beam, spreading and compensation of ranges, taking into account when planning for uncertainties and finiteness of proton ranges, a decrease in the contribution to the dose of secondary neutrons, the creation of error-tolerant optimization algorithms for dosimetric plans, and, finally, a precision calculation of dose distributions. The paper discusses the main stages and problems of physical planning of proton radiation therapy. Particular attention is paid to the formation of an extended high-dose region (extended Bragg peak) using the beam scattering method and scanning method, and to the algorithms for calculating the dose distributions created by protons in the scattering and beam scanning systems. The most detailed consideration is given to different versions of the proton pencil beam method, which allows to increase the dose calculation accuracy and take into account the transverse scattering and fluctuations in proton energy losses, especially at the end of the path (halo effect), analytical and numerical methods. Scanning are divided into three main technologies: homogeneous scanning, single field uniform dose (SFUD), multi-field uniform dose (MFUD), often called intensity modulated proton therapy (IMPT). Actual accounting problems are considered when planning the irradiation of the movement of organs, and uncertainties in determining path lengths and optimization of irradiation plans. In particular features, problems and modern approaches to the optimization of dosimetry plans of proton radiation therapy are discussed. It is noted that one of the most promising practical solutions for the uncertainty management in determining the path lengths of protons in optimization is to include possible errors in the objective function of the optimization algorithm. This technique ensures that an optimized irradiation plan will more reliably protect normal tissues and critical organs adjacent to the irradiation target from overexposure.

Abstract Development of the spectrum reconstruction method for bremsstrahlung beams with different field sizes, created medical electron linear accelerators (LAE), on the base of the deep dose distributions in a water phantom and determination of photon spectra for Varian Trilogy accelerator 6 MV. The proposed methodology is based on the use of dose kernels algorithm of point monoenergetic monodirectional source (pencil beam (PB)) for the depth dose distribution calculation, created different cross-section beams of in a water phantom, and experimental measurements of these distributions. For solving the inverse problem is applied Toolbox routines ’Optimtool’ knowing mathematical package MATLAB to solve. Bremsstrahlung energy spectrum generated medical accelerator Varian Triology with different sizes of square fields from 3 x 3 up to 40 x 40 cm2 and average energy photons, depending on the size of the fields were received. Dose kernels for a set of defined energies PB were calculated. Depth dose distribution in a water phantom, calculated using the obtained spectra and dose kernels agree well with measurement dose distributions. The proposed technique reconstruction of bremsstrahlung spectrum of medical accelerator is good adequate. Average energy spectra of photons for Varian Trilogy Accelerator in regime 6 MV varies from 1.71 to 1.43 MeV depending on the field size.

An analytical model of the dose kernel of a narrow photon beam (pencil beam) with a bremsstrahlung spectrum with maximal energy at 6 MeV was created, allowing determination of the primary and scattered components of the absorbed dose to be determined in a water phantom with error levels acceptable in practice. A simple method for the dosimetry of photon beams with small round cross sections with 6-MV bremsstrahlung spectra using this model is proposed, combining absolute measurement of the dose absorbed in the water at a reference point in the machine-specific reference geometry and calculation of the deep dose distribution using simple analytical equations for round beams with cross sections of any radius.

This article is the review of literature concerning use of proton beam therapy in treatment of oncology. The staticized data on comparison of effi ciency of this method at an eye melanoma are lit. Advantages of proton therapy on the level of local control and depression of frequency of development of the radio induced cataract are refl ected in the provided data. In evident material the technology of preparation and carrying out radiation of an eye is shortly covered with a fascicle of protons. The experience of use of proton therapy of tumors of a skull base got for the last several decades, showed good results. Physical properties of a fascicle of protons allow to achieve the maximum dose conformality, having lowered, thereby, a radial load on the next crucial anatomical structures. The presented material on an oncopediatrics shows insuffi cient knowledge of scientists concerning advantage of a fascicle of protons over modern methods of photon radiation. There are only preliminary clinical results concerning generally of treatment of cranyopharyngiomas. At cancer therapy of a mammary gland, proton therapy showed the best local control of postoperative recurrent tumors, and also depression of a dose load on the contralateral party. The available results of the retrospective analysis of clinical data in the University medical center of Lome Linda, testify to advantages of proton therapy of the localized prostate cancer. The lack of a biochemical recurrence and a local tumoral progression within 5 years after radiation was shown. The data obtained from experience of use of proton radiation therapy with passively scattered fascicle for cancer therapy of a prostate at an early stage showed the admixed results in comparison with modern methods of radiation therapy with the modulated intensity. In treatment of non-small cell cancer of mild advantage of proton therapy aren’t absolutely proved yet. There are data on extreme toxicity of a combination of a chemotherapy and photon radiation. It is supposed that physical properties of protons will allow to reduce toxicity of such technique, however clinical trials in comparison of protons and RTMI aren’t fi nished yet. The main directions of development of a method of proton therapy are shortly lit.

Purpose: Development of the bremsstrahlung spectrum reconstruction method of medical electron linear accelerators (ELA) with different field sizes on the base of the deep dose distributions in a water phantom and determination of photon spectra for Varian Trilogy accelerator 6 MV. Material and methods: The proposed methodology is based on the use of dose kernels algorithm of point monoenergetic monodirectional source (pencil beam (PB)) for the deep dose distribution calculation, created different cross-section beams of in a water phantom, and experimental measurements of these distributions. For solving the inverse problem is applied Toolbox routines 'ptimtool knowing mathematical package MATLAB to solve. Results: Bremsstrahlung energy spectrum generated medical accelerator Varian Triology with different sizes of square fields from 3×3 up to 40×40 cm and average energy photons, depending on the size of the fields were received. Dose kernels for a set of defined energies PB were calculated. Depth dose distribution in a water phantom, calculated using the obtained spectra and dose kernels agree well with measurement dose distributions. Conclusion: The proposed technique reconstruction of bremsstrahlung spectrum of electron linear accelerator is adequate. Average energy spectra of bremsstrahlung photons for Varian Trilogy Accelerator in regime 6 MV varies from 1.71 to 1.43 MeV depending on the field size.

One of the most difficult problems of modern radionuclide therapy (RNT) is control of the absorbed dose in pathological volume. This research presents new approach based on estimation of radiopharmaceutical (RP) accumulated activity value in tumor volume, based on planar scintigraphic images of the patient and calculated radiation transport using Monte Carlo method, including absorption and scattering in biological tissues of the patient, and elements of gamma camera itself. In our research, to obtain the data, we performed modeling scintigraphy of the vial with administered to the patient activity of RP in gamma camera, the vial was placed at the certain distance from the collimator, and the similar study was performed in identical geometry, with the same values of activity of radiopharmaceuticals in the pathological target in the body of the patient. For correct calculation results, adapted Fisher-Snyder human phantom was simulated in MCNP program. In the context of our technique, calculations were performed for different sizes of pathological targets and various tumors deeps inside patient’s body, using radiopharmaceuticals based on a mixed β-γ-radiating (131I, 177Lu), and clear β- emitting (89Sr, 90Y) therapeutic radionuclides. Presented method can be used for adequate implementing in clinical practice estimation of absorbed doses in the regions of interest on the basis of planar scintigraphy of the patient with sufficient accuracy.

Purpose or Objective: To investigate the association between external beam radiotherapy (EBRT) and pleural and peritoneal mesothelioma among long-term (>5 years) solid cancer survivors. Material and Methods:We analysed data from the US Surveillance, Epidemiology, and End Results (SEER) program .We fitted survival models adjusted by age, gender, race, year, surgery, and relative risk of primary mesothelioma in the county of residence (proxy for individual asbestos exposure).We estimated hazard ratios [HR] with reference to non-irradiated patients.We distinguished between scattered and direct irradiation to study the doseresponse. Results:We observed 300 mesotheliomas (264 pleural; 32 peritoneal; 4 others) among 913,873 patients.EBRT increased the risk of mesothelioma (any site; HR 1.36, 95%CI 1.05-1.76).We observed an increased risk of pleural mesothelioma (HR for EBRT 1.35, 95%CI 1.02-1.78),but we did not find signs of a dose-response relationship (HR for scattered irradiation 1.35; HR for direct irradiation 1.36).On the opposite, only direct peritoneal irradiation was associated with peritoneal mesothelioma (HR 2.13,, particularly for latencies ≥10 years (HR 3.19,.A competing risks analysis revealed that the clinical impact of radiationinduced mesothelioma was limited by the high frequency of competing events.The cumulative incidence function of mesothelioma after 40 years of observation was very low (non-irradiated patients: 0.00031, irradiated patients: 0.00056). Conclusion:EBRT is a determinant of mesothelioma.Longer latency periods are associated with higher risks, while the dose-response seems non-linear.The clinical impact of mesothelioma after EBRT for primary solid cancers is very limited.

Control of radiation dose absorbed in pathological volume represents one of the challenging issues in the implementation of radionuclide therapy (RNT). This paper presents new approach based on estimation of radiopharmaceutical (RP) accumulated activity value in tumor volume, based on planar scintigraphic images of the patient and calculated radiation transport using Monte Carlo method, including absorption and scattering in biological tissues of the patient, and elements of gamma camera itself. In our research, to obtain the data, we performed modeling scintigraphy of the vial with administered to the patient activity of RP in gamma camera, the vial was placed at the certain distance from the collimator, and the similar study was performed in identical geometry, with the same values of activity of radiopharmaceuticals in the pathological target in the body of the patient. For correct calculation results, adapted Fisher–Snyder human phantom was simulated in MCNP program. In the context of our technique, calculations were performed for different sizes of pathological targets and various tumors deeps inside patient's body, using radiopharmaceuticals based on a mixed β–γ-emitting (131I, 177Lu), and clear в-emitting (89Sr, 90Y) therapeutic radionuclides. Presented method can be used for adequate assessment of the absorbed dose in the regions of interest on the basis of patient planar scintigraphy.

Daily inspections of the radiation output of accelerator radiation beams prior to patient treatment are a compulsory component of all international recommendations on quality assurance. In the classic version, such an inspection is performed using standard “wired” (connected by wires) dosimetric equipment, such as calibrated ionization chambers or detector matrices. However, in the case of testing of a large number of accelerators and lack of appropriate radiological equipment and personnel, morning inspections may affect the beginning time of the treatment process. To accelerate this procedure, the N.N. Blokhin Russian Cancer Research Center of the Russian Academy of Medical Sciences developed and implemented a wireless technique of morning inspections using portal imaging devices for testing constancy of the absolute dose of photon radiation and assessing the accuracy of the multileaf collimator. The performance of the system for data transmission between the department server and the accelerator console, as well as the possibility of imaging, is checked simultaneously with the morning inspection.

This article presents the results of calculations by the Monte-Carlo method in the EGSnrc toolkit of the spatial distributions of absorbed energy or dose kernels in water for a pencil beam or differential pencil beam (point spread function) with the spectrum of ROKUS-M treatment machines. The photon spectrum of the ROKUS-M machines was also calculated by the Monte-Carlo method. The calculated dose-kernel results were approximated separately for the radial distribution of the primary and the scattered component of dose kernels by sums of exponential functions divided by the squared radius for a differential pencil beam and by the radius for a pencil beam. This approximation makes direct implementation possible for wellknown model-based techniques for finding 3D dose distributions in external radiation therapy. A simple analytical procedure to verify approximation formulas is proposed. It is also applicable in independent checks of dose distributions along the treat beam axis, which is an important guideline of the Radiation Therapy Quality Assurance Program.