Reconstruction of Bremsstrahlung Spectrum of Medical Electron Linear Accelerators from Deep Dose Distributions in Water Phantom

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.

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Study of Analysis the Sensitivity of the Computational Environment for Radiological Research Field Size Based on Two Dimensional Dose Distribution for Water Phantom Cases

Radiology - Open Journal ◽

10.17140/roj-4-130 ◽

2020 ◽

Vol 4 (2) ◽

pp. 39-45

Author(s):

Yati Hardiyanti ◽

◽

Thareq Barasabha ◽

Choirul Anam ◽

Novitrian Novitrian ◽

...

Keyword(s):

Dose Distribution ◽

Dose Calculation ◽

Target Volume ◽

Sensitivity Study ◽

Research Field ◽

Field Size ◽

Radiation Beam ◽

Water Phantom ◽

Computational Environment ◽

Beam Parameters

Purpose This study analysed the sensitivity of the field size from variations in the target volume dimensions, depth, and position. The variations in the target volume analysis were used to determine the width of the field size. Thus, the quality control of the radiation beam can be obtained. Materials and Methods The computed tomography (CT) image of the IBA Dose 1 type of water phantom consists of 350 slices. Variations in the dimension of the target volume were modelled in 10×10×10 cm3, 10×12×10 cm3 , 10.2×10×10.2 cm3, and 15×15×15 cm3. Beam parameters use one beam of irradiation on the central axis 0°, 6 MV energy, 100 cm source-skin distance (SSD), beamlet delta x, and y set to 0.1 cm. Dose distribution in the form of the XZ isodose curve and dose profile was used to observe the field size. Results In this study, the isodose curve was successfully displayed in the XZ isodose curve. The field size’s sensitivity has been successfully reviewed from variations of the target volume, depth, and position. The target X and Z direction analysis is used in determining the width and length of the field size. Conclusion The analysis related to the field size sensitivity study was obtained from a relatively valid calculation. The field size was evaluated with variations in depth of 1.5 cm, 5 cm, 10 cm, and variations in positions of 10 cm, 12 cm, 14 cm, 18 cm, and 20 cm. This study will be used as a reference to validate the distribution of computational environment for radiotherapy research (CERR) dose in the future. Thus, the accuracy of the dose calculation can be obtained.

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Wedge angle confirmation in computer controlled wedge field

International Journal of Radiology & Radiation Therapy ◽

10.15406/ijrrt.2020.07.00270 ◽

2020 ◽

Vol 7 (3) ◽

pp. 81-86

Author(s):

Salman Farrukh

Keyword(s):

Linear Accelerator ◽

Beam Energy ◽

Wedge Angle ◽

Target Volume ◽

Field Size ◽

Published Data ◽

Linear Accelerators ◽

Water Phantom ◽

Ion Chamber ◽

Computer Controlled

Aim: The use of computer controlled wedge system is an important segment of radiotherapy and increases the uniformity of dose in the target volume. The aim of this study is to verify the virtual wedge angles from the machine setup angles in Siemens ONCOR Linear accelerator (Linac) and compare with published data of different linear accelerators as a function of beam energy and field sizes. Method and material: This experiment was carried out on Siemens ONCOR impression linear accelerator (Linac). The doses at different depth were measured by using CC13 ion chamber. During our work the source to surface distance was kept 100 cm. The square field sizes on which we worked were 10 cm2, 15cm2 and 20 cm2.The selected Virtual wedge angles for our study are 15°, 30°, 45° and 60°.This work is carried out for both photon energies 15 MV and 6 MV, tissue equivalent water phantom IBA blue water phantom inside which all the observations were taken. The LDA 99 detector for virtual wedge profile was used. The wedge angle were calculated for the Siemen’s given formula. The variation in wedge angle from machine setup angle and published data as a function of beam energy and field sizes were analyzed. Results: The variation increases with field size and wedge angle but decreases with beam energy. Conclusion: Deviations are under 3% which are acceptable before treatment planning.

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Dosimetric comparison of photon beam profile characteristics for different treatment parameters

Journal of Radiotherapy in Practice ◽

10.1017/s1460396917000292 ◽

2017 ◽

Vol 16 (4) ◽

pp. 444-450 ◽

Cited By ~ 2

Author(s):

Qurat-ul-ain Shamsi ◽

Maria Atiq ◽

Atia Atiq ◽

Saeed Ahmad Buzdar ◽

Khalid Iqbal ◽

...

Keyword(s):

Linear Accelerator ◽

Radiation Treatment ◽

Beam Profile ◽

Photon Beam ◽

Field Size ◽

Photon Beams ◽

Linear Accelerators ◽

Water Phantom ◽

Treatment Plans ◽

Profile Characteristics

AbstractPurposeTo deliver radiation doses with higher accuracy, radiation treatment through megavoltage photon beams from linear accelerators, is accepted widely for treating malignancies. Before calibrating the linear accelerators, it is essential to make a complete analysis of all photon beam profile parameters. The main objective of this exploration was to investigate the 6 and 15 MV photon beam profile characteristics to improve the accuracy of radiation treatment plans.MethodsIn this exploration, treatment parameters like depth, field size and beam energy were varied to observe their effect on dosimetric characteristics of beam profiles in a water phantom, generated by linear accelerator Varian Clinac.ResultsThe results revealed thatDmaxandDmindecreased with increasing depth but increased with increasing field sizes. Both left and right penumbras increased with increasing depth, field size and energy. Homogeneity increased with field size but decreased with depth. Symmetry had no dependence on depth, energy and field size.ConclusionAll the characteristics of photon beam dosimetry were analysed and the characteristics like homogeneity and symmetry measured by an ion chamber in a water phantom came within clinically acceptable level of 3 and 103%, respectively, thus fulfilled the requirements of standard linear accelerator specifications. This exploration can be extended to the determination of beam profile characteristics of electron and photon beams of other energies at various depths and field sizes for designing optimum treatment plans.

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Dose Distribution near Tissue In-homogeneities in Megavoltage Radiation Therapy

HNPS Proceedings ◽

10.12681/hnps.1912 ◽

2019 ◽

Vol 23 ◽

pp. 94

Author(s):

E. Katsarou ◽

K. Karava ◽

I. E. Stamatelatos ◽

J. Kalef-Ezra

Keyword(s):

Atomic Number ◽

Human Body ◽

Dose Distribution ◽

Soft Tissues ◽

Absorbed Dose ◽

Field Size ◽

Linear Accelerators ◽

Treatment Planning Systems ◽

Dose Measurements ◽

Dose Factor

The presence of an in-homogeneity inside the human body modifies the radiation dose distribution in tissue. Such disturbances are even higher close to the interface between materials of different atomic number, Z. During radiotherapy with megavolt photons a remarkable lack of particle equilibrium is displayed in the transition zones between soft tissues and either bones or devices implanted in the human body for medical purposes, resulting in large dose gradients.The disturbance in the dose distribution in soft tissue close to a high Z material in regions where the photon beam enters or exits the in-homogeneity, is quantified by the Backscatter Dose Factor (BSDF) and Forward Scatter Dose Factor (FSDF), respectively. In the present work BSDF and FSDF dependence on photon energy, material thickness, atomic number and field size were studied experimentally. For this purpose, slabs made of high Z material (aluminum, copper and lead) were inserted in a PMMA (Plexiglas) phantom. Irradiations were performed using a Co-60 teletherapy unit and two 6 MV linear accelerators. Dose measurements were carried out using MD-55 and HD-810 Gafchromic films.The results of the study showed that the presence of the in-homogeneity increased the absorbed dose in the low Z material before the in-homogeneity (BSDF >1.00) and decreased after it (FSDF <1.00). Moreover, it was found that BSDF increases as the in-homogeneity thickness increases (up to a saturation thickness). On the contrary, FSDF decreases with increasing in-homogeneity thickness. In addition, both disturbances increase with increasing Z of the in-homogeneity. Outcome of this study was high quality experimental data to be used for benchmarking BSDF and FSDF calculations performed by dedicated Monte Carlo and analytical radiotherapy treatment planning systems.

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Measurements of Electron Beam Dose Distributions in Perspex Block for Different Field Size

Journal of Physics Conference Series ◽

10.1088/1742-6596/1829/1/012025 ◽

2021 ◽

Vol 1829 (1) ◽

pp. 012025

Author(s):

Safa Sami ◽

Ban S Hameed ◽

Nabaa M Alazawy ◽

Mustafa J Al-Musawi

Keyword(s):

Electron Beam ◽

Field Size ◽

Dose Distributions ◽

Beam Dose

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Physical approach to depth dose distributions in a water phantom irradiated by a teleisotope photon beam

Medical Physics ◽

10.1118/1.594674 ◽

1980 ◽

Vol 7 (2) ◽

pp. 120-126 ◽

Cited By ~ 1

Author(s):

Sain D. Ahuja ◽

Steven L. Stroup ◽

Marion G. Bolin ◽

S. Julian Gibbs

Keyword(s):

Photon Beam ◽

Dose Distributions ◽

Water Phantom ◽

Depth Dose ◽

Physical Approach

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Erratum: Physical approach to depth dose distributions in a water phantom irradiated by a teleisotope photon beam [Med. Phys. 7 , 120 (1980)]

Medical Physics ◽

10.1118/1.594718 ◽

1980 ◽

Vol 7 (5) ◽

pp. 550-550

Author(s):

Sain D. Ahuja ◽

Steven L. Stroup ◽

Marion G. Bolin ◽

S. Julian Gibbs

Keyword(s):

Photon Beam ◽

Dose Distributions ◽

Water Phantom ◽

Depth Dose ◽

Physical Approach

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Analysis of the Physical and Radiobiological Equivalence of the Calculated and Measured Dose Distributions for Prostate Stereotactic Radiotherapy

Medical Radiology and radiation safety ◽

10.12737/1024-6177-2021-66-3-68-75 ◽

2021 ◽

Vol 66 (3) ◽

pp. 68-75

Author(s):

E. Sukhikh ◽

L. Sukhikh ◽

A. Vertinsky ◽

P. Izhevsky ◽

I. Sheino ◽

...

Keyword(s):

Radiation Therapy ◽

Dose Distribution ◽

Three Dimensional ◽

Anterior Wall ◽

Dose Distributions ◽

Stereotactic Radiation ◽

Dose Volume Histograms ◽

Dose Volume ◽

Gamma Index ◽

Measured Dose

Purpose: Carrying out the analysis of the physical and radiobiological equivalence of dose distributions obtained during the planning of hypofractionated stereotactic radiation therapy of the prostate cancer and verification using a three-dimensional cylindrical dosimeter. Material and Methods: Based on the anatomical data of twelve patients diagnosed with prostate carcinoma, stage T2N0M0 with low risk, plans were developed for stereotactic radiation therapy with volumetric modulates arc therapy (VMAT). The dose per fraction was 7,25 Gy for 5 fractions (total dose 36,25 Gy) with a normal photon energy of 10 MV. The developed plans were verified using a three-dimensional cylindrical ArcCHECK phantom. During the verification process, the three-dimensional dose distribution in the phantom was measured, based on which the values of the three-dimensional gamma index and the dose–volume histogram within each contoured anatomical structures were calculated with 3DVH software. The gamma index value γ (3 %, 2 mm, GN) at a threshold equal to 20 % of the dose maximum of the plan and the percentage of coincidence of points at least 95 % was chosen as a criterion of physical convergence of the calculated and measured dose distribution according to the recommendations of AAPM TG-218. To analyze the radiobiological equivalence of the calculated and measured dose distribution, the local control probability (TCP) and normal tissue complication probability (NTCP) criteria were used based on the calculated and measured dose–volume histograms. Contours of the target (PTV) and the anterior wall of the rectum were used for the analysis. The approach based on the concept of equivalent uniform dose (EUD) by A. Niemierko was used to calculate the values of TCP/NTCP criteria. Results: The results of physical convergence of plans for all patients on the contour of the whole body were higher than 95 % for the criteria γ (3 %, 2 mm, GN). The convergence along the PTV contour is in the range (75.5–95.2)%. The TCP and NTCP values obtained from the measured dose-volume histograms were higher than the planned values for all patients. It was found that the accelerator delivered a slightly higher dose to the PTV and the anterior wall of the rectum than originally planned. Conclusion: The capabilities of modern dosimetric equipment allow us move to the verification of treatment plans based on the analysis of TCP / NTCP radiobiological equivalence, taking into account the individual characteristics of the patient and the capabilities of radiation therapy equipment.

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Quality Assurance of Dose Distribution of Photon Beam Planning by Anisotropic Analytical Algorithm (AAA)

Bangladesh Journal of Medical Physics ◽

10.3329/bjmp.v4i1.14686 ◽

2013 ◽

Vol 4 (1) ◽

pp. 43-49

Author(s):

M Jahangir Alam ◽

Syed Md Akram Hussain ◽

Kamila Afroj ◽

Shyam Kishore Shrivastava

Keyword(s):

Quality Assurance ◽

Treatment Planning ◽

Dose Distribution ◽

Maximum Dose ◽

Photon Beam ◽

Field Size ◽

Planning System ◽

Treatment Planning System ◽

Anisotropic Analytical Algorithm ◽

Analytical Algorithm

A three dimensional treatment planning system has been installed in the Oncology Center, Bangladesh. This system is based on the Anisotropic Analytical Algorithm (AAA). The aim of this study is to verify the validity of photon dose distribution which is calculated by this treatment planning system by comparing it with measured photon beam data in real water phantom. To do this verification, a quality assurance program, consisting of six tests, was performed. In this program, both the calculated output factors and dose at different conditions were compared with the measurement. As a result of that comparison, we found that the calculated output factor was in excellent agreement with the measured factors. Doses at depths beyond the depth of maximum dose calculated on-axis or off-axis in both the fields or penumbra region were found in good agreement with the measured dose under all conditions of energy, SSD and field size, for open and wedged fields. In the build up region, calculated and measured doses only agree (with a difference 2.0%) for field sizes > 5 × 5 cm2 up to 25 × 25 cm2. For smaller fields, the difference was higher than 2.0% because of the difficulty in dosimetry in that region. Dose calculation using treatment planning system based on the Anisotropic Analytical Algorithm (AAA) is accurate enough for clinical use except when calculating dose at depths above maximum dose for small field size.DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14686 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 43-49

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Dosimetric Characterization of Small Radiotherapy Electron Beams Collimated by Circular Applicators with the New Microsilicon Detector

Applied Sciences ◽

10.3390/app12020600 ◽

2022 ◽

Vol 12 (2) ◽

pp. 600

Author(s):

Serenella Russo ◽

Silvia Bettarini ◽

Barbara Grilli Leonulli ◽

Marco Esposito ◽

Paolo Alpi ◽

...

Keyword(s):

Radiation Therapy ◽

Electron Beams ◽

High Energy ◽

Field Size ◽

The Novel ◽

Linear Accelerators ◽

Depth Dose ◽

Dosimetric Data ◽

Output Factors ◽

Dose Measurements

High-energy small electron beams, generated by linear accelerators, are used for radiotherapy of localized superficial tumours. The aim of the present study is to assess the dosimetric performance under small radiation therapy electron beams of the novel PTW microSilicon detector compared to other available dosimeters. Relative dose measurements of circular fields with 20, 30, 40, and 50 mm aperture diameters were performed for electron beams generated by an Elekta Synergy linac, with energy between 4 and 12 MeV. Percentage depth dose, transverse profiles, and output factors, normalized to the 10 × 10 cm2 reference field, were measured. All dosimetric data were collected in a PTW MP3 motorized water phantom, at SSD of 100 cm, by using the novel PTW microSilicon detector. The PTW diode E and the PTW microDiamond were also used in all beam apertures for benchmarking. Data for the biggest field size were also measured by the PTW Advanced Markus ionization chamber. Measurements performed by the microSilicon are in good agreement with the reference values for all the tubular applicators and beam energies within the stated uncertainties. This confirms the reliability of the microSilicon detector for relative dosimetry of small radiation therapy electron beams collimated by circular applicators.

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