scholarly journals Dose Distribution near Tissue In-homogeneities in Megavoltage Radiation Therapy

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.

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

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.

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

2017 ◽  
Vol 62 (5) ◽  
pp. 47-51
Author(s):  
В. Климанов ◽  
V. Klimanov ◽  
Ж. Галяутдинова ◽  
Zh. Galyautdinova ◽  
Н. Могиленец ◽  
...  
Keyword(s):  
Dose Distribution ◽  
Average Energy ◽  
Field Size ◽  
Bremsstrahlung Spectrum ◽  
Reconstruction Method ◽  
Electron Linear Accelerator ◽  
Linear Accelerators ◽  
Dose Distributions ◽  
Water Phantom ◽  
Dose Kernels

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.

POSTAL TLD AUDIT OF HETEROGENEITY CORRECTIONS IN RADIOTHERAPY IN THE CZECH REPUBLIC

2019 ◽  
Vol 186 (2-3) ◽  
pp. 373-376
Author(s):  
Michaela Kapuciánová ◽  
Daniela Ekendahl
Keyword(s):  
Czech Republic ◽  
Dose Distribution ◽  
Linear Accelerators ◽  
Relative Deviation ◽  
The Czech Republic ◽  
Dose Measurements ◽  
Advanced Version ◽  
Thermoluminescent Dosemeters

Abstract In the Czech Republic, a more advanced version of postal audit in radiotherapy (RT) is available. It covers dose measurements with thermoluminescent dosemeters (TLD) in more complex conditions of irradiation, when dose distribution is affected by heterogeneities in the irradiated volume. Relative deviation between doses measured with TLDs and doses stated by RT centre should not exceed 3%. During 2015–2017, all Czech RT centres equipped with modern linear accelerators were subjected to this more advanced TLD audit. A total of  70% of participants complied with the limit of 3% in the first round of this audit.

scholarly journals Surface Dose for Five Telecobalt Machines, 6MV Photon Beam from Four Linear Accelerators and a Hi-Art TomoTherapy

2008 ◽  
Vol 7 (5) ◽  
pp. 381-384 ◽  
Author(s):  
Rajesh A. Kinhikar
Keyword(s):  
Linear Accelerator ◽  
Photon Beam ◽  
Field Size ◽  
Surface Dose ◽  
Linear Accelerators ◽  
Thermoluminescent Dosimeters ◽  
Medical Technologies ◽  
Dose Measurements ◽  
Good Agreement

The purpose of this study was to estimate the surface dose for five telecobalt machines (four from Best Theratronics Limited, Canada, one from Panacea Medical Technologies, India), 6 MV photon beam (static) from four linear accelerators (three Varian linear accelerators and one Siemens) and Hi-Art Tomotherapy unit. The surface dose was measured with Thermoluminescent dosimeters in phantom slabs. For Tomotherapy 6 MV beam the surface dose was estimated as 32% while it was 35%, 33%, and 36% for Clinac 6EX, Clinac 2100CD, and Clinac 2100C linear accelerators, respectively. Similarly, the surface dose for 6 MV photon beam from Primus linear accelerator was estimated as 35%. Surface doses from telecobalt machines Equinox-80, Elite-80, Th-780C, Th-780, and Bhabhatron-II was found to be 30%, 29.1%, 27.8%, 29.3%, and 29.9% for 10 cm × 10 field size, respectively. Measured surface dose from all four linear accelerators were in good agreement with that of the Tomotherapy. The surface dose measurements were useful for Tomotherapy to predict the superficial dose during helical IMRT treatments.

EQUIVALENT UNIFORM DOSE SENSITIVITY TO CHANGES IN ABSORBED DOSE DISTRIBUTION

2013 ◽  
Vol 06 (01) ◽  
pp. 1250069
Author(s):  
FRANCISCO CUTANDA-HENRÍQUEZ ◽  
SILVIA VARGAS-CASTRILLÓN
Keyword(s):  
Treatment Planning ◽  
Dose Distribution ◽  
Absorbed Dose ◽  
Target Volume ◽  
Simple Expression ◽  
External Beam Radiation ◽  
Equivalent Uniform Dose ◽  
Beam Radiation ◽  
Dose Volume Histograms ◽  
Small Change

Treatment planning in external beam radiation therapy (EBRT) utilizes dose volume histograms (DVHs) as optimization and evaluation tools. They present the fraction of planning target volume (PTV) receiving more than a given absorbed dose, against the absorbed dose values, and a number of radiobiological indices can be computed with their help. Equivalent uniform dose (EUD) is the absorbed dose that, uniformly imparted, would yield the same biological effect on a tumor as the dose distribution described by the DVH. Uncertainty and missing information can affect the dose distribution, therefore DVHs can be modeled as samples from a set of possible outcomes. This work studies the sensitivity of the EUD index when a small change in absorbed dose distribution takes place. EUD is treated as a functional on the set of DVHs. Defining a Lévy distance on this set and using a suitable expansion of the functional, a very simple expression for a bound on the variation of EUD when the dose distribution changes is found. This bound is easily interpreted in terms of standard treatment planning practice.

Theoretical study of the influence of a heterogeneous activity distribution on intratumoral absorbed dose distribution

2004 ◽  
Vol 32 (1) ◽  
pp. 200-208 ◽  
Author(s):  
Ande Bao ◽  
Xia Zhao ◽  
William T. Phillips ◽  
F. Ross Woolley ◽  
Randal A. Otto ◽  
...  
Keyword(s):  
Dose Distribution ◽  
Theoretical Study ◽  
Absorbed Dose ◽  
Activity Distribution

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

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

OSL in NaCl vs. TL in LiF for absorbed dose measurements and radiation quality assessment in the photon energy range 20 keV to 1.3 MeV

2018 ◽  
Vol 112 ◽  
pp. 11-15 ◽  
Author(s):  
Maria Christiansson ◽  
Christian Bernhardsson ◽  
Therése Geber-Bergstrand ◽  
Sören Mattsson ◽  
Christopher L. Rääf
Keyword(s):  
Energy Range ◽  
Quality Assessment ◽  
Photon Energy ◽  
Absorbed Dose ◽  
Photon Energy Range ◽  
Radiation Quality ◽  
Dose Measurements

Absorbed dose measurements using a detector with an arbitrary energy response

1989 ◽  
Vol 32 (8) ◽  
pp. 821-822
Author(s):  
V. K. Lyapidevskii ◽  
R. S. Mil'shtein
Keyword(s):  
Absorbed Dose ◽  
Energy Response ◽  
Dose Measurements ◽  
Arbitrary Energy
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