Evaluation of Peripheral Dose for Varian Trilogy Linear Accelerator

2021 ◽  
Author(s):  
Bo Yang ◽  
Tingtian Pang ◽  
Xiansong Sun ◽  
Tingting Dong ◽  
Rui Li ◽  
...  
Keyword(s):  
Linear Accelerator ◽  
Ionization Chamber ◽  
Beam Energy ◽  
Wedge Angle ◽  
Field Size ◽  
Measure Data ◽  
Interest Points ◽  
Peripheral Dose ◽  
Radiation Beam ◽  
Dosimetric System

Abstract Objective To measure and evaluate the peripheral dose(PD) for Trilogy linear accelerator in different setup condition and investigate the feasibility of the diode dosimetric system to measure the peripheral dose.Methods Peripheral dose were measured using a CC13 ionization chamber and the diode dosimetric system in a set of solid water phantom. Measurements were performed for different depths, field sizes, physical and virtual wedge, radiation beam energy and up at distance of 1cm to 31cm beyond the field edges. PD is separated into PDleakage and PDscatter by measure peripheral dose with or without scattering phantom. CRIS phantom was used for this research with the diode dosimetric system at the interest points of the breast, thyroid, and lens.Results All the measure data were normalized to isocenter. The measured PD decreases exponentially as a function of distance up to 31cm from the edge. PD shows no significant relevant to depth and it increases with the increased field size. As the physics wedge angle increase, PD increases about 1%, but enhanced dynamic wedge decreased 2-3% compared with open field. As the beam energy increase, PD decreased. All PD data difference less than 1% between CC13 ionization chamber and diode. The PD of CRIS phantom for Volume Modulated ARC Therapy (VMAT) is minimum and the mean dose for breast、thyroid and lens is 6.72 mGy、2.90 mGy and 2.37 mGy respectively.Conclusion The diode dosimetric system provides an sufficient assessment in peripheral regions of 6MV X-ray beam. PD changes because of field size、depth、beam energy etc and the assessment of PD would be helpful to evaluate the dose received by the relevant critical structures near the treatment field. Furthermore it is advantaged to use external shielding for critical organs.

Wedge angle confirmation in computer controlled wedge field

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.

scholarly journals Assessment the Photo-neutron Contamination of IMRT and 3D-Conformal Techniques Using Thermo-luminescent Dosimeter (TLD)

2019 ◽  
pp. 1-10
Author(s):  
Ebtesam M. Mohamedy ◽  
Hassan Fathy ◽  
Wafaa M. Khalil ◽  
Nadia L. Helal ◽  
Ehab M. Attalla
Keyword(s):  
Prostate Cancer ◽  
Neutron Monitor ◽  
Linear Accelerator ◽  
Ionization Chamber ◽  
High Energy ◽  
Neutron Production ◽  
Field Size ◽  
Planning System ◽  
Energy Beam ◽  
Treatment Plans

The aim of the study is to evaluate the dependence of photo-neutron production on field size, depth in phantom and distance from isocenter and also to calculate the equivalent neutron doses for PTV and OARs of IMRT and 3DCRT techniques using TLD (600/700).The Linac Siemens Oncor installed at Nasser Institute, Cairo, Egypt. TLDs, Neutron Monitor, Ionization chamber were provided by NIS, the duration of the study was from November 2017 to July 2018. 5 prostate cancer cases were selected treated with high energy beam (15MV) Linear accelerator using 3DCRT and IMRT treatment plans. The OARs were bladder, rectum and femur. Once the plans were completed, there were copied from the planning system onto the RW3 slab phantom in which pairs of TLD chips (600/700) were placed at the exact site of PTV and OARs. The results showed that: The measured photo-neutron decreases from 0.2 mSv/Gy to 0.09 mSv/Gy as increases field sizes from 2x2 cm2 to 20x20 cm2. The measured photo-neutron was maximum at dmax =0.15 mSv/Gy and decreases gradually as increases the depth in phantom reaches to 0.07 mSv/Gy at 10cm depth in phantom. The measured photo-neutron decreases from 1.5 mSv/Gy to 0.02 mSv/Gy when measured at isocenter and at 100cm along the patient couch. Using 3DCRT for PTV and OARs were ranging from 0.027 to 0.39 mSv per photon Gy and for IMRT were 0.135 to 2.34 mSv per photon Gy. In conclusion the photo-neutron production is decreases as increases field size and distance from isocenter along patient couch while increases with depth in phantom up to dmax and decreases gradually as increases depth in phantom. IMRT requires longer beam-on time than 3DCRT leading to worse OARs sparing and increase the production of photo-neutrons than 3DCRT.

scholarly journals Determination of effective source to surface distance and cutout factor in small fields in electron beam radiotherapy: A comparison of different dosimeters

2020 ◽  
Vol 26 (4) ◽  
pp. 235-242
Author(s):  
Mohamad Reza Bayatiani ◽  
Fatemeh Fallahi ◽  
Akbar Aliasgharzadeh ◽  
Mahdi Ghorbani ◽  
Benyamin Khajetash ◽  
...  
Keyword(s):  
Electron Beam ◽  
Linear Accelerator ◽  
Beam Energy ◽  
Field Size ◽  
Surface Distance ◽  
Small Fields ◽  
Dosimetry System ◽  
Electron Beam Radiotherapy ◽  
Effective Source

AbstractObjective: The main purpose of this study is to calculate the effective source to surface distance (SSDeff) of small and large electron fields in 10, 15, and 18 MeV energies, and to investigate the effect of SSD on the cutout factor for electron beams a linear accelerator. The accuracy of different dosimeters is also evaluated.Materials and methods: In the current study, Elekta Precise linear accelerator was used in electron beam energies of 10, 15, and 18 MeV. The measurements were performed in a PTW water phantom (model MP3-M). A Semiflex and Advanced Markus ionization chambers and a Diode E detector were used for dosimetry. SSDeff in 100, 105, 110, 115, and 120 cm SSDs for 1.5 × 1.5 cm2 to 5 × 5 cm2 (small fields) and 6 × 6 cm2 to 20 × 20 cm2 (large fields) field sizes were obtained. The cutout factor was measured for the small fields.Results: SSDeff in small fields is highly dependent on energy and field size and increases with increasing electron beam energy and field size. For large electron fields, with some exceptions for the 20 × 20 cm2 field, this quantity also increases with energy. The SSDeff was increased with increasing beam energy and field size for all three detectors.Conclusion: The SSDeff varies significantly for different field sizes or cutouts. It is recommended that SSDeff be determined for each electron beam size or cutout. Selecting an appropriate dosimetry system can have an effect in determining cutout factor.

scholarly journals Surface and Buildup Region Dose Measurements with Markus Parallel-Plate Ionization Chamber, GafChromic EBT3 Film, and MOSFET Detector for High-Energy Photon Beams

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Ugur Akbas ◽  
Nazmiye Donmez Kesen ◽  
Canan Koksal ◽  
Hatice Bilge
Keyword(s):  
Ionization Chamber ◽  
Parallel Plate ◽  
Incident Radiation ◽  
High Energy ◽  
Field Size ◽  
Surface Dose ◽  
Photon Beams ◽  
Radiation Beam ◽  
Mosfet Detector ◽  
Dose Measurements

The aim of the study was to investigate surface and buildup region doses for 6 MV and 15 MV photon beams using a Markus parallel-plate ionization chamber, GafChromic EBT3 film, and MOSFET detector for different field sizes and beam angles. The measurements were made in a water equivalent solid phantom at the surface and in the buildup region of the 6 MV and 15 MV photon beams at 100 cm source-detector distance for 5 × 5, 10 × 10, and 20 × 20 cm2field sizes and 0°, 30°, 60°, and 80° beam angles. The surface doses using 6 MV photon beams for 10 × 10 cm2field size were found to be 20.3%, 18.8%, and 25.5% for Markus chamber, EBT3 film, and MOSFET detector, respectively. The surface doses using 15 MV photon beams for 10 × 10 cm2field size were found to be 14.9%, 13.4%, and 16.4% for Markus chamber, EBT3 film, and MOSFET detector, respectively. The surface dose increased with field size for all dosimeters. As the angle of the incident radiation beam became more oblique, the surface dose increased. The effective measurement depths of dosimeters vary; thus, the results of the measurements could be different. This issue can lead to mistakes at surface and buildup dosimetry and must be taken into account.

scholarly journals Experimental analysis of correction factors for reference dosimetry in a magnetic field

2017 ◽  
Vol 3 (2) ◽  
pp. 803-805
Author(s):  
Nicole Brand ◽  
Stefan Pojtinger ◽  
Savas Tsitsekidis ◽  
Daniela Thorwarth ◽  
Oliver S. Dohm
Keyword(s):  
Magnetic Field ◽  
Linear Accelerator ◽  
Ionization Chamber ◽  
Field Size ◽  
Measured Signal ◽  
Correction Factors ◽  
Ionization Chambers ◽  
Field Orientation ◽  
The Magnetic Field ◽  
Phantom Material

AbstractToday, hybrid systems of linear accelerator and MRI scanner are clinically available. Therefore it is important to investigate the feasibility of reference dosimetry with ionization chambers in the presence of a magnetic field and determine correction factors. In this work, correction factors under various conditions that influence the chamber response were experimentally investigated, using a conventional 6 MV linear accelerator together with a stand-alone magnet. We found that the correction factor for a PTW31010 ionization chamber ranges from 0.9873 to 1.009 depending on the magnetic field strength, magnetic field orientation and magnetic field size. The phantom material also does have an influence on the measured signal. Therefore, reference dosimetry with ionization chambers in the presence of a magnetic field is feasible, but requires dedicated correction factors, which depend on the experimental setup.

Sign in / Sign up

Export Citation Format

Share Document