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 Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Vanessa Da Silva Mendes ◽  
Lukas Nierer ◽  
Minglun Li ◽  
Stefanie Corradini ◽  
Michael Reiner ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Target Volume ◽  
Planning System ◽  
Treatment Planning System ◽  
Target Coverage ◽  
Treatment Delivery ◽  
Ptv Margin ◽  
Delivery Times ◽  
Low Field ◽  
Treatment Plans

Abstract Background The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. Materials and methods 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. Results The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. Conclusions A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

scholarly journals Dosimetric Studies of Mixed Energy Intensity Modulated Radiation Therapy for Prostate Cancer Treatments

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
K. Abdul Haneefa ◽  
K. K. Shakir ◽  
A. Siddhartha ◽  
T. Siji Cyriac ◽  
M. M. Musthafa ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
High Energy ◽  
Photon Beam ◽  
Planning System ◽  
Treatment Planning System ◽  
Intensity Modulated ◽  
Mixed Beam ◽  
Mixed Field

Dosimetric studies of mixed field photon beam intensity modulated radiation therapy (IMRT) for prostate cancer using pencil beam (PB) and collapsed cone convolution (CCC) algorithms using Oncentra MasterPlan treatment planning system (v. 4.3) are investigated in this study. Three different plans were generated using 6 MV, 15 MV, and mixed beam (both 6 and 15 MV). Fifteen patients with two sets of plans were generated: one by using PB and the other by using CCC for the same planning parameters and constraints except the beam energy. For each patient’s plan of high energy photons, one set of photoneutron measurements using solid state neutron track detector (SSNTD) was taken for this study. Mean percentage of V66 Gy in the rectum is 18.55±2.8, 14.58±2.1, and 16.77±4.7 for 6 MV, 15 MV, and mixed-energy plans, respectively. Mean percentage of V66 Gy in bladder is 16.54±2.1, 17.42±2.1, and 16.94±41.9 for 6 MV, 15 MV, and mixed-energy plans, respectively. Mixed fields neutron contribution at the beam entrance surface is 45.62% less than at 15 MV photon beam. Our result shows that, with negligible neutron contributions, mixed field IMRT has considerable dosimetric advantage.

scholarly journals Differentiation of Using Flattening Filter Free Energy in Vmat Plans for Prostate Cancer

2018 ◽  
Vol 22 ◽  
pp. 01049 ◽  
Author(s):  
Yonca Yahşi Çelen ◽  
Atilla Evcin
Keyword(s):  
Prostate Cancer ◽  
Planning System ◽  
Treatment Planning System ◽  
Conformity Index ◽  
Dose Rates ◽  
Advantages And Disadvantages ◽  
Flattening Filter Free ◽  
Significant Difference ◽  
Treatment Plans ◽  
Flattening Filter

It is aimed to compare the values of conformity index (CI), homogeneity index (HI), monitor unit (MU) of volumetrically adjusted arthritis therapy (VMAT) plans using 10 prostate cancer patients with flattened filter (FF) and without flattening filter (FFF). In the study, treatment plans were prepared using 6 FF and 6 FFF in the Eclipse (ver.13.6) treatment planning system with Varian Trilogy Linear Accelerator. When planning was completed, CI averaged 0.87, HI averaged 0.44 and MU values were found to be 591 ± 26.8, 650 ± 33.06, respectively. When the PTV coverage, CI, HI and MU comparisons were made as a result of planning, there was no significant difference when comparing VMAT plans in FFF and FF energies. When we compare the MU values, the MU increase is seen when the straightening filter is removed. In both energy modes, good homogeneity in PTV was achieved with conventional francitation and close dose rates. No significant advantages and disadvantages of the unfiltered energy mode were observed in the assessment of plan quality in terms of CI, HI.

scholarly journals Feasibility Study of a Prostate Cancer FLASH Therapy Treatment With Electrons of High Energy

2021 ◽  
Author(s):  
Alessio Sarti ◽  
Patrizia De Maria ◽  
Battistoni Giuseppe ◽  
Micol De Simoni ◽  
Cinzia Di Felice ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Technological Development ◽  
High Energy ◽  
Planning System ◽  
Treatment Planning System ◽  
High Dose ◽  
Dose Rates ◽  
Very High Energy ◽  
Almost All ◽  
Very High

Abstract Prostate cancer is among the most common cancers in men and one of the leading causes of death worldwide. Different therapies are adopted for its treatment and generally radiotherapy with photons (RT) is the preferred solution in almost all cases. Up to now, in addition to photons, only protons have been implemented as alternative radiotherapy. The use of Very High Energy Electron (VHEE) beams (100-200 MeV) has been suggested in literature but the needed accelerators are more demanding, as far as space and cost are concerned, with respect to standard photon devices, with only limited advantages when compared to protons or other heavy ions. In this contribution we investigate how recent developments in electron beam therapy could reshape the landscape of prostate treatments. The VHEE Treatment Planning System obtained combining an accurate Monte Carlo (MC) simulation with a simple modelling of the FLASH effect (healthy tissues sparing at very high dose rates) is compared with conventional RT. The results demonstrate that FLASH therapy with VHEE beams of 70-130 MeV could represent a valid alternative to standard RT allowing a better sparing of the healthy tissues surrounding the tumour, in the framework of an affordable technological development.

scholarly journals The Influence of Brass Compensator Thickness and Field Size on Neutron Contamination Spectrum in 18MV Elekta SL 75/25 Medical Linear Accelerator with and without Flattening Filter: A Monte Carlo Study

2018 ◽  
Vol 8 (3Sep) ◽  
Author(s):  
A S Talebi ◽  
M Maleki ◽  
P Hejazi ◽  
M Jadidi ◽  
R Ghorbani
Keyword(s):  
Monte Carlo ◽  
Linear Accelerator ◽  
Monte Carlo Study ◽  
High Energy ◽  
Nonparametric Tests ◽  
Primary Electron ◽  
Field Size ◽  
Dose Ratio ◽  
Medical Linear Accelerator ◽  
Flattening Filter

BackgroundOne of the most significant Intensity Modulated Radiation Therapy treatment benefits is a high target to normal tissue dose ratio. To improve this advantage, an additional accessory such as a compensator is used to delivering doses. Compensator-based IMRT treatment is usually operated with an energy higher than 10 MV. Photoneutrons, which have high linear energy transfer and radiobiological effectiveness, are produced by colliding high-energy photon beams with linear accelerator structures, then they deliver the unwanted doses to patients and staff. Therefore, the neutron energy spectra should be determined in order to calculate and reduce the photoneutron risk.Objective: We have conducted a comprehensive and precise study on the influence of brass compensator thickness and field size on neutron contamination spectrum in an Elekta SL 75/25 medical linear accelerator with and without the flattening filter by Monte Carlo method.Materials and Methods: MCNPX MC Code version 2.6.0 was utilized to simulate the detailed geometry of Elekta SL 75/25 head components based on Linac’s manual. This code includes an important feature to simulate the photo-neutron interactions. Photoneutrons spectrum was calculated after the Linac output benchmarking based on tuning the primary electron beam.Results and Conclusion: Based on the Friedman and Wilcoxon nonparametric tests results (P<0.05), photoneutron fluence directly depends on the field size and compensator thickness. Moreover, the unflattened beam provides lower photoneutron fluence than the flattened beam. Photoneutrons fluence is not negligible in compensator-based IMRT treatment. However, in order to optimize treatment plans, this additional and unwanted dose must be accounted for patients.

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.

Comparison of Gamma Analyses with using Different Dosimetric Systems for Pre-Treatment Verification of Intensity Modulated Radiation Therapy

2020 ◽  
Author(s):  
Gokcen Inan ◽  
Osman Vefa Gul
Keyword(s):  
Quality Control ◽  
Radiation Therapy ◽  
Linear Accelerator ◽  
Intensity Modulated Radiation Therapy ◽  
Planning System ◽  
Treatment Planning System ◽  
Array Detector ◽  
Intensity Modulated ◽  
Treatment Plans ◽  
2D Array

Purpose: The evaluation of the agreement between calculated and measured dose plays an essential role in the quality assurance (QA) procedures of intensity-modulated radiation therapy (IMRT). This study aimed to compare gamma analysis using Portal Dosimetry (PD), Epiqa, and 2D array detector for dose verification of radiotherapy treatment plans. Materials and Methods: Five fields step-and-shoot IMRT plan was used to performed for 20 prostate IMRT patients using the dual-energy DHX linear accelerator (Varian Medical System, Palo Alto, CA, USA). The treatment plans were created using Varian DHX Eclipse treatment planning system (TPS) version 15.1. All measurements were performed by aS500 EPID integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (1%/1 mm, 2%/2 mm 3%/2 mm and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann Whitney Test and Kruskal-Wallis Test, and p-value of p <0.01 was considered to be significant. Results: The average pass rate for 20 IMRT plans was above 95% for all devices with 2%/2 mm, 3%/2 mm and 3%/3 mm. The mean and standard deviation passing rates (γ ≤1) were found to be 99.80±0.19, 99.35±0.34 and 97.53±0.71 for PD, Epiqa and 2D array respectively. All IMRT plans passed 2%/2 mm, 3%/2 mm and 3%/3 mm gamma by more than 95% of three dosimetric systems. They are all in good agreement with the literature. Conclusion: All three devices are acceptable for quality control of IMRT. Due to the simplicity and fast evaluation process, PD can be preferred for quality control.

scholarly journals Dosimetric Evaluation of the QFix kVueTM Calypso Couch Top

2021 ◽  
Vol 20 ◽  
pp. 153303382110119
Author(s):  
Lingtong Hou ◽  
Huiqin Zhang ◽  
Xiaomei Sun ◽  
Qianqian Liu ◽  
Tingfeng Chen ◽  
...  
Keyword(s):  
Treatment Plan ◽  
Field Size ◽  
Planning System ◽  
Treatment Planning System ◽  
The Real ◽  
Depth Dose ◽  
Dosimetric Accuracy ◽  
Treatment Plans ◽  
The Difference ◽  
A Minor

Purpose: To evaluate the dosimetric accuracy of the default couch model of the QFix kVueTM Calypso couch top in the treatment planning system. Methods: With the gantry 180°, field size 20 × 20 cm, 6 MV, we measured the depth dose, off-axis dose, and dose plane of different depths in the phantom with the couch rails in and out, respectively. Isocenter doses at different angles were also obtained. The results were compared to the doses calculated using the default couch top model and the real scanned couch top model. Then we revised the default model according to the measured results. Results: With “Rails In,” the depth dose, off-axis dose, and dose plane of the default couch top model had a big difference with the dose of the real scanned couch top model and the measured result. The dose of the real scanned couch top model was much closer to the measured result, but in the region of the rail edge, the difference was still significant. With “Rails Out,” there was a minor difference between the measured result, the dose of the default couch top model and the real scanned couch top model. The difference between the measurement and the default couch top model became very small after being revised. Conclusions: It is better to avoid the beam angle passing through the couch rails in treatment plans, or you should revise the parameter of the QFix kVueTM Calypso couch top model based on the measured results, and verify the treatment plan before clinical practice.

scholarly journals COLLIMATOR EXCHANGE EFFECT OF MEGAVOLTAGE PHOTON BEAMS AND ITS IMPACT ON CLINICAL DOSIMETRY

2020 ◽  
pp. 1-4
Author(s):  
Shachindra Goswami ◽  
Bhaveshwar Yadav ◽  
Shashi Bhushan Sharma ◽  
Mithu Barthakur ◽  
Pranjal Goswami ◽  
...  
Keyword(s):  
Linear Accelerator ◽  
High Energy ◽  
Field Size ◽  
Data Sets ◽  
Photon Beams ◽  
Linear Accelerators ◽  
Exchange Effect ◽  
Maximum Percentage ◽  
Percentage Difference ◽  
Collimator Scatter Factor

AIM To determine the Collimator Exchange Effect (CEE) for telecobalt unit (Bhabhatron -II TAW) and Linear accelerator unit (Varian Trilogy). MATERIALS AND METHOD The study was carried out in Bhabhatron-II TAW Telecobalt machine and Varian Trilogy Linear Accelerator. The study was done to find the collimator scatter factor (S¬c) for rectangular fields at 5 and 10gm/cm2 depths using indigenously designed mini phantom. Three sets of electrometer reading were noted for the irradiation of each field size and the average was taken for calculation. Sc values for different rectangular fields were then calculated from these data sets and the CEE at two depths (5 and 10 gm/cm2) for the 6MV and 15MV photon and Co-60 gamma beam were calculated. RESULTS The values of Sc obtained for the rectangular fields as alternatively defined by X & Y jaws are different for high energy photon beams indicating CEE. The maximum percentage difference between the Sc of the corresponding collimator settings for the Bhabhatron-II TAW unit for depths 5 and 10gm/cm2 were found to be 0.42% and 0.5% respectively. Sc values for 6MV and 15MV photon beams were found to be higher when Y-jaw (upper jaw) acts as the longer side of the rectangular field. The maximum percentage difference between the Sc values of the corresponding collimator settings for 6MV at depths 5 and 10gm/cm2 were 2.74% and 2.87% respectively whereas for 15 MV the differences were 3% and 2.99%. CONCLUSION The CEE of Cobalt Teletherapy units can be ignored in clinical dosimetry. However, the CEE of Linear Accelerators having energies 6MV & 15MV should be taken into consideration. A two dimensional table of Sc should be generated for rectangular fields during MU calculations in Linear Accelerators. For TPS based calculations, the generated data should be incorporated during beam modeling for accurate dose delivery in clinical dosimetry.

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.

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