scholarly journals Factor 10 Expedience of Monthly Linac Quality Assurance via an Ion Chamber Array and Automation Scripts

2019 ◽  
Vol 18 ◽  
pp. 153303381987689
Author(s):  
Lawrie B. Skinner ◽  
Yong Yang ◽  
Annie Hsu ◽  
Lei Xing ◽  
Amy S. Yu ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Standard Deviation ◽  
Linear Accelerator ◽  
Data File ◽  
Field Size ◽  
Linear Accelerators ◽  
Ion Chamber ◽  
Medical Linear Accelerators ◽  
Jaw Position ◽  
Dosimetric Leaf Gap

Purpose: While critical for safe and accurate radiotherapy, monthly quality assurance of medical linear accelerators is time-consuming and takes physics resources away from other valuable tasks. The previous methods at our institution required 5 hours to perform the mechanical and dosimetric monthly linear accelerator quality assurance tests. An improved workflow was developed to perform these tests with higher accuracy, with fewer error pathways, in significantly less time. Methods: A commercial ion chamber array (IC profiler, Sun Nuclear, Melbourne, Florida) is combined with automation scripts to consolidate monthly linear accelerator QA. The array was used to measure output, flatness, symmetry, jaw positions, gated dose constancy, energy constancy, collimator walkout, crosshair centering, and dosimetric leaf gap constancy. Treatment plans were combined with automation scripts that interface with Sun Nuclear’s graphical user interface. This workflow was implemented on a standard Varian clinac, with no special adaptations, and can be easily applied to other C-arm linear accelerators. Results: These methods enable, in 30 minutes, measurement and analysis of 20 of the 26 dosimetric and mechanical monthly tests recommended by TG-142. This method also reduces uncertainties in the measured beam profile constancy, beam energy constancy, field size, and jaw position tests, compared to our previous methods. One drawback is the increased uncertainty associated with output constancy. Output differences between IC profiler and farmer chamber in plastic water measurements over a 6-month period, across 4 machines, were found to have a 0.3% standard deviation for photons and a 0.5% standard deviation for electrons, which is sufficient for verifying output accuracy according to TG-142 guidelines. To minimize error pathways, automation scripts which apply the required settings, as well as check the exported data file integrity were employed. Conclusions: The equipment, procedure, and scripts used here reduce the time burden of routine quality assurance tests and in most instances improve precision over our previous methods.

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.

Smartphone application for mechanical quality assurance of medical linear accelerators

2017 ◽  
Vol 62 (11) ◽  
pp. N257-N270
Author(s):  
Hwiyoung Kim ◽  
Hyunseok Lee ◽  
Jong In Park ◽  
Chang Heon Choi ◽  
So-Yeon Park ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Smartphone Application ◽  
Linear Accelerators ◽  
Mechanical Quality ◽  
Medical Linear Accelerators

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.

Dosimetric comparison of photon beam profile characteristics for different treatment parameters

2017 ◽  
Vol 16 (4) ◽  
pp. 444-450 ◽  
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.

scholarly journals Dose non-linearity of the dosimetry system and possible monitor unit errors on medical linear accelerators used in conventional and intensity-modulated radiation therapy

2012 ◽  
Vol 27 (4) ◽  
pp. 368-373 ◽  
Author(s):  
Wazir Muhammad ◽  
Lee Hoon ◽  
Khan Alam ◽  
Muhammad Maqbool ◽  
Gulzar Khan
Keyword(s):  
Radiation Therapy ◽  
Dose Rate ◽  
Linear Accelerator ◽  
Intensity Modulated Radiation Therapy ◽  
Monitor Unit ◽  
Linear Accelerators ◽  
Intensity Modulated ◽  
Dynamic Wedge ◽  
Dosimetry System ◽  
Medical Linear Accelerators

The purpose of this work is to study dose non-linearity in medical linear accelerators used in conventional radiotherapy and intensity-modulated radiation therapy. Open fields, as well as the enhanced dynamic wedge ones, were used to collect data for 6 MV and 15 MV photon beams obtained from the VARIAN linear accelerator. Beam stability was checked and confirmed for different dose rates, energies, and application of enhanced dynamic wedge by calculating the charge per monitor unit. Monitor unit error was calculated by the two-exposure method for open and enhanced dynamic wedge beams of 6 MV and 15 MV photons. A significant monitor unit error with maximum values of ?2.05931 monitor unit and ?2.44787 monitor unit for open and enhanced dynamic wedge beams, respectively, both energy and dose rate dependent, was observed both in the open photon beam and enhanced dynamic wedge fields. However, it exhibited certain irregular patterns at enhanced dynamic wedge angles. Dose monitor unit error exists only because of the overshoot phenomena and electronic delay in dose coincident and integrated circuits with a dependency on the dose rate and photon energy. Monitor unit errors are independent of the application of enhanced dynamic wedge. The existence of monitor unit error demands that the dose non-linearity of the linear accelerator dosimetry system be periodically tested, so as to avoid significant dosimetric errors.

scholarly journals A Study on Photoneutrons Generated in a Linear Accelerator Head using GEANT4

2018 ◽  
Vol 7 (4.27) ◽  
pp. 106
Author(s):  
Junho Ko ◽  
Yoon S Ang Kim ◽  
. .
Keyword(s):  
Electron Beam ◽  
Linear Accelerator ◽  
High Energy ◽  
Linear Accelerators ◽  
Simulation Results ◽  
Medical Linear Accelerators

Medical linear accelerators use high energy for treatment of deeply located tumors. However, linear accelerators using energy above 6 MeV are likely to cause photoneutron contamination. In this paper, we analyzed photoneutrons generated in a linear accelerator head using GEANT4 (GEometry ANd Tracking) simulation. From the simulation results, it was confirmed that the generation of photoneutrons increases in the linear accelerator head as higher the energy of the electron beam.  

scholarly journals Pretreatment Patient Specific Quality Assurance and Gamma Index Variation Study in Gantry Dependent EPID Positions for IMRT Prostate Treatments

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Siji Cyriac ◽  
M. M. Musthafa ◽  
R. Ganapathi Raman ◽  
K. Abdul Haneefa ◽  
V. T. Hridya
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Patient Specific ◽  
Linear Accelerators ◽  
Imaging Device ◽  
Gamma Index ◽  
Medical Linear Accelerators ◽  
The Difference ◽  
Gantry Angle

Pretreatment quality assurance (QA) is a major concern in complex radiation therapy treatment plans like intensity modulated radiation therapy (IMRT). Present study considers the variations in gamma index for gantry dependent pretreatment verification and commonly practiced zero gantry angle verifications for ten prostate IMRT plans using two commercial medical linear accelerators (Varian 2300 CD, Varian Clinac iX). Two verification plans (the one with all fields at the actual treatment angles and one with all fields merged to 0 degree gantry angles) for all the patients were generated to obtain dose fluence mapping using amorphous silicon electronic portal imaging device (EPID). The gamma index was found depend on gantry angles but the difference between zero and the nonzero treatment angles is in the confidence level for clinical acceptance. The acceptance criteria of gamma method were always satisfied in both cases for two machines and are stable enough to execute the patient specific pretreatment quality assurance at 0 degree gantry angle for prostate IMRTs, where limited number of gantry angles are used.

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.

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