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 Evaluation of jaws-only intensity modulated radiation therapy treatment plans using Octavius 4D system

2018 ◽  
Vol 24 (2) ◽  
pp. 75-78 ◽  
Author(s):  
Duong Thanh Tai ◽  
Luong Thi Oanh ◽  
Nguyen Dong Son ◽  
Truong Thi Hong Loan
Keyword(s):  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Patient Specific ◽  
Intensity Modulated ◽  
Angle Measurements ◽  
Gamma Index ◽  
Treatment Plans ◽  
Zero Degree ◽  
Gantry Angle ◽  
Therapy Treatment

Abstract Introduction: Jaws-Only Intensity modulated radiation therapy (JO-IMRT) is a technique uses the collimator jaws of the linear accelerator (LINAC) to delivery of complex intensity patterns. In previous studies, pretreatment patient specific quality assurance for those JO-IMRT were also performed using ionization chamber, MapCHECK2, and Octavius 4D and good agreements were shown. The aim of this study is to further verify JO-IMRT plans in 2 different cases: one with the gantry angle set equal to beam angle as in the plans and the other with gantry angle set to zero degree. Materials and Methods: Twenty-five JO-IMRT, previously verified, were executed twice for each plan. The first one used a real gantry angle, and the second one used a 0° gantry angle. Measurements were performed using Octavius 4D 1500. Results: The results were analyzed using Verisoft software. The results show that the Gamma average was 97.32 ± 2.21% for IMRT with a 0° gantry angle and 94.72 ± 2.67% for IMRT with a true gantry angle. Conclusion: In both cases, gamma index of more than 90% were found for all of our 25 JO-IMRT treatment plans.

Fraction-specific post-treatment quality assurance for active breath-hold radiation therapy

2019 ◽  
Vol 18 (03) ◽  
pp. 262-270
Author(s):  
Rajesh Thiyagarajan ◽  
Arunai Nambiraj ◽  
Durai Manigandan ◽  
Tamilseivan Singaravelu ◽  
Rajesh Selvaraj ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Post Treatment ◽  
Patient Comfort ◽  
Treatment Quality ◽  
Patient Specific ◽  
Breath Hold ◽  
Therapist Communication ◽  
Dosimetric System

AbstractPurposeThe purpose of this study is to evaluate variation in the treatment hold pattern and quantify its dosimetric impact in breath-hold radiotherapy, using fraction-specific post-treatment quality assurance.Material and MethodsA patient with lung mets treated using intensity-modulated radiation therapy (IMRT) with active breath coordinator (ABC) was recruited for the study. Treatment beam hold conditions were recorded for all the 25 fractions. The linearity and reproducibility of the dosimetric system were measured. Variation in the dose output of unmodulated open beam with beam hold was studied. Patient-specific quality assurance (PSQA) was performed with and without beam hold, and the results were compared to quantify the dosimetric impact of beam hold.ResultsThere was a considerable amount of variation observed in the number of beam hold for the given field and the monitor unit at which the beam held. Linearity and reproducibility of the dosimetric system were found within the acceptable limits. The average difference over the 25 measurements was 0·044% (0·557 to −0·318%) with standard deviation of 0·248.ConclusionPatient comfort with the ABC system and responsiveness to the therapist communication help to maintain consistent breathing pattern, in turn consistent treatment delivery pattern. However, the magnitude of dosimetric error is much less than the acceptable limits recommended by IROC. The dosimetric error induced by the beam hold is over and above the dose difference observed in conventional PSQA.

scholarly journals A method for in vivo treatment verification of IMRT and VMAT based on electronic portal imaging device

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Jun Zhang ◽  
Xiuqing Li ◽  
Miaomiao Lu ◽  
Qilin Zhang ◽  
Xile Zhang ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Measurement Data ◽  
Patient Specific ◽  
Imaging Device ◽  
Portal Imaging ◽  
Treatment Verification ◽  
Electronic Portal Imaging ◽  
In Vivo Treatment

Abstract Background Intensity-modulated radiation therapy (IMRT) and volume-modulated arc therapy (VMAT) are rather complex treatment techniques and require patient-specific quality assurance procedures. Electronic portal imaging devices (EPID) are increasingly used in the verification of radiation therapy (RT). This work aims to develop a novel model to predict the EPID transmission image (TI) with fluence maps from the RT plan. The predicted TI is compared with the measured TI for in vivo treatment verification. Methods The fluence map was extracted from the RT plan and corrections of penumbra, response, global field output, attenuation, and scatter were applied before the TI was calculated. The parameters used in the model were calculated separately for central axis and off-axis points using a series of EPID measurement data. Our model was evaluated using a CIRS thorax phantom and 20 clinical plans (10 IMRT and 10 VMAT) optimized for head and neck, breast, and rectum treatments. Results Comparisons of the predicted and measured images were carried out using a global gamma analysis of 3%/2 mm (10% threshold) to validate the accuracy of the model. The gamma pass rates for IMRT and VMAT were greater than 97.2% and 94.5% at 3%/2 mm, respectively. Conclusion We have developed an accurate and straightforward EPID-based quality assurance model that can potentially be used for in vivo treatment verification of the IMRT and VMAT delivery.

scholarly journals A comparison of the quality assurance of four dosimetric tools for intensity modulated radiation therapy

2015 ◽  
Vol 49 (3) ◽  
pp. 307-313 ◽  
Author(s):  
Jaeman Son ◽  
Taesung Baek ◽  
Boram Lee ◽  
Dongho Shin ◽  
Sung Yong Park ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Radiation Therapy ◽  
Intensity Modulated Radiation Therapy ◽  
Planning System ◽  
Treatment Planning System ◽  
Patient Specific ◽  
Intensity Modulated ◽  
Passing Rates ◽  
Passing Rate ◽  
Patient Specific Qa

Abstract Background. This study was designed to compare the quality assurance (QA) results of four dosimetric tools used for intensity modulated radiation therapy (IMRT) and to suggest universal criteria for the passing rate in QA, irrespective of the dosimetric tool used. Materials and methods. Thirty fields of IMRT plans from five patients were selected, followed by irradiation onto radiochromic film, a diode array (Mapcheck), an ion chamber array (MatriXX) and an electronic portal imaging device (EPID) for patient-specific QA. The measured doses from the four dosimetric tools were compared with the dose calculated by the treatment planning system. The passing rates of the four dosimetric tools were calculated using the gamma index method, using as criteria a dose difference of 3% and a distance-to-agreement of 3 mm. Results. The QA results based on Mapcheck, MatriXX and EPID showed good agreement, with average passing rates of 99.61%, 99.04% and 99.29%, respectively. However, the average passing rate based on film measurement was significantly lower, 95.88%. The average uncertainty (1 standard deviation) of passing rates for 6 intensity modulated fields was around 0.31 for film measurement, larger than those of the other three dosimetric tools. Conclusions. QA results and consistencies depend on the choice of dosimetric tool. Universal passing rates should depend on the normalization or inter-comparisons of dosimetric tools if more than one dosimetric tool is used for patient specific QA.

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