TECHNICAL NOTE
Year : 2015 | Volume
: 40 | Issue : 4 | Page : 226--232
Impact of dose rate on accuracy of intensity modulated radiation therapy plan delivery using the pretreatment portal dosimetry quality assurance and setting up the workflow at hospital levels
Karunakaran Kaviarasu1, N Arunai Nambi Raj3, K Krishna Murthy2, A Ananda Giri Babu2, Bhaskar Laxman Durga Prasad2
1 Department of Radiation Oncology, Krishna Institute of Medical Sciences, Secunderabad, Telangana; School of Advanced Sciences, Vellore Institute of Technology University, Vellore, Tamil Nadu, India
2 Department of Radiation Oncology, Krishna Institute of Medical Sciences, Secunderabad, Telangana, India
Correspondence Address:
Karunakaran Kaviarasu
Department of Radiation Oncology, Krishna Institute of Medical Sciences, Secunderabad - 500 003, Telangana
India
The aim of this study was to examine the impact of dose rate on accuracy of intensity modulated radiation therapy (IMRT) plan delivery by comparing the gamma agreement between the calculated and measured portal doses by pretreatment quality assurance (QA) using electronic portal imaging device dosimetry and creating a workflow for the pretreatment IMRT QA at hospital levels. As the improvement in gamma agreement leads to increase in the quality of IMRT treatment delivery, gamma evaluation was carried out for the calculated and the measured portal images for the criteria of 3% dose difference and 3 mm distance-to-agreement (DTA). Three gamma parameters: Maximum gamma, average gamma, and percentage of the field area with a gamma value>1 .0 were analyzed. Three gamma index parameters were evaluated for 40 IMRT plans (315 IMRT fields) which were calculated for 400 monitor units (MU)/min dose rate and maximum multileaf collimator (MLC) speed of 2.5 cm/s. Gamma parameters for all 315 fields are within acceptable limits set at our center. Further, to improve the gamma results, we set an action level for this study using the mean and standard deviation (SD) values from the 315 fields studied. Forty out of 315 IMRT fields showed low gamma agreement (gamma parameters>2 SD as per action level of the study). The parameters were recalculated and reanalyzed for the dose rates of 300, 400 and 500 MU/min. Lowering the dose rate helped in getting an enhanced gamma agreement between the calculated and measured portal doses of complicated fields. This may be attributed to the less complex motion of MLC over time and the MU of the field/segment. An IMRT QA work flow was prepared which will help in improving the quality of IMRT delivery.
How to cite this article:
Kaviarasu K, Raj N A, Murthy K K, Babu A A, Prasad BL. Impact of dose rate on accuracy of intensity modulated radiation therapy plan delivery using the pretreatment portal dosimetry quality assurance and setting up the workflow at hospital levels.J Med Phys 2015;40:226-232
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How to cite this URL:
Kaviarasu K, Raj N A, Murthy K K, Babu A A, Prasad BL. Impact of dose rate on accuracy of intensity modulated radiation therapy plan delivery using the pretreatment portal dosimetry quality assurance and setting up the workflow at hospital levels. J Med Phys [serial online] 2015 [cited 2023 Mar 28 ];40:226-232
Available from: https://www.jmp.org.in/article.asp?issn=0971-6203;year=2015;volume=40;issue=4;spage=226;epage=232;aulast=Kaviarasu;type=0 |
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