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SU‐G‐TeP4‐11: Implementation of a Non‐Measurement‐Based Patient‐Specific IMRT QA Program
Author(s) -
Chen S,
Guerrero M,
Zhang B,
Yi B,
Mossahebi S,
Prado K,
D'Souza W,
Langen K
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4957136
Subject(s) - collimator , dosimetry , medical physics , nuclear medicine , radiation treatment planning , medicine , monitor unit , computer science , radiation therapy , radiology , physics , optics
Purpose: To implement a comprehensive non‐measurement‐based verification program for patient‐specific IMRT QA Methods: Based on published guidelines, a robust IMRT QA program should assess the following components: 1) accuracy of dose calculation, 2) accuracy of data transfer from the treatment planning system (TPS) to the record‐and‐verify (RV) system, 3) treatment plan deliverability, and 4) accuracy of plan delivery. Results: We have implemented an IMRT QA program that consist of four components: 1) an independent re‐calculation of the dose distribution in the patient anatomy with a commercial secondary dose calculation program: Mobius3D (Mobius Medical Systems, Houston, TX), with dose accuracy evaluation using gamma analysis, PTV mean dose, PTV coverage to 95%, and organ‐at‐risk mean dose; 2) an automated in‐house‐developed plan comparison system that compares all relevant plan parameters such as MU, MLC position, beam iso‐center position, collimator, gantry, couch, field size settings, and bolus placement, etc. between the plan and the RV system; 3) use of the RV system to check the plan deliverability and further confirm using “mode‐up” function on treatment console for plans receiving warning; and 4) implementation of a comprehensive weekly MLC QA, in addition to routine accelerator monthly and daily QA. Among 1200 verifications, there were 9 cases of suspicious calculations, 5 cases of delivery failure, no data transfer errors, and no failure of weekly MLC QA. These 9 suspicious cases were due to the PTV extending to the skin or to heterogeneity correction effects, which would not have been caught using phantom measurement‐based QA. The delivery failure was due to the rounding variation of MLC position between the planning system and RV system. Conclusion: A very efficient, yet comprehensive, non‐measurement‐based patient‐specific QA program has been implemented and used clinically for about 18 months with excellent results