SU‐GG‐T‐242: The Use of a Commercial Multi‐Detector Device for Daily QA of Linear Accelerators

Zhaohui Han, Jianming Zhu, Robert Drzymala, Dharanipathy Rangaraj, Sasa Mutic, Daniel Low, Harold li

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Purpose: With the increasing number of complex treatments there is a pressing need for QA tools that can help improve QA efficiency and comprehensiveness. The clinical use of a commercial multi‐detector device for daily QA of linear accelerators is presented. Method and Materials: The DailyQA 3™ (Sun Nuclear, Melbourne, FL) device consists of 25 detectors: 5 ionization chambers for flatness, symmetry, and output check; 4 curved ionization chambers for photon energy check by studying beam flatness; 4 circular chambers with inherent attenuators for electron energy verification; 4 sets of three diodes with 5 mm spacing for light‐radiation coincidence check. During morning output check, the open 20×20 cm2 field is formed by MLC in order to check the SMLC positioning. For DMLC delivery check, a slit with 2 cm gap is programmed to move across the detector array. Results: With one exposure for each modality, we can verify that the output is within 3%, the symmetry (both axial ant transverse) and flatness are within 3%, light‐radiation coincidence is within 3 mm, and electron energy is within 3%. The flatness is an extremely sensitive indicator to the change of X‐ray energy. Our data showed that a 10% tolerance for X‐ray energy was clinical acceptable, which translates to 1MV for 6MV and 2 MV for 18 MV. This meets 2% tolerance in PDD as recommended by AAPM protocol. The QA device is able to detect 1 mm SMLC error on a daily basis. The DMLC output typically is within 3%, which approximately translates to 0.6 mm leaf positioning/motion consistency. Combined with monthly picket‐fence QA, it provides confidence in MLC positioning. Conclusion: The clinical use of this multi‐detector device has improved the efficiency and thoroughness of linear accelerator daily QA. Reasonable action level has been established by considering dosimetric relevance and clinic flow.

Original languageEnglish
Number of pages1
JournalMedical physics
Volume35
Issue number6
DOIs
StatePublished - Jun 2008

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