Patient daily treatment verification using MLC log files. (September 2016)

• Record Type: Journal Article
• Authors: Defoor, D.; Papanikolaou, N.; Stathakis, S.
• Is Part Of: Physica medica. Volume 32(2016)Supplement 3
• Page Start: 196
• Publication Date: 2016-09
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2016.07.668
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: To investigate the viability of patient specific IMRT QA method which uses MLC log files to recreate a delivered fluence and compare to the planned fluence. Materials and methods: A Varian Novalis Tx equipped with a HD120 MLC was used in this study. A total of 40 patients of both VMAT and step and shoot of various sites were used. Error containing plans were generated for 5 of the 40 patients. The errors introduced were MLC shifts, gantry angle errors and collimator errors. The treatment plans were delivered in air and the MLC log files recorded. An in-house MatLab program was used to recreate the planned fluence from the dicomRT file for reference and recreate the delivered fluence using data from the MLC log files. The resulting beam fluence maps and composite fluence maps were then compared using the gamma index. Gamma passing percentages were then compared to the results of the original IMRT QA (performed using the Delta 4 to establish a correlation and compare error detection capabilities. Results: The overall mean gamma values for the Delta 4 and the fluence comparisons were similar. Gamma passing percentages for the Delta 4 were 96.9% while the fluence comparisons resulted in averages of 99.7% and 98.8% for 3%/3 mm and 2%/2 mm respectively. The error detection capabilities of the fluence comparison method was on par with that of the Delta 4 . Conclusion: Using fluences created from MLC log files for patient specific IMRT QA is a valid alternative to traditional methods. The ease of use and efficiency of the fluence method makes it an attractive option for routine patient specific IMRT QA.