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SU‐E‐T‐145: Patient Specific Quality Assurance ‐ Not Just Stamp Collecting
Author(s) -
Barnett E,
Moseley D,
Comsa D,
Abbas A,
van Prooijen M,
Yeung I
Publication year - 2011
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 - 10.1118/1.3612096
Subject(s) - pinnacle , quality assurance , standard deviation , radiation treatment planning , nuclear medicine , computer science , mathematics , statistics , medical physics , algorithm , medicine , radiation therapy , radiology , external quality assessment , pathology
Purpose: To assess the feasibility of using MapCheck 2D dose maps to improve quality in radiation therapy. Methods: A MapCheck2 device is used to validate each inverse planned step and shoot IMRT field at our centre. To date over 2000 fields have been measured. It is of interest to use this wealth of data effectively to establish appropriate control limits by applying principals of statistical process control, change planning practice if required as well as evaluate beam model performance. An application has been developed that generates a report comparing the measured 2D dose maps with the planar dose maps exported from the Pinnacle treatment planning system (Philips Radiation Oncology Systems, Madison, WI). This application reports mean error and standard deviation for each field within the following three distinct regions of the distribution consistent with AAPMˈs TG53: inner (80 – 100%), outer (0 – 20 %) and penumbra (20 – 80 %) where the percentages are of the maximum dose in the 2D dose map. Results: Results of the N=2193 measured fields are: inner field mean of the mean error −0.3%, SD 1.0%, outer field mean of mean error −0.1%, SD 1.0%, penumbra mean of mean error 0.6%, SD 2.3%. Control limits have been established. Mean error as a function of the number of control points has been reviewed and more appropriate control point limits established for treatment plan generation. A test suite of patients has been created for validation of new beam models or software releases. Conclusions: This quantity of measured data allows for a thorough evaluation of beam model performance and TPS software version in terms of IMRT delivery. By effectively analyzing the large quantity of measured clinical data, continual quality improvement becomes a less labour intensive task.