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Sci‐Sat AM (2) Therapy‐05: Early Experience with a Clinical TomoTherapy Unit
Author(s) -
Gerig L,
MacPherson M,
Malone S,
MacRae R,
Carty K,
Montgomery L,
Fox G,
Clark B
Publication year - 2006
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 - 10.1118/1.2244701
Subject(s) - tomotherapy , quality assurance , imaging phantom , dosimetry , nuclear medicine , standard deviation , radiation treatment planning , calibration , medicine , consistency (knowledge bases) , monitor unit , mathematics , computer science , radiation therapy , medical physics , statistics , surgery , artificial intelligence , external quality assessment , pathology
In March 2005 The Ottawa Hospital Regional Cancer Center received a helical TomoTherapy Hi‐Art machine, beginning treatment September 2005. The delivery and planning systems were subjected to rigorous daily QA. Herein we report our geometric, dosimetric and uptime analysis. Daily dosimetric QA comprises output and energy checks as well as the geometric consistency of the integrated laser and couch drive systems. At least one patient treatment plan per day is delivered to a phantom for delivery quality assurance, thereby checking all integrated tomotherapy subsystems (e.g. gantry rotation speed, couch speed, dose rate, MLC, jaw calibration and modeling within the planning system). Over the first 130 treatment days the mean output was 0.5% above reference and varied about the mean with a SD of 0.32%. Approximately 1.5% (2 of 132) of output measurements exceeded our tolerance of 2% requiring the calibration to be modified twice prior to the resumption of clinical service. The beam energy was measured by the PDD at 10 and 20 cm. We found these to vary about their expectation values with standard deviations of 0.52% and 0.59% respectively. Single point doses for the Delivery QA were normally distributed with a standard deviation of 2.4%, where 92% of all points were within 3% and 97% of all points were within 5% of expected. All coronal plane film measurements had a distance to agreement of less than 3 mm. We experienced a total of 4.5 days of downtime, 2 of which are attributed to delay in parts delivery.