Overdose problem associated with treatment planning software for high energy photons in response of Panama's accident.
OBJECTIVE
The purpose of this study was to quantify dose distribution errors by comparing actual dose measurements with the calculated values done by the software. To evaluate the outcome of radiation overexposure related to Panama's accident and in response to ensure that the treatment planning systems (T.P.S.) are being operated in accordance with the appropriate quality assurance programme, we studied the central axis and pripheral depth dose data using complex field shaped with blocks to quantify dose distribution errors.


METHODS
Multidata T.P.S. software versions 2.35 and 2.40 and Helax T.P.S. software version 5.1 B were assesed. The calculated data of the software treatment planning systems were verified by comparing these data with the actual dose measurements for open and blocked high energy photon fields (Co-60, 6MV & 18MV photons).


RESULTS
Close calculated and measured results were obtained for the 2-D (Multidata) and 3-D treatment planning (TMS Helax). These results were correct within 1 to 2% for open fields and 0.5 to 2.5% for peripheral blocked fields. Discrepancies between calculated and measured data ranged between 13. to 36% along the central axis of complex blocked fields when normalisation point was selected at the Dmax, when the normalisation point was selected near or under the blocks, the variation between the calculated and the measured data was up to 500% difference.


CONCLUSIONS
The present results emphasize the importance of the proper selection of the normalization point in the radiation field, as this facilitates detection of aberrant dose distribution (over exposure or under exposure).
Attalla
Ehab M
EM
The Department of Radiotherapy and Nuclear Medicine, National Cancer Institute, Cairo University. ehab_marouf@yahoo.com
Lotayef
Mohamed M
MM
Khalil
Ehab M
EM
El-Hosiny
Hesham A
HA
Nazmy
Mohamed S
MS
D003198:Computer Simulation; D062787:Drug Overdose / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D008954:Models, Biological; D011785:Quality Assurance, Health Care; D018788:Radioactive Hazard Release / Q000517:prevention & control*; D011879:Radiotherapy Dosage / Q000592:standards*; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D001749:Urinary Bladder Neoplasms / Q000532:radiotherapy*