Dosimetric verification of pre-treatment intensity modulated radiation therapy in the commissioning process

Background: commissioning tests are recommended before implementingintensity modulated radiation therapy. this study evaluated five different plans ofimrt mocks for different modulation indices. materials and methods: imrt testswere done in slab phantom for both 6mv and 15 mv photon energies using a 2darray ion chamber dosimeter. results: the acceptance criteria were based on3% /3mm. all tests passed the gamma criteria except for the prostate testwith 15 mv photon beams and c shape test for both 6 mv and 15 mvenergies. the ratio passing points for multi target test in 6 mv and 15 mvplans were 93.1% and 91.5%, respectively. the results of the prostate testswith 3%/3mm was 92.3% for 6mv and 91.2% for 15 mv in 4%/4 mmtolerance limit. for head and neck test with the same gamma criteria, thepercentages of the points were 93.2 and 94 for 6 mv and 15 mv plans,respectively. for c shape tests, the used gamma criteria were 4%/ 4 mm. theratio passing points were 94.9% and 94.3% for 6mv and 15mv plans,respectively. however, c shape hard test could not pass the gamma criteria of4%/ 4mm for 6mv. conclusion: results showed that by increasing the complexityof the imrt plan, the verification test must be done in a more strict-manner,because a small change in dose delivery can cause a large discrepancy betweenplanned and real dosimetry and may produce hot spots in organs or a cold spot inthe target volume.