METHODS
IMRT treatment fields larger than 15 cm were planned. TPS created
two new sub-fields by splitting each original field. IMRT
plans of 14 overlapping complementary binary sub-fields were
sent to virtual phantom of TPS for quality assurance (QA) calculations
by setting all gantry and collimator angles zero. The measurements
at linac were taken using 2D-ion chamber lattice and
film both placed at 5 cm depth in solid phantom at QA conditions.
RESULTS
According to different analyze criterias, consistence of dose
fluence related to all fields and sub-fields were found respectively
between 81%–99.2% and 80.4%–99.7% by 2D-Array
ion chamber system.
CONCLUSION
As a result there was no statistically significant difference between
calculated and measured dose distributions in overlap
regions of two split fields derived from fields larger than 15
cm.
Keywords: Split fields; gamma-index analysis; quality assurance; overlap region; intensity modulated radiation therapy
