Volumetric-Modulated Arc Radiotherapy for Carcinomas of the Pituitary Adenomas : A Treatment Planning Comparison with Fixed Field IMRT
T Sun, T Liu, Y Yin*, Shandong Cancer Hospital & Institute, Jinan, ShandongSU-E-T-591 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: A treatment planning study was performed to compare volumetric-modulated arc radiotherapy against conventional fixed field IMRT on pituitary adenomas cancer patients.
Methods: CT datasets of 10 patients affected by carcinoma of the pituitary adenomas were included and four plans were generated for each case: fixed five-Fields and seven-Fields IMRT, single (RA1)- and double (RA2)-modulated arcs with the RapidArc technique. The radiation dose was prescribed as 45 Gy in 25 fractions . DVHs were adopted for the statistics of above parameters, as well as conformal index (CI), homogeneity index (HI), dose-volumetric parameters of normal tissues, total accelerator output MUs and total treatment time.
Results: Target coverage resulted basically equivalent among four plans. CI and HI were 0.84±0.04, 0.84±0.03, 0.86±0.03, 0.85±0.04 and 9.03±1.05 8.39±1.55, 10.02±1.30, 10.59±1.30, respectively. The the V20Gy (in %) and V40Gy (in %) of brainstem were 30.48±16.84, 10.23±7.47, 21.34 ±12.2, 26.4±12.1 and 5.06±4.37, 4.27±4.49, 3.97±4.45, 4.49±4.56, repectively.
The max dose(Gy)of Optic nerve-right and Optic nerve-left were 31.87±12.04, 33.23±12.65, 28.96 ±13.42, 28.68±12.63 and 33.15±12.51, 34.15±11.51, 30.37 ±12.41,30.09±11.34 .Concerning the healthy brain tissue: V20Gy (in %) was 7.11 ± 2.1,7.92 ±2.7, 8.12 ± 1.8 and 8.0 ± 2.0, respectively. The number of computed MU/fraction were 580 ± 69 (5-IMRT), 598 ± 112 (7-IMRT),474 ±43(RA1), and 477 ± 77 (RA2) .
Conclusions: In our study, rapidarc showed improvement in organ at risk sparing with uncompromised target coverage .Rapidarc could lead to the less MU and shortor delivery time compared to IMRT