Program Information
Dosimetric Study of TMI Using Helical Tomotherapy
r phurailatpam*, J Swamidas , J Sastri , K Josi , M Mathankar , S Paul , M Sawant , P moundekar , ACTREC,TMC, Mumbai, Maharastra
Presentations
SU-E-T-337 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:The purpose of this study is to evaluate the dosimtry of TMI using Helical Tomotherapy (HT).
Methods:Whole body CT data sets of 4 patients (median age : range:12-37years) with 5mm slice thickness were used for planning in HT (TPS version 4.2.3). The contouring of the target and organ at risks (OAR) were delineated ( Oncentra Master Plan v 4.1). Two plans were generated using 5cm and 2.5 cm field widths .The modulation factor and pitch was 3 and 0.3 respectively. Dose to PTV, OARs and the dose homogeneity were evaluated. . The doses obtained were compared with the existimg literature. Dose delivery verification was carried out by point dose and 2D array measurements with ion chamber and Arc check dosimetry (Sun NuclearTM) system repectively. The prescribed dose was 14.4 Gy in 8 fractions.
Results:The mean PTV volume was 7341.28cc (sd=2353) The dose homogeneity index of PTV was 12.03(sd=2.98) for 2.5cm_FW and 14.61 (sd=1.33) for 5cm_FW.The conformation number for 2.5 and 5 cm plans are 0.6328(sd=0.09) and 0.5915 (sd=0.0376) respectively. The mean dose(Gy) to the OARs were as follows for 2.5cm_FW : eyes, lens, lungs, kidneys, heart, liver ,thyroid and testes for are 4.12,1.9,6.61,4.04,4.85,6.06,7.17 and 1.27. The mean dose(Gy) to the OARs were as follows for 5cm_FW :eyes, lens, lungs, kidneys, heart, liver ,thyroid and testes for are 4.45,3.14,6.79,4.02,5.01,6.01,10.8 and 1.33. The mean variation of the point dose as compared to the expected dose was within 2% and the gamma analysis was at 91%.
Conclusion:It was concluded that 5cm field width plans produces optimal dose volume parameters with deliverable treatment time. From this initial dissymmetric study, it was concluded that the treatment planning and the dose delivery verification was feasible considering the complexity of the TMI.
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