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SU‐E‐T‐587: Whole IMRT, Hybrid IMRT and 3D Conformal Plan a Dosimetric Comparison for Large Target
Author(s) -
Sharma S,
Manigandan D,
Gandhi A,
Subramani V,
Sharma D,
Kumar P,
Julka P,
Rath G
Publication year - 2012
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4735676
Subject(s) - nuclear medicine , medicine
Purpose: To dosimetrically compare the whole‐IMRT, hybrid‐IMRT (combination of IMRT and 3D‐CRT) and 3D‐conformal radiotherapy (3D‐ CRT) plans for larger targets. Methods: Five previously treated patients of carcinoma cervix with para‐aortic lymph‐nodes (target length 33‐34cm) were selected. PTV‐P (PTV‐Primary), PTV‐PA (PTV‐para–aortic) and organ at risks (OARs) were defined. Three plans were generated using Eclipse TPS for Varian CL2300C/D linear accelerator using 6MV photon beam. Three plans were: (i) Whole‐IMRT: IMRT for both PTV‐P and PTV‐PA (ii) Hybrid‐IMRT: IMRT for PTV‐P and 3D‐CRT for PTV‐PA (iii) 3D‐CRT: 3D‐CRT for both PTV‐P and PTV‐PA. Prescription dose for PTV‐P is 50.4Gy and PTV‐PA is 45Gy in 28 fractions. Coverage index (CI=Target volume covered by prescription dose/Target volume), mean doses to bladder, rectum and bowel were used for plan comparison by using DVH. Integral dose (liter‐Gray) to normal tissue (i.e., patient volume minus PTV‐P and PTV‐PA) and total monitor units (MUs) required to deliver a plan was also noted. Results: The CI for PTV‐P is 0.98±0.20, 0.96±0.09, and 0.95±0.01 for Whole‐IMRT, Hybrid‐IMRT and 3D‐CRT plan and for PTV‐ PA is 0.98±0.01, 0.98±0.01, and 0.97±0.20. Maximum doses to PTV‐P are 5660.85±90.85cGy, 5640.35±70.35cGy and 5813.80±97.40cGy. Maximum doses to PTV‐PA are 5000.60±109.10cGy, 5079.85±20.25cGy and 5092.25±19.75cGy. Mean doses to the bladder are 3810±225.80cGy, 3842.10±182.70cGy and 5204±98.25cGy for Whole‐IMRT, Hybrid‐IMRT and 3D‐CRT plan, respectively. Mean doses to rectum are 3955.35±324.95cGy, 3971.15±354.15cGy and 4741.20±371.60cGy. Mean doses to bowel are 2623.35±320.85cGy, 2855.30±371.05cGy and 3011.7±433.80cGy. Average MUs required to deliver one fraction is 1285±87, 1585±186, 485±46 for Whole‐IMRT, Hybrid‐IMRT and 3D‐CRT plans, respectively. Higher integral doses to normal tissue were observed for whole‐IMRT (267.60±76 liter‐Gy) followed by hybrid‐IMRT (259.20±53 liter‐Gy) and 3D‐CRT (186.30±33 liter‐Gy). Conclusions: Whole‐IMRT is useful for larger targets compared to hybrid‐IMRT in terms of dose conformity, lesser MUs and reduced critical organ doses with little compromise on integral dose, where 3D‐CRT sacrificed the OAR sparing.