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SU‐E‐T‐449: Optimization and Evaluation: IMRT of Sinoâ,<nasal Carcinoma in Reference to ICRU 83
Author(s) -
Maria Das Joseph K,
Aziz Sait A Abdul,
Senthil Kumar S,
Verma M,
Lal P,
Kumar S
Publication year - 2014
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 - 10.1118/1.4888782
Subject(s) - nuclear medicine , medicine , dosimetry
Purpose: Estimating the potential radiobiological advantage using the sub‐volume concept (ICRU 83)in plan optimization and evaluation of IMRT for sino‐nasal carcinoma. Methods: Ten patients planned with IMRT were selected retrospectively. Two plans were generated for each patient with 7 coplanar field arrangements. The PTV was prescribed 60Gy/30# with an unedited expansion from CTV (CC=5mm, ML=4mm and AP=4mm) and the in‐air PTV filled with a virtual bolus 1cm thick. Proximity structures were defined as per the guidelines. Plan1 was optimized and evaluated based on ICRU 50/62, whereas plan2 was based incorporating the ICRU 83 approach. The dosimetric parameters, including CI, HI, MU were compared and radiobiological metrics estimated using the Biosuite software (NTCP‐LKB model & EUD). The paired T‐test was used to assess the statistical significance of differences of similar parameters between the plans. Results: The mean±sd of PTV was 230.21±88.13cc, where as the sub‐volume PTV was 3.09±1.47cc. PTV dosimetric parameters i.e., D2%, D98%, D95%, D50%, etc., CI and HI were similar for both plans, but OAR and PRV showed reduction in D2%, Dmax, Dmean for plan2 compared with plan1. D2% of optic chiasm 53.66±0.90 vs. 52.47±0.89, p = 0.004; left optic nerve 54.91±1.54 vs. 53.67±1.56, p = 0.001; left retina 54.00±1.34 vs. 51.82±2.52, p = 0.005 for plan1 and plan2 respectively while Dmax, Dmean for other OARs and PRVs demonstrated a similar trend. NTCP for optic chiasm was 7.71±2.86 vs. 5.62±2.24, p = 0.005 without fractionation effect, whereas it was 4.42±2.11 vs. 2.80±1.46, p = 0.006 with fractionation effect for plan1 and plan2 respectively. Similar trend were observed for other OARs and EUDs.7% increase in MU for plan2 was observed. Conclusion: Incorporating the sub volume concept of ICRU 83 in IMRT optimization and evaluation may Resultin reduction of doses to OAR and lower / safer NTCP without compromising TCP. The authors are acknowledging Dr. Julien Uzan and Professor Alan Nahum, Clatterbridge Cancer Centre, Wirral, UK for guidance and sharing the Biosuite software for radiobiological evaluation.