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SU‐E‐E‐03: Advantageous Liver Sparing by Non‐Coplanar Volumetric Modulated Arc Therapy to Intrahepatic Malignancy: A Dosimetric and Feasibility Study
Author(s) -
Tsai YiChun
Publication year - 2011
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 - 10.1118/1.3611557
Subject(s) - tomotherapy , nuclear medicine , medicine , dosimetry , radiation therapy , malignancy , radiology , pathology
Purpose: Volumetric modulated arc therapy (VMAT) has been an evolving technique with improved conformity, normal organ sparing, and the additional freedom of non‐coplanar beam design as compared to helical tomotherapy. This study was to compare the dose‐volume liver sparing effect between coplanar (C) with and without non‐coplanar (NC) design for volumetric modulated arc therapy (VMAT), and to verify the delivery accuracy in patients with liver malignancy treated by the integrated NC‐VMAT. Methods: Sixteen patients with intrahepatic malignancies were planned with VMAT using coplanar with and without the additional non‐coplanar beams. All the prescribed doses were normalized to the fraction size of 2 Gy. The dose‐volume data of liver were calculated by the total liver minus the gross tumor volume. The mean dose, volume fraction receiving more than certain dose x Gy (Vx), and effective volume of liver (Veff) were compared with paired Student t test. Seven patients treated by the integrated NC‐VMAT were verified for dose accuracy using 2‐dimensional array method (MapCheck2). Results: With comparable target coverage, NC‐VMAT provided significantly better liver sparing effect than C‐VMAT in mean dose (16.52±7.8 Gy vs. 17.9±8.9 Gy, p=0.02), V5 (50.3±15.2% vs. 53.8±16.6%, p=0.02), V10 (33.1±10.8% vs. 35.3±13.1%, p=0.08), V20 (24.6±10.3% vs. 26.6±12.2%, p=0.04), V30 (20.1±10.3% vs. 22.0±11.9%, p=0.02), and Veff (9.6±5.2% vs. 10.6±5.9%., p=0.03), respectively. Among the 7 patients treated by NC‐VMAT with the average delivery time of 368±105 seconds, All but one patient with the dose accuracy met the 3%/3mm criteria of more than 95%, and all patients completed the treatment with no more than grade 2 liver toxicity. Conclusions: Liver is a sensitive organ to even low‐dose irradiation, is located asymmetrically in the abdomen, and has irregular shape. NC‐VMAT may be advantageous in liver sparing and feasible for the accurate delivery.