title: The impact of beam angle configuration of intensity-modulated radiotherapy in the hepatocellular carcinoma.
abstract: OBJECTIVE
  This treatment planning study was undertaken to evaluate the impact of beam angle configuration of intensity-modulated radiotherapy (IMRT) on the dose of the normal liver in hepatocellular carcinoma (HCC).
  
  
  METHODS
  The computed tomography datasets of 25 patients treated with IMRT for HCC were selected. Two IMRT plans using five beams were made in each patient; beams with equidistance of 72° (Plan I), and beams with a 30° angle of separation entering the body near the tumor (Plan II). Both plans were generated using the same constraints in each patient. Conformity index (CI), homogeneity index (HI), gamma index, mean dose of the normal liver (Dmean_NL), Dmean_NL difference between the two plans, and percentage normal liver volumes receiving at least 10, 20, and 30 Gy (V10, V20, and V30) were evaluated and compared.
  
  
  RESULTS
  Dmean_NL, V10, and V20 were significantly better for Plan II. The Dmean_NL was significantly lower for peripheral (p = 0.001) and central tumors (p = 0.034). Dmean_NL differences between the two plans increased in proportion to gross tumor volume to normal liver volume ratios (p = 0.002). CI, HI, and gamma indices were not significantly different for the two plans.
  
  
  CONCLUSIONS
  The IMRT plan based on beams with narrow separations reduced the irradiated dose of the normal liver, which would allow radiation dose escalation for HCC.
authors.affiliation: Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, Korea.
authors.forename: Sung Hoon
authors.initials: SH
authors.lastname: Kim
authors.forename: Min Kyu
authors.initials: MK
authors.lastname: Kang
authors.forename: Ji Woon
authors.initials: JW
authors.lastname: Yea
authors.forename: Sung Kyu
authors.initials: SK
authors.lastname: Kim
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Choi
authors.forename: Se An
authors.initials: SA
authors.lastname: Oh