title: Influence of monte carlo variance with fluence smoothing in VMAT treatment planning with Monaco TPS.
abstract: BACKGROUND
  The study aimed to investigate the interplay between Monte Carlo Variance (MCV) and fluence smoothing factor (FSF) in volumetric modulated arc therapy treatment planning by using a sample set of complex treatment planning cases and a X-ray Voxel Monte Carlo-based treatment planning system equipped with tools to tune fluence smoothness as well as MCV.
  
  
  METHODS
  The dosimetric (dose to tumor volume, and organ at risk) and physical characteristic (treatment time, number of segments, and so on) of a set 45 treatment plans for all combinations of 1%, 3%, 5% MCV and 1, 3, 5 FSF were evaluated for five carcinoma esophagus cases under the study.
  
  
  RESULTS
  Increase in FSF reduce the treatment time. Variation of MCV and FSF gives a highest planning target volume (PTV), heart and lung dose variation of 3.6%, 12.8% and 4.3%, respectively. The heart dose variation was highest among all organs at risk. Highest variation of spinal cord dose was 0.6 Gy.
  
  
  CONCLUSIONS
  Variation of MCV and FSF influences the organ at risk (OAR) doses significantly but not PTV coverage and dose homogeneity. Variation in FSF causes difference in dosimetric and physical parameters for the treatment plans but variation of MCV does not. MCV 3% or less do not improve the plan quality significantly (physical and clinical) compared with MCV greater than 3%. The use of MCV between 3% and 5% gives similar results as 1% with lesser calculation time. Minimally detected differences in plan quality suggest that the optimum FSF can be set between 3 and 5.
authors.affiliation: Department of Radiation Oncology, AMRI Hospitals, Kolkata, India.
authors.forename: B
authors.initials: B
authors.lastname: Sarkar
authors.forename: A
authors.initials: A
authors.lastname: Manikandan
authors.forename: M
authors.initials: M
authors.lastname: Nandy
authors.forename: A
authors.initials: A
authors.lastname: Munshi
authors.forename: P
authors.initials: P
authors.lastname: Sayan
authors.forename: N
authors.initials: N
authors.lastname: Sujatha
mesh_terms: D004938:Esophageal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D009010:Monte Carlo Method; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013131:Spine / Q000528:radiation effects