title: Dosimetric impact of different multileaf collimators on prostate intensity modulated treatment planning.
abstract: OBJECTIVE
  The main purpose of this study is to perform a dosimetric comparison on target volumes and organs at risks (OARs) between prostate intensity modulated treatment plans (IMRT) optimized with different multileaf collimators (MLCs).
  
  
  BACKGROUND
  The use of MLCs with a small leaf width in the IMRT optimization may improve conformity around the tumor target whilst reducing the dose to normal tissues.
  
  
  METHODS
  Two linacs mounting MLCs with 5 and 10 mm leaf-width, respectively, implemented in Pinnacle(3) treatment planning system were used for this work. Nineteen patients with prostate carcinoma undergoing a radiotherapy treatment were enrolled. Treatment planning with different setup arrangements (7 and 5 beams) were performed for each patient and each machine. Dose volume histograms (DVHs) cut-off points were used in the treatment planning comparison.
  
  
  RESULTS
  Comparable planning target volume (PTV) coverage was obtained with 7- and 5-beam configuration (both with 5 and 10 mm MLC leaf-width). The comparison of bladder and rectum DVH cut-off points for the 5-beam arrangement shows that 52.6% of the plans optimized with a larger leaf-width did not satisfy at least one of the OARs' constraints. This percentage is reduced to 10.5% for the smaller leaf-width. If a 7-beam arrangement is used the value of 52.6% decreases to 21.1% while the value of 10.5% remains unchanged.
  
  
  CONCLUSIONS
  MLCs collimators with different widths and number of leaves lead to a comparable prostate treatment planning if a proper adjustment is made of the number of gantry angles.
authors.affiliation: Medical Physics Unit, Centro Oncologico Fiorentino, Via A. Ragionieri 101, 50019 Sesto Fiorentino, Italy.
authors.forename: Lucia Clara
authors.initials: LC
authors.lastname: Orlandini
authors.affiliation: Medical Physics Unit, Centro Oncologico Fiorentino, Via A. Ragionieri 101, 50019 Sesto Fiorentino, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Betti
authors.affiliation: Medical Physics Unit, Centro Oncologico Fiorentino, Via A. Ragionieri 101, 50019 Sesto Fiorentino, Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Fulcheri
authors.affiliation: Radiation Oncology Department, Centro Oncologico Fiorentino, Via A. Ragionieri 101, 50019 Sesto Fiorentino, Italy.
authors.forename: Marianna
authors.initials: M
authors.lastname: Coppola
authors.affiliation: Radiation Oncology Department, Centro Oncologico Fiorentino, Via A. Ragionieri 101, 50019 Sesto Fiorentino, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Cionini
keywords: Intensity modulated radiation therapy (IMRT); Multileaf collimator; Prostate treatment