title: Volumetric modulated arc therapy for prostate cancer patients with hip prosthesis.
abstract: OBJECTIVE
  To study the use of RapidArc techniques in the treatment of prostate cancer patients with hip prosthesis.
  
  
  BACKGROUND
  An important aspect of treatment planning is to achieve dose homogeneity inside the planning target volume (PTV). Especially for those patients presenting with hip prosthesis, it becomes a challenging task to achieve dose uniformity inside the PTV.
  
  
  METHODS
  Five prostate patients presenting with hip prosthesis who had undergone radical radiotherapy were selected for this study. Depending on the composition of prosthesis, a predefined set of Hounsfield values were assigned to each study set. RapidArc plans were generated on an Eclipse treatment planning system. Two arcs that include clockwise and counter-clockwise arcs were used in all these cases. To avoid beams passing through the prosthesis, a simple structure was defined around it with 1 cm margin and a strict dose constraint applied to the block during VMAT optimization.
  
  
  RESULTS
  The mean D2/D98 ratio of PTV for all the patients was 1.06 ± 0.01. The mean percentage rectum volume receiving 50 Gy, 60 Gy, 70 Gy and 75 Gy for all the patients were 33.1 ± 5.9, 21.7 ± 5.5, 13.8 ± 4.4 and 9.5 ± 3.0, respectively.
  
  
  CONCLUSIONS
  This study shows that using a double arc RapidArc technique is a simple and effective treatment method of treating prostate cancer in patients presenting with a hip prosthesis. The definition of a beam avoidance structure encompassing the prosthesis and applying strict dose constraints to it reduces the beam contribution to the prosthesis.
authors.affiliation: Peter MacCallum Cancer Centre, Victoria, Australia.
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Prabhakar
authors.affiliation: Malabar Cancer Center, Thalaserry, Kerala, India.
authors.forename: Milind
authors.initials: M
authors.lastname: Kumar
authors.affiliation: Malabar Cancer Center, Thalaserry, Kerala, India.
authors.forename: Suja
authors.initials: S
authors.lastname: Cheruliyil
authors.affiliation: Malabar Cancer Center, Thalaserry, Kerala, India.
authors.forename: Silpa
authors.initials: S
authors.lastname: Jayakumar
authors.affiliation: Malabar Cancer Center, Thalaserry, Kerala, India.
authors.forename: Satheesan
authors.initials: S
authors.lastname: Balasubramanian
authors.affiliation: Peter MacCallum Cancer Centre, Victoria, Australia.
authors.forename: Jim
authors.initials: J
authors.lastname: Cramb
keywords: Prostate cancer; Prosthesis; Radiotherapy; Treatment planning; VMAT