title: Dosimetric influence of photon beam energy and number of arcs on volumetric modulated arc therapy in carcinoma cervix: A planning study.
abstract: OBJECTIVE
  Aim of the present study was to compare the dosimetric impact of different photon beam energies and number of arcs in the treatment of carcinoma cervix.
  
  
  BACKGROUND
  Carcinoma cervix is a common cancer in women worldwide with a high morbidity rate. Radiotherapy is used to treat such tumours. Volumetric Modulated Arc Therapy (VMAT) is considered superior to other techniques with multiple arcs and energies.
  
  
  METHODS
  Twenty patients with carcinoma cervix underwent radiotherapy in a prospective observation study conducted at our institute. Volumetric modulated arc plans with 6 MV, 10 MV and 15 MV photon energies using single arc (SA) and dual arc (DA) were generated. Several physical indices for planning target volume (PTV) likeV95%,V100%,V110%,D98%,D50%,D2%and total number of MUs were compared. Normal Tissue Integral Dose (NTID) and dose to a shell structure PHY2.5and PHY5.0were analyzed.
  
  
  RESULTS
  Comparable dose coverage to PTV was observed for all the energies and arcs. CI for DA6MV(1.095) was better than SA6MV(1.127), SA10MV(1.116) and SA15MV(1.116). Evaluated parameters showed significant reduction in OAR doses. Mean bladder dose for DA6MV(41.90 Gy) was better than SA6MV(42.48 Gy), SA10MV(42.08 Gy) and SA15MV(41.93 Gy). Similarly,p-value for the mean rectal dose calculated was 0.001 (SA6 vs 15), 0.013 (DA6 vs 10) and 0.003 (DA6 vs 15) and subsequently favoured DA6MV. Difference in NTID was very small.
  
  
  CONCLUSIONS
  The study showed no greater advantage of higher energy, and DA VMAT plan with 6 MV photon energy was a good choice of treatment for carcinoma cervix as it delivered a highly homogeneous and conformal plan with superior target coverage and better OAR sparing.
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Girigesh
authors: G
authors: Yadav
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Manindra
authors: M
authors: Bhushan
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Abhinav
authors: A
authors: Dewan
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Upasna
authors: U
authors: Saxena
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Lalit
authors: L
authors: Kumar
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Deepika
authors: D
authors: Chauhan
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Kothanda
authors: K
authors: Raman
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Swarupa
authors: S
authors: Mitra
authors: Division of Medical Physics & Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, Sector-5, Rohini, New Delhi 110085, India.
authors: Mahammood
authors: M
authors: Suhail
keywords: Carcinoma cervix; Conformity index; Dual arc; NTID; Photon energy; VMAT