title: Integral radiation dose to normal structures with conformal external beam radiation.
abstract: BACKGROUND
  This study was designed to evaluate the integral dose (ID) received by normal tissue from intensity-modulated radiotherapy (IMRT) for prostate cancer.
  
  
  METHODS
  Twenty-five radiation treatment plans including IMRT using a conventional linac with both 6 MV (6MV-IMRT) and 20 MV (20MV-IMRT), as well as three-dimensional conformal radiotherapy (3DCRT) using 6 MV (6MV-3DCRT) and 20 MV (20MV-3DCRT) and IMRT using tomotherapy (6MV) (Tomo-IMRT), were created for 5 patients with localized prostate cancer. The ID (mean dose x tissue volume) received by normal tissue (NTID) was calculated from dose-volume histograms.
  
  
  RESULTS
  The 6MV-IMRT resulted in 5.0% lower NTID than 6MV-3DCRT; 20 MV beam plans resulted in 7.7%-11.2% lower NTID than 6MV-3DCRT. Tomo-IMRT NTID was comparable to 6MV-IMRT. Compared with 6MV-3DCRT, 6MV-IMRT reduced IDs to the rectal wall and penile bulb by 6.1% and 2.7%, respectively. Tomo-IMRT further reduced these IDs by 11.9% and 16.5%, respectively. The 20 MV did not reduce IDs to those structures.
  
  
  CONCLUSIONS
  The difference in NTID between 3DCRT and IMRT is small. The 20 MV plans somewhat reduced NTID compared with 6 MV plans. The advantage of tomotherapy over conventional IMRT and 3DCRT for localized prostate cancer was demonstrated in regard to dose sparing of rectal wall and penile bulb while slightly decreasing NTID as compared with 6MV-3DCRT.
authors.affiliation: Department of Human Oncology, University of Wisconsin, Madison, WI, USA. hao@radi.med.hokudai.ac.jp
authors.forename: Hidefumi
authors.initials: H
authors.lastname: Aoyama
authors.forename: David Clark
authors.initials: DC
authors.lastname: Westerly
authors.forename: Thomas Rockwell
authors.initials: TR
authors.lastname: Mackie
authors.forename: Gustavo H
authors.initials: GH
authors.lastname: Olivera
authors.forename: Søren M
authors.initials: SM
authors.lastname: Bentzen
authors.forename: Rakesh R
authors.initials: RR
authors.lastname: Patel
authors.forename: Hazim
authors.initials: H
authors.lastname: Jaradat
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Tome
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ritter
authors.forename: Minesh P
authors.initials: MP
authors.lastname: Mehta
mesh_terms: D006801:Humans; D008297:Male; D010413:Penis / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012007:Rectum / Q000528:radiation effects*