title: Intraoperative ultrasound-based planning can effectively replace postoperative CT-based planning for high-dose-rate brachytherapy for prostate cancer.
abstract: Ultrasound (US)-based planning for high-dose-rate brachytherapy allows prostate patients to be implanted, imaged, planned, and treated without changing position. This is advantageous with respect to accuracy and efficiency of treatment but is only valuable if plan quality relative to CT is maintained. This study evaluates any dosimetric impact of changing from CT- to US-based planning.
  
  
  
  Thirty patients each were randomly selected from CT-planned and US-planned cohorts. All received single fraction high-dose-rate brachytherapy (15 Gy) followed by 37.5 Gy in 15 fractions external beam radiation therapy. Prostate V90, V100, V150, V200, D90, and the dose homogeneity index were compared. For the rectum, Dmax, D0.5cc, D1cc, V10, V50, and V80 were examined. For the urethra, only Dmax and D10 were considered.
  
  
  
  US plans had smaller 200% hot spots, although the dose homogeneity index for both was 0.7 ± 0.1. On average, plans using either modality satisfied planning goals. Although several parameters were significantly different between the two modalities (p < 0.05), the absolute differences were small. Of greatest, clinical relevance was the difference in frequency with which upper dose goals were exceeded. The prostate V200 goal was exceeded in 53% of CT-planned cases, but only 20% of those planned with US. The urethral D10 goal was never exceeded using US but was exceeded in 13% of CT cases.
  
  
  
  US planning results in plans that, clinically, are dosimetrically equivalent to CT-based planning. Upper dosimetric goals are, however, exceeded less often with US than with CT.
authors.affiliation: Medical Physics Department, Odette Cancer Centre, Toronto, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Canada. Electronic address: dbatchelar@bccancer.bc.ca.
authors.forename: Deidre L
authors.initials: DL
authors.lastname: Batchelar
authors.affiliation: Department of Radiation Oncology, University of Toronto, Toronto, Canada; Department of Radiation Oncology, Odette Cancer Centre, Toronto, Canada.
authors.forename: Hans T
authors.initials: HT
authors.lastname: Chung
authors.affiliation: Department of Radiation Oncology, University of Toronto, Toronto, Canada; Department of Radiation Oncology, Odette Cancer Centre, Toronto, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Loblaw
authors.affiliation: Department of Radiation Therapy, Odette Cancer Centre, Toronto, Canada.
authors.forename: Niki
authors.initials: N
authors.lastname: Law
authors.affiliation: Department of Radiation Therapy, Odette Cancer Centre, Toronto, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cisecki
authors.affiliation: Department of Radiation Oncology, University of Toronto, Toronto, Canada; Department of Radiation Oncology, Odette Cancer Centre, Toronto, Canada.
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Morton
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007430:Intraoperative Care; D008297:Male; D058958:Organs at Risk / Q000000981:diagnostic imaging; D011182:Postoperative Care; D011184:Postoperative Period; D011349:Proctitis / Q000517:prevention & control; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D012007:Rectum / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D014521:Urethra / Q000000981:diagnostic imaging; D014526:Urethritis / Q000517:prevention & control
keywords: CT-based planning; High-dose-rate brachytherapy; Prostate cancer; Ultrasound-based planning