title: Real-time computed tomography dosimetry during ultrasound-guided brachytherapy for prostate cancer.
abstract: OBJECTIVE
  Ultrasound-guided implantation of permanent radioactive seeds is a treatment option for localized prostate cancer. Several techniques have been described for the optimal placement of the seeds in the prostate during this procedure. Postimplantation dosimetric calculations are performed after the implant. Areas of underdosing can only be corrected with either an external beam boost or by performing a second implant. We demonstrate the feasibility of performing computed tomography (CT)-based postplanning during the ultrasound-guided implant and subsequently correcting for underdosed areas.
  
  
  METHODS
  Ultrasound-guided brachytherapy is performed on a modified CT table with general anesthesia. The postplanning CT scan is performed after the implant, while the patient is still under anesthesia. Additional seeds are implanted into "cold spots," and the resultant dosimetry confirmed with CT.
  
  
  RESULTS
  Intraoperative postplanning was successfully performed. Dose-volume histograms demonstrated adequate dose coverage during the initial implant, but on detailed analysis, for some patients, areas of underdosing were observed either at the apex or the peripheral zone. Additional seeds were implanted to bring these areas to prescription dose.
  
  
  CONCLUSIONS
  Intraoperative postplanning is feasible during ultrasound-guided brachytherapy for prostate cancer. Although the postimplant dose-volume histograms for all patients, before the implantation of additional seeds, were adequate according to the American Brachytherapy Society criteria, specific critical areas can be underdosed. Additional seeds can then be implanted to optimize the dosimetry and reduce the risk of underdosing areas of cancer.
authors.affiliation: Department of Radiation Therapy, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA. ikaplan@caregroup.harvard.edu
authors.forename: Irving D
authors.initials: ID
authors.lastname: Kaplan
authors.forename: Paul
authors.initials: P
authors.lastname: Meskell
authors.forename: Nicklas E
authors.initials: NE
authors.lastname: Oldenburg
authors.forename: Brian
authors.initials: B
authors.lastname: Saltzman
authors.forename: Gary P
authors.initials: GP
authors.lastname: Kearney
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Holupka
mesh_terms: D004867:Equipment Design; D005240:Feasibility Studies; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*; D014463:Ultrasonography