title: Multi-institutional clinical experience with the Calypso System in localization and continuous, real-time monitoring of the prostate gland during external radiotherapy.
abstract: OBJECTIVE
  To report the clinical experience with an electromagnetic treatment target positioning and continuous monitoring system in patients with localized prostate cancer receiving external beam radiotherapy.
  
  
  METHODS
  The Calypso System is a target positioning device that continuously monitors the location of three implanted electromagnetic transponders at a rate of 10 Hz. The system was used at five centers to position 41 patients over a full course of therapy. Electromagnetic positioning was compared to setup using skin marks and to stereoscopic X-ray localization of the transponders. Continuous monitoring was performed in 35 patients.
  
  
  RESULTS
  The difference between skin mark vs. the Calypso System alignment was found to be >5 mm in vector length in more than 75% of fractions. Comparisons between the Calypso System and X-ray localization showed good agreement. Qualitatively, the continuous motion was unpredictable and varied from persistent drift to transient rapid movements. Displacements > or =3 and > or =5 mm for cumulative durations of at least 30 s were observed during 41% and 15% of sessions. In individual patients, the number of fractions with displacements > or =3 mm ranged from 3% to 87%; whereas the number of fractions with displacements > or =5 mm ranged from 0% to 56%.
  
  
  CONCLUSIONS
  The Calypso System is a clinically efficient and objective localization method for positioning prostate patients undergoing radiotherapy. Initial treatment setup can be performed rapidly, accurately, and objectively before radiation delivery. The extent and frequency of prostate motion during radiotherapy delivery can be easily monitored and used for motion management.
authors.affiliation: M. D. Anderson Cancer Center Orlando, Orlando, FL 32806, USA. patrick.kupelian@orhs.org
authors.forename: Patrick
authors.initials: P
authors.lastname: Kupelian
authors.forename: Twyla
authors.initials: T
authors.lastname: Willoughby
authors.forename: Arul
authors.initials: A
authors.lastname: Mahadevan
authors.forename: Toufik
authors.initials: T
authors.lastname: Djemil
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Weinstein
authors.forename: Shirish
authors.initials: S
authors.lastname: Jani
authors.forename: Charles
authors.initials: C
authors.lastname: Enke
authors.forename: Timothy
authors.initials: T
authors.lastname: Solberg
authors.forename: Nicholas
authors.initials: N
authors.lastname: Flores
authors.forename: David
authors.initials: D
authors.lastname: Liu
authors.forename: David
authors.initials: D
authors.lastname: Beyer
authors.forename: Lisa
authors.initials: L
authors.lastname: Levine
mesh_terms: D000368:Aged; D055590:Electromagnetic Phenomena / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D011467:Prostate; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D019736:Prostheses and Implants; D018787:Radiation Oncology / Q000295:instrumentation / Q000379:methods*; D011859:Radiography