Multi-institutional clinical experience with the Calypso System in localization and continuous, real-time monitoring of the prostate gland during external radiotherapy.
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.
Kupelian
Patrick
P
M. D. Anderson Cancer Center Orlando, Orlando, FL 32806, USA. patrick.kupelian@orhs.org
Willoughby
Twyla
T
Mahadevan
Arul
A
Djemil
Toufik
T
Weinstein
Geoffrey
G
Jani
Shirish
S
Enke
Charles
C
Solberg
Timothy
T
Flores
Nicholas
N
Liu
David
D
Beyer
David
D
Levine
Lisa
L
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