An evaluation of interference of inflatable penile prostheses with electromagnetic localization and tracking system.
OBJECTIVE
The Calypso system is stated by the manufacturer to be contraindicated for cases where the patient has been implanted with a penile prosthesis. This is due to concern for potential metal interference-related reduction of spatial localization and tracking accuracy. Here we quantify the localization and tracking accuracy of the Calypso system in the presence of inflatable penile prosthesis devices from three most widely used models which account for, essentially, 100% of implants in North America.


METHODS
Phantom studies were first performed to quantify the interference of Calypso localization and tracking accuracy from both varying metal (steel) masses, and from the penile prosthetic devices themselves. The interference of varying steel masses was studied as a function of two factors: (a) the mass and (b) the location of steel material. The Calypso daily quality assurance (QA) phantom with three implanted Beacon(®) transponders was used to measure any aliasing of position that might occur due to metal interference. After confirming the safety of use in phantom, we implanted Calypso Beacon(®) transponders in one patient with a previously implanted AMS Model 700 inflatable penile prosthetic device. For each of the 42 delivered treatment fractions, redundant stereotactic ultrasound (US) image guidance was performed to ensure good agreement between US and Calypso guidance.


RESULTS
We observed that a steel mass of less than 18 g did not cause any detectable positional aliasing for the Calypso tracking function. The mass of metal material measured to exist in the three penile prosthetic devices studied here (MP35N alloy) was approximately 1 g for each. No positional aliasing was observed for the three prosthetic devices in phantom, and good agreement between redundant US and Calypso was also observed in patient.


CONCLUSIONS
Both phantom and patient evaluations with the penile prosthetic devices showed no measurable interference with the Calypso system, thus indicating that accurate Calypso-based alignments can be performed in the presence of current industry standard inflatable penile prosthetic devices.
Department of Radiation Oncology, University of Utah, Salt Lake City, Utah 84112, USA.
Brian
B
Wang
Jonathan D
JD
Tward
Bill J
BJ
Salter
D000497:Alloys; D055590:Electromagnetic Phenomena; D004867:Equipment Design; D006801:Humans; D008297:Male; D008670:Metals / Q000737:chemistry; D015917:Penile Prosthesis; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D019736:Prostheses and Implants; D011785:Quality Assurance, Health Care; D015203:Reproducibility of Results
D000497:Alloys; D008670:Metals