Real-time verification of a high-dose-rate Ir-192 source position using a modified C-arm fluoroscope

Publication date: Available online 10 December 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Takayuki Nose, Masashi Chatani, Yuki Otani, Teruki Teshima, Shinichirou Kumita
PurposeHigh-dose-rate (HDR) brachytherapy misdeliveries can occur at any institution and they can cause disastrous results, even a patient death is reported elsewhere. Misdeliveries could be avoided with real-time verification methods. In 1996, we developed a modified C-arm fluoroscopic verification of an HDR Ir-192 source position in order to prevent these misdeliveries from occurring. This method provided excellent image quality sufficient to detect errors, and it has been in clinical use at our institutions for 20 years. The purpose of the current study is to introduce the mechanisms and validity of our straightforward C-arm fluoroscopic verification method.Methods and materialsConventional X-ray fluoroscopic images are degraded by spurious signals and quantum noise from Ir-192 photons, which make source verification impractical. To improve image quality, we quadrupled the C-arm fluoroscopic X-ray dose per pulse. The pulse rate was reduced by a factor of 4 to keep the average exposure compliant with the Japanese medical regulation. The images were thereby displayed with quarter-frame rates.ResultsSufficient quality was obtained to observe the source position relative to both the applicators and the anatomy. With the use of this method, 2 errors were detected among 2,031 treatment sessions for 370 patients performed within a 6-year period.ConclusionsWith the use of a modified C-arm fluoroscopic verification method, treatment errors that were otherwise overlooked were detected in real time. This method should be given consideration for widespread use.

Teaser

High-dose-rate brachytherapy misdeliveries can occur at any institution and they can cause a disastrous accident, but can be avoided with real-time verification. The simple application of conventional X-ray fluoroscopy for source position verification results only in halation due to the scattered photons from the source. We quadrupled the fluoroscopic dose per pulse to obtain better images, and reduced the pulse rate by a factor of 4 to avoid overexposure. Using this method, we detected 2 errors among 2031 sessions.


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