Minimizing variation in uptake times in a busy multi- camera PET/CT oncology clinic

Objectives The time from tracer injection to imaging affects standardized uptake values and lesion contrast. Thus, a uniform uptake time is highly desirable especially for patients being imaged multiple times during the course of their cancer therapy. Our objective for this study was to evaluate the effectiveness of countdown clocks and visual monitoring to minimize the variation in radiotracer uptake times.

Methods The goal established for time from 18F-FDG tracer injection to the beginning of PET imaging was 60 minutes. In a two camera PET/CT clinic, three uptake rooms were setup. Each room was outfitted with a video camera to allow monitoring of patients by the nuclear technicians from the PET/CT control room. A 45 minute digital countdown clock was placed in each room, in a location clearly visible by the video monitors. Upon tracer injection, the countdown clock was started. Patients then would be taken to the restroom for voiding then placed on the camera table for imaging, initially a CT scan for attenuation correction purposes, followed by PET imaging. Tracer injection times and the start of PET imaging was recorded.

Results There were a total of 194 patients evaluated. The average tracer uptake tie was 60.9 +/- 11.9 minutes. A total of 166 patients (86%) fell within the 50 to 70 minute time window, and 178 (92%) fell within the 45 minute to 75 minute time window. A subgroup analysis was done on 26 patients. This found that for uptake times between 50 and 70 minutes, there was not a significant difference in average liver SUV values.

Conclusions A system utilizing countdown clocks and video monitoring enables a high patient throughput while minimizing variation in uptake times.