Demonstration of PET System Design Trade-offs Using Small Lesion Detectability as a Metric and Measured Phantom Data

PET system design involves trade-offs between cost and performance. It is a combination of capabilities that define the clinical utility of any given system design. System sensitivity and time-of-flight (TOF) timing resolution are two such parameters that influence system performance and cost. It is important to quantify the trade-offs using clinically-relevant measures prior to selecting a design. A lesion detection phantom has previously been demonstrated and is used in this work to characterize the relationships between timing resolution or system sensitivity and model observer SNR. To summarize, doubling of NEMA sensitivity resulted in detectability improvement of the same order of magnitude as a halving of coincidence timing FWHM. The trend in detectability improvement as a function of sensitivity was predicted by a square root relationship while for timing improvement, the relationship was less than that predicted by a square root. Over the range of parameters studied, change in NEMA sensitivity produced more change in detectability than improvement in timing resolution from 550 to 200 ps.