The Current Status of a Non-Invasive Arterial Monitor under Development

A non-invasive arterial monitor (NIAM) is being developed as an alternative to invasive arterial sampling to measure the input function of radiotracer uptake in PET patients. NIAM consists of dual Bismuth Germanate (BGO)-block detectors. The output was digitized at 500 MHz, and then processed to generate energy, timing and position information. System matrices were calculated for a range of geometries, allowing iterative reconstruction of tomographic images. Countrate efficiency was measured as 4.8cps/(kBq/ml) and countrate linearity was confirmed up to 330kBq/ml. The coincidence time resolution was measured using two techniques; a digital Constant Fraction Discriminator (CFD) and a Parametric Waveform Analysis (PWA). The resulting time-resolutions were; t_CFD = 7.8ns and t_PWA = 5.7ns. Spatial resolution was measured, both parallel (Deltax,y) and orthogonal (Deltaz) to the detector faces. At 140mm block separation, the measured resolution was Deltax,y = 6mm and Deltaz = 21mm. The system was simulated using the Geant4 Application for Tomographic Emission (GATE) to compare measured- vs. simulated-performance. After the dual-block validation of GATE, the performance characteristics of a simulated quad-block system were investigated.