Design and Performance of a 1 mm3 Resolution Clinical PET System Comprising 3-D Position Sensitive Scintillation Detectors

We are developing a 1-mm(3) resolution, high-sensitivity positron emission tomography (PET) system for loco-regional cancer imaging. The completed system will comprise two 16.5 x 10 cm detector panels and contain 4 608 position sensitive avalanche photodiodes (PSAPDs) coupled to arrays of 0.9 x 0.9 x 1 mm 3 LYSO crystal elements for a total of 294 912 crystal elements. For the first time, this paper summarizes the design and reports the performance of a significant portion of the final clinical PET system, comprising 1 536 PSAPDs, 98 304 crystal elements, and an activefield-of-view(FOV) of 16.5x3.3 cm. The sub-system performance parameters, such as energy, time, and spatial resolutions are predictive of the performance of the final system due to the modular design. Analysis of the multiplexed crystal flood histograms shows 84% of the crystal elements have >99% crystal identification accuracy. The 511 keV photopeakenergy resolutionwas 11.34 +/- 0.06% full-width half maximum (FWHM), and coincidence timing resolution was 13.92 +/- 0.01 ns FWHM at 511 keV. The spatial resolution was measured using maximum likelihood expectation maximization reconstruction of a grid of point sources suspended in warm background. The averaged resolution over the central 6 cm of the FOV is 1.01 +/- 0.13mm in the X-direction, 1.84 +/- 0.20 mm in the Y-direction, and 0.84 +/- 0.11 mm in the Z-direction. Quantitative analysis of acquiredmicro-Derenzo phantom images shows better than 1.2 mm resolution at the center of the FOV, with subsequent resolution degradation in the y-direction toward the edge of the FOV caused by limited angle tomography effects.