NEMA performance evaluation of the DISCOVERY MI 25 cm axial extent digital PET/CT scanner

Objectives: The DISCOVERY MI digital PET/CT scanner from GE healthcare has a modular design allowing for 15, 20, and 25 cm axial extents (3, 4 or 5 rings). Several 3 and 4 ring systems have been installed and their NEMA NU2-2012 performance characteristics have been previously presented; however, there have been no results from a 5 ring system. In this abstract we present the NEMA NU2-2012 results of the first installed 5 rings system from 2 sites and compare them with those from a 4 ring system as well as the 25 cm axial extent GE Signa PET/MR.

Methods: The Discovery MI 5 ring PET/CT scanner is composed of 34 modules each consisting of 5 detector blocks arranged in 16x9 LYSO detector elements. Each detector element is 3.95 x 5.3 x 25 mm. Each detector block is coupled to an array of 4x3 SiPM chips arranged as a 3x2 independent channels. The scanner detector to detector diameter is 74.4cm. NEMA NU2-2012 tests including resolution (FBP and OSEM), sensitivity, count rate, accuracy and image quality were performed. Additionally, the timing resolution and energy resolution of the system were measured. Data for the 4 ring system were obtained from the literature¹ while data for PET/MR were obtained in-house.

Results: The resolution (OSEM and FBP), sensitivity, count rate, accuracy and image quality are shown in table 1. The resolution is similar between all systems since the detector element is the same. The sensitivity of the 5 ring (20.3 cps/kBq) and the PET/MR (21.5 cps/kBq) are similar since both have a 25 cm axial extent (compared to the 20 cm 4 Ring system) although they have slightly different ring diameters (74.4 vs 62.4cm). The NECR of the 5 ring system has the highest effective sensitivity (269 vs 211 kcps@21 kBq/mL for the PET/MR). Scatter fraction, correction accuracy and image quality have similar results. Conclusion: The discovery MI 5 ring digital scanner has better or comparable NEMA performance characteristics among currently installed PET/CT systems.

1. Hsu DFC, Ilan E, Peterson W, Uribe J, Lubberink M, Levin C; Studies of a Next Generation Silicon-Photomultiplier-Based Time-of-Flight PET/CT System, JNM 2017 Sep; 58(9):1511-1518.

Results:

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