Development and Initial Results of a Brain PET Insert for Simultaneous 7-Tesla PET/MRI Using an FPGA-Only Signal Digitization Method

• Published in: IEEE transactions on medical imaging Vol. 40; no. 6; pp. 1579 - 1590
• Main Authors: Won, Jun Yeon, Park, Haewook, Lee, Seungeun, Son, Jeong-Whan, Chung, Yina, Ko, Guen Bae, Kim, Kyeong Yun, Song, Junghyun, Seo, Seongho, Ryu, Yeunchul, Chung, Jun-Young, Lee, Jae Sung
• Format: Journal Article
• Language: English
• Published: United States IEEE 01-06-2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bed movements; Brain; Brain PET; Cables; Cooling systems; Crystals; DAQ; Data acquisition; Detectors; Digitization; Emission analysis; Energy resolution; Field of view; Field programmable gate arrays; FPGA; Heat pipes; High definition; Human motion; Imaging; Magnetic resonance imaging; Medical imaging; Multimedia; NEMA; Neuroimaging; Positron emission; Positron emission tomography; Scanners; simultaneous PET/MRI; Spatial discrimination; Spatial resolution; Synchronism; Synchronization; Tomography; Transceivers
• ISSN: 0278-0062; 1558-254X
• DOI: 10.1109/TMI.2021.3062066

In study, we developed a positron emission tomography (PET) insert for simultaneous brain imaging within 7-Tesla (7T) magnetic resonance (MR) imaging scanners. The PET insert has 18 sectors, and each sector is assembled with two-layer depth-of-interaction (DOI)-capable high-resolution block detectors. The PET scanner features a 16.7-cm-long axial field-of-view (FOV) to provide entire human brain images without bed movement. The PET scanner early digitizes a large number of block detector signals at a front-end data acquisition (DAQ) board using a novel field-programmable gate array (FPGA)-only signal digitization method. All the digitized PET data from the front-end DAQ boards are transferred using gigabit transceivers via non-magnetic high-definition multimedia interface (HDMI) cables. A back-end DAQ system provides a common clock and synchronization signal for FPGAs over the HDMI cables. An active cooling system using copper heat pipes is applied for thermal regulation. All the 2.17-mm-pitch crystals with two-layer DOI information were clearly identified in the block detectors, exhibiting a system-level energy resolution of 12.6%. The PET scanner yielded clear hot-rod and Hoffman brain phantom images and demonstrated 3D PET imaging capability without bed movement. We also performed a pilot simultaneous PET/MR imaging study of a brain phantom. The PET scanner achieved a spatial resolution of 2.5 mm at the center FOV (NU 4) and a sensitivity of 18.9 kcps/MBq (NU 2) and 6.19% (NU 4) in accordance with the National Electrical Manufacturers Association (NEMA) standards.