RT Journal Article
SR Electronic
T1 First Pre-Clinical Study of Total-Body Dynamic PET Imaging using the mini-EXPLORER Scanner
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 394
OP 394
VO 58
IS supplement 1
A1 Zhang, Xuezhu
A1 Berg, Eric
A1 Bec, Julien
A1 Judenhofer, Martin
A1 Kapusta, Maciej
A1 Schmand, Matthias
A1 Casey, Michael
A1 Badawi, Ramsey
A1 Cherry, Simon
A1 Qi, Jinyi
YR 2017
UL http://jnm.snmjournals.org/content/58/supplement_1/394.abstract
AB 394Objectives: Non-human primate (NHP) PET imaging is of importance in translational molecular imaging research for the development of diagnostic and treatment methods for human diseases. Existing clinical whole-body PET scanners offer limited sensitivity and temporal resolution for NHP imaging. Our team has built a mini-EXPLORER PET scanner, dedicated to NHP imaging with an axial FOV of 45 cm, capable of covering the entire body of a rhesus monkey. It provides 5-fold increase in sensitivity compared with a clinical whole-body PET and offers a platform to explore the benefits of total-body imaging. Here we present our quantitative image reconstruction technique and the first dynamic total-body PET imaging using the mini-EXPLORER.Methods: The mini-EXPLORER was constructed using 192 detector modules of a Siemens mCT PET scanner. The system consisted of 8 axial rings, each formed by 24 detectors with an inner diameter of 43.4 cm. Each detector consisted of a 13×13 array of 4×4×20 mm3 LSO crystals. The system TOF resolution is 609 ps. We developed a 3D TOF list-mode OS-EM reconstruction with accurate resolution model and quantitative correction. Component-based normalization factors were estimated from a scan of an annulus source of 31-cm diameter. Attenuation factors were obtained using a separate CT scan aligned to the emission image. Scatters were estimated using the single scatter simulation algorithm and randoms were estimated using a model-based method from the delayed random sinogram in each time frame. To evaluate its capability for mid-size animal imaging, we conducted the first pre-clinical 18F-FDG PET study using a male rat, 26 cm in length (excluding tail) and weighing 431 grams. 1.14 mCi was injected. A total of twelve billion prompt events were acquired over a 2-hour dynamic scan. To demonstrate the improved image quality offered by the high sensitivity, dynamic PET data were reconstructed into 1-second, 10-second, 1-minute, and 10-minute frames. Furthermore, the list-mode data were down-sampled to generate datasets mimicking dynamic PET scans with 1/2, 1/5, 1/10 and 1/20 of the original injected dose, respectively. Regions of interest (ROIs) were drawn for major organs and the tissue time activity curves were fitted to a two-tissue-compartment model. The input function was extracted from the left ventricle for the first 40 seconds and the vena cava for the remaining 7,160 seconds.Results: Reconstructed dynamic PET images showed good image quality; even 1-second frames provided detailed and clear tracer distribution for the early dynamic imaging. The estimated kinetic parameters remain stable up to 1/10th of the injected dose. Results of 1/20th injected dose are less satisfactory, mostly caused by noise in the estimate of the blood input function due to the small size of the ROI.Conclusion: This study demonstrated that the mini-EXPLORER scanner can perform total-body dynamic PET imaging for pre-clinical mid-size animal studies at high temporal resolution and lower radiation dose than that required by current protocols. Research Support: This work was carried out under the EXPLORER consortium and was funded by NIH R01-CA170874, R01-CA206187 and a UC Davis RISE award. The authors would like to thank Brijesh Patel, Jennifer Fung, Charles Smith and Douglas Rowland from CMGI for the phantom and animal experiments.