Feasibility of template-guided attenuation correction in cat brain PET imaging.
OBJECTIVE
Attenuation correction (AC) is important in quantitative positron emission tomography (PET) imaging of medium-sized animals such as the cat. However, additional time for transmission (TX) scanning and tracer uptake is required in PET studies with animal-dedicated PET scanners because post-injection TX scanning is not available in these systems. The aim of this study was to validate a template-guided AC (TGAC) method that does not require TX PET data for AC in cat 2-deoxy-2-[F-(18)fluoro-D-glucose (FDG) brain PET imaging.


METHODS
PET scans were acquired using a microPET Focus 120 scanner. TX data were obtained using a (68)Ge point source before the injection of FDG. To generate the attention map (mu-map) template for the TGAC, a target image of emission (EM) PET was selected, and spatial normalization parameters of individual EM data onto the target were reapplied to the corresponding mu-maps. The inverse transformations of the mu-map template into the individual spaces were performed, and the transformed template was forward projected to generate the AC factor. The TGAC method was compared with measured AC (MAC) and calculated AC (CAC) methods using region of interest (ROI) and SPM analyses.


RESULTS
The ROI analysis showed that the activity of the TGAC EM PET images strongly correlated with those of the MAC data (y = 0.98x + 0.01, R(2) = 0.96). In addition, no significant difference was observed in the SPM analysis. By contrast, the CAC showed a significantly higher uptake in the deep gray regions compared to the MAC (corrected P < 0.05). The ROI correlation with MAC was worse than with the TGAC (R(2) = 0.84). In SPM analysis for the voxel-wise group comparisons between before and after the induction of deafness, only the TGAC showed equivalent results with the MAC.


CONCLUSIONS
The TGAC was reliable in cat FDG brain PET studies in terms of compatibility with the MAC method. The TGAC might be a useful option for increasing study throughput and decreasing the probability of subject movement. In addition, it might reduce the possible biological effects of long-term anesthesia on the cat brain in investigations using animal-dedicated PET scanners.
Kim
Jin Su
JS
Department of Nuclear Medicine and Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea.
Lee
Jae Sung
JS
Park
Min-Hyun
MH
Kim
Kyeong Min
KM
Oh
Seung-Ha
SH
Cheon
Gi Jeong
GJ
Song
In Chan
IC
Moon
Dae Hyuk
DH
Chung
June-Key
JK
Lee
Dong Soo
DS
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism; D001931:Brain Mapping / Q000379:methods*; D002415:Cats; D005240:Feasibility Studies; D019788:Fluorodeoxyglucose F18; D049268:Positron-Emission Tomography / Q000379:methods*
D019788:Fluorodeoxyglucose F18