Quantitation in PET Beta Amyloid Imaging

An effective treatment for Alzheimer disease is important since the incidence rate is increasing with age. Beta amyloid (A) plaque is an important characteristic in AD. Therefore, Ais the most significant target for developing AD treatment. A reliable biomarker for Aimaging can aid AD diagnosis in obtaining the Apathological record, predict disease progression, monitor treatment response, and evaluate the risk of converting into AD from a preclinical stage. A novel PET tracer 18F-AV45 has recently become a standard tracer for imaging amyloid plaque in AD. Quantitation is important for 18F-AV45 imaging in early detection of amyloid plaque deposits, and sensitive treatment monitoring in AD. Conventional quantitation methods for brain imaging applied VOI analysis for compuating binding power of specific uptake ratio within VOIs, or voxel-based analysis for group differentitation. To achieve automation, both methods need the use of a template for standardized spatial normalization. However due to heterogeneous and scattered distribution of the amyloid plaque, amyloid template based on images of normal controls or AD patients is suboptimal, and leads to quantitation errors. Our aims are to propose a novel dual scan protocol for beta amyloid imaging of PET tracer AV45, semi-automatic quantitation methods using the dual scan images, and provide dual functions (biomarkers for AD) from dual scan images of the same study, as well as improving quantitation using partial volume correction for compensating system resolution limitation and the organ atrophy as commonly seen in the brain of AD patients. The assumption of this dual scan protocol is that: early-phase AV45 images might reflect the perfusion information, in additional to the well known of late-phase AV45 images for amyloid distribution. Thus the dual scans from the same AV45 study can provide dual functions simultaneously. Since early phase images are possibly related to perfusion or cerebral glucose metabolism, the uptake pattern will be less sensitive to disease stage and preserve better anatomical information. We will develop a template based on early phase AV45 images, and apply this for quantitation in AV45 imaging. Further quantitation analysis can be constructed from this dual scan protocol. So during the proposed grant period, we will verify the dual scan protocol for AV45 using retrospective dynamic AV45 data and corresponding FDG images, build up a quantitative analysis system based on the proposed dual-scan protocol, and implement quality improving procedures, all possibly without the need of an extra MRI or even FDG scans. In addition, we will also implement partial volume correction method for improving AV45 quantitation degraded by atrophy and partial volume effect. So the contribution in this grant is to propose a novel dual-scan quantitation procedure for amyloid imaging using a novel PETAV45 tracer, and build up automatic or semi-automatic image quantitation system, as well as implementation of PVC using the dual scan protocol without the need of a MRI scan. WE believe that this is the first and novel work in applying the dual-scan imaging protocol for amyloid imaging quantitation, and significant impact to amyloid imaging could be expected.

Project ID:PC10007-0399
External Project ID:NSC100-2314-B182-038