TY - JOUR T1 - A Semi-Automated Method for Regional Cerebral Uptake Analysis in Micro PET-CT JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 156 LP - 156 VL - 61 IS - supplement 1 AU - Christopher Leatherday AU - Virginie Lam AU - Jan Boucek AU - Liesl Celliers Y1 - 2020/05/01 UR - http://jnm.snmjournals.org/content/61/supplement_1/156.abstract N2 - 156Introduction: For nuclear medicine imaging of neurodegenerative disorders, it is important to be able to assess localised uptake within substructures of the brain. Micro CT produces very little intrinsic cerebral soft tissue contrast; accurate registration to an atlas can provide a means to extract cerebral regions of interest. We present a semi-automated method to co-register a T1 MRI-derived mouse brain template to a group of PET-CT images. Methods: The method involves first cropping a subject CT image to include only the skull region and converting it to a binary mask. The binary skull mask is then filled to create a “skull cavity mask”, which has the same overall shape as the brain. A T1 weighted MRI atlas developed by the Australian Mouse Brain Mapping Consortium (AMBMC)1 is then co-registered to the skull cavity mask via an affine transformation using FSL2 software. Each subsequent subject CT is then skull cropped and binary masked before being co-registered to the first CT using affine transformations, which are then applied to each corresponding PET. The method was tested on a cohort of 7 12 month old mice (1 female wild type control, 6 double transgenic Alzheimer’s amyloidosis model (APP/PS1) (3 male)) who were intravenously administered 20 MBq of the amyloid tracer 18F-NAV4694 (NAV) before a 30 minute dynamic acquisition on a Bioscan BioPET/CT. Results: Figure 1 shows a skull-cropped CT with its skull cavity mask and the AMBMC atlas after CT co-registration. Figure 2 shows the closeness of registration between the skull cropped binary CT masks for the cohort. The method was used to assess olfactory bulb/cerebellum NAV ratios in the cohort by masking those regions on the AMBMC atlas. Figure 3 shows the comparative dynamic uptake ratios between the wild type mouse and the APP/PS1 group. Conclusions: A method has been developed that uses freely available software to co-register a mouse brain atlas to a cohort of micro PET-CT images, enabling uptake assessment of cerebral VOIs with minimal computational demand. References: 1Janke AL, Ullmann JF. (2015) Robust methods to create ex vivo minimum deformation atlases for brain mapping. Methods. 2015 Feb;73:18-26. doi: 10.1016/j.ymeth.2015.01.005 2M. Jenkinson, C.F. Beckmann, T.E. Behrens, M.W. Woolrich, S.M. Smith. FSL. NeuroImage, 62:782-90, 2012 Figure 1: (Top row) A skull-cropped CT image in the Sagittal and Transaxial planes with the skull cavity mask shown in yellow. (Bottom row) The same CT overlaid with the co-registered AMBMC template; Olfactory bulb and Cerebellum VOIs shown in green and blue respectively. Figure 2: Sagittal and Transaxial views of the co-registered binary skull-cropped CT masks showing the voxel-wise registration accuracy from 0 to 100%. Figure 3: The Olfactory bulb/Cerebellum VOI uptake ratios for the wild type control mouse and the averaged Alzheimer’s Amyloidosis APP/PS1 transgenic mice. ER -