activated a predominantly left hemispheric network during a semantic memory task while the aMCI group activated similar areas but to a lesser extent. This suggests that semantic memory is affected in addition to episodic memory in aMCI. The areas of diminished activation in the aMCI group did not correspond to the region of reduced gray matter density, indicating that the decreased activa- tion in the aMCI group was not due to effects of local atrophy in these subjects. Study supported by: Alzheimers Association NIRG-05-13067, NIH AG19142, AG06786, AG16574, AG11378, Robert H. and Clarice Smith and Abigail Van Buren Alzheimers Disease Research Program. P-046 [I-123] IMPY IMAGING IN ALZHEIMER’S DISEASE AND HEALTHY CONTROLS Kenneth Marek 1 , Danna Jennings 1 , Gilles Tamagnan 1 , Andre Koren 1 , Daniel Skovronsky 2 , John Seibyl 1 , 1 Institute for Neurodegenerative Disorders, New Haven, CT, USA; 2 AVID Radiopharmaceuticals, Philadelphia, PA, USA. Contact e-mail: kmarek@indd.org Background: -Amyloid plaque accumulation likely plays a critical role in AD etiology, and potentially in AD therapy. Imaging tracers targeting -amyloid would provide improved diagnostic accuracy and enable monitoring of amyloid reducing therapies for AD. IMPY is a modified thioflavin derivative with good binding affinity to preformed synthetic A 1-40 aggregates, excellent brain uptake, and selective plaque labeling in AD transgenic mouse models and in postmortem AD brain sections. Objective: To evaluate [I-123] IMPY (6-iodo-2-(4’-dimethyl- amino-)phenyl-imidazo[1,2-]pyridine) as an objective and quantifiable biomarker of -amyloid deposition in Alzheimer’s disease (AD) subjects and healthy controls (HC). Methods: In this ongoing study AD patients and HC undergo serial SPECT imaging after either a single bolus injection or a bolus injection followed by multiple mini-bolus injections of [I-123] IMPY. Subjects were evaluated prior to imaging with MMSE, ADAS-Cog. After the single bolus injection 15 serial, dynamic SPECT acquisitions were acquired over 2 hours. During the bolus plus mini-bolus injections scans were acquired for 90 minutes. All images within each reconstructed data set were aligned with SPM. Results were based on a standard- ized cortical volume of interest protocol. Venous blood was obtained to assess free plasma IMPY and metabolites. Results: 15 subjects; 8 AD patients (mean age 80, gender -6F,2M, mean MMSE 23) and 7 HC (mean age 69, gender -2F 5M, mean MMSE 29) have undergone [I-123] IMPY imaging. Following bolus injection cortical time activity data shows rapid uptake and washout. Analysis shows a T1/2 washout of [I-123] IMPY of 21.5 minutes (sd 5.3) for HS and 39.3 minutes (sd 19) for AD (p=.052). Preliminary analysis of equilibrium distribution volume showed mean cortical to cerebellar ratios of 1.25 in AD subjects compared to 1.06 in HS. Conclusion: This pilot [I-123] IMPY study demonstrates a 25%-100% signal difference between well-characterized AD patients and older HC depending on the imaging outcome. These data suggest the feasibility of distinguishing AD and HC using quantitative [I-123] IMPY imaging outcomes. However, additional studies are required to more fully validate [I-123] IMPY as a potential tool for AD onset and progression. P-047 CEREBRAL PERFUSION IN ALZHEIMER’S DISEASE AND FRONTOTEMPORAL DEMENTIA USING DYNAMIC SUSCEPTIBILITY CONTRAST MRI Rachel D. McKinsey 1 , Zhifei Wen 1 , Alan B. McMillan 1 , Mary E. Meyerand 1 , Michele E. Fitzgerald 2 , Cindy M. Carlsson 2 , Gemma Gliori 2 , George C. Newman 3 , Sterling C. Johnson 2 , Sean B. Fain 1 , 1 University of Wisconsin Madison, Madison, WI, USA; 2 GRECC, Veterans Administration Hospital, Madison, WI, USA; 3 Department of Neurology, University of Wisconsin School of Madison, Madison, WI, USA. Contact e-mail: mckinsey@wisc.edu Background: Decrease in cerebral perfusion has been observed with perfusion MRI in Alzheimer disease(AD) and frontotemporal dementia(FTD). Dynamic susceptibility-weighted contrast(DSC) perfusion with intravenous gadolinium con- trast injection has received only limited attention in the investigation of perfusion changes in AD and FTD. It may be clinically advantageous to develop DSC further because the technique can be performed rapidly, provides cerebral blood flow(CBF), cerebral blood volume(CBV), and mean transit time(MTT) maps, and is less sensitive to bias due to normal age-dependent reductions in blood flow. Objective(s): To determine the feasibility of DSC perfusion MRI for the detection of quantitative CBV and CBF changes in subjects with AD and FTD. Materials and Methods: Seven subjects with AD(mean age 76.9 years), six subjects with FTD(mean age 62.7 years), and six normal control(NC) subjects(mean age 71.5 years) were scanned on a GE Signa 1.5T MR. The imaging protocol included one relatively rapid bolus injection (65mol/kg at 3mL/s) followed by a slow infusion (35 mol/kg, diluted to 90mL at 1mL/s). The acquisition parameters were opti- mized for depicting MTT measurements while a contrast infusion technique was optimized for measuring CBV. CBF maps were calculated using the central volume theorem, CBF=CBV/MTT. These perfusion maps were normalized to standard MNI space and smoothed with a 10mm FWHM Gaussian kernel using SPM5[http://www.fil.ion.ucl.ac.uk/spm/]. Results: ADvsNC. Decreases in perfu- sion were identified in subjects with AD bilaterally in the superior frontal cortex, the posterior cingulated, and in the para hippocampal gyrus(Figure 1). The CBV map shows decreased blood volume in the right posterior temporal lobe. FTD- vsCN. Hypoperfusion was observed bilaterally in the inferior frontal gyrus and in the left inferior frontal gyrus. A unilateral region in the left posterior temporal lobe showed corresponding reduction in CBV in subjects with FTD(Figure 2). Con- clusion: The DSC MRI data show correspondence with known regions of hypo- perfusion measured with ASL MRI methods. DSC MRI appears to be a viable means for measuring relative perfusion changes in AD and FTD and potentially for identifying those at risk for developing more progressed disease. Interestingly, blood volume changes were not found to be significant in the subjects studied thus far. P-048 REGIONALLY-SPECIFIC DIFFUSION TENSOR IMAGING MEASURES IN ALZHEIMER’S DISEASE AND CONTROLS Michelle Mielke 1 , Michael George 1 , Nicholas Kozauer 1 , Jaimie Toroney 1 , Karen Bandeen-Roche 2 , Gary Chan 2 , Peter vanZijl 3 , James Pekar 3 , Susumu Mori 3 , Constantine Lyketsos 1 , Marilyn Albert 1 , 1 Johns Hopkins University School of Medicine, Baltimore, MD, USA; 2 Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; 3 FIM Kirby Imaging Center, Johns Hopkins University, Baltimore, MD, USA. Contact e-mail: mmielke1@jhmi.edu Background: Diffusion tensor imaging (DTI) is an imaging method that evaluates the integrity of white matter fiber tracts within the brain. Recent cross-sectional studies have reported differences in the posterior cingulate, corpus callosum, and cingulum bundle among normal controls, MCI cases and patients with AD. Cross-sectional analyses are important for determining whether DTI measures can distinguish among groups of subjects based on cognitive status, and longitudinal data can determine whether changes in clinical status are reflected in significant changes in DTI. Objective(s): To examine both cross-sectional and longitudinal measures of DTI in cognitively normal controls and AD patients in order to determine its feasibility as a surrogate marker for AD. Methods: Seventy-five participants (25 normal controls, 25 amnestic MCI, and 25 mild AD patients) have been enrolled in a longitudinal study in which subjects are evaluated at 4 time points (baseline, 3, 6, and 12 months) with both imaging and clinical evaluations. In the present report, DTI data from the baseline and 3-month assessments of 10 normal controls and 10 S112 Posters: P-046