Amyloid burden identifies neuropsychological phenotypes at increased risk of progression to Alzheimer's disease in mild cognitive impairment patients.

PURPOSE: The extent of amyloid burden associated with cognitive impairment in amnestic mild cognitive impairment is unknown. The primary aim of the study was to determine the extent to which amyloid burden is associated to the cognitive impairment. The secondary objective was to test the relationship between amyloid accumulation and memory or cognitive impairment. MATERIALS AND METHODS: In this prospective study 66 participants with amnestic mild cognitive impairment underwent clinical, neuropsychological and PET amyloid imaging tests. Composite scores assessing memory and non-memory domains were used to identify two clinical classes of neuropsychological phenotypes expressing different degree of cognitive impairment. Detection of amyloid status and definition of optimal amyloid ± cutoff for discrimination relied on unsupervised k-means clustering method. RESULTS: Threshold for identifying low and high amyloid retention groups was of SUVr = 1.3. Aß + participants showed poorer global cognitive and episodic memory performance than subjects with low amyloid deposition. Aß positivity significantly identified individuals with episodic memory impairment with a sensitivity and specificity of 80 and 79%, (χ2 = 21.48; P < 0.00001). Positive and negative predictive values were 82 and 76%, respectively. Amyloid deposition increased linearly as function of memory impairment with a rate of 0.13/ point of composite memory score (R = -44, P = 0.0003). CONCLUSION: The amyloid burden of SUVr = 1.3 allows early identification of subjects with episodic memory impairment which might predict progression from MCI to Alzheimer's disease. TRIAL REGISTRATION: EudraCT 2015-001184-39.

Assembly of gold nanoparticles on functionalized Si(100) surfaces through pseudorotaxane formation.

The assembly of gold nanoparticles (AuNPs) on a hydrogenated Si(100) surface, mediated by a series of hierarchical and reversible complexation processes, is reported. The proposed multi-step sequence involves a redox-active ditopic guest and suitable calix[n]arene-based hosts, used as functional organic monolayers of the two inorganic components. Surface reactions and controlled release of AuNPs have been monitored by application of XPS, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM) and electrochemistry.

Weighted registration of 123I-FP-CIT SPECT images improves accuracy of binding potential estimates in pathologically low striatal uptake.

To test whether the use of a striatum weighted image may improve registration accuracy and diagnostic outcome in patients with parkinsonian syndromes (PS), weighted images were generated by increasing signal intensity of striatal voxels and used as intermediate dataset for co-registering the brain image onto template. Experimental validation was performed using an anthropomorphic striatal phantom. (123)I-FP-CIT SPECT binding ratios were manually determined in 67 PS subjects and compared to those obtained using unsupervised standard (UWR) and weighted registered (WR) approach. Normalized cost function was used to evaluate the accuracy of phantom and subjects registered images to the template. Reproducibility between unsupervised and manual ratios was assessed by using intra-class correlation coefficient (ICC) and Bland and Altman analysis. Correlation coefficient was used to assess the dependence of semi-quantitative ratios on clinical findings. Weighted method improves accuracy of brain registration onto template as determined by cost function in phantom (0.86 ± 0.06 vs. 0.98 ± 0.02; Student's t-test, P = 0.04) and in subject scans (0.69 ± 0.06 vs. 0.53 ± 0.06; Student's t-test, P < 0.0001). Agreement between manual and unsupervised derived binding ratios as measured by ICC was significantly higher on WR as compared to UWR images (0.91 vs. 0.76). Motor UPDRS score was significantly correlated with manual and unsupervised derived binding potential. In phantom, as well as in subjects studies, correlations were more significant using the WR method (BPm: R(2) = 0.36, P = 0.0001; BPwr: R(2) = 0.368, P = 0.0001; BPuwr: R(2) = 0.300, P = 0.0008). Weighted registration improves accuracy of binding potential estimates and may be a promising approach to enhance the diagnostic outcome of SPECT imaging, correlation with disease severity, and for monitoring disease progression in Parkinsonian syndromes.