Amyloid imaging in Alzheimer's disease: comparison of florbetapir and Pittsburgh compound-B positron emission tomography.

BACKGROUND: Amyloid imaging provides in vivo detection of the fibrillar amyloid-ß (Aß) plaques of Alzheimer's disease (AD). The positron emission tomography (PET) ligand, Pittsburgh Compound-B (PiB-C11), is the most well studied amyloid imaging agent, but the short half-life of carbon-11 limits its clinical viability. Florbetapir-F18 recently demonstrated in vivo correlation with postmortem Aß histopathology, but has not been directly compared with PiB-C11. METHODS: Fourteen cognitively normal adults and 12 AD patients underwent PiB-C11 and florbetapir-F18 PET scans within a 28-day period. RESULTS: Both ligands displayed highly significant group discrimination and correlation of regional uptake. CONCLUSION: These data support the hypothesis that florbetapir-F18 provides comparable information with PiB-C11.

Knee articular cartilage damage in osteoarthritis: analysis of MR image biomarker reproducibility in ACRIN-PA 4001 multicenter trial.

PURPOSE: To prospectively determine the reproducibility of quantitative magnetic resonance (MR) imaging biomarkers of the morphology and composition (spin lattice relaxation time in rotating frame [T1-ρ], T2) of knee cartilage in a multicenter multivendor trial involving patients with osteoarthritis (OA) and asymptomatic control subjects. MATERIALS AND METHODS: This study was HIPAA compliant and approved by the institutional review committees of the participating sites, with written informed consent obtained from all participants. Fifty subjects from five sites who were deemed to have normal knee joints (n = 18), mild OA (n = 16), or moderate OA (n = 16) on the basis of Kellgren-Lawrence scores were enrolled. Each participant underwent four sequential 3-T knee MR imaging examinations with use of the same imager and with 2-63 days (median, 18 days) separating the first and last examinations. Water-excited three-dimensional T1-weighted gradient-echo imaging, T1-ρ imaging, and T2 mapping of cartilage in the axial and coronal planes were performed. Biomarker reproducibility was determined by using intraclass correlation coefficients (ICCs) and root-mean-square coefficients of variation (RMS CVs, expressed as percentages). RESULTS: Morphometric biomarkers had high reproducibility, with ICCs of 0.989 or greater and RMS CVs lower than 4%. The largest differences between the healthy subjects and the patients with radiographically detected knee OA were those in T1-ρ values, but precision errors were relatively large. Reproducibility of T1-ρ values was higher in the thicker patellar cartilage (ICC range, 0.86-0.93; RMS CV range, 14%-18%) than in the femorotibial joints (ICC range, 0.20-0.84; RMS CV range, 7%-19%). Good to high reproducibility of T2 was observed, with ICCs ranging from 0.61 to 0.98 and RMS CVs ranging from 4% to 14%. CONCLUSION: MR imaging measurements of cartilage morphology, T2, and patellar T1-ρ demonstrated moderate to excellent reproducibility in a clinical trial network.

Blood Pressure Effects of Yoga, Alone or in Combination With Lifestyle Measures: Results of the Lifestyle Modification and Blood Pressure Study (LIMBS).

The authors conducted a study to assess the effects of yoga on blood pressure (BP). Patients were randomized to yoga (Blood Pressure Education Program [BPEP]), or a combined program (COMBO). Ambulatory BP was measured at baseline and at 12 and 24 weeks. Data are presented for all enrolled patients (n=137) and for completers only (n=90). Systolic BP (SBP) and diastolic BP (DBP) were significantly decreased within all groups at 12 and 24 weeks (P<.001) for enrolled patients and completers. SBP was significantly reduced in the yoga and COMBO groups as compared with the BPEP group at 12 weeks in all enrolled and completers. SBP differences were no longer significant at 24 weeks between groups in all enrolled patients; however, there was a greater reduction in SBP at 24 weeks in completers favoring BPEP over yoga. No differences in DBP between groups or in BP between the yoga and COMBO groups were present. The authors did not observe an additive benefit from combining yoga with BPEP measures. Reasons for this are unclear at this time. BP lowering with yoga, however, was similar to that achieved with lifestyle measures.

Comparison of qualitative and quantitative imaging characteristics of [11C]PiB and [18F]flutemetamol in normal control and Alzheimer's subjects.

INTRODUCTION: Neuritic amyloid plaques and neurofibrillary tangles, the hallmark pathologic lesions of Alzheimer's disease, are thought to develop before the symptoms of brain failure are clinically detectable. Imaging methods capable of detecting the presence of neuritic amyloid plaques should improve a clinician's ability to identify Alzheimer's disease during the earliest symptomatic phase and to identify at-risk individuals presymptomatically. Currently the best studied amyloid imaging ligand is [(11)C]Pittsburgh Compound B ([(11)C]PiB). However, the 20-minute half-life of this radiotracer limits its use. This study is designed to evaluate the performance characteristics of [(18)F]flutemetamol and to independently compare results to [(11)C]PiB in the same subjects. METHODS: Twenty-three subjects, 15 cognitively normal (NL) and 8 with a clinical diagnosis of Alzheimer's Dementia (AD), underwent [(11)C]PiB and [(18)F]flutemetamol PET scans within 28 days of study enrollment. We studied both normal and AD subjects to assess the uptake characteristics across a range of amyloid positivity. Blinded visual reads were conducted by five raters. Correlation analyses were performed between cortical SUVR for the two tracers and also between rater scores and SUVR for each tracer. Overall reader accuracy for classifying scans as amyloid positive or negative was determined for each tracer using SUVR classification as the standard. RESULTS: The linear correlation coefficient between global cortical SUVR for the two tracers was R(2) = 0.85, indicating that both tracers have similar retention characteristics. The two tracers were well correlated for rater-determined AD-like positivity (Cohen κ = 0.82). Averaged visual ratings and global cortical SUVR disagreed on their classification in 2/23 [(11)C]PiB scans and 4/23 [(18)F]flutemetamol scans. CONCLUSIONS: [(11)C]PiB and [(18)F]flutemetamol have similar retention characteristics across a range of amyloid negative to positive subjects. Both tracers performed similarly when a standardized visual read technique was used to classify scans as amyloid-positive or amyloid-negative and correlated well with SUVR classifications. However, care in visual interpretation of amyloid positive versus amyloid negative regions should be taken, particularly in the case of [(18)F]flutemetamol when considering cortical vs. white-matter retention.