Performance characteristics of amyloid PET with florbetapir F 18 in patients with alzheimer's disease and cognitively normal subjects.

UNLABELLED: The objectives of this study were to examine the effective dose range and the test-retest reliability of florbetapir F 18 using, first, visual assessment by independent raters masked to clinical information and, second, semiautomated quantitative measures of cortical target area to cerebellum standardized uptake value ratios (SUVr) as primary outcome measures. Visual ratings of PET image quality and tracer retention or ß-amyloid (Aß) binding expressed as SUVrs were compared after intravenous administration of either 111 MBq (3 mCi) or 370 MBq (10 mCi) of florbetapir F 18 in patients with Alzheimer's disease (AD) (n = 9) and younger healthy controls (YHCs) (n = 11). In a separate set of subjects (AD, n = 10; YHCs, n = 10), test-retest reliability was evaluated by comparing intrasubject visual read ratings and SUVrs for 2 PET images acquired within 4 wk of each other. RESULTS: There were no meaningful differences between the 111-MBq (3-mCi) and 370-MBq (10-mCi) dose in the visual rating or SUVr. The difference in the visual quality across 111 and 370 MBq showed a trend toward lower image quality, but no statistical significance was achieved (t test; t(1) = -1.617, P = 0.12) in this relatively small sample of subjects. At both dose levels, visual ratings of amyloid burden identified 100% of AD subjects as Aß-positive and 100% of YHCs as Aß-negative. Mean intrasubject test-retest variability for cortical average SUVrs with the cerebellum as a reference over the 50- to 70-min period was 2.4% ± 1.41% for AD subjects and 1.5% ± 0.84% for controls. The overall SUVr test-retest correlation coefficient was 0.99. The overall κ-statistic for test-retest agreement for Aß classification of the masked reads was 0.89 (95% confidence interval, 0.69-1.0). CONCLUSION: Florbetapir F 18 appears to have a wide effective dose range and a high test-retest reliability for both quantitative (SUVr) values and visual assessment of the ligand. These imaging performance properties provide important technical information on the use of florbetapir F 18 and PET to detect cerebral amyloid aggregates.

Factors affecting visual outcomes after small-incision phacoemulsification in diabetic patients.

PURPOSE: To examine the factors affecting visual outcome after phacoemulsification and evaluate the use of preoperative visual potential in assessing the visual prognosis in diabetic patients. SETTING: Department of Ophthalmology, University of Texas Medical Branch, Galveston, Texas, USA. METHODS: In a retrospective chart review of 1345 consecutive patients who had uneventful small-incision phacoemulsification, operated eyes from 106 diabetic and 55 nondiabetic control patients were selected. Data on demographics, level of retinopathy, perioperative glycosylated hemoglobin (HbA(Ic)), surgical duration, preoperative best corrected visual acuity (BCVA), and visual potential were collected. RESULTS: The age, sex, preoperative BCVA, and visual potential in the diabetic and control eyes were comparable. Throughout the postoperative period, BCVA was worse of the diabetic group. At 1 year, BCVA was 20/40 in 82.1% of the diabetic group and 94.7% of the control group (P =.01). The most important factors affecting postoperative BCVA included coexisting diabetes and preoperative level of retinopathy. No correlation was found between perioperative and postoperative BCVA. Diabetic patients were less likely than control patients to achieve a BCVA better than or equal to the preoperative visual potential at 4 years (hazard ratio 0.6; 95% confidence interval, 0.4-0.9; P =.011). Patients with nonproliferative diabetic retinopathy were nearly 5 times less likely (P =.023) and patients with proliferative diabetic retinopathy 30 times less likely (P <.0001) to achieve a postoperative BCVA of 20/40 than diabetic patients without retinopathy. CONCLUSIONS: Although uneventful small-incision phacoemulsification improved visual acuity in diabetic patients, this group had an overall worse visual outcome than nondiabetic patients. The most important predictors of visual outcome were coexisting diabetes and the extent of preoperative retinopathy. Methods used to assess preoperative visual potential provided a reasonable estimate of postoperative BCVA in diabetic patients. Given the inverse association between the level of retinopathy and visual outcome, it may be better to perform cataract extraction in diabetic patients during earlier stages of retinopathy.