Multimodal Imaging and Hybrid Scanners

10.1155/2007/45353International Journal of Biomedical Imaging20074535

Statistical Evaluations of the Reproducibility and Reliability of 3-Tesla High Resolution Magnetization Transfer Brain Images: A Pilot Study on Healthy Subjects

Magnetization transfer imaging (MT) may have considerable promise for early detection and monitoring of subtle brain changes before they are apparent on conventional magnetic resonance images. At 3 Tesla (T), MT affords higher resolution and increased tissue contrast associated with macromolecules. The reliability and reproducibility of a new high-resolution MT strategy were assessed in brain images acquired from 9 healthy subjects. Repeated measures were taken for 12 brain regions of interest (ROIs): genu, splenium, and the left and right hemispheres of the hippocampus, caudate, putamen, thalamus, and cerebral white matter. Spearman's correlation coefficient, coefficient of variation, and intraclass correlation coefficient (ICC) were computed. Multivariate mixed-effects regression models were used to fit the mean ROI values and to test the significance of the effects due to region, subject, observer, time, and manual repetition. A sensitivity analysis of various model specifications and the corresponding ICCs was conducted. Our statistical methods may be generalized to many similar evaluative studies of the reliability and reproducibility of various imaging modalities

Calcified plaque modification alters local drug delivery in the treatment of peripheral atherosclerosis

Background: Calcific atherosclerosis is a major challenge to intraluminal drug delivery in peripheral artery disease (PAD). Objectives: We evaluated the effects of orbital atherectomy on intraluminal paclitaxel delivery to human peripheral arteries with substantial calcified plaque. Methods: Diagnostic angiography and 3-D rotational imaging of five fresh human lower limbs revealed calcification in all main arteries. The proximal or distal segment of each artery was treated using an orbital atherectomy system (OAS) under simulated blood flow and fluoroscopy. Explanted arterial segments underwent either histomorphometric assessment of effect or tracking of [superscript 14]C-labeled or fluorescent–labeled paclitaxel. Radiolabeled drug quantified bulk delivery and fluorescent label established penetration of drug over finer spatial domain in serial microscopic sections. Results: were interpreted using a mathematical model of binding-diffusion mediated arterial drug distribution. Results Lesion composition affected paclitaxel absorption and distribution in cadaveric human peripheral arteries. Pretreatment imaging calcium scores in control femoropopliteal arterial segments correlated with a log-linear decline in the bulk absorption rate-constant of [superscript 14]C-labeled, declining 5.5-fold per calcified quadrant (p = 0.05, n = 7). Compared to controls, OAS-treated femoropopliteal segments exhibited 180 μm thinner intima (p < 0.001), 45% less plaque calcification, and 2 log orders higher paclitaxel bulk absorption rate-constants. Correspondingly, fluorescent paclitaxel penetrated deeper in OAS-treated femoropopliteal segments compared to controls, due to a 70% increase in diffusivity (p < 0.001). Conclusions These data illustrate that calcified plaque limited intravascular drug delivery, and controlled OAS treatment of calcific plaques resulted in greater drug permeability and improved adjunct drug delivery to diseased arteries.Peripheral artery disease Keywords: Drug coated balloons, Drug eluting stents, Atherectomy, Orbital atherectomy, calcified plaque, PaclitaxelNational Institute of Mental Health (U.S.) (Grant R01 GM-49039