The PCr recovery time constant is prolonged in patients with symptomatic PAD compared with normal subjects. The method is reproducible and may be useful in the identification of disease. Further study of this parameter's ability to track response to therapy as well as its prognostic capability is warranted.

Purpose:To develop a contrast-enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD). Materials and Methods:A total of 11 patients (age ϭ 61 Ϯ 11 years) with mild to moderate symptomatic PAD (anklebrachial index [ABI] ϭ 0.75 Ϯ 0.08) and 22 normals were studied using an MR-compatible ergometer. PAD and normal max (Nl max ; N ϭ 11) exercised to exhaustion. Nl low (N ϭ 11) exercised to the same workload achieved by PAD. At peak exercise, 0.1 mm/kg of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was infused at 3-4 cm 3 / second followed by a saline flush at the same rate. A dualcontrast gradient echo (GRE) sequence enabled simultaneous acquisition of muscle perfusion and arterial input function (AIF). The perfusion index (PI) was defined as the slope of the time-intensity curve (TIC) in muscle divided by the arterial TIC slope. Results Conclusion:Peak-exercise measurement of lower limb perfusion with dual-contrast, first-pass MR distinguishes PAD from normals. This method may be useful in the study of novel therapies for PAD.

A high resolution, noninvasive approach to quantify atherosclerotic plaque in the peripheral vasculature could have significant clinical and research utility. Seventeen patients with peripheral arterial disease (PAD) were studied in a 1.5T CMR scanner. Atherosclerotic plaque volume in the superficial femoral artery was measured and interobserver, intraobserver, and test-retest variability determined. Nineteen vessels were studied with mean acquisition time of 13.1 minutes per vessel. Mean plaque volume was 7.27 ± 3.73 cm 3 . Intra-observer intraclass correlation was R = 0.997, inter-observer was R = 0.987, and test-retest reproducibility was R = 0.996. Thus, high resolution measurement of plaque volume in PAD is reliable and reproducible.

BACKGROUND and OBJECTIVES-The study was designed to determine the prevalence of extracardiac findings discovered during multidetector computed tomography (MDCT) examinations prior to atrial fibrillation ablation. MDCT has become a valuable tool in detailing left atrial anatomy prior to catheter ablation. The incidence of extracardiac findings has been reported for electron beam CT calcium scoring (EBCT) and coronary MDCT, but no data exists for the prevalence of extracardiac findings discovered prior to atrial fibrillation ablation with MDCT.

Because of its safety, accuracy, ease of interpretation, and increasing availability, cardiac magnetic resonance-based assessment of myocardial viability has quickly transitioned from bench to bedside. Routine clinical implementation has prompted improved diagnostic capabilities and easier image interpretation. As a research tool, cardiac magnetic resonance continues to provide valuable insights into the fundamental nature of viability.