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OBJECTIVE--To determine whether middle-aged and older individuals with impaired fasting glucose (IFG), but no clinical evidence of cardiovascular disease, exhibit abnormal changes in proximal thoracic aortic stiffness or left ventricular (LV) mass when compared with healthy counterparts. RESEARCH DESIGN AND METHODS--From the Multi-Ethnic Study of Atherosclerosis, 2,240 subjects with normal fasting glucose (NFG), 845 with IFG, and 414 with diabetes, all aged 45 to 85 years and without preexisting coronary artery disease, underwent MRI determinations of total arterial and proximal thoracic aortic stiffness and LV mass. The presence or absence of other factors known to influence arterial stiffness was assessed. RESULTS--After adjustment for clinical factors known to modify arterial stiffness, proximal thoracic aortic stiffness was not increased in those with IFG compared with those with NFG (1.90 ± 0.05 versus 1.91 ± 0.04 [10.sup.-3] [mmHg.sup.-1], respectively, P = 0.83). After accounting for clinical factors known to influence LV mass, LV mass was increased in those with diabetes relative to those with NFG (150.6 ± 1.4 versus 145.8 ± 0.81 g, P < 0.0009) but not in those with IFG in comparison with NFG (145.2 ± 1.03 versus 145.8 ± 0.81 g, P = 0.56). CONCLUSIONS--Middle-aged and older individuals with the pre-diabetes state of IFG do not exhibit abnormal proximal thoracic distensibility or LV hypertrophy relative to individuals with NFG. For this reason, an opportunity may exist in those with IFG to prevent LV hypertrophy and abnormal aortic stiffness that is observed in middle-aged and older individuals with diabetes., Individuals with diabetes exhibit increased arterial stiffness that is associated with future cardiovascular morbidity and mortality, peripheral arterial disease, impaired myocardial function, left ventricular (LV) hypertrophy, and congestive heart failure [...]

Atheroma vulnerability to rupture is increased in the presence of a large lipid core. Factors associated with a lipid core in the general population have not been studied.

Dynamic load balancing is a popular recent technique that protects ISP networks from sudden congestion caused by load spikes or link failures. Dynamic load balancing protocols, however, require schemes for splitting traffic across multiple paths at a fine granularity. Current splitting schemes present a tussle between slicing granularity and packet reordering. Splitting traffic at the granularity of packets quickly and accurately assigns the desired traffic share to each path, but can reorder packets within a TCP flow, confusing TCP congestion control. Splitting traffic at the granularity of a flow avoids packet reordering but may overshoot the desired shares by up to 60% in dynamic environments, resulting in low end-to-end network goodputContrary to popular belief, we show that one can systematically split a single flow across multiple paths without causing packet reordering. We propose FLARE, a new traffic splitting algorithm that operates on bursts of packets, carefully chosen to avoid reordering. Using a combination of analysis and trace-driven simulations, we show that FLARE attains accuracy and responsiveness comparable to packet switching without reordering packets. FLARE is simple and can be implemented with a few KB of router state

This review is focused on two relatively new developments in magnetic resonance imaging (MRI) and their application to breast lesion characterization: diffusion and perfusion MRI. Diffusion MRI measures the mobility of the water protons and thus provides a window to tissue microstructure. Perfusion MRI measures the rate at which blood is delivered to tissue and thus provides information about microvasculature. Because both tissue structure and vasculature are likely to change in disease states, measurement of diffusion and perfusion may have direct physiologic relevance. This review covers topics related to the imaging sequences, image analysis, and clinical studies for diffusion and perfusion breast MRI. Preliminary studies show that the apparent diffusion coefficient (ADC) is a marker of cell density and can distinguish malignant from benign lesions. Perfusion MR also shows promise for breast tumor characterization: malignant tumors have consistently higher relative tissue blood volumes (rTBV) than normal and benign tumors. Additional research is required with large patient cohorts to establish these two techniques on a clinical footing.

High-resolution magnetic resonance imaging (MRI) at 1.5 T preferentially enhances the perilymph over endolymph after administration of contrast with gadodiamide, which allows for differentiation of the membranous labyrinth. Furthermore, this imaging allows for the detection of endolymphatic hydrops.

The objective of this study was to determine whether linear discriminant analysis of different independent features of MR images of breast lesions can increase the sensitivity and specificity of this technique. For MR images of 23 benign and 20 malignant breast lesions, three independent classes of features, including characteristics of Gd‐DTPA‐uptake curve, boundary, and texture were evaluated. The three classes included five, four and eight features each, respectively. Discriminant analysis was applied both within and across the three classes, to find the best combination of features yielding the highest classification accuracy. The highest specificity and sensitivity of the different classes considered independently were as follows: Gd‐up‐take curves, 83% and 70%; boundary features, 86% and 70%; and texture, 70% and 75%, respectively. A combination of one feature each from the first two classes and age yielded a specificity of 79% and sensitivity of 90%, whereas highest figures of 93% and 95%, respectively, were obtained when a total of 10 features were combined across different classes. Statistical analysis of different independent classes of features in MR images of breast lesions can improve the classification accuracy of this technique significantly.

Breast implant rupture is an important complication of augmented and reconstructed breasts. Although several techniques such as mammography, xeromammography, ultrasound, thermography, and computed tomographic (CT) scanning have been proven to be useful to detect implant rupture, they have several disadvantages and lack specificity. In the current study, we have established magnetic resonance imaging (MRI) as a definitive, reliable, and reproducible technique to diagnose both intracapsular and extracapsular ruptures. The study was conducted in 100 symptomatic patients. Our imaging parameters were able to identify ruptures in implants with silicone shells. All the ruptures showed the presence of wavy lines, free-floating silicone shell within the gel (“free-floating loose-thread sign” or “linguine sign”). We had a 3.75 percent incidence of false-positive and false-negative results. The sensitivity for detection of silicone implant rupture was 76 percent, with a specificity of 97 percent. In addition, we also were able to identify the artifacts that may interfere with the definitive diagnosis of implant rupture. (Plast. Reconstr. Surg.92: 681, 1993.)

Proton phase shift imaging methods with keyholing were developed to rapidly monitor temperature during MR‐guided radiofrequency (RF) interventional procedures on a .2‐T open configuration scanner. Temperature calibration was performed on thermally controlled gel phantom and ex vivo bovine liver samples. Keyholing methods were implemented for rapid imaging and tested both in simulation experiments and in the gel phantom. Phase drifts from extraneous sources were monitored and compensated for using reference phantoms. Sequence parameters TE, TR, and flip angle (FA) were optimized for maximum temperature sensitivity and minimum noise. Reduction of phase noise from coupling of the magnetic field to external perturbations using navigator‐echo‐based correction schemes were also investigated. The extraneous phase drifts from the magnet could be minimized by keeping the electromagnet on continuously. Navigator echo corrected keyholed FLASH sequences (TE = 30 msec, TR = 60 msec, FA = 40°, 64 × 128 matrix) were used to monitor the RF lesioning process in gel phantoms yielding images every 4 seconds with a temperature sensitivity of .015 ppm/°C. RF ablation in the bovine tissue was monitored using navigator‐echo‐corrected keyholed fast low angle shot (FLASH) sequences (TE = 30 msec, TR = 100 msec, FA = 40°, 128 × 256 matrix) with a temporal resolution of 13 seconds and a temperature sensitivity of .007 ppm/°C. The results indicate that monitoring of an RF ablation procedure by mapping temperature with sufficient temporal resolution is possible using phase images of FLASH sequences on a .2‐T open scanner.

To synthesize magnetic resonance images (MRI) in real-time using a minimal data set obtained with routine clinical protocols and stored in a picture archiving and communication system (PACS) database.

The purpose of this study was to test the feasibility of MR‐guided percutaneous ethanol ablation of liver tissue on a .2‐T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low‐angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol‐infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol‐induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR‐guided hepatic tumor ablation.

The origin of the crystal field and its variation with temperature in severalα-alums have been studied bynmrof27Al andeprof Cr3+at high hydrostatic pressures and low temperatures. The results lead to an explanation of the anomalous temperature variation of the axial crystal field at the trivalent ion site. The mechanism of the phase transition in ammonium alum is also explained. A correlation between the axial crystal field as determined bynmr(e2qQ/h) and that determined byepr(D) has been obtained.