Mitral Valve Flow and Myocardial Motion Assessed with Dual-Echo Dual-Velocity Cardiac MRI.

Purpose: To develop a dual-echo phase-contrast (DEPC) MRI approach with which each echo is acquired by using a different velocity sensitivity within one repetition time (TR) and demonstrate the feasibility of this approach to measure transmitral blood flow and myocardial tissue ( ) velocities.

Materials And Methods: The flow across tubes of known diameter was measured by using the proposed DEPC method and compared with flowmeter measurements and theoretic predictions. Then, with both the DEPC MRI sequence and the conventional single-echo phase-contrast (SEPC) MRI sequence, , and were measured in six healthy volunteers (mean age, 49 years ± 13 [standard deviation]) and eight patients (mean age, 54 years ± 15) being evaluated for cardiac disease.

Tissue characterization of uterine fibroids with an intravoxel incoherent motion model: The need for T correction.

Background: Diminished signal intensity of uterine fibroids in T -weighted images is routinely used as a qualitative marker of fibroid hypoperfusion. However, quantitative classification of fibroid perfusion with intravoxel incoherent motion (IVIM) model-based metrics is not yet clinically accepted.

Purpose: To investigate the influence of T correction on the estimation of IVIM model parameters for characterizing uterine fibroid tissue.

Noninvasive, in vivo determination of uterine fibroid thermal conductivity in MRI-guided high intensity focused ultrasound therapy.

Purpose: To estimate the local thermal conductivity of uterine fibroid in vivo at a high temperature range (60-80°C) typically encountered in magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU) surgery. The thermal conductivity of uterine fibroids in vivo is unknown and knowledge about tissue thermal conductivity may aid in effective delivery of thermal energy for ablation.

Materials And Methods: All subjects (nine women) provided written informed consent to participate in this Institutional Review Board-approved study.

Implications of charge ordering in high Tc cuprate superconductors in far-infrared spectroscopy.

We addressed the issue of the absence of far-infrared signatures pertaining to charge ordering in the published far-infrared reflectivity data of La2-xSrxCuO4 single crystals while other experimental probes reveal that charge ordering is a hallmark of superconducting cuprates. Through direct comparison of the far-infrared data reported by various groups side by side and also with the Raman scattering data, we found that the inconsistencies stem from the failure in capturing delicate spectral features embedded in the close-to-perfect ab-plane far-infrared reflectivity of La2-xSrxCuO4 single crystals by misidentifying the reflectivity as the Drude-like metallic reflectivity. The analysis of the close-to-true reflectivity data reveals that only a small fraction (<3%) of the total doping-induced charge carriers (electrons) are itinerant on the electron lattice made up with the rest of the electrons (>97%) at all doping levels up to 16%.

Volumetric MRI-guided high-intensity focused ultrasound for noninvasive, in vivo determination of tissue thermal conductivity: initial experience in a pig model.

Purpose: To estimate the local thermal conductivity of porcine thigh muscle at temperatures required for magnetic resonance imaging (MRI)-guided high-intensity focused ultrasound (MRgHIFU) surgery (60-90°C).

Materials And Methods: Using MRgHIFU, we performed 40 volumetric ablations in the thigh muscles of four pigs. Thirty-five of the sonications were successful.

A basic step toward understanding skin surface temperature distributions caused by internal heat sources.

This study uses numerical solutions of a bio-heat transfer equation to investigate the relationship between skin surface temperature distributions and internal heat sources under various physiological and environmental conditions. It is found that although a surface temperature distribution depends on all heat source parameters, the properly normalized distribution is primarily affected only by the depth of the heat source. This study provides a physical basis for determining the depth and type of an internal heat source from a thermogram acquired in various environmental conditions and an understanding of the basic relationship between skin surface temperature distributions and internal heat sources.