First-pass contrast-enhanced myocardial perfusion MRI using a maximum up-slope parametric map.

Magnetic resonance first-pass perfusion imaging offers a noninvasive method for the rapid, accurate, and reproducible assessment of cardiac function without ionizing radiation. Quantitative or semiquantitative analysis of changes in signal intensity (SI) over the whole image sequence yields a more efficient analysis than direct visual inspection. In this paper, a method to generate maximum up-slope myocardial perfusion maps is presented. The maximum up-slope is defined by comparison of the SI variations using frame-to-frame analysis. A map of first-pass transit of the contrast agent is constructed pixel by pixel using a linear curve fitting model. The proposed method was evaluated using data from eight subjects. The data from the parametric maps agreed well with those obtained from traditional, manually derived region-of-interest methods as shown through ANOVA. The straightforward implementation and increase in image analysis efficiency resulting from this method suggests that it may be useful for clinical practice.

Evidence that collagen and tendon have monolayer water coverage in the native state.

This paper investigates an alternative explanation for widely reported paradoxical intracellular water properties. The most frequent biological explanation assumes water structure extending multiple layers from surfaces of compactly folded macromolecules to explain large amounts of perturbed water. Long range water structuring, however, contradicts molecular models widely accepted by the scientific majority. This study questions whether the paradoxical cell water could result from larger than expected amounts of first layer interfacial water on internal protein surfaces rather than structured multilayers. Native mammalian tendon is selected for the study because (1) the organ consists of highly compact structures of a single macromolecular protein--collagen, (2) molecular structure and geometry of collagen is well characterized by X-ray diffraction, (3) molecular structure extends to the macroscopic tendon level and (4) perturbed water behavior similar to cellular water is reported on tendon. Native tendon holds 1.6 g water/g dry mass. The 62% native water content simulates the water content of many cell types. MicroCT studies of tendon dilatometry as a function of hydration are measured and correlated to X-ray diffraction measurements of interaxial separation. Correlations show that native tendon has sufficient water for only a single monolayer of interfacial water. Thus the paradoxical properties of water in native tendon are first-layer interfacial water properties. Similar water behavior on globular proteins suggests that paradoxical cell water behavior could be caused by larger than expected amounts of first layer interfacial water on internal and external macromolecular surfaces of cell components.