Time Course Of Volume Research Articles

Left ventricle: fully automated segmentation based on spatiotemporal continuity and myocardium information in cine cardiac magnetic resonance imaging (LV-FAST).

CMR quantification of LV chamber volumes typically and manually defines the basal-most LV, which adds processing time and user-dependence. This study developed an LV segmentation method that is fully automated based on the spatiotemporal continuity of the LV (LV-FAST). An iteratively decreasing threshold region growing approach was used first from the midventricle to the apex, until the LV area and shape discontinued, and then from midventricle to the base, until less than 50% of the myocardium circumference was observable. Region growth was constrained by LV spatiotemporal continuity to improve robustness of apical and basal segmentations. The LV-FAST method was compared with manual tracing on cardiac cine MRI data of 45 consecutive patients. Of the 45 patients, LV-FAST and manual selection identified the same apical slices at both ED and ES and the same basal slices at both ED and ES in 38, 38, 38, and 41 cases, respectively, and their measurements agreed within −1.6 ± 8.7 mL, −1.4 ± 7.8 mL, and 1.0 ± 5.8% for EDV, ESV, and EF, respectively. LV-FAST allowed LV volume-time course quantitatively measured within 3 seconds on a standard desktop computer, which is fast and accurate for processing the cine volumetric cardiac MRI data, and enables LV filling course quantification over the cardiac cycle.

Rheoplethysmographic studies of digital venous tone and venous activity.

Abstract It has been shown that partial obstruction to digital venous outflow resulted in slight increase in tone and constriction of the precapillary digital vessels and from slight to marked increase in postcapillary vascular tone and constriction. The digital veins were among the postcapillary vessels. The mechanism for the increase in venomotor tone as well as the tone of the other vessels remains unknown. Four types of volume-time course curves for the initial pulse cycles after inflation of the digital collecting cuff were described. These included the patterns for (1) the resting, relaxed state of the digital vessels, (2) the dilated state, (3) the constricted state (Types A and B), and (4) the obstruction to digital flow. These curves have significant rheoplethysmographic, physiologic, and pathologic connotations. Noradrenalin was found to constrict the postcapillary digital vessels, including the veins, but the veins were not constricted as much as the precapillary vessels for the doses used. The orienting reflex, psychogenic and neurogenic reflexes, and deep inspiration were found to produce constriction of the postcapillary vessels, including the digital veins, as well as the precapillary vessels. It was found rheoplethysmographically that the pre- and postcapillary vessels constrict and/or dilate discordantly or disproportionately in the same manner described for the afferent and efferent arterioles of the kidney. This phenomenon probably exists for other organs as well. The phenomenon is most likely concerned with the regulation of water and solute loss into, and absorption from, the intercellular spaces, and with interstitial fluid circulation and lymph flow in healthy and diseased states. The value of digital rheoplethysmography in the study of the peripheral circulation was further emphasized by these observations.

A study of the volume-time course of the pulse wave of the finger tip

The volume pulse waves of the index finger tip of normal man and subjects with selected diseases of the cardiovascular system were analyzed to study the time course of velocity and acceleration derived by successive differentiation of the pulse wave. These velocity and acceleration curves were described. The curve of the third derivative of the volume pulse wave was found to resemble remarkably the ballistocardiogram. Certain physiologic implications of these various curves were indicated.