The relationship between the acoustic intensity and the time duration of exposure, for a single pulse, necessary to produce a threshold lesion in the cat brain was studied. Focused ultrasound of 1, 3, and 4 MHz was employed with intensities ranging from 102 to 2×104 W/cm2 with the corresponding pulse durations from 7 to 2×10−4 sec, respectively. Three types of lesions were observed attending three regions. At the lower intensities and long time durations of exposure, the lesion is produced by a thermal mechanism. At the highest intensities and shortest time durations, cavitation is believed to be the mechanism responsible for the sometimes randomly appearing lesions. At intermediate dosages, the lesions are formed by a mechanical mechanism which is thus far not well understood. These results exhibit good agreement with that of other investigators on both the cat and the rat brain.

Real time cross-sectional echocardiographic studies of the left main coronary artery (LMCA) were performed in 15 normal patients, 15 patients with angiographically proven coronary artery disease but normal left main coronary segments, three patients with greater than 75% obstruction of the left main coronary artery, and one patient with a larger aneurysm of the left main coronary artery. In normal subjects the LMCA evaginates from in inferolateral wall of the aorta. The artery appears as two dominant parallel linear echoes separated by a clear space representing the lumen of the vessel. The LMCA courses beneath the right ventricular outflow tract and can generally be followed to its expected point of bifurcation. Confirmation that this structure was in fact the LMCA was obtained by injection of cardiogreen dye directly into the LMCA in two cases and by visualization of dye in this structure following aortic flush in one case. In the three cases with obstructive lesions of the LMCA, there was an area of inward bending of the parallel vessel wall echoes resulting in varying degrees of narrowing of the arterial lumen. In the case with the aneurysmal dilatation of the LMCA, an echo-free circular bulge in the distal portion of the LMCA was recorded. This study demonstrates the fesibility of recording the left main coronary artery using the cross-sectional echocardiographic technique.

Cross-sectional echocardiograms of the mitral valve orifice were recorded in 37 patients with mitral stenosis. Twenty-seven had pure mitral stenosis, and 10 had associated mitral regurgitation. Mitral valve area in patients with pure mitral stenosis measured from cross-sectional echocardiography was highly correlated (r = 0.89) with that calculated with the Gorlin formula using the pressure gradient and Fick cardiac output. With mitral regurgitation, mitral valve area by cross-sectional echocardiography correlated well (r = 0.90) with that calculated from the pressure gradient and cineangiographic stroke output. In two cases, direct pathologic measurements of mitral valve area agreed exactly with the cross-sectional echocardiographic measurement. Correlation between the mitral E-F slope and mitral valve area by cross-sectional echocardiography (r = 0.56) and catheterization (r = 0.49) was less reliable. Cross-sectional echocardiographic measurement of the mitral valve area correlates well with catheterization in patients with pure mitral stenosis and those with associated regurgitation.

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