Magnetic resonance (MR) imaging has proved to be a new alternative method for the noninvasive detection and quantification of blood flow in human vessels. By means of standard gradient echo sequences triggered with electrocardiography on a 1.5-T whole-body imaging system, the authors measured the flow-induced phase shift in the abdominal aorta of healthy volunteers. The instantaneous two-dimensional velocity profiles and the integrated flow rate were determined in intervals down to 21 msec throughout the cardiac cycle. The results were validated by means of comparative measurements with a multigated Doppler ultrasound instrument. The velocity values acquired with this instrument in one spatial dimension in the anteroposterior direction of the abdominal aorta agreed to a great extent with the temporal and spatial corresponding values recorded with MR imaging. The same high correlation between the two methods was found for the calculated instantaneous total blood flow.

Ultrasonic tissue characterization is a new area of investigation in the field of cardiac ultrasound. The amplitude and frequency of the ultrasound signal are normally altered as the signal penetrates through tissue. It is assumed that the amplitude distribution and frequency shift of diseased or edematous tissue are different than those of normal tissue. A statistical approach to the analysis of the unprocessed radiofrequency signal in the amplitude domain was used to study the effect of acute myocardial ischemia on the parameter mean amplitude/standard deviation of the amplitude (MSR). Ten dogs were anesthetized and underwent left lateral thoracotomy. Baseline mean MSR from the interventricular septum was 1.99 + 0.05, but increased by 30 min after coronary artery occlusion and started to plateau at 1 hr (mean 2.24 + 0.06). Reproducibility in noninfarcted myocardium (left ventricular inferoposterior wall) was good, with a mean MSR of 2.00 + 0.05 at baseline and 1.98 0.04 3 to 4 hr later. There was no difference in mean MSR when data were obtained through chest wall and when they were obtained directly from the surface of the heart. We conclude that statistical analysis in the amplitude domain of the unprocessed radiofrequency signal can detect acute myocardial ischemia within 30 min after coronary artery occlusion, provides reproducible measurements, and is unaffected by chest wall filtering. Circulation 72, No. 1, 193-199, 1985. DETECTION OF early acute myocardial ischemia in man is currently suboptimal. The electrocardiogram may not always reveal acute ischemia because it may demonstrate only nonspecific changes. The technetium pyrophosphate scintigram usually requires a delay of 24 hr before it can be interpreted as positive for myocardial injury. The information obtained from serum creatine kinase-MB levels is also delayed. A history of angina pectoris may be the only evidence of ongoing myocardial infarction in these patients. It would be highly desirable to have a noninvasive tool available for diagnosis and localization of early acute myocardial injury.Echocardiography has traditionally been used as an imaging device. Recent work by several investigators suggests that interactions between the ultrasound energy and tissue can be analyzed to characterize the histologic state of tissue, both in vitro1' 2 and in vivo.36

KEY WORDS: Two-dimensional ultrasonic echocardiography, 'RAO equivalent' view, left ventricular ejection fraction, biplane cine-angiography. ! as well as when the parasternal short axis and the apical twochamber views were used for biplane volumetry! 2 !. It appeared to us that two strictly orthogonal views obtained with the same transducer location and transecting the left ventricle longitudinally would probably produce more realistic determinations of its volume. To assess this, we initiated a prospective study involving patients with and without localized wall motion disorders. In each case we calculated the volumes by a modified procedure •This work was supported by a grant from the Swiss National Science Foundation.from the classical apical four-chamber view and the 'RAO equivalent ' view! 5 ], orthogonal to the former. Thereafter, we determined the volumes from biplane right (RAO) and left (LAO) anterior oblique cine-angiograms. Our echocardiographic approach differs from that of Silverman et a/.! 4 ! in paediatric patients insofar as the plane of our 'RAO equivalent' view transects the true anterior and the inferior walls of the left ventricle and does not contain portions of the right ventricle. MethodsFifty-four patients undergoing routine catheterization and biplane cine-angiography were studied by 2-D echocardiography the day before the invasive procedure. Forty-two patients had satisfactory investigations with both methods and form the material of the present study (Table 1). Twelve patients were excluded because the 2-D echoes were not satisfactory, because of ectopic beats during cine-angiography, or the heart rate differed more than ± 15 b.p.m. between the two investigations. All patients were in sinus rhythm. ECHOCARDIOGRAPHIC IMAGESTwo-dimensional echocardiograms were ob-0195-668X/81 /O3O217+09 $01.00/0

For the purpose of the quantitative assessment of subtle disease processes in the cardiovascular system an electronically steered sector scanner that combines echographic imaging and Doppler blood velocity measurements has been developed. The integrated operation of a fast Fourier transform (FFT) Doppler signal processor for the simultaneous blood velocity evaluation of 64 individual gates is among the specific design goals. The instrument incorporates an unusually high degree of digital signal processing, which allows for high integration density, easy manufacturing and high reliability in future designs. The complex Doppler spectra are determined for each of the 64 Doppler gates in real time, and the subsequent computation of the first moment provides a reliable estimate of the mean blood flow velocities at the respective locations. The instantaneous velocity profile along the Doppler beam is displayed together with the calculated volume flow rate and a range-selected complete frequency spectrum. Results of both in vitro and in vivo tests indicate that in the future, a higher degree of digital signal processing could be implemented in complex ultrasonic systems.