New concepts in echocardiography

If short pulses of high frequency sound are transmitted through the heart, discontinuities in the tissues will produce reflected sound waves or "echoes". There wil! be a delay between a pulse transmission and the arrival of a correspond·mg echo. Together with knowledge of sound velocity this wi!l enable determination of the distance between the transmitterfreceiver and the reflecting interface, thus providing information about cardiac dimensions. Similarly the Doppler effect can be used to provide further diagnostic information. These applications of ultrasound (echocardiography) for the detection of cardiac (mal)function have recently gained acceptance even though interpretation of the information obtained can be difficult. Major reasons for this acceptance are probably that, while

Intra-arterial ultrasonic imaging for recanalization by spark erosion

Presently several new methods are being developed to recanalize obstructed arteries during catheterization. Intra-arterial high frequency ultrasonic imaging may be used as a guidance for these new techniques. Spark erosion is a new obstruction removal technology. Experiments have shown that this method can be applied in a selective way. An ultrasonic intra-arterial imaging system allows for the proper indication of the spark erosion catheter relative to the obstruction. The first in vitro results of this study illustrate that integration of catheter tip imaging and spark erosion is possible

Characterization of plaque components with intravascular ultrasound elastography in human femoral and coronary arteries in vitro

BACKGROUND: The composition of plaque is a major determinant of coronary-related clinical syndromes. Intravascular ultrasound (IVUS) elastography has proven to be a technique capable of reflecting the mechanical properties of phantom material and the femoral arterial wall. The aim of this study was to investigate the capability of intravascular elastography to characterize different plaque components. METHODS AND RESULTS: Diseased human femoral (n=9) and coronary (n=4) arteries were studied in vitro. At each location (n=45), 2 IVUS images were acquired at different intraluminal pressures (80 and 100 mm Hg). With the use of cross-correlation analysis on the high-frequency (radiofrequency) ultrasound signal, the local strain in the tissue was determined. The strain was color-coded and plotted as an additional image to the IVUS echogram. The visualized segments were stained on the presence of collagen, smooth muscle cells, and macrophages. Matching of elastographic data and histology were performed with the use of the IVUS echogram. The cross sections were segmented in regions (n=125) that were based on the strain value on the elastogram. The dominant plaque types in these regions (fibrous, fibro-fatty, or fatty) were obtained from histology and correlated with the average strain and echo intensity. The strain for the 3 plaque types as determined by histology differed significantly (P=0.0002). This difference was mainly evident between fibrous and fatty tissue (P=0.0004). The plaque types did not reveal echo-intensity differences in the IVUS echogram (P=0.882). CONCLUSIONS: Different strain values are found between fibrous, fibro-fatty, and fatty plaque components, indicating the potential of intravascular elastography to distinguish different plaque morphologies

Cyclic changes of blood echogenicity in high-frequency ultrasound

Ultrasound images from human arteries obtained in vivo with an intravascular 30 MHz ultrasound imaging device show that blood echogenicity changes during the cardiac cycle. Quantitative measurements of blood echogenicity during the cardiac cycle suggest that these variations may be related to changes in the state of erythrocyte aggregation, which are induced by varying shear rate

The relative contributions of myocardial wall thickness and ischemia to ultrasonic myocardial integrated backscatter during experimental ischemia

Abstract The purpose of this study was to assess the empirical relationship between myocardial integrated backscatter (IB) and myocardial wall thickness (WT) in normal myocardium. A second object was to estimate the additional contribution to acute ischemic integrated backscatter levels given this relationship. Myocardial IB measurements and simultaneous myocardial WT measurements were made in 16 open-chested pigs with intact coronary circulation (normal myocardium) and 10 min after the flow in the left anterior descending coronary artery had been reduced to 20% of its baseline value (ischemic myocardium). Measurements were made 50 times during one cardiac cycle and averaged over 10 cardiac cycles. IB and WT measurements were normalized with respect to the nonischemic end-diastolic values. The relationship between IB and WT in normal myocardium was estimated in every individual pig by simple linear regression. Estimates of IB during ischemia were calculated on the basis of this relationship and the ischemic WT measurements. Differences of the estimator and the actual measurement made during ischemia depict the actual contribution of the state of acute ischemia, without the influence of WT. The slope of the relationship between IB and WT during normal myocardial contraction ranged from −0.16 to 0.03 dB/% (mean = −0.036 dB/%, SD = 0.06 dB/%). The additional contribution of ischemia ranged from −3.84 to 5.56 dB (mean = 0.31 dB, SD = 2.72 dB). It was concluded that the average contribution of ischemia to IB measurements is insignificant if the IB dependency on WT is removed from the data and that the higher level of ischemic IB measurements can be explained by the decrease in wall thickness during ischemia and not by the ischemia itself

Temporal averaging for quantification of lumen dimensions in intravascular ultrasound images

Quantitative analysis of arterial dimensions from high frequency intravascular ultrasound images (30 MHz) may be hampered by strong blood scattering. Replacement of blood by saline is one method to provide a clear view of the arterial lumen; another method is that of temporal averaging of successive ultrasound images. The accuracy of this latter method was tested by comparing the lumen area measurements on the temporal-averaged image, with the data of the same cross-section obtained from the single-frame and saline-filled images. The mean lumen area measured on the temporal-averaged images was similar to that measured on the single-frame images (mean difference: −0.02 ± 1.16 mm2; p = ns). The mean lumen a

Detection of vascular morphology by high frequency intravascular ultrasonic imaging

This study was designed to validate the potential clinical utility of intravascular ultrasonic imaging in vitro and in vivo. In vitro studies were performed to assess the accuracy of dimensional and morphological information. In vitro images of human vessels (n = 75) demonstrated that lesion thickness determined echographically closely related with histological samples (r = 0.83). Morphologically, muscular and elastic arteries could be distinguished echographically based on the echogenicity of the arterial media. Close relation was also found in the morphological subtypes of atherosclerosis. Subsequently, intravascular ultrasound was used percutaneously in vivo in 20 patients to obtain images of the iliac and superficial femoral artery. High quality real-time images were obtained. Normal vessels were seen showing pulsatile circular images with a hypoechoic muscular media resulting in a typical three-layered appearance. Diseased arteries revealed non-obstructive and obstructive lumen. At the site of obstruction thinning of the muscular media was evident. Pulsation was not always present. Following dilatation of the obstructive lesion using balloon angioplasty the ultrasonic cross-sections changed drastically revealing plaque rupture, dissection, plaque-free wall rupture, rest stenosis and oedema. We conclude that intravascular ultrasonic imaging is a promising technique to document accurate dimensional and morphological characteristics of human vascular disease for guidance of therapeutic interventions

The relationship between myocardial integrated backscatter, perfusion pressure and wall thickness during isovolumic contraction: An isolated pig heart study

The independent effect of myocardial wall thickness and myocardial perfusion pressure on integrated backscatter was investigated through experiments wherein integrated backscatter of normally perfused myocardial tissue was measured while changes in wall thickness during the cardiac cycle were reduced to a minimum. Results of the experiments show that integrated backscatter is mainly determined by myocardial wall thickness if only wall thickness and perfusion pressure are involved