Effect of anisotropy and spatial compound imaging on renal cortical echogenicity in dogs.

The echogenicity of the renal cortex is an important parameter to consider in dogs that are suspected to have renal dysfunction. Focal increases in echogenicity have been attributed to neoplasia, infection, calcification, fibrosis, gas, and infarction. Anisotropic backscatter has been described as a source of focally increased renal cortical echogenicity in several species. The source of anisotropy appears to be the medullary rays, which are oriented perpendicular to the renal capsule. Spatial compound imaging (SCI) is an ultrasound setting that uses beam steering to acquire and average several overlapping scans of an object from different view angles, creating a compound image that is updated in real time. The impact of insonation angle and SCI on renal cortical echogenicity was evaluated ex vivo in eight kidneys from four dogs. Significant angle-dependent differences in cortical echogenicity were detected with both microconvex and linear transducers (P < 0.0001). Furthermore, the angle-dependent echogenicity differences persisted when SCI mode was used. Our finding that echogenicity was increased using a perpendicular insonation angle (90°) relative to the tubules, compared to a parallel insonation angle (0°) should assist in the interpretation of ultrasonographic images of the dog kidney.

The Mechanisms Underlying Vertical Artifacts in Lung Ultrasound and Their Proper Utilization for the Evaluation of Cardiogenic Pulmonary Edema.

The recent advances in lung ultrasound for the diagnosis of cardiogenic pulmonary edema are outstanding; however, the mechanism of vertical artifacts known as B-lines used for the diagnosis has not yet been fully elucidated. The theory of "acoustic trap" is useful when considering the generation of vertical artifacts. Basic research in several studies supports the theory. Published studies with pilot experiments indicate that clarification of the relationship between the length and intensity of vertical artifacts and physical or acoustic composition of sources may be useful for differentiating cardiogenic pulmonary edema from lung diseases. There is no international consensus with regard to the optimal settings of ultrasound machines even though their contribution to the configuration of vertical artifacts is evident. In the clinical setting, the configuration is detrimentally affected by the use of spatial compound imaging, the placement of the focal point at a deep level, and the use of multiple focus. Simple educational materials using a glass microscope slide also show the non-negligible impact of the ultrasound machine settings on the morphology of vertical artifacts.

Measurement of regional pulse-wave velocity using spatial compound imaging of the common carotid artery in vivo.

Pulse-wave velocity (PWV) is an important index for diagnosing cardiovascular diseases. The pulse wave is volumetric change induced by heartbeat or inflowing blood, and significantly depends on the propagating path and stiffness of the artery. In this study, PWV of the propagating wave was visualized using spatial compound imaging with high temporal resolution. The frame rate was 1000 Hz, or a time interval of 1 ms. Subjects were four young healthy males and one young healthy female (n=5, age: 23.8±1.17 years old), and the measurement area was the right common carotid artery. PWVs in four phases (the four phases of heart valve opening and closing) were investigated during a cardiac cycle. In phase I, the heart pulsates. In phase II, the tricuspid and mitral valves close, and the aortic and pulmonic valves open. In phase III, the tricuspid and mitral valves open, and the aortic and pulmonic valves close. In phase IV, the propagating wave is reflected. PWVs in phases II and III were easily observed. PWVs were 3.52±1.11 m/s in phase I, 5.62±0.30 m/s in phase II, 7.94±0.85 m/s in phase III, and -4.60±0.99 m/s for the reflective wave. PWV was measured using Spatial Compound Imaging with high temporal resolution, and the PWV in each phase may be used as the index for diagnosing stages of arteriosclerosis progression.