The stripe artifact in transcranial ultrasound imaging.

Objective: Transcranial images are affected by a "stripe artifact" (also known as a "streak artifact"): two dark stripes stem radially from the apex to the base of the scan. The stripes limit the effective field of view even on patients with good temporal windows. This study investigated the angle dependency of ultrasound transmission through the skull to elucidate this artifact.

A novel phase assignment protocol and driving system for a high-density focused ultrasound array.

Currently, most phased-array systems intended for therapy are one-dimensional (1-D) and use between 5 and 200 elements, with a few two-dimensional (2-D) systems using several hundred elements. The move toward lambda/2 interelement spacing, which provides complete 3-D beam steering, would require a large number of closely spaced elements (0.15 mm to 3 mm).

Noninvasive transesophageal cardiac thermal ablation using a 2-D focused, ultrasound phased array: a simulation study.

This simulation study proposes a noninvasive, transesophageal cardiac-thermal ablation using a planar ultrasound phased array (1 MHz, 60 x 10 mm2, 0.525 mm interelement spacing, 114 x 20 elements). Thirty-nine foci in cardiac muscle were defined at 20, 40, and 60-mm distances and at various angles from the transducer surface to simulate the accessible posterior left atrial wall through the esophageal wall window.

A numerical study of transcranial focused ultrasound beam propagation at low frequency.

The feasibility of transcranial ultrasound focusing with a non-moving phased array and without skull-specific aberration correction was investigated using computer simulations. Three cadaver skull CT image data sets were incorporated into an acoustic wave transmission model to simulate transskull ultrasound wave propagation. Using a 0.

[Response of lettuce to different nitrogen forms].

Solution culture experiment was adopted to investigate the influence of different nitrogen forms on lettuce growth and development and their nitrogenous nutritional characteristics. The results showed that the affinity of the roots of lettuce seedlings to ammonium nitrogen (NH4(+)-N) was slightly higher than that to nitrate nitrogen (NO3(-)-N). Among three treatments of NO3(-)-N, NH4(+)-N+ NO3(-)-N and NH4(+)-N, the relative proportion of biological yields of lettuce was 100:56.

Experimental spatial sampling study of the real-time ultrasonic pulse-echo BAI-mode imaging technique.

The ultrasonic pulse-echo backscattered amplitude integral (BAI)-mode imaging technique has been developed to inspect the seal integrity of hermetically sealed, flexible food packages. With a focused 17.3-MHz transducer acquiring radio frequency (RF) echo data in a static rectilinear stop-and-go pattern, this technique was able to reliably detect channel defects as small as 38 microm in diameter and occasionally detect 6-microm-diameter channels.