Ultrasound Physics and Instrumentation

Ultrasound Physics and Instrumentation

Question # 1

Tissue Harmonic Imaging

Tissue Harmonic Imaging is the latest sonographic technique, which can produce images of better quality as compared to conventional sonographic technique. These are the frequencies that occur because of the transmitted sonographic frequency. In the sonography of the conventional gray scale, the wave with frequency emitted and transmitted into the patient receives to provide sonographic image. In Tissue Harmonic Imaging sonography, the Ultrasound beams through tissue with higher frequencies generated to produce sonography. This offers various advantages in the field of ultrasound. For example, including modified lateral resolution, improved signal to noise ratio and reduced sidelobe artifact (Shapiro, Wagreich & Parsons, 1998, p 1203).

Harmonic imaging provides the clearer image that lead to significant clinical diagnosing and information. Through the harmonic imaging lesions can be identified. Mostly on occasions harmonic images point out the hidden or invisible lesions even in retrospect. The situation of the focal liver and duct stones are the example of harmonic imaging.

It is usually happened as the penetration of the signal increases in the soft tissue, the fundamental transmit frequency decreases. On the other hand, axial, image resolution, elevational, and lateral decreases. As the ultrasound signal passes through the medium the frequency of the wave's changes. This change occurs because of the tissue resistance to the sound wave. This signal transmits back with twice the frequency and propagates the image.

Question # 2

Artifact

It is the term which means the disturbance in the wave's pattern on the monitor affected by electrode's movement.

Acoustic Shadow

The reflected amount of the sound beam depends upon the change in acoustic impedence of more than one tissue and the area and surface's shape. In case of large impedence between tissues the significant portion of the sound would be reflected and will not go in further depth (Brian, et al, 2007, p. 420). It occurs mostly when looking for the target that situated in more depth to the bone. In this acoustic shadow the violation occurring if the following assumptions.

The acoustic wave does travelling in a straight line

Each interface emits one reflection

These types of the assumptions may seem violated in the case of the soft tissue. It is useful for the diagnosing in cases where there is the presence of stones in image. Gallstones, usually observes with the help of the acoustic shadow they cast posteriorly. It can occur with ribs, and various calcified structures. It emits the sound waves when sound returns to the transducer with partial portion of the emitted waves and the rest absorbed (Gupta, Norman & Rantanen, 2007. pp. 24-25).

Acoustic enhancement artifact

It occurs when the waves travel through the tissue it occurs a mechanical loss that is loss of energy because of scattering or absorption. The waves passing through the medium of fluid experience less attenuation as compared to the waves passing through the soft tissue. As a result, the image region beyond the filled structure with fluid appears brighter than the nearby ...