Diagnostic Ultrasound

Diagnostic Ultrasound is a diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely recognized by the public. There are many diagnostic and therapeutic applications practiced in medicine. It can be used to "steer" a needle to a precise location in the body in order to deliver medication or to "hydro-dissect" a nerve that has been compressed, such as in Carpal Tunnel Syndrome or Ulnar Neuropathy, as well as to drain a fluid-filled cyst, such as ganglion cyst or a "Baker's Cyst" of the knee.

Strengths
▪ It images muscle, soft tissue, and bone surfaces very well and is particularly useful for delineating the interfaces between solid and fluid-filled spaces.
▪ It provides "live" images, where the operator can dynamically select the most useful section for diagnosing and documenting changes, often enabling rapid diagnoses.
▪ It does not use ionizing radiation, such as with X-Ray, CT Scan, or fluoroscopy.
▪ It has no known long-term side effects and causes no discomfort to the patient.
▪ It is relatively inexpensive compared to other modes of investigation, such as a CT or MRI Scan. ▪ Spatial resolution is better in high frequency ultrasound transducers than it is in most other imaging modalities.

Weaknesses
▪ Sonographic devices have trouble penetrating bone. For example, sonography of the adult brain is very limited though improvements are being made in transcranial ultrasonography.
▪ Sonography performs very poorly when there is a gas between the transducer and the organ of interest, due to the extreme differences in acoustic impedance.
▪ Even in the absence of bone or air, the depth penetration of ultrasound may be limited depending on the frequency of imaging. Consequently, there might be difficulties imaging structures deep in the body, especially in obese patients.
▪ The method is operator-dependent. A high level of skill and experience is needed to acquire good-quality images and make accurate diagnoses.
▪ There is no scout image as there is with CT and MR. Once an image has been acquired there is no exact way to tell which part of the body was imaged.