ULTRASOUND


 INDICATIONS
■ Ultrasound is useful in the evaluation of
■ Cholecystitis
■ Abdominal aortic aneurysm
■ Ectopic pregnancy
■ Pericardial tamponade
■ Hemoperitoneum
■ Cardiac electromechanical dissociation
■ Hydronephrosis
■ Tendons, bursae, cartilage, synovium, synovial fluid, and bone
■ Fetus during routine and emergency prenatal care
■ Foreign bodies in soft tissues or eyes
■ To guide cannulation of vessels, aspirate fluid collections within cavities (eg, pericardium, pleurae, bladder, or joints), and locate soft tissue foreign bodies in the skin, soft tissues, or eyes
■ To mark the site for skin puncture or provide continuous real-time visualization throughout a procedure 

 CONTRAINDICATIONS
■ Lack of sonographic training and experience 

 TECHNIQUE
■ Lower-frequency probes (3-7 MHz) are used for viewing deeper structures but produce lower resolution images.
■ Higher-frequency probes (7-20 MHz) are used for viewing superficial structures and provide higher resolution images.
■ The "gain" controls the amplification of the returning signal. High gain will cause the image to appear white, low gain will produce dark images.
■ The depth gain control is a set of slide bars that allow you to set individual gains (brightness) at different levels.
■ The "magnify" function causes the field to be magnified with the skin surface remaining in the image.
■ The "zoom" function causes the boxed area of interest to be magnified. 

 COMPLICATIONS
■ Ultrasound is generally considered safe because it does not produce cancercausing ionizing radiation. However, prolonged ultrasound causes increased inflammatory response and heats soft tissue. 

 INTERPRETATION OF RESULTS
■ Catheters, wires, and needles appear as brightly reflective structures within fluid-filled anechoic spaces.
■ Arteries and veins appear as anechoic circular structures when viewed in the transverse plane. Veins are easily compressed, arteries are less easily compressed, and veins filled with clot are noncompressible. 

 NOTE:
-Medical diagnostic ultrasound uses sound between 3 and 20 MHz (106 times per second). This is above the upper limit for the human ear to hear sound of 20 KHz (103 times per second).
-Use a low frequency probe to see deep structures. For example, a 3.5-MHz probe is appropriate for a FAST exam 



  • Video 1