■ 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 

■ Lack of sonographic training and experience 

■ 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. 

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

■ 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. 

-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