Test Details & Preparation
A chest ultrasound is a non-invasive (the skin is not pierced) procedure used to assess the organs and structures within the chest, such as the lungs, mediastinum (area in the chest containing the heart, aorta, trachea, oesophagus, thymus, and lymph nodes), and pleural space (space between the lungs and the interior wall of the chest). Ultrasound technology allows quick visualization of the chest organs and structures from outside the body. Ultrasound may also be used to assess blood flow to chest organs.
A chest ultrasound uses a handheld probe called a transducer that sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed on the chest at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the organs and structures of the chest. The sound waves bounce off the organs like an echo and return to the transducer. The transducer picks up the reflected waves, which are then converted into an electronic picture of the organs.
Different types of body tissues affect the speed at which sound waves travel. Sound travels the fastest through bone tissue, and moves most slowly through air. The speed at which the sound waves are returned to the transducer, as well as how much of the sound wave returns, is translated by the transducer as different types of tissue.
Prior to the procedure, clear, water-based gel is applied to the skin to allow for smooth movement of the transducer over the skin and to eliminate air between the skin and the transducer.
By using an additional mode of ultrasound technology during an ultrasound procedure, blood flow within the chest can be assessed. An ultrasound transducer capable of assessing blood flow contains a Doppler probe. The Doppler probe within the transducer evaluates the velocity and direction of blood flow in the vessel by making the sound waves audible. The degree of loudness of the audible sound waves indicates the rate of blood flow within a blood vessel. Absence or faintness of these sounds may indicate an obstruction of blood flow.
A chest ultrasound may used to assess the presence of excess fluid in the pleural space or other areas of the chest, especially when the amount of fluid is small. If excess fluid is present, ultrasound may be useful to determine the type of fluid, exudate (seen in inflammatory, cancerous, or infectious conditions) or transudate (fluid that has leaked from blood or lymph vessels for various reasons).