Ultrasound
Ultrasound produces sound waves that are beamed into the body causing return echoes that are recorded to "visualize" structures beneath the skin. The ability to measure different echoes reflected from a variety of tissues allows a shadow picture to be constructed. The technology is especially accurate at seeing the interface between solid and fluid filled spaces. These are actually the same principles that allow SONAR on boats to see the bottom of the ocean.
Ultrasonography is body imaging using ultrasound in medical diagnosis. A skilled ultrasound technician is able to see inside the body using ultrasonography to answer questions that may be asked by the medical practitioner caring for the patient. Usually, a radiologist will oversee the ultrasound test and report on the results, but other types of physicians may use ultrasound as a diagnostic tool.
A transducer, or probe, is used to project and receive the sound waves and the return signals. A gel is wiped onto the patient's skin so that the sound waves are not distorted as they cross through the skin. Using their understanding of human anatomy and the machine, the technician can evaluate specific structures and try to answer the question asked by the patient's physician. This may take a fair amount of time and require the probe to be repositioned and pointed in different directions. As well, the technician may need to vary the amount of pressure used to push the probe into the skin. The goal will be to "paint" a shadow picture of the inner organ that the health care practitioner has asked to be visualized.
Diagnostic Uses
Echocardiology
Echocardiography (echo=sound + cardio=heart + graphy=study) evaluates the heart, the heart's valve function, and blood flow through them. It also evaluates the heart wall motion and the amount of blood the heart pumps with each stroke.
Different groups of illnesses can be assessed by echocardiography:
● Valves in the heart keep blood flowing in one direction when the heart pumps. For example, when the heart beats, blood is pumped from the left ventricle through the aortic valve into the aorta and the rest of the body. The aortic valve prevents blood from back-flowing into the heart as it fills for the next beat. Echocardiography can determine if the valve is narrow or leaking (regurgitating, insufficient). By following how the patient fares clinically, repeated echocardiograms can help determine whether valve replacement or repair is warranted. The same principles apply to the mitral valve which keeps blood flowing from the left atrium to the left ventricle.
● The heart muscle pumps blood to the body. If the heart weakens, the amount of blood it pumps with each beat can decrease, leading to congestive heart failure. The echocardiogram can measure the efficiency of the heart beat and how much blood it pumps; which assists in determining whether medications are needed. It also is used to monitor how well medications are working.
● Echocardiography can visualize the heart chambers to detect blood clots in conditions such as atrial fibrillation (an irregular heart rhythm). In other situations, the test can help diagnose endocarditis (an infection of the heart valves) by visualizing "vegetations" (an infected mass) on the valves themselves.
● Echocardiography also can detect abnormal fluid collections (pericardial effusions) in the pericardium.
● Echocardiograms are used to diagnose and monitor pulmonary artery hypertension.
Blood Vessels
Ultrasound can detect blood clots in veins (superficial or deep venous thrombosis) or artery blockage (stenosis) and dilatation (aneurysms). Some examples of ultrasound testing include:
● Carotid ultrasound is performed in patients with transient ischemic attacks (TIAs) or strokes to determine whether the major arteries in the neck are blocked causing the decreased blood supply to the brain.
● The aorta is the large blood vessel leaving the heart that supplies blood to the rest of the body. The walls of the aorta are under significant pressure from the force of the heartbeat and over time, may weaken and widen. This is called an aneurysm, and it can be detected in the abdomen by ultrasound (abdominal aortic aneurysm). For those patients with small aneurysm, observation may be recommended and the aneurysm size followed over time by repeated tests.
● Veins can also be evaluated by ultrasound and it is a common test to assess whether swelling in a leg is due to a blood clot, deep vein thrombosis (DVT) or another cause.
Abominal Structures
Aside from its use in obstetrics, ultrasound can evaluate most of the solid structures in the abdominal cavity. This includes the liver, gallbladder, pancreas, kidneys, bladder, prostate, testicles, uterus, and ovaries.
Ultrasound is the preferred to test to screen for gallstones or an infected gallbladder. The ultrasound can reveal the stones as well as signs of infection, including thickening of the gallbladder wall and fluid surrounding the gallbladder. The ultrasound may find blockage in the bile ducts.
For those patients where the radiation of a CT scan (computerized tomography) is a potential risk (pregnant patients or children), ultrasound may be used to look for diseases like appendicitis or kidney stones.
Ultrasound is the test of choice to diagnose testicular torsion.
Pelvic ultrasound is used in gynecology to help assess non-pregnancy related issues like lower abdominal pain, ovarian cysts, uterine fibroids, uterine growths, and endometriosis.
The Neck
The thyroid gland can be imaged using ultrasound looking for nodules, growths, or tumors.
Knee Joint
Ultrasound can be used to detect bulging of fluid from a swollen knee joint into the back of the knee, called a Baker's cyst.