Diagnostic ultrasound — your body's 'echo' in images

Previously, X-rays were used, and their potential harmful effects were already noted. Many people were concerned that ultrasound might be harmful in the same way, but a series of animal experiments provided reassuring evidence that ultrasound is harmless from that perspective, easy to perform and repeatable.

The idea for the ultrasound devices used in healthcare actually came from the sonar navigation devices used in World War I to detect submarines, which were based on the reflection of sound.

The principle of the method

Certain crystals (when electrically stimulated) emit sounds with frequencies too high for the human ear to detect — higher-frequency waves. These ultrasound waves travel at high speed in water and other fluid media, then reflect off surfaces they encounter. The physical basis is that the ultrasound beams emitted by the probe are reflected differently by different tissues. From the time elapsed between emission and return, the distance and size of tissues and structures can be calculated. The reflected signals can be converted into a visible "image." The method is not the same as photography, so experience is required to analyze the resulting image. From that point on, a great deal of useful information can be obtained for the diagnosis and treatment of various diseases and conditions.

Most ultrasound examinations are performed with an external (fixed or portable) ultrasound device, although in some cases a device is introduced inside the body to reach the area to be examined.

What does diagnostic ultrasound help with?

Ultrasound is a versatile diagnostic tool.

It makes individual organs and tissues visible. The physical dimensions of structures and their distances from each other can be assessed and even measured. Movements can be observed (e.g., blood flow, heart contractions, heart valve motion). Changes in organ size, structural abnormalities, developmental disorders are visible, as are cysts, stones, abscesses, benign fatty and muscular tumors, malignant tumors, and fluid in the abdominal cavity.

Let's look a little more closely:

• Abdominal ultrasound. Suitable for examining the organs of the abdominal cavity and the pelvis. The liver, gallbladder, pancreas, spleen, kidneys, bladder, and in women the uterus and ovaries, and in men the testicle and prostate can all be examined by ultrasound. It also allows assessment of larger blood vessels running in the abdomen and lymph nodes. Cysts, stones, abscesses, benign fatty and muscular tumors, malignant tumors and abdominal fluid can be detected.
• Gynecological ultrasound. On the one hand it assesses the condition of the uterus and ovaries, and on the other hand it monitors the health of the developing baby during pregnancy. Its primary goal in this context is to detect fetal abnormalities as early and as accurately as possible, and to shed light on the mother's health. Confirmation of an existing pregnancy can usually be done as early as the second week after the missed menstrual period if a home pregnancy test was positive.
• Cardiac ultrasound (echocardiography). Helps determine the size and shape of the heart, the dimensions of the heart chambers and atria. It provides an accurate picture of heart valve function and their closing function. Calcified deposits can also be seen. The motion of the heart muscle can be assessed. Blood flow data and volumes can be measured.
• Vascular (blood vessel) ultrasound. For evaluating blood flow — ultrasound of the carotid artery, neck vessels, and limb vessels: a special Doppler ultrasound is an excellent tool for precisely determining the location, structure and size of arterial calcifications and the stenoses they cause. Thanks to the examination, a tendency toward atherosclerosis that may lead to narrowing or occlusion of vessels can be detected early. It can provide information about phlebitis, venous thrombosis, and venous valve insufficiency.
• Breast ultrasound. For women under 35, breast ultrasound is recommended to detect tissue and structural changes (cysts, tumors, etc.), while for women over 35 mammography is recommended in addition to ultrasound.
• Thyroid ultrasound. Ultrasound is an indispensable tool for examining the two lobes and the parathyroid glands. It clearly shows the structure and size of the lobes, any nodules, cysts, or inflammatory processes in the thyroid. It also plays an important role in examining the large salivary glands and the neck lymph nodes.
• Prostate and genital ultrasound. Examines size and structural changes of the prostate and inflammatory processes. During testicular ultrasound the tissue structure of the testicle, the arteries and veins around the testicle, the layers of the scrotum, and the epididymis are assessed. Inflammations, tumors, and circulation disorders can also be detected. A testicular hernia, testicular tumor, and varicoceles can be identified.
• Joint ultrasound. Assesses inflammatory processes of the joints (synovitis). The joint capsule, ligaments, cartilage, tendons, and accumulation of joint fluid can be examined. It can also be extended to the surrounding skeletal muscles, so muscle injuries and hematomas can be seen.
• Bone ultrasound. Used to measure the mineral content of bones, for example when osteoporosis is suspected.
• Other soft-tissue ultrasound: examination of subcutaneous soft tissues, muscles, tendons, fatty tissue, blood vessels, connective tissue, and lymph nodes. Skin-related lesions are also assessed.
• Ultrasound-guided procedures. In these cases, the purpose of the ultrasound is to follow a specific intervention. For example, a sampling instrument can be seen under ultrasound. This is done for tissue sampling (so-called biopsy) or for tumor treatment.

Risks

Diagnostic ultrasound is a safe procedure that uses low-power sound waves. It is a relatively inexpensive and widely available diagnostic tool that can produce real-time, noninvasive (performed from outside the body) images without significant biological effects. There are no known risks.

Ultrasound is a valuable diagnostic tool, but it has limitations. Sound does not travel well through air or bone, so it is not effective for examining body parts that contain gas or are obscured by bone, such as the lungs or the head. For viewing these areas, your doctor may order other imaging tests such as CT or MRI scans, or X-rays.

Preparing for an ultrasound exam

Most diagnostic ultrasound exams do not require special preparation. There are, however, a few exceptions:

• For some examinations, such as gallbladder ultrasound, your doctor may ask you not to eat or drink for a certain period before the exam.
• For abdominal and pelvic examinations, you should not eat for 6 hours beforehand, and only noncarbonated water is recommended for fluid intake. Your physician will inform you how much water to drink before the exam. For pelvic or specifically bladder ultrasound, it is important to arrive with a full bladder, so avoid urinating before the exam.
• Additional preparation may be required for young children. There are ages and temperaments for which fear cannot be fully alleviated; in such cases the only solution is to perform the examination as quickly as possible within what is feasible. If you or your child are going to have an ultrasound, it is worth asking your doctor whether there are any special instructions you should follow or discuss before the exam.

Wear loose clothing for the ultrasound examination. You may be asked to remove jewelry for some exams, so it is advisable to leave valuables at home.

What to expect

Before the procedure

Before starting the ultrasound examination you may be asked to do the following:

• Remove any jewelry from the area to be examined.
• Remove some or all of your clothing.
• Lie down on the examination table.

During the procedure

Gel will be applied to your skin over the area being examined. This helps prevent air bubbles that can block the sound waves that create the images. This water-based gel is easy to remove from the skin and, if it gets on clothing, from clothes as well.

In Hungary, ultrasound examinations are predominantly performed by physicians, whereas in the West they are more often performed by sonographers — health technicians specifically trained for this role. Whoever performs the exam holds a small device (the transducer) in their hand and places or lightly presses it against the area to be examined. They move it as needed or reposition it to another spot. The transducer both emits and receives the ultrasound signal; piezoelectric materials (certain crystalline materials that generate an electric potential when mechanically stressed) are used in its construction. This probe sends sound waves into your body, collects the reflected sound waves, and sends them to a computer that creates the images.

Some diagnostic ultrasound examinations are not performed on the body surface but are introduced into a natural orifice of the body. Examples include:

• Transesophageal: a transducer inserted into the esophagus obtains images of the heart. It is usually performed under sedation (but not general anesthesia).
• Transrectal ultrasound: this exam uses a special transducer inserted into the rectum to obtain images of the prostate.
• Transvaginal ultrasound: a special probe is inserted into the vagina to obtain a more detailed view of the uterus and ovaries.

Ultrasound is generally painless. You may experience mild discomfort when the sonographer moves the probe over the area to be examined, especially if you are required to have a full bladder or if a probe is inserted into your body.

A diagnostic ultrasound examination usually takes a few minutes, but it can take 30–60 minutes.

Results

After the diagnostic ultrasound examination, a physician trained in interpreting ultrasound images (a radiologist) reviews the images and prepares a summary report. Your treating physician will receive this report and will discuss the results with you.

No recovery time is needed after an ultrasound examination (except for some procedures performed under sedation). You can immediately resume your usual daily activities. No adverse consequences related to the examination are expected.