Mark Oren, M.D., FACP
An ultrasound test sends and receives high-frequency sound waves to create images of internal organs or tissues. Sound waves pass into the tissues of the area being examined. These sound waves are reflected (bounced back), recorded and displayed on a computer screen or television-type monitor. The technology used in ultrasound in similar to sonar.
Ultrasound may be used to diagnose a number of medical conditions, including cancer. It creates images of soft tissue organs, such as the gall bladder, liver, heart, kidney and female reproductive organs. Ultrasound is especially useful in diagnosing cancer when a tumor is located in soft tissue and it is unclear whether an abnormality is a cyst (sac of fluid) or a solid mass.
The images created by an ultrasound are considered to be less clear than those from CAT scans (computed axial tomography) or MRIs (magnetic resonance imaging). They can provide different information than these tests, however, and can be used for a wide array of reasons. Unlike CAT scans and MRI, ultrasound does not use any form of radiation. Because it is fast, noninvasive and relatively inexpensive, ultrasound is frequently used to help with the diagnosis and treatment of certain cancers.
About ultrasound & cancer
Ultrasound, which is sometimes called ultrasonography or sonogram, uses high-frequency sound waves to create images of organs, blood vessels and tissues. The frequency of sound waves is too high for the human ear to hear, but they produce an image that allows physicians to view internal organs and to assess blood flow through various vessels.
Ultrasound technology can help a physician to diagnose cancer, especially when a tumor is located in soft tissue and it is unclear whether an abnormality is a cyst (sac of fluid) or a solid mass. It also can be used to help guide physicians during certain procedures, such as needle biopsies. In addition, ultrasound does not expose the patient to any radiation. For this reason, it is sometimes a preferred alternative to x-ray tests in assessing the conditions of certain populations, such as pregnant women and infants.
Inspired by sonar technology, which uses sound waves to detect objects underwater, ultrasound or ultrasonography can help diagnose a wide range of diseases and conditions. Ultrasound may be used alone or with other diagnostic procedures. Sonography is the medical term for the testing and recording of the ultrasound.
Ultrasound may be used to examine the internal structures of the abdomen (e.g., liver, spleen pancreas, ureters, kidneys), as well as for detecting gallstones and kidney stones. Other common uses for ultrasound include the detection of:
- Fluid, cysts, tumors or abscesses in the breast, liver or abdomen
- Reduced blood flow due to clots or arteriosclerosis in the legs
- Aneurysms of the aorta
- Abnormalities of the thyroid gland in the neck
- Gynecological problems in women, such as thickening of the endometrium.
Ultrasound is also used in physical therapy as the thermal effects have been found to be helpful for treatment of musculoskeletal injuries, breaking down scar tissue and helping to stretch tendons.
Role of ultrasound in cancer diagnosis
Ultrasound technology may be used to evaluate many forms of cancer, including:
- Breast cancer. A physician may use ultrasound to analyze an abnormality that has appeared in a mammogram or that was found during a clinical breast exam. Many women will experience a lump in their breast at some time, but it is usually a fluid-filled sac called a cyst. Cysts are rarely cancerous, and an ultrasound can help reveal whether the lump contains fluid or whether it’s a solid mass, indicating possible cancer. Sound waves will penetrate a fluid, whereas they will bounce back if the lump is solid. It is a valuable diagnostic tool for determining the presence of a tumor.
Ultrasound is often used as a follow-up test to an inconclusive mammogram or in addition to a mammogram or MRI in women who are at high risk for breast cancer. In some cases, a lump may be difficult to detect in dense breast tissue and may only show up as overlapping shadows in the mammogram. On the other hand, ultrasound may be able to distinguish differences in the density of the tissues and to pinpoint areas where denser tissue may indicate a tumor.
- Ovarian cancer. A pelvic ultrasound is used to send and receive high-frequency sound waves through a woman’s pelvic area. This can help determine whether an ovarian abnormality is a cyst or tumor.
- Endometrial cancer. A transvaginal ultrasound used to detect endometrial abnormalities. A lubricated probe is inserted into a woman’s vagina that sends sound waves into the tissues. The echoes from the sound waves create an image on the screen that helps determine the presence of a tumor. It can also detect a thickening of the endometrial lining and lesions in the tissue. Some physicians put salt water (saline) into the uterus before the sonogram to help see the uterine lining more clearly. This procedure is known as an ultrahysterosonogram.
- Gallbladder cancer. Ultrasound is one of the primary tests performed when a patient is diagnosed with jaundice. Ultrasound is particularly good at diagnosing gallstones and obstructed bile ducts, and can reveal the presence and extent of tumors. In some cases, endoscopic ultrasound will be used. In this test, an ultrasound transducer (a wand-like device that sends and receives high-frequency sound waves) is attached to the end of a flexible, lighted tube known as an endoscope. The endoscope is passed through the throat, stomach and duodenum before reaching the common bile duct.
- Stomach cancer. An endoscope is used in this test, which can reveal whether or not cancer has spread into the stomach walls or to nearby tissues and lymph nodes.
- Esophageal cancer. A tiny ultrasound probe is passed through an endoscope and into the esophagus. This endoscopic ultrasound (EUS) also can be used to examine the walls of the upper and lower gastrointestinal tracts and nearby organs such as the lung and pancreas. It is beneficial in examining surrounding lymph nodes to determine whether the cancer has spread.
- Colorectal, liver or pancreatic cancer. Liver cancer and pancreatic cancer can be detected using a traditional external transducer (the instrument that produces the sound waves) technique. However, this type of ultrasound is not used to detect cancers of the colon or rectum. These diseases can be detected using a variation called an endorectal ultrasound, which uses a special transducer that is inserted into the rectum. An intraoperative ultrasound can also be used to detect colorectal cancer. This technique is used when a surgeon has opened the abdominal cavity, allowing the transducer to be placed directly against an organ.
- Retinoblastoma. This childhood cancer of the eye is detected by applying a small ultrasound probe to the surface of the eye. It is used when tumors of the eye are so large that they prevent the physician from being able to see inside the entire eye.
Types and differences of ultrasound testing
There are various techniques of ultrasound imaging, including:
- A-mode, or amplitude modulation, which is recorded as a single line showing the time needed to reach the organ and return to the transducer
- B-mode, which is brightness modulation
- Gray scale, which shows the texture of various organs in shades of white and gray
- Real-time imaging, which shows rapid multiple views of tissues in motion
Some of the most common ultrasound tests include:
- Abdominal ultrasound. Used to view the kidneys, pancreas, gallbladder and other internal organs in the stomach area
- Breast ultrasound. Used to provide a closer look at a possible breast mass or in dense tissue
- Carotid duplex ultrasound. Used to view the carotid arteries of the neck for signs of disease
- Echocardiogram. Used to provide a closer look at the heart and its valves
- Interventional ultrasound. Often used to a guide a surgeon during a minimally invasive procedure, such as in the placement of biopsy needles or the drainage of infections
- Musculoskeletal ultrasound. Used to determine the cause of shoulder pain, tendonitis, a tear in the rotator cuff or possible sports injuries
- Pelvic ultrasound. Often used to find the cause of pelvic pain or discomfort
- Pregnancy ultrasound. Used to check the development of the fetus, including the baby’s heartbeat, size, location and, sometimes gender
- Prostate ultrasound. Used to obtain a closer look at any nodules that may have been detected during an exam
- Renal ultrasound. Used to specifically view the kidneys and urinary tract
- Thyroid ultrasound. Used to look for possible abnormalities in the thyroid
- Vascular ultrasound. Used to search for blood clots and view how well the vascular system is functioning
Before the ultrasound test
Preparations for an ultrasound test depend greatly on the type of ultrasound. Most ultrasound tests require little or no preparation. For ultrasounds being performed on internal organs, such as the gallbladder, patients may be asked to avoid eating or drinking for six to eight hours before the exam.
For other ultrasounds, such as gynecological or bladder tests, the patient may be asked to drink up to six glasses of water prior to the test to fill the area with extra fluid. The excess fluid in the bladder helps to move air-filled bowel loops away from the area of concern for a clearer view.
In preparation for an ultrasound, it may be helpful to ask a health care provider about:
- Eating or drinking restrictions prior to the test
- Smoking or using nicotine products before the test
- Leaving jewelry and valuables at home
- Wearing loose-fitting, comfortable clothing
- Avoiding soda or other carbonated drinks
- Taking any medications prior to the test
- Filling or emptying the bladder
During and after the ultrasound test
Most often, ultrasounds are performed on an outpatient basis, but these tests are also used in hospitals as part of diagnostic patient care. In general, most ultrasounds follow a similar procedure:
- Prior to the test, it may be necessary to change into a hospital gown to allow access to the body. Depending on the area being examined, the patient may lie on a padded examining table during the test. The room may be darkened to allow better viewing of the images on the monitor by the technician and physician. An ultrasound typically takes 20 to 30 minutes to administer.
- A small amount of water-soluble gel, which acts as a conductor, is placed on the part of the body to be examined and/or directly on the transducer. The transducer is a small device that sends the ultrasound waves through the body. If the transducer is a probe used in the vagina or anus, a thin rubber sheath is placed over the probe before it is lubricated and inserted into the opening. The gel does not harm the skin or stain clothing. It is important to note that the ultrasound’s transducer should not be placed over an open or draining wound.
- As the technician moves the transducer around an area, the sound waves sent from the transducer bounce off the structures within the body. The information is deciphered by the computer to create the ultrasound images.
- The ultrasound images appear on a television monitor for viewing. The technician is able to record the images on videotape and freeze images in a still picture.
- There is little or no pain associated with the ultrasound test though the tests done transvaginally or through the anus may be uncomfortable. There are no reported risks associated with a common ultrasound.
- After the test, the gel is wiped off of the skin. The test is evaluated by a physician specializing in radiology. In some cases, the physician may ask for additional images to be taken for a better view of an area. After the physician is satisfied with the results, the patient gets dressed (if necessary) and is allowed to leave. Patients may be given some preliminary results immediately following the test. However, the complete results of the ultrasound will be relayed to the physician who requested the test. They are usually reviewed with the patient in a follow-up visit or telephone call. It is important for the patient to indicate at the time of the test all of the physicians who should receive the results. If the ultrasound shows a problem, additional diagnostic tests, such as an MRI (magnetic resonance imaging), may be recommended.
Potential risks with ultrasound
In extensive studies, no risks associated with ultrasound have been documented. Ultrasounds are considered to be extremely safe, with no harmful side effects from the procedure. Unlike x-rays or CAT scans, an ultrasound does not use any radiation. This test is a noninvasive procedure that is widely available, easy to use and is considered painless.
Treatments that may follow ultrasound testing
Patients who are diagnosed with cancer may be treated in many ways. In some cases, one form of treatment will be considered. In many other cases, a combination of treatments will be used to fight the cancer. Commonly used treatments include:
- Chemotherapy. Uses one or more powerful drugs to destroy dividing cancer cells and to prevent them from reproducing and spreading throughout the body.
- Radiation therapy. Uses an energy called ionizing radiation to kill cancer cells and shrink tumors. Radiation targets dividing cancer cells and disrupts or destroys their genetic material, preventing the cells from continuing to grow and spread throughout the body.
- Biological therapy. Repairs, stimulates or enhances the immune system so that it can better recognize and destroy cancer cells. In some cases, biological therapy can directly attack cancer cells. This therapy is also used to blunt side effects associated with cancer treatments such as chemotherapy.
- Hormone therapy. Treatment for cancers that depend on hormones to grow and spread. Patients who undergo this treatment may take medications that reduce the levels of certain hormones, such as estrogen (in women) and testosterone (in men). In other cases, patients may take drugs that prevent cancer from attaching to hormones that help the disease to thrive.
- Surgery. Used for the complete or partial removal of a tumor.
- Bone marrow transplants. Replace bone marrow damaged by cancer or cancer treatments with healthy marrow obtained from a donor. Bone marrow contains stem cells that produce red blood cells, white blood cells and platelets necessary for life.
Questions for your doctor about ultrasound
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor or healthcare professional the following questions about ultrasound:
- Why do I need an ultrasound?
- What type of ultrasound will I receive?
- Do I need any preparation before the test?
- How long will it take to administer?
- Are there any risks involved with the test?
- Can this type of ultrasound detect cancer?
- When and from whom will I receive the results of the test?
- If a problem is detected, what tests might follow the ultrasound?
- Can I have an ultrasound if I am pregnant or nursing?
- Will I need to have future ultrasounds to monitor my condition?