General information
Other names
FIGURE Carotid Artery Doppler Sonography
After the test
| Where It's Done | Who Does It | How Long It Takes | Discomfort/Pain |
| Doctor's office, clinic, or hospital bedside. | Technician or doctor. | 15-60 minutes. | None. |
| Results Ready When | Special Equipment | Risks/Complications | Average Cost |
| Immediately if a doctor is there to view sonograms; otherwise, up to a few days. | Ultrasound transducer, monitor with oscilloscope screen, and video and/or strip recorders; other equipment varies according to the purpose of the test. | None, although concomitant tests may entail some risk. | $$ (Cost varies depending on the part of the body being examined and other concomitant tests, e.g., exercise stress test.) |
Doppler ultrasound, echography, sonography, and ultrasonography.
Purpose- To examine internal organs for any abnormalities in structure or function.
- To observe the heart, liver, spleen, and other organs in real time.
- During pregnancy, to evaluate the fetus for normal development and gestational age.
- To evaluate blood flow through specific vessels, usually with the aid of a Doppler transducer.
- The ultrasound transducer emits harmless, high-frequency sound waves, which bounce off the internal structure(s) under examination and are echoed back to the transducer. These echoes are amplified and displayed on a monitor; they can also be displayed as tracings on videotape or graph paper.
- The study may also include M-mode recordings, in which the tracings show the organ in motion over a period of time (see the variations described below).
- The patient lies on an examining table with the part of the body to be examined exposed.
- A conductive gel is applied to the skin over the area under examination.
- You lie quietly as the person performing the examination moves the transducer over the skin surface while watching the monitor.
- You may be asked to shift positions to obtain other views of the organ(s) under study.
- Breast sonography, in which a woman lies face down on an examination table that includes a special water tank containing an ultrasound transducer. The transducer beams sound waves into each breast as it is immersed in the water. (Alternatively, each breast may be examined with a handheld transducer.) The resulting sonograms may be used as an alternative or in addition to information obtained from regular X-ray mammograms.
- Doppler studies, in which a special transducer is used to direct sound waves into a blood vessel, which are reflected back by moving red blood cells (see figure 3.3). The transducer then transforms these echoes into wave forms that can be recorded. There is also an audio receiver that amplifies the sound of flowing blood, which is then transmitted by an audio speaker. Faintness or absence of such sounds indicates an obstruction to blood flow. Color may be added to the blood to provide better information about changes in the pattern or velocity of blood flow. The results are based on wave-form analysis.
- Internal ultrasound studies, in which special transducers are inserted into various body organs, to achieve a more accurate picture of nearby structures, such as the back of the heart from inside the esophagus, the uterus from inside the vagina, or the prostate gland from inside the rectum.
- Ultrasound in conjunction with other procedures. Increasingly, ultrasound is used to guide or augment other tests, for example, to safely guide withdrawal of amniotic fluid during amniocentesis, or to observe the heart in action during and after an exercise stress test.
A special transducer directs sound waves into a blood vessel. An audio receiver amplifies the sound of blood moving through the vessel, allowing an examiner to detect areas of obstructed blood flow, not only by the visual image but also by sound.
The gel is removed, and you can resume your usual activities unless a doctor gives other instructions, as may be the case when ultrasound is performed in conjunction with other tests.
Factors affecting results- Obesity may distort sound waves and make some organs difficult to examine.
- The presence of barium, gas, and other materials used in other procedures can distort sound waves; thus, ultrasound tests should be done first.
A radiologist or other physician trained to interpret sonograms reviews the tracings and video and audio recordings for abnormalities.
Advantages- Ultrasound studies, by themselves, are painless, noninvasive, and safe.
- They are ideal for use during pregnancy because they don't require radiation or contrast material, which may be harmful to the fetus.
- They can be used to examine blood flow and an organ in motion; they can also be used to evaluate change over a period of time--for example, the possible expansion of an aneurysm, fetal development, tumor growth, or the progressive narrowing of a blood vessel.
- Some physical characteristics, such as obesity, may distort the images.
- Some critics charge that ultrasound, which is more costly than X-rays, is overused as a routine screening procedure.
- Accuracy depends on the skill of the operator.
