Ultrasound: An Overview of Ultrasound Technology
Guest: Dr. Susan Ackerman – Radiology, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing Dr. Susan Ackerman, who is Associate Professor of Radiology and Director of Ultrasound here at MUSC. Dr. Ackerman, a lot of folks; mostly everybody, these days, has heard of ultrasound but don’t really understand what it is and why it can be so helpful in the diagnostic process. What can you, as a radiologist, see with an ultrasound that you couldn’t with the old fashioned, conventional, x-rays?
Dr. Susan Ackerman: Well, I think, first of all, we need to try to understand where ultrasound came from. Ultrasound first originated during World War II, when the Army; the military, used sonar to try to pick up the bed of the ocean to see if there were submarines, if there were bombs laying on the bed of the ocean. That’s how sonar was first used. And then, that kind of translated to the health field. They started out using it to look at babies, at the heart, and heart valves.
It has kind of evolved to almost everything now, particularly in my area. We do a lot of abdominal and pelvic imaging. We don’t do much obstetric ultrasound. That’s done by OB/GYN, primarily. And the vascular lab does most of the arterial and venous extremity studies. One of our more common ultrasounds is right upper quadrant (RUQ), to look at the gallbladder, the biliary tree, and the liver for abnormalities. Many patients present to us with abdominal pain; epigastric, and many doctors think, well, this could be gallstones.
Ultrasound is great for several reasons. One reason is that it’s portable. They actually make small machines now that you can carry with you, just like a handbag. So, you’ll see it [ultrasound] in many doctor offices. And one good use for these in the hospital setting is in the operating room. A surgeon might be looking for an abnormality, for instance, in the neck. Oftentimes, when they’re resecting a parathyroid lesion or small lymph node, it’s helpful to use intraoperative ultrasound when they’re dissecting in the area around nerves and vessels.
Dr. Linda Austin: So, just to clarify that a little bit, it becomes a guide; sort of a map, then, for the surgeon? So, the surgeon knows exactly what he or she is going to get into before they’re actually operating?
Dr. Susan Ackerman: Exactly. Another setting where it’s nice that it’s so portable is in intensive care, where you have a patient that’s on a ventilator, has a lot of tubes and lines; a difficult patient to move. In the intensive care unit, we can bring the machine up. It’s a small room. The patient doesn’t have to leave the intensive care unit.
Sometimes there are patients who are very sick, who are on ventilators, who are on multiple medications, and they’re not able to leave the floor easily. Sometimes they’re unstable. If a patient has fluid in their belly, or abdomen, for example, sometimes that fluid can become infected, particularly if they have liver problems. So, sometimes we use ultrasound to try to localize fluid. Ultrasound is very good for looking at that.
Dr. Linda Austin: So, in other words, ultrasound, then, one of the big advances is that it; unlike x-rays, which mostly look at hard substances; looks at soft tissues, and fluid.
Dr. Susan Ackerman: Ultrasound looks at soft tissues and fluid. That’s another good point about ultrasound. There’s no radiation. X-rays have radiation. CT scanners have radiation. With ultrasound, there’s no radiation. And so, that’s nice, because patients can have repeated ultrasounds without an increased incidence of developing radiation-induced carcinoma.
Dr. Linda Austin: Can you explain the difference between CT scans, ultrasound, and MRI? That’s a big question, I know. But if you could kind of sort it out, that would be helpful.
Dr. Susan Ackerman: Well, CT scans; CT is short for computed tomography, take pictures of all the organs, but it uses radiation to get that picture. MRI (magnetic resonance imaging) actually uses a magnet that aligns, basically, water molecules, or water, in the body to give you the different images. So, it’s a magnetization of sorts. Ultrasound uses sound waves that are integrated within the body. They’re absorbed and attenuated, and reflected at different sound wavelengths, depending on the substance. For example, sound travels through water differently than through the liver, therefore the picture is different.
Dr. Linda Austin: So, in other words, there’s a different physics involved in each of those?
Dr. Susan Ackerman: Correct.
Dr. Linda Austin: Then, is it fair to say that you might choose one or the other based on the kind of diagnosis you’re making; the kind of organ you’re looking; what you’re looking for?
Dr. Susan Ackerman: Exactly. Ultrasound is very good for looking at fluid. It’s very good for looking at the gallbladder. It’s a very good imaging modality to evaluate the female pelvis, to look at the ovaries, the adnexa, and to evaluate the endometrium. However, it’s not good for looking at the retroperitoneum.
Dr. Linda Austin: Which is, where?
Dr. Susan Ackerman: Deep within the body; very posterior, where your kidneys, ureters, and most of you bladder, are. Those structures are usually located too deep in the body for sound waves to penetrate very well. That’s where CT has a nice advantage; looking in the retroperitoneum.
Dr. Linda Austin: And, I would think that ultrasound, because it doesn’t involve radiation, would be very safe for a fetus.
Dr. Susan Ackerman: It is.
Dr. Linda Austin: Right.
Dr. Susan Ackerman: It’s very safe.
Dr. Linda Austin: Are there any risks associate with ultrasound?
Dr. Susan Ackerman: There are some risks with fetuses when using something called Doppler evaluation, which is used to look at cardiac activity; heart rate. There is some feeling; although not a lot of literature to support it, that high-intensity Doppler evaluation on a fetus, 8 to 12 weeks, may have a negative effect.
Dr. Linda Austin: Dr. Ackerman, thank you so much for talking with us today.
Dr. Susan Ackerman: Thank you.
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