MRI, CT scans, X-rays and more -- a medical imaging overview
[00:00:00] Host Amber Smith: From Upstate Medical University in Syracuse, New York, I'm Amber Smith. This is "HealthLink on Air." Lots of times because of illness or injury, doctors need to have a look inside our bodies, and often they can accomplish that through one or more medical imaging techniques. To help us understand what's available in medical imaging today and in the future is Dr. Michele Lisi. She's an associate professor of radiology and interim chair of radiology at Upstate. I appreciate you taking time for "HealthLink on Air," Dr. Lisi.
[00:00:29] Michele Lisi, MD: My pleasure. Thank you for having me.
[00:00:31] Host Amber Smith: I think listeners have probably heard of X-rays, ultrasound, CAT scans, MRIs, but I'm not sure we really understand which is used for what, so I'd like to have you explain the differences. Can we start with X-rays, which I believe have probably been around the longest, is that right?
[00:00:47] Michele Lisi, MD: That is correct. X-rays have been around for quite a while, since the 1800s, actually. Plain X-rays are a two-dimensional picture of our body, so we look at, for example, a chest X-ray, and that's giving us a two-dimensional picture of what's inside our lungs, and it allows us to look at the bones.
[00:01:05] Host Amber Smith: Does an X-ray let you see tissue and organs?
[00:01:09] Michele Lisi, MD: We can see tissue and organs with X-ray, but the main reason for X-ray is looking at bones, and we do that for fractures, dislocations, when a joint becomes separated -- very common in the emergency department, also good in terms of the chest for looking for pneumonia, so there are some soft-tissue applications for plain X-rays, but the applications are much fewer than with other modalities.
[00:01:37] Host Amber Smith: Now what about ultrasounds? We've heard about ultrasounds being used during pregnancy, but there's other things they're used for as well, right?
[00:01:45] Michele Lisi, MD: Definitely. Ultrasound is a great tool, mainly because it doesn't give the patient any radiation. So it's based on sound waves, and yes, it is very common to be used in pregnancy for looking at the anatomy of the baby, but we also use it for the gallbladder. That's a very common reason to use it in the emergency department. If somebody is having pain, you can find gallstones or infection in the gallbladder. It's a very good screening tool to look at the liver, for example, or the kidneys for certain types of ailments, kidney stones. So, yeah, there are many reasons that we would use ultrasound rather than just pregnancy.
[00:02:23] Host Amber Smith: Is mammogram the same type of thing? Is that an ultrasound, or is that something else?
[00:02:28] Michele Lisi, MD: No, mammography is another form of X-ray, kind of like the plain X-ray that we talked about in the beginning. Mammogram does use radiation, but it's a different type of radiation than what we use for the X-ray, so it does allow us to see tissue better. So it's very good for looking at the breast tissue and looking for cancers.
[00:02:48] Host Amber Smith: We've probably heard of CAT (or CT) scans. Now, am I correct that that is computerized tomography?
[00:02:54] Michele Lisi, MD: Correct.
[00:02:55] Host Amber Smith: What is that used for? And is it the same thing as a PET scan?
[00:03:00] Michele Lisi, MD: So no, PET scans and CT scans are different. So a CT scan is a way that we can look at cross sections of the body. So, as I mentioned, with plain X-rays, you're looking at a two-dimensional picture of a three-dimensional structure, like our body; the CAT scan actually allows us to look at things in a three-dimensional way. So it does use radiation, X-ray radiation, just like the plain X-rays do, but it takes them in such a way that we can see the body as if we sliced it. And so you get much more anatomy in a CAT scan, it's more sensitive for certain things, and it's used for the entire body, from the head all the way down through the legs. We have various applications for that.
[00:03:42] Host Amber Smith: I like how you described it; it's like a 3D X-ray.
[00:03:45] Michele Lisi, MD: Yeah. We take the pictures and then with the computer, we can reconstruct them or form them into three-dimensional images.
[00:03:53] Host Amber Smith: Now, a PET scan is entirely something different?
[00:03:56] Michele Lisi, MD: A PET scan is entirely different. That is something where we are actually injecting a form of radiation into the patient, and we're looking at where it comes from within the body. That's very common for cancer imaging. The radioactive tracer that we call it, that you inject into the patient, is a sugar.
[00:04:16] Michele Lisi, MD: It's a type of sugar that cancer cells or cells that are active in the body actually want to eat the sugar. And so that tracer will go to those types of cells, and then we can generate an image based on where those sugar molecules go in the body, so totally different, but yet the same in a way.
[00:04:36] Host Amber Smith: Now, when are MRIs used, and that's magnetic resonance imaging?
[00:04:40] Michele Lisi, MD: That is, yes, magnetic resonance imaging. That's used in many different applications as well. Probably I would say the most common indications are for the brain. You get very nice pictures of the brain with MRI, and for joints, people that have joint injuries or ligaments, when they tear the ligaments or the tendons and muscles, MRI is very good at looking at those tissues. So, whereas with the X-ray, we see bone very well, MRI kind of gives us a little bit better depiction of the soft tissues. And also I will point out with MRI that we do not use radiation. It's a magnetic field. So there's no radiation to the patient with MRI.
[00:05:23] Host Amber Smith: Let me ask you, as a radiologist, you do you ever have physicians coming to you and saying, "Here's the situation; which imaging is the best thing for what I need?"
[00:05:32] Michele Lisi, MD: Definitely. There are so many things now that we're able to do with imaging, and there's always new technology. So, very often there'll be a conundrum that a physician may have and need our opinion on what to do next.
[00:05:45] Host Amber Smith: Well, what have I left out? Does nuclear imaging fit in anywhere?
[00:05:49] Michele Lisi, MD: It does. Yeah. So nuclear imaging sort of goes back to the PET scan. That's a form of nuclear imaging or, as we now call it, molecular imaging, and we do quite a bit of that as well. We have various tracers, as I mentioned, that can be injected into patients and will go to places in the body of various pathological conditions. For example, we do something called bone scanning, where we inject a tracer, and the tracer will go to areas in the bone that may be fractured, that may have cancer, and we can take pictures of that and see where that goes and detect where those abnormalities are. And molecular imaging is a very interesting, upcoming technique for looking at various types of pathology.
[00:06:35] Host Amber Smith: This is Upstate's "HealthLink on Air." I'm your host, Amber Smith, and I'm talking with Dr. Michele Lisi. She's an associate professor of radiology and
[00:06:43] the interim
[00:06:44] Host Amber Smith: chair of radiology at Upstate, and we've been talking about medical imaging. We've talked about X-rays and CT scans and MRIs and sonograms -- a variety of things. I wanted to know, are these modalities that we've talked about, are they widely available, even in small hospitals or medical centers, or do you have to go to a specialized center?
[00:07:04] Michele Lisi, MD: For the most part they are. Most places nowadays will have all modalities available. Some of the higher-end imaging, PET scans, for example, may not be available in all hospitals or in all medical systems, but definitely more widely available than they were in the past.
[00:07:22] Host Amber Smith: Are there risks that patients should be aware of? I know the different modalities, some of them have radiation, some of them don't, but in general, what do patients need to be aware of before they have medical images?
[00:07:35] Michele Lisi, MD: I think that just the fact that there is a dose of radiation that the patients will receive with X-ray or CAT scan or some of the molecular imaging or PET scan studies, but the dose is minimal. We have a lot of dose-reducing techniques now that are built into our machines so that the images are inherently safer than they used to be in terms of the radiation dose. Sonography or ultrasound really doesn't have a risk associated with it since that's all based on sound waves and not radiation, and magnetic resonance, or MRI, when we screen patients for those examinations, we just want to make sure that they don't have any metallic implants, or, if they do, there are many of the metallic implants that are very safe, actually. And most of them nowadays are safe for going into the magnet. But we do screen the patients and ask if they've ever had any implants or if they have any metal that we need to be aware of just in case there may be a problem, but for the most part, the medical implants are safe for the magnet.
[00:08:39] Host Amber Smith: Now, the medical imaging we've talked about, are they all static images or are there modalities that allow for live video of a medical image?
[00:08:49] Michele Lisi, MD: So with X-ray, there's something called fluoroscopy, that we can look at live images, for example, patients that are having difficulty swallowing, and they're concerned that they're aspirating or getting pneumonia because contents are going into their lungs. We can do studies where we actually watch them swallow. We give them food that's labeled with something we can see on the X-ray and have them eat in front of us, and we can watch the swallowing mechanism, and then ultrasound as well. We do take static pictures with ultrasound, but when you are in the room scanning the patient, that is basically like a live video image.
[00:09:27] Host Amber Smith: Now do radiologists learn all of these medical imaging modalities, and then, do they specialize in one or two, or are they expected to be able to do all of them?
[00:09:39] Michele Lisi, MD: That depends. Definitely, during the residency (training), we () learn all about all of the modalities and pretty much everything there is in radiology, as a general knowledge base, but then people typically do subspecialize after the residency, and it's not necessarily modality specialized. It's more of a, how shall I say, body-parts specialized. So for example, you have people that specialize in abdominal imaging or people that specialize in neuro -- the brain, the spine -- or the chest, for example, and those required different training. You have people that specialize in nuclear medicine, mammography. So there are definitely subspecialties within our scope, but again, it's more body-part based than modality based.
[00:10:27] Host Amber Smith: I want to ask you about types of imaging that are in development. Now, you mentioned molecular imaging, so that's already in use, but it sounds like it's pretty new, right?
[00:10:36] Michele Lisi, MD: Well, it's not new actually. Molecular imaging used to be referred to as nuclear medicine. It has been around for quite a while. As a matter of fact, a lot of the pioneering in nuclear medicine took place here at Upstate back in the '70s. One of the agents that's most commonly used for bone scanning was developed here at Upstate -- just a little piece of history, which is great.
[00:10:59] Host Amber Smith: I had no idea. What is the element called?
[00:11:01] Michele Lisi, MD: It's called MDP. And it was developed here in our lab, downstairs in the basement, back in, I believe, the early 70s. We had quite an extensive (radiology) department here at one time, so it has been around for quite a while, but so many new tracers are being developed, and many of these tracers now, not only are we able to use them to image patients, but we're using them to treat patients as well by labeling them with, say, different molecules that are capable of treatment of cancer, specifically, and that's something that's just rapidly developing, which is very exciting.
[00:11:41] Host Amber Smith: What would doctors like to be able to do with imaging that they aren't able to do right now?
[00:11:47] Michele Lisi, MD: A lot of times we do get asked to make a definitive decision about something; we see a lesion or something in the body, and they say, "Well, what is it? We need to know what it is." And sometimes we can't tell them. We wish we could, but sometimes you actually need to look at the cells. We're not the pathologist, we're the radiologist. I wish we could sometimes be a little more definitive, but I think that's probably what physicians would want the most from us. But we can't always tell exactly what something is. Just give our best guess a lot of times.
[00:12:17] Host Amber Smith: The images today -- are you looking at a computer screen, or do they get printed out still on paper of some sort?
[00:12:24] Michele Lisi, MD: No, that went away. Here at Upstate, we started using what we call a PACS (picture archiving and communications) system, which is what gives us the images on computer; back in 2004 is when we started doing that. So I think most places now are obviously in the computer-screen mode.
[00:12:41] Host Amber Smith: Are computers or artificial intelligence being used to help read and interpret images? Or do you think it will be in, in the future?
[00:12:48] Michele Lisi, MD: I do. That's something that's really been talked about quite a bit in radiology, not only for diagnosis, but also using artificial intelligence for making images look better while using less radiation to make the images. That's something that's being studied quite extensively. And we've been using artificial intelligence for mammography for quite a while to help define or to recognize lesions on mammography, and there are other applications that are coming along as well with chest imaging, abdominal imaging. We're not using it yet, but I think it's on the horizon.
[00:13:27] Host Amber Smith: I really appreciate you making time to give us this overview. My guest has been associate professor of radiology, Dr. Michele Lisi, who is interim chair of the radiology department at Upstate. I'm Amber Smith for Upstate's "HealthLink on Air."