Radiology: Radiological Examinations
Guest: Dr. Walter Huda – Radiology, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: I’m Dr. Lind Austin. I’m interviewing Dr. Walter Huda, who is medical physicist here in the Department of Radiology, at MUSC. Dr. Huda, I bet a lot of people like me may be wondering just what, exactly, a medical physicist is. What’s a guy like you doing in a place like this, in order words?
Dr. Walter Huda: Okay. Well, my department, proudly, takes care of patients. And I have, I think, four roles in terms of what I do on a day-to-day basis. If you come to my department and look at the equipment we use, you’ll see that it’s fairly sophisticated. And it’s very expensive. The typical piece of imaging equipment, a CAT scanner or MR scanner, will cost one and half to two million dollars. And so, I would advise our department on the kind of equipment to buy, because I understand the underlying technology.
If we buy a CAT scanner, and it’s delivered to us, I will get out my gadgets and make measurements of the amount of radiation that patients would be exposed to, and how good the images are, before we scanned any patients. There are regulations in effect to make sure that our equipment continues to work properly. So, I run a quality control program to make sure that the equipment stays functioning in an appropriate manner.
And the fourth thing that I do, I think, is the most important. I advise on how the equipment should be used on patients. I want to try to get the best possible images for the least possible amount of radiation. Those are topics that I know and understand quite well.
Dr. Linda Austin: Now, anybody who has ever been a patient has been advised to get an x-ray or a CAT scan; CT scan, or maybe even an MRI (magnetic resonance imaging) scan. Why would a physician choose one versus the other?
Dr. Walter Huda: That’s an interesting question. The point is that different imaging modalities will show different kinds of things. So, let me give you an example. If I’m interested in the bone, and I’m interested in, say, things that have got calcium in them, I would use CT. But if I was interested in soft tissues, then I would use MR. In fact, MR will not show you anything about the bony structures that you have in the body. So, all the imaging modalities that we have at our disposal, they all show slightly different things. And you would use the one that is most appropriate for the types of things you’re looking for.
Dr. Linda Austin: What about plain old x-rays? What are they good at showing?
Dr. Walter Huda: Plain old x-rays are very convenient and cheap. They’re ubiquitous. You get them everywhere. The chest x-ray is the standard that we’ve had. I would estimate that a third of all exams in America are just conventional chest x-rays. It’s just a very simple general purpose type of radiological exam. It will tell you about lungs. It will tell you about things that you might have inside of you. It’s just sort of a general purpose thing. The only problem with a chest x-ray is that everything is superimposed on everything else. It’s like taking all the material and squishing it down onto one film, where a CT, it’s like cutting little slices through your chest region. You don’t have overlying and underlying tissues.
Dr. Linda Austin: Dr. Huda, with all the concern that people have about the impact of these procedures on their body, what about CAT scans, CT scans? Any evidence that CT scans might have detrimental effects on the human body?
Dr. Walter Huda: Okay. CT was invented about 30 years, or so, ago. It’s a very powerful imaging modality. We do about 60 million exams every year in North America. In terms of the radiation they deliver, it’s a relatively high-dose procedure. To the best of my knowledge, we have no credible evidence that any CT scan has caused detrimental effects in exposed individuals. It doesn’t mean that there aren’t any. I’m just saying that as far as we know, in all the studies that have been performed, there is no evidence in humans.
When I’m asked about people volunteering to have, for example, a CAT scan, whether there are any detrimental effects or possible risks, I say, yes. Theoretically, there are. But I always add that if there are such effects, they’re usually so small that it’s unlikely that we would be able to actually measure them in some kind study, where we would compare an exposed group with a non-exposed group.
Dr. Linda Austin: If I were a patient and was advised by my doctor to get an x-ray or some other imaging study, what are some of the questions I should ask?
Dr. Walter Huda: I would say you should ask two types of questions. If you have a concern about the radiation, you should ask if there are alternatives to conventional x-ray or a CT scan. And the other question you should always ask is, why? Why is this exam being performed? What kinds of information are you likely to get that would impact the way your physician is taking care of you? The idea behind any radiological exam is to get information that, hopefully, is going to impact on the way that you’re managed. In general, I would say that your physician can give you a credible reason why the exam is being performed. The chances are that it’s an indicated exam, and you really shouldn’t worry about the exam that you’ve had.
Dr. Linda Austin: It reminds me of an experience I had. I had back pain and was sent for a magnetic resonance imaging study, and it came back positive. The doctor said, look, there it is. I had a bulging disk. I said, wow, now what do we do? And he said, nothing. I thought, well, why do the study then? If it’s not going to change what you’re going to do, how does it help one to know if there’s a bulging disk or not?
Dr. Walter Huda: In general, I would agree, but you never know. I mean, first of all, there might have been something that would have impacted on the way the patient was going to be taken care of. So, I think you have to be a little bit careful. But I don’t think you should have exams performed in the way that I would call willy- nilly.
Dr. Linda Austin: So, they might have found a tumor; let’s imagine, a worse case scenario, in which it could have been very significant? So, what you’re saying is that the real question is: is there a chance that this could alter the way my treatment proceeds?
Dr. Walter Huda: Correct.
Dr. Linda Austin: How about pregnant women? What concerns should they have?
Dr. Walter Huda: What I would say about pregnant patients is that the most important thing to realize is that just because you are pregnant does not mean you shouldn’t be exposed to radiation, in the form of a CT scan or a chest x-ray. A pregnant patient should always be looked at in terms of a risk and a benefit. You have to ask: what are the possible risks? What are the benefits? And if the benefits of the exam outweigh any radiation risks, then, quite often, you will proceed with the exam. The other thing I would emphasize is that we’re very careful when we do exams on pregnant patients. I will quite often be contacted by a radiologist who will say, we plan to do an exam. They will ask what steps they can take to minimize any possible radiation exposure.
Dr. Linda Austin: A term that many folks might have heard, but not quite understand, is interventional radiology. What is that?
Dr. Walter Huda: Interventional radiology, you should think of as an alternative to surgery. If I wanted, 100 years ago, to understand what was going on in one of your major blood vessels, then I would have gotten a knife and cut you open, and taken a look. In interventional radiology, you insert a little tube into the blood vessel and squirt in a little bit of contrast material that’s visible on an x-ray image. And so, interventional radiology is, essentially, a convenient way of replacing traditional surgery.
Dr. Linda Austin: How about PET imaging?
Dr. Walter Huda: PET stands for positron emission tomography. It involves the use of radioactive materials. So, in physiology, you’re quite often interested in how a particular organ or tissue works. So, for example, you have a kidney. The kidney performs a certain role. It takes some kind of material and does chemical or physiological things with it. And if I put this material into you, and it either does or doesn’t do what it would normally do, the point is that I want to see it. And to see it, I label it with something that’s radioactive. Then, I need to be able to visualize the radioactivity.
The radioactive materials that we use in PET are things called positron emitters. And, they just give off a particular kind of radiation. It’s called a positron. And with a PET scanner; positron emission tomography machine, you can visualize the distribution of that radioactive material within the patient.
Dr. Linda Austin: Dr. Huda, thank you so much for talking with us today.
Dr. Walter Huda: You’re welcome.
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