Dec 28, 2018
New technology and guidelines allow us to use PET-CT scans to locate cancer earlier than ever before, with faster scans and less radiation. Dr. Carlos Garcia explains what this means for patients and how we continue to stay ahead of the curve in this area of testing.
Intro: MedStar Washington Hospital Center presents Medical Intel where our healthcare team shares health and wellness insights and gives you the inside story on advances in medicine.
Host: Thanks for joining us today. We’re talking to Dr. Carlos Garcia, Medical Director of Nuclear Medicine at MedStar Washington Hospital Center. Welcome, Dr. Garcia.
Dr. Carlos Garcia: Hi. Thank you for having me.
Host: Today we’re talking about advances in PET CT technology. Dr. Garcia, what is PET CT technology and when is it used?
Dr. Garcia: So, PET CT technology is a combination of anatomic and functional imaging. We use the anatomy from the CT portion of the exam and the self-function or the live cell portion of the exam from the PET CT exam. We use it mainly for oncologic imaging. It can be used for other purposes as well, but right now the mainstay, the gold standard, for cancer imaging is PET CT imaging.
Host: How has PET CT scanning technology improved in the last 10-15 years?
Dr. Garcia: It’s improved by leaps and bounds, actually. So, in 2006, the new kid on the block was time-of-flight PET CT imaging, which was the most advanced cancer imaging tool at that point in time. Now that’s evolved as technology does into digital imaging. So, analog vs digital imaging.
Host: So, why should a patient come to MedStar Washington Hospital Center for a PET CT scan?
Dr. Garcia: We’ve been very fortunate in the past to, in 2006, to have the first, the most advanced machines in the region. It was called the Time of Flight PET scan, which was the upgrade from, you know, analog imaging from way before 2006, and for many years we were the only ones that had that type of imaging. And now, as of August this year, we have a digital PET scanner, so it’s the step up from the Time of Flight. It’s the most advanced PET CT unit available in the world right now and we are very fortunate to, once again, be one of the first in the region to actually have this kind of technology. When you compare it to the Time of Flight PET scan that we had prior to the one we have right now, it’s basically comparing a flat screen TV to a State-of-the-Art 4K curved screen. You’re talking about night and day when it comes to resolution. Images are 10 times, you know, as crisp as compared to what they were before, that everybody, you know, joked around they were a little fuzzy. Now, the lesion detection has increased. The size of the lesion can be much smaller and still be detected. The amount of time it takes to acquire the images has been cut back almost by 50 percent and the dose that we give the patient in order to obtain these higher-quality images can also, in some cases, be cut back as far as 50 percent as well. So, from a patient point of view, they get a much more reliable scan and half the amount of time with half the radiation exposure, and these are all valid concerns to the patient, you know, because coming to the hospital, you know, you can have a PET scan anywhere. You can have any kind of exam anywhere - it’s the experience you get from, you know, the center, the staff, the amount of time, the comfortability you experience. All those things put together makes it a much better experience to have a higher quality machine in the hands of somebody with much more experience. The result of that has been increase in detectability, increase in being able to see lesions that were too small to be seen before. And, that leads to early detection, early treatment application and, you know, being able to catch a disease when it’s still a time when something can be done about it.
Host: What sort of research are you working on right now for PET CT scanning, and what do you see coming down the road, either at MedStar Washington Hospital Center or nationally?
Dr. Garcia: So, there’s a ton of research being done at all levels with PET CT imaging and cancer applications. There’s many novel tracers, or let’s say substances, that the body produces that are getting linked to radiation and injected into the body and seeing exactly where it will go, known places that you know or known organs that you know it will go to, places that it would take up normally and now it takes up abnormally, and that gives us information. Here at the hospital, we are considered a thyroid/cancer center of excellence, so a lot of the research that we do will be related to imaging with radioactive iodine. There’s many different types; used some for therapy, some for imaging and in our case, we use it to be able to see lesions that are not taken up by the normal exams we do, the normal iodine scans that we do, and sometimes these tumors, in thyroid cancer specifically, may stop working the way they do and they don’t take up iodine. So, we do PET imaging in those particular cases, and that’s actually a proved indication, a reimbursed indication, for patients that are iodine-negative and that still have blood markers that show that there is still cancer and in those cases that’s an indication.
Host: When you’re talking about radioactive iodine, how is that being introduced into a patient’s body and what does that look like for thyroid cancer?
Dr. Garcia: So, in thyroid cancer patients we rely on the fact that the body does essentially one thing with iodine. When you eat it in your normal diet, the iodine gets absorbed, it goes straight to your thyroid gland, and your thyroid gland uses iodine to make thyroid hormone. The body can’t tell the difference between radioactive iodine or normal iodine or between different types of radioactive iodine. So, nine out of 10 times it is introduced as a pill. The body thinks it’s just normal iodine and it’ll take it to wherever there is thyroid tissue. If there’s a little bit of thyroid tissue left behind after the surgery, which happens 99 percent of the time, it will absorb the iodine because it still, you know, retains its function. So, the same thing will happen if the cancer has spread to other parts of the body and wherever the cancer cells have gone and attached themselves to, it is still thyroid cells now growing on, for example, a lung, a bone, you know, or in your brain. It’s still thyroid cells so they retain that function of taking up iodine. So, the body absorbs the pill it took and it’ll circulate through the blood and it’ll find the thyroid cells. And the thyroid cells will latch onto it, look at the iodine, try to make thyroid hormone out of it, but we’ve altered it chemically to get essentially stuck inside the cell and not be able to be metabolized further. All of this translates to being able to see it on images. Wherever the iodine has been absorbed it will show up on the images and that gives us an idea of the degree of spread throughout the body.
Host: Interesting. So, the difference between the PET CT and the regular CT scan is that ability to really track that cancer throughout the entire body. How does that benefit patients, especially in the situation of thyroid cancer, and then how is that helpful for the physician team to treat them?
Dr. Garcia: Not only does it track where it has gone throughout the body because CT exams can show you, as well, irregularities in anatomy, differences in what, you know, patterns are supposed to look like in every part of the body. It will show you where there are cells that are still alive. Sometimes it takes longer for a change to happen on a CT scan, based on the therapy that was applied, then it will take with the level of metabolic function of a cell. Sometimes you can have a tumor that’ll shrink a little bit on the scan when you compare one scan before and after the therapy and when you look at the PET scan it’ll show that there was a very active lesion and then it’s completely inactive. It’s essentially gone, although there’s only been a small shrinkage of the tumor on the CT scan. So, it’s very complimentary to the anatomy that would be shown on a CT scan. This helps physicians to monitor a treatment response. And many, many - even research studies - will take into account the degree of metabolic activity and the change before and after the therapy to see if the treatment is working and should continue or if the treatment is not working and they should switch gears altogether and try something different. It’s called the metabolic response to therapy. In thyroid cancer, we use it in those cases in which we know there’s thyroid tissue still in the body because it’s producing a protein that shows up in the blood, that’s only made by thyroid cells. Sometimes these thyroid cells lose their function to capture the iodine and makes a iodine scan basically not the right study to be able to monitor the response. So, you have to migrate over to the basics of the cell function, which is to take up glucose, for example. So, it will still, it still might be able to take up glucose even though it won’t take up iodine and that is still very, very helpful to know whether or not this patient would benefit from being treated with radioactive iodine or if they need to be treated with another form of therapy, based on the examination - the PET CT exam.
Host: So, a very technical and very advanced way to get back to the basics of what the cancer does.
Dr. Garcia: That’s nuclear medicine, in essence. We rely 100 percent on physiology, which is the normal function of the body. The kidney has a normal function, the brain has a normal function - and when they deviate from that normal function, they stop using the materials or the substances in your blood that they normally would. If you can attach radiation to that substance and then you see that it doesn’t go into the liver when it should, that gives us information - we know what that means. So, you’re basically relying on the body doing what it’s supposed to do, and variations of that function will translate into disease entities, into diagnosis that we can establish. So, we trick the body into doing what it would normally do - it doesn’t know it’s doing it - and we can see it all on images.
Host: What sort research are you and your and your colleagues working on right now in the field of PET CT?
Dr. Garcia: Right now, we are working mostly in thyroid cancer research. We are looking into how much iodine is absorbed in individual tumors. In the past the fact that it showed up on the scan at all was very productive, but what we need to see is how much radiation is being delivered to each individual lesion. And that will make a difference. So, it’s very important to figure out - this is the ongoing research for us - to figure out how much radiation actually gets delivered in a particular lesion. And that will sometimes answer the question of how come we gave the same radiation level to two different patients and it didn’t quite work the same way. And we need to figure out how much is absorbed in each piece of tissue, if you will, that is malignant, and that way, if we know that, then we can start tailoring lesion radiation delivery more so than patient radiation delivery. We will go, I mean, we treat the patient as a whole, of course, you know…but we will go after targeting specific lesions and making sure that that lesion receives as much radiation as possible. We’re very happy to not have repeat customers, you know, and that’s kind of our goal, I mean, like we’ll try to get it all on the first try and if not, leave as little behind as possible if we have to do it again.
Host: Thank you for joining us today.
Dr. Garcia: Ah, it was a pleasure. Thank you for having me.
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