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Coronary CTA Radiation: How Much Are You Really Getting? · Heart Health, Reimagined with Dr. Mona Shah, MD

• 0:00
  SPEAKER_00: I get this question all the time.
• 0:02
  SPEAKER_00: You talk a lot about coronary CTA angiograms, but what about the radiation?
• 0:07
  SPEAKER_00: And it's an important question.
• 0:09
  SPEAKER_00: Because if you Google coronary CTA radiation, you may see numbers like 10, 15, even 20 millisieverts.
• 0:16
  SPEAKER_00: Then you may hear from someone else that their scan was only one or two millisieverts.
• 0:22
  SPEAKER_00: So which one is right?
• 0:23
  SPEAKER_00: Potentially both.
• 0:24
  SPEAKER_00: Here's a biggest misconception about coronary CTA: that it comes with one fixed radiation dose.
• 0:32
  SPEAKER_00: It doesn't.
• 0:33
  SPEAKER_00: And some of the higher numbers you still see online come from older scanners and older protocols that may not reflect how coronary CTA is being performed today.
• 0:45
  SPEAKER_00: I'm Dr.
• 0:46
  SPEAKER_00: Mona Shaw, preventive cardiologist, board certified in holistic medicine as well as cardiac CT.
• 0:52
  SPEAKER_00: My focus is early detection and helping you understand not just whether to get a test, but what it actually means for your risk.
• 1:00
  SPEAKER_00: So in this video, I want to answer three things.
• 1:04
  SPEAKER_00: How much radiation are you really getting?
• 1:08
  SPEAKER_00: What does that mean in terms of cancer risk?
• 1:11
  SPEAKER_00: And most importantly, when is the information from the test worth that exposure?
• 1:17
  SPEAKER_00: But first, why would I even order a coronary CTA?
• 1:20
  SPEAKER_00: A coronary CTA angiogram lets me actually look at the coronary arteries themselves.
• 1:26
  SPEAKER_00: I can see whether plaque is present, including non-calcified or soft plaque, that a calcium score can miss.
• 1:33
  SPEAKER_00: I can see how much plaque is in there, where it is, and whether it is causing narrowing in the artery.
• 1:40
  SPEAKER_00: And in the right patient, that information can change how aggressively I approach prevention and treatment.
• 1:48
  SPEAKER_00: I don't think everyone needs a coronary CTA, but if knowing what is actually happening inside someone's coronary arteries could meaningfully change what I do for that patient, then the test can be very valuable.
• 2:02
  SPEAKER_00: I have an entire separate video that goes much deeper into what a coronary CTA can show and why it can be important.
• 2:10
  SPEAKER_00: I'll link that below.
• 2:12
  SPEAKER_00: And I also have another video comparing coronary CTA, calcium scorning, and CIMT.
• 2:19
  SPEAKER_00: So if you want to understand what each of those tests can and cannot tell you, I'll link that below as well.
• 2:25
  SPEAKER_00: Now let's talk about the actual radiation.
• 2:27
  SPEAKER_00: A millisievert, the unit I'll keep using, is simply how we measure a radiation dose.
• 2:34
  SPEAKER_00: There's no single number.
• 2:36
  SPEAKER_00: With a modern scanner and a well-optimized protocol, some coronary CT angiograms can be performed in the 1 to 5 millisievert range, and sometimes even lower in selected patients.
• 2:49
  SPEAKER_00: But that's not what everybody gets.
• 2:51
  SPEAKER_00: A large recent international study looked at this in the real world and found a median around 7 millisieverts with a very wide range between imaging centers.
• 3:02
  SPEAKER_00: So don't walk away thinking every modern coronary CTA is 2 millisieverts, or assume it's always 15 to 20.
• 3:11
  SPEAKER_00: Neither extreme is accurate.
• 3:13
  SPEAKER_00: Years ago, coronary CTA commonly used older scanning techniques that could expose patients to 10, 15, 20 millisieverts, or even more.
• 3:24
  SPEAKER_00: Modern technology has changed that dramatically.
• 3:27
  SPEAKER_00: Scanners are faster, we can often time the scan to a specific part of the heartbeat instead of imaging continuously.
• 3:35
  SPEAKER_00: We can use lower radiation settings, and image reconstruction has improved.
• 3:41
  SPEAKER_00: But your dose also depends on you.
• 3:44
  SPEAKER_00: These are the things that matter: your body size, your heart rate, and rhythm, how much anatomy needs to be scanned, and whether additional images are needed.
• 3:54
  SPEAKER_00: That is why two people can both have a coronary CTA and receive very different radiation doses.
• 4:03
  SPEAKER_00: If you like these deeper dives into heart disease prevention and imaging, make sure you subscribe.
• 4:09
  SPEAKER_00: I put out a new video every week, and this is really the heart of precision medicine to me.
• 4:15
  SPEAKER_00: Not just telling you what tests or number you have, but what it actually means for your long-term cardiovascular risk.
• 4:22
  SPEAKER_00: Now, let's put these radiation numbers into perspective.
• 4:26
  SPEAKER_00: We receive about three millisieverts of natural background radiation every year simply from living on Earth.
• 4:33
  SPEAKER_00: So roughly one millisievert is about four months of natural background radiation.
• 4:40
  SPEAKER_00: Three millisieverts is about one year, and ten millisieverts is a little over three years.
• 4:46
  SPEAKER_00: That is not a perfect biological comparison, but it gives you an easier way to understand the scale.
• 4:53
  SPEAKER_00: Now compare that with some common medical tests.
• 4:56
  SPEAKER_00: A dental x-ray is about 0.005 millisieverts, a chest x-ray is about 0.1, a mammogram is roughly 0.3 to 0.4 millisieverts, and a calcium score is usually around 1 millisievert, although that also can vary.
• 5:15
  SPEAKER_00: And then there's a nuclear stress test, which some people assume avoids radiation issue entirely.
• 5:21
  SPEAKER_00: It doesn't at all.
• 5:22
  SPEAKER_00: A nuclear stress test is often roughly 10 to 15 millisieverts, which can be more radiation than a modern low-dose coronary CTA.
• 5:31
  SPEAKER_00: So you can't just compare test names, you have to know how each one is actually performed.
• 5:37
  SPEAKER_00: Now, let's get to the question most people really want answered.
• 5:41
  SPEAKER_00: Can the radiation from a coronary CTAs cause cancer?
• 5:46
  SPEAKER_00: Cancer risk from radiation is probabilistic, not a single threshold where it suddenly starts.
• 5:52
  SPEAKER_00: As dose increases, the probability of harm may increase.
• 5:57
  SPEAKER_00: But there's no magic number where everything below it is safe and everything above it is dangerous.
• 6:02
  SPEAKER_00: You may hear the number 100 millisieverts.
• 6:06
  SPEAKER_00: Here's what that actually means.
• 6:08
  SPEAKER_00: Around 100 millisieverts from a relatively large exposure delivered over a short period is roughly where an increase in cancer risk becomes statistically detectable in large adult populations.
• 6:21
  SPEAKER_00: It is not a lifetime limit, and it doesn't mean that 99 millisieverts is safe and 100 is suddenly dangerous.
• 6:28
  SPEAKER_00: It is simply a useful reference point.
• 6:31
  SPEAKER_00: Now compare that with the doses we have been discussing.
• 6:35
  SPEAKER_00: A low dose modern coronary CTA might be around 1 to 5 millisieverts, roughly 20 to 100 times lower than 100.
• 6:44
  SPEAKER_00: And even a 10 millisievert study is a tenth of that amount.
• 6:48
  SPEAKER_00: At these lower diagnostic doses, any possible increase in an individual person's cancer risk becomes extremely difficult to directly measure.
• 6:58
  SPEAKER_00: That doesn't mean we can prove the risk is zero.
• 7:01
  SPEAKER_00: It means we have to estimate it.
• 7:04
  SPEAKER_00: The FDA gives a commonly used estimate that an exposure of about 10 millisieverts may carry approximately a 1 in 2,000 additional lifetime risk of fatal cancer.
• 7:16
  SPEAKER_00: I'll say that again.
• 7:18
  SPEAKER_00: The FDA gives a commonly used estimate that an exposure of about 10 millisieverts may carry approximately a 1 in 2,000 additional lifetime risk of a fatal cancer.
• 7:31
  SPEAKER_00: But this is really important.
• 7:34
  SPEAKER_00: Researchers didn't take 2,000 people, give every one of them a 10 millisievert CT scan, and then directly observe one additional cancer death.
• 7:44
  SPEAKER_00: That one in 2000 number is a modeled estimate based on what we know from higher radiation exposures and then mathematically extrapolated down to these much lower doses.
• 7:57
  SPEAKER_00: If you use that same model and roughly scale it down, at one millisievert, the estimate would be around 1 in 20,000.
• 8:06
  SPEAKER_00: At 5 millisieverts, around 1 in 4,000, and at 10 millisieverts, around 1 in 2,000.
• 8:13
  SPEAKER_00: Again, very important, these are modeled estimates, not directly measured cancer rates from coronary CTA.
• 8:21
  SPEAKER_00: And your individual theoretical risk is not the same as everyone else's.
• 8:26
  SPEAKER_00: It tends to be higher in younger patients, lower as you get older, and it can differ some between women and men.
• 8:34
  SPEAKER_00: So I think differently about radiation exposure in someone who's 30 than I do in someone who's 70.
• 8:40
  SPEAKER_00: And what about having multiple scans over the years?
• 8:43
  SPEAKER_00: This is one of the questions I get asked constantly.
• 8:46
  SPEAKER_00: How many CT scans can I have in a year?
• 8:48
  SPEAKER_00: Does spacing them out actually even help?
• 8:51
  SPEAKER_00: Those exposures do add up.
• 8:54
  SPEAKER_00: There's no biological reset button after every scan.
• 8:59
  SPEAKER_00: There's no official yearly limit, and I would be a little suspicious of anyone who hands you a hard number like that.
• 9:05
  SPEAKER_00: But here's a rough anchor.
• 9:07
  SPEAKER_00: At a typical dose of around 5 millisieverts, it would take about 20 scans to reach that 100 millisievert reference point we talked about earlier.
• 9:17
  SPEAKER_00: So one coronary CTA every few years for a real clinical reason is not something I would lose sleep over.
• 9:25
  SPEAKER_00: Timing matters too.
• 9:27
  SPEAKER_00: The same total radiation spread out over many years generally carries less risk than getting it all at once.
• 9:35
  SPEAKER_00: So a coronary CTA this year and a calcium score three years from now is very different from stacking several scans back to back in a few months with no clear reason.
• 9:46
  SPEAKER_00: It's not about hitting some number of scans a year.
• 9:49
  SPEAKER_00: It's about whether each one is actually answering a question that matters now.
• 9:54
  SPEAKER_00: And a hundred millisieverts should not be viewed as some lifetime ceiling that you are slowly marching towards.
• 10:01
  SPEAKER_00: There's no number where your doctor says, you have reached your lifetime radiation limit.
• 10:06
  SPEAKER_00: You can never have another CT.
• 10:09
  SPEAKER_00: Instead, every scan has to earn its place.
• 10:13
  SPEAKER_00: And that brings me to what I think is the most important point in this entire video.
• 10:18
  SPEAKER_00: The question shouldn't simply be, does this test expose me to radiation?
• 10:22
  SPEAKER_00: Because yes, it does.
• 10:24
  SPEAKER_00: The better question is whether the information I'm likely to gain from it is important enough to justify that exposure.
• 10:32
  SPEAKER_00: That's precision medicine, matching the test and the risk to the person in front of me, not applying the same rule to everyone.
• 10:40
  SPEAKER_00: In medicine, we use a principle called Alara, A-L-A-R-A, as low as reasonably achievable.
• 10:48
  SPEAKER_00: If I'm going to order a test that uses radiation, I want the radiation dose as low as we reasonably can make it while still getting a high quality diagnostic study.
• 10:59
  SPEAKER_00: But there's an equally important question.
• 11:01
  SPEAKER_00: Do you need the test in the first place?
• 11:03
  SPEAKER_00: Because even a beautifully performed one millisievert corner CTA is unnecessary radiation if the information is not going to change anything.
• 11:13
  SPEAKER_00: On the other hand, if I can identify cornery plaque, soft plaque, or significant narrowing that I otherwise would not have known was there, and that information changes how aggressively I approach prevention or treatment, then that small radiation exposure may be very reasonable.
• 11:32
  SPEAKER_00: That is a risk-benefit calculation.
• 11:34
  SPEAKER_00: So I don't like either extreme.
• 11:37
  SPEAKER_00: CT radiation is dangerous, so avoid it.
• 11:40
  SPEAKER_00: Too simplistic.
• 11:42
  SPEAKER_00: Modern CT radiation is so low that it doesn't matter.
• 11:45
  SPEAKER_00: Also too simplistic.
• 11:47
  SPEAKER_00: Radiation matters, we should minimize it, and we should not order imaging simply because we can.
• 11:54
  SPEAKER_00: But we also should not become so afraid of a small theoretical radiation risk that we avoid a test that could give us important information about coronary artery disease.
• 12:05
  SPEAKER_00: And here's something practical you can do.
• 12:07
  SPEAKER_00: If radiation is something you are concerned about, ask your imaging center what the typical dose is for a coronary CTA on their scanner, and whether they routinely use modern dose reduction protocols.
• 12:20
  SPEAKER_00: The scanner, the protocol, and the individual patient all matter.
• 12:25
  SPEAKER_00: So if you take away one thing from this video, let it be this.
• 12:30
  SPEAKER_00: There's no single radiation dose for a coronary CTA.
• 12:34
  SPEAKER_00: Modern technology can dramatically reduce the exposure, and the theoretical cancer risk from one low-dose scan appears to be very small, though we cannot say it's absolutely zero.
• 12:47
  SPEAKER_00: And ultimately, the most important question isn't simply how much radiation am I getting?
• 12:52
  SPEAKER_00: It's is the information I am likely to gain from this test worth that exposure for me.
• 12:59
  SPEAKER_00: And if you want to hear more about coronary CTA, calcium scoring, and CIMT, and what each of those tests can actually show you, that video is on your screen now.