Scan Safety: A Radiation Reality Check

By Esther Napolitano,

Wednesday, February 4, 2015

Summary

Medical physicist Lawrence Dauer explains what you should know about the use and safety of tests such as CT scans that use radiation to obtain images of the body.

Over the last few decades, there has been a dramatic increase in the availability and application of tests that use ionizing radiation to take images of the body. These tests include computed tomography, or CT, scans and nuclear medicine exams that utilize small amounts of radioactive material such as nuclear stress tests, bone scans, and PET scans.

Physicians use these tests to help diagnose disease, as well as to make treatment decisions and monitor a patient’s response to therapy. However, recent media reports have suggested that doctors may be overusing these types of tests and exposing patients to unneeded radiation.

We asked Memorial Sloan Kettering medical physicist Lawrence Dauer to explain what you should know about the safety of these scans, how and why doctors use them, and what’s being done to address patients’ concerns.

Do tests like CT scans increase my risk of getting cancer?

Advances in technology and medical physics practice have helped to reduce the dose of radiation that patients receive from tests like CT. However, depending on a patient’s size and imaging needs, the radiation exposure of a CT scan is equivalent to about 100 to 200 chest x-rays. That’s not insignificant.

Risk evaluations currently rely on information from large populations who have received much higher doses of radiation, such as patients undergoing radiation therapy or atomic bomb survivors. This information is extracted and applied to an individual getting a CT, which yields far less radiation exposure and potential risk than those examples.

For the average person, a CT scan is associated with a very small potential risk — perhaps about .05 percent, or about one in 2,000 — of possibly developing a future cancer. If we’re trying to figure out whether you have cancer or how best we should treat an existing cancer, such a small potential risk is far outweighed by the current benefit, which could save your life.

We don't order a test unless it's justified [and] the benefit outweighs the risk.
Lawrence Dauer MSK medical physicist
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How do doctors decide whether this kind of test is necessary?

MSK physicians rely on two fundamental principles to protect patients when it comes to using imaging tests that employ radiation. The first is justification. We don’t order a test unless it’s justified, meaning that the benefit outweighs any associated risk. Once we’ve ordered the test, we implement the second principle, which is optimization — obtaining the best image we can with the lowest dose of radiation in order to reduce any associated potential future risk.

MSK’s collaborative team of oncologists, radiologists, nuclear medicine physicians, medical physicists, and radiation safety staff work hard to ensure you receive the lowest possible amount of radiation exposure from each imaging test without compromising image quality.

We want to give our physicians the very best tools and information to help them make informed diagnostic and treatment recommendations and engage with patients in shared decision-making about their care.

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Can getting too many scans be dangerous?

Not if they are justified and optimized. If those two principles are in place, then the benefit of having the test is going to far outweigh the potential risk. If you have symptoms or an illness, the information that can be obtained from a scan is usually justified. However, if we are talking about using imaging for screening purposes and you have no symptoms, we need to carefully evaluate whether you really need that test.

For example, CT screening for lung cancer has been greatly debated. It’s not right for everyone, so we have to ask, “Are you a smoker? Are you of a certain age?” If you fall into a high-risk category, then we can say that CT screening is a justified and appropriate diagnostic tool for you.

Screening CT renders a much lower dose of radiation compared with the kind of CT scans we use to look at a suspected lung cancer in someone with symptoms or to make treatment decisions. Because those scans require a greater amount of information about the image, the dose is appropriately higher.

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Are certain organs more sensitive to radiation exposure than others?

There are differences in organ sensitivity to radiation. For example, the breasts, thyroid, lungs, and bone marrow are more sensitive to radiation because the cells in those areas divide rapidly. Less-sensitive organs include the brain, where cells don’t divide as quickly.

Our assessments — such as that nominal .05 percent potential risk for a typical CT — factor in this wide range of organ sensitivity. We use mathematical models and other simulation tools to assess where radiation travels in the body and how it interacts with organs in order to get a better picture of dose distribution, measure the risk to the site we are imaging, and reduce the amount of radiation that scatters to areas outside of the area being imaged.

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Are children more sensitive to radiation than adults?

Yes, because their cells divide rapidly. Size and weight also matter when determining the appropriate dose and minimizing radiation scatter to surrounding organs during imaging. When imaging children, we implement child-size protocols to help minimize their overall exposure.

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What is being done to understand and address patient concerns about imaging risks?

Our research has shown that most patients with symptoms want their physicians to help them figure out what’s wrong and choose the best treatment. But once treatment is over, survivors may have more reservations about being scanned and are concerned about whether follow-up imaging might raise their risk of recurrence.

We’ve also learned from national data that a number of patients refuse imaging exams because they are afraid of the risks associated with them.

We want to…engage with patients in shared decision-making about their care.
Lawrence Dauer

We can’t ignore the fact that people feel this way. We need to listen to patients and find better ways to communicate with them about the benefits and risks of imaging at the time of diagnosis and treatment as well as after treatment.

In certain patients it makes sense to check for signs of recurrence with scans. Other patients can be imaged less often, and in many cases, our radiation safety experts push back on physicians to ensure that there is evidence to support a change in a patient’s management based on the imaging tests being ordered. That’s what you need for proper justification.

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Should physicians consider using alternative imaging methods such as ultrasound or MRI?

Yes, we do consider alternatives for certain cases when appropriate. However, not all imaging gives us the same information. We can’t replace all CTs with MRIs for example, but when it makes sense, and it’s justified, we should.

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Comments

Esther - thanks very much for the informative article. Radiation exposure by way of imaging has been a point of contention with many patients who believe physicians are over-ordering scans, etc. It's helpful to know that however real patient's perceptions of exposure are, clinical assessments must be made in order to carry out appropriate treatment and that the clinicians have an obligation to rely on justification and optimization as the fundamental principles when ordering. I'm most certain to continue to advocate that the benefits outweigh the risk.

But wouldn't an MRI be safer?

Dear Anne, MRI does not employ radiation to obtain images of the body, so there is no radiation exposure to a person during that test. As Dr. Dauer explains in the Q&A, we do consider alternative tests like MRI for certain cases when appropriate. However, not all imaging gives us the same information. We can't replace all CTs with MRIs for example, but when it makes sense, and it's justified, we should. Thank you for your comment.

After a distal transverse resection due to diverticulitis do you believe a ct scan poses less risk than a colonoscopy for diagnostic purposes.

Dear Mary, we sent your inquiry to one of our gastroenterologists who responded:

"In general, colonoscopy is safe after colonic surgery. We would recommend that you circle back with your physician who will take into consideration a number of factors -- including your age and other medical conditions -- before making a determination as to which of these tests is most appropriate for you."

If you are interested in making an appointment with one of our experts for a personal consultation, contact our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

I have received numerous scans post whipple surgery. I found this information very informative and answered some of the questions I had regarding the danger of scans. Hopefully, new and less dangerous tests will be developed.

Thank you for the info on this site. I had BC in 2011 and have been on Anastrozole. I have CT scans every 6 months or so to check on my Bronchiestasis. The last scan in October showed that I now have an " ascending aneurysm of the aorta", 4.3 cm. It is being " watched" to see if it gets any bigger. Should I be having all these CT scans? Scary enough to have an aneurysm but now should I have more worry about scans too?

Dear Jeannebnee12, if you have concerns about the CT scans you're receiving, it's best if you speak to your doctor. The benefits of regular scans can outweigh the risks, and your doctor should be able help you understand your specific situation. Wishing you all the best.

I am about to finish radio therapy 35 for level 2 breast cancer an estrogen prone what is the actual % rate of recurrence? I am on Anastrozole for 10 years.

Dear Ana, the rate of recurrence depends on many factors that are unique to you, and we are not able to speculate on what it might be in your particular case. If you have questions, we recommend you speak with your oncologist. Thanks for reaching out to us!

I was diagnosed with non-hodgkins lymphoma 17 years ago. Every year my oncologist orders a CT scan to check the size of my lymph nodes. Never been treated. Are all these scans necessary?

Dear Mary Lou, we are sorry to hear about your diagnosis. We would encourage you to discuss this further with your oncologist, who is familiar with your unique circumstances. Have a conversation with him or her about why he or she thinks having a san every year is important and necessary, and understand the benefits and possible risks of being scanned less often. We encourage this kind of open dialog and shared decision-making about your survivorship care. We wish you all the best. Thank you for your comment.

I was diagnosed with indolent lymphoma almost nine years ago. Fortunately, I have had no problems and have not needed treatment. I have had periodic ct scans, but refused yearly scans due the concerns you mention. My doctor was respectful of my concerns though he didn't necessarily agree. He was accessible and I felt he really watched out for me. Unfortunately, he retired and the last doctor I saw basically said I had to do yearly scans or not bother to return.
I feel abandoned and don't know where to turn.

Dear Sue, we are sorry to hear about your diagnosis and your most recent experience with your physician. If you are not already a Memorial Sloan Kettering patient and would like to make an appointment with one of our specialists, please call our Physician Referral Service at 800-225-2225. We wish you all the best. Thank you for your comment.

you did not mention full mouth x-rays that dental offices insist on taking. this is 18 to 24 films. how can this be necessary if no sign of dental decay and patient has no sign of dental problems.

Dear Greta, every patient's needs are different. Its is important to understand the benefits and risks of these tests and how they may impact your health. We would encourage you to share your concerns with your dentist and discuss whether it's appropriate for you to have x-rays less often. Thank you for your comment.

I had bilateral oncoplasty and lumpectomy on left breast followed by chemo and radiation. I also have a small PFO. While I am a symptomatic and low risk for cardiac problems my cardiologist recommended a nuclear stress test as a baseline. Is the risk worth the gain here?

Dear Lois, we sent your inquiry to MSK medical physicist Dr. Lawrence Dauer and he responded:

"While we can't offer specific medical advice, we can note that nuclear
stress tests use small amounts of radiopharmaceuticals that give radiation
doses about the same as those received from a typical chest CT scan. For
warranted procedures with either x-rays or radiopharmaceuticals, the
benefit of the information obtained from the procedure significantly
outweighs the risk from the radiation exposure. We suggest that you
discuss with your physician their recommendation and justification for the for the baseline nuclear stress test."

Thank you for reaching out to us.

TO MSKCC, I AM A ONGOING PATIENT WITH MELONOMA AT MSKCC, I FINISHED A CLINICAL TRIAL SUCCESSFULLY, MY CAT SCANS ARE NOW EVERY SIX MONTHS, HEAD TO ABDOMEN, RECENTLY I HAD FULL X-RAYS AT MY DENTISTS OFFICE AND DUE TO A SPRAIN TO MY LEFT ANKLE ALSO HAD AN X-RAY AT THE ORTHOPEDIC DOCTORS OFFICE, ALL WITHIN THE COURSE OF JAN-FEB 2015. I DID MENTION TO THESE DOCTORS THAT I WAS HAVING A CAT SCAN ON 25 FEB 15 AT MSKCC. IS THIS TOO MUCH RADIATION AM I PUTTING MYSELF IN DANGER? PLEASE ADVISE THANK YOU FRANK VIGGIANO. PATIENT AND CURRENTLY CANCER FREE.

Dear Frank, it's great to know you're cancer free! We sent your inquiry to MSK medical physicist Dr. Lawrence Dauer, who responded:

"While we can't offer specific medical advice, we note that for warranted
procedures with either x-rays or CT scans, the benefit of the information obtained from the procedure significantly outweighs the risk from the radiation
exposure. We suggest that you continue to discuss with your physicians their recommendation and justifications for each of the imaging tests you are receiving."

Thank you for reaching out to us.

I am a healthy 39 y/o female which has been dealing with a low WBC, swollen lymph node in my right armpit that has not gone away since October of last year, periodic night sweats, fatigue, dizziness, nauseous, loss of appetite. My doctor does not believe there is any thing truly wrong. However I feel generally unwell. I have no active infections and no out word signs or symptoms of an illness.
I need to know what I should do next. I had additional blood work performed and again low WBC, decreased iron binding and saturation levels.

Dear Jennifer, we are sorry to hear that you are not feeling well. Unfortunately, we cannot offer personal medical advice on our blog. We encourage you to go back to your doctor to discuss your concerns, and/or seek out a second opinion with another physician. Thank you for reaching out to us.

I am wondering if MSK is considering getting one of the new 3-D CT machines. I understand that only a few high end centers have them so far. I think Johns Hopkins is the closest one in our area. I believe they emit far less radiation and I know personally that they are super fast even with doing with/without contrast.

Dear Jeanne, we use state-of-art imaging equipment that employs the latest technologies for optimizing diagnostic imaging quality while reducing the dose of ionizing radiation. Thank you for your comment.

I am a breast cancer survivor for 14 years in treatment at Sloan. I really appreciate the care being provided . Yes there are times I have fears that too much exposure maybe harmful for me and have asked if a sonogram would reflect on the progress of the chemo. I am now getting. The cancer is now in the liver. I feel also that teaching could be done with regard as to what we can do to rid our bodies of this radiation once we have been exposed,ie drinking lots of water, fruits and vegs, bowels kept open(natural foods or vitamins to promote elimination,etc) Usually we are told to drink water.

Personally, I wouldn't have an issue with an occasional CT scan if deemed necessary; except for the fact that I was diagnosed with endometrial cancer in my 40's. Treatment after surgery involved chemo once a week, & daily external radiation treatments for 30 days, then 3 treatments of internal radiation.

Of course I'm thankful that 8 years later, I have not had a recurrence of cancer. A different physician who I see for follow-ups repeatedly comments that I had a LOT of radiation during my treatment. Although I do have a few issues which were caused by radiation/scar tissue damage, but overall not too bad.
My question >> how concerned do I need to be if pelvic CT scans are needed, or I've also had several rounds of xrays to diagnose & follow several sacral stress fractures. Because I had radiation treatments for cancer, an I now more susceptible to more radiation damage from simple CT or xray scans ?
And is there anything I can do to protect sensitive areas if I should need a scan ?
Thanking you in advance for a response.

Dear Mari, we are so happy to hear that you are eight years cancer-free!

Concerns such as the ones you describe are common among cancer survivors. Many want to be involved with their physicians in making decisions together around the type and frequency of medical imaging follow-up that they have. Many survivors are often interested in exploring imaging options (such as MRI) that do not involve the use of ionizing radiation. Even so, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks, even when the patient has had multiple prior scans. We would encourage you to discuss the benefits and risks of imaging - as it pertains to your particular circumstances - with your physician. Thank you for reaching out to us.

I recently had a nuclear stress test because of recurring chest and shoulder pain and I needed to have a clearance for surgery. I was able to do the stress portion on the treadmill and I was very upset to find out I could've avoided all the radiation and had an echo stress. My question to you; my level of radiation was 9.4 msv(?) in the Intravenous I was given. In the scheme of things is that a dangerous level and how much would that increase my cancer risk? I worry about the cumulative effect because I have had several full spinal x-rays, numerous ribs chest X-rays and abdominal CT scan. Don't don't want to obsess over this but I just want to know what my risk factors are. thanks

Connie, thank you for reaching out. Your concern is common among cancer survivors. However, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks, even when the patient has had prior x-rays and CT scans. We would encourage you to discuss the benefits and risks of imaging - as it pertains to your particular circumstances - with your physician.

I recently underwent a lot of Radiation exposure due to CT AND PET SCAN , this was done to explore if i had Ca Thyroid , first FNA was false positive as it was taken blindly , second FNA was done in total aseptic conditions ultra sound guided and PET. Also shows nothing , now i am
Concerned abt the amount of radiation i was given and any chances of CA in future please guide and explain ???

Kapil, if you have concerns about the scans you're receiving, we recommend that you speak to your doctor. The benefits of scans can outweigh the risks, and your doctor should be able help you understand your specific situation. Thank you for your comment.

I have been reading up on radiation exposure. You see, I am a 40 yeast old male. Now I have heart issues, and a seizure disorder. With that said, since September till last week I have undergone at least 25 CT scans. Numerous chest x rays. CT scans with some injection to light up my insides.I have had 3 MRI's. That's all in the last 8 months. Although throughout my life I have had even more CT scans of body and head. I guess my question is ; in your estimation, what is opinion, as to how much exposer i have undergone? What are my chance of developing a cancer? I never knew any of these risks. Please enlighten me. I am simply trying to understand things I never knew.

Dear Shane, we are sorry to hear about your health issues.

Concerns about the frequency and type of imaging procedures you've had are common. Many people are often interested in exploring imaging options (such as MRI) that do not involve the use of ionizing radiation. Even so, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks, even when you've had multiple prior scans. We would encourage you to discuss the benefits and risks of imaging - as it pertains to your particular circumstances - with your physician.

You may also be interested in learning more about patient safety and standard doses of radiation exposure for various imaging procedures here: http://www.radiologyinfo.org/en/safety/

Thank you for reaching out to us.

I just have a question. I am a 27 year old female and in the past year I have had a chest, abdomen, and pelvis ct scan. Should I worry about a future cancer due to this?

Concerns about the frequency of CT scans you've had are common. According to our experts, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks. We would encourage you to discuss the benefits and risks of imaging - as it pertains to your particular circumstances - with your physician.

You may also be interested in learning more about patient safety and standard doses of radiation exposure for various imaging procedures here: http://www.radiologyinfo.org/en/safety/

Thank you for reaching out to us.

Hi,my 23 year old daughter has just had 3 CAT scans within a month due to the diagnosis and treatment of a stubborn kidney stone. I am so angry that non of the 3 different doctors told us about the dangers of CAT scan radiation! Is there anything that we can do to minimize the dangers from these scans. I read that vitamin A, C and E could be helpful. Thanks.

Elaine, we recommend that you speak with your daughter's physician before supplementing with any kind of vitamin or other over-the-counter product. Thank you for your comment.

I recently went to the emergenavy room for chest discomfort, three blood fest and three kegs were all negative and yet the doctor ordered a nuclear stress test, after the test I felt ok but about n hour latter my entire body started to feel warm I also felt like I had to vomite, my body felt achy, it as been three days and my body hurts it feels like I'm being cut from the inside not every where just certain spits but my body hurts. Could that be the radiation effect and can it eventually kill me pause its not going away. Was the nuclear stress test ncrceseary for me? I don't know if it was and now I regret having it done acid I came out of that hospital with more pain then I when I went in. Was I over Exposed to radiation? cause I don't think I'm getting better in fact I feel like I'm getting worse.

We're sorry that you had this experience. We recommend that you discuss this with your doctor. Thank you for your comment.

My father has prostate cancer and has been treated with All adds injections for 5 years now. The last 2 yeas have needed to be topped up with Bicalutamide tablets which are now no longer affective. He has been sent to have a CT scan with the intravenous contrast. He is also to have an NM whole body scan also with intravenous contrast within 5 days of the CT scan. He is 89 years old and my father, sister and myself are worried about no gap in between. I know you say the benefits out way the risks and his doctor keeps saying he's had a good run but just because he has had a good run and is 89 years old doesn't mean he doesn't want to fight to stay alive as long as possible. His doctor is wanting to see what treatment is best for him and hence the scans so we understand the need for them, but we (family) are all worried about the gap in between the two higher radiation factor tests.
In the patient advice section on the letters he received stated 2 months gap before any new scan. We would appreciate your independent advice about the recommended 2 months gap and the risks of only a 5 day gap. We have spoken over telephone to doctors Secretary about this and she says doctor doesn't see any risks. But we would appreciate your independent advice regarding a CT scan and Nuclear Medicine scan both with injected radiation and gap between for safety.
Best regards Debbie

Dear Debbie, we are sorry to hear about your father's diagnosis. Concerns about the frequency of scans that use radiation are common. According to our experts, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks. We would encourage you to continue to discuss the benefits and risks of imaging - as it pertains to your father's particular circumstances - directly with his physician.

You may also be interested in learning more about patient safety and standard doses of radiation exposure for various imaging procedures here: http://www.radiologyinfo.org/en/safety/

Thank you for reaching out to us.

I had a CAT scan the end of August 2015 and now am scheduled for a Nuclear Stress Test for the heart. Is this too much radiation? Thanks.

John, we recommend that you discuss this with your healthcare team. Thank you for your comment.

I have CLL and finished my last round of chemo Sept 2014. This year I have had 8 ct scans, 1 Pet scan and a # of x-rays. I also have histoplasmosis and has had problems after problems . My white count dropped to 1 and finally got it up to 3.5. I dont know what to do, my dr doesn't even know what to do o#

Im a healthy non smoking 45 year old woman. 19 months ago I had a CT Scan for abdominal pain. They found a 4mm nodule on my lower left lobe. 7 months later I had a follow up CT done and the nodule looked the same now a year later they want me to do one more lung CT. I'm nervous about radiation exposure and am not sure this test is neeeded. I have also had mammograms and a shoulder exray during this time. I grew up around smokers and smoked when I was a teenager but haven't smoked in 25 years. I am also a hairdresser working with chemicals. Does this make me high risk? Do you think I need another CT? Thanks for your in put.

Dear Susan, concerns about the frequency of CT scans are common. According to our experts, if a medical imaging procedure that uses radiation is clearly indicated and appropriate, its benefits almost always outweigh the risks. For the average person, a CT scan is associated with a very small potential risk of possibly developing a future cancer. If the goal is to figure out whether a person has cancer, for example, such a small potential risk is far outweighed by the current benefit, which could save the person's life.

We would encourage you to go back to your physician and discuss the benefits and risks of imaging - as it pertains to your particular circumstances and medical history.

You may also be interested in learning more about patient safety and standard doses of radiation exposure for various imaging procedures (such as mammograms and x-rays) here: http://www.radiologyinfo.org/en/safety/

Thank you for reaching out to us.

My husband is diagnosed of Kidney cancer early this year and has been on a clinical trial for 3 months. We were informed that from now on the CT scan will be taken every 6 week after one cycle of treatment. While we appreciate of the benefit for having frequent scans, however, we are concerned of the risk involved and wonder if it is justifiable to subject him for such a dangerous radiation on such a short interval.
Your advice is very much appreciated.

Sue, we recommend you discuss your concerns about radiation with your husband's healthcare team. Thank you for your comment.

Last week I had an x-ray because of repeated inner ear and sinus infection. The results indicated possible mastoiditis, and a CT scan was scheduled. I had the CT scan 2 days ago, and my family doctor just called me and apparently the doctor there said I had a deviated septum (yeah, I already knew my nose was broken from years ago), but when my family doctor asked them about the mastoiditis, they said they needed a more detailed scan to look at that. Apparently they did the wrong type of CT scan, despite mastoiditis being written on the referral sheet, and despite my mentioning it to the technician at the time!!! Now I am guessing I have to have another CT scan done since they screwed up the last one. Additional to this, I have had annual chest CT scans for the prior 3 years in a row due to nodes on my lungs, but fortunately they have not enlarged over that time. I also had a CT scan maybe 3 years prior to that (head and chest) for unrelated ailment. So 5 scans so far in as many years (plus multiple x-rays), and it seems I have to have another one within days of the last because these idiots did the wrong type of scan! My question is, will their incompetence increase my risk of cancer, particularly when having detailed CT scans just days apart? Thanks.

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