Decreasing radiation dose in CT for COPD patients

Study concludes that ultralow-dose CT may substitute for standard-dose CT in some COPD patients

There are at least three different generations of iterative reconstruction, all of which enable substantial CT dose reductions without compromise of diagnostic power. While earlier versions of IR yielded 30% dose reductions, those with model-based IR or some blend thereof can result in 50-80% patient radiation dose reductions – with even better spatial and low contrast resolution. Access the full article on this study.

Radiation protection shielding

This article outlines the substantial reduction in radiation exposure to body parts which are shielded during a CT scan but not included in the field of imaging.

That is a very good practice.

More controversial is another practice: shielding sensitive body parts which ARE included in the field of imaging, specifically breasts, thyroid and gonads.

For some types of scanners this works well, while for other types less well.

With our scanners (GE) IF shielding to the sensitive body part is applied after the scout views are obtained, and IF the shield is separated from the body by placing towels or a blanket to elevate the shield off the body by 2-3 cm – then this works well. Any artifacts or other issues with image quality are minimal or out of the area of interest and the dose to the shielded body part does drop measurably.

Further, such shielding sends a strong message to patients and to our own staff about our concern for their safety.

Best Way to Reduce CT Radiation Dose in Children? No Unnecessary Testing

A University of Washington study featured in the August issue of JAMA Pediatrics claims that 4 million annual pediatric CT scans of the head, spine, abdomen and pelvis are predicted to cause nearly 5,000 future cancers, according to HealthImaging.com. However, the study goes on to state that the risk can be mitigated by CT dose reduction and appropriate imaging initiatives which have the potential to prevent more than half of the projected radiation-related cancers. Practices like eliminating unnecessary scans and targeting high-dose scans are called out in the study.

I believe that the best way to reduce radiation dose from CT in children is to not do studies which are inappropriate or which have a very low chance of producing impactful diagnostic information. The next best way to reduce dose is to pay close attention to all the tricks of technique: accurate patient centering in the gantry, use of radiation shields, use of 80 or 100 kVp, minimizing Z axis scan length, etc. Then newer technology will greatly further reduce dose – automated tube current modulation, iterative reconstruction – especially fully model-based iterative reconstruction. Together these can reduce radiation dose by 70-80 percent. Scanning in kids above 6-8 mSv should be a thing of the past and sub-1.0 mSv scans should be common.

CT Scans and Children–Consider the Risk/ Benefit Ratio

A new pediatric imaging study has been making headlines, but it’s important for patients to keep in mind both the risks and benefits of CT scans when evaluating the research. The study, published this week in Lancet, a British medical journal, claims that CT scans expose children to cancer causing radiation.

According to the researchers, for every 10,000 CT scans performed on children under the age of 10, one additional child will get a brain tumor and another child will get leukemia within 10 years of the initial scan. The research claims that these cancers would not have otherwise been expected regardless of medical imaging exams.

However, this article documents an extremely small risk. In fact, this figure is less than what we have been assuming historically prior to any evidence. But, the article also cautions that any decision on whether or not to scan should involve a risk/ benefit ratio consideration. The study does not change our assessment of risk in that ratio. Thus, the potential benefit from CT remains the critical determinant on whether to perform a scan.

As always, the ACR appropriateness guidelines help with that assessment. That also is the role of trained Board Certified radiologists—to know and advise about when CT scanning creates a risk/ benefit ratio strongly in a patient’s favor.

Remember parents, discussing the risks of CT with your health care provider should certainly be done, but be sure to get the full set of facts before refusing care that may save and extend a child’s life.

New Data on Lung Cancer Screening Shows Low Dose CT Saves Lives

Earlier this year, I wrote a blog entry about the news surrounding an important study involving CT and lung cancer screening. Now, the same study is making big headlines again as stronger (final) findings have been released. According to CNN, the study found that “low-dose CT screening reduces the number of lung cancer deaths in high risk smokers by 20 percent.”

Here’s another interesting fact coming out of the latest data: In high-risk populations, lung cancer CT screening can save a life for every 300 people screened. That’s more potential lives saved than mammography, colonography and prostate cancer screening COMBINED!

The only hitch: lung cancer CT screening is not covered by most insurance. However, many hospitals and imaging centers are offering this service at attractive rates for those who are willing to pay themselves.

An Interview with Dr. Mitsumori on Weight-based Selection of CT Parameters

The following is an interview I conducted with Dr. Lee Mitsumori, Assistant Professor of Radiology at the University of Washington.

Dr. Shuman: Please give us a brief overview of your work involving weight-based selection of CT parameters.

Dr. Mitsumori: We have been investigating the use of body-size-dependent CT scan parameters to optimize the radiation dose of each scan. Several imaging parameters can be modified at the time of the CT that can alter the amount of radiation of the scan (tube current, tube potential, scan range, scan phases, image reconstruction techniques). The challenge is to adjust each so that the final set of patient images are of diagnostic image quality and were obtained with the lowest possible radiation dose. The risk is that incorrect settings or too aggressive dose reduction can create a scan that is of poor image quality that does not allow a correct interpretation. Current work at University of Washington Medical Center involves studies comparing different CT image reconstruction techniques (adaptive iterative reconstruction, model based iterative reconstruction) that can significantly reduce CT image noise and how these can be best implemented in patient CT exams.

Dr. Shuman: Why is weight an important concern regarding CT? How does weight affect CT?

Dr. Mitsumori: A patient’s body size, as reflected by weight, affects two important feature of a CT scan. The first is the amount of photons needed to generate an interpretable CT image. A CT is a projection technique, where an x-ray source emits photons that then pass through the subject before being recorded by a detector on the other side of the patient. Larger patients need more photons with higher energy than smaller patients to create images that can be correctly interpreted. If the CT parameters are not correctly set and only a small number of photons are recorded by the detector, the images created are noisy. If an image is too noisy, the interpreting physician may not be able to see if a problem or disease process is present. Unfortunately, the more photons used the higher the radiation exposure of the CT exam. While large patients are at risk for having noisy images, small patients can have scans done with parameters selected for an average sized patient, in which case too many photons are used than what would be needed to create diagnostic images. Thus, the importance of matching the radiation dose (number and energy of photons emitted) with the patient’s body size to prevent non-interpretable studies in larger patients, and avoid excessive radiation dose in the smaller patient.

The second feature of a CT scan where patient size is important is in the amount of iodinated contrast needed for the scan. Iodinated CT contrast is injected intravenously during the scan and improves the depiction of the different organs and vascular structures in the body. With CT imaging, the use of contrast greatly improves the radiologist’s ability to differentiate diseased (tumors, infection, inflammation) from normal tissues. Similar to radiation dose, the amount of contrast needed to enhance the organs is dependent upon patient body size. Small patients will have smaller organs, less blood volume, and be shorter than larger patients. Thus the amount of CT contrast needed may not be the same for every patient.

Dr. Shuman: What are the risks involved when a hospital or imaging center does NOT take a patient’s weight into account?

Dr. Mitsumori: The risks for scanning with fixed CT parameters are that when compared to an average sized patient, the large patient may have scans with noisy CT images that could lead to interpretation errors, or a non-diagnostic scan in which the scan may need to be repeated or an alternative imaging test performed. For the smaller patient, the risk would be that more radiation is used than what is needed to generate adequate, diagnostic images.

Similar risks occur with CT contrast administration. If a fixed amount of contrast is used for every scan that is based on an “average” patient size, then large patients may not receive enough contrast to adequately enhance the internal organs rendering the scan potentially non-diagnostic, and the small patients are given more than the amount of contrast needed to obtain an adequate scan.

Dr. Shuman: When discussing CT exams with their doctors, are there questions a patient should ask regarding their weight? In other words, what would make an “informed patient” as it relates to weight and CT?

Dr. Mitsumori: An informed patient would want to ask if their CT scans will be performed with “patient tailored” or “patient specific” protocols that use the amount of radiation and iodinated contrast that best match the patient’s body size.

Thoughts on Radiation Exposure, Risk

A New York Times op-ed about nuclear radiation exposure, called “Unsafe at Any Dose,” got me thinking about CT scan radiation exposure – and the ongoing debate regarding CT scan risks.

Many activities and endeavors in human life have associated risk. Driving a car is risky; people die. And the more miles you drive, the greater the risk. But that does not mean we don’t use cars. Rather, we minimize risk by driving carefully, using seatbelts, etc. And we go ahead and drive in order to capture the benefits.

So it is with medical radiation… and nuclear energy. But an important note: even with Dr. Caldicott’s pessimistic predictions and numbers, if you look at human deaths associated with kilowatt hours of electrical generation, coal powered electricity is the worst. Oil is next, and nuclear is at the vary bottom of the list (i.e., it has historically caused the fewest deaths).

Makes one stop and think, doesn’t it?

Important Studies on CT Scans and Lung Cancer Make Headlines, Generate Debate

In the last few months I’ve read several stories concerning research about CT screenings for lung cancer.

In mid-November, there was a story making the rounds among the major news outlets about a study that found that CT lung scans can reduce the risk of lung cancer death among former and current heavy smokers. During the excitement of this study, a New York Times piece was published that expressed concern that the study’s findings could easily be taken out of context – and perhaps incite unnecessary fear, as well as drive demand for unnecessary scans.

I’d like to point out the importance of this study: it showed a 20 percent reduction in mortality in patients at very high-risk who were screened with low dose CT compared to patients who were not. Several things to keep in mind about this study – first, it was a study of patients with 30 or more pack-years of smoking history. Second, the technique was a quick and a low dose CT. And third, the costs of false positive findings and their workup have not yet been analyzed.

Now, another study is gaining traction that provides even more support for the findings of the November study. While this data suggests that screening can lower lung cancer mortality substantially in high-risk individuals, what we don’t yet know is the cost of a QUALY – a quality adjusted life-year. Calculating that cost involves knowing how much society had to expend paying for CT exams and the costs of false-positive results in order to capture a saved life-year in an at-risk person. Generally, if you can save a QUALY for $50,000 or less, it’s worth doing. If more, it’s a debate.

Just some things I’ve been thinking about as more and more news agencies report on these findings. I’m interested in learning what you think – what’s your opinion on these studies? Was the New York Times piece correct in its cautionary tone? Or could these findings, in fact, be as revolutionary as some reporters (and researchers) want us to believe?

Obligation to Patients: Minimize Risk and Maximize Benefit

One of the most exciting – and talked about – sessions at RSNA was called “Radiation Dose: Can It Be Too Low?” The expert panel had a healthy debate on radiation dose and risk, and finally reached an agreement that CT scans should be limited to “justified and optimized studies.” (HealthImaging.com has a good recap of the panel’s discussion.)

The debate about risk can go on, but when practicing medicine (radiology) with real patients, the obligation is to both minimize risk AND maximize benefit.

So the challenge for radiologists is to lower dose as much as possible without compromising the amazing diagnostic power of CT. How to accomplish this is both science and art. But we have discovered at UW that with a combination of low dose technique and low dose CT technology, you can take out up to 40 percent of the radiation dose to the patient (compared to 3 years ago) without having any negative impact on diagnosis. So that number certainly is achievable at most sites.

Could we go even further in dose reduction?

Stay tuned…

Educating Patients About Radiation Risk Not Always Easy

Lots of articles are published on a regular basis that talk about public awareness (or lack thereof) of CT scan risks and benefits. This one’s a recent example. But here’s the thing, which I’ve discovered through personal experience: educating patients about radiation risk is very challenging. This is because extremely low rates of risk are hard to comprehend. It can be talked about in terms of background natural radiation, or risk of driving a car, for example. While it is important that patients be informed, it is also important that they not be scared away from a test that stands a good chance of helping them – a lot. This is a fine balance.

Practicing medicine in an emergency room environment is different from in a clinic or a hospital. The diseases are different as is the acuity. What may not be appropriate in a family medicine clinic population may be appropriate in an acutely ill ER patient.

This is why specialists in radiology and emergency medicine are continually reviewing appropriateness criteria, like those published by the American College of Radiology.

Patients Want To Know About Radiation Risks

A new study published in the November issue of the American Journal of Roentgenology concluded that patients from the emergency department are more concerned about having their condition diagnosed with CT than about the risk of future cancer from radiation exposure.

Although the patients in this study did not estimate the risk of development of cancer as high, the majority of patients wanted someone to discuss the risk and benefits of testing them. This is not as simple as it sounds. How do we best educate patients about radiation? Who is responsible for educating patients about risks and benefits of radiation exposure from CT – the ordering provider, the radiologist, or the CT technologist?

Right now it seems that nobody is doing such education likely due to time constraints and the fact that it is a difficult topic to discuss.  There is no standardized way to discuss radiation with patients and research shows that many physicians don’t fully understand radiation, radiation doses from common tests or possible risks from exposure to radiation from medical imaging. This is a topic that is not going away. We know what our patients want and need, it’s up to us as their healthcare providers to deliver.

Communication Networks Help Avoid Repeat CT Scans

Aunt Minnie recently reported on a study that found that when emergency room personnel are knowledgeable about protocols for transferring and accepting DICOM CDs – which contain images of emergency CT scans of injured children – there is a decrease in the number of repeat (unnecessary) exams performed.

However, the authors of the study said that problems arise when CDs aren’t transferred to the appropriate personnel, leading to unnecessary exams (and unnecessary radiation exposure) even when a CD exists, according to the article.

Another approach – one which we follow – is to set up pre-existing VPN communication networks so studies can be directly downloaded (quickly), without the need for CDs. These often arrive before the transfer of the patient. They are set up with the sites that refer more than 5 patients per year. Here we have about 200 such connections to other healthcare facilities, which is great for all medical records as well as the images from radiology.

Upcoming CT Speaking Engagements

I’ve got two events coming up I’d like to share…

The first, on November 4, is the Grand Rounds conference at Overlake Hospital. The conference will focus on radiation exposure and its potential risks with regard to patients receiving multiple imaging studies/multiple radiation doses. Should be interesting!

The second, on November 6, is the Washington State Radiological Society (WSRS) annual meeting. It’s at the World Trade Center in Seattle, and it’s scheduled for 4:00 p.m. Click here for more information about this meeting. If you’d like to attend, you can find the registration form available for download here.

November’s off to a busy start!

CT Scans CAN Be Cost Effective (and Save Lives) in Emergency Situations

A recent study found that the use of CT scanners and other advanced imaging machines in U.S. hospital emergency departments “tripled between 1998 and 2007, resulting in higher costs and longer emergency room stays,” according to an article by blogger Julie Steenhuysen.

Lead researcher Dr. Frederick Korley of Johns Hopkins Medicine in Baltimore said his team noticed “a really significant increase [in usage] without a corresponding increase in the diagnosis of life-threatening illness.” He said this suggest that there is a “potential amount of overuse or use that is not directly yielding any meaningful clinical results.”

Actually, the use of all CT and MR from any source more than doubled during that time period.

Emergency rooms are under great pressure to diagnose or rule out serious conditions quickly, since every ER in the country is swamped with patients – many of whom cannot get to other forms of care. What is inappropriate in some settings may be appropriate in the ER setting.

In our study of patients with low-risk chest pain who had a cardiac CT early in their ER visit, patients were discharged 20 hours faster and with a 40 percent cost reduction compared to similar patients who had a workup without cardiac CT.

So it really depends on the indication.

Study Published in American Journal of Roentgenology

The October issue of the American Journal of Roentgenology has just been released, and it features a recent study I conducted with blog contributor Janet Busey and colleagues Kelley Branch, Lee Mitsumori, Jared Strote, Douglas Green and James Caldwell.

The study, “Negative ECG-Gated Cardiac CT in Patients with Low-to-Moderate Risk Chest Pain in the Emergency Department: 1-Year Follow-Up,” shows that for patients with low-to-moderate risk chest pain evaluated in the emergency department, adverse cardiac events may be rare during the year after a negative cardiac CTA scan.

To read the study, click here (a subscription is needed to read the full article, though you can view the abstract for free).

ACR Guidelines Still Best Resource for Determining Appropriateness of CT Imaging

William R. Hendee, Medical College of Wisconsin, makes some very valid points in a recent article about overuse of CT scans and the harmful effects unnecessary exams have on both patients and the healthcare industry. Specifically, he says that radiologists can “play a big role in educating ordering physicians about what scans are appropriate and when.”

A big part of the training and experience-based learning of radiologists is what imaging tests are appropriate for specific healthcare problems and what imaging tests are inappropriate. Inappropriate means the imaging test has little chance of adding significant value to the diagnosis and therapy of the patient, especially relative to its cost.

The American College of Radiology (ACR) has spent more than a decade developing imaging appropriateness guidelines for hundreds of clinical problems and indications. These ACR appropriateness guidelines are based on the best available scientific evidence and were written by panels of best sub-specialized experts. The guidelines each get revised every three to five years as new evidence becomes available. There is no better source available for appropriateness of diagnostic imaging.

The decision support computer programs mentioned in the article start with the ACR appropriateness guidelines and create a quick way for referring physicians to know if any imaging test they order is appropriate. At the point of computerized imaging exam order entry into an electronic system, the decision support examines the entered indications for an imaging exam and then either agrees with doing the exam, or cautions that the exam may be only marginally indicated – or states that by generally accepted criteria the requested exam is unindicated. There is education involved, as the evidence-based reasons an exam is unindicated are provided to the ordering physician, along with suggestions for a better approach to the patient’s problem (often involving some other type of imaging). These decision support programs are now running in several healthcare enterprises, and they hold good hope for decreasing inappropriate complex imaging exam utilization without blocking access to appropriate tests.

CT Perfusion Dose – What is all the Hue and Cry About?

Last year a New York Times investigation uncovered more than 200 radiation overdose cases at Cedars-Sinai Medical Center. According to a New York Times follow-up published on July 31 this year, 200 additional cases were revealed at other hospitals leading to more than 400 cases nationwide. The radiation overdose delivered to patients in these overdose cases was between 4 to 13 times higher than a typical dose for the performed scans. These overdoses led patients to experience hair loss, headaches, confusion, and may increase their long-term risk of cancer and possible eye and brain damage. The patients had received CT brain perfusion exams, which help to identify strokes through a number of blood flow images.

Why did these overdoses happen?  This could be due to equipment malfunction, the need for “prettier” clinical images (requiring high radiation dose), or a serious lack of operator knowledge in setting up the CT imaging protocols for this type of exam. CT brain perfusion is a high-dose exam but can be performed safely if the technologists, physicists and radiologists work diligently together to ensure that the CT imaging protocols are set up optimally to follow the As Low As Reasonably Achievable (ALARA) principle. The dose delivered by this exam should also be monitored on a regular basis to ensure it remains at minimal levels and no equipment malfunction or dose creep has occurred.  Physicians should also be aware of the potential side effects, as discussed above, which can be triggered by such high-dose exams.

Following 2009’s overdose discoveries, the FDA launched a collaborative Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging, to promote the safe use of medical imaging devices, support informed clinical decision making, increase patient awareness, and optimize patient exposure to radiation.

At the recent American Association of Physicists in Medicine (AAPM) annual meeting, the patient safety symposium focused on these overdose cases and the AAPM CT dose summit’s recent efforts to ensure CT scan parameter optimization and patient safety.  The AAPM also produces reports on quality and safety in medical imaging and radiotherapy, along with letter-writing and policy campaigns targeted at the government and public.

Researchers at Mayo Clinic are also investigating the use of new image-processing algorithms to reduce the dose for CT perfusion exams up to 95 percent and maintain the same image quality as a high-dose perfusion exam.

If appropriate steps are taken to ensure patient safety and dose optimization, the benefits from a CT brain perfusion scan far outweigh the risks associated with it.

Debating the Cumulative Radiation Dose Theory

Despite the attention being given to the cumulative CT scan radiation effect and the buzz surrounding risks of repeat CT scans, one leading expert is disputing the theory.

As reported in Diagnostic Imaging, Richard Morin, Ph.D, chair of the American College of Radiology’s safety committee says, “There is no radiation biology to demonstrate CTs are additive in any way.”

Morin uses a driving analogy that relates probability of an accident to the number of miles logged by a driver, but notes that there is not a certain mile threshold, like 200 miles, that would trigger an accident.

I like the driving analogy and used it in my recent post Measuring Risk: Driving vs. CT. Driving is something that most of us can relate to, and therefore the numbers are more meaningful, so I’ve tried to quantify it even further.

Here’s how I like to look at the risk: The risk of dying from a cancer induced from a CT of the abdomen and pelvis in a middle aged male is similar to the risk of dying in a car accident if you drive 36,000 miles – both are about one in 2000.

The debates over cumulative dose theory will continue, and so I feel it’s important to explain the risks in ways people can understand – so that they don’t turn down any life-saving exams out of fear or misunderstandings.

While Dr. Morin explains that there is no way to figure out whether a person developed cancer due to radiation, a carcinogen or chance, he does say “it’s important that the right test is ordered at the right time.”  I’ll add that it’s always a good idea to look at lowering the CT dose, too.

And while the effect of cumulative dose from multiple exams is unproven, we really must take the most conservative position when it comes to public health and assume the effect is cumulative.

Low Dose CT for Cardiac Imaging

Findings of a recent population-based study featured in the Journal of American College of Cardiology (JAAC) suggest cardiac imaging may be putting younger adults at risk due to radiation exposure.

“The study demonstrated that there are sizable rates of radiation exposure for patients 35-54 years, many of whom will likely live long enough for such long-term complications (as malignancy) to potentially develop,” wrote Jersey Chen, MD.

While the results may make cardiologists give further thought to the tests they recommend and alternatives they can use, others point out that the benefits of the test must be weighed against the risks of radiation exposure.

It is very unusual for a patient in this age range to get a cardiac CT scan. But if they do need one, we can now scan them using less than 2 mSv of radiation (compared to 10-25 mSv in 2005).

That means the risk of dying from a cancer induced by the CT scan (1 in 4,000) is about the same as the risk of dying in a car accident if they were to drive 70,000 miles (about 5 years of driving for the average American) which is also about 1 in 4,000.

Is Treatment Necessary? Ask a Radiologist.

In a recent New York Times article, Dr. Peter Libby, chief of cardiovascular medicine at the Brigham and Women’s Hospital in Boston, discusses the benefits versus the risks and costs of medical procedures like CT scans. In particular, he addresses the issue of incidentalomas, which occur when “medical scans pick up incidental findings that may be benign, leading to complications that make an otherwise healthy person ill.”

Dr. Libby writes, “While contemporary imaging modalities offer powerful and much needed tools for diagnosis and management when appropriately deployed, we should bear in mind the potential risks they entail if used indiscriminately.”

The problems created by incidentalomas is one area where you really need an expert: your radiologist.

This is what radiologists do – they don’t merely detect findings on CT scans, but also attach significance (or insignificance) to each finding.

When all your training and all your experience is in CT scans and their findings, you become pretty good at telling incidentalomas from true problems which need more investigation. Not perfect, of course, but pretty darn good.

Measuring Risk: Driving vs. CT

In the past couple weeks there has been much talk about the cancer risk from medical radiation. According to a recent Reuters article, one chest CT scan delivers the same radiation (and risk) as 100 chest X-rays. However, these numbers still do not communicate the bigger picture: CT cancer risk can be more clearly explained.

Since most people never get close to getting 100 chest X-rays, we need to find a more common point of comparison. Driving, however, is something most North Americans do on a regular basis, and its risks are well-publicized.

43,000 people died in 2007 from car accidents in the U.S. During that same year, U.S. drivers drove 3 trillion miles, according to the U.S. Census Bureau. Based on these statistics, the risk of dying from driving 35,000 miles is about 1 in 2000 (0.05%).

An abdominal/pelvic CT scan delivers about 15 milliSieverts of radiation. In our calculations, using the most conservative data from the atomic bombings of Hiroshima and Nagasaki and the Chernobyl disaster, the risk of mortality from radiation-induced cancer is also about 1 in 2000 (0.05%).

Published data also supports this risk level: Brenner and Hall have estimated that the total lifetime attributable risk of death from cancer after receiving an abdominal CT with 240 mAs, is in the 0.06%-0.07% range (this estimate is for ages 15-25; CT risk drops radically after age 25).

Thus: If the average U.S. driver travels just under 14,000 miles per year… then the risk of dying in car accident (if only driving for 2 years, or 35,000 miles) is about the same as the lifetime risk of dying from cancer induced by the radiation in a CT of the abdomen and pelvis.

Of course, driving more carefully and lowering the CT dose per scan both are good ideas.

Discussing the Benefits of Low Dose CT Scans

Radiation is part of nature. We’re all exposed to radiation every day in very small amounts. But the amount of radiation being used for medical diagnosis has been increasing over the last 20 years or so – to a point where it is now raising new concerns about CT scan risks. In fact, the use of CT has increased over the last decade to the point where we’re now doing around 60 million CT scans a year in the United States.

So what does this mean for patients?

What other options are available to minimize the effects of CT scans?

How can patients go about trying to make smart decisions about the risks and benefits of CT scans?

Last October, I took part in a Webinar for Patient Power with medical physicist Dr. Kalpana Kanal that addresses these questions and more – touching on radiation dosage and risk, new technologies, and techniques for limiting exposure.

>watch the webinar