Annual screening for lung cancer low-dose CT

This is a major advance as American healthcare evolves from reactive to preventive.

But a key to success in this lung cancer screening program is keeping the radiation dose of each exam as low as possible – certainly well below one mSv. Ideally, a low dose approach would involve model based or some other form of iterative reconstruction. All the other techniques to minimize dose should be employed together. Fortunately, this is an application where very low kVp will work well (70-100).

Next – and possibly even more impactful: coverage for screening CT colonography.

CT radiation dose reduction by iterative reconstruction in lymphoma staging

There are some who say that iterative reconstruction should be reserved only for younger patients and not used on older cancer patients who already have serious disease.

But many patients with malignancies are younger or are being treated for cure.

This article suggests that an iterative reconstruction technique (such as model-based iterative reconstruction, MBIR) which can reduce patient radiation dose by 50% may have salubrious utility in patients with lymphomas – who often are younger, who get multiple CT scans, and who are being treated for cure.  

This may apply to other malignancies as well.

Lung Cancer Screening in High Risk Patients

For the question of whether lung cancer screening in high risk patients causes more good than harm, check out this article.

I’m pretty convinced the data shows that in a research study high risk population where the scans are read by highly skilled experts closely following the rules, lives are saved by CT screening and the cost is reasonable for each QUALY.

Further, the interpretation of these chest CT screening exams is fairly straightforward for experienced and trained radiologists. That suggests that when CT screening is extended beyond research to broader community practice, results should also be good.

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.

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.

Patient Resource: Radiation Risk Calculator

Here on this blog I often talk about the importance of patient education and awareness, as it relates to CT scans, radiation dose and cancer risks. Informed patients are smart patients! To that end, I wanted to share with you an interesting resource I recently came across: a “radiation risk calculator” sponsored by the American Society of Radiologic Technologists.

According to the site, the purpose of this (free) tool is to “calculate your dose and estimate cancer risk from studies including CT scans, x-rays, nuclear scans and interventional procedures.” I think this is good for patients, if combined with counseling about the meaning of the numbers.

I always say: the more info, the better – as long as it is understood appropriately. Remember too, that a 1 in 2000 risk of causing cancer means a 1999 in 2000 risk of not causing cancer…

The Thyroid Shield Controversy: Cancer Fears Overblown

Recently, an episode of Dr. Oz that linked the increase in thyroid cancer to imaging and biopsy procedures prompted an increase in requests for thyroid shields from women undergoing mammograms. The cancer risk scare appears to be caused by a chain e-mail that was created by a viewer after the episode aired. The public outcry has reached the point that the American College of Radiology and the Society of Breast Imaging have issued a joint statement to try to overcome fears of high radiation risk from mammography.

Here in our own offices, we have women showing up for mammograms bringing their own thyroid shields. This is silly – the amount of scatter radiation is so small as to be hardly measurable with very sensitive instruments.

If you take a thyroid shield to a mammogram, to be logically consistent, you should be wearing it all the time – on any airplane flight, when sunbathing… the list goes on!

Virtual Colonoscopy on the Rise

A new study published in the March issue of the Journal of the American College of Radiology shows that the use of virtual colonoscopies at U.S. hospitals is increasing – even though the procedure is not covered by Medicare.

A neat feat of virtual colonoscopy is how the radiation dose associated with the exam has dropped considerably since it was introduced. Newer reconstruction techniques on newer CT scanners have made this possible.

While it is still true that Medicare will not pay for any type of screening (except mammography), some commercial insurance companies have realized the value of screening for colon cancer, particularly in high-risk patients. Screen CT colonography does well when compared to other tests for detecting colon tumors and polyps. And patient acceptance is higher because it is quick and less uncomfortable.

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?

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.

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.

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.