Medical Imaging and Radiation

Dr. Bhavin JankhariaJankharia Imaging

There is no evidence that low-level radiation from medical imaging

causes harm

1. Amis Stephen. Radiology 2011: 261: 52. Position Statement of the Health Physics Society3. American Association of Physicists in Medicine – position statement. Dec 20114. Hendee William R. Radiology 2012: 264: 312

What is the Issue?

Radiation in high doses, as with accidents, nuclear bombs and with

radiotherapy causes damage

The doses in such cases are upwards of 100 mSV and often

much more

This damage can be non-stochastic (skin burns, exfoliation, loss of hair,

diarrhea, etc), which is dose related….

…or stochastic, which are random events and include DNA mutations,

etc. that can lead to cancer

Medical Imaging

Modalities•X-Ray•Computed Tomography•Mammography•Nuclear Medicine incl PET/CT

Radiation Numbers

Normal•Normal background - 3 mSv / year (chest x-ray is 0.1 mSv and chest CT scan is 5-7 mSv).•The average per person radiation in the US because of medical imaging has now gone up to around 6 mSv / year, much less in India.

Radiation Numbers

Normal•Essentially, normally any person will receive up to 50 mSv of radiation in the first 17 years and then up to 250 mSv till age 80.

Below 50-100 mSv of exposure, the risks of health effects are either too

small to be observed or non-existent

Position Statement of the Health Physics Society

Risks of medical imaging at patient doses below 50 mSV for single procedures or 100 mSv for multiple

procedures over short time periods are too low to be detectable and may be nonexistent.

Position Statement of the American Association of Physicists in Medicine, Dec 2011

So, what is all the fuss about?

The BEIR VII Report

www.nap.edu

Based on Japanese bomb survivor data, risks have been extrapolated

Radiation Numbers

Risk•0.7 to 2.0 % of all cancers are supposed to be due to low level radiation

These extrapolations have often led to sensationalistic reports in the media

Based on the CT scans done in 2007, the National Cancer Institute projects 29,000 excess cancers…

http://www.npr.org/templates/story/story.php?storyId=121436092

In perspective...

http://www.npr.org/templates/story/story.php?storyId=121436092

The total number of new cancers per year is around 1.6 million in the US. The lifetime risk of getting any kind of cancer is 1 in 2 to 1 in 3

http://www.cancer.org/acs/groups/content/@epidemiologysurveilance/documents/document/acspc-031941.pdf

So unfortunately, this often causes more harm than good because some patients

and guardians refuse life-saving or required medical imaging procedures

based on these media reports

One New Twist…

Radiation Risk

Retrospective Study•180,000 patients underwent 280,000 CT scans below 22 years of age•The estimate is that one head CT scan performed in the first decade of life would produce one excess case of brain tumor and one excess case of leukemia per 10,000 patients who underwent CT scan, in the first decade after exposure

Pearce M et al. Lancet. Published online, June 7, 2012

It is known that children are particularly more susceptible to radiation and there is no question that the radiation dose used should be as low as possible. The risk however is small and as long

as the study is justified, not really relevant.

And while the study’s data and conclusions have not been particularly challenged, in

the end, this is a retrospective study. What is required are prospective studies that

address this issue.

Age Matters

What do you tell a 60 years old man concerned with the ill-effects of radiation?

Radiation Numbers

Risk•0.7 to 2.0 % of all cancers are supposed to be due to low level radiation•In the elderly the risk of cancer from radiation is less than 0.04%

Cumulative Dose and Multiple Tests

Two 35 years old men with suspected acute appendicitis need CT scans. One is a radiation virgin, the other has had 20 CT abdomen pelvis studies for treated testicular cancer in the last 10 years with a cumulative dose of 180 mSv

Eisenberg et al. Radiology 2012; 263: 626

Radiation Risk

Sunk Cost Effect and Cumulative Dose Issues•The risk from radiation is stochastic and hence is a one-time risk related to that particular test. •Cumulative dose is irrelevant. •The risk therefore for both patients is the same.

Eisenberg et al. Radiology 2012; 263: 626

But, going with the assumption that we should use radiation wisely…

...the radiology community has taken significant steps to reduce radiation...

...on the principles of…

ALARA (Keeping Radiation Dose As Low As Reasonably Achievable)

ASARA (Keeping Medical Procedures as Safe as Reasonably Achievable)

AHARA (Keeping Medical Benefits as High as Reasonably Achievable)

Radiation Control

Stakeholders•Vendors•Radiologists and other health workers•Regulatory authorities

Radiation Control

Vendors•Radiation reduction technology•Protocols that use less radiation

Radiation Control

Radiologists and other health workers•Optimal use of investigations•Using non x-ray based techniques wherever feasible•Using protocols with the lowest radiation possible that still allows accurate diagnosis

Radiation Control

Regulatory Authorities•Monitoring proper use•Accrediting only appropriate personnel

Image Gently

www.imagegently.org

Step Lightly

Conclusion

Summary•There is increasing exposure to low level radiation from medical imaging•While there is little hard evidence that this is harmful to people, there is concern based on extrapolated data from Japanese bomb explosion survivors•All stakeholders are working hard to reduce radiation exposure

Thank You