Radiation Dose Pearls - Learning

Radiation Dose

The Informed Patient

“ However, estimation of the risk of cancer from radiation doses associated with standard CT examinations requires certain assumptions (e.g. linear no threshold model) that may not be correct. To date, there is no scientific evidence showing a causitive relationship between CT radiation dose and cancer risk.”
Body CT: Technical Advances for Improving Safety
Marin D et al.
AJR 2011; 197:33-41
“ Although CT is a powerful tool that has transformed the practice of medicine, the benefits are accompanied by important risks. Radiologists must understand these risks and the strategies available to minimize them as well as the risks associated with contrast medium delivery in abdominal CT.”
Body CT: Technical Advances for Improving Safety
Marin D et al.
AJR 2011; 197:33-41

Sample Visual Aid Chart for Use When Discussing Radiation Imaging Procedures

Imaging Examples	Effective Dose Range (msv)	Background Equivalent radiation Time	Radiation Risk Descriptor	Probability of Cancer from Imaging (%)	Probability of No Cancer From Imaging (5)
CT scan	1-10	years	minor	0.05	99.95
Abdominal Radiograph	0.1-1.0	months	minimal	0.005	99.995
Chest X-ray or Mammogram	<0.1-0.1	Days to weeks	negligible	0.0005	99.9995

AJR 2011;196:756-761 (modified)

Typical Comparison Approaches for Communicating Medical Radiation Risk

Comparison	Chest radiographs (0.1 mSv)	CT of the Abdomen (<10 mSv)
Equivalent to how many CXRs	1	100
Background equivalent radiation time US	12d	3.3y
Background equivalent radiation time Colorado	9d	2.5y
Number of flights NYC to Seattle	3.6	360
Fraction of occupational dose limit (50 mSv/y)	0.002	0.2

AJR 2011;196:756-761

"The risk associated with a radiologic examination appears to be rather low compared with the natural risk. However, any added risk, no matter how small, is unacceptable if it does not benefit the patient."

Radiation Risk: What You Should Know to Tell your Patient
Verdun FR et al.
RadioGraphics 2008:28:1807-1816
"A small proportion (1.9%) of emergency department patients undergoing CT of the neck, chest, abdomen, or pelvis have high cumlative rates of multiple or repeat imaging. Collectively, this patient subgroup may have a heightened risk of developing cancer from cumulative radiation exposure."

Cumulative Radiation Exposure and Cancer Risk Estimates in Emergency Department Patients Undergoing Repeat ot Multiple CT
Griffey RT, Sodickson A
AJR 2009; 192:887-892