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While there are a multitude of administrative challenges facing computed tomography (CT) facilities in today's medical arena (i.e., decreasing reimbursements, staffing issues, rising costs, etc.), none of these issues are as important as providing a safe environment for patients undergoing a CT examination.

As the technology and application of CT imaging have increased dramatically in the past ten years, the public is becoming more astute in terms of realizing that there are issues that they, as patients, should be aware of when it comes to radiation-based testing. Mainstream media often chooses to bring this topic to the attention of its audience, as illustrated by an article entitled, "Are Medical Tests A Hazard?", published in the May 2008 issue of Ladies Home Journal. Within the article, patients are encouraged to ask their doctor smart questions, such as if a CT scan is necessary, to check whether the facility performing their CT procedure is accredited, to ask if the dosage on the CT scanner can be adjusted for children and small adults, to avoid unnecessary repeat procedures, and to refrain from a whole-body scan unless it's a medical must.

As those with expertise in CT imaging are aware, with the increase in computer power and data channels (16, 40, 64, etc.) that can be acquired per scan rotation, the clinical use of CT in cardiac exams, vasculature structures and multi-phase imaging is on the rise. Understandably, this has led radiation safety experts in the field to research and analyze the trends in the field and the potential radiation effects on the population. The American Association of Physicists in Medicine's report entitled, "The Measurement, Reporting, and Management of Radiation Dose in CT"; AAPM Report 96, published in January 2008, compares the effective dose from CT to that of nuclear medicine studies, cardiac catheterizations and interventional fluoroscopy procedures, of which all are higher than conventional x-ray exams (see Figure 1 below).

Typical effective dose values for
CT and diagnostic studies

Figure 1.

CT PROCEDURES	EFFECTIVE DOSE (mSv)	OTHER DIAGNOSTIC STUDIES	EFFECTIVE DOSE (mSv)
Head CT	1-2	Dental bite wing x-ray	< 0.1
Chest CT	5-7	Chest x-ray	< 0.1
Abdomen	5-7	Mammogram	0.3-0.6
Pelvis	3-4	Barium enema	3-6
Abdomen and Pelvis	8-14	Lumbar spine	0.5-1.5
Calcium Score	1-3	Sestamibi myocardial perfusion	13-16
CCTA	5-15	Diagnostic Coronary angiogram	5-10
		Thallium myocardial perfusion	35-40
*US natural annual background radiation	3.0-3.6

Source: The AAPM Report 96, January 2008

Scientists estimate that the average person in the United States receives a dose of about 3.60 mSv of radiation per year (see Figure 2 below). Approximately 81% of that exposure comes from natural sources -- radon gas, the human body, outer space, and rocks and soil. The remaining 19% comes from man-made radiation sources, primarily medical x-rays.

Sources Of Radiation Dose

Ionizing radiation is known to cause cancer in humans. Radiation can also cause other adverse health effects, including genetic defects in the children of exposed parents or mental retardation in the children of mothers exposed during pregnancy. The risk of these other effects is much less than the risk of developing cancer due to radiation exposure.

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