January 24, 2010

CT Radiation Exposure in Real Clinical Practice and Cancer Risk Estimation

Two recent studies published in the Archives of Internal Medicine in December 2009 could serve as an eye opener for every physicians ordering CT scans as well as radiologists.

Smith-Bindman et al collected CT dose data of 11 most common CT study types performed in 4 hospitals in San Francisco Bay Area. They found that there were wide variations in dose within each study type and between different types. For example, routine chest CT dose ranged from 2 to 24 mSv, routine abdomen-pelvis CT with IV contrast dose ranged from 4-45 mSv. Median effective doses for each exam were higher than they were commonly quoted in the literature, for example, 8-10 mSv is common quote for a chest CT examination. They also estimated the risk of developing cancer related to CT in several patient groups according to patient's age at the time of CT. Based on their calculation, 1 in every 80 women who undergo a chest CT for suspected pulmonary embolism at age 20 will develop cancer. Similarly, 1 in every 270 women who undergo coronary CT angiography at age 40 will develop cancer.

Berrington de Gonzalez et al utilized Medicare claim data and IMV Medical Information Division survey to project estimated age-specific cancer risk from CT studies performed in the U.S. in 2007. Excluding CT studies done for cancer diagnosis and within the last 5 years of life, 2% (29,000) excess cancers caused by CT scans in 2007 were predicted.

What is needed?
  1. Optimization and standardization of CT protocols and techniques to limit radiation
  2. Reduction of number of CT scans
  3. Collection of dose information at patient level to educate patients and health care providers about radiation exposure
1. Smith-Bindman R et al. Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer. Arch Intern Med 2009; 169:2078. PubMed abstract
2. Berrington de González A et al. Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med 2009; 169:2071. PubMed abstract

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1 comment:

joel said...

I would like discuss about the uses of medical CT.

CT scans are used to:

* detect the presence of a tumor.
* provide pictures to determine the size and location of a tumor and whether the tumor has metastasized, or spread to other tissues.
* guide a biopsy. The removal of cells or tissue from the tumor for examination is called a biopsy and is the only way to determine the exact diagnosis regarding the specific the type of pancreatic tumor.
* help plan for surgery or radiation therapy.
* determine whether the tumor is responding to treatment.

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