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Lots Of Looks At CT Radiation Risk

May 13, 2010
Written by: , Filed in: Diagnostic Imaging
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Risks accompany all imaging techniques, especially those involving radiation. Several studies presented in San Diego at last week’s annual meeting of the American Roentgen Ray Society dealt with assessing or minimizing those risks:

  • A new computer-based system called Valkyrie can track individual CT scan radiation doses, allowing patients to start logging their cumulative exposure. A study at Weill Cornell Medical Center and Columbia University Medical Center in New York randomly selected 518 CT dose reports for processing by the Valkyrie system. Valkyrie accurately extracted dose information from all 518 reports, said George Shih, MD, lead author of the study.
  • Estimated radiation risks of abdominal and pelvic CT scans for younger patients are twice those of older patients, concludes a study at the Medical University of South Carolina in Charleston. The study included 51 patients who underwent routine contrast-enhanced abdominal and pelvic CT exams. “We found that the estimated radiation risk for a 31-year-old (0.91 per 1,000) was about double that for a 74-year-old (0.47 per 1,000),” said lead author James Koonce, MD.
  • A simple z-axis modulation can significantly reduce the radiation dose from unenhanced CT scans of the head, according to a study at Penn State Hershey Medical Center in Hershey, Pennsylvania. The study looked at 100 unenhanced CT head scans with z-axis modulation and 100 without. Said the lead author, Thomas Zacharia, MD:

For unenhanced CT head examinations, the radiation dose was reduced by approximately 35 percent by using z-axis modulation, while image quality and noise were unaffected.

  • Using prospective electrocardiogram (ECG) gating and breast shields during CT coronary angiography (CTCA) of the coronary arteries can greatly reduce the radiation dose to the female breast, finds a study at the University Health Network in Toronto. The researchers scanned an adult female phantom, trying eight different CTCA protocols. “The highest breast dose (82.9 mGy) was associated with using retrospective ECG gating,” said lead author Sobhi Abadi, MD. “The lowest breast dose (15.2 mGy) was achieved with prospective gating with narrow exposure window, resulting in an 82 percent reduction in breast dose. The use of surface breast shields resulted in an additional 38 percent reduction in breast dose.”
  • Basing the automatic exposure control (AEC) technique on weight, age, and the indication for the scan can reduce radiation exposure up to 20 percent during chest CT scans, according to researchers at Massachusetts General Hospital in Boston. Evaluations of 98 patients who were scanned using the AEC technique adapted simultaneously for weight, age, and clinical indication found that it reduced radiation dose by 6 to 20 percent compared to weight-based AEC controls and 40 to 50 percent compared to fixed scans without AEC.
  • Another Massachusetts General study found that adaptive image filters can reduce radiation from chest and abdominal CT scans while significantly improving image quality. Twelve patients received a CT scan at four different levels of radiation in the chest and abdomen. All low-dose images were processed with adaptive filters. “As we lower the radiation dose, the CT images become ‘noisy’ or speckled, which makes it difficult to view the organs or the body structures in the image,” said lead author Sarabjeet Singh, MD. “Image filters allow us to effectively lower the radiation dose without sacrificing the image clarity.”

Related seminar: National Diagnostic Imaging Symposium (brand new!)

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2 Responses to “Lots Of Looks At CT Radiation Risk”

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