Low-dose multidetector CT (MDCT) is as accurate as standard-dose MDCT in evaluating urinary stone disease, even in overweight patients.

according to a report in the February issue of the American Journal of Roentgenology.

Several authors have proposed the use of low-dose techniques to avoid the radiation doses experienced due to repeated examinations in otherwise healthy patients, the investigators explain.

Dr. Tom H. Mulkens and colleagues from Heilig Hart Ziekenhuis in Lier, Belgium, compared the performance of standard-dose MDCT with that of low-dose MDCT, performed with 4D tube current modulation, in 300 patients with renal colic. Low-dose MDCT was associated with a 51.2 per cent to 64.3 per cent reduction in radiation dose, compared with the standard-dose protocol, the authors report.

The overall accuracy of low-dose MDCT (95.3 per cent) was similar to that of standard-dose MDCT (97.3 per cent) in the hands of two experienced reviewers, the results indicate, who had a maximum of 10 false-positive and 4 false-negative findings in 300 examinations.

Overall accuracy was also high among inexperienced reviewers, the researchers note, and the diagnostic performance remained high in overweight and obese patients.

Alternative diagnoses were found on MDCT in similar percentages of patients receiving the standard dose (around 15 per cent) and those receiving the low-dose (around 16 per cent), the report indicates.

"Our study showed that low-dose MDCT with tube current modulation can be used as a standard procedure for evaluation of patients with suspected acute renal colic," the investigators conclude.

"The use of a tube current modulation mechanism adapts the tube current to the patient's anatomic configuration and size," the authors add. "Therefore, even overweight and obese patients can be examined with low doses of radiation."

AJR Am J Roentgenol 2007;188:553-562.

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