MDCT performed using a modulated tube current system results in as much as a 64 per cent reduction in standard radiation dose without compromising accuracy, a new study finds. MDCT performed using a modulated tube current system – which adapts the tube current to the patient’s anatomic configuration and size -- results in as much as a 64 per cent reduction in standard radiation dose without compromising accuracy in the detection of urinary stone disease regardless of the size of the patient, a new study finds.

The study included 300 patients with 150 of them undergoing a standard dose protocol and 150 patients undergoing the lower dose protocol. Of the 300 patients, 158 had urinary stone disease; the difference in urinary stones between the standard and low dose groups was not significant, said Tom H. Mulkens, MD, of Heilig Hart Ziekenhuis in Lier, Belgium. Dr. Mulkens is the lead author of the study.

The overall accuracy by experienced radiologists was about 97 per cent for standard-dose and 95 per cent for low-dose examinations, Dr. Mulkens said. The low dose procedures had about a 99 per cent accuracy rate for overweight and obese patients, he added.

The overall accuracy by first-year residents for both low-dose and standard radiation dose examinations was about 94 per cent, he noted.
The lower dose examination also allowed for accurate alternative diagnoses by the board-certified radiologists in 25 patients (15 per cent). The experienced radiologists reading the images correctly identified a variety of other disorders and diseases (including appendicitis, prostate cancer and ovarian cysts and masses) that were causing the patient’s symptoms instead or urinary stone disease. Only one case of cholecystolithiasis was missed by one experienced radiologists. The residents, on the other hand, made an accurate alternative diagnoses in only four-five per cent of these 25 patients, Dr. Mulkens said.

It is important to note that CT without the use of contrast media is a limited examination, and many alternative diagnoses cannot be made regardless of the dose used, Dr. Mulkens said. A complete CT examination using contrast needs to be performed in cases where the patient has persistent clinical symptoms, he added.

Urinary stone disease affects about 12 per cent -15 per cent of the population in the Western world, said Dr. Mulkens. Many of these patients are between the ages of 30 and 50 and are otherwise healthy. In addition, there is a group of patients who have recurrent urinary stone formation. Using a lower dose procedure is important because of all those reasons, he said.

The study appeared in the February issue of the American Journal of Roentgenology, which is published by the American Roentgen Ray Society.