Use of helical high-resolution multi-detector CT (MDCT) with one millimeter collimation proves to be better than conventional high-resolution CT (HRCT) in showing the presence and extent of bronchiectasis (abnormal enlargement of the respiratory passages within the lungs), according to a study conducted by Vancouver General Hospital's department of radiology in Vancouver, BC, Canada.
"Although high resolution CT [when using 1 to 1.5 millimeter slices every 10 millimeters] has been regarded as the radiological gold standard in the diagnosis of bronchiectasis, we knew from previous studies that it had significant limitations," said Nestor Muller, MD, lead author of the study. "The main limitation is that the traditional high-resolution CT technique, consisting of thin sections at ten millimeter intervals through the chest, fails to evaluate most of the lungs and the airways therein," said Dr. Muller.
The study included 61 patients who were diagnosed with bronchiectasis by either MDCT or HRCT. Seven patients had positive MDCT scans only and two patients had positive HRCT scans only. MDCT detected bronchiectasis in 202 lobes compared with 162 lobes with HRCT.
"The results indicate that volumetric CT with thin sections is superior to conventional high-resolution CT technique in the detection of bronchiectasis. It should be noted however that when using the same exposure factors MDCT results in considerably greater radiation dose," said Dr. Muller. "The radiation risk is considerably greater in children than in adults, being lowest in patients over 50. In all circumstances, we try to limit the radiation dose by using the lowest exposure factors consistent with good image quality," he said.