Radiation intensity () and visibility of anatomical structures in head CT examinations

Abstract

The purpose of this study was to quantify how changing the amount of radiation used to perform routine head CT examinations (CTDIvol) affects visibility of key anatomical structures. Eight routine noncontrast head CT exams were selected from six CT scanners, each of which had a different CTDIvol setting (60 to 75 mGy). All exams were normal and two slices were selected for evaluation, one at the level of basal ganglia and the other at the fourth ventricle. Three experienced neuroradiologists evaluated the visibility of selected structures, including the putamen, caudate nucleus, thalamus, internal capsule, grey/white differentiation, and brainstem. Images were scored on a five‐point scoring scheme (1, unacceptable, 3, satisfactory, and 5, excellent). Reader scores, averaged over the cases obtained from each scanner, were plotted as a function of the corresponding CTDIvol. Average scores for the fourth ventricle were 3.06±0.83 and for the basal ganglia were 3.20±0.86. No image received a score of 1. Two readers showed no clear trend of an increasing score with increasing CTDIvol. One reader showed a slight trend of increasing score with increasing CTDIvol, but the increase in score from a 25% increase in CTDIvol was a fraction of the standard deviation associated average scores. Collectively, results indicated that there were no clear improvements in visualizing neuroanatomy when CTDIvol increased from 60 to 75 mGy in routine head CT examinations. Our study showed no apparent benefit of using more than 60 mGy when performing routine noncontrast head CT examinations.PACS number(s): 87.57.C‐

Assessment of patient dose and noise level of clinical CT images: automated measurements

“…This finding indicated that the protocol for head CT examination produces too high a dose and too low noise, the dose could be further reduced while maintaining diagnostic image quality. Previously, Tipnis et al [42] reported that a decrease in output dose from 75 to 60 mGy in head CT examinations produced no clear degradations in depicting neuroanatomy. Based on this finding, the noise in the head image could be further increased up to about 5 HU which may be obtained with a dose lower than 60 mGy.…”

“…In the current study, however, the calculated noise level has not been compared with visual observations by expert radiologists [42]. In a follow-up study, we will compare quantitative noise levels from automated methods with qualitative radiological observations determined by a radiologist.…”