Taiwan’s Ministry of Health and Welfare requested all radiology departments to complete a
questionnaire for each of their CT scanners. Information gathered included all scanning
parameters for CT head scans. For the present analysis, CT machines were divided into
three subgroups: single slice CT (Group A); multi-detector CT (MDCT) with 2-64 slices
(Group B); and MDCT with more than 64 slices (Group C). Correlations between computed
tomography dose index (CTDI) and signal-to-noise ratio (SNR) with cumulated tube rotation
number (CTW(n)) and cumulated tube rotation time (CTW(s)), and sub group analyses of
CTDI and SNR across the three groups were performed.