Radiology, Vol 146, 807-810, Copyright © 1983 by Radiological Society of North America
Baseline subtraction in quantitative cardiovascular computed tomography
DF Guthaner, M Nassi and B Bradley
Beam-hardening (BH) effect was evaluated to determine its potential
significance in quantitative blood flow measurements using computed
tomography (CT). CT scans of a water bath containing a range of
concentrations of iodine (0-15 mg/ml) placed outside and within the chest
of a dead dog were obtained at different kVp levels (100, 120, and 130
kVp). The mean CT number and standard deviation were measured over a small
region of interest for each concentration. The CT numbers measured outside
the chest were significantly higher (p less than 0.01) than those measured
inside, suggesting a BH effect. However, this BH error was almost
eliminated (p greater than 0.01) when water values (CTw) were subtracted
from the CT numbers of the iodine solutions (delta CT = CT1 - CTW). Water
subtraction was used to simulate baseline tissue CT numbers prior to
contrast enhancement so that the delta CT values were analogous to those
generally used to analyze blood flow. The BH effect was therefore not found
to be significant for blood flow measurement accuracy in cardiovascular CT.
