Optimising dual-energy CT scan parameters for virtual non-calcium imaging of the bone marrow: a phantom study

Abstract

BackgroundWe investigated the influence of dose, spectral separation, pitch, rotation time, and reconstruction kernel on accuracy and image noise of virtual non-calcium images using a bone marrow phantom.MethodsThe phantom was developed at our institution and scanned using a third-generation dual-source dual-energy\xa0CT scanner at five different spectral separations by varying the tube-voltage combinations (70\u2009kV/Sn150\xa0kV, 80\u2009kV/Sn150\xa0kV, 90\u2009kV/Sn150\xa0kV, and 100\u2009kV/Sn150\xa0kV, all with 0.6-mm tin filter [Sn]; 80\u2009kV/140\u2009kV without tin filter) at six different doses (volume computed tomography dose index from 1 to 80\u2009mGy). In separate experiments, rotation times, pitch, and reconstruction kernels were varied at a constant dose and tube voltage. Accuracy was determined by measuring the mean error between virtual non-calcium values in the fluid within and outside of the bone. Image noise was defined as the standard deviation of virtual non-calcium values.ResultsSpectral separation, dose, rotation time, or pitch did not significantly correlate (p\u2009>\u20090.083) with mean error. Increased spectral separation (rs-0.96, p\u2009<\u20090.001) and increased dose (rs-0.98, p\u2009<\u20090.001) correlated significantly with decreased image noise. Increasing sharpness of the reconstruction kernel correlated with mean error (rs 0.83, p\u2009=\u20090.015) and image noise (rs 1.0, p\u2009<\u20090.001).ConclusionsIncreased dose and increased spectral separation significantly lowered image noise in virtual non-calcium images but did not affect the accuracy. Virtual non-calcium reconstructions with similar accuracy and image noise could be achieved at a lower tube-voltage difference by increasing the dose.