We compared semiautomatic contour detection and manual contour tracing in cardiac multidetector row computed tomography (MDCT) with magnetic resonance imaging (MRI) for calculation of left-ventricular (LV) volumes. The study included 30 patients who underwent contrast-enhanced cardiac MDCT and cardiac cine-MRI. Were calculated 8 mm short-axis slices from MDCT data using three-dimensional multiphase image reconstruction. LV volumes including peak ejection rate and peak filling rate were calculated from manually and semiautomatically determined contours. Results were compared to those from cine-MRI with manually drawn contours as the standard of reference. We found good agreement for the LV volumes, with an ejection fraction of 47.1+/-9.4% for manually drawn contours, 47.9+/-9.9% for semiautomatically detected contours on MDCT, and 48.0+/-10.2% for MRI. Except for peak-filling rate analysis of variance revealed no difference between any of these techniques. Bland-Altman plots and Lin's concordance correlation coefficient showed best agreement between MRI and manual contour tracing in MDCT. Calculation of LV volumes using either semiautomatic or manual contour tracing in cardiac MDCT is therefore feasible when compared to MRI. Automated contour detection needs to be improved to equal manual contour tracing.

Multisegmental image reconstruction improves the quantitative assessment of left ventricular function when compared to standard image reconstruction. Multisegmental image reconstruction allows qualitative wall motion analysis.

The accuracy of coronary calcium scoring using 16-row MSCT comparing 1- and 3-mm slices was assessed. A thorax phantom with calcium cylinder inserts was scanned applying a non-enhanced retrospectively ECG-gated examination protocol: collimation 12 x 0.75 mm; 120 kV; 133 mAs(eff). Thirty-eight patients were examined using the same scan protocol. Image reconstruction was performed with an effective slice thickness of 3 and 1 mm. The volume score, calcium mass and Agatston score were determined. Image noise was measured in both studies. The volume score and calcium mass varied less than the Agatston score. The overall measured calcium mass compared to the actual calcium mass revealed a relative difference of +2.0% for 1-mm slices and -1.2% for 3-mm slices. Due to increased image noise in thinner slices in the patient study (26.1 HU), overall calcium scoring with a scoring threshold of 130 HU was not feasible. Interlesion comparison showed significantly higher scoring results for thinner slices (all P<0.001). A similar accuracy comparing calcium scoring results of 1- and 3-mm slices was shown in the phantom study; therefore, the potentially necessary increase of the patient's dose in order to achieve assessable 1-mm slices with an acceptable image-to-noise-ratio appears not to be justified.

In computed tomography (CT), selection of a convolution kernel determines the tradeoff between image sharpness and pixel noise. For certain clinical applications it is desirable to have two or more sets of images with different settings. So far, this typically requires reconstruction of several sets of images. We present an alternative approach using default reconstruction of sharp images and online filtering in the spatial domain allowing modification of the sharpness-noise tradeoff in real time. A suitable smoothing filter function in the frequency domain is the ratio of smooth and original (sharp) kernel. Efficient implementation can be achieved by a Fourier transform of this ratio to the spatial domain. Separating the two-dimensional spatial filtering into two subsequent one-dimensional filtering stages in the x and y directions using a Gaussian approximation for the convolution kernel further reduces computational complexity. Due to efficient implementation, interactive modification of the filter settings becomes possible, which can completely replace the variety of different reconstruction kernels.