Accuracy Comparison of a 16 and 64 Multidetector-Row Computed Tomography Scanner to Image Small High-Density Structures

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Objectives:The accuracy in imaging small high-density structures is compared for 16 and 64 multidetector-row computed tomography (MDCT) scanners.Materials and Methods:Phantom experiments and different quantification methods are used to establish size measurement accuracy, object signal, and image noise, for both MDCT systems.Results:At similar scanning doses, image noise is larger (∼55%) for the 64 MDCT compared with the 16 MDCT, leading to lower signal-to-noise ratios (∼28% for objects <2 mm). Object spread in the xy-plane is similar for both systems; while it is reduced along the z-axis (by ∼0.18 mm) for the 64 MDCT. Measurement accuracy of the 64 MDCT is not significantly higher (P < 0.05) compared with the 16 MDCT when using a relative-threshold corresponding to 50% of the object maximum attenuation value. However, when using a fixed-threshold, interscanner and interprotocol measurement differences are statistically significant (eg, volume relative errors are reduced by ∼17% on average for the 64 MDCT).Conclusions:Measurement accuracy of the 16 and 64 MDCT scanners is not significantly different when using a 50% relative threshold. However, image noise is significantly larger for the 64 MDCT. Compared with a fixed-threshold based method, the 50% relative-threshold strongly reduces interscanner and interprotocol measurement dependency and improves accuracy.

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