Impact of Patient Size and Radiation Dose on Accuracy and Precision of Iodine Quantification and Virtual Noncontrast Values in Dual-layer Detector CT—A Phantom Study

Quantitative accuracy of virtual non-contrast images derived from spectral detector computed tomography: an abdominal phantom study

“…As per definition of VNC error , negative values indicate that the VNC attenuation values are lower compared to the expected attenuation of the base material; hence, that the iodine-associated attenuation has been slightly overestimated, a phenomenon known from earlier studies 10 . These findings are on the lower end of earlier reported VNC errors that range from − 1.2 to 15 HU 17 , 28 , 30 . This may be explained by the fact that in this study, unlike aforementioned investigations, a solid-state phantom was used.…”

“…In accordance with earlier reports we found that VNC error is independent from kernel setting and denoising level 9 , 27 . Regarding radiation dose, which was deemed to not significantly impact VNC error based on our data, there are opposing reports 28 , 30 : While Van Hedent et al report that lower radiation dose results in greater inaccuracy of VNC it needs to be acknowledge that their lowest dose (2 mGy) was markedly lower than the one used in this study (10 mGy) 28 . Similarly, Si-Mohammed et al employing CTDI vol of 2.5 mGy, 5 mGy and 10 mGy, reported lower accuracy of VNC images 30 .…”

“…While the reason for this remains elusive, a possible hypothesis is that the medium sized phantom most closely resembles an average sized patient (350 × 250 mm) potentially effecting model assumptions in image reconstruction 2 . Other studies 28 , 30 reported that smaller phantoms yielded higher accuracy of VNC images. In line with that, we found lowest standard deviation with small size phantom.…”

“…Hua et al also report a shift from under- towards overestimation between iodine contents of 2.5 mg/ml and 5 mg/ml 4 . Opposed to this, Van Hedent et al reported no impact of iodine concentration on VNC performance 28 ; however, the lowest concentration they used was 2 mg/ml 28 . Regarding the base materials, data with attenuation different from water is sparse.…”

“…First, we did not test extreme values for radiation dose or phantom size but focused on scan parameters typically encountered in abdominal imaging and average patients. Second, we did not evaluate accuracy of iodine reconstruction as there are numerous earlier reports for SDCT and other DECT-approaches 8 – 11 , 27 , 28 . It would also be of interest to investigate the dependency of VNC error on different iodine background concentrations for the parenchyma and other organs.…”