Virtual versus true non-contrast images of the brain from spectral detector CT: comparison of attenuation values and image quality

Abstract

Background Prior studies focused on utilization of dual-energy computed tomography (DECT) to better detect intracranial pathology and to reduce artifacts. It is still unclear whether virtual non-contrast (VNC) images of DECT can replace true non-contrast (TNC) images. Purpose To compare attenuation values and image quality of VNC images to TNC images of the brain, obtained using spectral detector CT (SDCT). Material and Methods We retrospectively evaluated patients that underwent head CT with and without contrast material, on a SDCT scanner at our institution (n = 33). The attenuation values of different brain structures were obtained from TNC images, the conventional images of the post-contrast exams (n = 16) or the CT angiography (CTA) (n = 17), and the derived VNC images. In total, 591 regions of interest were obtained, including white and gray matter. Two neuroradiologists independently evaluated the image quality of the VNC and TNC images, using a 5-point Likert scale. Results The mean difference between the attenuation values on the VNC versus the TNC images was <4 HU for almost all the structures. The difference reached statistical significance ( P < 0.05) for the deep gray structures but not for the white matter. The image quality score of the TNC images was 5 in all the patients (excellent gray–white matter differentiation). The scores of the VNC images differed between post-contrast and CTA examinations, with means of 4.9 ± 0.3 (excellent) and 3.2 ± 0.4 (fair), respectively ( P < 0.001). Conclusion Our results show minor differences between attenuation values of different brain structures on VNC versus TNC images of SDCT.

Dual-energy computed tomography angiography-based quantification of lesion net water uptake to identify stroke onset time

“…The stroke patients within 4.5 h had lower NWU values on all VNC and VM images derived from DECT angiography than did those with stroke occurrence beyond 4.5 h (p-value <0.001). According to previous reports, DECT angiography can capture different characteristic absorption profiles of substances and could be used to obtain virtual “NCCT” and “CTA” images [ 19 , 20 ]. Furthermore, it showed greater sensitivity in identifying ischemic brain tissue as an area of lower attenuation value compared with conventional CT [ 21 , 31 , 32 ].…”

“…Dual-energy CT (DECT) is a standard clinical technique that enables material characterization with differential CT attenuation at two distinct energy levels [ 18 ]. DECT angiography enables the reliable derivation of virtual images [ 19 , 20 ], which means both virtual “NCCT” and “CTA” images can be obtained simultaneously through DECT angiography reconstructions. Several previous findings have reported the value of virtual images reconstructed from DECT to optimize the visualization of acute cerebral infarction, in comparison with that achieved using conventional NCCT [ [21] , [22] , [23] ].…”

Virtual Non-Contrast versus True Native in Photon-Counting CT: Stability of Density of Upper Abdominal Organs and Vessels

“…Comparison tables were created with the tableone package (version 0.13.2). Boxplots were cre- 1), in the descending aorta (2), in the inferior vena cava (3), in the liver parenchyma (4), in the spleen parenchyma (5), in the psoas muscle (6), in the subcutaneous adipose tissue (7), in the surrounding air (8), in the erector spinae muscle (9) and in the first lumbar vertebral body (10).…”

“…All measurements were performed by the same observer. 4), in the spleen parenchyma (5), in the psoas muscle (6), in the subcutaneous adipose tissue (7), in the surrounding air (8), in the erector spinae muscle (9) and in the first lumbar vertebral body (10).…”

Advanced Neuroimaging With Photon-Counting Detector CT

“…In addition, postprocessing of VNC images from postcontrast CT scans might allow to replace the true noncontrast image acquisition to reduce the applied radiation dose. This concept has already been shown feasible in spectral imaging from DECT with minor differences between attenuation values of different brain structures on VNC and true noncontrast images 71 . A recent study about VNC imaging in the abdomen has shown that PCD-CT allows for the postprocessing of VNC images of the liver with accurate attenuation values, being independent of dose, attenuation of base material, and liver iodine content 72 …”