Juan Montoya, Presenter: Nothing to Disclose

Guozhi Zhang, Abstract Co-Author: Nothing to Disclose

Ahmed Halaweish PhD, Abstract Co-Author: Employee, Siemens AG

Shuai Leng PhD, Abstract Co-Author: Nothing to Disclose

Cynthia H. McCollough PhD, Abstract Co-Author: Research Grant, Siemens AG

Previous studies noted a decrease in stone volume in VNC images created from contrast-enhanced DECT data sets, making small stones undetectable. Improvements in spatial resolution and spectral separation may decrease this limitation. In this study on a newer dual-source CT scanner model, we evaluate the accuracy with which VNC images from contrast-enhanced DECT exams can characterize the volume of urinary stones.

Seventeen Uric Acid (UA) and 27 non-UA stones of different sizes (mean volume 98 mm3, range 10-330 mm3) were placed in 1.5 ml vials, submerged in 35 and 40 cm wide water phantoms, and scanned with a newer dual-source CT scanner (Siemens Somatom Force). Images were reconstructed using a medium sharp kernel, 1.0-mm thickness and 0.8-mm interval. Initially, vials were filled with saline in order to acquire True Non-Contrast (TNC) data, which were reconstructed as mixed DECT images. The saline was then replaced with iodine solutions having concentrations consistent with clinical CT urogram studies (40 and 80 mg/ml). Scans were repeated for each iodine concentration and VNC images were created using commercially available software (Siemens, Syngo Via VA30). Using a custom Matlab-based program (Mathworks, Matlab 8.2), stones were segmented in TNC and VNC images with an adaptive threshold technique. After segmentation, stone volumes were calculated and a two-tailed t test was performed to compare TNC and VNC volume measurements (SAS, JMP 9).

Volume measurements from VNC images were not statistically different than those from TNC mixed images (P>0.05 for both phantom sizes and iodine concentrations).

VNC images created from contrast-enhanced DECT data sets can accurately quantify urinary stone volumes, which may reduce the need to obtain a separate TNC scan in CT urogram studies.

VNC images may now have sufficient quality to allow omission of TNC scans in CT urography, or to allow detection and size assessment of urinary stones in routine contrast enhanced exams.

Montoya, J, Zhang, G, Halaweish, A, Leng, S, McCollough, C, Accurate Assessment of Urinary Stone Volume Using Virtual Non Contrast (VNC) Images Created from Contrast-Enhanced Dual-Energy CT (DECT) Scans.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013944.html