Virtual Non-Contrast Reconstructions of Photon-Counting Detector CT Angiography Datasets as Substitutes for True Non-Contrast Acquisitions in Patients after EVAR—Performance of a Novel Calcium-Preserving Reconstruction Algorithm

Abstract

The purpose of this study was to evaluate virtual-non contrast reconstructions of Photon-Counting Detector (PCD) CT-angiography datasets using a novel calcium-preserving algorithm (VNCPC) vs. the standard algorithm (VNCConv) for their potential to replace unenhanced acquisitions (TNC) in patients after endovascular aneurysm repair (EVAR). 20 EVAR patients who had undergone CTA (unenhanced and arterial phase) on a novel PCD-CT were included. VNCConv- and VNCPC-series were derived from CTA-datasets and intraluminal signal and noise compared. Three readers evaluated image quality, contrast removal, and removal of calcifications/stent parts and assessed all VNC-series for their suitability to replace TNC-series. Image noise was higher in VNC- than in TNC-series (18.6 ± 5.3 HU, 16.7 ± 7.1 HU, and 14.9 ± 7.1 HU for VNCConv-, VNCPC-, and TNC-series, p = 0.006). Subjective image quality was substantially higher in VNCPC- than VNCConv-series (4.2 ± 0.9 vs. 2.5 ± 0.6; p < 0.001). Aortic contrast removal was complete in all VNC-series. Unlike in VNCConv-reconstructions, only minuscule parts of stents or calcifications were erroneously subtracted in VNCPC-reconstructions. Readers considered 95% of VNCPC-series fully or mostly suited to replace TNC-series; for VNCConv-reconstructions, however, only 75% were considered mostly (and none fully) suited for TNC-replacement. VNCPC-reconstructions of PCD-CT-angiography datasets have excellent image quality with complete contrast removal and only minimal erroneous subtractions of stent parts/calcifications. They could replace TNC-series in almost all cases.

Virtual Noncontrast Abdominal Imaging with Photon-counting Detector CT

“…The VNC algorithm evaluated in our study is used to subtract iodine-based contrast material from parenchymatous organs and improve quantitative attenuation measurements (eg, lesion characterization). However, known shortcomings of this algorithm are altered visualization and possible erroneous subtraction of calcified structures such as vascular calcifications or high attenuating material, including stents (37). When the aim is to visualize calcifications or metallic structures after subtracting iodine, the second virtual noncontrast postprocessing algorithm should be used (37,38).…”

“…However, known shortcomings of this algorithm are altered visualization and possible erroneous subtraction of calcified structures such as vascular calcifications or high attenuating material, including stents (37). When the aim is to visualize calcifications or metallic structures after subtracting iodine, the second virtual noncontrast postprocessing algorithm should be used (37,38).…”

Artifact Reduction From Dental Material in Photon-Counting Detector Computed Tomography Data Sets Based on High-keV Monoenergetic Imaging and Iterative Metal Artifact Reduction Reconstructions—Can We Combine the Best of Two Worlds?

“…[14][15][16][17] The recently introduced photon-counting detector CT (PCD-CT) technology is especially promising in this regard because of its routine acquisition of spectral data. 18,19 From these, high-keV VMI reconstructions can be derived, which should reduce dental artifacts. This study investigates the extent to which dental artifacts are influenced by keV level choice in VMI reconstructions, kernel choice, and the use or nonuse of an iterative metal artifact reduction (IMAR) reconstruction.…”

“…Several techniques have been developed to mitigate these artifacts, most commonly based on iterative reconstruction algorithms, 10,11 virtual monoenergetic imaging (VMI) reconstructions from multienergy imaging data, 4,5,12,13 or a combination thereof 14–17 . The recently introduced photon-counting detector CT (PCD-CT) technology is especially promising in this regard because of its routine acquisition of spectral data 18,19 . From these, high-keV VMI reconstructions can be derived, which should reduce dental artifacts.…”

Stability of spectral results in cardiac dual-source photon-counting CT

“…The copyright holder for this this version posted December 12, 2022. ; https://doi.org/10.1101/2022.12.07.22283222 doi: medRxiv preprint and PCCT illustrated good agreement with magnetic resonance imaging in terms of both visualization with VMI and iodine density maps and quantification of the extracellular volume important for evaluating myocardial fibrosis, edema, and viability in cardiomyopathy [23][24][25] . Virtual non contrast images, on the other hand, have exhibited improved preservation of stent and calcified structures compared to conventional CT for the surveillance post endovascular aneurysm repair 44 . With the consistency of the spectral results of dual source PCCT, these applications can be investigated and implemented to improve cardiovascular diagnostics.…”