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.
Highlights
Endovascular aneurysm repair (EVAR) has become the primary treatment option for a wide variety of aneurysms of the descending aorta and some types of aortic dissection [1,2]
Consecutive patients status post endovascular aneurysm repair (EVAR) who had undergone clinically indicated CT of the aorta on a novel PhotonCounting Detector (PCD)-CT between May and July 2021 were included according to the following inclusion criteria: (1) the patient was status post-EVAR with aortic stent prosthesis, (2) the patient had undergone a biphasic CT scan of the aorta, (3) CT raw data had successfully been transferred to a long-term archive
Twenty consecutive patients after EVAR who had undergone biphasic CT scans of the aorta on a novel Photon-counting detector CT (PCD-CT) were included in this study
Summary
Endovascular aneurysm repair (EVAR) has become the primary treatment option for a wide variety of aneurysms of the descending aorta and some types of aortic dissection [1,2]. For the confident exclusion of endoleaks, a triphasic scan protocol is frequently applied, comprising a non-contrast acquisition followed by an arterial and venous phase scan [3]. These follow-up scans lead to substantial cumulative radiation exposure in this patient cohort [4,5,6]. Based on dual-energy information, the iodine-containing contrast material can be quantified and subtracted, resulting in a ‘virtual non-contrast’ (VNC) series. Initial non-contrast scans are still widely performed in this clinical context [3]
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