Optimization of window settings for coronary arteries assessment using spectral CT-derived virtual monoenergetic imaging.

PURPOSE: To determine the optimal window setting for virtual monoenergetic images (VMI) reconstructed from dual-layer spectral coronary computed tomography angiography (DE-CCTA) datasets. MATERIAL AND METHODS: 50 patients (30 males; mean age 61.1 ± 12.4 years who underwent DE-CCTA from May 2021 to June 2022 for suspected coronary artery disease, were retrospectively included. Image quality assessment was performed on conventional images and VMI reconstructions at 70 and 40 keV. Objective image quality was assessed using contrast-to-noise ratio (CNR). Two independent observers manually identified the best window settings (B-W/L) for VMI 70 and VMI 40 visualization. B-W/L were then normalized with aortic attenuation using linear regression analysis to obtain the optimized W/L (O-W/L) settings. Additionally, subjective image quality was evaluated using a 5-point Likert scale, and vessel diameters were measured to examine any potential impact of different W/L settings. RESULTS: VMI 40 demonstrated higher CNR values compared to conventional and VMI 70. B-W/L settings identified were 1180/280 HU for VMI 70 and 3290/900 HU for VMI 40. Subsequent linear regression analysis yielded O-W/L settings of 1155/270 HU for VMI 70 and 3230/880 HU for VMI 40. VMI 40 O-W/L received the highest scores for each parameter compared to conventional (all p < 0.0027). Using O-W/L settings for VMI 70 and VMI 40 did not result in significant differences in vessel measurements compared to conventional images. CONCLUSION: Optimization of VMI requires adjustments in W/L settings. Our results recommend W/L settings of 1155/270 HU for VMI 70 and 3230/880 HU for VMI 40.

Image quality assessment of coronary artery segments using ultra-high resolution dual source photon-counting detector computed tomography.

PURPOSE: The study is intended to assess the image quality of ultra-high resolution (UHR) coronary computed tomography angiography (CCTA) performed on dual source photon-counting detector CT (PCD-CT). METHOD: Consecutive patients, who underwent clinically indicated CCTA on PCD-CT (UHR 120x 0.2 mm collimation), were included. CCTA images were reconstructed at 0.2 mm slice thickness with Bv40, Bv44, Bv48 and Bv56 kernels and quantum iterative reconstruction level 4. Contrast-to-noise (CNR) and signal-to-noise ratios (SNR) were quantified from contrast-enhanced blood and subcutaneous adipose tissue. All reconstructions were scored per coronary segment (18-segment model) for presence, image quality, motion artefacts, stack artefacts, plaque presence and composition, and stenosis degree. Image quality was scored by two independent observers. RESULTS: Sixty patients were included (median age 62 [25th - 75th percentile: 53-67] years, 45% male, median calcium score 62 [0-217]). The mean heart rate during scanning was 71 ± 11 bpm. Median CTDIvol was 19 [16-22]mGy and median DLP 243 [198-327]mGy.cm. The SNR was 9.3 ± 2.3 and the CNR was 11.7 ± 2.6. Of the potential 1080 coronary segments (60 patients x 18 segments), 255/256 (reader1/reader2) segments could not be assessed for being absent or non-evaluable due to size. Both readers scored 85% of the segments as excellent or very good (Intraclass Correlation Coefficient: 0.88 (95% CI: 0.87-0.90). Motion artefacts were present in 45(5%) segments, stack artefacts in 60(7%) segments and metal artefacts in 9(1%) segments. CONCLUSION: UHR dual-source PCD-CT CCTA provides excellent or very good image quality in 85% of coronary segments at relatively high heart rates at moderate radiation dose with only limited stack artefacts.

Coronary calcium scoring on virtual non-contrast and virtual non-iodine reconstructions compared to true non-contrast images using photon-counting computed tomography.

OBJECTIVES: To compare coronary artery calcification (CAC) scores measured on virtual non-contrast (VNC) and virtual non-iodine (VNI) reconstructions computed from coronary computed tomography angiography (CCTA) using photon-counting computed tomography (PCCT) to true non-contrast (TNC) images. METHODS: We included 88 patients (mean age = 59 years ± 13.5, 69% male) who underwent a TNC coronary calcium scan followed by CCTA on PCCT. VNC images were reconstructed in 87 patients and VNI in 88 patients by virtually removing iodine from the CCTA images. For all reconstructions, CAC scores were determined, and patients were classified into risk categories. The overall agreement of the reconstructions was analyzed by Bland-Altman plots and the level of matching classifications. RESULTS: The median CAC score on TNC was 27.8 [0-360.4] compared to 8.5 [0.2-101.6] (p < 0.001) on VNC and 72.2 [1.3-398.8] (p < 0.001) on VNI. Bland-Altman plots depicted a bias of 148.8 (ICC = 0.82, p < 0.001) and - 57.7 (ICC = 0.95, p < 0.001) for VNC and VNI, respectively. Of all patients with CACTNC = 0, VNC reconstructions scored 63% of the patients correctly, while VNI scored 54% correctly. Of the patients with CACTNC > 0, VNC and VNI reconstructions detected the presence of coronary calcium in 90% and 92% of the patients. CACVNC tended to underestimate CAC score, whereas CACVNI overestimated, especially in the lower risk categories. According to the risk categories, VNC misclassified 55% of the patients, while VNI misclassified only 32%. CONCLUSION: Compared to TNC images, VNC underestimated and VNI overestimated the actual CAC scores. VNI reconstructions quantify and classify coronary calcification scores more accurately than VNC reconstructions. CLINICAL RELEVANCE STATEMENT: Photon-counting CT enables spectral imaging, which might obviate the need for non-contrast enhanced coronary calcium scoring, but optimization is necessary for the clinical implementation of the algorithms. KEY POINTS: • Photon-counting computed tomography uses spectral information to virtually remove the signal of contrast agents from contrast-enhanced scans. • Virtual non-contrast reconstructions tend to underestimate coronary artery calcium scores compared to true non-contrast images, while virtual non-iodine reconstructions tend to overestimate the calcium scores. • Virtual non-iodine reconstructions might obviate the need for non-contrast enhanced calcium scoring, but optimization is necessary for the clinical implementation of the algorithms.

Photon-counting Detector CT in Patients Pre- and Post-Transcatheter Aortic Valve Replacement.

Photon-counting detector CT (PCD CT) has increasingly garnered interest in cardiothoracic imaging due to its high spatial resolution and ability to perform spectral imaging. CT plays an important role in the planning and postprocedural assessment of transcatheter aortic valve replacement (TAVR). Limitations of current CT technology resulting in blooming and metal artifacts may be addressed with PCD CT. This case series demonstrates the potential advantages of PCD CT in patients prior to and post-TAVR. In TAVR planning, PCD CT allowed for a detailed depiction of the aortic valve, aortic root, coronary arteries, and potential vascular access routes. The high-spatial-resolution reconstructions enabled assessment of hypoattenuating leaflet thickening and periprosthetic leakage for prosthetic valves. This study shows promising initial results, but further research is needed to determine the clinical impact of PCD CT in patients prior to and post-TAVR. Keywords: Transcatheter Aortic Valve Replacement, Cardiac, Coronary Arteries, Heart, Valves, Photon-counting Detector CT © RSNA, 2023 An earlier incorrect version appeared online. This article was corrected on October 27, 2023.

Photon-counting CT: Review of initial clinical results.

Photon-counting computed tomography (PCCT) is a new technology that enables higher spatial resolution compared to conventional CT techniques, energy resolved imaging and spectral post-processing. This leads to improved contrast-to-noise ratio, artifact and potential dose reduction as well as elimination of electronic noise. Since the introduction of clinical PCCT in 2021, a shift has been observed from solely pre-clinical studies to clinical research (i.e. use of PCCT imaging in humans). This review article is focused on the initial clinical results of PCCT by explaining the current PCCT systems, the applications themselves and, the challenges of PCCT.

Gender Differences in Patients With Stable Chest Pain.

This study sought to investigate gender differences in clinical presentation, presence, and extent of coronary artery disease (CAD), and all-cause mortality in patients with stable chest pain who underwent coronary computed tomography angiography (CCTA). Patients who visited the fast-track outpatient clinic of the Erasmus Medical Center and underwent CCTA were analyzed. Clinical characteristics of chest pain, CAD on CCTA, coronary artery calcium scores, and survival were collected retrospectively and compared between men and women. Logistic regression was used to identify independent risk factors for the presence of CAD and Cox regression for all-cause mortality. In 1,835 included patients, 966 (52.6%) were female. Men and women were similar in age (55 vs 56 years). Compared with men, women had a lower frequency of typical pain (22.8% vs 31.1%, p <0.001), lower prevalence of significant CAD (22.2% vs 38.1%, p <0.001), and lower coronary artery calcium scores (p <0.001). CAD was more prevalent in men than in women with typical pain (67.4% vs 35.9%, p <0.001) and also with nontypical pain (24.9% vs 18.1%, p = 0.002). After adjustment for baseline characteristic, male sex was associated with all-cause mortality (adjusted hazard ratio 1.87, 95% confidence interval 1.25 to 2.80, p = 0.002). The additional risk of mortality because of CAD was similar between men and women. Stratifying by typical and nontypical pain, women again had a better prognosis. Our study identifies gender-related differences in characteristics, CCTA-findings, and outcomes for women compared with men presenting for CCTA with chest pain. Women have less CAD and a better prognosis than men, the clinical implications of which require further study.