Research Presentation Session: Cardiac

RPS 2403 - Spectral CT: new developments and clinical applications (part 2)

March 3, 11:30 - 12:30 CET

7 min
Coronary artery calcium scoring using virtual vs true non-contrast images from photon-counting coronary CT angiography
Jan Robert Kröger, Minden / Germany
Author Block: N. Haag1, A. E. Michael1, S. Lennartz2, C. Panknin3, I. Shahzadi3, J. H. Niehoff1, J. Borggrefe1, J. R. Kröger1; 1Minden/DE, 2Cologne/DE, 3Forchheim/DE
Purpose: Coronary artery calcium scoring (CACS) requires true non-contrast (TNC) CT. Photon-counting CT provides an algorithm (PureCalcium) for reconstructing virtual non-contrast images from contrast-enhanced coronary CT angiography (CCTA) specifically for CACS. The aim of this study was to assess the CACS differences based on PureCalcium images derived from contrast-enhanced CCTA compared with TNC images and evaluate the impact of these differences on the classification of patients into plaque burden categories.
Methods or Background: Images from patients who underwent photon-counting CCTA between August 2022 and May 2023 were identified and retrospectively analysed. Agatston scores were derived from TNC and PureCalcium images and tested for agreement using the intra-class correlation coefficient. Patients were categorised into different plaque burden groups based on Agatston scores and agreement was evaluated using weighted Cohen’s kappa. Wilcoxon signed-rank test and Bland-Altman analysis were used to evaluate differences, the DLP for the entire examination and TNC were analysed.
Results or Findings: Median Agatston scores were comparable between TNC and PureCalcium (4.8; IQR= 83.6 [0.0 – 2151.8] vs 2.7; IQR =89.2 [0.0-2377.1], P=.99) and showed a strong agreement and relationship (ICC = 0.98, 95% CI [0.97, 0.99]. On Bland-Altman analysis only two patients showed a bias outside of the limits of agreement. With PureCalcium CACS, 74% of patients were correctly classified into plaque burden groups agreement excellent (κ = 0.88). TNC contributed a mean of 19.7 ± 8.8% SD of the radiation dose of the entire examination.
Conclusion: Agatston scores for coronary artery disease derived from PureCalcium and TNC images from contrast-enhanced photon counting CCTA high agreement and did not differ significantly. PureCalcium CACS correctly classified most patients into plaque burden groups. Omitting TNC scans reduced the radiation dose.
Limitations: Distribution of Agatston scores was skewed and lower than expected in our study cohort.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: This study was approved by the local ethics committee as a retrospective study
7 min
In vitro study of the quality of multi-parameter coronary stent images on second-generation dual-layer detector spectral CT
Lihong Chen, Xi'an / China
Author Block: L. Chen, Z. Jian; Xi An/CN
Purpose: The aim of this study was to evaluate the image quality of the multi-parameter coronary stent images on second-generation dual-layer detector spectral CT.
Methods or Background: Eighteen coronary stents of different materials and diameters were placed in simulated coronary vessels containing a concentration of 11 mg/L iodine contrast agent. Scanning was performed using second generation dual-layer detector spectral CT. 50~190 keV monoenergetic (20 keV interval), conventional, and iodine map images were reconstructed. Stent lumen score, stent structure score, and degree of blooming artefact were subjectively evaluated (Likert 4-score). Stent lumen contrast noise ratios (CNRs), non-stent lumen contrast noise ratios (CNRc), inner diameter differences (IDD), and blooming artifact index (BAI) were used for objective evaluation. The stents were divided into small diameter subgroups (<3 mm) and large diameter subgroups (≥3 mm) according to their diameters. Repeated-measure ANOVA and Tukey's test were used for multi-comparison.
Results or Findings: For all stents and the large diameter subgroup, the optimal monoenergetic images had the highest stent lumen score, which was significantly greater than those of iodine map images. The iodine map images had the highest stent structure score, which was significantly greater than those of iodine maps (for all stents and small diameter subgroup) and conventional images (for all stents and both subgroups). CNRs and CNRc decreased with increasing mono-energy level. For all stents and both subgroups, the CNRs and CNRc of optimal monoenergetic images were greater than for conventional and iodine map images. For all stents, iodine map images had the smallest IDD and BAI.
Conclusion: Monoenergetic imaging on the second-generation dual-layer detector spectral CT has advantages in assessing stent lumen and improving CNR. Meanwhile, iodine map imaging has advantages in assessing stent structure and internal diameter.
Keywords: Stent; Computed tomography; Coronary vessels
Limitations: The main limitation was that this was a phantom study.
Funding for this study: No funding was obtained for this study.
Has your study been approved by an ethics committee? Not applicable
Ethics committee - additional information: No ethical clearance was sought for this study.
7 min
Ultra-high resolution coronary CT angiography on photon-counting detector CT: impact of quantum iterative reconstruction
Milán Vecsey-Nagy, Budapest / Hungary
Author Block: M. Vecsey-Nagy1, G. Tremamunno1, U. J. Schoepf1, N. Fink1, E. Zsarnóczay1, P. Maurovich-Horvat2, B. Szilveszter2, A. Varga-Szemes1, T. S. Emrich1; 1Charleston, SC/US, 2Budapest/HU
Purpose: The objective of this study was to assess the impact of different quantum iterative reconstruction (QIR) levels on objective and subjective image quality of ultra-high resolution (UHR) coronary CT angiography (CCTA) images and to determine the accuracy of stenosis quantification using photon-counting detector CT (PCD-CT) .
Methods or Background: A dynamic vessel phantom containing two calcified lesions (25% and 50% stenosis) was scanned at 60, 80 and 100 beats per minute with a PCD-CT system. In vivo examinations were performed in 102 CCTA patients. All scans were acquired in UHR mode (slice thickness: 0.2 mm, kernel: bv64) and reconstructed with four different QIR levels (1-4). Image noise, signal-to-noise ratio (SNR), sharpness, and percent diameter stenosis (PDS) were quantified on the phantom, while subjective quality metrics (graininess, sharpness, overall image quality) were assessed on clinical scans.
Results or Findings: Increasing QIR levels resulted in significantly lower objective image noise and higher SNR (p<0.001), while sharpness and PDS values did not differ significantly between QIRs (all pairwise p>0.013). Subjective graininess of in vivo images significantly decreased with increasing QIR levels, with significantly higher image quality scores for each stepwise increase (all pairwise p<0.001). Qualitative sharpness, on the other hand, did not differ across different levels of QIR (p=0.15).
Conclusion: The novel QIR algorithm may enhance image quality of CCTA datasets without compromising image sharpness or accurate stenosis measurements, with the most prominent benefits at the highest strength level.
Limitations: The subjective aspect of the qualitative analysis introduces the possibility of bias into the study. Moreover, although potential usefulness of QIR in reducing radiation dose may be proposed, we have not yet examined methods of radiation dose reduction with QIR.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The protocol for this prospective, HIPAA-compliant study was approved by the local Institutional Review Board (#6030).
7 min
Feasibility of coronary CT angiography-based fractional flow reserve using a clinical photon-counting detector CT system
Emese Zsarnóczay, Budapest / Hungary
Author Block: E. Zsarnóczay1, D. Pinos2, U. J. Schoepf2, N. Fink2, J. O'Doherty2, M. Vecsey-Nagy2, P. Maurovich-Horvat1, T. S. Emrich2, A. Varga-Szemes2; 1Budapest/HU, 2Charleston, SC/US
Purpose: The aim of this study was to intra-individually compare CT-FFR between photon-counting detector (PCD) and conventional energy-integrating detector (EID) CT systems.
Methods or Background: In this single-centre prospective study, adults who underwent CCTA on an EID-CT system were recruited for research PCD-CT scans between July 2021 to March 2022. EID-CT images were reconstructed (Bv36 kernel, iterative reconstruction level 3, 0.5 mm slice thickness). PCD-CT images were post-processed with settings matched to EID-CT as close as possible (Bv36 kernel, quantum iterative reconstruction level 3, virtual mono-energetic level 55 keV, 0.6 mm slice thickness). CT-FFR was obtained semi-automatically using a prototype on-site machine learning algorithm by two readers. The lowest CT-FFR value was used for the per-patient analysis and a CT-FFR ≤0.75 was considered haemodynamically significant. Correlation and reliability between CT-FFREID-CT and CT-FFRPCD-CT were assessed with Spearman (r) and intraclass correlation coefficients (ICC).
Results or Findings: A total of 22 patients (63.3±9.2 years; 7 women) were included. The median time between EID-CT and PCD-CT was 5.5 days. Comparison of CT-FFR values showed no significant difference and strong agreement between EID-CT and PCD-CT in the per-vessel analysis (0.88 [0.74-0.94] vs. 0.87 [0.76-0.93], P=0.096, mean bias 0.02, limits of agreement [LoA] -0.14/0.19, r=0.83, ICC=0.92), and in the per-patient analysis (0.81 [0.60-0.86] vs. 0.76 [0.64-0.86], P=0.768, mean bias 0.02, LoA -0.15/0.19, r=0.90, ICC=0.93). All included patients were classified into the same category (CT-FFR>0.75 vs ≤0.75) with both CT systems.
Conclusion: PCD-CT-based CT-FFR evaluation is feasible and correlates well with EID-CT-based CT-FFR.
Limitations: CT-FFR values from EID- and PCD-CT were not compared with invasively measured FFR. Only one reconstruction setting was used for image postprocessing with EID- and PCD-CT.
Funding for this study: This research was partially funded by a grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The protocol of this prospective, Health Insurance Portability and Accountability Act–compliant, single-centre study was approved by the local Institutional Review Board, and written informed consent was obtained from each participant.
7 min
Impact of reconstruction parameters on the accuracy of myocardial extracellular volume quantification on a first-generation photon-counting detector CT
Chiara Gnasso, Milan / Italy
Author Block: C. Gnasso1, D. Pinos2, U. J. Schoepf2, M. Vecsey-Nagy2, E. Zsarnóczay2, N. Fink2, R. J. Holtackers3, A. Varga-Szemes2, T. S. Emrich2; 1Milan/IT, 2Charleston, SC/US, 3Maastricht/NL
Purpose: The potential role of cardiac CT has increasingly been demonstrated for the assessment of diffuse myocardial fibrosis through the quantification of extracellular volume (ECV). The recently introduced photon-counting detector (PCD)-CT technology may deliver more accurate ECV quantification compared to energy-integrating detector CT. This study aimed to establish the image reconstruction settings for PCD-CT delayed acquisitions yielding the highest agreement in ECV quantification compared to MRI-ECV.
Methods or Background: Patients (n=27, 53.1±17.2 years; 14 women) prospectively underwent same-day cardiac MRI and PCD-CT. Delayed CT scans were reconstructed with different quantum iterative reconstruction levels (QIR 1-4), slice thicknesses (s.t. 0.4-8 mm), and virtual monoenergetic imaging levels (VMI, 40-90 keV), as shown in Figure 1. ECV was quantified for each reconstruction setting and compared using ANOVA for repeated measures and t-test for pairwise comparisons. The agreement with MRI was assessed with Bland-Altman plots and Lin’s concordance correlation coefficient (CCC).
Results or Findings: ECV values didn’t differ significantly among QIR levels (p=1.00), whereas a significant difference was observed throughout different slice thicknesses, with 0.4 mm yielding the highest agreement (CCC 0.944). 45 keV VMI reconstructions had the lowest mean bias (0.6, 95%CI 0.1–1.4) compared to MRI. Using the most optimal reconstruction settings (QIR4; s.t. 0.4 mm; VMI 45 keV), a 63% reduction in mean bias and a 6% increase in concordance with MRI were achieved compared to the standard settings used in previous publications (QIR3; s.t. 1.5 mm; VMI 65 keV).
Conclusion: The appropriate selection of CT reconstruction parameters improves the agreement between PCD-CT and MRI ECV values.
Limitations: Our study has the following limitations: first, it is a single-centre study with a relatively small sample size; second, the lack of a histological reference, and third, the use of MRI-derived synthetic Hct.
Funding for this study: This study was supported by an institutional research grant from Siemens Healthcare.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study is HIPAA-compliant.
7 min
Impact of photon-counting CT-based virtual mono-energetic imaging on detecting myocardial late iodine enhancement: comparison with MRI reference
Chiara Gnasso, Milan / Italy
Author Block: C. Gnasso1, M. Vecsey-Nagy2, U. J. Schoepf2, D. Pinos2, E. Zsarnóczay2, G. Tremamunno2, R. J. Holtackers3, T. S. Emrich4, A. Varga-Szemes2; 1Milan/IT, 2Charleston, SC/US, 3Maastricht/NL, 4Frankfurt/DE
Purpose: Cardiac CT has the ability to detect myocardial scar, which can potentially be improved by the use of the recently-introduced photon-counting detector (PCD)-CT technology. This study aims to investigate the image quality and diagnostic performance of late iodine enhancement (LIE)-CT scans at different virtual monoenergetic image (VMI) levels in detecting and characterising myocardial scars, using late gadolinium enhancement (LGE)-MRI as the reference standard.
Methods or Background: This is a post-hoc analysis of a prospective research study including patients with various cardiomyopathies who underwent clinical LGE-MRI and same-day research LIE-CT scan between July 2021 and January 2022. LIE PCD-CT scans were reconstructed at different VMI levels (40, 45, 50, 60, 70, and 90 keV). Two blinded readers evaluated subjective and objective image quality, presence of scar and scar pattern on a per-segment level. The diagnostic performance was evaluated as sensitivity, specificity, and accuracy. Agreement with MRI in scar detection and pattern identification were evaluated with Cohen’s κ statistic.
Results or Findings: The LIE-CT scans of 27 patients (48% male, mean age 52.9 ± 17.2 years) were analyzed. VMI at 50 keV demonstrated an adequate objective and subjective image quality and the best trade-off between sensitivity (87.4%), specificity (97.8%), and accuracy (95.9%), in scar detection, with an excellent agreement with MRI (κ = 0.86). 50 keV also showed the highest concordance in discriminating different scar patterns, with a 100% rate for detecting subepicardial scars and patchy fibrosis.
Conclusion: PCD-CT VMI reconstructions at 50 keV are a valuable tool for myocardial scar detection and characterisation, demonstrating excellent diagnostic performance and agreement with cardiac MRI.
Limitations: Due to the sub-analysis nature of this study, selection bias needs to be considered. Due to the limited number of patients, per-patient analysis was not performed.
Funding for this study: No funding was obtained for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study is HIPAA-compliant.
7 min
Dual-layer spectral CT-based quantification of myocardial extracellular volume fraction using CMR as a reference in aortic valve disease
Gang Wang, Lanzhou / China
Author Block: Y. Li1, X. He1, J. Nan1, W. Tian1, X. Lu1, L. Cao1, Y. Wang2, G. Wang1, Z. Chen1; 1Lanzhou/CN, 2Shanghai/CN
Purpose: The objective of this study was to assess the agreement of myocardial extracellular volume fraction (ECV) measurements in patients with aortic valve disease (AVD) between dual-layer spectral detector CT (DLCT) and cardiovascular magnetic resonance (CMR) measurements.
Methods or Background: Twenty-three patients diagnosed with AVD who underwent both simultaneous DLCT late iodine enhancement and CMR examinations were retrospectively enrolled. These examinations performed within a week. ECV values were calculated from the iodine map (CT-ECV-Iodine) and the conventional CT images (CT-ECV-HU (Hounsfield units)) derived from DLCT. CT-ECV-Iodine, CT-ECV-HU, and CMR-ECV were measured at three short axes (base, middle, and apex), according to the American Heart Association 16-segment model. Global and segmental ECVSs of cardiac is recorded. The Pearson correlation coefficient and Bland-Altman plot were used to calculate the correlation and agreements among these measurements.
Results or Findings: The correlation analysis revealed a strong correlation between CT-ECV-Iodine and CT-ECV-HU (r =0.954, 95% confidence interval (CI) [0.89-0.98], p <0.001), a relatively high correlation between CT-ECV-Iodine and CMR-ECV (r =0.862, 95% CI [0.70-0.94], p <0.001), and a significant correlation between CT-ECV-HU and CMR-ECV (r =0.812, 95% CI [0.60-0.92], p <0.001). The mean differences between these measurements were as follows: CT-ECV-Iodine and CT-ECV-HU exhibited a mean difference of -0.40% (with a 95% limit of agreement (LOA) ranging from -3.2% to 2.4%), CT-ECV-Iodine and CMR-ECV showed a mean difference of 0.76% (95% LOA: -3.5-5.0%), and CT-ECV-HU and CMR-ECV had a mean difference of 1.17 (95% LOA: -4.22-6.55%).
Conclusion: DLCT-based ECV measurements showed a strong correlation with CMR in patients with AVD. Furthermore, it is a potential alternative way for assessment of myocardial interstitial fibrosis in AVD.
Limitations: Small sample size is the limitation of this study.
Funding for this study: This study is supported by the Lanzhou Science and technology project Foundation (2020-2D-80) and First Hospital of Lanzhou University Hospital Foundation (ldyyyn2019-78).
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethical Committee of the first hospital of Lanzhou University.
7 min
Quantification of myocardial extracellular volume and aortic valve calcification scores using dual-layer spectral CT to identify severe aortic regurgitation in patients with aortic valve disease
ZiXian Chen, Lanzhou / China
Author Block: Y. Li1, X. He1, L. Cao1, W. Tian1, X. Lu1, J. Xu1, Y. Wang2, G. Wang1, Z. Chen1; 1Lan Zhou city/CN, 2Shanghai/CN
Purpose: To investigate the diagnostic performance of a combination of myocardial extracellular volume fraction (ECV) and aortic valve calcification scores (AVCS) measured using dual-layer spectral detector CT (DLCT) in the identifying of severe aortic regurgitation (sAR) in patients with aortic valve disease (AVD).
Methods or Background: A total of 54 patients with AVD (37 aortic regurgitation (AR), including 16 severe AR (sAR) and 21 with mild to moderate AR (mAR); 17 aortic stenosis (AS)) who underwent non-contrast and late iodine enhancement DLCT examinations were retrospectively included. The ECV map was reconstructed using a dedicated workstation, and AVCS was evaluated semi-automatically using multiplanar reconstruction by Agatston algorithm from the non-contrast phase of DLCT. AVCS scores were categorized into four grades. Student’s t-test and Mann-Whitney U test were performed. The feasibility of CT-ECV combined with AVCS grades in identifying sAR was evaluated using the receiver operating characteristic curve.
Results or Findings: In the sAR group, the ECV was significantly higher (32.29 [30.26-35.57]% vs 29.30 [27.08, 32.71]% , p=0.03) than non-sAR group, while the AVCS grades were significantly lower (1.88±0.48 vs 2.5±0.94, p=0.02). Using an ECV cutoff of 29.13%, the AUC for discriminating sAR was 0.75. The combined model of ECV and AVCS grades demonstrated notable diagnostic performance in distinguishing sAR from non-sAR, with an AUC of 0.82, sensitivity of 94% and specificity of 55%. To differentiate between AR severity levels, there was a significant difference in ECV between the sAR group and the mAR group (p =0.02). The AUC was 0.79, with a sensitivity of 75% and specificity of 72%.
Conclusion: The combination of DLCT-ECV and AVCS grades, assessed via spectral CT, shows promise for identifying severe aortic regurgitation in patients with aortic valve disease.
Limitations: Small sample size was a limitation of this study.
Funding for this study: This study is supported by the Lanzhou Science and technology project Foundation (2020-2D-80) and First Hospital of Lanzhou University Hospital Foundation (ldyyyn2019-78).
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethical Committee of the first hospital of Lanzhou University.

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