RPS 2003 - Cardiac applications of photon-counting CT

Author Block: M. Vecsey-Nagy¹, G. Tremamunno¹, C. Gnasso¹, E. Zsarnóczay², D. Kravchenko², B. Szilveszter², P. Maurovich-Horvat², A. Varga-Szemes¹, T. S. Emrich¹; ¹Charleston, SC/US, ²Budapest/HU
Purpose: To evaluate the effect of photon-counting detector (PCD)-CT on coronary plaque quantification and characterization on coronary CT angiography (CCTA) series compared to energy-integrating detector (EID)-CT.
Methods or Background: Consecutive patients undergoing clinically indicated CCTA on EID-CT (192×0.6 mm collimation) were enrolled for an ultrahigh-spatial-resolution (UHR) PCD-CT scan (120×0.2 mm collimation) within 30 days. PCD-CT was acquired using equivalent or lower CT dose index and equivalent contrast media volume as the clinical scan. Total, calcified, fibrotic, and low-attenuation coronary plaque volumes were quantified and compared between scanners. Intra- and inter-reader reproducibility was assessed on both systems.
Results or Findings: A total of 164 plaques from 48 patients were segmented on both scans. Total plaque volume was lower on PCD-CT compared to EID-CT (723.5 [interquartile range: 500.6–1184.7] vs. 1084.7 [IQR: 710.7–1609.8] mm3, p<0.001). UHR-based segmentations produced lower fibrotic plaque volumes than EID-CT-based measurements (325.4 [IQR: 151.7–519.2] vs. 627.7 [IQR: 385.8–795.1] mm3, p<0.001), while low-attenuation (72.1 [IQR: 38.6–161.9] vs. 58.1 [IQR: 23.4–102.3] mm3, p=0.052) and calcified plaque volumes (IQR: 344.5 [174.3–605.7] vs. 342.1 [IQR: 180.4–607.5] mm3, p=0.50) did not differ significantly between PCD-CT and EID-CT. Total, calcified, and fibrotic plaque volumes demonstrated excellent agreement between repeated measurements and between readers for both PCD-CT and EID-CT (all intraclass correlation coefficients >0.90). While low-attenuation plaque volume had strong intra- (ICC: 0.84 [95%CI, 0.57–0.94]) and inter-reader (ICC: 0.92 [95%CI, 0.81–0.97]) agreements for PCD-CT, EID-CT showed only moderate (ICC: 0.62 [95%CI, 0.11–0.86]) and poor (ICC: 0.47 [95%CI, 0.01–0.79]) intra- and inter-reader reproducibility.
Conclusion: Compared to EID-CT, PCD-CT UHR imaging reduces segmented coronary plaque volume by nearly one-third and improves the reproducibility of low-attenuation plaque measurements.
Limitations: Lack of invasive reference.
Funding for this study: The study was funded by a research grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Local Ethics Committee approved the present study.

Author Block: A. Choux¹, S. Sharma², S. Ross², R. Thompson², Z. Yu², A. Pourmorteza¹; ¹Atlanta, GA/US, ²Vernon Hills, IL/US
Purpose: Photon-counting detector CT (PCD-CT) has demonstrated significant radiation dose reduction capabilities compared to energy-integrating detector CT (EID-CT), particularly for coronary artery calcium scoring (CACS). Alternatively, the dose savings from PCD-CT can be leveraged to improve the reproducibility of CACS by reconstructing images with thinner slice thicknesses to reduce variability from partial volume effects (PVE). This ex vivo study aims to evaluate and quantify the effect of PVE on reproducibility of calcified plaque volume measurements.
Methods or Background: Six excised human hearts with varying degrees of calcification were placed inside a chest phantom and scanned on a CdZnTe-based PCD-CT (120 kVp and 250 mAs). To simulate variability in the scan and reconstruction ranges, 10 image volumes were reconstructed for each heart using identical parameters, with the only variation being the starting slice location, which was incremented by 1/10 of the slice thickness for each reconstruction. Images were reconstructed using FBP (soft kernel, 0.3 mm in-plane pixel size) at both 3-mm (recommended for CACS) and 1.5-mm slice thicknesses. Calcium volume was measured using 130 HU threshold (as per SCCT guidelines). Variability was quantified as the ratio of std deviation and mean of calcium volume measurements for each heart and a paired t-test (alpha=0.05) was used for establishing statistical significance.
Results or Findings: Variability was found to be 36.2% for conventional 3-mm images, which was significantly higher than the 16.6% variability for 1.5-mm images (p<0.001).
Conclusion: Slight variations in scan or reconstruction range leads to significant variability in coronary plaque characterization. Taking advantage of thinner slices provided by PCD-CT (matched in radiation dose to thick EID slices) can mitigate this variability drastically.
Limitations: This was a small sample size ex-vivo study.
Funding for this study: Sponsored research agreement with Canon Medical Research USA, Inc.
Has your study been approved by an ethics committee? Not applicable
Ethics committee - additional information: Ex vivo study, did not require ethics committee approval

Author Block: M. Gruber, D. Beitzke, C. Loewe, D. Beitzke; Vienna/AT
Purpose: Coronary computed tomography angiography (CCTA) enables non-invasive quantification of plaque burden and composition. The aim of this study was to evaluate the intra-reader and inter-platform reproducibility of coronary plaque volume and composition measurements from two plaque analysis software solutions using a first-generation Photon-counting CT (PCCT) system.
Methods or Background: Twenty plaques from thirteen patients who underwent CCTA with a slice thickness of 0.4 mm were analyzed. Plaque quantification was performed using two dedicated software solutions (Software 1: Syngo.via Frontier CT Coronary Plaque Analysis, Siemens Healthineers; Software 2: QAngio CT, Medis Medical Imaging Systems). Volumes of coronary lumen, total plaque and plaque components were assessed at two time points with each software using the following attenuation thresholds for plaque classification in Hounsfield units (HU) : necrotic core: -30 to 30 HU, fibrotic plaque: 31 to 350 HU and calcified plaque: >351 HU.
Results or Findings: Intraobserver variability, determined by the Pearson correlation coefficient showed a strong positive correlation (r = 0.94, p< 0.001), indicating a high consistency in repeated measures. Furthermore, the paired-samples t-test showed no statistically significant difference between the two time points for Software 1 t(19) = 0.77, p= 0.45 or Software 2 t(19) = -0.81, p= 0.43). A repeated-measures ANOVA revealed no significant main effect for the software type, but differences were observed for lumen volume and calcified plaque volume with F(11.78, 33.85) =12.81, p< 0.001 and F(1.29, 24.56) = 13.89, p < 0.001, respectively.
Conclusion: Quantification measurements of plaque with PCCT are feasible and highly reproducible, indicating that software comparisons should take into account potential differences in measurements of specific components.
Limitations: Limitations of this study are the relatively small sample size, as well as the reliance on a single reader.
Funding for this study: Beitzke Daniela as a research radiographer is supported by a research grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study is approved by the local Ethics board. All patients gave written and informed consent.

Author Block: G. Tremamunno¹, A. Varga-Szemes², U. J. Schoepf², D. Kravchenko², M. T. Hagar², A. Laghi¹, T. S. Emrich², M. Vecsey-Nagy²; ¹Rome/IT, ²Charleston, SC/US
Purpose: To assess the impact of ultrahigh-resolution (UHR) photon-counting detector (PCD)-CT on the semiquantitative evaluation of coronary artery disease (CAD) compared to energy-integrating detector (EID)-CT.
Methods or Background: Patients undergoing coronary CT angiography (CCTA) on an EID-CT system were prospectively enrolled for UHR PCD-CT scan within 30 days. Both datasets were visually evaluated using five established semiquantitative scores: Segment Involvement Score (SIS), Segment Stenosis Score (SSS), Multivessel Aggregate Stenosis Score (MVAS), CCTA-adapted Leaman score (CT-LeSc), and Coronary Artery Disease Reporting and Data System (CAD-RADS). Additionally, the total number of detected plaques and high-risk features were reported (positive remodeling, spotty calcification, low-attenuation, and napkin-ring sign).
Results or Findings: The cohort comprised 46 patients (37 men, 68.4±6.9 years). When assessing stenosis severity, PCD-CT showed lower SSS (3.5 [1.3-5.0] vs 6.5 [3.0-9.8], p<0.001), MVAS (5.5 [4.0-7.0] vs 7.0 [5.0-9.0], p<0.001), and CT-LeSc (10.4 [8.5-13.9] vs 11.2 [8.8-15.4], p=0.032). Furthermore, 52% (24/46) of patients were reclassified to a lower CAD-RADS category compared to EID-CT. In terms of CAD extent, PCD-CT demonstrated higher SIS (8.0 [6.0-9.0] vs 7.0 [6.0-8.8], p=0.018) and plaque count (9.0 [7.0-13.8] vs 7.0 [7.0-9.8] p<0.001). Positive remodeling was less frequent in PCD-CT datasets (2.0 [1.0-4.3] vs 1.0 [0.0-3.0], p=0.012), with no significant differences in other high-risk features.
Conclusion: The use of UHR PCD-CT results in the detection of less severe, but more extensive CAD in the same patient compared to EID-CT. The effect of such CCTA-based differences on individual risk stratification needs further investigation.
Limitations: Only a limited number of patients were enrolled and the characterization and extent of plaques were not validated against invasive reference.
Funding for this study: This study received funding by Siemens Healthineers
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Name of Institution: Medical University of South Carolina
Code/Number: Pro00108359
Date of Approval: 4/13/2021

Author Block: M. Vecsey-Nagy¹, T. S. Emrich¹, G. Tremamunno¹, D. Kravchenko¹, M. T. Hagar¹, B. Szilveszter², P. Maurovich-Horvat², A. Varga-Szemes¹, J. A. Decker³; ¹Charleston, SC/US, ²Budapest/HU, ³Augsburg/DE
Purpose: To simulate the cost-effectiveness of ultrahigh-resolution (UHR) photon-counting detector (PCD)-CT in stable chest pain patients undergoing coronary CT angiography (CCTA).
Methods or Background: A decision and simulation model was developed using Monte Carlo simulations with 1,000 bootstrap resamples to estimate the costs associated with PCD-CT in lieu of EID-CT for CCTA and the referral for subsequent testing. The model was constructed using the diagnostic accuracy metrics of 55 coronary lesions of patients who underwent CCTA on both CT systems and subsequent invasive coronary angiography (ICA). Sensitivity and specificity were defined for each Coronary Artery Disease Reporting and Data System category. The aggregate healthcare expenditures were derived from the hospital billing system.
Results or Findings: Assuming a projected cohort of 15,000 patients over the lifetime of the PCD-CT, its implementation resulted in a 18.9% reduction in the number of functional follow-up tests (6330.3 ± 59.5 vs. 5135.7 ± 60.6, p<0.001), a 6.0% reduction in performed ICAs (1,447.7 ± 36.2 vs. 1,360.2 ± 34.7, p<0.001), and a 9.4% decrease in major procedure-related complications. Over a 10-year expected life expectancy, PCD-CT led to an average cost saving of $794.50 ± 18.50 per patient and an overall cost difference of $11,917,500 ± 4,350,169.
Conclusion: PCD-CT has the potential to reduce the financial burden on healthcare systems and procedure-related complications for stable chest pain patients with coronary calcification when compared to EID-CT.
Limitations: Limited number of lesions included.
Funding for this study: The study was funded by a research grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Local Ethics Committee approved the present study.

Author Block: G. Tremamunno¹, M. Vecsey-Nagy¹, M. T. Hagar¹, U. J. Schoepf¹, J. O'Doherty¹, J. A. Luetkens², A. Varga-Szemes¹, T. S. Emrich¹, D. Kravchenko¹; ¹Charleston, SC/US, ²Bonn/DE
Purpose: Pericoronary adipose tissue (PCAT) fat attenuation index (FAI) predicts major adverse cardiac events, but is known to be influenced by multiple factors, such as kernel sharpness, slice thickness, and tube potential. The objective of this study was to explore intra-individual differences in PCAT FAI between PCD- and energy-integrating detector (EID)-CT.
Methods or Background: Patients were prospectively enrolled for a PCD-CT research scan after EID coronary CT angiography. Reconstructions were performed using a Qr36 kernel at 0.6 mm slice thickness (EID and PCD-down-sampled [DS]) and at 0.2 mm ultra-high resolution (UHR) for the PCD-CT. Data was processed either with no use of iterative reconstruction, using a weighted filter back projection, or set to a strength level of Advanced Modeled Iterative Reconstruction 3 for the EID-CT and Quantum Iterative Reconstruction 4 for the PCD-CT. PCAT FAI of the right coronary artery (RCA), left anterior descending artery, and left circumflex artery (LCX) was measured automatically using established thresholds of -190 to -30 HU at a set distance and radius. Statistical testing was performed using repeated-measures ANOVA and Bonferroni’s multiple comparison tests (p<.003).
Results or Findings: 40 patients (mean age 68±8 years, 32 males [80%]) were analyzed. Absolute FAI measurements differed significantly for all vessels between all reconstructions in the ANOVA comparison (all p<.001). The mean FAI when using iterative reconstruction did not demonstrate significant differences on multiple comparisons (e.g. LCX: EID: -65.7±8.5; PCD-DS: -66.0±7.4; PCD-UHR: -67.8±7.0 HU, respectively; all p >.05).
Conclusion: Intra-individual absolute PCAT FAI measurements differ significantly between EID- and PCD-CT when controlling for reconstruction kernel and slice thickness. However, the use of iterative reconstruction minimizes most differences in FAI, enabling inter-scanner comparability.
Limitations: Small population size and not all patients underwent both examinations at the same tube potential.
Funding for this study: In part supported by a research grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: This HIPAA compliant single-center study received approval from the Institutional Review Board of the Medical University of South Carolina.

Author Block: G. Fahrni¹, S. A. Si-Mohamed², R. Wiemker³, D. C. Rotzinger¹, A. Houmeau², C. Prieur², P. C. Douek², S. Boccalini²; ¹Lausanne/CH, ²Lyon/FR, ³Hamburg/DE
Purpose: To assess the capabilities of first-pass myocardial perfusion imaging (MPI) with Spectral Photon Counting CT (SPCCT) Coronary Angiography to detect fractional-flow reserve (FFR) positive coronary artery stenoses, compared with dual-energy CT (DECT) in a very-high cardiovascular risk population.
Methods or Background: 18 very-high cardiovascular risk patients referred for CCTA after diagnostic invasive coronary angiography (ICA) were prospectively included (15 men, 3 women). ECG-gated CCTA was performed with DECT (IQon CT and CT7500, Philips Healthcare) and SPCCT (Philips clinical SPCCT prototype, Philips Healthcare), within 3 days. First-pass perfusion images were reconstructed with high-resolution (DECT) and ultra-high-resolution (SPCCT) parameters. Myocardial territories were visually labelled as normal or showing hypoperfusion. These labels were then compared to hemodynamic positivity on diagnostic ICA, indicated by either by significant stenosis (>70%) or FFR-positive stenosis. Myocardial attenuation was measured in normal and hypoperfusion territories.
Results or Findings: A total of 54 coronary artery territories were included. At ICA, significant stenosis was found in 15 (26%) arteries (8 LAD, 3 CX, 4 RCA). 11 lesions were significant stenoses, 4 were FFR-positive. Seventeen (31%) coronary artery territories were labelled as hypoperfusion for DECT and 18 (33%) for SPCCT. There was a significant difference between normal and hypoperfusion segments both for DECT (mean: 97±43 HU versus 80±35 HU, p<0.001) and SPCCT (mean: 92±86 HU versus 76±74 HU, p<0.001). A sensitivity for hemodynamically significant stenoses detection of 73% and specificity of 69% were found for DECT, versus 60% ad 72% for SPCCT.
Conclusion: In very-high cardiovascular risk population, SPCCT first-pass myocardial perfusion imaging was comparable to DECT in detecting myocardial hypoperfusion in significant or FFR-positive coronary artery stenosis territories.
Limitations: Small cohort of patients and predominance of LAD lesions.
Funding for this study: This work was supported by the European Union Horizon 2020 grant No. 643694.
G.F. is supported by a research grand from the Swiss Society of Radiology (SSR, Luzern, Switzerland) and Lausanne University hospital (CHUV, Lausanne, Switzerland).
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Hospices Civils de Lyon, approval number: 2019-A02945–52, SPEQUA study

Author Block: V. Mergen, N. Ehrbar, L. J. Moser, R. Manka, H. Alkadhi, M. Eberhard; Zurich/CH
Purpose: To evaluate the accuracy of myocardial extracellular volume (ECV) calculation using a synthetic hematocrit derived from virtual non-iodine images (VNI) and virtual non-contrast images (VNC) with photon-counting detector (PCD) CT.
Methods or Background: In this retrospective study, 125 consecutive patients examined by a PCD coronary CT angiography (CCTA) and a cardiac late enhancement (LE) scan, and having a recent blood hematocrit were included. In the derivation cohort (first 75 patients), CCTA and LE scans were reconstructed as VNI at 60, 70, and 80keV and as VNC with quantum iterative reconstruction (QIR) strengths 2, 3, and 4. Mean blood pool attenuation (BPmean) was correlated to the blood hematocrit. In the validation cohort (next 50 patients), BPmean served to calculate a synthetic hematocrit. Myocardial ECV was computed using the synthetic hematocrit and compared with the ECV using the blood hematocrit as reference.
Results or Findings: In the derivation cohort (49 men, mean age 79±8 years, mean BMI 26±5 kg/m2), correlation between BPmean and blood hematocrit ranged from poor for VNI of CCTA at 80keV, QIR2 (R2=0.12) to moderate for VNI of LE at 60keV, QIR4; 70keV, QIR3 and 4; and VNC of LE, QIR3 and 4 (all, R2=0.58). In the validation cohort (29 men, age 75±14 years, mean BMI 26±5 kg/m2), BPmean from VNC of the LE scan with QIR3 served to calculate the synthetic hematocrit. Median ECV was 26.9% (interquartile range (IQR), 25.5%,28.8%) using the blood hematocrit and 26.8% (IQR, 25.4%,29.7%) using the synthetic hematocrit (VNC, QIR3; mean difference,-0.2%; limits of agreement,-2.4%,2.0%; p=0.33).
Conclusion: Myocardial ECV calculation with PCD-CT, using a synthetic hematocrit derived from VNC images, enables accurate ECV measurements.
Limitations: Limited number of patients and lack of comparison with the clinical reference standard cardiac MRI
Funding for this study: None
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Kantonale Ethikkommission Zürich

Author Block: A. Clemente, A. Marcucci, C. De Gori, M. Occhipinti, M. Muca, F. Pignatelli, D. Cioni, E. Neri; Pisa/IT
Purpose: Cardiac amyloid deposition causes interstitial expansion, thereby increasing myocardial extracellular volume (ECV). The need for quantification of amyloid burden in transthyretin-related cardiac amyloidosis (TTR-CA) is currently met in part through semi-quantitative bone scintigraphy or with measurement of ECV through Cardiovascular Magnetic Resonance(CMR). Although Photon-counting CT (PCCT) provides comprehensive spectral data with every acquisition of the heart, to date few studies analysed ECV in cardiac amyloidosis by using it.
We evaluated the accuracy of extracellular volume (ECV) quantification with PCCT in TTR-CA.
Methods or Background: We prospectively enrolled 15 patients referred to our centre for suspected cardiac amyloidosis and atypical symptoms who underwent a complete diagnostic work-out including bone scintigraphy and PCCT. Iodine maps were created by using multienergy late scan. Volumetric ROIs of at least 2 cm3 were manually positioned using a 17 segments model of the left ventricle and global ECV was calculated as average of all segments. Then, the study population was divided into TTR-CA cases and non-amyloid heart disease cases (NCA).
Results or Findings: One patient was excluded due to light chain (AL) amyloidosis. Among the 14 patients included (77 years±5;10 men) 7 were diagnosed with TTR-CA. All TTR-CA cases showed positive scintigraphy (Perugini score ≥2), except for one, where the diagnosis was made through fat tissue biopsy and consistent cardiac CMR findings.
Global ECV was significantly higher in patients with TTR-CA (40.50±8.97%) than in NCA patients (27.00±3.03%;P<0.01). The accuracy of myocardial global ECV to identify occult TTR-CA was high (AUC=0.87; 95%CI, 0.65-1.00).
Conclusion: Preliminary results on myocardial tissue characterization based on ECV quantification with PCCT iodine maps show this is a promising method to detect TTR-CA.
Limitations: Preliminary results with small sample.
Funding for this study: No funding received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: No

Author Block: G. Tremamunno¹, A. Varga-Szemes², D. Kravchenko³, A. Laghi¹, F. Bamberg⁴, M. Vecsey-Nagy⁵, T. S. Emrich⁶, M. T. Hagar⁴; ¹Rome/IT, ²Charleston, SC/US, ³Bonn/DE, ⁴Freiburg im Breisgau/DE, ⁵Budapest/HU, ⁶Mainz/DE
Purpose: To assess the feasibility and determine the diagnostic accuracy of iodine maps from photon-counting detector (PCD) CT in detecting and characterizing myocardial late enhancement (LE), compared to late gadolinium enhancement (LGE) MRI.
Methods or Background: This IRB-approved retrospective analysis of a prospective study cohort included subjects who underwent cardiac MRI followed by late iodine enhancement (CT-LE) using a PCD-CT system (NAEOTOM Alpha, Siemens Healthineers). CT-LE scans were performed 5 minutes after administering 100 mL of contrast media (Ultravist, 370 mg I/mL; Bayer Healthcare) with an ECG-triggered sequential protocol, and full spectral capabilities. Iodine maps were reconstructed at a section thickness of 1.0 mm, using a quantitative kernel (Qr40), and iterative reconstruction (QIR level 3). Two blinded and independent radiologists interpreted all images. Diagnostic accuracy was evaluated per-patient and per-segment using LGE-MRI as the standard of reference. Inter-reader agreement was assessed with Cohen’s kappa.
Results or Findings: The final cohort comprised 27 patients (52% female, mean age 52.9 ± 17.2 years). Twelve patients (44%) had positive LGE on MRI (3 ischemic, 9 non-ischemic). Per-patient sensitivity was 100% and 91.7%, with specificities of 73.3% and 80.0%, and accuracies of 85.2%, respectively for both readers. Per-segment sensitivity was 74.7% and 66.7%, with specificities of 94.9% and 96.4%, and accuracies of 91.1% and 90.7%. Cohen’s kappa was 0.70 (patient level) and 0.63 (segment level), respectively.
Conclusion: Iodine maps from PCD-CT provide high diagnostic accuracy for myocardial LE detection with substantial inter-reader agreement. PCD-CT may serve as an alternative to LGE-MRI in selective cases, such as a contraindication to MRI or anxiety.
Limitations: Our study's limited sample size mandates confirmatory research. Our study design introduces a selection bias, so further studies are needed to evaluate the diagnostic role across diverse patient populations.
Funding for this study: This study was partially supported by an unrestricted research grant from Siemens Healthineers.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study protocol, compliant with the Health Insurance Portability and Accountability Act, received approval from the local institutional review board at the respective academic medical center, and all subjects provided written informed consent.

Author Block: S. Araki, S. Nakamura, M. Takafuji, Y. Ichikawa, H. Sakuma, K. Kitagawa; Tsu/JP
Purpose: Photon-counting detector computed tomography (PCD-CT), which allows for the exclusion of electronic noise, shows promise for significant dose reduction in coronary computed tomography angiography (CCTA). This study aimed to assess the radiation dose and image quality of CCTA using PCD-CT, combined with electrocardiogram (ECG)-triggered prospective high-pitch helical scanning and an ultra-low tube potential of 70 kVp and to investigate the effect of a sharp kernel on image quality and stenosis assessment in such an ultra-low dose CCTA setting.
Methods or Background: Forty patients (65% male) with stable heart rates and no prior coronary interventions were included. Data on CT dose index volume (CTDIvol) and dose-length product (DLP) were collected, with effective radiation dose estimated using a conversion factor of 0.014. Images were reconstructed using kernels of Bv64 and Bv40 for image quality and stenosis assessment.
Results or Findings: The mean CTDIvol, DLP, and effective dose of CCTA were 1.72±0.38 mGy, 29.1±6.8 mGy·cm, and 0.41±0.09 mSv, respectively. Image quality was similar (p=0.75) between the two kernels, with over 95% of segments achieving a rating of good image quality for both kernels. Additionally, 42% of non-calcified plaques showed an increased stenosis severity from Bv40 to Bv64 (p<0.001), while 25% of calcified plaques exhibited a decreased severity (p<0.001).
Conclusion: PCD-CT technology with ECG-triggered prospective high-pitch helical scanning and the tube potential of 70kVp can provide CCTA with ultra-low radiation exposure (0.4 mSv), offering a safer and more effective method for diagnosing coronary artery disease. The noise reduction capability of PCD-CT allows the use of a sharp kernel even in this low-dose CCTA setting without compromising image quality, potentially improving the evaluation of coronary artery stenosis.
Limitations: There is no reference standard such as coronary angiography.
Funding for this study: No funding was provided for this study
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Clinical Research Ethics Review Committee of Mie University Hospital (approval No. H2019-207)

Author Block: C. Mayard, S. A. Si-Mohamed, A. Houmeau, L. Boussel, P. C. Douek, S. Boccalini; Lyon/FR
Purpose: To assess the benefits of photon counting CT (PCCT) on image quality of cardiac valves as compared to conventional CT (conv-CT).
Methods or Background: Patients were prospectively included to undergo a clinically indicated coronary CT angiography with PCCT and conv-CT within three days. All the components of each valve were subjectively scored by two observers with a 4-point scale for sharpness and conspicuity. The number of nodules and of mitral chordae was noted. The number and the localisation of the calcifications relative to the thickness of the aortic leaflets were assessed. Furthermore, the full width at mid weight (FWMH) of the attenuation profile of a line perpendicular to the commissure between the left and right coronary cusps of the aortic valve was calculated.
Results or Findings: Thirty-three patients were included (88% men; 62±13 years). 33 pairs of aortic and mitral valves and 18 pairs of pulmonary valves could be analysed. Conspicuity of aortic, mitral, and pulmonary valvular structures was increased with PCCT except for one commissure of the aortic and pulmonary valves (p=0.06 and p=0.07). Sharpness was superior for all structures of the aortic and mitral valves, and for 2/3 edges of the pulmonary valve. More fine structures (nodules, chordae) and calcifications of the aortic and mitral valves were visible with PCCT. The precise localisation of the calcifications could be assessed with PCCT in most cases while it remained doubtful in many cases with conv-CT (p=0.02). FWMH was lower with PCCT (1.7(IQ=1.1) vs 2.5mm (IQ=1.3); p<0.01). The radiation dose was lower with PCCT (567.8 ±67.7 vs 681.8 ±159.6 mGy*cm; p<0.01).
Conclusion: PCCT yielded better objective and subjective image quality of cardiac valves as compared to conv-CT and more components of the valve structures were visible.
Limitations: Small cohort
Funding for this study: European grant H2020
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Approved