Dual-source Scanner Research Articles

Computed tomography-derived myocardial extracellular volume as a prognosis predictor in patients with severe aortic stenosis

Abstract Background Patients with severe aortic stenosis (AS) face a higher risk of mortality, but prognosis is still heterogeneous and tools for prioritizing intervention are needed. Myocardial extracellular volume (ECV), measured non-invasively in pre-TAVR computed tomography (CT), is a marker of fibrosis that may reflect the degree of irreversible damage. The aim of this study was to assess the prognostic value of CT- derived ECV (ECVCT) in patients with severe AS referred for TAVR-planning CT. Methods Consecutive patients with severe symptomatic AS undergoing TAVR-planning CT between April and December 2022 at single centre were prospectively included. CT was performed on a 192-slice dual-source 3rdgeneration scanner. ECVCT was acquired during TAVR-planning using an additional post-contrast low-radiation-dose prospective acquisition. ECVCT was calculated as the ratio of change in CT attenuation (Hounsfield units [HU]) of the septal myocardium and the left ventricle (LV) blood pool before and after contrast administration, according to the equation: ECVCT = (1 – hematocrit) x (DHUmyo/DHUblood) – Figure 1A. The primary endpoint was all-cause mortality. The secondary endpoint was a composite endpoint including all-cause mortality and heart failure hospitalization. Results A total of 138 patients were included (mean age 81 ± 7 years; 46% male; mean transaortic gradient 51 ± 15 mmHg; mean aortic valvearea 0.75 ± 0.19 cm2; mean LV ejection fraction (EF) by 2D echocardiogram 57 ± 11%). No patient had a clinical diagnosis of cardiac amyloidosis. Mean ECVCT was 33.9 ± 8.0%. During a median follow-up period of 386 days (IQR 332 – 464), there were 18 deaths (13%), 13 before intervention and 5 after intervention; the secondary endpoint occurred in 26 patients (19%), 17 of which before intervention and 9 after. Patients who attained the primary endpoint were significantly older [81 ± 7 vs. 85 ± 7 years, P = 0.011], had lower left ventricular ejection fraction [51 ± 11 vs. 58 ± 11%, P = 0.015], higher NTproBNP levels [4739 (IQR 2003 – 9970) vs. 751 (IQR 314 – 2541), P <0.001] and higher ECV values (39.9 ± 7.4% vs. 33.0 ± 7.7%, P <0.001). After adjustment for age, LVEF and NTproBNP levels, ECVCT remained an independent predictor of all-cause mortality (adjusted HR 1.09 per 1% ECV increase, 95%CI 1.02 – 1.17, p=0.005 – Figure 1B) and also the secondary endpoint (adjusted HR 1.07 per 1% ECV increase, 95%CI 1.01 – 1.13, p=0.002). Conclusions In this prospective observational cohort study, interstitial fibrosis assessed by CT-derived ECV was associated with poor outcomes in patients with severe AS. ECVCT values may be useful to identify a subgroup of patients with higher risk who may benefit from earlier intervention.

Evaluating small coronary stents with dual-source photon-counting computed tomography: effect of different scan modes on image quality and performance in a phantom.

The study aimed to assess the feasibility and image quality of dual-source photon-counting detector computed tomography (PCD-CT) in evaluating small-sized coronary artery stents with respect to different acquisition modes in a phantom model. Utilizing a phantom setup mimicking the average patient's water-equivalent diameter, we examined six distinct coronary stents inflated in a silicon tube, with stent sizes ranging from 2.0 to 3.5 mm, applying four different CT acquisition modes of a dual-source PCD-CT scanner: "high-pitch," "sequential," "spiral" (each with collimation of 144 × 0.4 mm and full spectral information), and "ultra-high-resolution (UHR)" (collimation of 120 × 0.2 mm and no spectral information). Image quality and diagnostic confidence were assessed using subjective measures, including a 4-point visual grading scale (4 = excellent; 1 = non-diagnostic) utilized by two independent radiologists, and objective measures, including the full width at half maximum (FWHM). A total of 24 scans were acquired, and all were included in the analysis. Among all CT acquisition modes, the highest image quality was obtained for the UHR mode [median score: 4 (interquartile range (IQR): 3.67-4.00)] (P = 0.0015, with 37.5% rated as "excellent"), followed by the sequential mode [median score: 3.5 (IQR: 2.84-4.00)], P = 0.0326 and the spiral mode [median score: 3.0 (IQR: 2.53-3.47), P > 0.05]. The lowest image quality was observed for the high-pitch mode [median score: 2 (IQR: 1- 3), P = 0.028]. Similarly, diagnostic confidence for evaluating stent patency was highest for UHR and lowest for high-pitch (P < 0.001, respectively). Measurement of stent dimensions was accurate for all acquisition modes, with the UHR mode showing highest robustness (FWHM for sequential: 0.926 ± 0.061 vs. high-pitch: 0.990 ± 0.083 vs. spiral: 0.962 ± 0.085 vs. UHR: 0.941 ± 0.036, P = non-significant, respectively). Assessing small-sized coronary stents using PCD-CT technology is feasible. The UHR mode offers superior image quality and diagnostic confidence, while all modes show consistent and accurate measurements. These findings highlight the potential of PCD-CT technology, particularly the UHR mode, to enhance non-invasive coronary stent evaluation. Confirmatory research is necessary to influence the guidelines, which recommend cardiac CT only for stents of 3 mm or larger.

Impact of an institutional process change adopting end-systolic coronary CTA acquisition and automated dose selection on patient throughput and image quality

IntroductionGuidelines recommend prospective ECG-triggered mid-diastolic coronary computed tomographic angiography (CCTA) acquisition after achieving optimal heart rate (HR) control in order to optimize scan image quality. With dual-source CCTA, prospective end-systolic acquisition has been shown to be less prone to motion artifacts at higher heart rates and may improve scan and CT laboratory efficiency by allowing CCTA without routine pre-scan beta-blocker (BB) administration. MethodsWe implemented an institutional process change in CCTA performance effective January 2023, comprising a transition from prospective ECG-triggered mid-diastolic acquisitions individually supervised by a physician at the scanner to an algorithmic approach predominately utilizing prospective end-systolic acquisition (200–400 ​ms after R peak), employing an automated dose selection algorithm, without BB administration. All scans were performed on a third-generation 192-slice dual-source scanner. We reviewed 300 consecutive CCTAs done pre- and post-process change in Jan 2022 (phase 0), Jan 2023 (phase 1), and in May 2023 (phase 2) after implementation of a process improvement involving more selective utilization of automated tube potential/current algorithms (CARE kV) to optimize image quality. Coronary segmental image quality was assessed by two experienced CCTA readers by consensus using an 18-segment SCCT model on a 5-point Likert scale (1 ​= ​non-interpretable; 2 ​= ​poor; 3 ​= ​acceptable; 4 ​= ​good; 5 ​= ​excellent). Measures of radiation dose, medication administration, and time required for patient scanning were compared. Logistic regression was used to determine factors associated with patient-level reduction in image quality (IQ) and with repeat scans. ResultsPost-process change, there was a significant reduction in the median overall patient appointment [phase 0: 95 (75–125) min vs. phase 1: 68 (52–88) min and phase 2: 72 (59–90) min; P ​< ​0.001] and scan times [phase 0: 13 (10–16) min vs. phase 1: 8 (6–13) min and phase 2: 9 (7–13) min; P ​< ​0.001]. Median IQ score in both post-process change phases was 4 (4–5) compared to a median score of 5 (4–5) pre-process change (P for comparison <0.001). The majority of segments post-process change had “good” IQ (Phase 1 segmental IQ scores: 5 ​= ​36.7 ​%, 4 ​= ​46.8 ​%, 3 ​= ​13 ​%, 2 ​= ​2.6 ​%, 1 ​= ​0.9 ​%; Phase 2 segmental IQ scores: 5 ​= ​26 ​%, 4 ​= ​49.7 ​%, 3 ​= ​16.3 ​%, 2 ​= ​6.1 ​%, 1 ​= ​1.9 ​%), whereas pre-process change, the majority of segments had “excellent” IQ (Phase 0 segmental IQ scores: 5 ​= ​56 ​%, 4 ​= ​34.3 ​%, 3 ​= ​7.5 ​%, 2 ​= ​1.8 ​%, 1 ​= ​0.4 ​%) There was no significant increase in non-interpretable scans at the patient level. The 22 ​% re-scan rate in phase 1 (vs. 6 ​% in phase 0, P ​= ​.002) improved to 15 ​% in phase 2. While patient related factors of body mass index [adjusted OR obese 2.64, 95 ​% CI 1.12–6.51, P ​= ​0.03; aOR morbidly obese 6.94, 95 ​% CI 2.21–23.52, P ​= ​0.001] and average HR [aOR (per 10 bpm increase) 1.51, 95 ​% CI 1.21–1.9, P ​< ​0.001] were associated with the scoring of any segment as ​≤ ​3 ​at the patient level in a fully adjusted model, the improved phase 2 of the process change was not [aOR 1.61, 95 ​% CI 0.78–3.32]. ConclusionImplementation of an institutional process change utilizing prospective ECG-triggered dual-source end-systolic acquisition avoided the use of beta-blockers, significantly reduced patient appointment and scan times with acceptable diagnostic performance.

Combined Computed Coronary Tomography Angiography and Transcatheter Aortic Valve Implantation (TAVI) Planning Computed Tomography Reliably Detects Relevant Coronary Artery Disease Pre-TAVI.

Background: Before surgical or transcatheter aortic valve implantation (TAVI), coronary status evaluation is required. The role of combined computed coronary tomography angiography (cCTA) and TAVI planning CT in this context is not yet well elucidated. This study assessed whether relevant proximal coronary disease requiring coronary revascularization can be safely detected by combined cCTA and TAVI planning CT, including CT-derived fractional flow reserve (FFR) calculation in patients with severe aortic stenosis. Methods: This study analyzed patients with successful cCTA combined with TAVI planning CT using a 128-slice dual-source scanner. The detection via cCTA of relevant left main stem stenosis (>50%) or proximal coronary artery stenosis (>70%) was compared to invasive coronary angiography (ICA). Results: This study comprised 101 consecutive TAVI patients with a median age of 83 [77-86] years, a median STS score of 3.7 [2.4-6.1] and 54% of whom had known coronary artery disease. Of 15 patients with relevant coronary stenoses, 14 (93.3%) were detected with cCTA, while false positive results were found in 25 patients. Only in patients with previous percutaneous coronary stent implantation (PCI) were false positive rates (11/29) increased. In the subgroup without previous PCI, an improved classification performance of 87.5%, being mainly due to 11.1% false positive classifications, led to a negative predictive value of 98.5%. Conclusions: Combined cCTA and CT-FFR with TAVI planning CT via state-of-the-art scanners and protocols as a one-stop shop can replace routine ICA in patients prior to TAVI due to its safe detection of relevant coronary artery stenosis, although diagnostic performance of cCTA is only reduced in patients with coronary stents.

Accuracy of a deep learning-based algorithm for the detection of thoracic aortic calcifications in chest computed tomography and cardiovascular surgery planning.

To assess the accuracy of a deep learning-based algorithm for fully automated detection of thoracic aortic calcifications in chest computed tomography (CT) with a focus on the aortic clamping zone. We retrospectively included 100 chest CT scans from 91 patients who were examined on second- or third-generation dual-source scanners. Subsamples comprised 47 scans with an ECG-gated aortic angiography and 53 unenhanced scans. A deep learning model performed aortic landmark detection and aorta segmentation to derive eight vessel segments. Associated calcifications were detected and their volumes measured using a mean-based density thresholding. Algorithm parameters (calcium cluster size threshold, aortic mask dilatation) were varied to determine optimal performance for the upper ascending aorta that encompasses the aortic clamping zone. A binary visual rating served as a reference. Standard estimates of diagnostic accuracy and inter-rater agreement using Cohen's Kappa were calculated. Thoracic aortic calcifications were observed in 74% of patients with a prevalence of 27% to 70% by aorta segment. Using different parameter combinations, the algorithm provided binary ratings for all scans and segments. The best-performing parameter combination for the presence of calcifications in the aortic clamping zone yielded a sensitivity of 93% and a specificity of 82% with an area under the receiver operating characteristic curve of 0.874. Using these parameters, the inter-rater agreement ranged from κ 0.66 to 0.92 per segment. Fully automated segmental detection of thoracic aortic calcifications in chest CT performs with high accuracy. This includes the critical preoperative assessment of the aortic clamping zone.

Image quality in CT thorax: effect of altering reconstruction algorithm and tube load.

Non-linear properties of iterative reconstruction (IR) algorithms can alter image texture. We evaluated the effect of a model-based IR algorithm (advanced modelled iterative reconstruction; ADMIRE) and dose on computed tomography thorax image quality. Dual-source scanner data were acquired at 20, 45 and 65 reference mAs in 20 patients. Images reconstructed with filtered back projection (FBP) and ADMIRE Strengths 3-5 were assessed independently by six radiologists and analysed using an ordinal logistic regression model. For all image criteria studied, the effects of tube load 20 mAs and all ADMIRE strengths were significant (p<0.001) when compared to reference categories 65 mAs and FBP. Increase in tube load from 45 to 65 mAs showed image quality improvement in three of six criteria. Replacing FBP with ADMIRE significantly improves perceived image quality for all criteria studied, potentially permitting a dose reduction of almost 70% without loss in image quality.

Towards safer imaging: A comparative study of deep learning-based denoising and iterative reconstruction in intraindividual low-dose CT scans using an in-vivo large animal model

PurposeComputed tomography (CT) scans are a significant source of medically induced radiation exposure. Novel deep learning-based denoising (DLD) algorithms have been shown to enable diagnostic image quality at lower radiation doses than iterative reconstruction (IR) methods. However, most comparative studies employ low-dose simulations due to ethical constraints. We used real intraindividual animal scans to investigate the dose-reduction capabilities of a DLD algorithm in comparison to IR. Materials and methodsFourteen veterinarian-sedated alive pigs underwent 2 CT scans on the same 3rd generation dual-source scanner with two months between each scan. Four additional scans ensued each time, with mAs reduced to 50 %, 25 %, 10 %, and 5 %. All scans were reconstructed ADMIRE levels 2 (IR2) and a novel DLD algorithm, resulting in 280 datasets. Objective image quality (CT numbers stability, noise, and contrast-to-noise ratio) was measured via consistent regions of interest. Three radiologists independently rated all possible dataset combinations per time point for subjective image quality (−1 = inferior, 0 = equal, 1 = superior). The points were averaged for a semiquantitative score, and inter-rater agreement was measured using Spearman's correlation coefficient and adequately corrected mixed-effects modeling analyzed objective and subjective image quality. ResultsNeither dose-reduction nor reconstruction method negatively impacted CT number stability (p > 0.999). In objective image quality assessment, the lowest radiation dose achievable by DLD when comparing noise (p = 0.544) and CNR (p = 0.115) to 100 % IR2 was 25 %. Overall, inter-rater agreement of the subjective image quality ratings was strong (r ≥ 0.69, mean 0.93 ± 0.05, 95 % CI 0.92–0.94; each p < 0.001), and subjective assessments corroborated that DLD at 25 % radiation dose was comparable to 100 % IR2 in image quality, sharpness, and contrast (p ≥ 0.281). ConclusionsThe DLD algorithm can achieve image quality comparable to the standard IR method but with a significant dose reduction of up to 75%. This suggests a promising avenue for lowering patient radiation exposure without sacrificing diagnostic quality.

Anomalous Origin of Left Circumflex Artery from the Right Sinus of Valsalva in Cardiac Computed Tomography in a Group of 16,680 Patients—Radiologic and Clinical Characteristics

Background: Anomalous aortic origin of a coronary artery (AAOCA) is the most prevalent form of coronary anomaly. One variant of AAOCA is the anomalous origin of the left circumflex artery from the right sinus of Valsalva, which can be detected using cardiac computed tomography (CT). However, limited data are available regarding the natural history of this anomaly, its impact on myocardial function, and associated symptoms. Methods: We conducted a retrospective analysis of 16,680 CT exams (cardiac and chest) performed between 2015 and 2022 at our Heart Imaging Department, utilising a dual-source 128-slice CT scanner (SOMATOM Definition Flash, Siemens Healthineers, Forchheim, Germany). A registry of patients with anomalous origin of the circumflex artery from the right sinus of Valsalva (RCx) was established. The study included 56 cases of RCx (0.33%). Clinical information was obtained from medical records. RCx was defined as a circumflex artery originating from the right sinus of Valsalva (type I or II) or the right coronary artery (type III). Two researchers independently reevaluated each CT exam in our study group to ensure accurate radiologic descriptions and provide additional precise radiologic information regarding the anomaly, including high-risk features. Results: Our study comprised 56 patients, with approximately equal distribution between males (n = 30, 54%) and females (n = 26, 46%), and with a median age of 59 years. Coronary heart disease (CAD) was known in 23% of patients (n = 13), while 11% (n = 6) were obese (defined as a BMI &gt; 30 kg/m2), and 13% (n = 7) were diagnosed with type 2 diabetes. Only 9% of patients (n = 5) were smokers. Dyslipidemia was the most prevalent atherosclerotic risk factor, affecting approximately one third of patients (n = 17, 30%). In 14% (n = 8) of patients, heart failure was observed, while 13% (n = 7) were diagnosed with atrial fibrillation. Type I RCx was the most common subtype, identified in 48% of patients (n = 27) with this anomaly. Type II and Type III were found in 25% (n = 14) and 27% (n = 15) of patients, respectively. Conclusions: Our findings suggest that RCx is frequently encountered as an incidental finding, and we did not identify a consistent clinical characteristic in all patients with this type of anomaly. Furthermore, no gender predominance was associated with RCx. The natural history of this anomaly and its clinical implications seem benign. Further research is warranted to better understand this anomaly’s natural course and clinical implications.

Abstract 13323: Impact of an Institutional Process Change Adopting End-Systolic Coronary CTA Acquisition on Patient Throughput and Image Quality

Introduction: Prospective ECG-triggered end-systolic coronary computed tomographic angiography (CCTA) acquisition is less prone to motion artifacts with arrhythmias and high heart rates, and with increasing utilization, has the potential to improve scan and CT laboratory efficiency by reducing the need for IV/oral beta-blockers (BB) prior to the scan. Methods: We implemented an institutional process change in CCTA performance effective January 2023, transitioning from prospective ECG-triggered mid-diastolic acquisitions supervised by a physician at the scanner to an algorithmic approach with prospective end-systolic acquisition (200-400 ms after R peak) without BB administration, all on 3 rd -generation 192 slice dual-source scanners. We reviewed 100 consecutive CCTAs done pre- and post-process change in Jan 2022 and Jan 2023. Two experienced CCTA readers assessed segmental image quality by consensus using an 18-segment SCCT model on a 5-point Likert scale (1=non-interpretable; 2=poor; 3=satisfactory; 4=good; 5=excellent). Results: Post-process change, median overall patient appointment [94 (78 - 127) min vs. 69 (53 - 86) min; P &lt; 0.001] and scan times [12 (10 - 16) min vs. 7 (6 - 9) min; P &lt;.001] were significantly lower, and patient throughput doubled [2 (2 - 3)/day vs. 4 (3 - 6)/day; P =.024]. Median segmental image quality score decreased from excellent to good [5 (4 - 5) vs. 4 (4 - 5); P &lt;.001], with a decrease in signal-noise ratio [23.5 (18 - 28.8) vs. 11.8 (8.7 - 14.7); P &lt;.001], and no significant difference in poor or non-interpretable segments in the end-systolic cohort. More scans were repeated with end-systolic scans (10% vs. 18%), with no significant change in radiation dose (Table 1). Conclusion: Utilizing prospective ECG-triggered end-systolic acquisition avoided the use of BB, significantly reduced scan times, doubled patient throughput, at similar radiation doses, and maintained diagnostic performance with only a mild compromise in image quality.

Dual energy CT reconstruction using the constrained one step spectral image reconstruction algorithm.

The constrained one-step spectral CT Image Reconstruction method (cOSSCIR) has been developed to estimate basis material maps directly from spectral CT data using a model of the polyenergetic x-ray transmissions and incorporating convex constraints into the inversion problem. This 'one-step' approach has been shown to stabilize the inversion in the case of photon-counting CT, and may provide similar benefits to dual-kV systems that utilize integrating detectors. Since the approach does not require the same rays be acquired for every spectral measurement, cOSSCIR can apply to dual energy protocols and systems used clinically, such as fast and slow kV switching systems and dual sourcescanning. The purpose of this study is to investigate the use of cOSSCIR applied to dual-kV data, using both registered and unregistered spectral acquisitions, specifically slow and fast kV switching imaging protocols. For this application, cOSSCIR is investigated using inverse crime simulations and dual-kV experiments. This study is the first demonstration of cOSSCIR on the dual-kV reconstructionproblem. An integrating detector model was developed for the purpose of reconstructing dual-kV data, and an inverse crime study was used to validate the detector model within the cOSSCIR framework using a simulated pelvic phantom. Experiments were also used to evaluate cOSSCIR on the dual energy problem. Dual-kV data was obtained from a physical phantom containing analogs of adipose, bone, and liver tissues, with the aim of recovering the material coefficients in the bone and adipose basis material maps. cOSSCIR was applied to acquisitions where all rays performed both spectral measurements (registered) and fast and slow kV switching acquisitions (unregistered). cOSSCIR was also compared to two image-domain decomposition approaches, where image-domain methods are the conventional approach for decomposing unregistered spectraldata. Simulations demonstrate the application of cOSSCIR to the dual-kV inversion problem by successfully recovering the material basis maps on ideal data, while further showing that unregistered data presents a more challenging inversion problem. In our experimental reconstructions, the recovered basis material coefficient errors were found to be less than 6.5% in the bone, adipose, and liver regions for both registered and unregistered protocols. Similarly, the errors were less than 4% in the 50 keV virtual mono-energetic images, and the recovered material decomposition vectors nearly overlap their corresponding ground-truth vectors. Additionally, a preliminary two material decomposition study of iodine quantification recovered an average concentration of 9.2 mg/mL from a 10 mg/mL experimental iodineanalog. Using our integrating detector and spectral models, cOSCCIR is capable of accurately recovering material basis maps from dual-kV data for both registered and unregistered data. The material decomposition quantification compare favorably to the image domain approaches, and our results were not affected by the imaging protocol. Our results also suggest the extension of cOSSCIR to iodine quantification using two materialdecomposition.

75% radiation dose reduction using deep learning reconstruction on low-dose chest CT

ObjectiveFew studies have explored the clinical feasibility of using deep-learning reconstruction to reduce the radiation dose of CT. We aimed to compare the image quality and lung nodule detectability between chest CT using a quarter of the low dose (QLD) reconstructed with vendor-agnostic deep-learning image reconstruction (DLIR) and conventional low-dose (LD) CT reconstructed with iterative reconstruction (IR).Materials and methodsWe retrospectively collected 100 patients (median age, 61 years [IQR, 53–70 years]) who received LDCT using a dual-source scanner, where total radiation was split into a 1:3 ratio. QLD CT was generated using a quarter dose and reconstructed with DLIR (QLD-DLIR), while LDCT images were generated using a full dose and reconstructed with IR (LD-IR). Three thoracic radiologists reviewed subjective noise, spatial resolution, and overall image quality, and image noise was measured in five areas. The radiologists were also asked to detect all Lung-RADS category 3 or 4 nodules, and their performance was evaluated using area under the jackknife free-response receiver operating characteristic curve (AUFROC).ResultsThe median effective dose was 0.16 (IQR, 0.14–0.18) mSv for QLD CT and 0.65 (IQR, 0.57–0.71) mSv for LDCT. The radiologists’ evaluations showed no significant differences in subjective noise (QLD-DLIR vs. LD-IR, lung-window setting; 3.23 ± 0.19 vs. 3.27 ± 0.22; P = .11), spatial resolution (3.14 ± 0.28 vs. 3.16 ± 0.27; P = .12), and overall image quality (3.14 ± 0.21 vs. 3.17 ± 0.17; P = .15). QLD-DLIR demonstrated lower measured noise than LD-IR in most areas (P < .001 for all). No significant difference was found between QLD-DLIR and LD-IR for the sensitivity (76.4% vs. 72.2%; P = .35) or the AUFROCs (0.77 vs. 0.78; P = .68) in detecting Lung-RADS category 3 or 4 nodules. Under a noninferiority limit of -0.1, QLD-DLIR showed noninferior detection performance (95% CI for AUFROC difference, -0.04 to 0.06).ConclusionQLD-DLIR images showed comparable image quality and noninferior nodule detectability relative to LD-IR images.

Minimizing Contrast Media Dose in CT Pulmonary Angiography with Clinical Photon Counting Using High Pitch Technique

To evaluate the potential to reduce the amount of iodinated contrast media (CM) for computer tomographic pulmonary angiography (CTPA) with a novel photon-counting-detector CT (PCCT). Overall, 105 patients referred for CTPA were retrospectively included in this study. CTPA was performed using bolus tracking and high-pitch dual-source scanning (FLASH mode) on a novel PCCT (Naeotom Alpha, Siemens Healthineers). CM (Accupaque 300, GE Healthcare) dose was lowered stepwise following the introduction of the new CT scanner. Thus, patients could be divided into 3 groups as follows: group 1, n=29, 35ml of CM; group 2, n=62, 45ml of CM and group 3, n=14, 60ml of CM. Four readers independently assessed the image quality (Likert-scale 1-5) and adequate assessment of the segmental pulmonary arteries. Additionally, the pulmonary arterial contrast opacification was measured. The subjective image quality was rated highest in group 1 with 4.6 compared to 4.5 (group 2) and 4.1 (group 3) with a significant difference between groups 1 and 3 (p<0.001) and between groups 2 and 3 (p=0.003). In all groups, almost all segmental pulmonary arteries could be assessed adequately without significant differences (18.5 vs. 18.7 vs. 18.4). Mean attenuation in the pulmonary trunk did not differ significantly between groups 321±92 HU versus 345±93 HU versus 347±88 HU (p=0.69). Significant CM dose reduction is possible without a reduction in image quality. PCCT enables diagnostic CTPA with 35ml of CM.

Computed tomography-derived myocardial extracellular volume in patients with severe aortic stenosis: correlation with markers of ventricular dysfunction

Abstract Funding Acknowledgements Type of funding sources: None. Background Myocardial fibrosis is a potential adverse prognostic marker in patients with severe aortic stenosis (AS) and can be quantified using non-invasive imaging measures, such as the extracellular volume fraction (ECV). Although computed tomography (CT) for transcatheter aortic valve replacement (TAVR) planning was originally developed to assess the aortic valve complex and access routes, it has evolved to include the measurement of ECV for myocardial tissue characterization. Aim This study aimed to determine associations between CT-derived ECV (ECVCT) and clinical and echocardiographic markers of ventricular function in patients with severe AS referred for TAVR-planning CT. Methods Single-center prospective study enrolling all consecutive patients with severe symptomatic AS referred for TAVR-planning CT between April and November 2022. CT was performed on a 192-slice dual-source 3rd generation scanner (Siemens Somatom Force) and ECVCT was acquired during TAVR-planning using an additional 5-minute post-contrast low-radiation-dose prospective acquisition. ECVCT was calculated as the ratio of change in CT attenuation (Hounsfield units [HU]) of the septal myocardium and the left ventricle (LV) blood pool before and after contrast administration, according to the equation: ECVCT = (1 – hematocrit) x (DHUmyo/DHUblood) – Figure 1A. Results A total of 102 patients were included (mean age 81 ± 7 years; 46% male; mean valvular transaortic gradient 51 ± 14 mmHg; mean aortic valve area 0.7 ± 0.2 cm2; mean LV ejection fraction (EF) by 2D echocardiogram 57 ± 11%). No patient had a clinical diagnosis of cardiac amyloidosis. Overall, the mean ECVCT value was 33.4 ± 7.0%. Myocardial ECVCT values significantly differed between AS subtypes, with higher values in patients with low-gradient AS (n=13, 13%; ECVCT 40.3 ± 4.8% vs 32.4 ± 6.7%, p&amp;lt;0.001) - Figure 1B. Additionally, myocardial ECVCT values correlated with markers of LV and right ventricular (RV) dysfunction, including lower LV EF (r = -0.354, p&amp;lt;0.001), worse LV global longitudinal strain (r = 0.420, p = 0.002), reduced TAPSE (r = -0.230, p = 0.043) and RV S wave by tissue doppler imaging (r = -0.321, p = 0.010) and higher NT-proBNP values (r = 0.347, p = 0.002). Conclusions In patients with severe AS scheduled for TAVR-planning CT, ECVCT values are significantly higher in those with low-gradient AS and correlated with several measures of biventricular dysfunction. This CT parameter may be useful to identify a subgroup of patients with higher risk of adverse prognosis.

Impact of tin filter on the image quality of ultra-low dose chest CT: A phantom study on three CT systems

PurposeThe purpose of this study was to assess the impact of a tin filter on the image quality of ultra-low dose (ULD) chest computed tomography (CT) on three different CT systems. Materials and methodsAn image quality phantom was scanned on three CT systems including two split-filter dual-energy CT (SFCT-1 and SFCT-2) scanners and one dual-source CT scanner (DSCT). Acquisitions were performed with a volume CT dose index (CTDIvol) of 0.4 mGy, first at 100 kVp without tin filter (Sn), and second, at Sn100/Sn140 kVp, Sn100/Sn110/Sn120/Sn130/Sn140/Sn150 kVp and Sn100/Sn150 kVp for SFCT-1, SFCT-2 and DSCT respectively. Noise-power-spectrum and task-based transfer function were computed. The detectability index (d’) was computed to model the detection of two chest lesions. ResultsFor DSCT and SFCT-1, noise magnitude values were higher with 100kVp than with Sn100 kVp and with Sn140 kVp or Sn150 kVp than with Sn100 kVp. For SFCT-2, noise magnitude increased from Sn110 kVp to Sn150 kVp and was higher at Sn100 kVp than at Sn110 kVp. For most kVp with the tin filter, the noise amplitude values were lower than those obtained at 100 kVp. For each CT system, noise texture and spatial resolution values were similar with 100 kVp and with all kVp used with a tin filter. For all simulated chest lesions, the highest d’ values were obtained at Sn100 kVp for SFCT-1 and DSCT and at Sn110 kVp for SFCT-2. ConclusionFor ULD chest CT protocols, the lowest noise magnitude and highest detectability values for simulated chest lesions are obtained with Sn100 kVp for the SFCT-1 and DSCT CT systems and at Sn110 kVp for SFCT-2.

Can You Reliably Achieve Diagnostic Image Quality in Morbidly Obese Patients Undergoing Computed Tomography Coronary Angiography?

There is concern about computed tomography coronary angiography (CTCA) image quality with the increasing numbers of obese and morbidly obese patients presenting with chest pain syndrome. This study evaluated the CTCA image quality in obese and morbidly obese patients in Counties Manukau, using a dual source scanner. Scan reports were prospectively collected using the All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) CT database between 1 January 2022 and 31 December 2022. Image quality was subjectively graded by the reporting cardiologist as good, average, or suboptimal at the time of scan. Coronary Artery Disease Reporting and Data System (CAD-RADS) score N (non-diagnostic) due to suboptimal image quality was collected. Patients were divided into three body mass index groups: 1) normal/overweight <30 kg/m2; 2) obese 30–40 kg/m2; 3) morbidly obese > 40 kg/m2. A total of 1,137 CTCA were performed. A total of 575 patients were normal/overweight and image quality was suboptimal in 10 (1.7%), average in 78 (13.6%), and good in 487 patients (84.7%); two patients had CAD-RADS-N due to suboptimal image quality. A total of 544 patients were obese and image quality was suboptimal in 16 (3.6%), average in 106 (23.9%), and good in 321 patients (72.5%); three patients had CAD-RADS-N due to suboptimal image quality. A total of 119 patients were morbidly obese and image quality was suboptimal in 10 (8.4%), average in 57 (47.9%), and good in 52 patients (43.7%); three patients had CAD-RADS-N due to suboptimal image quality. Although proportionately more morbidly obese patients were likely to have suboptimal CTCA image quality, diagnostic scans were obtained in almost all patients.

Optimization of chest CT protocols based on pixel image matrix, kernels and iterative reconstruction levels – A phantom study

IntroductionThis study investigated the impact of high matrix image reconstruction in combination with different reconstruction kernels and levels of iterative reconstructions on image quality in chest CT. MethodsAn anthropomorphic chest phantom (Kyoto Kagaku Co., Ltd., Kyoto, Japan), and a Catphan® 600 (The Phantom Laboratory, Greenwich, NY, USA) phantom were scanned using a dual source scanner. Standard institutional protocol with 512 × 512 matrix was used as a reference. Reconstructions were performed for 768 × 768 and 1024 × 1024 matrices and all possible combinations of three different kernels and five levels of iterative reconstructions were included. Signal difference to noise ratio (SdNR) and line pairs per cm (lp/cm) were manually measured. A Linear regression model was applied for objective image analysis (SdNR) and inter–and intra-reader agreement was given as Cohen's kappa for the visual image assessment. ResultsMatrix size did not have a significant impact on SdNR (p = 0.595). Kernel (p = 0.014) and ADMIRE level (p = 0.001) had a statistically significant impact on SdNR. The spatial resolution ranged from 7 lp/cm to 9 lp/cm. The highest spatial resolution was achieved using kernel Br64 and ADMIRE 1, 2 and 3 in both 768- and 1024-matrices, and with Br59 with ADMIRE 2 and 4 and 768-matrix, all visualizing 9 lp/cm. Both readers scored kernel Br59 highest, and the scoring increased with increasing levels of Iterative Reconstruction. ConclusionMatrix size did not influence image quality, however, the choice of kernel and degree of IR had an impact on objective and visual image quality in 768 - and 1024-matrices, suggesting that increased degree of IR may improve diagnostic image quality in chest CT. Implications for practiceImage quality in CT of the lung may be improved by increasing the level of IR.

The Importance of Temporal Resolution for Ultra-High-Resolution Coronary Angiography: Evidence From Photon-Counting Detector CT.

The aim of this study was to assess the effect of temporal resolution on subjective and objective image quality of coronary computed tomography angiography (CCTA) in the ultra-high-resolution (UHR) mode with dual-source photon-counting detector (PCD) CT. This retrospective, institutional review board-approved study evaluated 30 patients (9 women; mean age, 80 ± 10 years) undergoing UHR CCTA with a clinical dual-source PCD-CT scanner. Images were acquired with a tube voltage of 120 kV and using a collimation of 120 × 0.2 mm. Gantry rotation time was 0.25 seconds. Each scan was reconstructed using both single-source and dual-source data resulting in an image temporal resolution of 125 milliseconds and 66 milliseconds, respectively. The average heart rate and the heart rate variability were recorded. Images were reconstructed with a slice thickness of 0.2 mm, quantum iterative reconstruction strength level 4, and using the Bv64 and Bv72 kernel for patients without and with coronary stents, respectively. For subjective image quality, 2 experienced readers rated motion artifacts and vessel delineation, or in-stent lumen visualization using 5-point discrete visual scales. For objective image quality, signal-to-noise ratio, contrast-to-noise ratio, stent blooming artifacts, and vessel and stent sharpness were quantified. Fifteen patients had coronary stents, and 15 patients had no coronary stents. The mean heart rate and heart rate variability during data acquisition were 72 ± 10 beats per minute and 5 ± 6 beats per minute, respectively. Subjective image quality in the right coronary artery, left anterior descending, and circumflex artery was significantly superior in 66 milliseconds reconstructions compared with 125 milliseconds reconstructions for both readers (all P 's < 0.01; interreader agreement, Krippendorff α = 0.84-1.00). Subjective image quality deteriorated significantly at higher heart rates for 125 milliseconds (ρ = 0.21, P < 0.05) but not for 66 milliseconds reconstructions (ρ = 0.11, P = 0.22). No association was found between heart rate variability and image quality for both 125 milliseconds (ρ = 0.09, P = 0.33) and 66 milliseconds reconstructions (ρ = 0.13, P = 0.17), respectively. Signal-to-noise ratio and contrast-to-noise ratio were similar between 66 milliseconds and 125 milliseconds reconstructions (both P 's > 0.05), respectively. Stent blooming artifacts were significantly lower on 66 milliseconds than on 125 milliseconds reconstructions (46.7% ± 10% vs 52.9% ± 8.9%, P < 0.001). Higher sharpness was found in 66 milliseconds than in 125 milliseconds reconstructions both in native coronary arteries (left anterior descending artery: 1031 ± 265 ∆HU/mm vs 819 ± 253 ∆HU/mm, P < 0.01; right coronary artery: 884 ± 352 ∆HU/mm vs 654 ± 377 ∆HU/mm, P < 0.001) and stents (5318 ± 3874 ∆HU/mm vs 4267 ± 3521 ∆HU/mm, P < 0.001). Coronary angiography with PCD-CT in the UHR mode profits considerably from a high temporal resolution, resulting in less motion artifacts, superior vessel delineation and in-stent lumen visualization, less stent blooming artifacts, and superior vessel and stent sharpness.

Coronary CTA for Acute Chest Pain in the Emergency Department: Comparison of 64-Detector-Row Single-Source and Third-Generation Dual-Source Scanners.

BACKGROUND. When coronary CTA is performed in the emergency department (ED), the use of a contemporary scanner with improved temporal resolution may eliminate the need to administer β-blockers for heart rate (HR) control, thereby expediting workup. OBJECTIVE. The purpose of this study was to compare ED length of stay (LOS), image quality, frequency of nondiagnostic examinations, and other clinical outcomes between patients undergoing coronary CTA in the ED on a single-source CT (SSCT) scanner with HR control versus on a dual-source CT (DSCT) scanner without HR control. METHODS. This retrospective study included 509 patients (283 men, 226 women; mean age, 52.1 ± 15.1 [SD] years) at low to intermediate risk for acute coronary syndrome who underwent coronary CTA for acute chest pain during off-hours in a single ED from March 1, 2020, to April 25, 2022. A total of 205 patients initially underwent CTA using a 64-detector-row SSCT scanner with HR control (oral β-blocker administration if HR was > 65 beats/min); after scanner replacement on April 26, 2021, 304 patients underwent CTA using a third-generation DSCT without HR control. Groups were compared in terms of ED LOS and CT completion time (defined as time from ordering CTA to completion of acquisition) using propensity score matching and additional endpoints including image quality and nondiagnostic examinations based on radiology reports. RESULTS. The DSCT group, compared with the SSCT group, showed no significant difference in median ED LOS (505 vs 457 minutes, respectively; p = .37) but showed shorter median CT completion time (95 vs 117 minutes, p < .001); on the basis of a mediation analysis, 89% of the reduction in CT completion time for DSCT was attributed to the absence of HR control. The DSCT group, compared with the SSCT group, showed higher frequency of examinations with good or excellent image quality (87.8% vs 60.0%, p < .001) and lower frequency of nondiagnostic examinations (1.6% vs 6.3%, p = .01) but showed no significant difference in frequencies of emergent cardiology consultation, invasive angiography, ED disposition, or coronary revascularization (all p > .05). No patient in either group experienced 30-day all-cause mortality or a major adverse cardiovascular event. CONCLUSION. The use of a DSCT scanner for coronary CTA can eliminate the need for β-blocker administration for HR control while decreasing nondiagnostic examinations. CLINICAL IMPACT. A DSCT scanner can expedite clinical processes in the ED.

Obesity-Related Pitfalls of Virtual versus True Non-Contrast Imaging-An Intraindividual Comparison in 253 Oncologic Patients.

Dual-source dual-energy CT (DECT) facilitates reconstruction of virtual non-contrast images from contrast-enhanced scans within a limited field of view. This study evaluates the replacement of true non-contrast acquisition with virtual non-contrast reconstructions and investigates the limitations of dual-source DECT in obese patients. A total of 253 oncologic patients (153 women; age 64.5 ± 16.2 years; BMI 26.6 ± 5.1 kg/m2) received both multi-phase single-energy CT (SECT) and DECT in sequential staging examinations with a third-generation dual-source scanner. Patients were allocated to one of three BMI clusters: non-obese: <25 kg/m2 (n = 110), pre-obese: 25-29.9 kg/m2 (n = 73), and obese: >30 kg/m2 (n = 70). Radiation dose and image quality were compared for each scan. DECT examinations were evaluated regarding liver coverage within the dual-energy field of view. While arterial contrast phases in DECT were associated with a higher CTDIvol than in SECT (11.1 vs. 8.1 mGy; p < 0.001), replacement of true with virtual non-contrast imaging resulted in a considerably lower overall dose-length product (312.6 vs. 475.3 mGy·cm; p < 0.001). The proportion of DLP variance predictable from patient BMI was substantial in DECT (R2 = 0.738) and SECT (R2 = 0.620); however, DLP of SECT showed a stronger increase in obese patients (p < 0.001). Incomplete coverage of the liver within the dual-energy field of view was most common in the obese subgroup (17.1%) compared with non-obese (0%) and pre-obese patients (4.1%). DECT facilitates a 30.8% dose reduction over SECT in abdominal oncologic staging examinations. Employing dual-source scanner architecture, the risk for incomplete liver coverage increases in obese patients.

Real-time germanium-doped optical fibers for clinical computed tomography dosimetry

In studies focusing on the practice of clinical computed tomography (CT) a particular concern has been that of delivering unnecessary dose to patients and with it the added risk for radiation-induced cancers. For a CT system, present work has investigated the dosimetric characteristics of a Ge-doped optical fiber real-time dosimetry system (model LS-2000, Lumisyns), measuring beam quality, exposure linearity and exposure duration accuracy. For comparison, the study has used a RaySafe X2 test device (Unfors RaySafe) and a Black Piranha (RTI) QA meter. Irradiations were made using a Somatom Definition Flash dual-source 128-slice CT scanner (Siemens Healthcare). The LS-2000, RaySafe X2, and Black Piranha sensors were exposed to beams energized at accelerating potentials ranging from 80 to 140 kVp, with tube current-time products from 50 to 300 mA, and exposure durations from 750 to 2000 ms. Constant signal responses from the LS-2000 have been obtained, measured in respect of beam quality, exposure linearity, and time accuracy. In respect of accuracy of beam quality, the RaySafe X2 and Black Piranha maximum deviations were 1% and 5%, respectively; the coefficients of linearity of RaySafe, Black Piranha and LS-2000 are 1%, 0.4% and 1.4%, respectively; the maximum deviation for the time accuracy test for the three sensors are 0.5%, 2% and 1.3%, respectively. Evaluation of the LS-2000 real-time dosimetry system with a Ge-doped optical fiber scintillator points to potential for its use in clinical CT dosimetry.