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Background Given the rising utilization of medical imaging and the risks of radiation, there is increased interest in reducing radiation exposure. The objective of this study was to evaluate, as a proof of principle, CT scans performed at radiation doses equivalent to that of a posteroanterior and lateral chest radiograph series in the cystic lung disease lymphangioleiomyomatosis (LAM). Methods From November 2016 to May 2018, 105 consecutive subjects with LAM received chest CT scans at standard and ultra-low radiation doses. Standard and ultra-low-dose images, respectively, were reconstructed with routine iterative and newer model-based iterative reconstruction. LAM severity can be quantified as cyst score (percentage of lung occupied by cysts), an ideal benchmark for validating CT scans performed at a reduced dose compared with a standard dose. Cyst scores were quantified using semi-automated software and evaluated by linear correlation and Bland-Altman analysis. Results Overall, ultra-low-dose CT scans represented a 96% dose reduction, with a median dose equivalent to 1 vs 22 posteroanterior and lateral chest radiograph series (0.14 mSv; 5th-95th percentile, 0.10-0.20 vs standard dose 3.4 mSv; 5th-95th percentile, 1.5-7.4; P Conclusions In LAM chest CT scan at substantial radiation reduction to doses equivalent to that of a posteroanterior and lateral chest radiograph series provides cyst score quantification similar to that of standard-dose CT scan. Trial Registry ClinicalTrials.gov; Nos.: NCT00001465 and NCT00001532 ; URL: www.clinicaltrials.gov .

Item does not contain fulltext OBJECTIVE: The objective of this study was to evaluate a prototype, ultrahigh-resolution computed tomography offering higher reconstruction matrix (1024 x 1024) and spatial resolution (0.15 mm) for chest imaging. METHODS: Higher (1024) matrix reconstruction enabled by ultrahigh-resolution computed tomography scanner (128-detector rows; detector width, 0.25 mm; spatial resolution, 0.15 mm) was compared with conventional (512) reconstruction with image quality grading on a Likert scale (1, excellent; 5, nondiagnostic) for image noise, artifacts, contrast, small detail, lesion conspicuity, image sharpness, and diagnostic confidence. Image noise and signal-to-noise ratio were quantified. RESULTS: Diagnostic image quality was achieved for all scans on 101 patients. The 1024 reconstruction demonstrated increased image noise (20.2 +/- 4.0 vs 17.2 +/- 3.8, P < 0.001) and a worse noise rating (1.98 +/- 0.63 vs 1.75 +/- 0.61, P < 0.001) but performed significantly better than conventional 512 matrix with fewer artifacts (1.37 +/- 0.43 vs 1.50 +/- 0.48, P < 0.001), better contrast (1.50 +/- 0.56 vs 1.62 +/- 0.57, P < 0.001), small detail detection (1.06 +/- 0.19 vs 2.02 +/- 0.22, P < 0.001), lesion conspicuity (1.08 +/- 0.23 vs 2.02 +/- 0.24, P < 0.001), sharpness (1.09 +/- 0.24 vs 2.02 +/- 0.28, P < 0.001), and overall diagnostic confidence (1.09 +/- 0.25 vs 1.18 +/- 0.34, P < 0.001). CONCLUSIONS: Ultrahigh-resolution computed tomography enabled a higher reconstruction matrix and improved image quality compared with conventional matrix reconstruction, with a minor increase in noise.

Background CT allows evaluation of atherosclerosis, coronary stenosis, and myocardial ischemia. Data on the characterization of ischemia and no obstructive stenosis (INOCA) at CT remain limited. Purpose This was an observational study to describe the prevalence of INOCA defined at coronary CT angiography with CT perfusion imaging and associated clinical and atherosclerotic characteristics. The analysis was also performed for the combination of invasive coronary angiography (ICA) and SPECT as a secondary aim. Materials and Methods The prospective CORE320 study (ClinicalTrials.gov: NCT00934037) enrolled participants between November 2009 and July 2011 who were symptomatic and referred for clinically indicated ICA. Participants underwent CT angiography, rest-adenosine stress CT perfusion, and rest-stress SPECT prior to ICA. For this ancillary study, the following three phenotypes were considered, using either CT angiography/CT perfusion or ICA/SPECT data: (a) participants with obstructive (≥50%) stenosis, (b) participants with no obstructive stenosis but ischemia (ie, INOCA) on the basis of abnormal perfusion imaging results, and (c) participants with no obstructive stenosis and normal perfusion imaging results. Clinical characteristics and CT angiography atherosclerotic plaque measures were compared by using the Pearson χ2 or Wilcoxon rank-sum test. Results A total of 381 participants (mean age, 62 years [interquartile range, 56-68 years]; 129 [34%] women) were evaluated. A total of 31 (27%) of 115 participants without obstructive (≥50%) stenosis at CT angiography had abnormal CT perfusion findings. The corresponding value for ICA/SPECT was 45 (30%) of 151. The prevalence of INOCA was 31 (8%) of 381 (95% confidence interval [CI]: 5%, 11%) with CT angiography/CT perfusion and 45 (12%) of 381 (95% CI: 9%, 15%) with ICA/SPECT. Participants with CT-defined INOCA had greater total atheroma volume (118 vs 60 mm3, P = .008), more positive remodeling (13% vs 1%, P = .006), and greater low-attenuation atheroma volume (20 vs 10 mm3, P = .007) than participants with no obstructive stenosis and no ischemia. Comparisons for ICA/SPECT showed similar trends. Conclusion In CORE320, ischemia and no obstructive stenosis (INOCA) prevalence was 8% and 12% at CT angiography/CT perfusion and invasive coronary angiography/SPECT, respectively. Participants with INOCA had greater atherosclerotic burden and more adverse plaque features at CT compared with those with no obstructive stenosis and no ischemia. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Francois in this issue.

To investigate the performance of a reconstruction algorithm, single-energy metal artifact reduction (SEMAR), against standard reconstruction in cardiac computed tomography (CT) studies of patients with implanted metal and in a defibrillator lead phantom.From a retrospective, cross-sectional clinical study with institutional review board approval of 118 patients with implanted metal, 122 cardiac CT studies from November 2009 to August 2016 performed on a 320-detector row scanner with standard and SEMAR reconstructions were included. The maximum beam hardening artifact radius, artifact attenuation variation surrounding the implanted metal, and image quality on a 4-point scale (1-no/minimal artifact to 4-severe artifact) were assessed for each reconstruction. A defibrillator lead phantom study was performed at different tube potentials and currents with both reconstruction methods. Maximum beam hardening artifact radius and average artifact attenuation variation were measured.In the clinical study, SEMAR markedly reduced the maximum beam hardening artifact radius by 77% (standard: 14.8 mm [IQR 9.7-22.2] vs. SEMAR: 3.4 mm [IQR 2.2-7.1], p 0.0001) and artifact attenuation variation by 51% (standard: 130.0 HU [IQR 75.9-184.4] vs. SEMAR: 64.3 HU [IQR 48.2-89.2], p 0.0001). Image quality improved with SEMAR (standard: 3 [IQR 2-3.5] vs. SEMAR: 2 [IQR 1-2.5], p 0.0001). The defibrillator lead phantom study confirmed these results across varying tube potentials and currents.SEMAR reconstruction achieved superior image quality and markedly reduced maximum beam hardening artifact radius and artifact attenuation variation compared to standard reconstruction in 122 clinical cardiac CT studies of patients with implanted metal and in a defibrillator lead phantom study.

OBJECTIVES The aim of this study is to evaluate the effect of heart rate on exposure window, best phase, and image quality for stress computed tomography perfusion (CTP) in the CORE320 study. METHODS The CTP data sets were analyzed to determine the best phase for perfusion analysis. A predefined exposure window covering 75% to 95% of the R-R cycle was used. RESULTS Of the 368 patients included in the analysis, 93% received oral β blockade before the rest scan. The median heart rate during the stress acquisition was 69 bpm (interquartile range [IQR], 60-77). The median best phase was 81% (IQR, 76-90), and length of exposure window was 22% (IQR, 19-24). The best phase was significantly later in the cardiac cycle with higher heart rates (P < 0.001), and higher heart rates resulted in a small, but higher number of poor quality scans (6%, P < 0.001). The median effective dose of the stress scan was 5.3 mSv (IQR, 3.8-6.1). CONCLUSIONS Stress myocardial CTP imaging can be performed using prospective electrocardiography triggering, an exposure window of 75% to 95%, and β-blockade resulting in good or excellent image quality in the majority (80%) of patients while maintaining a low effective radiation dose.

Assessing coronary artery calcium (CAC) is a valuable tool for individualizing cardiac risk assessment. In CAC scanning, this technical report assesses the use of a true model-based iterative reconstruction algorithm using forward projected model-based iterative reconstruction (“FIRST”) and assess whether FIRST allows for reduced radiation dose CAC scanning on 320-detector row computed tomography (320-CT). Here, 100 consecutive patients prospectively underwent reduced and standard dose scans. For the patients (59 ± 9 years, 61% male) stratified by Agatston categories 0, 1–10, 11–100, 101–400,> 400, agreement between reduced dose with FIRST versus standard dose with FBP was excellent at 81% (95% CI: 73–88%) with kappa 0.74 (95% CI: 0.64–0.85). Median radiation exposure was 75% lower for reduced (0.35 mSv) versus standard dose (1.37 mSv) scans. In conclusion, agreement was excellent for reduced dose with FIRST and standard dose with FBP in 320-detector row CT CAC imaging in well-established categories of cardiovascular risk. These methods make it possible to reduce radiation exposure by 75%.

Background The reader confidence and diagnostic accuracy of coronary CT angiography (CCTA) can be compromised by the presence of calcified plaques and stents causing blooming artifacts. Compared to conventional invasive coronary angiography (ICA), this may cause an overestimation of stenosis severity leading to false-positive results. In a pilot study, we tested the feasibility of a new coronary calcium image subtraction algorithm in relation to reader confidence and diagnostic accuracy. Methods Forty-three patients underwent clinically indicated ICA and CCTA using a 320-detector row CT. Median Agatston score was 510. Two data sets were reconstructed: a conventional CCTA (CCTA conv ) and a subtracted CCTA (CCTA sub ), where calcifications detected on noncontrast images were subtracted from the CCTA. Reader confidence and concordance with ICA for identification of >50% stenosis were recorded. We defined target segments on CCTA conv as motion-free coronary segments with calcification or stent and low reader confidence. The effect of CCTA sub was assessed. No approval from the ethics committee was required according to Danish law. Results A total of 76 target segments were identified. The use of coronary calcium image subtraction improved the reader confidence in 66% of these segments. In target segments, specificity (86% vs 65%; P P = .03) were improved using CCTA sub compared to CCTA conv without loss in negative predictive value. Conclusions Our initial experience with coronary calcium image subtraction suggests that it is feasible and could lead to an improvement in reader confidence and diagnostic accuracy for identification of significant coronary artery disease.

Background— Coronary computed tomographic angiography (CTA) and myocardial perfusion imaging (CTP) is a validated approach for detection and exclusion of flow-limiting coronary artery disease (CAD), but little data are available on gender-specific performance of these modalities. In this study, we aimed to evaluate the diagnostic accuracy of combined coronary CTA and CTP in detecting flow-limiting CAD in women compared with men. Methods and Results— Three hundred and eighty-one patients who underwent both CTA-CTP and single-photon emission computed tomography myocardial perfusion imaging preceding invasive coronary angiography as part of the CORE320 multicenter study (Coronary Artery Evaluation Using 320-row Multidetector Computed Tomography Angiography and Myocardial Perfusion) were included in this ancillary study. All 4 image modalities were analyzed in blinded, independent core laboratories. Prevalence of flow-limiting CAD defined by invasive coronary angiography equal to 50% or greater with an associated single-photon emission computed tomography myocardial perfusion imaging defect was 45% (114/252) and 23% (30/129) in males and females, respectively. Patient-based diagnostic accuracy defined by the area under the receiver operating curve for detecting flow-limiting CAD by CTA alone in females was 0.83 (0.75–0.89) and for CTA-CTP was 0.92 (0.86–0.97; P =0.003) compared with men where the area under the receiver operating curve for detecting flow-limiting CAD by CTA alone was 0.82 (0.77–0.87) and for CTA-CTP was 0.84 (0.80–0.89; P =0.29). Conclusions— The combination of CTA-CTP was performed similarly in men and women for identifying flow-limiting coronary stenosis; however, in women, CTP had incremental value over CTA alone, which was not the case in men. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00934037.

Iterative reconstruction has been shown to reduce image noise compared with traditional filtered back projection with quantum denoising software (FBP/QDS+) in CT imaging but few comparisons have been made in the same patients without the influence of interindividual factors. The objective of

The purpose of this study was to estimate dose reduction after implementation of asymmetrical cone beam processing using exposure differences measured in a water phantom and a small cohort of clinical coronary CTA patients. Two separate 320 × 0.5 mm detector row scans of a water phantom used identical cardiac acquisition parameters before and after software modifications from symmetric to asymmetric cone beam acquisition and processing. Exposure was measured at the phantom surface with Optically Stimulated Luminescence (OSL) dosimeters at 12 equally spaced angular locations. Mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at the center plus four peripheral locations in the water phantom. To assess image quality, mean HU and standard deviation (SD) for both approaches were compared using ROI measurements obtained at five points within the water phantom. Retrospective evaluation of 64 patients (37 symmetric; 27 asymmetric acquisition) included clinical data, scanning parameters, quantitative plus qualitative image assessment, and estimated radiation dose. In the water phantom, the asymmetric cone beam processing reduces exposure by approximately 20% with no change in image quality. The clinical coronary CTA patient groups had comparable demographics. The estimated dose reduction after implementation of the asymmetric approach was roughly 24% with no significant difference between the symmetric and asymmetric approach with respect to objective measures of image quality or subjective assessment using a four point scale. When compared to a symmetric approach, the decreased exposure, subsequent lower patient radiation dose, and similar image quality from asymmetric cone beam processing supports its routine clinical use.