Variability and Reproducibility of the SYNTAX Score for Triple-Vessel Disease.

BACKGROUND: The SYNTAX score (SX) is an angiographic grading system to determine the burden and complexity of coronary artery disease (CAD) and to guide operators as to the appropriateness of percutaneous coronary intervention (PCI) vs coronary artery bypass grafting (CABG). However, variability of the SX may exist since the assessment relies on individual clinicians to visually interpret lesion severity and characteristics. We therefore aimed to assess SX variability and reproducibility among interpreting physicians. METHODS: Fifty patient angiograms were randomly selected from a registry of patients with multi-vessel CAD (treated with PCI or CABG) completed at our institution during the years 2011-2018. Each angiogram was evaluated by 6 clinicians on 2 separate occasions (minimum 8 weeks between occasions) for a total of 600 SX. Our goal was to evaluate both inter- and intra- observer reliability of SX scores. Variation in both raw score as well as risk classification (low, intermediate or high SX) was observed. Inter- and intra-observer reliability were assessed using the intra-class correlation coefficient (ICC), Cohen's weighted Kappa, and Fleiss' Kappa. RESULTS: SYNTAX scores on both assessments and across all 6 cardiologists had a mean score of 25.3. On the first assessment, the ICC for the inter-observer reliability of SX scores was 0.61 (95% CI: 0.50, 0.73). Across the 6 observers, only 16% of angiograms were classified in the same risk classification by all observers. 34% of angiograms had less than a majority agreement (3 or less observers) on risk classification. The weighted Kappa for intra-observer reliability of risk classification scores ranged from 0.30 to 0.81. Across the 6 observers, the proportion of angiograms classified as the same risk classification between each observer's 1st and 2nd assessment ranged from 46% to 84%. CONCLUSION: This study shows a wide inter- and intra- user variability in calculating SX. Our data indicates a significant limitation in using the SX to guide revascularization strategies. Further studies are needed to determine more reliable ways to quantitate burden of CAD.

Early recurrence of atrial fibrillation after pulmonary vein isolation: a comparative analysis between cryogenic and contact force radiofrequency ablation.

BACKGROUND: Early recurrence (ER) of atrial fibrillation (AF) within 90 days post-ablation is observed in up to 50% of patients and has been attributed to transient inflammation. The importance of ER in current era of pulmonary vein isolation (PVI) with cryoballoon ablation (CBA) and contact-force catheter radiofrequency ablation (cfRFA) has not been clearly reported. In addition, it is not known whether there are differences between types of ablation energy used during PVI. METHODS: Study population was drawn from a prospective multicenter database of AF ablation. Consecutive patients undergoing first-time ablation with PVI alone, using either second-generation CBA or cfRFA catheters were included. Patients were followed at 0.5, 3, 6, and 12 months to assess recurrence. Predictors of late recurrence (LR), defined as recurrence outside the blanking period, were assessed by Cox proportional hazards regression models. Freedom from LR was calculated and compared between two groups using the Kaplan-Meier method and log-rank test. RESULTS: Study cohort included 300 patients (1:1 CBA:RFA, age 63.6 ± 10.3 years, 67% male). There were no baseline characteristic differences between the CBA and cfRFA groups. ER occurred in 23.3% and 16.7% of patients in the CBA and cfRFA groups, respectively (p = 0.149). One-year freedom from LR was similar for both groups (72.7% CBA vs. 78% cfRFA, p = 0.287). Fifty-two patients (25 CBA and 27 cfRFA) underwent repeat ablation and no difference in durability of PVI was found. ER was the only common independent predictor of LR for either group and for the entire cohort (HR 2.3). CONCLUSIONS: In our series of AF ablation using second-generation cryoballoon and contact-force RFA catheters, recurrence in the "blanking period" is seen in 20% and remains predictive of late recurrence irrespective of the energy used.

View-Sharing Artifact Reduction With Retrospective Compressed Sensing Reconstruction in the Context of Contrast-Enhanced Liver MRI for Hepatocellular Carcinoma (HCC) Screening.

BACKGROUND: View-sharing (VS) increases spatiotemporal resolution in dynamic contrast-enhanced (DCE) MRI by sharing high-frequency k-space data across temporal phases. This temporal sharing results in respiratory motion within any phase to propagate artifacts across all shared phases. Compressed sensing (CS) eliminates the need for VS by recovering missing k-space data from pseudorandom undersampling, reducing temporal blurring while maintaining spatial resolution. PURPOSE: To evaluate a CS reconstruction algorithm on undersampled DCE-MRI data for image quality and hepatocellular carcinoma (HCC) detection. STUDY TYPE: Retrospective. SUBJECTS: Fifty consecutive patients undergoing MRI for HCC screening (29 males, 21 females, 52-72 years). FIELD STRENGTH/SEQUENCE: 3.0T MRI. Multiphase 3D-SPGR T1 -weighted sequence undersampled in arterial phases with a complementary Poisson disc sampling pattern reconstructed with VS and CS algorithms. ASSESSMENT: VS and CS reconstructions evaluated by blinded assessments of image quality and anatomic delineation on Likert scales (1-4 and 1-5, respectively), and HCC detection by OPTN/UNOS criteria including a diagnostic confidence score (1-5). Blinded side-by-side reconstruction comparisons for lesion depiction and overall series preference (-3-3). STATISTICAL ANALYSIS: Two-tailed Wilcoxon signed rank tests for paired nonparametric analyses with Bonferroni-Holm multiple-comparison corrections. McNemar's test for differences in lesion detection frequency and transplantation eligibility. RESULTS: CS compared with VS demonstrated significantly improved contrast (mean 3.6 vs. 2.9, P < 0.0001) and less motion artifact (mean 3.6 vs. 3.2, P = 0.006). CS compared with VS demonstrated significantly improved delineations of liver margin (mean 4.5 vs. 3.8, P = 0.0002), portal veins (mean 4.5 vs. 3.7, P < 0.0001), and hepatic veins (mean 4.6 vs. 3.5, P < 0.0001), but significantly decreased delineation of hepatic arteries (mean 3.2 vs. 3.7, P = 0.004). No significant differences were seen in the other assessments. DATA CONCLUSION: Applying a CS reconstruction to data acquired for a VS reconstruction significantly reduces motion artifacts in a clinical DCE protocol for HCC screening. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:984-993.

Accelerated imaging of metallic implants using model-based nonlinear reconstruction.

PURPOSE: To accelerate imaging near metallic implants with multi-spectral imaging (MSI) techniques by exploiting a signal model in the spectral dimension. METHODS: MSI techniques resolve metal-induced field perturbations by acquiring separate 3D spatial encodings at multiple excitation frequencies, which are referred to as spectral bins. The proposed model-based reconstruction exploits the correlation between spectral bins in image reconstruction by enforcing a signal model to describe the signal profile across bins. This work evaluates the accuracy of the MSI signal model in simulations and in vivo experiments. The proposed model-based reconstruction was evaluated in 6 subjects at an overall undersampling factor of 17.4 and compared with model-free parallel imaging and compressed sensing (PI & CS). The quality of reconstructed images was evaluated using normalized RMS error (nRMSE) and structural similarity index (SSIM) comparisons, with paired Wilcoxon tests in 6 subjects used to determine whether there was a significant difference in the metrics. RESULTS: Both simulations and in vivo experiments show that the proposed signal model can represent the MSI signal profiles in the spectral dimension compactly and accurately. In the in vivo experiments, the model-based reconstruction significantly improved image quality over model-free PI & CS, with P < 0.05 for both nRMSE and SSIM at 17.4× acceleration. CONCLUSION: This work presents the feasibility of using a model-based reconstruction to accelerate MSI techniques for faster MR imaging near metal.

Motion-robust reconstruction of multishot diffusion-weighted images without phase estimation through locally low-rank regularization.

PURPOSE: The goal of this work is to propose a motion robust reconstruction method for diffusion-weighted MRI that resolves shot-to-shot phase mismatches without using phase estimation. METHODS: Assuming that shot-to-shot phase variations are slowly varying, spatial-shot matrices can be formed using a local group of pixels to form columns, in which each column is from a different shot (excitation). A convex model with a locally low-rank constraint on the spatial-shot matrices is proposed. In vivo brain and breast experiments were performed to evaluate the performance of the proposed method. RESULTS: The proposed method shows significant benefits when the motion is severe, such as for breast imaging. Furthermore, the resulting images can be used for reliable phase estimation in the context of phase-estimation-based methods to achieve even higher image quality. CONCLUSION: We introduced the shot-locally low-rank method, a reconstruction technique for multishot diffusion-weighted MRI without explicit phase estimation. In addition, its motion robustness can be beneficial to neuroimaging and body imaging.

On-the-Fly Adaptive ${k}$ -Space Sampling for Linear MRI Reconstruction Using Moment-Based Spectral Analysis.

In high-dimensional magnetic resonance imaging applications, time-consuming, sequential acquisition of data samples in the spatial frequency domain ( -space) can often be accelerated by accounting for dependencies in linear reconstruction, at the cost of noise amplification that depends on the sampling pattern. Common examples are support-constrained, parallel, and dynamic MRI, and -space sampling strategies are primarily driven by image-domain metrics that are expensive to compute for arbitrary sampling patterns. It remains challenging to provide systematic and computationally efficient automatic designs of arbitrary multidimensional Cartesian sampling patterns that mitigate noise amplification, given the subspace to which the object is confined. To address this problem, this paper introduces a theoretical framework that describes local geometric properties of the sampling pattern and relates them to the spread in the eigenvalues of the information matrix described by its first two spectral moments. This new criterion is then used for very efficient optimization of complex multidimensional sampling patterns that does not require reconstructing images or explicitly mapping noise amplification. Experiments with in vivo data show strong agreement between this criterion and traditional, comprehensive image-domain- and -space-based metrics, indicating the potential of the approach for computationally efficient (on-the-fly), automatic, and adaptive design of sampling patterns.

Accelerated three-dimensional multispectral MRI with robust principal component analysis for separation of on- and off-resonance signals.

PURPOSE: To enable highly accelerated distortion-free MRI near metal by separating on- and off-resonance to exploit the redundancy of slice-phase encoding for the dominant on-resonance component. METHODS: Multispectral MRI techniques resolve off-resonance distortions by a combination of limited excitation bins and additional encoding. Inspired by robust principal component analysis, a novel compact representation of multispectral images as a sum of rank-one and sparse matrices corresponding to on- and off-resonance respectively is described. This representation is used in a calibration-free and model-free reconstruction for data with an undersampling pattern that varies between bins. Retrospective undersampling was used to compare the proposed reconstruction and bin-by-bin compressed sensing. Hip images were acquired in eight patients with standard and prospectively undersampled three-dimensional multispectral imaging, and image quality was evaluated by two radiologists on a 5-point scale. RESULTS: Experiments with retrospective undersampling showed that the enhanced sparsity afforded by the separation greatly reduces reconstruction errors and artifacts. Images from prospectively undersampled multispectral imaging offered 2.6-3.4-fold (18-24-fold overall) acceleration compared to standard multispectral imaging with parallel imaging and partial-Fourier acceleration with equivalence in all qualitative assessments within a tolerance of one point (P < 0.004). CONCLUSION: Three-dimensional multispectral imaging can be highly accelerated by varying undersampling between bins and separating on- and off-resonance. Magn Reson Med 79:1495-1505, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Simultaneous bilateral-knee MR imaging.

PURPOSE: To demonstrate and evaluate the scan time and quantitative accuracy of simultaneous bilateral-knee imaging compared with single-knee acquisitions. METHODS: Hardware modifications and safety testing was performed to enable MR imaging with two 16-channel flexible coil arrays. Noise covariance and sensitivity-encoding g-factor maps for the dual-coil-array configuration were computed to evaluate coil cross-talk and noise amplification. Ten healthy volunteers were imaged on a 3T MRI scanner with both dual-coil-array bilateral-knee and single-coil-array single-knee configurations. Two experienced musculoskeletal radiologists compared the relative image quality between blinded image pairs acquired with each configuration. Differences in T2 relaxation time measurements between dual-coil-array and single-coil-array acquisitions were compared with the standard repeatability of single-coil-array measurements using a Bland-Altman analysis. RESULTS: The mean g-factors for the dual-coil-array configuration were low for accelerations up to 6 in the right-left direction, and minimal cross-talk was observed between the two coil arrays. Image quality ratings of various joint tissues showed no difference in 89% (95% confidence interval: 85-93%) of rated image pairs, with only small differences ("slightly better" or "slightly worse") in image quality observed. The T2 relaxation time measurements between the dual-coil-array configuration and the single-coil configuration showed similar limits of agreement and concordance correlation coefficients (limits of agreement: -0.93 to 1.99 ms; CCC: 0.97 (95% confidence interval: 0.96-0.98)), to the repeatability of single-coil-array measurements (limits of agreement: -2.07 to 1.96 ms; CCC: 0.97 (95% confidence interval: 0.95-0.98)). CONCLUSION: A bilateral coil-array setup can image both knees simultaneously in similar scan times as conventional unilateral knee scans, with comparable image quality and quantitative accuracy. This has the potential to improve the value of MRI knee evaluations. Magn Reson Med 80:529-537, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

3D Cartesian MRI with compressed sensing and variable view sharing using complementary poisson-disc sampling.

PURPOSE: To enable robust, high spatio-temporal-resolution three-dimensional Cartesian MRI using a scheme incorporating a novel variable density random k-space sampling trajectory allowing flexible and retrospective selection of the temporal footprint with compressed sensing (CS). METHODS: A complementary Poisson-disc k-space sampling trajectory was designed to allow view sharing and varying combinations of reduced view sharing with CS from the same prospective acquisition. These schemes were used for two-point Dixon-based dynamic contrast-enhanced MRI (DCE-MRI) of the breast and abdomen. Results were validated in vivo with a novel approach using variable-flip-angle data, which was retrospectively accelerated using the same methods but offered a ground truth. RESULTS: In breast DCE-MRI, the temporal footprint could be reduced 2.3-fold retrospectively without introducing noticeable artifacts, improving depiction of rapidly enhancing lesions. Further, experiments with variable-flip-angle data showed that reducing view sharing improved accuracy in reconstruction and T1 mapping. In abdominal MRI, 2.3-fold and 3.6-fold reductions in temporal footprint allowed reduced motion artifacts. CONCLUSION: The complementary-Poisson-disc k-space sampling trajectory allowed a retrospective spatiotemporal resolution tradeoff using CS and view sharing, imparting robustness to motion and contrast enhancement. The technique was also validated using a novel approach of fully acquired variable-flip-angle acquisition. Magn Reson Med 77:1774-1785, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Location-dependent ethnic differences in the risk of colorectal adenoma: a retrospective multiethnic study.

BACKGROUND AND AIMS: Epidemiological data have demonstrated that Hispanics have a lower incidence rate of colorectal cancer (CRC) compared with other major race/ethnicity groups in the United States. However, data regarding the relative prevalence of colorectal adenomas (CRAs) in Hispanic versus non-Hispanic populations are currently sparse and inconclusive. METHODS: We conducted a retrospective review of colonoscopy patients (n=1656) at a single tertiary-care community hospital from 2007 to 2011, to evaluate the association of self-reported race/ethnicity status with CRA prevalence and characteristics. Established CRC risk factors were also included in multivariate regression models. RESULTS: Overall, the CRA prevalence was lower in Hispanic subjects than non-Hispanic subjects (14.8% vs. 22.5%) and this difference was statistically significant (adjusted odds ratio, 0.67; 95% confidence interval, 0.47-0.96; P<0.01). Conversely, no difference in CRA prevalence was observed between non-Hispanic white and black subjects. Further analyses by adenoma location revealed more pronounced reduction in proximal CRA prevalence for Hispanics versus non-Hispanics (5.3% vs. 13.1%; adjusted odds ratio, 0.42; 95% confidence interval, 0.26-0.70; P<0.001), whereas CRA prevalence in distal colon, rectum or multiple locations did not differ significantly between race/ethnicity groups. CONCLUSIONS: Our data showed a marked distinction in CRA prevalence, particularly proximal adenomas, between Hispanics and non-Hispanics. Additional multicenter studies are needed to confirm these findings, elucidate the underlying mechanisms, and clarify the implications for CRC screening and other preventive and/or therapeutic interventions.

Water flows, energy demand, and market analysis of the informal water sector in Kisumu, Kenya.

In rapidly growing urban areas of developing countries, infrastructure has not been able to cope with population growth. Informal water businesses fulfill unmet water supply needs, yet little is understood about this sector. This paper presents data gathered from quantitative interviews with informal water business operators (n=260) in Kisumu, Kenya, collected during the dry season. Sales volume, location, resource use, and cost were analyzed by using material flow accounting and spatial analysis tools. Estimates show that over 76% of the city's water is consumed by less than 10% of the population who have water piped into their dwellings. The remainder of the population relies on a combination of water sources, including water purchased directly from kiosks (1.5 million m3 per day) and delivered by hand-drawn water-carts (0.75 million m3 per day). Energy audits were performed to compare energy use among various water sources in the city. Water delivery by truck is the highest per cubic meter energy demand (35 MJ/m3), while the city's tap water has the highest energy use overall (21,000 MJ/day). We group kiosks by neighborhood and compare sales volume and cost with neighborhood-level population data. Contrary to popular belief, we do not find evidence of price gouging; the lowest prices are charged in the highest-demand low-income area. We also see that the informal sector is sensitive to demand, as the number of private boreholes that serve as community water collection points are much larger where demand is greatest.

Obesity, metabolic factors, and colorectal adenomas: a retrospective study in a racially diverse New York State Hospital.

OBJECTIVE: We studied a racially diverse population and the relationship with colorectal adenomas (CA) further looking for risks related to BMI and metabolic factors. DESIGNS: Seven hundred seventy-nine patients who underwent screening colonoscopies between 2007 and 2009 meeting exclusion criteria were included. To evaluate the association between race, BMI, and other metabolic factors with having one or more CA detected at colonoscopy, adjusted odds ratios and 95 % CI were estimated using unconditional logistic regression models. OUTCOMES: CA were detected in 167 out of 779 (21.4 %) patients. Compared to Whites, Hispanics were less likely to have one or more adenomas detected during a screening colonoscopy (OR = 0.52, 95 % CI, 0.31-0.88; p = 0.01). There was no significant statistical difference between Blacks and Whites, or other races and Whites. There was an association between the presence of CA and smoking (OR = 1.57, 95 % CI, 1.02-2.43; p = 0.04). CONCLUSION: Our results showed that Hispanics were less likely to have an adenoma detected during a screening colonoscopy than Whites. No statistical significant difference was found between patients with metabolic factors and the presence of colorectal adenoma.

The relationship of vitamin D status, smoking, and colorectal adenoma: a retrospective study in an ethnically diverse community.

OBJECTIVE: Circulating 25-hydroxyvitamin D (25OHD) level is suggested to be negatively correlated with risk of colorectal cancer (CRC) and colorectal adenoma (CRA), but most of the epidemiological data were originated amongst Caucasians and African Americans. This study aimed to investigate the relationship between vitamin D status, smoking and CRA in an ethnically diverse community with a high Hispanic density. METHODS: In this retrospective study, we included 233 patients who underwent complete colonoscopies from 2009 to 2011, and their serum 25OHD levels in the winter season had been measured. Among them, 65 adenoma cases and 168 adenoma-free controls were identified and evaluated for the association of CRA with smoking, ethnicity and serum 25OHD level using unstratified and stratified multivariate logistic regression analyses. RESULTS: In our study participants, the mean serum 25OHD level and the percentage of Hispanics were lower in the adenoma group versus the control group, while no black-white difference was noted in the CRA prevalence. When adjusted for 25OHD level, the lower rate of adenoma in Hispanics compared to non-Hispanics was attenuated and became statistically insignificant. A mild protective effect of vitamin D (6% reduction) on the CRA risk was found significant for active smokers, but not for non-smokers. A detrimental impact of smoking in the CRA risk was only shown among non-Hispanic patients, but not among Hispanics irrespective of vitamin D status. CONCLUSIONS: Our data suggest a marked distinction between Hispanics and non-Hispanics in the risk of CRA. The reduced adenoma prevalence among Hispanics vs. non-Hispanics could be partially explained by vitamin D status, cigarette smoking and their interactions. Future larger-sized multi-center studies on vitamin D status and ethnicity, as well as dietary, behavioral, genetic factors and their interactions for CRA and CRC are needed. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Luminal flow amplifies stent-based drug deposition in arterial bifurcations.

BACKGROUND: Treatment of arterial bifurcation lesions using drug-eluting stents (DES) is now common clinical practice and yet the mechanisms governing drug distribution in these complex morphologies are incompletely understood. It is still not evident how to efficiently determine the efficacy of local drug delivery and quantify zones of excessive drug that are harbingers of vascular toxicity and thrombosis, and areas of depletion that are associated with tissue overgrowth and luminal re-narrowing. METHODS AND RESULTS: We constructed two-phase computational models of stent-deployed arterial bifurcations simulating blood flow and drug transport to investigate the factors modulating drug distribution when the main-branch (MB) was treated using a DES. Simulations predicted extensive flow-mediated drug delivery in bifurcated vascular beds where the drug distribution patterns are heterogeneous and sensitive to relative stent position and luminal flow. A single DES in the MB coupled with large retrograde luminal flow on the lateral wall of the side-branch (SB) can provide drug deposition on the SB lumen-wall interface, except when the MB stent is downstream of the SB flow divider. In an even more dramatic fashion, the presence of the SB affects drug distribution in the stented MB. Here fluid mechanic effects play an even greater role than in the SB especially when the DES is across and downstream to the flow divider and in a manner dependent upon the Reynolds number. CONCLUSIONS: The flow effects on drug deposition and subsequent uptake from endovascular DES are amplified in bifurcation lesions. When only one branch is stented, a complex interplay occurs - drug deposition in the stented MB is altered by the flow divider imposed by the SB and in the SB by the presence of a DES in the MB. The use of DES in arterial bifurcations requires a complex calculus that balances vascular and stent geometry as well as luminal flow.