Myocardial extracellular volume quantification by cardiac CT in pulmonary hypertension: Comparison with cardiac MRI

PURPOSE

Myocardial extracellular volume (ECV) measured by cardiac magnetic resonance imaging (MRI) has been suggested as a marker of disease severity in pulmonary hypertension (PH). However, consistency between ECVs quantified by computed tomography (CT) and MRI has not been sufficiently investigated in (PH). We investigated the utility of CT-ECV in PH, using MRI-ECV as a reference standard.

METHOD

We evaluated 20 patients with known or suspected PH who underwent dual-energy CT, cardiac MRI, and right heart catheterization. We used Pearson correlation analysis to investigate correlations between CT-ECV and MRI-ECV. We also assessed correlations between ECV and mean pulmonary artery pressure (mPAP).

RESULTS

CT-ECV showed a very strong correlation with MRI-ECV at the anterior (r = 0.83) and posterior right ventricular insertion points (RVIPs) (r = 0.84). CT-ECV and MRI-ECV were strongly correlated in the septum and left ventricular free wall (r = 0.79-0.73) but weakly correlated in the right ventricular free wall (r = 0.26). CT-ECV showed a strong correlation with mPAP in the anterior RVIP (r = 0.64) and a moderate correlation in the posterior RVIP and septum (r = 0.50-0.42). Compared with CT-ECV, MRI-ECV had a higher correlation with mPAP; however, the difference was not significant (anterior RVIP, r = 0.72 [MRI-ECV] vs. 0.64 [CT-ECV], p = 0.663; posterior RVIP, r = 0.67 vs. 0.50, p = 0.446).

CONCLUSION

Dual-energy CT can quantify myocardial ECV and yield results comparable to those obtained using cardiac MRI. CT-ECV in the anterior RVIP could be a noninvasive surrogate marker of disease severity in PH.

Implementation of 99mTc-GSA SPECT Image-guided Inverse Planning into Palliative Radiotherapy for Diffuse Liver Metastases: A Novel Approach

BACKGROUND/AIM

This is a report of the first clinical implementation of ^99mTc-labeled diethylene triamine pentaacetate-galactosyl human serum albumin (^99mTc-GSA) single-photon emission computed tomography (SPECT) image-guided inverse planning into palliative radiotherapy (RT) for diffuse liver metastases.

CASE REPORT

A 48-year-old man developed chemo-refractory diffuse liver metastases from thymic carcinoma characterized by abdominal pain and distension. Palliative RT was performed with a total dose of 20 Gy in five fractions using double arc volumetric modulated arc therapy to reduce the dose to functional liver defined by ^99mTc-GSA SPECT images. His symptoms were immediately relieved after RT and did not experience radiation-induced liver disease. Both Functional Assessment of Cancer Therapy (FACT)-G and FACT-Hep total scores improved after 2 weeks of RT initiation and did not become worse than baseline scores.

CONCLUSION

The ^99mTc-GSA SPECT image-guided palliative RT is an effective and safe treatment for patients with diffuse liver metastases.

Effects of tube voltage and iodine contrast medium on radiation dose of whole-body CT

BACKGROUND

The low-tube-voltage scan generally needs a higher tube current than the conventional 120 kVp to maintain the image noise. In addition, the low-tube-voltage scan increases the photoelectric effect, which increases the radiation absorption in organs.

PURPOSE

To compare the organ radiation dose caused by iodine contrast medium between low tube voltage with low contrast medium and that of conventional 120-kVp protocol with standard contrast medium.

MATERIAL AND METHODS

After the propensity-matching analysis, 66 patients were enrolled including 33 patients with 120 kVp and 600 mgI/kg and 33 patients with 80 kVp and 300 mgI/kg (50% iodine reduction). The pre- and post-contrast phases were assessed in all patients. The Monte Carlo simulation tool was used to simulate the radiation dose. The computed tomography (CT) numbers for 10 organs and the organ doses were measured. The organ doses were normalized by the volume CT dose index, and the 120-kVp protocol was compared with the 80-kVp protocol.

RESULTS

On contrast-enhanced CT, there were no significant differences in the mean CT numbers of the organs between 80-kVp and 120-kVp protocols except for the pancreas, kidneys, and small intestine. The normalized organ doses at 80 kVp were significantly lower than those of 120 kVp in all organs (e.g. liver, 1.6 vs. 1.9; pancreas, 1.5 vs. 1.8; spleen, 1.7 vs. 2.0) on contrast-enhanced CT.

CONCLUSION

The low tube voltage with low-contrast-medium protocol significantly reduces organ doses at the same volume CT dose index setting compared with conventional 120-kVp protocol with standard contrast medium on contrast-enhanced CT.

Cardiac computed tomography-derived myocardial tissue characterization after anthracycline treatment

AIMS

Understanding cardiac function after anthracycline administration is very important from the perspective of preventing the onset of heart failure. Although cardiac magnetic resonance and echocardiography are recognized as the 'gold standard' for detecting cardiotoxicity, they have many shortcomings. We aimed to investigate whether cardiac computed tomography (CCT) could replace these techniques, assessing serial changes in cardiac tissue characteristics as determined by CCT after anthracycline administration.

METHODS AND RESULTS

We prospectively investigated 15 consecutive breast cancer patients who were scheduled to receive anthracycline therapy. We performed echocardiography and CCT before and 3, 6, and 12 months after anthracycline treatment. The mean cumulative administered anthracycline dose was 269.9 ± 14.6 mg/m² (doxorubicin-converted dose). Of the 15 enrolled patients who received anthracycline treatment for breast cancer, none met the definition of cardiotoxicity. The CCT-derived extracellular volume fraction tended to continue to increase after anthracycline treatment and had relatively similar dynamics to the left ventricular ejection fraction and global longitudinal strain as determined by echocardiography.

CONCLUSIONS

Our findings indicated that CCT could provide adequate information about the characteristics of myocardial tissue after anthracycline administration. CCT may improve the understanding of cardiotoxicity by compensating for the weaknesses of echocardiography. This technique could be useful for understanding cardiac tissue characterization as a 'one-stop shop' evaluation, providing new insight into cardiooncology.

Hybrid deep-learning-based denoising method for compressed sensing in pituitary MRI: comparison with the conventional wavelet-based denoising method

OBJECTIVES

This study aimed to evaluate the efficacy of a combined wavelet and deep-learning reconstruction (DLR) method for under-sampled pituitary MRI.

METHODS

This retrospective study included 28 consecutive patients who underwent under-sampled pituitary T2-weighted images (T2WI). Images were reconstructed using either the conventional wavelet denoising method (wavelet method) or the wavelet and DLR methods combined (hybrid DLR method) at five denoising levels. The signal-to-noise ratio (SNR) of the CSF, hypothalamic, and pituitary images and the contrast between structures were compared between the two image types. Noise quality, contrast, sharpness, artifacts, and overall image quality were evaluated by two board-certified radiologists. The quantitative and the qualitative analyses were performed with robust two-way repeated analyses of variance.

RESULTS

Using the hybrid DLR method, the SNR of the CSF progressively increased as denoising levels increased. By contrast, with the wavelet method, the SNR of the CSF, hypothalamus, and pituitary did not increase at higher denoising levels. There was a significant main effect of denoising methods (p < 0.001) and denoising levels (p < 0.001), and an interaction between denoising methods and denoising levels (p < 0.001). For all five qualitative scores, there was a significant main effect of denoising methods (p < 0.001) and an interaction between denoising methods and denoising levels (p < 0.001).

CONCLUSIONS

The hybrid DLR method can provide higher image quality for T2WI of the pituitary with compressed sensing (CS) than the wavelet method alone, especially at higher denoising levels.

KEY POINTS

• The signal-to-noise ratios of cerebrospinal fluid progressively increased with the hybrid DLR method, with an increase in the denoising level for cerebrospinal fluid in pituitary T2WI with CS. • The signal-to-noise ratios of cerebrospinal fluid using the conventional wavelet method did not increase at higher denoising levels. • All qualitative scores of hybrid deep-learning reconstructions at all denoising levels were higher than those for the wavelet denoising method.

Population pharmacokinetic analysis and dosage recommendations for digoxin in Japanese patients with atrial fibrillation and heart failure using real-world data

BACKGROUND

Digoxin is an important treatment option for reducing the ventricular rate in patients with atrial fibrillation (AF) and heart failure (HF). Digoxin has a narrow therapeutic window and large interindividual variability. A low target blood concentration, especially ≤0.9 ng/mL, is recommended for patients with HF who are taking digoxin. This study aimed to develop a population pharmacokinetic model and to identify clinical factors that affect digoxin exposure and an optimal digoxin dosing regimen in Japanese patients with AF and HF.

METHODS

A population pharmacokinetic analysis was performed by using a nonlinear mixed effects model based on 3465 concentration points from 391 patients (>18 years) who were receiving oral digoxin. Using trough serum digoxin concentrations and clinical data, a population pharmacokinetic model was developed for determining covariates of clearance. A 1-compartment model was used to examine the interindividual variability of the oral clearance (CL/F) of digoxin. An appropriate dosage of digoxin was identified using Monte Carlo simulation.

RESULTS

The final model demonstrated that creatinine clearance (CL_CR) and the use of amiodarone were factors that contributed to the CL/F of digoxin. Monte Carlo simulation results showed that with a daily maintenance dose of 0.25 mg, the intoxication risk window of a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients regardless of renal function category or concurrent use of amiodarone. The appropriate maintenance dosage was 0.125 mg daily for most Japanese patients with AF and HF. However, with a daily dose of 0.125 mg, a trough serum concentration of ≥0.9 ng/mL could be reached in more than half of patients with renal impairments (CL_CR 30 mL/min) or concurrent use of amiodarone. A daily maintenance dose of 0.0625 mg was acceptable for these patients.

CONCLUSIONS

CL_CR and the use of amiodaron were found to contribute to digoxin clearance using a population pharmacokinetic methodology. For Japanese patients with AF and HF, 0.125 mg is an appropriate daily digoxin maintenance dose, but a dose reduction is required for patients with CL_CR <30 mL/min or concurrent amiodarone use.

Spectral imaging with dual-layer spectral detector computed tomography for the detection of perfusion defects in acute coronary syndrome

To evaluate the feasibility of spectral imaging with dual-layer spectral detector computed tomography (CT) for the diagnosis of acute coronary syndrome. We identified 30 consecutive patients who underwent cardiac CT using dual-layer spectral detector CT and were diagnosed with acute ischemic syndrome by an invasive coronary angiography. We reconstructed 120 kVp images and generated virtual monochromatic images (VMIs; 40-200 keV in 10 keV increments), iodine concentration maps, and effective atomic number (Z) maps. We calculated the contrast and contrast-to-noise ratio (CNR) between myocardial normal and hypo-perfusion and chose the VMIs with the best CNR for quantitative analysis. We compared the image noise, contrast, and CNR of 120 kVp images and the best VMIs, CT value, iodine concentration, and effective Z between myocardial normal and hypo-perfusion with the paired t test. As the X-ray energy decreased, venous attenuation, contrast, and CNR gradually increased. The 40 keV image yielded the best CNR. The contrast and CNR between myocardial normal and hypo-perfusion were significantly higher in 40 keV images than those in 120 kVp images. The iodine concentration and the effective Z were significantly higher in normal myocardium than those in hypo-perfused myocardium. Spectral imaging with dual-layer spectral detector CT is a feasible technique to detect the hypo-perfused area of acute ischemic syndrome.

External Evaluation of a Bayesian Warfarin Dose Optimization Based on a Kinetic-Pharmacodynamic Model

Warfarin is a representative anticoagulant with large interindividual variability. The published kinetic-pharmacodynamic (K-PD) model allows the prediction of warfarin dose requirement in Swedish patients; however, its applicability in Japanese patients is not known. We evaluated the model's predictive performance in Japanese patients with various backgrounds and relationships using Bayesian parameter estimation and sampling times. A single-center retrospective observational study was conducted at Tokyo Women's Medical University, Medical Center East. The study population consisted of adult patients aged >20 years who commenced warfarin with a prothrombin time-international normalized ratio (PT-INR) from June 2015 to June 2019. The published K-PD model modified by Wright and Duffull was assessed using prediction-corrected visual predictive checks, focusing on clinical characteristics, including age, renal function, and individual prediction error. The external dataset included 232 patients who received an initial warfarin daily dose of 3.2 ± 1.28 mg with 2278 PT-INR points (median [range] follow-up period of 23 d [7-28]). Prediction-corrected visual predictive checks carried a propensity for underprediction. Additionally, age >60 years, body mass index ≤25 kg/m², and estimated glomerular filtration rate ≤60 mL/min/1.73 m² had a pronounced tendency to underpredict PT-INR. However, Bayesian prediction using four prior observations reduced underprediction. To improve the prediction performance of these special populations, further studies are required to construct a model to predict warfarin dose requirements in Japanese patients.

Usefulness of quantitative 99mTc-pyrophosphate SPECT/CT for predicting the prognosis of patients with wild-type transthyretin cardiac amyloidosis

PURPOSE

Wild-type transthyretin-related amyloidosis cardiomyopathy (ATTRwt-CM) is an increasingly recognized cause of heart failure especially in elderly patients. The purpose of the present study was to determine retrospectively whether the quantitative indices of ^99mTc-pyrophosphate (PYP) SPECT/CT help to predict the prognosis of ATTRwt-CM patients when compared with other clinical parameters.

MATERIALS AND METHODS

Sixty-eight patients with biopsy-proven ATTRwt-CM who underwent PYP SPECT/CT were enrolled. Baseline clinical characteristics, echocardiographic parameters, and qualitative and/or quantitative indices of planar and SPECT/CT imaging in PYP scintigraphy for each patient were included. For quantitative analysis of SPECT/CT, the accumulation ratio of PYP in the septum, posterior, anterior, lateral, and apex walls to the cavity pool was calculated as the septal wall-to-cavity ratio (Se/C), lateral wall-to-cavity ratio (La/C), anterior wall-to-cavity ratio (An/C), inferior wall-to-cavity ratio (In/C), and apical wall-to-cavity ratio (Ap/C), respectively. Endpoints for prognostic accuracy evaluation were cardiac death or hospitalization due to heart failure. Event-free survival rate was evaluated through Cox proportional hazards regression analysis, providing estimated hazard ratios (HRs) with 95% confidence intervals (CIs) and Kaplan-Meier curves.

RESULTS

High-sensitivity cardiac troponin T (hs-cTnT), La/C, age, interventricular septal thickness in diastole, and E/e' ratio in the septal wall were significantly associated with event-free survival (P < 0.05). For a multivariable Cox proportional hazards analysis, hs-cTnT (HR 1.153; 95% CI 1.034-1.286; P < 0.01), La/C (HR 2.091; 95% CI 1.012-4.322; P = 0.046), and age (HR 1.116; 95% CI 1.007-1.238; P = 0.037) were significant independent prognostic factors.

CONCLUSION

This study indicated that the quantitative indices of PYP SPECT/CT can help to predict the prognosis of ATTRwt-CM patients.

Detection of acute rib fractures on CT images with convolutional neural networks: effect of location and type of fracture and reader's experience

PURPOSE

The evaluation of all ribs on thin-slice CT images is time consuming and it can be difficult to accurately assess the location and type of rib fracture in an emergency. The aim of our study was to develop and validate a convolutional neural network (CNN) algorithm for the detection of acute rib fractures on thoracic CT images and to investigate the effect of the CNN algorithm on radiologists' performance.

METHODS

The dataset for development of a CNN consisted of 539 thoracic CT scans with 4906 acute rib fractures. A three-dimensional faster region-based CNN was trained and evaluated by using tenfold cross-validation. For an observer performance study to investigate the effect of CNN outputs on radiologists' performance, 30 thoracic CT scans (28 scans with 90 acute rib fractures and 2 without rib fractures) which were not included in the development dataset were used. Observer performance study involved eight radiologists who evaluated CT images first without and second with CNN outputs. The diagnostic performance was assessed by using figure of merit (FOM) values obtained from the jackknife free-response receiver operating characteristic (JAFROC) analysis.

RESULTS

When radiologists used the CNN output for detection of rib fractures, the mean FOM value significantly increased for all readers (0.759 to 0.819, P = 0.0004) and for displaced (0.925 to 0.995, P = 0.0028) and non-displaced fractures (0.678 to 0.732, P = 0.0116). At all rib levels except for the 1st and 12th ribs, the radiologists' true-positive fraction of the detection became significantly increased by using the CNN outputs.

CONCLUSION

The CNN specialized for the detection of acute rib fractures on CT images can improve the radiologists' diagnostic performance regardless of the type of fractures and reader's experience. Further studies are needed to clarify the usefulness of the CNN for the detection of acute rib fractures on CT images in actual clinical practice.

A National Survey on Safety Management at MR Imaging Facilities in Japan

PURPOSE

To investigate safety management at Japanese facilities performing human MRI studies.

METHODS

All Japanese facilities performing human MRI studies were invited to participate in a comprehensive survey that evaluated their MRI safety management. The survey used a questionnaire prepared with the cooperation of the Safety Committee of the Japanese Society for Magnetic Resonance in Medicine. The survey addressed items pertaining to the overall MRI safety management, questions on the occurrence of incidents, and questions specific to facility and MRI scanner or examination. The survey covered the period from October 2017 to September 2018. Automated machine learning was used to identify factors associated with major incidents.

RESULTS

Of 5914 facilities, 2015 (34%) responded to the questionnaire. There was a wide variation in the rate of compliance with MRI safety management items among the participating facilities. Among the facilities responding to this questionnaire, 5% reported major incidents and 27% reported minor incidents related to MRI studies. Most major incidents involved the administration of contrast agents. The most influential factor in major incidents was the total number of MRI studies performed at the facility; this number was significantly correlated with the risk of major incidents (P < 0.0001).

CONCLUSION

There were large variations in the safety standards applied at Japanese facilities performing clinical MRI studies. The total number of MRI studies performed at a facility affected the number of major incidents.

Added Value of Contrast-enhanced 3D-FLAIR MR Imaging for Differentiating Cystic Pituitary Adenoma from Rathke's Cleft Cyst

PURPOSE

Half of the surgically proven Rathke's cleft cysts (RCCs) can be preoperatively misdiagnosed as cystic pituitary adenoma (CPA). We aimed to evaluate the usefulness of contrast-enhanced (CE) 3D T2 fluid-attenuated inversion-recovery (3D T2-FLAIR) imaging for differentiating between CPA and RCC.

METHODS

This retrospective study included six patients with RCC (all pathologically confirmed) and six patients with CPA (five pathologically confirmed, one clinically diagnosed). The 12 patients underwent pre- and post-contrast T1-weighted (T1W)- and 3D T2-FLAIR imaging at 3T. Based on the degree of enhancement of the lesion wall, two radiologists independently scored the images using a 3-point grading system. Interobserver agreement was calculated by using the κ coefficient. The statistical significance of grading differences was analyzed with the Mann-Whitney U-test. Another neuroradiologist first interpreted conventional MR images (1st session), and then the reader read images to which the 3D T2-FLAIR images had been added (2nd session). Sensitivity, specificity, and accuracy of the reader's interpretation were calculated.

RESULTS

Interobserver agreement for post-contrast T1W- and 3D T2-FLAIR images was excellent (κ = 1.000 and 0.885, respectively). Although the mean enhancement grade on post-contrast T1W images of RCCs and CPAs was not significantly different, on post-contrast 3D T2-FLAIR images it was significantly higher for RCCs and CPAs (P < 0.05). Three CPAs (50%) showed remarkable, donut-like enhancement along the inner margin of the cyst on CE-3D T2-FLAIR images; this was not the case on CE-T1W images. The sensitivity, specificity, and accuracy of the 2nd session were 1.00, 0.83, and 0.92, respectively, which were improved compared to the 1st session (1.00, 0.50, and 0.75, respectively).

CONCLUSION

CE-3D FLAIR imaging is useful for discriminating CPAs and RCCs.

Can myocardial susceptibility quantification be an imaging biomarker for cardiac amyloidosis?

Purpose

This study aimed to evaluate whether quantification of myocardial susceptibility by cardiac magnetic resonance imaging (CMR) can be an imaging biomarker for cardiac amyloidosis (CA).

Materials and methods

Twenty-six patients with CA underwent CMR, including magnetic phase imaging with a 3.0-T magnetic resonance imaging scanner. Myocardial susceptibility was quantified as a phase shift slope value by magnetic phase analysis. Those values from patients with CA were compared with corresponding values from 18 controls and 15 healthy volunteers. A univariate logistic regression analysis was conducted to identify significant parameters related to CA.

Results

The phase shift slope, a quantitative parameter of myocardial susceptibility, was significantly lower in the CA group compared with the control group and compared with healthy volunteers (p < 0.01). From a total of 17 tested variables, 6 were considered to be significant predictors of CA (p ≤ 0.05) during the univariate analysis. The phase shift slope yielded the best AUC of 0.89 (95% CI = 0.79–0.98) for the prediction of CA (p < 0.01). The phase shift slope was significantly correlated with the end-diastolic thickness of the interventricular septum (r =  − 0.39, p < 0.01) and posterior wall of the left ventricle (r =  − 0.35, p = 0.02).

Conclusion

Myocardial susceptibility analysis by CMR helps in the diagnosis of patients with CA and can be a new quantitative imaging biomarker for CA.

Virtual magnetic resonance lumbar spine images generated from computed tomography images using conditional generative adversarial networks

INTRODUCTION

The aim of this study was to generate virtual Magnetic resonance (MR) from computed tomography (CT) using conditional generative adversarial networks (cGAN).

METHODS

We selected examinations from 22 adults who obtained their CT and MR lumbar spine examinations. Overall, 4 examinations were used as test data, and 18 examinations were used as training data. A cGAN was trained to generate virtual MR images from the CT images using the corresponding MR images as targets. After training, the generated virtual MR images from test data in epochs 1, 10, 50, 100, 500, and 1000 were compared with the original ones using the mean square error (MSE) and structural similarity index (SSIM). Additionally, two radiologists also performed qualitative assessments.

RESULTS

The MSE of the virtual MR images decreased as the epoch of the cGANs increased from the original CT images: 8876.7 ± 1192.9 (original CT), 1567.5 ± 433.9 (Epoch 1), 1242.4 ± 442.0 (Epoch 10), 1065.8 ± 478.1 (Epoch 50), 1276.1 ± 718.9 (Epoch 100), 1046.7 ± 488.2 (Epoch 500), and 1031.7 ± 400.0 (Epoch 1000). No considerable differences were observed in the qualitative evaluation between the virtual MR images and the original ones, except in the structure of the spinal canal.

CONCLUSION

Virtual MR lumbar spine images using cGANs could be a feasible technique to generate near-MR images from CT without MR examinations for evaluation of the vertebral body and intervertebral disc.

IMPLICATIONS FOR PRACTICE

Virtual MR lumbar spine images using cGANs can offer virtual CT images with sufficient quality for attenuation correction for PET or dose planning in radiotherapy.

Clinical predictors of nephrotoxicity associated with teicoplanin: Meta-analysis and meta-regression

Teicoplanin is a glycopeptide antibiotic against methicillin-resistant Staphylococcus aureus infections. However, the impact of clinical characteristics on nephrotoxicity associated with teicoplanin has not been determined. This meta-analysis aimed to investigate the relationship between clinical characteristics and nephrotoxicity associated with teicoplanin. We identified clinical research published from January 1975 to June 2021 using PubMed, Cochrane Library, and Scopus, which described the nephrotoxicity associated with teicoplanin. Meta-analysis determined the incidence of nephrotoxicity. Using meta-regression analysis, we evaluated the impact of clinical characteristics on outcomes. Of the 567 articles, eight articles including 634 patients were analysed. The overall incidence of nephrotoxicity associated with teicoplanin was 11.0% (95% confidence interval: 8.0-13.0) for the fixed-effect model. Additionally, patients with >65 years had a high trend for the risk of nephrotoxicity compared to those with ≤65 years (>65 years; 12.0% [95% confidence interval: 9.0-15.0] vs. ≤65 years; 7.0% [95% confidence interval: 3.0-12.0], p = 0.09) for the fixed-effect model. Meta-regression analysis demonstrated that only serum albumin level negatively correlated with the risk of nephrotoxicity (y = -17.0 x + 56.7, r = 0.74, p = 0.01). This meta-analysis ascertained that hypoalbuminemia leads to nephrotoxicity associated with teicoplanin.

Different contribution of sympathetic nerve activity to arterial velocity pulse index in hypertensive patients with and without diastolic dysfunction

Introduction

Left ventricular diastolic dysfunction (LVDD) is the main cause of heart failure with preserved ejection fraction (HFpEF). LVDD is related not only to arterial stiffness but also sympathetic nerve activity (SNA). Recent study demonstrated that increased muscle sympathetic nerve activity (MSNA) may be one of contributing factor for arterial stiffness. In clinical practice, Cardio-ankle vascular index (CAVI) provides a reproducible index of arterial stiffness, independent of blood pressure (BP). Recently, Arterial Velocity pulse Index (AVI), which is an index of arterial reflected waves, have been proposed as new index of arterial stiffness. We reported that AVI was associated with MSNA in hypertensive (HT) patients. However, it is still uncertain the effect of LVDD on the association between AVI and SNA in HT patients. Thus, we tested the hypothesis that AVI would be increased and related to MSNA in HT patients with LVDD.

Methods

Patients with essential HT subjects were included in this study. HT was diagnosed as systolic blood pressure (SBP) ≥140mmHg or diastolic blood pressure (DBP) ≥90mmHg. Patients with secondary HT was excluded. AVI was measured from left upper arm by NAS-1000 (Nihon Koden, Japan). CAVI was measured by VaSera VS-1500A (Fukuda Denshi, Japan). Transthoracic echocardiography was performed by trained sonographers. SNA was evaluated by direct recording of MSNA from peroneal nerves.

Results

25 HT patients were included (age 63±14 years, Male/Female 9/16). They were divided into two groups according to E/e' (no LVDD group, E/e' ≤9, N=12; LVDD group, E/e' &gt;9, N=13). There were no significant differences between no LVDD and LVDD groups in age (63±9 vs 69±9 years p=0.205), body mass index (23±3 vs 24±4 p=0.355), BP (SBP 139±16 vs 144±20mmHg p=0.524, DBP 87±15 vs 78±14mmHg p=0.167). LV Ejection Fraction (EF) and Stroke Volume (SV) did not differ between two groups (EF 66±7 vs 69±6% p=0.471, SV 58±7 vs 62±14ml p=0.599). MSNA had tendency to increase in LVDD group compared to no LVDD group (MSNA 53±10 vs 44±12 bursts/100 heartbeats, p=0.052). Contrary to our hypothesis, AVI and CAVI did not differ between two groups (AVI 27±7 vs 29±7 p=0.398, CAVI 8.7±1.4 vs 8.6±1.4 p=0.894). However, a significant correlation was seen between AVI and MSNA in no LVDD group (r=0.57, p&lt;0.05), but no correlation in LVDD group. There is no correlation between CAVI and MSNA in no LVDD and LVDD group. Significant relationship was observed between AVI and CAVI in LVDD group (r=0.61, p&lt;0.05), but no relationship in no LVDD group.

Conclusion

AVI was significantly associated with MSNA in HT patients without LVDD, but not with LVDD. CAVI was related to AVI in HT patients with LVDD, but not without LVDD. MSNA was slightly increased in HT patients with LVDD compared to without LVDD. These results indicate that augmented SNA could contribute to the increase in arterial stiffness in HT patients without LVDD, however, this contribution might be attenuated in HT patients with LVDD.

Funding Acknowledgement

Type of funding sources: None.

Effect of pulmonary vein isolation on left atrial remodeling and muscle sympathetic nerve activity in patients with atrial fibrillation

Background

Catheter ablation (CA) for atrial fibrillation (AF) improves left ventricular function and induces left atrium reverse remodeling (LARR). CA is also associated with the modulation of ganglionated plexi in the left atrium (LA), including stretch-sensitive sympathetic and parasympathetic nerve mechanoreceptors. Increased filling pressure and enlargement of LA stimulate stretch-sensitive sympathetic nerve mechanoreceptors in heart failure, which contribute augmented sympathetic nerve activity. However, little is known about an effect of CA on the interaction between the changes of LARR and sympathetic nerve activity.

Purpose

To test the hypothesis that CA induce the reduction in sympathetic nerve activity in accordance with LARR in patients with atrial fibrillation.

Methods

This study was conducted as a retrospective, observational study. Twenty-eight AF patients (65.4±12.1 years old) were included in this study. We measured mean blood pressure (BP), heart rate (HR), brain natriuretic peptide (BNP), and direct recording of muscle sympathetic nerve activity (MSNA) using microneurography technique before and 12 weeks after CA. Echocardiogram was also performed to assess LARR and left ventricular function. To evaluate the interaction between LARR and MSNA, AF patients were divided into two groups by presence (LARR group; n=18) and absence (no LARR group; n=10) of LARR according to left atrium volume index (LAVi) following CA.

Results

No significant differences were observed at baseline in BP, MSNA and LAVi between two groups. BP did not change significantly after CA in both groups. HR significantly increased in the LARR group (63.1±5.7 vs 69.9±7.8, p&lt;0.01) compared to no LARR group. CA significantly reduced MSNA in the LARR group (37.8±10.1 vs 24.9±8.8 bursts/min, p&lt;0.01), but there was no significant change in the no LARR group. The septal E/e' ratio (11.3±3.8 vs 9.8±2.9, p&lt;0.05), left ventricular end-systolic volume index (LVESVi) (24.4±11.9 vs 19.6±7.8 ml/m2, p&lt;0.05) and Ln BNP (4.0±1.2 vs 3.3±1.0 log/pg/ml, p&lt;0.05) were also significantly improved in the LARR group. On the other hand, in the no LARR group, there were no significancy in the changes of the septal E/e' ratio, LVESVi and Ln BNP. LVEF was not significantly changed in both two groups.

Conclusion

Our study shows CA reduced MSNA accompanied by LARR in AF patients. The reduction in MSNA, septal E/e' ratio, LVESVi and Ln BNP were all more pronounced in the LARR group compared to the no LARR group. These findings suggest that LARR is associated with the reduction in MSNA in AF patients, which was attributed to CA-induced modulation of stretch-sensitive sympathetic nerve mechanoreceptors.

Funding Acknowledgement

Type of funding sources: None.

Age differences in the association between arterial velocity pulse index and muscle sympathetic nerve activity in hypertensive patients

Background

Increased arterial stiffness characterize by aging. It is reported that age-related increases in muscle sympathetic nerve activity (MSNA) may be one of contributing factor for arterial stiffness. Arterial reflected wave was composed of SNA and aging. Increased arterial reflected wave partly plays an important role in blood pressure. Recently, we reported that arterial velocity pulse index (AVI), a novel index of arterial reflected waves, was associated with MSNA in hypertensive patients. It is still uncertain the effect of age on the association between AVI and SNA in hypertensive patients.

Method

Patients with essential HT and matched non-hypertensive control subjects were included in this study. HT was diagnosed as systolic blood pressure (SBP) ≥140 mmHg or diastolic blood pressure (DBP) ≥90 mmHg. AVI was measured from left upper arm by NAS-1000. SNA was evaluated by direct recording of muscle sympathetic nerve activity (MSNA) from peroneal nerves.

Results

45 HT patients and 46 control subjects were included. Age, SBP and DBP were significantly increased in HT group compared to control (Age 63±14 vs 42±16 years, p&lt;0.001; SBP 144±16 vs 115±9 mmHg, p&lt;0.001; DBP 80±14 vs 67±9 mmHg, p&lt;0.001). MSNA and AVI were significantly increased in HT group compared to control (MSNA 34±10 vs 25±8 bursts/min, p&lt;0.05; AVI 28±9 vs 17±5, p&lt;0.05). AVI was significantly correlated with MSNA, age, and SBP in HT group. HT group was divided into two groups according to their age (group 1, age ≤63 N=21, group 2, age ≥64 N=26). AVI in group 1 showed correlation with MSNA (r=0.59, p&lt;0.05), but no correlation was seen in group 2. However excluded SBP&gt;160 mmHg subjects in group 2, significant correlation was clarified between AVI and MSNA (r=0.62, p&lt;0.05).

Conclusion

The relationship between AVI and MSNA in HT patients is preserved regardless of aging, however, high blood pressure over 160mmHg might obscure its correlation. These results indicate that AVI is useful to estimate sympathetic nerve activity in high aging HT patient treated &lt;160 blood pressure.

Funding Acknowledgement

Type of funding sources: None.

Deep Learning-based Reconstruction for Lower-Dose Pediatric CT: Technical Principles, Image Characteristics, and Clinical Implementations

Optimizing the CT acquisition parameters to obtain diagnostic image quality at the lowest possible radiation dose is crucial in the radiosensitive pediatric population. The image quality of low-dose CT can be severely degraded by increased image noise with filtered back projection (FBP) reconstruction. Iterative reconstruction (IR) techniques partially resolve the trade-off relationship between noise and radiation dose but still suffer from degraded noise texture and low-contrast detectability at considerably low-dose settings. Furthermore, sophisticated model-based IR usually requires a long reconstruction time, which restricts its clinical usability. With recent advances in artificial intelligence technology, deep learning-based reconstruction (DLR) has been introduced to overcome the limitations of the FBP and IR approaches and is currently available clinically. DLR incorporates convolutional neural networks-which comprise multiple layers of mathematical equations-into the image reconstruction process to reduce image noise, improve spatial resolution, and preserve preferable noise texture in the CT images. For DLR development, numerous network parameters are iteratively optimized through an extensive learning process to discriminate true attenuation from noise by using low-dose training and high-dose teaching image data. After rigorous validations of network generalizability, the DLR engine can be used to generate high-quality images from low-dose projection data in a short reconstruction time in a clinical environment. Application of the DLR technique allows substantial dose reduction in pediatric CT performed for various clinical indications while preserving the diagnostic image quality. The authors present an overview of the basic concept, technical principles, and image characteristics of DLR and its clinical feasibility for low-dose pediatric CT. ^©RSNA, 2021.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

Background The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipid-poor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand. Purpose To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] × 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test. Results A total of 220 patients (mean age ± standard deviation, 66 years ± 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of >210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of ≤21 HU), contrast-enhanced attenuation (3% [four of 131 adenomas; 95% CI: 1, 8] at a threshold of >120 HU), and absolute enhancement (24% [32 of 131 adenomas; 95% CI: 17, 33] at a threshold of >74 HU; all P < .001). The sensitivities of the relative enhancement ratio were 100% (58 of 58 adenomas; 95% CI: 94, 100), 83% (52 of 63 adenomas; 95% CI: 71, 91), and 30% (three of 10 adenomas; 95% CI: 7, 65) for adenomas measuring unenhanced attenuation of more than 10 HU up to 20 HU, 21-30 HU, and more than 30 HU, respectively. Conclusion A relative enhancement ratio threshold of greater than 210%, measured at unenhanced and portal venous phase CT, accurately differentiated lipid-poor adenomas from nonadenomas, particularly for lesions with unenhanced attenuation of 10-30 HU. © RSNA, 2021 Online supplemental material is available for this article.