Common Carotid Artery Volume Flow: A Comparison Study between Ultrasound Vector Flow Imaging and Phase Contrast Magnetic Resonance Imaging

Comparison Between Attenuation Measurement and the Controlled Attenuation Parameter for the Assessment of Hepatic Steatosis Based on MRI Images

BACKGROUND AND AIMS

This study prospectively compared the diagnostic accuracies of the improved Attenuation Measurement (iATT) algorithm and the Controlled Attenuation Parameter (CAP) and assessed the interchangeability of iATT with magnetic resonance imaging-derived proton density fat fraction (MRI-derived PDFF).

METHODS

Patients with chronic liver disease were prospectively enrolled and underwent iATT, CAP and MRI-derived PDFF measurements for hepatic steatosis evaluation. According to MRI-derived PDFF values, steatosis grades were categorised as steatosis (S)0 (< 5.2%), S1 (≥ 5.2%, < 11.3%), S2 (≥ 11.3%, < 17.1%) and S3 (≥ 17.1%). Correlation coefficients (CCs) were determined, diagnostic performances were compared by the area under the receiver operating characteristic curve (AUROC) and agreement was evaluated using the calculated percentage error (PE) and expected limit of agreement (LOA).

RESULTS

A total of 414 patients (median age 64 years, 203 females) were evaluated. The CC between iATT and MRI-derived PDFF was 0.727 (95% confidence interval [CI] 0.678-0.770), which was higher than that between CAP and MRI-derived PDFF at 0.615 (95% CI 0.551-0.672) (p < 0.001). The AUROCs of iATT for ≥ S1, ≥ S2 and ≥ S3 were 0.901 (95% CI 0.870-0.931), 0.878 (95% CI 0.846-0.910) and 0.839 (95% CI 0.794-0.883), respectively. The diagnostic performances of iATT for ≥ S1 and ≥ S2 showed significantly higher AUROCs than those of CAP (p < 0.001, p = 0.036, respectively). The calculated PE and the expected LOA for CAP and iATT were 38.94% and 22.66% and 32.94% and 30.03%, respectively.

CONCLUSIONS

iATT was superior to CAP and comparable to MRI-derived PDFF in assessing hepatic steatosis.

TRIAL REGISTRATION

This study was registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN000047411).

iATT liver fat quantification for steatosis grading by referring to MRI proton density fat fraction: a multicenter study

BACKGROUND

Several preliminary reports have suggested the utility of ultrasound attenuation coefficient measurements based on B-mode ultrasound, such as iATT, for diagnosing steatotic liver disease. Nonetheless, evidence supporting such utility is lacking. This prospective study aimed to investigate whether iATT is highly concordant with magnetic resonance imaging (MRI)-based proton density fat fraction (MRI-PDFF) and could well distinguish between steatosis grades.

METHODS

A cohort of 846 individuals underwent both iATT and MRI-PDFF assessments. Steatosis grade was defined as grade 0 with MRI-PDFF < 5.2%, grade 1 with 5.2% MRI-PDFF < 11.3%, grade 2 with 11.3% MRI-PDFF < 17.1%, and grade 3 with MRI-PDFF of 17.1%. The reproducibility of iATT and MRI-PDFF was evaluated using the Bland-Altman analysis and intraclass correlation coefficients, whereas the diagnostic performance of each steatosis grade was examined using receiver operating characteristic analysis.

RESULTS

The Bland-Altman analysis indicated excellent reproducibility with minimal fixed bias between iATT and MRI-PDFF. The area under the curve for distinguishing steatosis grades 1, 2, and 3 were 0.887, 0.882, and 0.867, respectively. A skin-to-capsula distance of ≥ 25 mm was identified as the only significant factor causing the discrepancy. No interaction between MRI-logPDFF and MRE-LSM on iATT values was observed.

CONCLUSIONS

Compared to MRI-PDFF, iATT showed excellent diagnostic accuracy in grading steatosis. iATT could be used as a diagnostic tool instead of MRI in clinical practice and trials. Trial registration This study was registered in the UMIN Clinical Trials Registry (UMIN000047411).

B-mode shear wave elastography can be an alternative method to vibration-controlled transient elastography according to a moderate-scale population study

PURPOSE

We aimed to compare vibration-controlled transient elastography (VCTE) with shear wave elastography (SWE) without previous analysis and generate regression equations between VCTE and new point SWE using combination-elastography.

METHODS

Overall, 829 patients with chronic liver disease were enrolled in this study. Patients with a skin-liver capsule distance > 25 mm were excluded. The reproducibility of VCTE and SWE was confirmed in a phantom study and a clinical study. Considering that combination-elastography allows measurement based on strain elastography, a similar analysis was performed for the liver fibrosis index (LFI), which is a quantitative value for evaluation of liver fibrosis calculated using strain elastography image features. Regression equations between the VCTE and SWE values were obtained based on linear regression analysis.

RESULTS

In the phantom study and clinical study, there was a strong correlation between VCTE and SWE [r = 0.995 (p < 0.001) and r = 0.747 (p < 0.001), respectively). The regression equation between VCTE and SWE was VCTE (kPa) = 1.09 × point SWE (kPa) - 0.17. The Bland-Altman plots revealed no statistically significant bias. Meanwhile, there was no correlation between VCTE and LFI (r = 0.279). There was a statistically significant bias between VCTE and LFI in the Bland-Altman plots. The inter-operator reliability showed a good intraclass correlation coefficient of 0.760 (95% confidence interval: 0.720-0.779).

CONCLUSION

Liver stiffness measured using point SWE was comparable to that measured using VCTE.

Intra-individual comparison of liver stiffness measurements by magnetic resonance elastography and two-dimensional shear-wave elastography in 888 patients

PURPOSE

Quantitative elastography methods, such as ultrasound two-dimensional shear-wave elastography (2D-SWE) and magnetic resonance elastography (MRE), are used to diagnose liver fibrosis. The present study compared liver stiffness determined by 2D-SWE and MRE within individuals and analyzed the degree of agreement between the two techniques.

METHODS

In total, 888 patients who underwent 2D-SWE and MRE were analyzed. Bland-Altman analysis was performed after both types of measurements were log-transformed to a normal distribution and converted to a common set of units using linear regression analysis for differing scales. The expected limit of agreement (LoA) was defined as the square root of the sum of the squares of 2D-SWE and MRE precision. The percentage difference was expressed as (2D-SWEMRE)/ mean of the two methods×100.

RESULTS

A Bland-Altman plot showed that the bias and upper and lower LoAs (ULoA and LLoA) were 0.0002 (95% confidence interval [CI], -0.0057 to 0.0061), 0.1747 (95% CI, 0.1646 to 0.1847), and -0.1743 (95% CI, -0.1843 to -0.1642), respectively. In terms of percentage difference, the mean, ULoA, and LLoA were -0.5944%, 19.8950%, and -21.0838%, respectively. The calculated expected LoA was 17.1178% (95% CI, 16.6353% to 17.6002%), and 789 of 888 patients (88.9%) had a percentage difference within the expected LoA. The intraclass correlation coefficient of the two methods indicated an almost perfect correlation (0.8231; 95% CI, 0.8006 to 0.8432; P<0.001).

CONCLUSION

Bland-Altman analysis demonstrated that 2D-SWE and MRE were interchangeable within a clinically acceptable range.

Intra-individual Comparisons of the Ultrasound-Guided Attenuation Parameter and the Magnetic Resonance Imaging-Based Proton Density Fat Fraction Using Bias and Precision Statistics

Ultrasound-based techniques using the attenuation coefficient, including the ultrasound-guided attenuation parameter (UGAP), have been developed for the quantification of hepatic steatosis. The magnetic resonance imaging-based proton density fat fraction (MRI-PDFF) is considered to be more accurate than liver biopsy for liver fat quantification. The aim of this study was to perform intra-individual comparisons of UGAP and MRI-PDFF for determining hepatic steatosis grade. The study enrolled 309 patients who underwent UGAP and MRI-PDFF measurements. Bland-Altman analysis was conducted after transforming MRI-PDFF values to a normal distribution and converted to a common set of units using linear regression analysis for differing scales. The expected limits of agreement (LOA) was defined as the square root of the sum of the squares of UGAP and MRI-PDFF precision. A Bland-Altman plot revealed that the bias and upper and lower LOAs (ULOA and LLOA) were -0.0047, 0.1160 and -0.1255, respectively. The percentage difference indicated that the mean, ULOA and LLOA were -1.1434%, 18.1723% and -20.4590%, respectively. The calculated expected LOA was 18.5449%, and 283 of 309 patients (91.6%) had a percentage difference within 18.5449%. Bland-Altman analysis revealed that UGAP and MRI-PDFF were interchangeable within a clinically acceptable range.

Quantitative Evaluation of Post-stenotic Blood Flow Disturbance in Canine Femoral Artery Stenosis Model: An Early Experience With Vector Flow Imaging

Objective

To investigate the value of Vector Flow Imaging (V Flow) in the assessment of post-stenotic turbulence in the canine arterial stenosis model.

Materials and Methods

Canine femoral artery stenosis models were established using ameroid constrictors in 12 beagle dogs. 50% and then 70% femoral artery stenoses were confirmed by selective femoral artery angiography. V Flow was used to measure femoral artery flow turbulence index (Tur) preoperatively as a baseline. After establishing of a 50% and then 70% stenoses, the Tur indices were recorded in the femoral artery at 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 mm distal to the stenosis.

Results

Baseline Tur indices of normal canine femoral arteries were <1% in 11 of 12 cases (91.7%). Distal to a 50% stenosis, the Tur index (>1%) was recorded in 83.3–100% cases between 1 and 9 mm, 41.7–58.3% between 11 and 17 mm, and 16.7% at 19 mm. For a 70% stenosis, the Tur index (>1%) occurred in 81.8–100% cases between 1 and 17 mm distal to the stenosis, and 63.6% at 19 mm. The Tur index peaked around 7 mm or 2.3 times of the initial vessel diameter (3 mm) downstream for a 50% stenosis and 11 mm or 3.7 times of vessel diameter downstream for a 70% stenosis.

Conclusion

V Flow with Tur index measurement adds quantitative information of post-stenotic turbulence when assessing an arterial stenosis with ultrasound. Tur index of 1% seems a useful threshold for assessment of flow turbulence in this small sample study. Further studies with larger sample size are needed to evaluate the value of V Flow in clinical applications.