Feature tracking computed tomography-derived left ventricular global longitudinal strain in patients with aortic stenosis: a comparative analysis with echocardiographic measurements

BackgroundLeft ventricular (LV) systolic function is a prognostic factor in patients with severe aortic stenosis (AS). Multi-detector row computed tomography (MDCT) data are key in the evaluation of patients undergoing transcatheter aortic valve implantation (TAVI) and when acquired retrospectively, LV systolic function can be assessed. Novel software permits assessment of LV global longitudinal strain (GLS) from MDCT data.ObjectivesThe present study investigated the feasibility of feature tracking MDCT-derived LV GLS and its agreement with echocardiographic LV GLS in patients treated with TAVI.MethodsLV GLS was measured on transthoracic echocardiography using speckle tracking analysis and on dynamic MDCT using feature tracking technology. Agreement between the measurements of two different modalities was assessed using Bland-Altman analysis.ResultsA total of 214 patients (51% male, mean age: 80 ± 7 years) were analysed. Mean LV GLS on echocardiography was −13.91 ± 4.32%, whereas mean feature tracking MDCT-derived GLS was −12.46 ± 3.97%. Correlation of measurements between feature tracking MDCT-derived LV GLS and echocardiographic LV GLS demonstrated a large effect size (r = 0.791, p < 0.001). On Bland-Altman analysis, feature tracking MDCT-derived strain analysis underestimated LV GLS compared to echocardiography with a mean difference of 1.44% (95% limits of agreement −3.85% - 6.73%).ConclusionsAssessment of LV GLS on dynamic feature tracking MDCT data is feasible in TAVI patients. Compared to speckle tracking echocardiography, feature tracking MDCT underestimates the value of LV GLS.     

Myocardial tagging and strain analysis at 3 Tesla: comparison with 1.5 Tesla imaging

PURPOSE: To determine whether imaging at 3 T could improve and prolong the tag contrast compared to images acquired at 1.5 T in normal volunteers, and whether such improvement would translate into the ability to perform strain measurements in diastole. MATERIALS AND METHODS: Normal volunteers (N = 13) were scanned at 1.5 T (GE Signa CV/i) and 3.0 T (GE VH/i). An ECG-triggered, segmented k-space, spoiled-gradient-echo grid-tagged sequence was used during cine acquisition. Tag contrast was determined by the difference of the mean signal intensity (SI) of the tagline to the mean SI of the myocardium divided by the standard deviation (SD) of the noise (CNR(tag)). Matched short-axis (SA) slices were analyzed. Strain measurements were performed on images using a 2D strain analysis software program (harmonic phase (HARP)). RESULTS: The average CNR(tag) over the cardiac cycle was superior at 3 T compared to 1.5 T for all slices (3 T: 23.4 +/- 12.1, 1.5 T: 9.8 +/- 8.4; P < 0.0001). This difference remained significant at cycle initiation, end-systole, and the end R-R interval (at cycle termination: 3 T = 14.0 +/- 11.0 vs. 1.5 T = 4.4 +/- 3.5; P < 0.01). Strain measures were obtainable only in early systole for 1.5 T images, but were robust throughout the entire R-R interval for 3 T images. CONCLUSION: Imaging at 3 T had a significant benefit for myocardial tag persistence through the cardiac cycle. The improvement allowed strain analysis to be performed into diastole.     

Global longitudinal strain assessment by computed tomography in severe aortic stenosis patients - Feasibility using feature tracking analysis

BackgroundGlobal longitudinal strain (GLS) detects subclinical myocardial changes in patients with aortic stenosis (AS). Although GLS is typically measured by transthoracic echocardiography (TTE), assessment by multiphasic gated computed tomography angiography (CTA) has become recently available. We sought to evaluate the feasibility of CTA-derived GLS assessment and compare its agreement with TTE using the same post-processing software in severe AS patients undergoing transcatheter aortic valve replacement (TAVR) evaluation.MethodsWe evaluated patients with severe AS, sinus rhythm and adequate image quality for GLS analysis by both CTA and TTE pre-TAVR using 2D CT-Cardiac Performance Analysis prototype software (TomTec). The 18-segment model was used for GLS analysis by averaging the three long-axis views in both CTA and TTE studies. Agreement was assessed using linear regression and Bland-Altman analysis.ResultsA total of 123 consecutive patients were included (mean age 84 ± 7 years, 45% female). The mean left ventricular ejection fraction (LVEF) by CTA and TTE were similar 53 ± 14% for both. On average, CTA-derived GLS was greater than by TTE (−20 ± 6.5% vs. −16 ± 4.9%, respectively, p < 0.001). There was a moderate correlation between GLS assessed by CTA vs. TTE (r = 0.62, p < 0.001), although variability between imaging methods existed. The correlation between GLS and LVEF was strong (r = −0.90, p < 0.001 for CTA, r = −0.88, p < 0.001 for TTE) using the same imaging modality.ConclusionCTA-derived GLS assessment is feasible in selected patients with sinus rhythm and adequate image quality. The agreement of GLS between TTE and CTA is moderate but not interchangeable suggesting a potential modality-specific GLS threshold.     

Quantification of myocardial strain at early systole in mouse heart: Restoration of undeformed tagging grid with single‐point HARP

Purpose:

To develop accurate strain and torsion quantification method for the assessment of myocardial contraction in mice by MRI tagging.

Materials and Methods:

Ventricular wall motion at baseline and during β‐adrenergic stimulation was assessed in mice using MRI tagging. Myocardial strain and torsion were quantified using finite element analysis method. A harmonic phase (HARP) based method was developed for the restoration of undeformed taglines for more accurate calculation of myocardial wall strain and torsion.

Results:

Myocardial deformation was observed at early systole (<20 msec after QRS) both at baseline and during β‐adrenergic stimulation. The HARP‐based method allowed robust restoration of undeformed taglines that can be used as the reference in finite element analysis of the tagged images. Without such correction for myocardial deformation in the reference image, inaccuracy in strain quantification underestimated significant strain development at early systole in dobutamine‐stimulated hearts.

Conclusion:

The HARP‐based method developed in the current study enabled automated restoration of undeformed taglines in mouse hearts, leading to more accurate calculation of myocardial wall strain and torsion during dobutamine stimulation. J. Magn. Reson. Imaging 2010;32:608–614. © 2010 Wiley‐Liss, Inc.     

Right coronary artery flow velocity and volume assessment with spiral K‐space sampled breathhold velocity‐encoded MRI at 3 tesla: Accuracy and reproducibility

Purpose:

To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity‐encoded (VE) MRI with spiral k‐space sampling at 3 Tesla.

Materials and Methods:

Flow velocity assessment was performed using VE MRI with spiral k‐space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 ± 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA).

Results:

MRI‐measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region‐of‐interest segmentation was used. Using constricted region‐of‐interest segmentation with lumen size equal to ground‐truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra‐ and inter‐observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes.

Conclusion:

3T breathhold VE MRI with spiral k‐space sampling enables accurate and reproducible assessment of RCA flow velocity. J. Magn. Reson. Imaging 2010;31:1215–1223. © 2010 Wiley‐Liss, Inc.     

Reproducibility of 4D cardiac computed tomography feature tracking myocardial strain and comparison against speckle-tracking echocardiography in patients with severe aortic stenosis

BackgroundMyocardial strain is an established parameter for the assessment of cardiac function and routinely derived from speckle tracking echocardiography (STE). Novel post-processing tools allow deformation imaging also by 4D cardiac computed tomography angiography (CCT). This retrospective study aims to analyze the reproducibility of CCT strain and compare it to that of STE.MethodsLeft (LV) and right ventricular (RV), and left atrial (LA) ejection fraction (EF), dimensions, global longitudinal (GLS), circumferential (GCS) and radial strain (GRS) were determined by STE and CCT feature tracking in consecutive patients with severe aortic stenosis evaluated for transcatheter aortic valve implantation.Results106 patients (mean age 79.9 ?± ?7.8, 44.3% females) underwent CCT at a median of 3 days (IQR 0–28 days) after STE. In CCT, strain measures showed good to excellent reproducibility (intra- and inter-reader intraclass correlation coefficient ≥0.75) consistently in the LV, RV and LA. In STE, only LV GLS and LA GLS yielded good reproducibility, whereas LV GCS and LV GRS showed moderate, and RV GLS and free wall longitudinal strain (FWLS) poor reproducibility. Agreement between CCT and STE was strong for LV GLS only, while other strain features displayed moderate (LV GCS, LA GLS) or weak (LV GRS, RV GLS and FWLS) inter-modality correlation.ConclusionLV, RV and LA CCT strain assessments were highly reproducible. While a strong agreement to STE was found for LV GLS, inter-modality correlation was moderate or weak for LV GCS, LV GRS, and RV and LA longitudinal strain, possibly related to poor reproducibility of STE measurements.     

Quantitative and qualitative comparison of 1.5 and 3.0 tesla MRI in patients with chronic liver diseases

Purpose

To compare the quantitative and qualitative image quality intra‐individually, at 1.5 and 3.0 Tesla (T) in patients with chronic liver diseases.

Materials and Methods

The study group included 24 consecutive patients (17 males, 7 females; mean age ± standard deviation 56.5 ± 11.5) who had chronic liver diseases and underwent abdominal MRI for the liver evaluation at both 1.5 and 3.0T within a 4‐month period. All MRI studies were retrospectively evaluated quantitatively and qualitatively. Quantitative analysis was performed by measuring signal to noise ratio (SNR) on various abdominal organs. Qualitative analysis was performed by two reviewers to assess image quality, artifacts, and imaging findings of chronic liver diseases. Quantitative and qualitative analyses findings were compared between 1.5 and 3.0T using the paired Student t‐test and Wilcoxon signed rank test, respectively.

Results

The statistically significant increase in SNRs in various abdominal tissues ranged from 1.3‐ to 3.5‐fold at 3.0T compared to 1.5T. Three‐dimensional gradient echo (3D‐GE) sequences demonstrated significantly higher image quality at 3.0T (P < 0.01), whereas precontrast spoiled gradient echo (SGE) sequences demonstrated significantly higher image quality at 1.5T (P < 0.01). T2‐weighted sequences did not show any significant difference in image quality between 1.5 and 3.0T (P > 0.05).

Conclusion

The SNRs of various abdominal tissues demonstrated significant increases at 3.0T. The image quality of 3D‐GE sequences was higher at 3.0T, whereas the image quality of precontrast SGE sequences was higher at 1.5T. J. Magn. Reson. Imaging 2009;29:869–879. © 2009 Wiley‐Liss, Inc.     

Multicontrast black-blood MRI of carotid arteries: comparison between 1.5 and 3 tesla magnetic field strengths

PURPOSE: To compare black-blood multicontrast carotid imaging at 3T and 1.5T and assess compatibility between morphological measurements of carotid arteries at 1.5T and 3T. MATERIALS AND METHODS: Five healthy subjects and two atherosclerosis patients were scanned in 1.5T and 3T scanners with a similar protocol providing transverse T1-, T2-, and proton density (PD)-weighted black-blood images using a fast spin-echo sequence with single- (T1-weighted) or multislice (PD-/T2-weighted) double inversion recovery (DIR) preparation. Wall and lumen signal-to-noise ratio (SNR) and wall/lumen contrast-to-noise ratio (CNR) were compared in 44 artery cross-sections by paired t-test. Interscanner variability of the lumen area (LA), wall area (WA), and mean wall thickness (MWT) was assessed using Bland-Altman analysis. RESULTS: Wall SNR and lumen/wall CNR significantly increased (P < 0.0001) at 3T with a 1.5-fold gain for T1-weighted images and a 1.7/1.8-fold gain for PD-/T2-weighted images. Lumen SNR did not differ for single-slice DIR T1-weighted images (P = 0.2), but was larger at 3T for multislice DIR PD-/T2-weighted images (P = 0.01/0.03). The LA, WA, and MWT demonstrated good agreement with no significant bias (P 0.5), a coefficient of variation (CV) of < 10%, and intraclass correlation coefficient (ICC) of > 0.95. CONCLUSION: This study demonstrated significant improvement in SNR, CNR, and image quality for high- resolution black-blood imaging of carotid arteries at 3T. Morphologic measurements are compatible between 1.5T and 3T.     

CTA pulmonary artery enlargement in patients with severe aortic stenosis: Prognostic impact after TAVR

BackgroundIdentifying high-risk patients who will not derive substantial survival benefit from TAVR remains challenging. Pulmonary hypertension is a known predictor of poor outcome in patients undergoing TAVR and correlates strongly with pulmonary artery (PA) enlargement on CTA. We sought to evaluate whether PA enlargement, measured on pre-procedural computed tomography angiography (CTA), is associated with 1-year mortality in patients undergoing TAVR.MethodsWe retrospectively included 402 patients undergoing TAVR between July 2012 and March 2016. Clinical parameters, including Society of Thoracic Surgeons (STS) score and right ventricular systolic pressure (RVSP) estimated by transthoracic echocardiography were reviewed. PA dimensions were measured on pre-procedural CTAs. Association between PA enlargement and 1-year mortality was analyzed. Kaplan-Meier and Cox proportional hazards regression analyses were performed.ResultsThe median follow-up time was 433 (interquartiles 339–797) days. A total of 56/402 (14%) patients died within 1 year after TAVR. Main PA area (area-MPA) was independently associated with 1-year mortality (hazard ratio per standard deviation equal to 2.04 [95%-confidence interval (CI) 1.48–2.76], p ​< ​0.001). Area under the curve (95%-CI) of the clinical multivariable model including STS-score and RVSP increased slightly from 0.67 (0.59–0.75) to 0.72 (0.72–0.89), p ​= ​0.346 by adding area-MPA. Although the AUC increased, differences were not significant (p ​= ​0.346). Kaplan-Meier analysis showed that mortality was significantly higher in patients with a pre-procedural non-indexed area-MPA of ≥7.40 ​cm² compared to patients with a smaller area-MPA (mortality 23% vs. 9%; p ​< ​0.001).ConclusionsEnlargement of MPA on pre-procedural CTA is independently associated with 1-year mortality after TAVR.