Influence of aortic valve morphology on vortical structures and wall shear stress

The aim of this paper is to assess the association between valve morphology and vortical structures quantitatively and to highlight the influence of valve morphology/orientation on aorta's susceptibility to shear stress, both proximal and distal. Four-dimensional phase-contrast magnetic resonance imaging (4D PCMRI) data of 6 subjects, 3 with tricuspid aortic valve (TAV) and 3 with functionally bicuspid aortic values (BAV) with right-left coronary leaflet fusion, were processed and analyzed for vorticity and wall shear stress trends. Computational fluid dynamics (CFD) has been used with moving TAV and BAV valve designs in patient-specific aortae to compare with in vivo shear stress data. Vorticity from 4D PCMRI data about the aortic centerline demonstrated that TAVs had a higher number of vortical flow structures than BAVs at peak systole. Coalescing of flow structures was shown to be possible in the arch region of all subjects. Wall shear stress (WSS) distribution from CFD results at the aortic root is predominantly symmetric for TAVs but highly asymmetric for BAVs with the region opposite the raphe (fusion location of underdeveloped leaflets) being subjected to higher WSS. Asymmetry in the size and number of leaflets in BAVs and TAVs significantly influence vortical structures and WSS in the proximal aorta for all valve types and distal aorta for certain valve orientations of BAV. Analysis of vortical structures using 4D PCMRI data (on the left side) and wall shear stress data using CFD (on the right side).

Left ventricular non-compaction in paediatrics: a novel semi-automated imaging technique bridging imaging findings and clinical outcomes

Aims

We set out to design a reliable, semi-automated, and quantitative imaging tool using cardiac magnetic resonance (CMR) imaging that captures LV trabeculations in relation to the morphologic endocardial and epicardial surface, or perimeter-derived ratios, and assess its diagnostic and prognostic utility.

Methods and results

We queried our institutional database between January 2008 and December 2018. Non-compacted (NC)-to-compacted (C) (NC/C) myocardium ratios were calculated and our tool was used to calculate fractal dimension (FD), total mass ratio (TMR), and composite surface ratios (SRcomp). NC/C, FD, TMR, and SRcomp were assessed in relation to LVNC diagnosis and outcomes. Univariate hazard ratios with cut-offs were performed using clinically significant variables to find ‘at-risk’ patients and imaging parameters were compared in ‘at-risk’ patients missed by Petersen Index (PI). Ninety-six patients were included. The average time to complete the semi-automated measurements was 3.90 min (SEM: 0.06). TMR, SRcomp, and NC/C were negatively correlated with LV ejection fraction (LVEF) and positively correlated with indexed LV end-systolic volumes (iLVESVs), with TMR showing the strongest correlation with LVEF (−0.287; P = 0.005) and SRcomp with iLVESV (0.260; P = 0.011). We found 29 ‘at-risk’ patients who were classified as non-LVNC by PI and hence, were missed. When compared with non-LVNC and ‘low-risk’ patients, only SRcomp differentiated between both groups (1.91 SEM 0.03 vs. 1.80 SEM 0.03; P = 0.019).

Conclusion

This method of semi-automatic calculation of SRcomp captured changes in at-risk patients missed by standard methods, was strongly correlated with LVEF and LV systolic volumes and may better capture outcome events.

Ultrafast Computation of Left Ventricular Ejection Fraction by Using Temporal Intensity Variation in Cine Cardiac Magnetic Resonance

Cardiac magnetic resonance enables comprehensive cardiac evaluation; however, intense time and labor requirements for data acquisition and processing have discouraged many clinicians from using it. We have developed an alternative image-processing algorithm that requires minimal user interaction: an ultrafast algorithm that computes left ventricular ejection fraction (LVEF) by using temporal intensity variation in cine balanced steady-state free precession (bSSFP) short-axis images, with or without contrast medium. We evaluated the algorithm's performance against an expert observer's analysis for segmenting the LV cavity in 65 study participants (LVEF range, 12%-70%). In 12 instances, contrast medium was administered before cine imaging. Bland-Altman analysis revealed quantitative effects of LV basal, midcavity, and apical morphologic variation on the algorithm's accuracy. Total computation time for the LV stack was <2.5 seconds. The algorithm accurately delineated endocardial boundaries in 1,132 of 1,216 slices (93%). When contours in the extreme basal and apical slices were not adequate, they were replaced with manually drawn contours. The Bland-Altman mean differences were <1.2 mL (0.8%) for end-diastolic volume, <5 mL (6%) for end-systolic volume, and <3% for LVEF. Standard deviation of the difference was ≤4.1% of LV volume for all sections except the midcavity in end-systole (8.3% of end-systolic volume). We conclude that temporal intensity variation-based ultrafast LVEF computation is clinically accurate across a range of LV shapes and wall motions and is suitable for postcontrast cine SSFP imaging. Our algorithm enables real-time processing of cine bSSFP images on a commercial scanner console within 3 seconds in an unobtrusive automated process.

Dobutamine stress cardiac MRI is safe and feasible in pediatric patients with anomalous aortic origin of a coronary artery (AAOCA)

BACKGROUND

Risk stratification in anomalous aortic origin of a coronary artery (AAOCA) is challenged by the lack of a reliable method to detect myocardial ischemia. We prospectively studied the safety and feasibility of Dobutamine stress-cardiac magnetic resonance (DSCMR), a test with excellent performance in adults, in pediatric patients with AAOCA.

METHODS

Consecutive DSCMR from 06/2014-12/2019 in patients≤20 years old with AAOCA were included. Hemodynamic response and major/minor events were recorded. Image quality and spatial/temporal resolution were evaluated. Rest and stress first-pass perfusion and wall motion abnormalities (WMA) were assessed. Inter-observer agreement was assessed using kappa coefficient.

RESULTS

A total of 224 DSCMR were performed in 182 patients with AAOCA at a median age of 14 years (IQR 12, 16) and median weight of 58.0 kg (IQR 43.3, 73.0). Examinations were completed in 221/224 (98.9%), all studies were diagnostic. Heart rate and blood pressure increased significantly from baseline (p < 0.001). No patient had major events and 28 (12.5%) had minor events. Inducible hypoperfusion was noted in 31/221 (14%), associated with WMA in 13/31 (42%). Inter-observer agreement for inducible hypoperfusion was very good (Κ = 0.87). Asymptomatic patients with inducible hypoperfusion are considered high-risk and those with a negative test are of standard risk.

CONCLUSIONS

DSCMR is feasible in pediatric patients with AAOCA to assess for inducible hypoperfusion and WMA. It can be performed safely with low incidence of major/minor events. Thus, DSCMR is potentially a valuable test for detection of myocardial ischemia and helpful in the management of this patient population.

Breath-hold and free-breathing quantitative assessment of biventricular volume and function using compressed SENSE: a clinical validation in children and young adults

BACKGROUND

Although the breath-hold cine balanced steady state free precession (bSSFP) imaging is well established for assessment of biventricular volumes and function, shorter breath-hold times or no breath-holds are beneficial in children and severely ill or sedated patients.

METHODS

Clinical cardiovascular magnetic resonance (CMR) examinations from September 2019 to October 2019 that included breath-hold (BH) and free-breathing (FB) cine bSSFP imaging accelerated using compressed sensitivity encoding (C-SENSE) factor of 3 in addition to the clinical standard BH cine bSSFP imaging using SENSE factor of 2 were analyzed retrospectively. Patients with structurally normal hearts who could perform consistent BHs were included. Aortic flow measured by phase contrast acquisition was used as a reference for the left ventricular (LV) stroke volume. Comparative analysis was performed for evaluation of biventricular volumes and function, imaging times, quantitative image quality, and qualitative image scoring.

RESULTS

There were 26 patients who underwent all three cine scans during the study period (16.7 ± 6.4 years, body surface area (BSA) 1.6 ± 0.4 m2, heart rate 83 ± 7 beats/min). BH durations of 8 ± 1 s with C-SENSE = 3 were significantly shorter (p < 0.001) by 33% compared to 12 ± 1 s with SENSE = 2. Actual scan time for BH SENSE (4.9 ± 1.2 min) was comparable to that with FB C-SENSE (5.2 ± 1.5 min; p= NS). Biventricular stroke volume and ejection fraction, and LV mass computed using all three sequences were comparable. There was a small but statistically significant (p < 0.05) difference in LV end-diastolic volume (- 3.0 ± 6.8 ml) between BH SENSE and FB C-SENSE. There was a small but statistically significant (p < 0.005) difference in end-diastolic LV (- 5.0 ± 7.7 ml) and RV (- 6.0 ± 8.5 ml) volume and end-systolic LV (- 3.2 ± 4.3 ml) and RV(- 4.2 ± 6.8 ml) volumes between BH C-SENSE and FB C-SENSE. The LV stroke volumes from all three sequences had excellent correlations (r = 0.96, slope = 0.98-1.02) with aortic flow, with overestimation by 2.7 (5%) to 4.6 (8%) ml/beat. The image quality score was Excellent (16 of 26) to Good (10 of 26) with BH SENSE, Excellent (13 of 26) to Good (13 of 26) with BH C-SENSE, and Excellent (3 of 26) to Good (21 of 26) to Adequate (2 of 26) with FB C-SENSE.

CONCLUSIONS

Image quality and ventricular volumetric and functional indices using either BH or FB C-SENSE cine bSSFP imaging were comparable to standard BH SENSE cine bSSFP imaging while maintaining nominally identical spatio-temporal resolution. This accelerated image acquisition provides an alternative to accommodate patients with impaired BH capacity.

Myocardial Stress Perfusion MRI Using Regadenoson: A Weight-based Approach in Infants and Young Children

Purpose

To determine the safety and feasibility of stress cardiac MRI by using weight-based dosing of regadenoson in patients less than 40 kg and whether stress cardiac MRI affects patient management.

Materials and Methods

All patients less than 40 kg undergoing stress cardiac MRI by using weight-based dosing (8 μg/kg) of regadenoson were included in this retrospective single-center study. Hemodynamic response, adverse events, and cardiac MRI abnormalities in myocardial perfusion, wall motion, and delayed enhancement were evaluated. Patient management based on the results of the stress cardiac MRI were evaluated.

Results

Forty-six consecutive stress cardiac MRI examinations were performed in 36 patients (median age, 9.0 years; age range, 2 months to 13.9 years) with congenital and acquired heart disease. Thirty-one of 46 (67.4%) studies were performed with the use of sedation. A myocardial perfusion defect was present in 20 of 46 (43.5%) studies, five with inducible defects only, and the remaining 15 with fixed or irreversible defects. In the 46 total studies, there were no major adverse events and nine (19.6%) minor adverse events including emesis (n = 1) and transient hypotension requiring pharmacologic intervention in eight patients who were all sedated. Sedation was an independent predictor for hypotension (P =.040). Twenty-six negative studies had no coronary interventions performed, and of the 20 positive studies, 15 were referred for catheterization, eight of which underwent coronary interventions.

Conclusion

Weight-based dosing of regadenoson for stress cardiac MRI was safe and feasible in infants and young children and played an integral role in the outcome and treatment decisions for children with coronary artery disease.© RSNA, 2019.

Regadenoson Stress Perfusion Cardiac Magnetic Resonance Imaging in Children With Kawasaki Disease and Coronary Artery Disease

Coronary artery (CA) stenosis and occlusion in convalescent Kawasaki disease (KD) is progressive and may result in myocardial infarction. The use of regadenoson, a strong selective CA vasodilator with low side effect profile, for stress cardiac magnetic resonance (CMR) imaging has not been studied in children with KD. The safety, feasibility, and diagnostic utility of regadenoson stress CMR was assessed in children with KD and CA abnormalities. A retrospective review of regadenoson stress CMR in children with convalescent KD was performed. Hemodynamics changes after regadenoson administration and adverse effects were recorded. First-pass perfusion was evaluated at rest and during pharmacologic stress. The results were compared with anatomic CA imaging. Forty-one stress CMR (18 sedated examinations, 44%) were performed successfully in 32 patients. Median age was 11.2 years (range 2.2 to 18.6) and weight 41 kg (range 13 to 93.4). Heart rate increased 66 ± 25% (p <0.005) after regadenoson. Minor adverse events occurred in 6 sedated and 1 unsedated patients. Hypoperfusion during stress occurred in 16 of 41 (39%), including 5 inducible, 9 inducible and fixed, and 2 fixed lesions. Late gadolinium enhancement was present in 10 of 16 with hypoperfusion and in 1 without hypoperfusion. Stress CMR had 100% positive agreement and >90% negative and overall agreement with moderate-to-severe CA stenoses. Four patients with hypoperfusion underwent revascularization for severe CA stenoses. In conclusion, regadenoson stress CMR is hemodynamically safe and feasible in children with KD and CA disease. It has excellent agreement with CA angiography and aided decision-making to proceed with revascularization.

Free-breathing Cardiorespiratory Synchronized Cine MRI for Assessment of Left and Right Ventricular Volume and Function in Sedated Children and Adolescents with Impaired Breath-holding Capacity

PURPOSE

To prospectively compare left ventricular and right ventricular volume, function, and image quality of a free-breathing (FB) cardiorespiratory synchronized balanced steady-state free precession cine MRI sequence with that of a standard of reference breath-hold (BH) technique in sedated children and adolescents who are unable to perform BHs.

MATERIALS AND METHODS

Cohort 1 included 30 patients able to perform BHs (mean age, 19 years; age range, 9-69 years). Cohort 1 underwent both BH and FB cine short-axis imaging with identical acquisition parameters. Cohort 2 included 63 patients unable to perform BHs (50 sedated patients [mean age, 9 years; age range, 4 months to 28 years], 13 unsedated patients [mean age, 21 years; age range, 8-58 years]). Cohort 2 underwent FB cine imaging in multiple views with spatiotemporal resolution equivalent to BH imaging. Comparative quantitative analysis was performed for left ventricular and right ventricular volumes in cohort 1 and for qualitative image quality scores in all patients.

RESULTS

Global left ventricular and right ventricular volumetric indexes and image quality scores were comparable between BH and FB sequences in cohort 1. FB image quality was graded as excellent (37 sequences), good (197 sequences), adequate (26 sequences), and suboptimal (three sequences) for 263 cine sequences in cohort 2. In cohort 1, de facto image acquisition time for FB (6.1 minutes ± 1.9 [standard deviation]) was comparable to the equivalent for BH (6.1 minutes ± 2.6) for a stack of 14 sections.

CONCLUSION

In cohorts of sedated children, adolescents, and young adults unable to perform BHs consistently, left ventricular and right ventricular volumes and function were comparable and image quality was noninferior between FB and standard of reference BH techniques.© RSNA, 2019.

Platform for Automated Real-Time High Performance Analytics on Medical Image Data

Biomedical data are quickly growing in volume and in variety, providing clinicians an opportunity for better clinical decision support. Here, we demonstrate a robust platform that uses software automation and high performance computing (HPC) resources to achieve real-time analytics of clinical data, specifically magnetic resonance imaging (MRI) data. We used the Agave application programming interface to facilitate communication, data transfer, and job control between an MRI scanner and an off-site HPC resource. In this use case, Agave executed the graphical pipeline tool GRAphical Pipeline Environment (GRAPE) to perform automated, real-time, quantitative analysis of MRI scans. Same-session image processing will open the door for adaptive scanning and real-time quality control, potentially accelerating the discovery of pathologies and minimizing patient callbacks. We envision this platform can be adapted to other medical instruments, HPC resources, and analytics tools.

Interleaved susceptibility-weighted and FLAIR MRI for imaging lesion-penetrating veins in multiple sclerosis

Purpose

To simultaneously image brain lesions and veins in multiple sclerosis.

Methods

An interleaved sequence was developed to simultaneously acquire 3D T2*-weighted (or susceptibility-weighted, SW) and fluid-attenuated inversion recovery (FLAIR) images on a 3.0T MRI system. The pulse sequence parameters were calculated to minimize signal perturbation from steady state while maintaining acceptable image contrast and scan time. Fifteen multiple sclerosis patients were enrolled in this prospective study and underwent a standard MS imaging protocol. In addition, SW and FLAIR images were acquired separately and also in an interleaved manner. The SW and FLAIR images were combined into one image to visualize lesions and penetrating veins. The contrast ratios between white matter lesions and penetrating veins were compared between the interleaved sequence and the individual non-interleaved acquisitions.

Results

Interleaved scanning of the FLAIR and the SW pulse sequences was achieved, producing aligned images, and with similar image contrast as in the non-interleaved images. A total of 1076 lesions were identified in all patients on the combined SW-FLAIR image, of which 968 lesions (90%) had visible penetrating veins. Lesion-to-vein contrast ratio was 32.7 ± 17.9 (mean ± standard deviation) for the interleaved sequence compared to 28.1 ± 13.7 using the separate acquisitions (P<0.001).

Conclusion

The feasibility of interleaved acquisition of susceptibility-weighted and FLAIR images was demonstrated. This sequence provides self-registered images and facilitates the visualization of veins in brain lesions.

Two-center clinical validation and quantitative assessment of respiratory triggered retrospectively cardiac gated balanced-SSFP cine cardiovascular magnetic resonance imaging in adults

BACKGROUND

Breath-hold (BH) requirement remains the limiting factor on the spatio-temporal resolution and coverage of the cine balanced steady-state free precession (bSSFP) cardiovascular magnetic resonance (CMR) imaging. In this prospective two-center clinical trial, we validated the performance of a respiratory triggered (RT) bSSFP cine sequence for evaluation of biventricular function.

METHODS

Our study included 23 asymptomatic healthy subjects and 60 consecutive patients from Institute A (n = 39) and Institute B (n = 21) referred for a clinically indicated CMR study. We implemented a RT sequence with a respiratory synchronized drive to steady state (SS) of bSSFP signal, before the commencement of image data acquisition with prospective cardiac arrhythmia rejection and retrospectively cardiac gated reconstruction in real-time. Left (LV) and right (RV) ventricular function and LV mass were evaluated by using RT-bSSFP and conventional BH-bSSFP sequences with one cardiac cycle for SS preparation keeping all the imaging parameters identical. The performance of the sequences was evaluated by using quantitative and semi-quantitative metrics.

RESULTS

Global LV and RV functional parameters and LV mass obtained from the RT-bSSFP and BH-bSSFP sequences were in good agreement. Quantitative metrics designed to capture fluctuation in SS signal intensity showed no significant difference between sequences. In addition, blood-to-myocardial contrast was nearly identical between sequences. The combined clinical score for image quality was excellent or good for 100% of cases with the BH-bSSFP and 83% of cases with the RT-bSSFP sequence. The de facto image acquisition time for RT-bSSFP was statistically significantly longer than that for conventional BH-bSSFP (7.9 ± 3.4 min vs. 5.1 ± 2.6 min).

CONCLUSIONS

Cine RT-bSSFP is an alternative for evaluating global biventricular function with contrast and spatio-temporal resolutions that are similar to those attained by using the BH-bSSFP sequence, albeit with a modest time penalty and a small reduction in image quality.

Patient-specific 3D FLAIR for enhanced visualization of brain white matter lesions in multiple sclerosis

PURPOSE

To improve the conspicuity of white matter lesions (WMLs) in multiple sclerosis (MS) using patient-specific optimization of single-slab 3D fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Sixteen MS patients were enrolled in a prospective 3.0T MRI study. FLAIR inversion time and echo time were automatically optimized for each patient during the same scan session based on measurements of the relative proton density and relaxation times of the brain tissues. The optimization criterion was to maximize the contrast between gray matter (GM) and white matter (WM), while suppressing cerebrospinal fluid. This criterion also helps increase the contrast between WMLs and WM. The performance of the patient-specific 3D FLAIR protocol relative to the fixed-parameter protocol was assessed both qualitatively and quantitatively.

RESULTS

Patient-specific optimization achieved a statistically significant 41% increase in the GM-WM contrast ratio (P < 0.05) and 32% increase in the WML-WM contrast ratio (P < 0.01) compared with fixed-parameter FLAIR. The increase in WML-WM contrast ratio correlated strongly with echo time (P < 10^-11 ). Two experienced neuroradiologists indicated substantially higher lesion conspicuity on the patient-specific FLAIR images over conventional FLAIR in 3-4 cases (intrarater correlation coefficient ICC = 0.72). In no case was the image quality of patient-specific FLAIR considered inferior to conventional FLAIR by any of the raters (ICC = 0.32).

CONCLUSION

Changes in proton density and relaxation times render fixed-parameter FLAIR suboptimal in terms of lesion contrast. Patient-specific optimization of 3D FLAIR increases lesion conspicuity without scan time penalty, and has potential to enhance the detection of subtle and small lesions in MS.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:557-564.

Automated patient-specific optimization of three-dimensional double-inversion recovery magnetic resonance imaging

PURPOSE

To automatically optimize three-dimensional double-inversion recovery (3D-DIR) MRI of the brain on a patient-by-patient basis.

METHODS

DIR is a powerful MRI technique that allows simultaneous suppression of white matter (WM) and cerebrospinal fluid (CSF) in brain imaging. Unfortunately, the tissue suppression is not always consistent across patients. We propose patient-specific optimization of WM suppression for improved gray matter (GM)-WM contrast. Relaxation times were measured in the same scan session, and through real time processing were used for calculating DIR inversion times for maximum tissue contrast. Signal evolution during the variable-flip-angle turbo-spin-echo readout was calculated using the extended phase graph algorithm. Patient-specific optimization was examined in five healthy volunteers and two multiple sclerosis patients. Two volunteers were scanned twice for reproducibility. The contrast ratios, GM signal-to-noise ratio (SNR), and image histogram were used to assess the performance of this patient-specific approach.

RESULTS

Automated optimization of 3D-DIR was successfully completed in all experiments with processing time of ∼1 min. GM-WM contrast ratio tripled with the optimized DIR sequence, with only a 19% decrease in GM-CSF contrast and 30% SNR penalty.

CONCLUSION

Patient-specific optimization is feasible and significantly improves GM-WM contrast on 3D-DIR with a moderate decrease in the GM SNR.

Automatic computation of left ventricular ejection fraction from spatiotemporal information in cine-SSFP cardiac MR images

PURPOSE

To clinically validate an algorithm that automatically computes left ventricular (LV) ejection fraction (LVEF) using a priori geometric and intrinsic spatiotemporal information from cine steady-state free precession (SSFP) MR images.

MATERIALS AND METHODS

The algorithm was evaluated in 64 subjects (21 healthy volunteers and 43 patients, LVEF 19-71%). Bland-Altman analyses were performed on short-axis slices subdivided into three sections (basal, midcavity, and apical) to assess the impact of morphologic variations on LVEF computation.

RESULTS

The automated algorithm delineated the clinically applicable endocardial boundary in 1011 of 1078 short-axis slices (94%). The bias (mean difference) values computed with clinically unusable contours replaced with hand-drawn equivalents were small for the LV end-diastolic volume (LVEDV, <11 mL/7%), end-systolic volume (LVESV, <7 mL/11%), and LVEF (<1.2%). Moreover, these values were within the limits of interobserver and intraobserver variability of experienced observers (LVEDV, <13 mL/8%; LVESV, <12 mL/17%; and LVEF, <5%). In the end-diastolic phase, the limits of agreement (bias +/- 1.96 SD of difference) were small (<5% LVEDV) in all sections. However, in the end-systolic phase, the limits of agreement were larger for the midcavity (<21% LVESV) and apical (<11% LVESV) slices.

CONCLUSION

This data-driven algorithm can estimate LVEDV, LVESV, and LVEF with a bias that is comparable to the interobserver and intraobserver variability of experienced observers.

Image segmentation based on fuzzy connectedness using dynamic weights

Traditional segmentation techniques do not quite meet the challenges posed by inherently fuzzy medical images. Image segmentation based on fuzzy connectedness addresses this problem by attempting to capture both closeness, based on characteristic intensity, and "hanging togetherness," based on intensity homogeneity, of image elements to the target object. This paper presents a modification and extension of previously published image segmentation algorithms based on fuzzy connectedness, which is computed as a linear combination of an object-feature-based and a homogeneity-based component using fixed weights. We provide a method, called fuzzy connectedness using dynamic weights (DyW), to introduce directional sensitivity to the homogeneity-based component and to dynamically adjust the linear weights in the functional form of fuzzy connectedness. Dynamic computation of the weights relieves the user of the exhaustive search process to find the best combination of weights suited to a particular application. This is critical in applications such as analysis of cardiac cine magnetic resonance (MR) images, where the optimal combination of affinity component weights can vary for each slice, each phase, and each subject, in spite of data being acquired from the same MR scanner with identical protocols. We present selected results of applying DyW to segment phantom images and actual MR, computed tomography, and infrared data. The accuracy of DyW is assessed by comparing it to two different formulations of fuzzy connectedness. Our method consistently achieves accuracy of more than 99.15% for a range of image complexities: contrast 5%-65%, noise-to-contrast ratio of 6%-18%, and bias field of four types with maximum gain factor of up to 10%.

Automatic identification of the left ventricle in cardiac cine-MR images: Dual-contrast cluster analysis and scout-geometry approaches

PURPOSE

To evaluate the technical feasibility of two approaches--dual-contrast (DC) cluster analysis, and scout geometry (SG)--for automatic identification of the left ventricular (LV) cavity in short-axis (SA) cine-MR images.

MATERIALS AND METHODS

The DC algorithm uses Fuzzy C-Means (FCM) cluster analysis of SA images from a black-blood double-inversion recovery turbo spin-echo (dual IR TSE) sequence, and bright-blood images from a steady-state free precession (SSFP) sequence. The SG algorithm employs geometric information from scout views (i.e., vertical long-axis (VLA) and four-chamber (4CH) views). Both algorithms incorporate additional geometric continuity constraints along with LV region segmentation to identify the LV. The performance of both algorithms was compared on images of eight healthy volunteers, and the SG algorithm was further evaluated on images of 13 clinical patients.

RESULTS

The DC algorithm identified the LV in 89% (72/75 at end-diastole (ED) and 47/59 at end-systole (ES)) of the images from healthy volunteers, compared to 98% (74/75 at ED and 57/59 at ES) by the SG algorithm. Both methods are robust against interslice signal variations and misalignment. The DC method suffers from misregistration between the dual IR TSE and SSFP images near the apex at ES. The SG method identified the LV in 91% (112/122 at ED and 91/102 at ES) of the images from clinical patients.

CONCLUSION

The SG method requires no additional scan, is robust and accurate, and performs better than the DC method for automatic identification of the LV.