Short-axis Orientation Research Articles

The role of cardiac magnetic resonance in patients with an angiographically diagnosed SCAD

Abstract Background/Introduction Spontaneous coronary artery dissection (SCAD) characterized by its non-atherosclerotic nature, poses challenges in diagnosis and management. While recent efforts shed light on SCAD's clinical aspects, the specific utility of CMR demands deeper investigation for enhanced diagnosis and patient care. Purpose This study aims to analyze the characteristics of patients with an angiographically diagnosed SCAD, evaluate qualitative and quantitative parameters of baseline CMR and investigate predictors of myocardial injury and the association between CMR parameters and clinical outcome (major adverse cardiac events, MACE). Methods The study is a prospective single-center analysis of 59 patients, presented acutely in our hospital, from March 2018 to November 2023, with an angiographically detected SCAD. CMR was performed after a median of 4 days (IQR 1.5-7) from the acute onset of symptoms. SCAD Types were angiographically categorized according to the Yip-Saw classification. Most patients (71%) were screened for fibromuscular dysplasia (FMD) with a brain MR and at least one contrast-enhanced abdominal vessels investigation (CT or MR). CMR imaging was performed on a clinical 1.5 T Scanner. T1-weighted, T2-weighted turbo-spin-echo (TSE) Black-Blood (BB) and Short-Tau-Inversion-Recovery (STIR) sequences in short-axis orientation were acquired. The scan protocol included standard cine and T1/T2-weighted TSE BB and Mapping sequences. Late gadolinium enhanced (LGE) images were acquired ≏10 min after the contrast injection and were visually assessed for the presence and extension of LGE areas. LGE quantification was assessed semiautomatically. Results 40 (68%) were females. 54(92%) complained of chest pain, in 55 (93%) high-sensitive Troponin T was eleveted (>14 ng/l) and 24 (41%) presented with the clinical picture of STEMI on admission. From an angiographic point of view, the majority (69.5%) were classified as SCAD Type 2 (a+b). Among patients who underwent a proper screening, 7 patients (16%) were diagnosed with FMD. Baseline CMR showed signs of active injury in 81% and LGE in 93% of the population; however, it was often moderate in size (median of LGE segments 3, IQR 2-5). Most patients had a preserved LVEF (55±10%). STEMI presentation is an independent predictor of LGE extension (p=0.02, OddsRatio(95% CI)=7(2-24)). ScadType1 (p=0.01, OR=10( 2-39)) and N°LGE transmural segments >3 (p=0.03, OR=5.4(1.2-25)) were found to be significant predictor of MACE. 6 of the 11 MACEs were SCAD recurrence/progression, and 4 out of these 11 had already shown signs of previous myocardial injury in the baseline CMR. Conclusion(s) This study emphasized the significance of CMR, which may provide further insights into extend of myocardial damage and may aid in patients’ risk stratification.

Segmentation-Free Estimation of Left Ventricular Ejection Fraction Using 3D CNN Is Reliable and Improves as Multiple Cardiac MRI Cine Orientations Are Combined.

We aimed to study classical, publicly available convolutional neural networks (3D-CNNs) using a combination of several cine-MR orientation planes for the estimation of left ventricular ejection fraction (LVEF) without contour tracing. Cine-MR examinations carried out on 1082 patients from our institution were analysed by comparing the LVEF provided by the CVI42 software (V5.9.3) with the estimation resulting from different 3D-CNN models and various combinations of long- and short-axis orientation planes. The 3D-Resnet18 architecture appeared to be the most favourable, and the results gradually and significantly improved as several long-axis and short-axis planes were combined. Simply pasting multiple orientation views into composite frames increased performance. Optimal results were obtained by pasting two long-axis views and six short-axis views. The best configuration provided an R2 = 0.83, a mean absolute error (MAE) = 4.97, and a root mean square error (RMSE) = 6.29; the area under the ROC curve (AUC) for the classification of LVEF < 40% was 0.99, and for the classification of LVEF > 60%, the AUC was 0.97. Internal validation performed on 149 additional patients after model training provided very similar results (MAE 4.98). External validation carried out on 62 patients from another institution showed an MAE of 6.59. Our results in this area are among the most promising obtained to date using CNNs with cardiac magnetic resonance. (1) The use of traditional 3D-CNNs and a combination of multiple orientation planes is capable of estimating LVEF from cine-MRI data without segmenting ventricular contours, with a reliability similar to that of traditional methods. (2) Performance significantly improves as the number of orientation planes increases, providing a more complete view of the left ventricle.

Development and performance evaluation of fully automated deep learning-based models for myocardial segmentation on T1 mapping MRI data

To develop a deep learning-based model capable of segmenting the left ventricular (LV) myocardium on native T1 maps from cardiac MRI in both long-axis and short-axis orientations. Models were trained on native myocardial T1 maps from 50 healthy volunteers and 75 patients using manual segmentation as the reference standard. Based on a U-Net architecture, we systematically optimized the model design using two different training metrics (Sørensen-Dice coefficient = DSC and Intersection-over-Union = IOU), two different activation functions (ReLU and LeakyReLU) and various numbers of training epochs. Training with DSC metric and a ReLU activation function over 35 epochs achieved the highest overall performance (mean error in T1 10.6 ± 17.9 ms, mean DSC 0.88 ± 0.07). Limits of agreement between model results and ground truth were from -35.5 to + 36.1 ms. This was superior to the agreement between two human raters (-34.7 to + 59.1 ms). Segmentation was as accurate for long-axis views (mean error T1: 6.77 ± 8.3 ms, mean DSC: 0.89 ± 0.03) as for short-axis images (mean error ΔT1: 11.6 ± 19.7 ms, mean DSC: 0.88 ± 0.08). Fully automated segmentation and quantitative analysis of native myocardial T1 maps is possible in both long-axis and short-axis orientations with very high accuracy.

Quantitative assessment of carotid ultrasound diameter measurements in the operating room: a comparable analysis of long-axis versus rotated and tilted orientation

Objective. Carotid ultrasound (US) has been studied as a non-invasive alternative for hemodynamic monitoring. A long-axis (LA) view is traditionally employed but is difficult to maintain and operator experience may impact the diameter estimates, making it unsuitable for monitoring. Preliminary results show that a new, i.e. rotated and tilted (RT) view is more robust to motion and less operator-dependent. This study aimed to quantitatively assess common carotid diameter estimates obtained in a clinical setting from an RT view and compare those to corresponding estimates obtained using other views. Approach. Carotid US measurements were performed in 30 adult cardiac-surgery patients (26 males, 4 females) with short-axis (SA), LA, and RT probe orientations, the first being used as a reference for measuring the true vessel diameter. Per 30 s acquisition, the median and spread in diameter values were computed, the latter representing a measure of robustness, and were statistically compared between views. Main results. The median (IQR) over all the patients of the median diameter per 30 s acquisition was 7.15 (1.15) mm for the SA view, 7.03 (1.51) mm for the LA view, and 6.99 (1.72) mm for the RT view. The median spread in diameter values was 0.18 mm for the SA view, 0.16 mm for the LA view, and 0.18 mm for the RT view. There were no statistically significant differences between views in the median diameter values (p = 0.088) or spread (p = 0.122). Significance. The RT view results in comparable and equally robust median carotid diameter values compared to the reference. These findings open the path for future studies investigating the use of the RT view in new applications, such as in wearable ultrasound devices.

Effect of Data Augmentation on Deep-Learning-Based Segmentation of Long-Axis Cine-MRI

Automated Cardiac Magnetic Resonance segmentation serves as a crucial tool for the evaluation of cardiac function, facilitating faster clinical assessments that prove advantageous for both practitioners and patients alike. Recent studies have predominantly concentrated on delineating structures on short-axis orientation, placing less emphasis on long-axis representations due to the intricate nature of structures in the latter. Taking these consideration into account, we present a robust hierarchy-based augmentation strategy coupled with the compact and fast Efficient-Net (ENet) architecture for the automated segmentation of two-chamber and four-chamber Cine-MRI images. We observed an average Dice improvement of 0.99% on the two-chamber images and of 2.15% on the four-chamber images, and an average Hausdorff distance improvement of 21.3% on the two-chamber images and of 29.6% on the four-chamber images. The practical viability of our approach was validated by computing clinical metrics such as the Left Ventricular Ejection Fraction (LVEF) and left ventricular volume (LVC). We observed acceptable biases, with a +2.81% deviation on the LVEF for the two-chamber images and a +0.11% deviation for the four-chamber images.

Impact of the evaluation method on 4D flow-derived diastolic transmitral and myocardial peak velocities: Comparison with echocardiography

PurposeTo compare agreement of different evaluation methods of magnetic resonance (MR) 4D flow-derived diastolic transmitral and myocardial peak velocities as well as their ratios, using echocardiography as reference. MethodsIn this prospective study, 60 subjects without symptoms of cardiovascular disease underwent echocardiography and non-contrast 3 T MR 4D flow imaging of the heart. Early- (E) and late-diastolic (A) transmitral peak filling velocities were evaluated from 4D flow data using three different strategies: 1) at the mitral valve tips in short-axis orientation (SA-method), 2) between the mitral valve tips in 4-chamber orientation (4-chamber-method), and 3) as maximal velocities in the transmitral inflow volume (max-velocity-method). Septal, lateral and average early-diastolic myocardial peak velocities (e’) were derived from the myocardial tissue in the vicinity of the mitral valve. 4D flow parameters were compared with echocardiography by correlation and Bland-Altman analysis. ResultsAll 4D flow-derived E, A and E/A values correlated with echocardiography (r = 0.65–0.73, 0.75–0.83 and 0.74–0.86, respectively). While the SA- and 4-chamber-methods substantially underestimated E and A compared to echocardiography (p < 0.001), the max-velocity-method provided E (p = 0.13) and E/A (p = 0.07) without significant bias. Septal, lateral and average e’ from 4D flow as well as the max-velocity-method-derived E/e’ correlated with echocardiographic measurements (r = 0.64–0.81) and showed no significant bias (p = 0.26–0.54). ConclusionMR 4D flow imaging allows precise and accurate evaluation of transmitral and myocardial peak velocities for characterization of LV diastolic function without significant bias to echocardiography, when transmitral velocities are assessed from the transmitral inflow volume. This enables the use of validated echocardiography threshold values.

Abstract 16590: Left Ventricular Remodelling Following Transcatheter Mitral Valve Replacement With the Innovalve System

Introduction: Transcatheter Mitral Valve Replacement (TMVR) using a trans-septal approach is a new therapeutic option for patients with severe mitral regurgitation (MR). However, both surgical as well as currently under-testing trans-catheter approach, are shown to cause decrease in LV function. The Innovalve TMVR is a novel self-expandable transcatheter mitral valve prosthesis, delivered trans-septally using femoral venous access. It is deployed in an intravalvular posterior position after subvalvular anchoring by rotation of 6 circumferential arms Hypothesis: TMVR procedure (Innovalve system) leads to LV anatomical and functional changes Methods: CT was performed before the Innovalve TMVR procedure, and after 3 to 6 months. CT protocol included retrospective ECG gating with full cardiac cycle coverage. LV end diastolic and end systolic diameters (LVEDD, LVESD) were measured in the left ventricular outflow tract orientation at the most basal level. Tip to tip papillary muscle distance was measured in the short axis orientation at the most basal slice demonstrating the papillary muscle tips. LV ejection fraction (LVEF) was calculated using the end systolic and end diastolic volumes. All measurements were performed at end systole and end diastole before MTVR and after 3-6 months using a dedicated platform (3Mensio). Results: Ten patients (7 males) average age 69+/-10 years, underwent the Innovalve TMVR procedure. Average LVESD decreased from 52±15 mm at baseline to 44±15mm (P=0.016) at 3-6 months. Similarly, LVEDD decreased from 60±14 mm at baseline, to 52±13mm at 3-6 months (P=0.039). Average papillary muscle tip to tip distance at end diastole (ED) decreased from 31.7±7mm at baseline to 28.4±6.5mm at 3-6 months (P=0.047).A trend of LVEF improvement was evident with an increase from 35%±12 average at baseline compared with 39%±12 average after 3-6 months (P=0.346). Conclusions: These preliminary results show that the TMVR procedure using the Innovalve system may result in favourable LV reverse remodelling changes including reduction of LVESD, LVEDD and ED papillary muscle distances, with improved LVEF. This encouraging data might suggest favourable postprocedural structural LV change.

Normal values for native T1 at 1.5 T in the pericardial fluid of healthy volunteers.

T1 mapping cardiovascular magnetic resonance (CMR) imaging has been used to characterize pericardial effusions. The aim of this study was to measure pericardial fluid native T1 values in healthy volunteers to establish normal values. Prospectively recruited volunteers (n = 30) underwent CMR at 1.5 T, and native T1 maps were acquired using a modified look-locker inversion recovery 5s(3s)3s acquisition scheme. A volume of pericardial fluid was imaged in a short-axis slice and in a slice perpendicular to the short-axis orientation. A reliable measurement had a region of interest (ROI) size > 10 mm2, coefficient of variation < 10%, and a relative difference < 5% between the two slice orientations. In 26/30 (87%) of volunteers, there was a sufficient amount of pericardial fluid to enable reliable measurement. Native T1 of pericardial fluid was 3262 ± 163 (95% normal limits 2943-3581 ms) and did not differ in the perpendicular slice orientation (3267 ± 173 ms, P = 0.75), due to sex (female 3311 ± 177 vs. male 3220 ± 142 ms, P = 0.17), age (R 2 = 0.03, P = 0.44), heart rate (R 2 = 0.005, P = 0.7), or size of the ROI (0.06, P = 0.23). This study shows that T1 values can be reliably measured in the pericardial fluid of healthy volunteers. It is the first to report normal reference ranges for T1 values at 1.5 T in the pericardial fluid of healthy volunteers.

Diagnostic quality and clinical utility of cardiovascular magnetic resonance in patients with subcutaneous ICDs

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiovascular magnetic resonance (CMR) is increasingly requested in patients with cardiac implantable electronic devices (CIEDs) – particularly for scar identification in patients with ventricular arrhythmias and implantable cardiac defibrillators (ICDs). Image artefact can be challenging in patients with larger devices, and patients with subcutaneous ICDs (S-ICDs) may not be referred due to concerns about non-diagnostic imaging. Modified sequences including wide band MOCO with PSIR (WB-MOCO) have been used to reduce image artefact in patients with CIEDs. We evaluated the image quality and clinical impact of gradient echo cine imaging and LGE CMR imaging in patients with S-ICDs. Methods Twenty CMR scans were performed adhering to manufacturer conditions in 19 patients (mean age 42± 13 years, 68% male) with MR conditional S-ICDs over four years.All patients were scanned at 1.5T at a single UK tertiary centre, with sequence modification using a pre-defined sequence protocol including gradient echo cine imaging, and WB-MOCO where conventional LGE showed artefact. LGE images were reviewed and graded for artefact by two independent observers, both by AHA segment and for overall quality on a scale of 0–4 (Grade 0 = no artefact, Grade 2 = 2–3 segments obscured by artefact, Grade 4 = entire myocardium obscured). Segments were viewed in both long and short axis orientations and deemed diagnostic if visible in at least one orientation. Clinical utility was assessed using pre-defined criteria, based on review of electronic medical records. Ethical approval was obtained from the Health Research Authority(REC21/EE/0037). Results CMR scans were performed in all patients without complication, excepting loss of ICD beeper function in 3 (16%) of patients (manufacturer recognised complication). S-ICDs were implanted for secondary prevention in 50% of cases with 63% patients having non-ischaemic cardiomyopathies. Scan indications included assessment of aetiology of heart failure (25%), ischaemic heart disease (20%), suspected left ventricular thrombus (20%), myocarditis (20%), scar assessment for viability (5%) miscellaneous (10%). Volumetric analysis from cine imaging was possible in 80%. LGE was present in 19 (95%) scans. Conventional LGE was only successful in 10% (2; 1 grade 0, 1 grade 1). Where WB-MOCO was used (n=18) this improved to 83% (grade 0 in 72%, grade 1 in 11%) with 95%being diagnostic (just 5% grade 3, 0% grade 4). Artefact was most commonly seen in the mid inferolateral segment (33% scans). Where follow-up data was available (19/20 scans), CMR led to a new diagnosis in 2 (10%) of scans and changes in management in 10 (53%) of scans. Conclusion Scar imaging using CMR can be safely performed in patients with S-ICDs, with diagnostic LGE imaging feasible in the majority (95% scans grades 0–2) and diagnostic cine imaging (in 80%) with the results providing high clinical yield.

The effect of continuous positive airway pressure on inferior vena cava collapsibility as measured by bedside ultrasound.

The purpose of this study was to determine the impact of progressively increasing continuous positive airway pressure (CPAP) on measurements of the caval index (CI) using bedside ultrasound at the 3 common inferior vena cava (IVC) evaluation sites. This was a prospective, observational trial that included 165 healthy adults over 18 years old enrolled between February 2015 and May 2018. Measurements of the IVC were obtained during normal tidal respirations from the subxiphoid area in the long and short axis and from the right mid-axillary line in the long axis. Measurements were obtained in each of these locations at atmospheric pressure and with CPAP at 5, 10, and 15 cmH2O. The CI was then calculated for each of the 3 selected locations at each level of pressure. As CPAP pressures increased from 0 to 15cmH2O the CI measurements obtained at the lateral mid-axillary line did not show any statistically significant variation. There was a statistically significant difference (P<0.001) when comparing measurements of the CI from the lateral mid-axillary line location to both anterior locations. As CPAP pressures increased, the CI calculated from the subxiphoid area in both the anterior short and anterior long axis orientations initially trended upwards at 5cmH2O, then began to downtrend as the pressures increased to 10 and 15cmH2O. Comparing the CI measurements from the anterior long and anterior short axis at 0, 5, 10, and 15cmH2O, there was no statistically significant difference at any pressure (P>0.05). When evaluating the IVC in a spontaneously breathing patient, measurements from an anterior orientation are preferred as the lateral mid-axillary view can underestimate CI calculations.

Cardiac magnetic resonance imaging derived reference values for ventricular anatomy and function and myocardial tissue characterization in adolescents: the EnIGMA study

Abstract Introduction Cardiac magnetic resonance (CMR) imaging is a precise tool for the assessment of cardiac anatomy and function. However, studies providing reference values for CMR parameters, including myocardial tissue properties, in healthy adolescents are scarce. Purpose To provide CMR derived reference values for biventricular mass, volumes and function measured by cine steady-state free-precession (SSFP) sequences and myocardial tissue relaxation properties as measured by native T1- and T2-mapping sequences in healthy adolescents. Methods A comprehensive non-contrast CMR study was performed in healthy adolescents aged 15 to 18 years enrolled in the “Early ImaginG Markers of unhealthy lifestyles in Adolescents” (EnIGMA) project using a 3-Tesla CMR scanner between March 2021 and October 2021. The imaging protocol included a cine SSFP to provide high-quality images for chamber size and function analysis, and a T2-GraSE mapping and native T1-mapping sequences (MOLLI Scheme 5 (3) 3) to provide precise myocardial relaxation time properties. Images were analyzed by experienced observers using the Cardiac Analysis tool available at IntelliSpace Portal following a standard protocol. In cine SSFP sequences, right and left ventricles were manually contoured for end-diastolic and end-systolic phases in the short-axis orientation, respectively (Figure 1A, B). Native T1 and T2 maps were analyzed in a mid-ventricular short axis slice and summarized values per individual were determined (Figure 1C, D). Student's t-tests were used for between-gender comparisons. Results CMR scans were performed in 123 adolescents (63 girls, 51.2%) with a mean age of 16.0 years (standard deviation (SD)=0.5), mean body mass index of 21.4 (SD=3.2) kg/m2, mean body surface area of 1.69 (SD=0.16) m2, and mean heart rate during CMR acquisitions of 69 (SD=11) beats/minute. Reference percentiles (P) 3, 10, 25, 50, 75, 90 and 97 for the different parameters analyzed by gender are provided in Figure 2. Mean left and right ventricular end-diastolic indexed volumes were higher in boys than in girls (91.5 vs 78.1 ml/m2, p&amp;lt;0.01; and 101.1 vs 84.2 ml/m2, p&amp;lt;0.01), as well as the indexed cardiac mass (48.4 vs 36.4 g/m2, p&amp;lt;0.01). Left ventricular ejection fraction (LVEF) was similar in boys and girls (62.0 vs. 62.9%, p=0.23), whereas right ventricular ejection fraction was slightly lower in boys than in girls (55.3 vs. 57.1%, p=0.03). Mean myocardial native T1 relaxation time was 1253 (SD=28) ms in girls and 1215 (SD=23) ms in boys (p&amp;lt;0.01), whereas mean myocardial T2 relaxation time was 44.1 (SD=2.3) ms and 44.4 (SD=2.0) ms in girls and boys, respectively (p=0.46). Conclusion This study provided CMR derived reference values for biventricular anatomy, function, and myocardial tissue properties, in healthy adolescents aged 15 to 18 years. This information may be useful for the differential diagnosis of cardiac diseases, such as cardiomyopathies and myocarditis, in adolescent population. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Instituto de Salud Carlos III (ISCIII)-Fondo de Investigaciόn SanitariaEuropean Regional Development Fund/European Social Fund (“A way to make Europe”/“Investing in your future”)

COMPARISON OF POST-PROCESSING TECHNIQUES FOR OPTIMIZING THE QUALITY OF CARDIAC MAGNETIC RESONANCE T1 MAPPING IMAGES

COMPARISON OF POST-PROCESSING TECHNIQUES FOR OPTIMIZING THE QUALITY OF CARDIAC MAGNETIC RESONANCE T1 MAPPING IMAGES

Right ventricular strain and volume analyses through deep learning-based fully automatic segmentation based on radial long-axis reconstruction of short-axis cine magnetic resonance images.

We propose a deep learning-based fully automatic right ventricle (RV) segmentation technique that targets radially reconstructed long-axis (RLA) images of the center of the RV region in routine short axis (SA) cardiovascular magnetic resonance (CMR) images. Accordingly, the purpose of this study is to compare the accuracy of deep learning-based fully automatic segmentation of RLA images with the accuracy of conventional deep learning-based segmentation in SA orientation in terms of the measurements of RV strain parameters. We compared the accuracies of the above-mentioned methods in RV segmentations and in measuring RV strain parameters by Dice similarity coefficients (DSCs) and correlation coefficients. DSC of RV segmentation of the RLA method exhibited a higher value than those of the conventional SA methods (0.84 vs. 0.61). Correlation coefficient with respect to manual RV strain measurements in the fully automatic RLA were superior to those in SA measurements (0.5-0.7 vs. 0.1-0.2). Our proposed RLA realizes accurate fully automatic extraction of the entire RV region from an available CMR cine image without any additional imaging. Our findings overcome the complexity of image analysis in CMR without the limitations of the RV visualization in echocardiography.

In Vivo Super-Resolution Cardiac Diffusion Tensor MRI: A Feasibility Study.

A super-resolution (SR) technique is proposed for imaging myocardial fiber architecture with cardiac magnetic resonance. Images were acquired with a motion-compensated cardiac diffusion tensor imaging (cDTI) sequence. The heart left ventricle was covered with three stacks of thick slices, in short axis, horizontal and vertical long axes orientations, respectively. The three low-resolution stacks (2 × 2 × 8 mm3) were combined into an isotropic volume (2 × 2 × 2 mm3) by a super-resolution reconstruction. For in vivo measurements, each slice was acquired during a breath-hold period. Bulk motion was corrected by optimizing a similarity metric between intensity profiles from all intersecting slices in the dataset. The benefit of the proposed approach was evaluated using a numerical heart phantom, a physical helicoidal phantom with artificial fibers, and six healthy subjects. The SR technique showed improved results compared to the native scans, in terms of image quality and cDTI metrics. In particular, the myocardial helix angle (HA) was more accurately estimated in the physical phantom (HA = 41.5° ± 1.1°, with the ground truth being 42.0°). In vivo, it resulted in a sharper rate of change of HA across the myocardial wall (−0.993°/% ± 0.007°/% against −0.873°/% ± 0.010°/%).

The microstructure of Moso bamboo (Phyllostachys heterocycla) with tung oil thermal treatment

Summary Bamboo has a natural anisotropic porous structure. Previous studies have shown strong correlations between the properties and microstructure of bamboo. In this study, we examined the microstructure of Moso bamboo to reveal the mechanism of enhanced properties with tung oil thermal treatment. The morphological and chemical microstructure of Moso bamboo were characterized using scanning electron microscopy (SEM) and Raman spectroscopy. We found that tung oil film presented in the cell wall, cell lumen, and intercellular space after tung oil thermal treatment, which could decrease the water permeability in the cell wall. Additionally, the pits in vessels showed significant shrinkage in the short-axis orientation with thermal treatment in tung oil, and the shrinkage rate was nearly 50% with a temperature of tung oil over 140°C, which prevented the transportation of water through the pit. The content of tung oil in bamboo was reduced by more than 50% with an increase of tung oil temperature from 140°C to 200°C, which further supported the results of changed bamboo morphology. Altogether, these findings offer further support for the enhanced hydrophobic property of bamboo after tung oil thermal treatment.

A Hybrid Approach for Cardiac Blood Flow Vortex Ring Identification Based on Optical Flow and Lagrangian Averaged Vorticity Deviation.

Objective: The measurement of cardiac blood flow vortex characteristics can help to facilitate the analysis of blood flow dynamics that regulates heart function. However, the complexity of cardiac flow along with other physical limitations makes it difficult to adequately identify the dominant vortices in a heart chamber, which play a significant role in regulating the heart function. Although the existing vortex quantification methods can achieve this goal, there are still some shortcomings: such as low precision, and ignoring the center of the vortex without the description of vortex deformation processes. To address these problems, an optical flow Lagrangian averaged vorticity deviation (Optical flow-LAVD) method is proposed.Methodology: We examined the flow within the right atrium (RA) of the participants’ hearts, by using a single set of scans pertaining to a slice at two-chamber short-axis orientation. Toward adequate extraction of the vortex ring characteristics, a novel approach driven by the Lagrangian averaged vorticity deviation (LAVD) was implemented and applied to characterize the trajectory integral associated with vorticity deviation and the spatial mean of rings, by using phase-contrast magnetic resonance imaging (PC-MRI) datasets as a case study. To interpolate the time frames between every larger discrete frame and minimize the error caused by constructing a continuous velocity field for the integral process of LAVD, we implemented the optical flow as an interpolator and introduced the backward warping as an intermediate frame synthesis basis, which is then used to generate higher quality continuous velocity fields.Results: Our analytical study results showed that the proposed Optical flow-LAVD method can accurately identify vortex ring and continuous velocity fields, based on optical flow information, for yielding high reconstruction outcomes. Compared with the linear interpolation and phased-based frame interpolation methods, our proposed algorithm can generate more accurate synthesized PC-MRI.Conclusion: This study has developed a novel Optical flow-LAVD model to accurately identify cardiac vortex rings, and minimize the associated errors caused by the construction of a continuous velocity field. Our paper presents a superior vortex characteristics detection method that may potentially aid the understanding of medical experts on the dynamics of blood flow within the heart.

Effect of low wall shear stress on the morphology of endothelial cells and its evaluation indicators

ObjectiveThis study is designed to explore the morphological changes of endothelial cells (ECs) under different levels of shear stress and find the effective evaluation indicators with in vivo and in vitro experiments. MethodsHuman umbilical vein endothelial cells (HUVECs) and Sprague–Dawley rats were used to study the effect of different shear stress which applied by means of parallel plate-flow chamber and abdominal aorta banding model on the morphology of endothelial cells. Then, fluorescence images were acquired by means of a confocal laser-scanning microscope. Finally, Cell morphological indicators were extracted by SRAD-MCW computer image processing algorithm for quantitative analysis. Results1) The morphological changes of HUVECs were observed after exposure to shear stress for 6 h, the HUVECs were elongated and spindle-shaped. And the degree of cell deformability was different while the exposure time was different, then it became stable after 18 h. The HUVECs exposure to high shear stress (HSS) exhibited an ordered cell arrangement, while the HUVECs exposure to low shear stress (LSS) showed a disordered cell arrangement. 2) Traditional cell morphological indicators such as area, perimeter, long axis diameter, short axis diameter and orientation angle were not significantly different between the normal shear stress (NSS) group and the LSS group (P > 0.05), but the intercellular space characteristics such as the junction length per unit area and the triple points per unit area were significantly different (P < 0.05). ConclusionThese results demonstrate that the size and duration of shear stress can affect the morphology and arrangement of endothelial cells. The commonly used evaluation indicators for studying the effect of shear stress on the morphology of endothelial cells, including area, perimeter, long axis diameter, short axis diameter and orientation angle, etc., had no significant statistical significance, while the intercellular space characteristics including the junction length per unit area and the triple points per unit area can be used as effective indicator to study the effect of shear stress on the morphology of endothelial cells.

Joint image and field map estimation for multi-echo hyperpolarized 13 C metabolic imaging of the heart.

Image reconstruction of metabolic images from hyperpolarized 13 C multi-echo data acquisition is sensitive to susceptibility-induced phase offsets, which are particularly challenging in the heart. A model-based framework for joint estimation of metabolite images and field map from echo shift-encoded data is proposed. Using simulations, it is demonstrated that correction of signal spilling due to incorrect decomposition of metabolites and geometrical distortions over a wide range of off-resonance gradients is possible. In vivo feasibility is illustrated using hyperpolarized [1-13 C]pyruvate in the pig heart. The model-based reconstruction for multi-echo, multicoil data was implemented as a nonconvex minimization problem jointly optimizing for metabolic images and B0 . A comprehensive simulation framework for echo shift-encoded hyperpolarized [1-13 C]pyruvate imaging was developed and applied to assess reconstruction performance and distortion correction of the proposed method. In vivo data were obtained in four pigs using hyperpolarized [1-13 C]pyruvate on a clinical 3T MR system with a six-channel receiver coil. Dynamic images were acquired during suspended ventilation using cardiac-triggered multi-echo single-shot echo-planar imaging in short-axis orientation. Simulations revealed that off-resonance gradients up to ±0.26ppm/pixel can be corrected for with reduced signal spilling and geometrical distortions yielding an accuracy of ≥90% in terms of Dice similarity index. In vivo, improved geometrical consistency (10% Dice improvement) compared to image reconstruction without field map correction and with reference to anatomical data was achieved. Joint image and field map estimation allows addressing off-resonance-induced geometrical distortions and metabolite spilling in hyperpolarized 13 C metabolic imaging of the heart.

Measuring myocardial extracellular volume of the right ventricle in patients with congenital heart disease

The right ventricle´s (RV) characteristics—thin walls and trabeculation—make it challenging to evaluate extracellular volume (ECV). We aimed to assess the feasibility of RV ECV measurements in congenital heart disease (CHD), and to introduce a novel ECV analysis tool. Patients (n = 39) and healthy controls (n = 17) underwent cardiovascular magnetic resonance T1 mapping in midventricular short axis (SAX) and transverse orientation (TRANS). Regions of interest (ROIs) were evaluated with regard to image quality and maximum RV wall thickness per ROI in pixels. ECV from plane ROIs was compared with values obtained with a custom-made tool that derives the mean T1 values from a “line of interest” (LOI) centered in the RV wall. In CHD, average image quality was good (no artifacts in the RV, good contrast between blood/myocardium), and RV wall thickness was 1–2 pixels. RV ECV was not quantifiable in 4/39 patients due to insufficient contrast or wall thickness < 1 pixel. RV myocardium tended to be more clearly delineated in SAX than TRANS. ECV from ROIs and corresponding LOIs correlated strongly in both directions (SAX/TRANS: r = 0.97/0.87, p < 0.001, respectively). In conclusion, RV ECV can be assessed if image quality allows sufficient distinction between myocardium and blood, and RV wall thickness per ROI is ≥ 1 pixel. T1 maps in SAX are recommended for RV ECV analysis. LOI application simplifies RV ECV measurements.

Unsupervised Domain Adaptation From Axial to Short-Axis Multi-Slice Cardiac MR Images by Incorporating Pretrained Task Networks.

Anisotropic multi-slice Cardiac Magnetic Resonance (CMR) Images are conventionally acquired in patient-specific short-axis (SAX) orientation. In specific cardiovascular diseases that affect right ventricular (RV) morphology, acquisitions in standard axial (AX) orientation are preferred by some investigators, due to potential superiority in RV volume measurement for treatment planning. Unfortunately, due to the rare occurrence of these diseases, data in this domain is scarce. Recent research in deep learning-based methods mainly focused on SAX CMR images and they had proven to be very successful. In this work, we show that there is a considerable domain shift between AX and SAX images, and therefore, direct application of existing models yield sub-optimal results on AX samples. We propose a novel unsupervised domain adaptation approach, which uses task-related probabilities in an attention mechanism. Beyond that, cycle consistency is imposed on the learned patient-individual 3D rigid transformation to improve stability when automatically re-sampling the AX images to SAX orientations. The network was trained on 122 registered 3D AX-SAX CMR volume pairs from a multi-centric patient cohort. A mean 3D Dice of 0.86 ± 0.06 for the left ventricle, 0.65 ± 0.08 for the myocardium, and 0.77 ± 0.10 for the right ventricle could be achieved. This is an improvement of 25% in Dice for RV in comparison to direct application on axial slices. To conclude, our pre-trained task module has neither seen CMR images nor labels from the target domain, but is able to segment them after the domain gap is reduced. Code: https://github.com/Cardio-AI/3d-mri-domain-adaptation.