Low dose threshold for measuring cardiac functional metrics using four-dimensional CT with deep learning.

Background: Four-dimensional CT is increasingly used for functional cardiac imaging, including prognosis for conditions such as heart failure and post myocardial infarction. However, radiation dose from an acquisition spanning the full cardiac cycle remains a concern. This work investigates the possibility of dose reduction in 4DCT using deep learning (DL)-based segmentation techniques as an objective observer.

The long-term vascular and myocardial outcomes in selected Kawasaki disease patients with regression of giant coronary artery aneurysms.

Background: Giant coronary artery aneurysms and myocardial fibrosis after Kawasaki disease may lead to devastating cardiovascular outcomes. We characterised the vascular and myocardial outcomes in five selected Kawasaki disease patients with a history of giant coronary artery aneurysms that completely regressed.

Methods: Five patients were selected who had giant coronary artery aneurysm in early childhood that regressed when studied 12-33 years after Kawasaki disease onset.

Bolus tracking from pulsed x-ray projections: A feasibility study using a five-dimensional cardiac CT contrast dynamics model.

Background: Cardiac computed tomography (CT) exams are some of the most complex CT exams due to the need to carefully time the scan when the heart chambers are near the peak contrast concentration. With current "bolus tracking" and "timing bolus" techniques, after contrast medium is injected, a target vessel or chamber is scanned periodically, and images are reconstructed to monitor the opacification. Both techniques have opportunities for improvement, such as reducing the contrast medium volume, the exam time, the number of manual steps, and improving the robustness of correctly timing the peak opacification.

Geometric Changes in Mitral Valve Apparatus during Long-term Cardiac Resynchronization Therapy as Assessed with Cardiac CT.

Purpose To assess long-term geometric changes of the mitral valve apparatus using cardiac CT in individuals who underwent cardiac resynchronization therapy (CRT). Materials and Methods Participants from a randomized controlled trial with cardiac CT examinations before CRT implantation and at 6 months follow-up (Clinicaltrials.gov identifier NCT01323686) were invited to undergo an additional long-term follow-up cardiac CT examination.

Protocol optimization for functional cardiac CT imaging using noise emulation in the raw data domain.

Background: Four-dimensional (4D) wide coverage computed tomography (CT) is an effective imaging modality for measuring the mechanical function of the myocardium. However, repeated CT measurement across a number of heartbeats is still a concern.

Purpose: A projection-domain noise emulation method is presented to generate accurate low-dose (mA modulated) 4D cardiac CT scans from high-dose scans, enabling protocol optimization to deliver sufficient image quality for functional cardiac analysis while using a dose level that is as low as reasonably achievable (ALARA).

Protocol Optimization for Functional Cardiac CT Imaging Using Noise Emulation in the Raw Data Domain.

Background: Four-dimensional (4D) wide coverage computed tomography (CT) is an effective imaging modality for measuring the mechanical function of the myocardium. However, repeated CT measurement across a number of heartbeats is still a concern.

Purpose: A projection-domain noise emulation method is presented to generate accurate low-dose (mA modulated) 4D cardiac CT scans from high-dose scans, enabling protocol optimization to deliver sufficient image quality for functional cardiac analysis while using a dose level that is as low as reasonably achievable (ALARA).

Motion correction of wide-detector 4DCT images for cardiac resynchronization therapy planning.

Background: Lead placement at the latest mechanically activated left ventricle (LV) segments is strongly correlated with response to cardiac resynchronization therapy (CRT). We demonstrate the feasibility of a cardiac 4DCT motion correction algorithm (ResyncCT) in estimating LV mechanical activation for guiding lead placement in CRT.

Methods: Subjects with full cardiac cycle 4DCT images acquired using a wide-detector CT scanner for CRT planning/upgrade were included.

Efficient multi-fidelity computation of blood coagulation under flow.

Clot formation is a crucial process that prevents bleeding, but can lead to severe disorders when imbalanced. This process is regulated by the coagulation cascade, a biochemical network that controls the enzyme thrombin, which converts soluble fibrinogen into the fibrin fibers that constitute clots. Coagulation cascade models are typically complex and involve dozens of partial differential equations (PDEs) representing various chemical species' transport, reaction kinetics, and diffusion.

Quantitative analysis of small coronary artery calcium detectability with an accurate simulation and validation on a clinical CT scanner.

Background: The absence of coronary artery calcium (CAC) measured via CT is associated with very favorable prognosis, and current guidelines recommend low-density lipoprotein cholesterol (LDL-c) lowering therapy for individuals with any CAC. This motivates early detection of small granules of CAC; however, calcium scan sensitivity for detecting very low levels of calcium has not been quantified.

Purpose: In this work, the size limit of detectability of small calcium hydroxyapatite (CaHA) granules with clinical CAC scanning was assessed using validated simulations.

Pulmonary vein flow split effects in patient-specific simulations of left atrial flow.

Disruptions to left atrial (LA) blood flow, such as those caused by atrial fibrillation (AF), can lead to thrombosis in the left atrial appendage (LAA) and an increased risk of systemic embolism. LA hemodynamics are influenced by various factors, including LA anatomy and function, and pulmonary vein (PV) inflow conditions. In particular, the PV flow split can vary significantly among and within patients depending on multiple factors.

Myocardial Regional Shortening from 4D Cardiac CT Angiography for the Detection of Left Ventricular Segmental Wall Motion Abnormality.

Purpose: To investigate whether endocardial regional shortening computed from four-dimensional (4D) CT angiography (RS) can be used as a decision classifier to detect the presence of left ventricular (LV) wall motion abnormalities (WMAs).

Materials And Methods: One hundred electrocardiographically gated cardiac 4D CT studies (mean age, 59 years ± 14 [SD]; 61 male patients) conducted between April 2018 and December 2020 were retrospectively evaluated. Three experts labeled LV wall motion in each of the 16 American Heart Association (AHA) segments as normal or abnormal; they also measured peak RS across one heartbeat in each segment.

Detection of left ventricular wall motion abnormalities from volume rendering of 4DCT cardiac angiograms using deep learning.

Background: The presence of left ventricular (LV) wall motion abnormalities (WMA) is an independent indicator of adverse cardiovascular events in patients with cardiovascular diseases. We develop and evaluate the ability to detect cardiac wall motion abnormalities (WMA) from dynamic volume renderings (VR) of clinical 4D computed tomography (CT) angiograms using a deep learning (DL) framework.

Methods: Three hundred forty-three ECG-gated cardiac 4DCT studies (age: 61 ± 15, 60.

Regional left ventricular endocardial strains estimated from low-dose 4DCT: Comparison with cardiac magnetic resonance feature tracking.

Background: Estimates of regional left ventricular (LV) strains provide additional information to global function parameters such as ejection fraction (EF) and global longitudinal strain (GLS) and are more sensitive in detecting abnormal regional cardiac function. The accurate and reproducible assessment of regional cardiac function has implications in the management of various cardiac diseases such as heart failure, myocardial ischemia, and dyssynchrony.

Purpose: To develop a method that yields highly reproducible, high-resolution estimates of regional endocardial strains from 4DCT images.

Coronary artery calcium and cardiovascular disease prediction by scanner type: the multi-ethnic study of atherosclerosis.

Aim: To evaluate the predictive value of coronary artery calcium (CAC) scoring methods across cardiac computed tomography (CT) scanner types.

Materials And Methods: CAC was measured in participants from the MESA (Multi-Ethnic Study of Atherosclerosis), a prospective cohort study of participants free of baseline cardiovascular disease (CVD), using either EBCT (electron beam CT) or MDCT (multidetector CT). The risks for incident coronary heart disease (CHD) and CVD events were compared for CAC scores per SD using Cox proportional hazards models with multivariable adjustment in 3,362 MESA participants with detectable CAC.

Four-dimensional computed tomography of the left ventricle, Part I: Motion artifact reduction.

Purpose: Standard four-dimensional computed tomography (4DCT) cardiac reconstructions typically include spiraling artifacts that depend not only on the motion of the heart but also on the gantry angle range over which the data was acquired. We seek to reduce these motion artifacts and, thereby, improve the accuracy of left ventricular wall positions in 4DCT image series.

Methods: We use a motion artifact reduction approach (ResyncCT) that is based largely on conjugate pairs of partial angle reconstruction (PAR) images.

Non-Newtonian blood rheology impacts left atrial stasis in patient-specific simulations.

The lack of mechanically effective contraction of the left atrium (LA) during atrial fibrillation (AF) disturbs blood flow, increasing the risk of thrombosis and ischemic stroke. Thrombosis is most likely in the left atrial appendage (LAA), a small narrow sac where blood is prone to stagnate. Slow flow promotes the formation of erythrocyte aggregates in the LAA, also known as rouleaux, causing viscosity gradients that are usually disregarded in patient-specific simulations.

M-SiSSR: Regional Endocardial Function Using Multilabel Simultaneous Subdivision Surface Registration.

Quantification of regional cardiac function is a central goal of cardiology. Multiple methods, such as Coherent Point Drift (CPD) and Simultaneous Subdivision Surface Registration (SiSSR), have been used to register meshes to the endocardial surface. However, these methods do not distinguish between cardiac chambers during registration, and consequently the mesh may "slip" across the interface between two structures during contraction, resulting in inaccurate regional functional measurements.

Four-dimensional computed tomography of the left ventricle, Part II: Estimation of mechanical activation times.

Purpose: We demonstrate the viability of a four-dimensional X-ray computed tomography (4DCT) imaging system to accurately and precisely estimate mechanical activation times of left ventricular (LV) wall motion. Accurate and reproducible timing estimates of LV wall motion may be beneficial in the successful planning and management of cardiac resynchronization therapy (CRT).

Methods: We developed an anthropomorphically accurate in silico LV phantom based on human CT images with programmed septal-lateral wall dyssynchrony.

Preliminary clinical validation of a new picture-based visual acuity test in children with amblyopia: a comparison of The Auckland Optotypes and crowded logMAR letters.

Background/aims: Amblyopia is the most common visual deficit in children and accurate visual acuity (VA) assessment is essential for diagnosis. While ETDRS high-contrast logMAR VA is the reference standard test for adults, less agreement exists for pre-literate children. A new picture optotype acuity test (The Auckland Optotypes [TAO]) has shown favourable comparison to letter acuity charts but has not yet been evaluated in children with amblyopia.

Novel 4DCT Method to Measure Regional Left Ventricular Endocardial Shortening Before and After Transcatheter Mitral Valve Implantation.

Background: Regional left ventricular (LV) mechanics in mitral regurgitation (MR) patients, and local changes in function after transcatheter mitral valve implantation (TMVI) have yet to be evaluated. Herein, we introduce a method for creating high resolution maps of endocardial function from 4DCT images, leading to detailed characterization of changes in local LV function. These changes are particularly interesting when evaluating the effect of the Tendyne TMVI device in the region of the epicardial pad.