Publications by authors named "Frank Ong"

The purpose of this study was to determine the reliability of anthropometric measurements between two trained anthropometrists working in a team and one trained anthropometrist working with a child's parent/caregiver in a primary health care setting. An observational study to determine measurement reliability was conducted in a primary care child research network in Canada. In total, 120 children 0-5 years old had their anthropometric measurement taken twice by two trained anthropometrists working in a team and twice by one trained anthropometrist working with a child's parent/caregiver.

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Article Synopsis
  • Parallel imaging and compressed sensing for MRI face high computational costs, particularly for 3D non-Cartesian datasets, leading to the proposed coil sketching method to enhance reconstruction efficiency while maintaining image quality.
  • Coil sketching utilizes randomized sketching algorithms and incorporates high-energy virtual coils along with random combinations of lower-energy coils, effectively leveraging data from all coils without losing signal energy.
  • Experimental results demonstrate that coil sketching significantly improves computational speed—up to three times faster for high-dimensional non-Cartesian data—without compromising image quality or signal-to-noise ratio.
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Context: Compared with the relatively benign effects of increased subcutaneous adipose tissue (SAT), increased visceral adipose tissue (VAT) volume is a causal risk factor for hypertension, hyperlipidemia, type 2 diabetes, and cardiovascular disease. In rodents, increased VAT volume and triglyceride density and ectopic lipid accumulation in kidneys and liver have been induced by alterations in the gut microbiome. However, few studies have characterized these relationships in humans.

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Purpose: Three-dimensional UTE MRI has shown the ability to provide simultaneous structural and functional lung imaging, but it is limited by respiratory motion and relatively low lung parenchyma SNR. The purpose of this paper is to improve this imaging by using a respiratory phase-resolved reconstruction approach, named motion-compensated low-rank reconstruction (MoCoLoR), which directly incorporates motion compensation into a low-rank constrained reconstruction model for highly efficient use of the acquired data.

Theory And Methods: The MoCoLoR reconstruction is formulated as an optimization problem that includes a low-rank constraint using estimated motion fields to reduce the rank, optimizing over both the motion fields and reconstructed images.

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Background: Young children are often accompanied by their parent/caregiver when attending primary healthcare visits, where clinical procedures such as anthropometric measurements are conducted. Parents are not typically involved in their child's anthropometric measurement collection, and there are no recommendations for parental involvement during visits. The objective of this study was to describe parents' experiences with being involved in their child's anthropometric measurements.

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The Shinnar-Le-Roux (SLR) algorithm is widely used to design frequency selective pulses with large flip angles. We improve its design process to generate pulses with lower energy (by as much as 26%) and more accurate phase profiles. Concretely, the SLR algorithm consists of two steps: (1) an invertible transform between frequency selective pulses and polynomial pairs that represent Cayley-Klein (CK) parameters and (2) the design of the CK polynomial pair to match the desired magnetization profiles.

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Article Synopsis
  • The study aims to create a new method for high-resolution coronary magnetic resonance angiography (CMRA) that compensates for respiratory motion during free breathing.
  • The method uses a specific imaging technique (variable-density 3D cones trajectory) and incorporates advanced motion correction strategies to improve image quality.
  • Initial tests on six subjects show that this approach significantly enhances image sharpness compared to traditional methods, as evaluated by both cardiologists and quantitative metrics.
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Background: The prevalence of overweight (15%) and obesity (6%) in children under 5 years of age in Canada are high, and young children with overweight and obesity are at increased risk of the development of chronic disease(s) in adulthood. Prior research has demonstrated very few published trials on effective obesity prevention interventions in young children at risk of obesity, within primary healthcare settings. The aim of this study is to determine if 18-48-month-old children at risk for obesity, who are randomized to receive the Parents Together program (i.

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Childhood obesity is a growing worldwide problem. In adults, lower cold-induced brown adipose tissue (BAT) activity is linked to obesity and metabolic dysfunction; this relationship remains uncertain in children. In this cross-sectional study, we compared cold-induced supraclavicular (SCV) BAT activity (percent change in proton density fat fraction [PDFF]) within the SCV region after 1 h of whole-body cold exposure (18°C), using MRI in 26 boys aged 8-10 years: 13 with normal BMI and 13 with overweight/obesity.

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In rodents, lower brown adipose tissue (BAT) activity is associated with greater liver steatosis and changes in the gut microbiome. However, little is known about these relationships in humans. In adults (n = 60), we assessed hepatic fat and cold-stimulated BAT activity using magnetic resonance imaging and the gut microbiota with 16S sequencing.

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Purpose: ESPIRiT is a parallel imaging method that estimates coil sensitivity maps from the auto-calibration region (ACS). This requires choosing several parameters for the optimal map estimation. While fairly robust to these parameter choices, occasionally, poor selection can result in reduced performance.

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Background: Quantitative T * MRI is the standard of care for the assessment of iron overload. However, patient motion corrupts T * estimates.

Purpose: To develop and evaluate a motion-robust, simultaneous cardiac and liver T * imaging approach using non-Cartesian, rosette sampling and a model-based reconstruction as compared to clinical-standard Cartesian MRI.

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Purpose: To develop a framework to reconstruct large-scale volumetric dynamic MRI from rapid continuous and non-gated acquisitions, with applications to pulmonary and dynamic contrast-enhanced (DCE) imaging.

Theory And Methods: The problem considered here requires recovering 100 gigabytes of dynamic volumetric image data from a few gigabytes of k-space data, acquired continuously over several minutes. This reconstruction is vastly under-determined, heavily stressing computing resources as well as memory management and storage.

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Purpose: To rapidly reconstruct undersampled 3D non-Cartesian image-based navigators (iNAVs) using an unrolled deep learning (DL) model, enabling nonrigid motion correction in coronary magnetic resonance angiography (CMRA).

Methods: An end-to-end unrolled network is trained to reconstruct beat-to-beat 3D iNAVs acquired during a CMRA sequence. The unrolled model incorporates a nonuniform FFT operator in TensorFlow to perform the data-consistency operation, and the regularization term is learned by a convolutional neural network (CNN) based on the proximal gradient descent algorithm.

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Article Synopsis
  • Compressed sensing enhances MRI by reducing the number of samples needed below traditional limits (Nyquist rate) through techniques like wavelet transforms and low rank extensions.
  • The article emphasizes the use of both phenomenological image priors and explicit physical laws governing MRI signal dynamics to improve image reconstruction and quantitative analysis.
  • It explores model-based quantitative MRI, user-controllable scan parameters, and demonstrates multiple applications for enhanced multi-contrast imaging and accurate quantitative mapping.
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We propose a k-space preconditioning formulation for accelerating the convergence of iterative Magnetic Resonance Imaging (MRI) reconstructions from non-uniformly sampled k-space data. Existing methods either use sampling density compensations which sacrifice reconstruction accuracy, or circulant preconditioners which increase per-iteration computation. Our approach overcomes both shortcomings.

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Context: In rodents, cold exposure induces the activation of brown adipose tissue (BAT) and the induction of intracellular triacylglycerol (TAG) lipolysis. However, in humans, the kinetics of supraclavicular (SCV) BAT activation and the potential importance of TAG stores remain poorly defined.

Objective: To determine the time course of BAT activation and changes in intracellular TAG using MRI assessment of the SCV ( BAT depot) and fat in the posterior neck region ( non-BAT).

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Robustness against data inconsistencies, imaging artifacts and acquisition speed are crucial factors limiting the possible range of applications for magnetic resonance imaging (MRI). Therefore, we report a novel calibrationless parallel imaging technique which simultaneously estimates coil profiles and image content in a relaxed forward model. Our method is robust against a wide class of data inconsistencies, minimizes imaging artifacts and is comparably fast, combining important advantages of many conceptually different state-of-the-art parallel imaging approaches.

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In this work, we broadly connect kernel-based filtering (e.g. approaches such as the bilateral filter and nonlocal means, but also many more) with general variational formulations of Bayesian regularized least squares, and the related concept of proximal operators.

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The activation of brown adipose tissue (BAT) is associated with reductions in circulating lipids and glucose in rodents and contributes to energy expenditure in humans indicating the potential therapeutic importance of targetting this tissue for the treatment of a variety of metabolic disorders. In order to evaluate the therapeutic potential of human BAT, a variety of methodologies for assessing the volume and metabolic activity of BAT are utilized. Cold exposure is often utilized to increase BAT activity but inconsistencies in the characteristics of the exposure protocols make it challenging to compare findings.

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Article Synopsis
  • Developed a phase regularized image reconstruction method applicable to various imaging techniques such as partial Fourier and water-fat imaging.
  • Studied phase constraints within a regularized inverse problem framework and introduced the phase cycling technique to handle non-convexity and sensitivity to phase wraps.
  • Results showed reduced artifacts and strong performance in reconstructions, offering a robust alternative that encourages joint imaging applications without needing phase unwrapping.
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Purpose: To achieve motion robust high resolution 3D free-breathing pulmonary MRI utilizing a novel dynamic 3D image navigator derived directly from imaging data.

Methods: Five-minute free-breathing scans were acquired with a 3D ultrashort echo time (UTE) sequence with 1.25 mm isotropic resolution.

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We present a natural generalization of the recent low rank + sparse matrix decomposition and consider the decomposition of matrices into components of multiple scales. Such decomposition is well motivated in practice as data matrices often exhibit local correlations in multiple scales. Concretely, we propose a multi-scale low rank modeling that represents a data matrix as a sum of block-wise low rank matrices with increasing scales of block sizes.

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Premature birth in conjunction with extremely low birth weight (<1 kg, ELBW) is associated with insulin resistance and increased cardiometabolic health risk compared to birth at full term with normal birth weight (NBW). However, little is known regarding the biologic mediators of these effects. Abdominal and ectopic lipid accumulation is linked to insulin resistance and metabolic dysfunction, yet whether ELBW survivors are predisposed to aberrant lipid deposition in adulthood is unknown.

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Cancer is a genetic disease characterized by uncontrolled growth of abnormal cells. Over time, somatic mutations accumulate in the cells of an individual due to replication errors, chromosome segregation errors, or DNA damage. When not caught by traditional mechanisms, these somatic mutations can lead to cellular proliferation, the hallmark of cancer.

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