Publications by authors named "Yohan Jun"

Article Synopsis
  • The study aimed to create a new MRI pulse sequence called PRIME, which improves diffusion MRI by adding an echo to obtain high-resolution images without increasing scan time.
  • The PRIME technique uses two echoes: one for detailed diffusion imaging and the second for generating accurate field maps or matching resolutions for efficient data acquisition.
  • Results showed that the PRIME sequence successfully achieved fast and clear diffusion imaging in healthy volunteers, allowing for high-quality images and detailed analysis without distortion.
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Article Synopsis
  • - Recent advances in brain MRI technology are enhancing diagnostic capabilities for intracranial diseases through two main areas: deep learning reconstruction (DLR) and quantitative imaging techniques.
  • - DLR utilizes deep neural networks to produce high-quality images more quickly, improving the signal-to-noise ratio and spatial resolution while making scanning faster.
  • - Quantitative MRI techniques allow for precise brain-tissue parameter calculations, which help improve diagnostic accuracy, but challenges like DLR instabilities and bias limitations are also addressed in the review.
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Article Synopsis
  • The study aims to create and assess methods for enhancing 3D imaging techniques, specifically using a low-rank subspace method and deep learning to improve accuracy and speed in T1 and T2 mapping.
  • Two innovative approaches were proposed: subspace QALAS, a low-rank method for quantification, and Zero-DeepSub, a deep-learning reconstruction technique that boosts imaging performance.
  • Results showed that these methods significantly improved image quality and accuracy, allowing for rapid whole-brain imaging at high resolution with less noise and artifacts compared to traditional methods.
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Article Synopsis
  • The study developed a new method called SSL-QALAS for quickly estimating multiparametric T1, T2, proton density, and inversion efficiency maps from MRI data using self-supervised learning (SSL).
  • This method allows rapid, dictionary-free mapping and was evaluated against traditional dictionary-matching techniques using both phantom and in vivo experiments, exhibiting strong accuracy and agreement with reference values.
  • Key findings indicate that SSL-QALAS can reconstruct multiparametric maps within 10 seconds and adapt to specific scan data in just 15 minutes, making it a promising tool for improving MRI efficiency.
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Objectives: An appropriate and fast clinical referral suggestion is important for intra-axial mass-like lesions (IMLLs) in the emergency setting. We aimed to apply an interpretable deep learning (DL) system to multiparametric MRI to obtain clinical referral suggestion for IMLLs, and to validate it in the setting of nontraumatic emergency neuroradiology.

Methods: A DL system was developed in 747 patients with IMLLs ranging 30 diseases who underwent pre- and post-contrast T1-weighted (T1CE), FLAIR, and diffusion-weighted imaging (DWI).

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Objectives: To establish a robust interpretable multiparametric deep learning (DL) model for automatic noninvasive grading of meningiomas along with segmentation.

Methods: In total, 257 patients with pathologically confirmed meningiomas (162 low-grade, 95 high-grade) who underwent a preoperative brain MRI, including T2-weighted (T2) and contrast-enhanced T1-weighted images (T1C), were included in the institutional training set. A two-stage DL grading model was constructed for segmentation and classification based on multiparametric three-dimensional U-net and ResNet.

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A wearable silent speech interface (SSI) is a promising platform that enables verbal communication without vocalization. The most widely studied methodology for SSI focuses on surface electromyography (sEMG). However, sEMG suffers from low scalability because of signal quality-related issues, including signal-to-noise ratio and interelectrode interference.

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Accelerating MRI scans is one of the principal outstanding problems in the MRI research community. Towards this goal, we hosted the second fastMRI competition targeted towards reconstructing MR images with subsampled k-space data. We provided participants with data from 7,299 clinical brain scans (de-identified via a HIPAA-compliant procedure by NYU Langone Health), holding back the fully-sampled data from 894 of these scans for challenge evaluation purposes.

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Objectives: To evaluate whether a deep learning (DL) model using both three-dimensional (3D) black-blood (BB) imaging and 3D gradient echo (GRE) imaging may improve the detection and segmentation performance of brain metastases compared to that using only 3D GRE imaging.

Methods: A total of 188 patients with brain metastases (917 lesions) who underwent a brain metastasis MRI protocol including contrast-enhanced 3D BB and 3D GRE were included in the training set. DL models based on 3D U-net were constructed.

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Quantitative tissue characteristics, which provide valuable diagnostic information, can be represented by magnetic resonance (MR) parameter maps using magnetic resonance imaging (MRI); however, a long scan time is necessary to acquire them, which prevents the application of quantitative MR parameter mapping to real clinical protocols. For fast MR parameter mapping, we propose a deep model-based MR parameter mapping network called DOPAMINE that combines a deep learning network with a model-based method to reconstruct MR parameter maps from undersampled multi-channel k-space data. DOPAMINE consists of two networks: 1) an MR parameter mapping network that uses a deep convolutional neural network (CNN) that estimates initial parameter maps from undersampled k-space data (CNN-based mapping), and 2) a reconstruction network that removes aliasing artifacts in the parameter maps with a deep CNN (CNN-based reconstruction) and an interleaved data consistency layer by an embedded MR model-based optimization procedure.

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Deep learning has recently achieved remarkable results in the field of medical imaging. However, as a deep learning network becomes deeper to improve its performance, it becomes more difficult to interpret the processes within. This can especially be a critical problem in medical fields where diagnostic decisions are directly related to a patient's survival.

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Article Synopsis
  • The study introduces a domain-transform framework called DOTA-MRI, aimed at improving the reconstruction of images from undersampled Cartesian magnetic resonance imaging (MRI) data.
  • It utilizes an initial analytic transform, specifically a 1D inverse Fourier transform (IFT), to efficiently convert undersampled k-space data into images while reducing the complexity of the learning process for neural networks.
  • By focusing on a 1D global transform in the phase-encoding direction, the method minimizes memory demands, making it suitable for high-resolution MR datasets, which traditional approaches struggle to handle.
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The ideal combination of high optical transparency and high electrical conductivity, especially at very low frequencies of less than the gigahertz (GHz) order, such as the radiofrequencies at which electronic devices operate (tens of kHz to hundreds of GHz), is fundamental incompatibility, which creates a barrier to the realization of enhanced user interfaces and 'device-to-device integration.' Herein, we present a design strategy for preparing a megahertz (MHz)-transparent conductor, based on a plasma frequency controlled by the electrical conductivity, with the ultimate goal of device-to-device integration through electromagnetic wave transmittance. This approach is verified experimentally using a conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), the microstructure of which is manipulated by employing a solution process.

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Purpose: To develop and evaluate a method of parallel imaging time-of-flight (TOF) MRA using deep multistream convolutional neural networks (CNNs).

Methods: A deep parallel imaging network ("DPI-net") was developed to reconstruct 3D multichannel MRA from undersampled data. It comprises 2 deep-learning networks: a network of multistream CNNs for extracting feature maps of multichannel images and a network of reconstruction CNNs for reconstructing images from the multistream network output feature maps.

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Black-blood (BB) imaging is used to complement contrast-enhanced 3D gradient-echo (CE 3D-GRE) imaging for detecting brain metastases, requiring additional scan time. In this study, we proposed deep-learned 3D BB imaging with an auto-labelling technique and 3D convolutional neural networks for brain metastases detection without additional BB scan. Patients were randomly selected for training (29 sets) and testing (36 sets).

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Purpose: To demonstrate accurate MR image reconstruction from undersampled k-space data using cross-domain convolutional neural networks (CNNs) METHODS: Cross-domain CNNs consist of 3 components: (1) a deep CNN operating on the k-space (KCNN), (2) a deep CNN operating on an image domain (ICNN), and (3) an interleaved data consistency operations. These components are alternately applied, and each CNN is trained to minimize the loss between the reconstructed and corresponding fully sampled k-spaces. The final reconstructed image is obtained by forward-propagating the undersampled k-space data through the entire network.

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Purpose: To develop an effective method that can suppress noise in successive multiecho T (*)-weighted magnetic resonance (MR) brain images while preventing filtering artifacts.

Materials And Methods: For the simulation experiments, we used multiple T -weighted images of an anatomical brain phantom. For in vivo experiments, successive multiecho MR brain images were acquired from five healthy subjects using a multiecho gradient-recalled-echo (MGRE) sequence with a 3T MRI system.

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