A5017843895- Advanced MRI Techniques and Applications
- Advanced Neuroimaging Techniques and Applications
- MRI in cancer diagnosis
- Medical Imaging Techniques and Applications
- Osteoarthritis Treatment and Mechanisms
- Photoacoustic and Ultrasonic Imaging
- Lower Extremity Biomechanics and Pathologies
- Cardiac Imaging and Diagnostics
- Advanced X-ray and CT Imaging
- Radiomics and Machine Learning in Medical Imaging
- Knee injuries and reconstruction techniques
- Total Knee Arthroplasty Outcomes
- Atomic and Subatomic Physics Research
- Ultrasound Imaging and Elastography
- NMR spectroscopy and applications
- Bone and Joint Diseases
- Sparse and Compressive Sensing Techniques
- Orthopedic Infections and Treatments
- Ultrasound and Hyperthermia Applications
- Cancer-related molecular mechanisms research
- Surgical Simulation and Training
- Orthopaedic implants and arthroplasty
- Augmented Reality Applications
- Electron Spin Resonance Studies
- Cardiovascular Function and Risk Factors
Stanford University
2016-2025
Northern Health
2025
University Radiology
2019-2025
Palo Alto University
2017-2022
Olea Medical (France)
2022
Stratford University
2017
Hewlett-Packard (United States)
2017
Stanford Medicine
2005-2014
Resonance Research (United States)
2005
VA Palo Alto Health Care System
2003
Magnetic resonance imaging (MRI) near metallic implants remains an unmet need because of severe artifacts, which mainly stem from large metal-induced field inhomogeneities. This work addresses MRI with innovative technique called "Slice Encoding for Metal Artifact Correction" (SEMAC). The SEMAC corrects metal artifacts via robust encoding each excited slice against is achieved by extending a view-angle-tilting (VAT) spin-echo sequence additional z-phase encoding. Although the VAT...
To develop a super-resolution technique using convolutional neural networks for generating thin-slice knee MR images from thicker input slices, and compare this method with alternative through-plane interpolation methods.We implemented 3D network entitled DeepResolve to learn residual-based transformations between high-resolution lower-resolution thick-slice at the same center locations. was trained 124 double echo in steady-state (DESS) data sets 0.7-mm slice thickness tested on 17...
Abstract Purpose To combine gradient‐echo (GRE) imaging with a multipoint water–fat separation method known as “iterative decomposition of water and fat echo asymmetry least squares estimation” (IDEAL) for uniform separation. Robust suppression is necessary many GRE applications; unfortunately, challenging in the presence B 0 inhomogeneities. These challenges are addressed IDEAL technique. Materials Methods Echo shifts three‐point were chosen to optimize noise performance estimation, which...
The 3D Cones k-space trajectory has many desirable properties for rapid and ultra-short echo time magnetic resonance imaging. An algorithm is presented that generates the gradient waveforms given a desired field of view resolution. enables favorable trade-off between increases in readout decreases total number required readouts. resulting very signal-to-noise ratio (SNR) efficient excellent aliasing properties. A high-resolution imaging sequence used to compare projection reconstruction...
Purpose To develop a method that combines parallel imaging and compressed sensing to enable faster and/or higher spatial resolution magnetic resonance (MR) show its feasibility in pediatric clinical setting. Materials Methods Institutional review board approval was obtained for this HIPAA-compliant study, informed consent or assent given by subjects. A pseudorandom k-space undersampling pattern incorporated into three-dimensional (3D) gradient-echo sequence; aliasing then has an incoherent...
Abstract The recently developed multi‐acquisition with variable resonance image combination (MAVRIC) and slice‐encoding metal artifact correction (SEMAC) techniques can significantly reduce artifacts commonly encountered near embedded hardware. These reductions are enabled by applying alternative spectral spatial‐encoding schemes to conventional spin‐echo imaging techniques. Here, the MAVRIC SEMAC concepts connected discussed. development of a hybrid technique that utilizes strengths both...
Abstract Refocused steady‐state free precession (SSFP) is limited by its high sensitivity to local field variation, particularly at strengths or the long repetition times (TRs) necessary for resolution. Several methods have been proposed reduce SSFP banding artifact combining multiple phase‐cycled acquisitions, each differing in how individual signal magnitudes and phases are combined. These include maximum‐intensity (MI‐SSFP) complex‐sum (CS‐SSFP). The reduction accompanied a loss...
Abstract Balanced steady‐state free precession (SSFP) imaging sequences require short repetition times (TRs) to avoid off‐resonance artifacts. The use of slab‐selective excitations is common, as this can improve speed by limiting the field view (FOV). However, necessarily short‐duration have poor slab profiles. This results in unusable slices at edge due significant flip‐angle variations or aliasing direction. Variable‐rate selective excitation (VERSE) a technique which time‐varying gradient...
Abstract Purpose: To develop and evaluate a multiphasic contrast‐enhanced MRI method called DIfferential Sub‐sampling with Cartesian Ordering (DISCO) for abdominal imaging. Materials Methods: A three‐dimensional, variable density pseudo‐random k ‐space segmentation scheme was developed combined Dixon‐based fat‐water separation algorithm to generate high temporal resolution images robust fat suppression without compromise in spatial or coverage. With institutional review board approval...
Purpose To organize a multi-institute knee MRI segmentation challenge for characterizing the semantic and clinical efficacy of automatic methods relevant monitoring osteoarthritis progression. Materials Methods A dataset partition consisting three-dimensional from 88 retrospective patients at two time points (baseline 1-year follow-up) with ground truth articular (femoral, tibial, patellar) cartilage meniscus segmentations was standardized. Challenge submissions majority-vote ensemble were...
Abstract Refocused steady‐state free precession (SSFP) imaging sequences have recently regained popularity as faster gradient hardware has allowed shorter repetition times, thereby reducing SSFP's sensitivity to off‐resonance effects. Although these offer fast scanning with good signal‐to‐noise efficiency, the “transient response,” or time taken reach a steady‐state, can be long compared total time, particularly when using 2D sequences. This results in lost and made SSFP difficult use for...
Abstract Purpose To compare signal‐to‐noise ratios (S/N) and contrast‐to‐noise (C/N) in various MR sequences, including fat‐suppressed three‐dimensional spoiled gradient‐echo (SPGR) imaging, fast spin echo (FSE) driven equilibrium Fourier transform (DEFT) to determine the diagnostic accuracy of these imaging sequences for detecting cartilage lesions osteoarthritic knees, as compared with arthroscopy. Materials Methods Two sagittal FSE images (repetition time [TR] / [TE], 4000/13 [FSE short...
To evaluate two magnetic resonance imaging (MRI) techniques, slice encoding for metal artifact correction (SEMAC) and multiacquisition variable-resonance image combination (MAVRIC), their ability to correct artifacts in postoperative knees with metal.A total of 25 were imaged this study. Fourteen knee replacements (TKRs) volunteers scanned SEMAC, MAVRIC, 2D fast spin-echo (FSE) measure extent implant rotation. The the sequences rotation dimensions was compared a TKR model. Eleven patients...
T2 mapping and diffusion-weighted imaging complement morphological for assessing cartilage disease injury. The double echo steady state sequence has been used generates two echoes with markedly different diffusion weighting. Modifying the spoiler gradient area flip angle of allows greater control weighting both echoes. Data from acquisitions areas angles are to simultaneously estimate apparent coefficient each voxel. This method is verified in phantoms validated vivo knee; estimates regions...
Abstract Purpose: To demonstrate accelerated imaging with both artifact reduction and different contrast mechanisms near metallic implants. Materials Methods: Slice‐encoding for metal correction (SEMAC) is a modified spin echo sequence that uses view‐angle tilting slice‐direction phase encoding to correct in‐plane through‐plane artifacts. Standard trains short‐TI inversion recovery (STIR) allow efficient PD‐weighted optional fat suppression. A completely linear reconstruction allows...
The prevalence of pseudotumors in patients with large-head metal-on-metal (MOM) THA has been the subject implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI superior for detection pseudotumors.We prospectively compared to pseudotumor an asymptomatic cohort MOM THAs. We also assessment growth progressive soft tissue involvement at a 6-month interval.We enrolled 40 THAs study. mean age was 54 years (range, 34-76 years)....
Metal Artifact Reduction With MAVRIC SL at 3-T MRI in Patients Hip ArthroplastySoo-Jung Choi1, Kevin M. Koch2, Brian A. Hargreaves3, Kathryn J. Stevens3 and Garry E. Gold3Audio Available | Share
Background Super‐resolution is an emerging method for enhancing MRI resolution; however, its impact on image quality still unknown. Purpose To evaluate super‐resolution using quantitative and qualitative metrics of cartilage morphometry, osteophyte detection, global blurring. Study Type Retrospective. Population In all, 176 studies subjects at varying stages osteoarthritis. Field Strength/Sequence Original‐resolution 3D double‐echo steady‐state (DESS) DESS with 3× thicker slices...