A5060043482- Advanced MRI Techniques and Applications
- Lanthanide and Transition Metal Complexes
- Electron Spin Resonance Studies
- MRI in cancer diagnosis
- Advanced Neuroimaging Techniques and Applications
- Acute Ischemic Stroke Management
- NMR spectroscopy and applications
- Bone and Joint Diseases
- Magnetism in coordination complexes
- Atomic and Subatomic Physics Research
- Radioactive element chemistry and processing
- Cerebrovascular and Carotid Artery Diseases
- Advanced NMR Techniques and Applications
- Functional Brain Connectivity Studies
- Cardiac Imaging and Diagnostics
- Graphene research and applications
- Gas Sensing Nanomaterials and Sensors
- Epilepsy research and treatment
- Photoacoustic and Ultrasonic Imaging
- Fetal and Pediatric Neurological Disorders
- Nanoplatforms for cancer theranostics
- Nanopore and Nanochannel Transport Studies
- Intracerebral and Subarachnoid Hemorrhage Research
- Renal function and acid-base balance
- Inhalation and Respiratory Drug Delivery
Imaging Center
2018-2024
Emory University
2018-2024
Emory National Primate Research Center
2018-2024
Harvard University
2014-2023
Athinoula A. Martinos Center for Biomedical Imaging
2014-2023
Massachusetts General Hospital
2014-2023
Emory and Henry College
2022
University of Manchester
2020
Henry Royce Institute
2020
Tianjin Medical University
2018
The classic definition of the ischemic penumbra is a hypoperfused region in which metabolism impaired, but still sufficient to maintain cellular polarization. Perfusion- and diffusion-weighted MRI (PWI, DWI) can identify regions reduced perfusion depolarization, respectively, it often remains unclear whether PWI—DWI mismatch corresponds benign oligemia or true penumbra. We hypothesized that pH-weighted (pHWI) subdivide into these regions. Twenty-one rats underwent permanent middle cerebral...
Abstract The ability to measure proton exchange rates in tissue using MRI would be very useful for quantitative assessment of magnetization transfer properties, both conventional MT imaging and the more recent chemical saturation (CEST) approach. CEST is a new MR contrast mechanism that depends on several factors, including rate labile protons agent pH‐dependent manner. Two methods monitor local based are introduced. two MRI‐compatible approaches quantifying time (QUEST) dependence power...
The proton exchange processes between water and solutes containing exchangeable protons have recently become of interest for monitoring pH effects, detecting cellular mobile proteins peptides, enhancing the detection sensitivity various low-concentration endogenous exogenous species. In this work, analytic expressions (WEX) filter spectroscopy, chemical exchange-dependent saturation transfer (CEST), amide (APT) experiments are derived by use Bloch equations with terms. effects initial states...
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism for magnetic resonance imaging (MRI). CEST MRI selectively saturates exchangeable protons that are transferred to MRI-detectable bulk water signal. MRI-CEST (pH)-responsive agents probes able map pH in the microenvironment which they distribute. To minimize confounding effects of agent concentration, researchers have developed ratiometric imaging, investigates containing multiple magnetically non-equivalent proton...
Abstract Chemical exchange saturation transfer (CEST) imaging provides an indirect detection mechanism that allows quantification of certain labile groups unobservable using conventional MRI. Recently, amide proton (APT) imaging, a variant form CEST has been shown capable detecting lactic acidosis during acute ischemia, providing information complementary to perfusion and diffusion However, contrast is usually small, therefore, it important optimize experimental conditions for reliable...
Abstract Chemical exchange saturation transfer (CEST) MRI provides a sensitive detection mechanism that allows characterization of dilute labile protons usually undetectable by conventional MRI. Particularly, amide proton (APT) imaging, variant CEST MRI, has been shown capable detecting ischemic acidosis, and may serve as surrogate metabolic imaging marker. For preclinical continuous‐wave (CW) radiofrequency (RF) irradiation is often applied so the steady state contrast can be reached. On...
Abstract Chemical exchange saturation transfer (CEST) MRI has been shown capable of detecting dilute labile protons and abnormal tissue glucose/oxygen metabolism, thus, may serve as a complementary imaging technique to the conventional methods. CEST imaging, however, is also dependent on experimental parameters such power, duration, waveform irradiation RF pulse. As result, its sensitivity specificity for microenvironment properties pH not optimal. In this study, dependence contrast was...
The ischemic tissue becomes acidic after initiation of anaerobic respiration, which may result in impaired metabolism and, ultimately, severe damage. Although changes the major cerebral metabolites can be studied using magnetic resonance (MR) spectroscopy (MRS)-based techniques, their spatiotemporal resolution is often not sufficient for routine examination fast-evolving and heterogeneous acute stroke lesions. Recently, pH-weighted MR imaging (MRI) has been proposed as a means to assess...
Chemical Exchange Saturation Transfer (CEST) MRI is sensitive to dilute metabolites with exchangeable protons, allowing tissue characterization in diseases such as acute stroke and tumor. CEST quantification using multi-pool Lorentzian fitting challenging due its strong dependence on image signal-to-noise ratio (SNR), initial values boundaries. Herein we proposed an Image Downsampling Expedited Adaptive Least-squares (IDEAL) algorithm that quantifies images based from of iteratively less...
Abstract Amide proton transfer (APT) imaging employs the chemical exchange saturation (CEST) mechanism to detect mobile endogenous proteins and peptides. It can be used pH reduction during acute ischemia thus provide complementary information perfusion‐weighted (PWI) diffusion‐weighted (DWI) imaging. However, APT contrast depends strongly on choice of parameters, especially radiofrequency (RF) time strength, which need optimized. In this work it is shown that even though at least three pools...
Ischemic tissue damage is heterogeneous, resulting in complex patterns the widely used diffusion-weighted MRI. Our study examined spatiotemporal characteristics of diffusion kurtosis imaging an animal model transient middle cerebral artery occlusion.Adult male Wistar rats (N=18) were subjected to 90 minutes occlusion. Multiparametric MR images obtained during occlusion and 20 after reperfusion with MRI using 8 b-values from 250 3000 s/mm(2) 6 gradient directions. Diffusion lesions outlined...
Abstract Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is capable of measuring dilute labile protons and microenvironmental properties. However, the CEST contrast dependent upon experimental conditions—particularly, radiofrequency (RF) irradiation scheme. Although continuous‐wave RF has been used conventionally, limited pulse duration or duty cycle most clinical systems requires use pulsed irradiation. Here, conventional numerical simulation extended to...
Purpose As the field of CEST grows, various novel preparation periods using different parameters are being introduced. At same time, large, multisite clinical studies require clearly defined protocols, especially across vendors. Here, we propose a definition standard open Pulseq format for shareable, simple, and exact protocols. Methods We present benefits such in three ways: (1) an database on GitHub, where fully defined, human‐readable protocols can be shared; (2) open‐source...
Abstract Development of imaging techniques that would allow the mapping immune cells in vivo could greatly aid our understanding a number inflammatory and autoimmune diseases. The current study focused on destruction insulin‐producing pancreatic beta‐cells by cytotoxic lymphocytes, cause insulin‐dependent diabetes mellitus (IDDM; Type 1 diabetes). Using high‐resolution MR microscopy conventional clinical system, it was possible to visualize infiltration diabetic mouse pancreas. Mouse...
Abstract Amide proton transfer (APT) imaging is a variant of magnetization (MT) imaging, in which the contrast determined by change water intensity due to chemical exchange with saturated amide protons endogenous mobile proteins and peptides. In this study, eight Fisher 344 rats implanted 9L gliosarcoma cells six nude human glioblastoma were imaged at 4.7 T. There increased signal intensities tumors APT‐weighted images. The APT between tumor contralateral brain tissue was about 3.9% (1.49 ±...
Abstract Amide proton transfer (APT) imaging is a variant form of chemical exchange saturation (CEST) that based on the magnetization between bulk water and labile endogenous amide protons. Given pH‐dependent, APT has been shown capable ischemic tissue acidosis, as such, may serve surrogate metabolic marker complementary to perfusion diffusion MRI. In order for properly diagnose heterogeneous pathologies such stroke cancer, fast volumetric be developed. this study evolution CEST contrast...
Background and Purpose— In acute stroke, mismatch between lesions seen on diffusion- (DWI) perfusion-weighted (PWI) MRI has been used to identify ischemic tissue before irreversible damage. Nevertheless, the concept of PWI/DWI is oversimplified metabolic status outcome are often heterogeneous. Tissue pH, a well-regulated physiological index that alters disrupted metabolism, may provide surrogate imaging marker augments DWI PWI for penumbra imaging. Methods— pH-weighted was obtained by...
Abstract Chemical exchange saturation transfer (CEST) MRI is a versatile imaging technique for measuring microenvironment properties via dilute CEST labile groups. Conventionally, implemented with long radiofrequency irradiation module, followed by fast image acquisition to obtain the steady state contrast. Nevertheless, sensitivity, scan time, and spatial coverage of conventional method may not be optimal. Our study proposed segmented labeling scheme that includes primary module generate...