Endogenous chemical exchange saturation transfer (CEST) effects are always diluted by competing effects, such as direct water proton (spillover) and semi-solid macromolecular magnetization (MT). This leads to unwanted T2 MT signal contributions that lessen the CEST specificity underlying biochemical processes. A spillover correction is of special interest for clinical static field strengths protons resonating near peak. case all endogenous agents, amide transfer, –OH-CEST glycosaminoglycans,...

Chemical exchange saturation transfer (CEST) provides an indirect means to detect exchangeable protons within tissues through their effects on the water signal. Previous studies have suggested that amide proton (APT) imaging, a specific form of CEST, detects endogenous with resonance frequency offset 3.5 ppm downfield from water, and thus may be sensitive variations in mobile proteins/peptides tumors. However, as CEST measurements are influenced by various confounding effects, such spillover...

Off‐resonant RF irradiation in tissue indirectly lowers the water signal by saturation transfer processes: on one hand, there are selective chemical exchange (CEST) effects originating from exchanging endogenous protons resonating a few parts per million water; other is broad semi‐solid magnetization (MT) immobile associated with matrix kilohertz linewidths. Recently it was shown that CEST contrasts can be strongly affected MT background, so corrections needed to derive accurate estimates of...

Abstract In this study, we introduce a new method for amide proton transfer imaging based on chemical exchange rotation transfer. It avoids several artifacts that plague conventional saturation approaches by creating label and reference scans varying the irradiation pulse angle (π 2π radians) instead of frequency offset (3.5 −3.5 ppm). Specifically, analysis is sensitive to confounding contributions from magnetic field ( B 0 ) inhomogeneities and, more problematically, inherently asymmetric...

Accurate quantification of chemical exchange saturation transfer (CEST) effects, including dipole-dipole mediated relayed nuclear Overhauser enhancement (rNOE) transfer, is important for applications and studies molecular concentration rate (and thereby pH or temperature). Although several methods, such as Lorentzian difference (LD) analysis, multiple-pool fits, the three-point method, have been extensively used in preclinical clinical applications, accuracy these methods has not evaluated....

A temporal diffusion MRI spectroscopy based approach has been developed to quantify cancer cell size and density in vivo.A novel imaging microstructural parameters using limited spectrally edited (IMPULSED) method selects a specific spectral window for an accurate quantification of sizes ranging from 10 20 μm common solid tumors. In practice, it is achieved by combination single long time pulsed gradient spin echo (PGSE) three low-frequency oscillating (OGSE) acquisitions. To validate our...

There is a need to develop imaging methods sensitive axonal injury in multiple sclerosis (MS), given the prominent impact of pathology on disability and outcome. Advanced multi-compartmental diffusion models offer novel indices white matter microstructure. One such model, neurite orientation dispersion density (NODDI), morphology, providing apparent volume fractions axons (vin), isotropic water (viso) fibers about central axis (orientation index, ODI). NODDI has yet be studied for its...

Purpose A new approach has been developed to quantify cell sizes and intracellular volume fractions using temporal diffusion spectroscopy with diffusion‐weighted acquisitions. Methods Temporal spectra may be used characterize tissue microstructure by measuring the effects of restrictions over a range times. Oscillating gradients have previously probe variations on cellular subcellular scales, but their ability accurately measure larger than 10 μm is limited. By combining measurements made...

Purpose Cell size is a fundamental characteristic of all tissues, and changes in cell cancer reflect tumor status response to treatments, such as apoptosis cell‐cycle arrest. Unfortunately, can currently be obtained only by pathological evaluation tissue samples invasively. Previous imaging approaches are limited preclinical MRI scanners or require relatively long acquisition times that impractical for clinical imaging. There need develop cell‐size applications. Methods We propose clinically...

ABSTRACT Background MR cytometry is a class of diffusion‐MRI‐based methods that characterize tumor microstructures at the cellular level. It involves multicompartmental biophysical modeling multi‐b and multiple diffusion time data to generate microstructural parameters, which may improve differentiation benign malignant breast tumors. Purpose To implement imaging with transcytolemmal water exchange (JOINT EXCHANGE) differentiate tumors, compare classification efficacy IMPULSED, JOINT,...

Abstract Magnetic resonance imaging measurements of the apparent rate water diffusion in tumors are sensitive to variations tissue cellularity, which have been shown useful for characterizing and their responses treatments. However, because technical limitations on most MRI systems, conventional pulse gradient spin echo (PGSE) methods measure relatively long time scales, during molecules may encounter barriers at multiple spatial including those much greater than typical cell dimensions. As...

Several studies have shown strong correlations between myelin content and T1 within the brain, even suggested that can be used to estimate content. However, other micro-anatomical features such as compartment size are known affect longitudinal relaxation rates, similar effects in porous media.T1 measurements were compared with measured or otherwise published axon white matter tracts of rat spinal cord, human brain.In both ex vivo studies, present rate 1/T1 across regions cord nearly equal...

Purpose Chemical exchange saturation transfer effects at 2 ppm (CEST@2ppm) in brain have previously been interpreted as originating from creatine. However, protein guanidino amine protons may also contribute to CEST@2ppm. This study aims investigate the molecular origins and specificity of CEST@2ppm brain. Methods Two experiments were performed: (i) samples containing egg white albumin creatine dialyzed using a semipermeable membrane demonstrate that proteins can be separated by this method;...

Abstract Inversion recovery sequences that vary the inversion time ( t i ) have been employed to determine T 1 and, more recently, quantitative magnetization transfer parameters. Specifically, in previous work, pulse varied only while maintaining a constant delay d between repetitions. values were determined by fitting single exponential function, and parameters then biexponential function with an approximate solution. In current study, new protocols are employed, which both fit data minimal...

Purpose This study investigates amide proton transfer (APT) and nuclear overhauser enhancement (NOE) in phantoms 9L tumors rat brains at 9.4 Tesla, using a recently developed method that can isolate different contributions to exchange. Methods Chemical exchange rotation (CERT) was used quantify APT NOEs through subtraction of signals acquired two irradiation flip angles, but with the same average power. Results CERT separates quantifies specific NOE without contamination from other pools,...

Purpose To investigate the influence of transcytolemmal water exchange on estimates tissue microstructural parameters derived from diffusion MRI using conventional PGSE and IMPULSED methods. Methods Computer simulations were performed to incorporate a broad range intracellular life times τin (50–∞ ms), cell diameters d (5–15 μm), intrinsic coefficient Din (0.6–2 μm2/ms) for different values signal-to-noise ratio (SNR) (10 50). For experiments, murine erythroleukemia (MEL) cancer cells...

Purpose To detect, map, and quantify a novel nuclear Overhauser enhancement (NOE)-mediated magnetization transfer (MT) with water at approximately −1.6 ppm [NOE(−1.6)] in rat brain using MRI. Methods Continuous wave MT sequences variety of radiofrequency irradiation powers were optimized to achieve the maximum contrast this NOE(−1.6) effect 9.4 T. The distribution magnitudes, resonance frequency offsets, line widths healthy brains differences between tumors contralateral normal imaged...

Background Immune checkpoint inhibitors, the most widespread class of immunotherapies, have demonstrated unique response patterns that are not always adequately captured by traditional criteria such as Response Evaluation Criteria in Solid Tumors or even immune-specific criteria. These metrics rely on monitoring tumor growth, but an increase size and/or appearance after starting immunotherapy does represent progression, also can be a result T cell infiltration and thus positive treatment...

Background and Objectives: Current guidelines recommend contrast-enhanced CT/MRI as confirmatory imaging tests for diagnosing hepatocellular carcinoma (HCC). However, these modalities are not always able to differentiate HCC from benign/dysplastic nodules that commonly observed in cirrhotic livers. Consequently, many lesions require either pathological confirmation via invasive biopsy or surveillance after 3–6 months, which results delayed diagnosis treatment. We aimed develop noninvasive...

An improved finite difference (FD) method has been developed in order to calculate the behaviour of nuclear magnetic resonance signal variations caused by water diffusion biological tissues more accurately and efficiently. The algorithm converts conventional image-based into a convenient matrix-based approach includes revised periodic boundary condition which eliminates edge effects artificial boundaries FD methods. Simulated results for some modelled are consistent with analytical solutions...

Chemical exchange saturation transfer (CEST) potentially provides the ability to detect small solute pools through indirect measurements of attenuated water signals. However, CEST effects may be diluted by various competing effects, such as non‐specific magnetization (MT) and asymmetric MT longitudinal relaxation ( T 1 ) direct (radiofrequency spillover). In current study, images were acquired in rats following ischemic stroke analyzed comparing reciprocals signals at three different...