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The complexity of modern in vivo magnetic resonance imaging (MRI) methods in oncology has dramatically changed in the last 10 years. The field has long since moved passed its (unparalleled) ability to form images with exquisite soft-tissue contrast and morphology, allowing for the enhanced identification of primary tumors and metastatic disease. Currently, it is not uncommon to acquire images related to blood flow, cellularity, and macromolecular content in the clinical setting. The acquisition of images related to metabolism, hypoxia, pH, and tissue stiffness are also becoming common. All of these techniques have had some component of their invention, development, refinement, validation, and initial applications in the preclinical setting using in vivo animal models of cancer. In this review, we discuss the genesis of quantitative MRI methods that have been successfully translated from preclinical research and developed into clinical applications. These include methods that interrogate perfusion, diffusion, pH, hypoxia, macromolecular content, and tissue mechanical properties for improving detection, staging, and response monitoring of cancer. For each of these techniques, we summarize the 1) underlying biological mechanism(s); 2) preclinical applications; 3) available repeatability and reproducibility data; 4) clinical applications; and 5) limitations of the technique. We conclude with a discussion of lessons learned from translating MRI methods from the preclinical to clinical setting, and a presentation of four fundamental problems in cancer imaging that, if solved, would result in a profound improvement in the lives of oncology patients. Level of Evidence: 5 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1377-1392.

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 to investigate the molecular origins and specificity of CEST@2ppm in brain.Two experiments were performed: (i) samples containing egg white albumin and creatine were dialyzed using a semipermeable membrane to demonstrate that proteins and creatine can be separated by this method; and (ii) tissue homogenates of rat brain with and without dialysis to remove creatine were studied to measure the relative contributions of proteins and creatine to CEST@2ppm.The experiments indicate that dialysis can successfully remove creatine from proteins. Measurements on tissue homogenates show that, with the removal of creatine via dialysis, CEST@2ppm decreases to approximately 34% of its value before dialysis, which indicates that proteins and creatine have comparable contribution to the CEST@2ppm in brain. However, considering the contribution from peptides and amino acids to CEST@2ppm, creatine may have much less contribution to CEST@2ppm.The contribution of proteins, peptides, and amino acids to CEST@2ppm cannot be neglected. The CEST@2ppm measurements of creatine in rat brain should be interpreted with caution. Magn Reson Med 78:881-887, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Corrosion perforation and scaling occur frequently in pipeline of Tuha oil field. After being exposed to crude oil in petroleum transmission pipeline for 120 days, corrosion rate of weight loss of the steel disc was calculated. Scanning Electron Microscope (SEM) was employed to observe the microscopic corrosion morphology of coupon, and the compositions of the oily water mixture and pipes were analyzed. The microstructure of the corrosion products and the reason of corrosion were investigated by Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD). The result showed that non-uniform corrosion occurred on the surface of coupon, and corrosion rate of weight loss was 0.187 mm/y The corrosion products was mainly ferrous sulfide (FeS) and silicon disulfide (SiS2), and the scaling was mainly calcium carbonate (CaCO3). The corrosion-cell reaction, calcium ion (Ca2+) and bicarbonate ion ( HCO 3 - ) in formation water, and sulfuretted hydrogen (H2S) were the major factors which caused pipeline corrosion and scaling. H2S and Ca2+ weakened carbon dioxide (CO2) corrosion of pipeline in oil–water mixture medium.

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.Continuous wave MT sequences with a variety of radiofrequency irradiation powers were optimized to achieve the maximum contrast of this NOE(-1.6) effect at 9.4 T. The distribution of effect magnitudes, resonance frequency offsets, and line widths in healthy rat brains and the differences of the effect between tumors and contralateral normal brains were imaged and quantified using a multi-Lorentzian fitting method. MR measurements on reconstituted model phospholipids as well as two cell lines (HEK293 and 9L) were also performed to investigate the possible molecular origin of this NOE.Our results suggest that the NOE(-1.6) effect can be detected reliably in rat brain. Pixel-wise fittings demonstrated the regional variations of the effect. Measurements in a rodent tumor model showed that the amplitude of NOE(-1.6) in brain tumor was significantly diminished compared with that in normal brain tissue. Measurements of reconstituted phospholipids suggest that this effect may originate from choline phospholipids.NOE(-1.6) could be used as a new biomarker for the detection of brain tumor. Magn Reson Med 78:588-597, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Off-resonant RF irradiation in tissue indirectly lowers the water signal by saturation transfer processes: on the one hand, there are selective chemical exchange saturation transfer (CEST) effects originating from exchanging endogenous protons resonating a few parts per million from water; on the other hand, there is the broad semi-solid magnetization transfer (MT) originating from immobile protons associated with the tissue matrix with kilohertz linewidths. Recently it was shown that endogenous CEST contrasts can be strongly affected by the MT background, so corrections are needed to derive accurate estimates of CEST effects. Herein we show that a full analytical solution of the underlying Bloch-McConnell equations for both MT and CEST provides insights into their interaction and suggests a simple means to isolate their effects. The presented analytical solution, based on the eigenspace solution of the Bloch-McConnell equations, extends previous treatments by allowing arbitrary lineshapes for the semi-solid MT effects and simultaneously describing multiple CEST pools in the presence of a large MT pool for arbitrary irradiation. The structure of the model indicates that semi-solid MT and CEST effects basically add up inversely in determining the steady-state Z-spectrum, as previously shown for direct saturation and CEST effects. Implications for existing previous CEST analyses in the presence of a semi-solid MT are studied and discussed. It turns out that, to accurately quantify CEST contrast, a good reference Z-value, the observed longitudinal relaxation rate of water, and the semi-solid MT pool size fraction must all be known.

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 transfer (MT) and asymmetric MT effects, water longitudinal relaxation (T1 ) and direct water saturation (radiofrequency spillover). In the current study, CEST images were acquired in rats following ischemic stroke and analyzed by comparing the reciprocals of the CEST signals at three different saturation offsets. This combined approach corrects the above competing effects and provides a more robust signal metric sensitive specifically to the proton exchange rate constant. The corrected amide proton transfer (APT) data show greater differences between the ischemic and contralateral (non-ischemic) hemispheres. By contrast, corrected nuclear Overhauser enhancements (NOEs) around -3.5 ppm from water change over time in both hemispheres, indicating whole-brain changes that have not been reported previously. This study may help us to better understand the contrast mechanisms of APT and NOE imaging in ischemic stroke, and may also establish a framework for future stroke measurements using CEST imaging with spillover, MT and T1 corrections.

In brain tumor dynamic susceptibility contrast (DSC)-MRI studies, multiecho acquisition methods are used to quantify the dynamic changes in T1 and T2 * that occur when contrast agent (CA) extravasates. Such methods also enable the estimation of the effective tissue CA transverse relaxivity. The goal of this study was to evaluate the sensitivity of the transverse relaxivity at tracer equilibrium (TRATE) to tumor cytoarchitecture.Computational and in vitro studies were used to evaluate the biophysical basis of TRATE. In 9L, C6, and human brain tumors, TRATE, the apparent diffusion coefficient (ADC), the CA transfer constant (K(trans) ), the extravascular extracellular volume fraction (ve ), and histological data were compared.Simulations and in vitro results indicate that TRATE is highly sensitive to variations in cellular properties such as cell size and density. The histologic cell density and TRATE values were significantly higher in 9L tumors as compared to C6 tumors. In animal and human tumors, a voxel-wise comparison of TRATE with ADC, ve , and K(trans) maps showed low spatial correlation.The assessment of TRATE is clinically feasible and its sensitivity to tissue cytoarchitectural features not present in other imaging methods indicate that it could potentially serve as a unique structural signature or "trait" of cancer.

Magnetization transfer (MT) provides an indirect means to detect noninvasively variations in macromolecular contents in biological tissues, but, so far, there have been only a few quantitative MT (qMT) studies reported in cancer, all of which used off-resonance pulsed saturation methods. This article describes the first implementation of a different qMT approach, selective inversion recovery (SIR), for the characterization of tumor in vivo using a rodent glioma model. The SIR method is an on-resonance method capable of fitting qMT parameters and T1 relaxation time simultaneously without mapping B0 and B1 , which is very suitable for high-field qMT measurements because of the lower saturation absorption rate. The results show that the average pool size ratio (PSR, the macromolecular pool versus the free water pool) in rat 9 L glioma (5.7%) is significantly lower than that in normal rat gray matter (9.2%) and white matter (17.4%), which suggests that PSR is potentially a sensitive imaging biomarker for the assessment of brain tumor. Despite being less robust, the estimated MT exchange rates also show clear differences from normal tissues (19.7 Hz for tumors versus 14.8 and 10.2 Hz for gray and white mater, respectively). In addition, the influence of confounding effects, e.g. B1 inhomogeneity, on qMT parameter estimates is investigated with numerical simulations. These findings not only help to better understand the changes in the macromolecular contents of tumors, but are also important for the interpretation of other imaging contrasts, such as chemical exchange saturation transfer of tumors.