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https://www.readbyqxmd.com/read/28096269/differentiation-between-radiation-necrosis-and-tumor-progression-using-chemical-exchange-saturation-transfer
#1
Hatef Mehrabian, Kimberly L Desmond, Hany Soliman, Arjun Sahgal, Gregory J Stanisz
PURPOSE: Stereotactic radiosurgery (SRS) is a common treatment used in patients with brain metastases and is associated with high rates of local control, however, at the risk of radiation necrosis. It is difficult to differentiate radiation necrosis from tumor progression using conventional MRI making it a major diagnostic dilemma for practitioners. This prospective study investigated whether chemical exchange saturation transfer (CEST) was able to differentiate these two conditions. MATERIALS & METHODS: Fifteen patients with brain metastases who had been previously treated with SRS were included...
January 17, 2017: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
https://www.readbyqxmd.com/read/28075559/one-component-supramolecular-filament-hydrogels-as-theranostic-label-free-magnetic-resonance-imaging-agents
#2
Lye Lin Lock, Yuguo Li, Xinpei Mao, Hanwei Chen, Verena Staedtke, Renyuan Bai, Wang Ma, Ran Lin, Yi Li, Guanshu Liu, Honggang Cui
Gadolinium (Gd)-based compounds and materials are the most commonly used magnetic resonance imaging (MRI) contrast agents in the clinic; however, safety concerns associated with their toxicities in the free ionic form have promoted the development of new generations of metal-free contrast agents. Here we report a supramolecular strategy to convert an FDA-approved anticancer drug, Pemetrexed (Pem), to a molecular hydrogelator with inherent chemical exchange saturation transfer (CEST) MRI signals. The rationally designed drug-peptide conjugate can spontaneously associate into filamentous assemblies under physiological conditions and consequently form theranostic supramolecular hydrogels for injectable delivery...
January 11, 2017: ACS Nano
https://www.readbyqxmd.com/read/28035783/separating-dipolar-and-chemical-exchange-magnetization-transfer-processes-in-1-h-cest
#3
Tairan Yuwen, Ashok Sekhar, Lewis E Kay
An amide (1) H-Chemical Exchange Saturation Transfer (CEST) experiment is presented for studies of conformational exchange in proteins. The approach, exploiting spin-state-selective magnetization transfer, completely suppresses undesired NOE-based dips in CEST profiles so that chemical exchange processes can be studied. The methodology is demonstrated with applications involving proteins that interconvert on the millisecond timescale between major and invisible minor states, and accurate amide (1) H chemical shifts of the minor conformer are obtained in each case...
December 30, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/28012297/balanced-steady-state-free-precession-bssfp-from-an-effective-field-perspective-application-to-the-detection-of-chemical-exchange-bssfpx
#4
Shu Zhang, Zheng Liu, Aaron Grant, Jochen Keupp, Robert E Lenkinski, Elena Vinogradov
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence...
December 8, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27987233/imaging-extracellular-lactate-in-vitro-and-in-vivo-using-cest-mri-and-a-paramagnetic-shift-reagent
#5
Dean Sherry, Lei Zhang, Andre Martins, Yuyan Mai, Piyu Zhao, Alexander Funk, Veronica Jordan, Shanrong Zhang, Wei Chen, Yunkou Wu
Overproduction of lactate is a hallmark of cancer yet a method to quantitatively measure lactate production by cancer cells is not straight-forward. CEST MRI can potentially be used to image lactate but the small difference in chemical shifts of the lactate -OH proton and water proton resonances make it challenging. Like other spectroscopic methods, CEST MRI cannot discriminate intracellular lactate from extracellular lactate. Here, we demonstrate a relatively simple way to shift of the lactate -OH proton resonance far away from water by addition of the paramagnetic shift reagent, EuDO3A, while retaining the CEST properties of lactate itself...
December 17, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27980128/nor-sass-norwegian-sonothrombolysis-in-acute-stroke-study-randomized-controlled-contrast-enhanced-sonothrombolysis-in-an-unselected-acute-ischemic-stroke-population
#6
Aliona Nacu, Christopher E Kvistad, Halvor Naess, Halvor Øygarden, Nicola Logallo, Jörg Assmus, Ulrike Waje-Andreassen, Kathinka D Kurz, Gesche Neckelmann, Lars Thomassen
BACKGROUND AND PURPOSE: The NOR-SASS (Norwegian Sonothrombolysis in Acute Stroke Study) aimed to assess effect and safety of contrast-enhanced ultrasound treatment in an unselected acute ischemic stroke population. METHODS: Patients treated with intravenous thrombolysis within 4.5 hours after symptom onset were randomized 1:1 to either contrast-enhanced sonothrombolysis (CEST) or sham CEST. A visible arterial occlusion on baseline computed tomography angiography was not a prerequisite for inclusion...
December 15, 2016: Stroke; a Journal of Cerebral Circulation
https://www.readbyqxmd.com/read/27966496/recent-excitements-in-protein-nmr-large-proteins-and-biologically-relevant-dynamics
#7
Sai Chaitanya Chiliveri, Mandar V Deshmukh
The advent of Transverse Relaxation Optimized SpectroscopY (TROSY) and perdeuteration allowed biomolecular NMR spectroscopists to overcome the size limitation barrier (approx. 20 kDa) in de novo structure determination of proteins. The utility of these techniques was immediately demonstrated on large proteins and protein complexes (e.g. GroELGroES, ClpP protease, Hsp90-p53, 20S proteasome, etc.). Further, recent methodological developments such as Residual Dipolar Couplings and Paramagnetic Relaxation Enhancement allowed accurate measurement of long-range structural restraints...
December 2016: Journal of Biosciences
https://www.readbyqxmd.com/read/27934305/gear-up-for-a-ph-shift-a-responsive-iron-ii-2-amino-6-picolyl-appended-macrocyclic-paracest-agent-that-protonates-at-a-pendent-group
#8
Pavel B Tsitovich, Jordan M Cox, Joseph A Spernyak, Janet R Morrow
Two high-spin Fe(II) and Co(II) complexes of 1,4,7,10-tetraazacyclododecane (CYCLEN) appended with four 2-amino-6-picolyl groups, denoted as [Fe(TAPC)](2+) and [Co(TAPC)](2+), are reported. These complexes demonstrate C2-symmetrical geometry from coordination of two pendents, and they are present in a single diastereomeric form in aqueous solution as shown by (1)H NMR spectroscopy and by a single-crystal X-ray structure for the Co(II) complex. A highly shifted but low-intensity CEST (chemical exchange saturation transfer) signal from NH groups is observed at -118 ppm for [Co(TAPC)](2+) at pH 6...
November 21, 2016: Inorganic Chemistry
https://www.readbyqxmd.com/read/27898185/perfusion-has-no-effect-on-the-in-vivo-cest-effect-from-cr-crcest-in-skeletal-muscle
#9
Feliks Kogan, Randall B Stafford, Erin K Englund, Garry E Gold, Hari Hariharan, John A Detre, Ravinder Reddy
Creatine, a key component of muscle energy metabolism, exhibits a chemical exchange saturation transfer (CEST) effect between its amine group and bulk water, which has been exploited to spatially and temporally map creatine changes in skeletal muscle before and after exercise. In addition, exercise leads to an increase in muscle perfusion. In this work, we determined the effects of perfused blood on the CEST effects from creatine in skeletal muscle. Experiments were performed on healthy human subjects (n = 5) on a whole-body Siemens 7T magnetic resonance imaging (MRI) scanner with a 28-channel radiofrequency (RF) coil...
January 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/27896628/clinical-translation-of-tumor-acidosis-measurements-with-acidocest-mri
#10
Kyle M Jones, Edward A Randtke, Eriko S Yoshimaru, Christine M Howison, Pavani Chalasani, Robert R Klein, Setsuko K Chambers, Phillip H Kuo, Mark D Pagel
PURPOSE: We optimized acido-chemical exchange saturation transfer (acidoCEST) magnetic resonance imaging (MRI), a method that measures extracellular pH (pHe), and translated this method to the radiology clinic to evaluate tumor acidosis. PROCEDURES: A CEST-FISP MRI protocol was used to image a flank SKOV3 tumor model. Bloch fitting modified to include the direct estimation of pH was developed to generate parametric maps of tumor pHe in the SKOV3 tumor model, a patient with high-grade invasive ductal carcinoma, and a patient with metastatic ovarian cancer...
November 28, 2016: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/27888530/perturbation-of-longitudinal-relaxation-rate-in-rotating-frame-plrf-analysis-for-quantification-of-chemical-exchange-saturation-transfer-signal-in-a-transient-state
#11
Yi Wang, Yaoyu Zhang, Xuna Zhao, Bing Wu, Jia-Hong Gao
PURPOSE: To develop a novel analytical method for quantification of chemical exchange saturation transfer (CEST) in the transient state. The proposed method aims to reduce the effects of non-chemical-exchange (non-CE) parameters on the CEST signal, emphasizing the effect of chemical exchange. METHODS: The difference in the longitudinal relaxation rate in the rotating frame ( ΔR1ρ) was calculated based on perturbation of the Z-value by R1ρ, and a saturation-pulse-amplitude-compensated exchange-dependent relaxation rate (SPACER) was determined with a high-exchange-rate approximation...
November 25, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/27866072/general-expressions-for-r1%C3%AF-relaxation-for-n-site-chemical-exchange-and-the-special-case-of-linear-chains
#12
Hans Koss, Mark Rance, Arthur G Palmer
Exploration of dynamic processes in proteins and nucleic acids by spin-locking NMR experiments has been facilitated by the development of theoretical expressions for the R1ρ relaxation rate constant covering a variety of kinetic situations. Herein, we present a generalized approximation to the chemical exchange, Rex, component of R1ρ for arbitrary kinetic schemes, assuming the presence of a dominant major site population, derived from the negative reciprocal trace of the inverse Bloch-McConnell evolution matrix...
January 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27859838/aggregation-induced-changes-in-the-chemical-exchange-saturation-transfer-cest-signals-of-proteins
#13
Steffen Goerke, Katharina S Milde, Raul Bukowiecki, Patrick Kunz, Karel D Klika, Thomas Wiglenda, Axel Mogk, Erich E Wanker, Bernd Bukau, Mark E Ladd, Peter Bachert, Moritz Zaiss
Chemical exchange saturation transfer (CEST) is an MRI technique that allows mapping of biomolecules (small metabolites, proteins) with nearly the sensitivity of conventional water proton MRI. In living organisms, several tissue-specific CEST effects have been observed and successfully applied to diagnostic imaging. In these studies, particularly the signals of proteins showed a distinct correlation with pathological changes. However, as CEST effects depend on various properties that determine and affect the chemical exchange processes, the origins of the observed signal changes remain to be understood...
January 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/27816001/diamagnetic-chemical-exchange-saturation-transfer-diacest-affords-magnetic-resonance-imaging-of-extracellular-matrix-hydrogel-implantation-in-a-rat-model-of-stroke
#14
Tao Jin, Francesca J Nicholls, William R Crum, Harmanvir Ghuman, Stephen F Badylak, Michel Modo
Extracellular matrix (ECM) is widely used as an inductive biological scaffold to repair soft tissue after injury by promoting functional site-appropriate remodeling of the implanted material. However, there is a lack of non-invasive analysis methods to monitor the remodeling characteristics of the ECM material after implantation and its biodegradation over time. We describe the use of diamagnetic chemical exchange saturation transfer (CEST) magnetic resonance imaging to monitor the distribution of an ECM hydrogel after intracerebral implantation into a stroke cavity...
January 2017: Biomaterials
https://www.readbyqxmd.com/read/27805423/the-potential-of-multiparametric-mri-of-the-breast
#15
Katja Pinker, Thomas H Helbich, Elizabeth A Morris
MRI is an essential tool in breast imaging, with multiple established indications. Dynamic contrast-enhanced MRI (DCE-MRI) is the backbone of any breast MRI protocol and has an excellent sensitivity and good specificity for breast cancer diagnosis. DCE-MRI provides high-resolution morphological information, as well as some functional information about neoangiogenesis as a tumour-specific feature. To overcome limitations in specificity, several other functional MRI parameters have been investigated and the application of these combined parameters is defined as multiparametric MRI (mpMRI) of the breast...
January 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/27748713/cellular-and-molecular-imaging-using-chemical-exchange-saturation-transfer
#16
Michael T McMahon, Assaf A Gilad
Chemical exchange saturation transfer (CEST) is a powerful new tool well suited for molecular imaging. This technology enables the detection of low concentration probes through selective labeling of rapidly exchanging protons or other spins on the probes. In this review, we will highlight the unique features of CEST imaging technology and describe the different types of CEST agents that are suited for molecular imaging studies, including CEST theranostic agents, CEST reporter genes, and CEST environmental sensors...
October 2016: Topics in Magnetic Resonance Imaging: TMRI
https://www.readbyqxmd.com/read/27717216/simulation-phantom-validation-and-clinical-evaluation-of-fast-ph-weighted-molecular-imaging-using-amine-chemical-exchange-saturation-transfer-echo-planar-imaging-cest-epi-in-glioma-at-3%C3%A2-t
#17
Robert J Harris, Timothy F Cloughesy, Linda M Liau, Phioanh L Nghiemphu, Albert Lai, Whitney B Pope, Benjamin M Ellingson
Acidity within the extracellular milieu is a hallmark of cancer. There is a current need for fast, high spatial resolution pH imaging techniques for clinical evaluation of cancers, including gliomas. Chemical exchange saturation transfer (CEST) MRI targeting fast-exchanging amine protons can be used to obtain high-resolution pH-weighted images, but conventional CEST acquisition strategies are slow. There is also a need for more accurate MR simulations to better understand the effects of amine CEST pulse sequence parameters on pH-weighted image contrast...
November 2016: NMR in Biomedicine
https://www.readbyqxmd.com/read/27711138/a-potential-magnetic-resonance-imaging-technique-based-on-chemical-exchange-saturation-transfer-for-in-vivo-%C3%AE-aminobutyric-acid-imaging
#18
Gen Yan, Tao Zhang, Zhuozhi Dai, Meizhi Yi, Yanlong Jia, Tingting Nie, Handi Zhang, Gang Xiao, Renhua Wu
PURPOSE: We developed a novel magnetic resonance imaging (MRI) technique based on chemical exchange saturation transfer (CEST) for GABA imaging and investigated the concentration-dependent CEST effect ofGABA in a rat model of brain tumor with blood-brain barrier (BBB) disruption. MATERIALS AND METHODS: All MRI studies were performed using a 7.0-T Agilent MRI scanner. Z-spectra for GABA were acquired at 7.0 T, 37°C, and a pH of 7.0 using varying B1 amplitudes. CEST images of phantoms with different concentrations of GABA solutions (pH, 7...
2016: PloS One
https://www.readbyqxmd.com/read/27709896/fast-tissue-characterization-with-quantitative-high-resolution-magic-angle-spinning-hrmas-cest-z-spectroscopy
#19
Iris Yuwen Zhou, Taylor L Fuss, Takahiro Igarashi, Weiping Jiang, Xin Zhou, Leo L Cheng, Phillip Zhe Sun
Chemical exchange saturation transfer (CEST) provides sensitive MR contrast for probing dilute compounds via exchangeable protons, serving as an emerging molecular imaging methodology. CEST Z-spectrum is often acquired by sweeping radiofrequency saturation around bulk water resonance, offset by offset, to detect CEST effects at characteristic chemical shift offsets, which requires prolonged acquisition time. Herein, combining high-resolution magic angle spinning (HRMAS) with concurrent application of gradient and RF saturation to achieve fast Z-spectral acquisition, we demonstrated the feasibility of fast quantitative HRMAS CEST Z-spectroscopy...
October 6, 2016: Analytical Chemistry
https://www.readbyqxmd.com/read/27690156/chemical-exchange-saturation-transfer-for-predicting-response-to-stereotactic-radiosurgery-in-human-brain-metastasis
#20
Kimberly L Desmond, Hatef Mehrabian, Sofia Chavez, Arjun Sahgal, Hany Soliman, Radoslaw Rola, Greg J Stanisz
PURPOSE: The purpose of this work was to determine the predictive value of chemical exchange saturation transfer (CEST) metrics in brain metastases treated with stereotactic radiosurgery (SRS). METHODS: CEST spectra at a radiofrequency power of 0.52 µT were collected on a 3 Tesla (T) magnetic resonance imaging from 25 patients at three time points: pretreatment, 1 week, and 1 month post-treatment. Amide proton transfer-weighted images and maps of the amplitude and width of Lorentzian-shaped CEST peaks and the relaxation-compensated AREX metric were constructed at the offset frequencies of amide, amine, and relayed nuclear Overhauser effect (NOE) from aliphatic groups as well as the broad magnetization transfer effect...
September 30, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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