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The high correlation between the introduced gagCEST method and (23)Na imaging implies that gagCEST is a potentially useful biomarker for glycosaminoglycans.

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Objective-The aim of this study was to compare quantitative and semiquantitative parameters (signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR], image quality, diagnostic confidence) from a standard brain magnetic resonance imaging examination encompassing common neurological disorders such as demyelinating disease, gliomas, cerebrovascular disease, and epilepsy, with comparable sequence protocols and acquisition times at 3 T and at 7 T.Materials and Methods-Ten healthy volunteers and 4 subgroups of 40 patients in total underwent comparable magnetic resonance protocols with standard diffusion-weighted imaging, 2D and 3D turbo spin echo, 2D and 3D gradient echo and susceptibility-weighted imaging of the brain (10 sequences) at 3 T and 7 T. The subgroups comprised patients with either lesional (n = 5) or nonlesional (n = 4) epilepsy, intracerebral tumors (n = 11), demyelinating disease (n = 11) (relapsing-remitting multiple sclerosis [MS, n = 9], secondary progressive MS [n = 1], demyelinating disease not further specified [n = 1]), or chronic cerebrovascular disorders [n = 9]). For quantitative analysis, SNR and CNR were determined. For a semiquantitative assessment of the diagnostic confidence, a 10-point scale diagnostic confidence score (DCS) was applied. Two experienced radiologists with additional qualification in neuroradiology independently assessed, blinded to the field strength, 3 pathology-specific imaging criteria in each of the 4 disease groups and rated their diagnostic confidence. The overall image quality was semiquantitatively assessed using a 4-point scale taking into account whether diagnostic decision making was hampered by artifacts or not.Results-Without correction for spatial resolution, SNR was higher at 3 T except in the T2 SPACE 3D, DWI single shot, and DIR SPACE 3D sequences. The SNR corrected by the ratio of 3Correspondence to: Siegfried Trattnig, MD, High Field MR Center, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Waerhringer Guertel 18-20, A-1090 Vienna, Austria. siegfried.trattnig@meduniwien.ac.at. Conflicts of interestThe authors report no conflicts of interest. Europe PMC Funders Group Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts T/7 T voxel sizes was higher at 7 T than at 3 T in 10 of 11 sequences (all except for T1 MP2RAGE 3D).In CNR, there was a wide variation between sequences and patient cohorts, but average CNR values were broadly similar at 3 T and 7 T.DCS values for all 4 pathologic entities were higher at 7 T than at 3 T. The DCS was significantly higher at 7 T for diagnosis and exclusion of cortical lesions in vascular disease. A tendency to higher DCS at 7 T for cortical lesions in MS was observed, and for the depiction of a central vein and iron deposits within MS lesions. Despite motion artifacts, DCS values were higher at 7 T for the diagnosis and exclusion of hippocampal sclerosis in mesial temporal lobe epilepsy (improved detection of the hippocampal subunits). Interrater ag...

Long-term clinical outcome in patients 7.9 years after AOT was good, but did not correlate with morphological and biochemical imaging results except for T2-mapping.

CEST is able to detect normal and damaged cartilage and is non-inferior in distinguishing both when compared to dGEMRIC and T2 mapping.

Chemical exchange saturation transfer (CEST) imaging depends on the performance of radiofrequency saturation during the experiment. Scanner specifications, in particular limited pulse width and duty-cycle, and specific absorption rate guidelines restrict the full exploitation of CEST effects in clinical MR systems. The purpose of this study was to optimize techniques for effective pulse train presaturation for CEST imaging in a whole-body MR scanner. Theoretical analysis and simulations of the spectral properties of radiofrequency pulse trains demonstrated the significance of pulse width t P and interpulse delay t D for effective and selective labeling of a chemically exchanging proton pool. CEST experiments with model solutions, e.g., creatine dissolved in water, showed best performance of pulse trains with t P 5 t D 5 100 msec, regarding minimum direct water saturation in z-spectra and distinct magnetization transfer ratio asymmetry that can be determined quantitatively. Saturation efficiency of trains of Gaussian-shaped radiofrequency pulses using this timing was evaluated in MR imagers with field strengths of 1.5, 3, and 7 T. The proposed saturation pulse train does not require hardware modifications, offers low specific absorption rate, and can be used in a standard clinical setup. Magn Reson Med 65:1620-1629, 2011. V C 2011 Wiley-Liss, Inc.Key words: CEST imaging; pulse train; selective spin labeling; clinical MR scanner Successful saturation transfer experiments crucially depend on the efficient irradiation of radiofrequency (RF) energy into a specific frequency range. After saturation of one spin species, magnetic interaction with another spin species causes detectable magnetization transfer (MT) between these two spin species. It is widely accepted that MT in aqueous solvents occurs due to dipole-dipole interactions as well as chemical exchange of protons, both of which can mediate cross relaxation between different spin systems.In conventional MT-based magnetic resonance imaging (MRI) in biological tissues, MT mainly involves the interaction between protons at the surface of slowly tumbling macromolecules and protons of bulk water molecules (1). In the following, this effect will be called ''conventional MT.'' Another class of MT experiments that exclusively exploits chemical exchange between protons of mobile solute molecules and the surrounding bulk water was dubbed chemical exchange saturation transfer (CEST) (2-4). In conventional MT, the resonances of macromolecular protons exhibit linewidths in the order of 1-100 kHz. This is different from CEST experiments with endogenous or diamagnetic contrast agents, where the linewidths of 1 H in mobile compounds are similar to that of bulk water protons, namely a few to tens of Hz. This property implies different experimental conditions compared to conventional MT although the fundamental physical principles in both techniques are similar: Concomitant direct saturation effects on water protons during off-resonant irradiation-called spillover or RFbleeding e...

Amide proton transfer (APT) magnetic resonance imaging is gaining attention for its capability for grading glial tumors. Usually, a representative slice is analyzed. Different definitions of tumor areas have been employed in previous studies. We hypothesized that the accuracy of APT imaging for brain tumor grading may depend upon the analytical methodology used, such as selection of regions of interest (ROIs), single or multiple tumor slices, and whether or not there is normalization to the contralateral white matter. This study was approved by the institutional review board, and written informed consent was waived. Twenty-six patients with histologically proven glial tumors underwent preoperative APT imaging with a three-dimensional gradient-echo sequence. Two neuroradiologists independently analyzed APT asymmetry (APTasym) images by placing ROIs on both a single representative slice (RS) and all slices including tumor (i.e. whole tumor: WT). ROIs indicating tumor extent were separately defined on both FLAIR and, if applicable, contrast-enhanced T1-weighted images (CE-T1WI), yielding four mean APTasym values (RS-FLAIR, WT-FLAIR, RS-CE-T1WI, and WT-CE-T1WI). The maximum values were also measured using small ROIs, and their differences among grades were evaluated. Receiver operating characteristic (ROC) curve analysis was also conducted on mean and maximum values. Intra-class correlation coefficients for inter-observer agreement were excellent. Significant differences were observed between high- and low-grade gliomas for all five methods (P < 0.01). ROC curve analysis found no statistically significant difference among them. This study clarifies that single-slice APT analysis is robust despite tumor heterogeneity, and can grade glial tumors with or without the use of contrast material.