7 tesla imaging of cerebral radiation necrosis after arteriovenous malformations treatment using amide proton transfer (APT) imaging

Gerigk, Lars; Schmitt, Benjamin; Stieltjes, Bram; Röder, Falk; Essig, Marco; Bock, Michael; Schlemmer, Heinz Peter; Röthke, Matthias

doi:10.1002/jmri.23534

Cited by 16 publications

(12 citation statements)

References 13 publications

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Section: Amide Proton Transfermentioning

confidence: 99%

“…Future clinical studies of tumor imaging with APT MRI should take care to avoid misinterpreting cystic, necrotic, or hemorrhagic areas as viable tumor in APT MR images, because tumor necrosis and hemorrhage can also have higher mobile protein concentrations. 79 T 1 -and T 2weighted MRI scans are typically acquired before CEST scans to delineate these regions. Additionally, the T 1 relaxation time constant of gray matter is 60% longer than for white matter, which allows a stronger CEST effect to be generated in gray matter that can be misinterpreted as a stronger ATP MRI contrast associated with brain tumors.…”

Section: Apt Mri Of Solid Tumorsmentioning

confidence: 99%

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Clinical applications of chemical exchange saturation transfer (CEST) MRI

Jones

Pollard

Pagel

2017

Magnetic Resonance Imaging

231

246

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Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has been developed and employed in multiple clinical imaging research centers worldwide. Selective radiofrequency (RF) saturation pulses with standard 2D and 3D MRI acquisition schemes are now routinely performed, and CEST MRI can produce semiquantitative results using magnetization transfer ratio asymmetry (MTRasym) analysis while accounting for B0 inhomogeneity. Faster clinical CEST MRI acquisition methods and more quantitative acquisition and analysis routines are under development. Endogenous biomolecules with amide, amine, and hydroxyl groups have been detected during clinical CEST MRI studies, and exogenous CEST agents have also been administered to patients. These CEST MRI tools show promise for contributing to assessments of cerebral ischemia, neurological disorders, lymphedema, osteoarthritis, muscle physiology, and solid tumors. This review summarizes the salient features of clinical CEST MRI protocols and critically evaluates the utility of CEST MRI for these clinical imaging applications. Level of Evidence: 5 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:11–27.

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Section: Amide Proton Transfermentioning

confidence: 99%

Section: Apt Mri Of Solid Tumorsmentioning

confidence: 99%

Clinical applications of chemical exchange saturation transfer (CEST) MRI

Jones

Pollard

Pagel

2017

Magnetic Resonance Imaging

231

246

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“…CEST and SL experiments are commonly applied to enhance the NMR sensitivity of protons in dilute metabolites in vivo , yielding an imaging contrast for different pathologies . The normalized z magnetization after irradiation at different frequencies, the so‐called Z ‐spectrum, is affected by relaxation and irradiation parameters.…”

Section: Introductionmentioning

confidence: 99%

Exchange‐dependent relaxation in the rotating frame for slow and intermediate exchange – modeling off‐resonant spin‐lock and chemical exchange saturation transfer

2012

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Chemical exchange observed by NMR saturation transfer (CEST) and spin-lock (SL) experiments provide an MRI contrast by indirect detection of exchanging protons. The determination of the relative concentrations and exchange rates is commonly achieved by numerical integration of the Bloch-McConnell equations. We derive an analytical solution of the Bloch-McConnell equations that describes the magnetization of coupled spin populations under radiofrequency irradiation. As CEST and off-resonant SL are equivalent, their steady-state magnetization and dynamics can be predicted by the same single eigenvalue: the longitudinal relaxation rate in the rotating frame R1ρ . For the case of slowly exchanging systems, e.g. amide protons, the saturation of the small proton pool is affected by transverse relaxation (R2b ). It turns out, that R2b is also significant for intermediate exchange, such as amine- or hydroxyl-exchange or paramagnetic CEST agents, if pools are only partially saturated. We propose a solution for R1ρ that includes R2 of the exchanging pool by extending existing approaches, and verify it by numerical simulations. With the appropriate projection factors, we obtain an analytical solution for CEST and SL for nonzero R2 of the exchanging pool, exchange rates in the range 1-10(4) Hz, B1 from 0.1 to 20 μT and arbitrary chemical shift differences between the exchanging pools, whilst considering the dilution by direct water saturation across the entire Z-spectra. This allows the optimization of irradiation parameters and the quantification of pH-dependent exchange rates and metabolite concentrations. In addition, we propose evaluation methods that correct for concomitant direct saturation effects. It is shown that existing theoretical treatments for CEST are special cases of this approach.

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“…Finally, amide proton transfer imaging in 7 Tesla MRI maybe an alternative and possibly promising approach, first results concerning radionecrosis after AVM radiosurgery were recently published by Gerigk et al in 2012 [28], but the applied technology and the required MR equipment are highly challenging and available only to very few clinical centers, and its usefulness has still to be evaluated in larger patient samples.…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance spectroscopic study of radiogenic changes after radiosurgery of cerebral arteriovenous malformations with implications for the differential diagnosis of radionecrosis

et al. 2013

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BackgroundThe incidence of radionecrosis after radiosurgery is 5–20%. That radionecrosis after radiosurgery may be confused with a malignant tumor is a known phenomenon and problem.MethodsThree similarly treated patients with cAVM, 1 patient with symptomatic radionecrosis and 2 patients with normal post-radiation MRI changes, were selected and studied in detail with magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and magnetic resonance spectroscopy (MRS). 2 cAVM were located in eloquent locations and were classified as Spetzler-Martin grade (SM) III such that interdisciplinary radiosurgery was recommended; a third patient with a left frontal SM II cAVM refused surgery. 1 patient was male, and 2 were female. The patient’s ages ranged from 38 to 62 years (median, 39 years). The nidus volume (= planning target volume = PTV) ranged from 2.75 to 6.89 ccm (median, 6.41 ccm). The single dose was 20 Gy at the isocenter of the PTV encompassing the 80 – 90% isodose. The median follow-up period was 20 months (range, 16 – 84 months). Toxicities were evaluated with the Common Terminology Criteria (CTC) for adverse events version 3.0.ResultsNo patient suffered a bleeding from cAVM during the study period. A complete nidus occlusion was shown in all patients with time-resolved MRA. All patients showed radiogenic MRI changes, 1 patient showed excessive radionecrosis. This patient was oligosymptomatic and under temporary corticoid therapy symptoms resolved completely.Following patterns associated with radionecrosis in the MRS studies were identified in our collective:• 2D spectroscopic imaging (2D-SI) revealed much lower concentrations of metabolites in the lesion as compared to contralateral healthy tissue in all patients.• Whereas regions with regular post-radiosurgery effects showed almost normal levels of Cho and a Cho/Cr ratio < 2.0, regions with radionecrosis were characterized by increased lipid levels and a Cho/Cr ratio > 2.0 in conjunction with decreased absolute levels of all metabolites, especially of Cr and NAA.ConclusionsMRS is an increasingly valuable tool for the differential diagnosis of radiation reactions. Specific patterns of MRS spectra in radionecrosis were identified; in synopsis with clinical parameters, these changes have to be taken into account to avoid misdiagnosis.

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7 tesla imaging of cerebral radiation necrosis after arteriovenous malformations treatment using amide proton transfer (APT) imaging

Cited by 16 publications

References 13 publications

Clinical applications of chemical exchange saturation transfer (CEST) MRI

Clinical applications of chemical exchange saturation transfer (CEST) MRI

Exchange‐dependent relaxation in the rotating frame for slow and intermediate exchange – modeling off‐resonant spin‐lock and chemical exchange saturation transfer

Magnetic resonance spectroscopic study of radiogenic changes after radiosurgery of cerebral arteriovenous malformations with implications for the differential diagnosis of radionecrosis

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