Measurement of regional brain temperature using proton spectroscopic imaging: validation and application to acute ischemic stroke

Marshall, Ian; Karaszewski, Bartosz; Wardlaw, Joanna M.; Cvoro, Vera; Wartolowska, Karolina; Armitage, Paul A.; Carpenter, Trevor; Bastin, Mark E.; Farrall, Andrew; Haga, Kristin

doi:10.1016/j.mri.2006.02.002

Cited by 78 publications

(94 citation statements)

References 27 publications

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“…Temperature changes due to metabolic activity (24)(25)(26), motion of water molecules associated with ion flux across the cell membrane during activation, increased water content inside the neurons (cell swelling), or physical motion induced by the changes in cellular volume (27)(28)(29)(30) all could be factors in the signal changes.…”

Section: Discussionmentioning

confidence: 99%

Direct magnetic resonance detection of neuronal electrical activity

Petridou

Plenz²,

Silva

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

100

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Present noninvasive neuroimaging methods measure neuronal activity indirectly, via either cerebrovascular changes or extracranial measurements of electrical͞magnetic signals. Recent studies have shown evidence that MRI may be used to directly and noninvasively map electrical activity associated with human brain activation, but results are inconclusive. Here, we show that MRI can detect cortical electrical activity directly. We use organotypic ratbrain cultures in vitro that are spontaneously active in the absence of a cerebrovascular system. Single-voxel magnetic resonance (MR) measurements obtained at 7 T were highly correlated with multisite extracellular local field potential recordings of the same cultures before and after blockade of neuronal activity with tetrodotoxin. Similarly, for MR images obtained at 3 T, the MR signal changed solely in voxels containing the culture, thus allowing the spatial localization of the active neuronal tissue.cell culture ͉ functional MRI ͉ neuronal current imaging ͉ brain P resent noninvasive neuroimaging methods have provided a wealth of information regarding the dynamic spatial and temporal organization of the brain. Limitations nevertheless remain. Electroencephalography (EEG) and magnetoencephalography (MEG) measure electromagnetic neuronal activity on the surface of the scalp with millisecond temporal resolution but limited spatial resolution and certainty of activation location (1-4). Functional MRI (fMRI) methods measure localized changes of blood flow, blood volume, and͞or blood oxygenation that occur with increased neuronal activation. The spatial (1.5-3 mm) and temporal resolution (1 s) of functional MRI is limited by variations in the vasculature and the neuronal-hemodynamic coupling (5). Significant effort has been made, with limited success, to combine information from these different methods to obtain more accurate maps of brain activation (4, 6).The work presented here presents evidence that magnetic resonance (MR) can detect changes in magnetic field, not related to hemodynamic changes but induced by neuronal electrical activity. The MR signal originates from protons precessing at a given frequency that is proportional to the magnetic field that they are experiencing. Ionic currents, on the order of a few nanoamperes, that are associated with synaptic and suprathreshold activity result in weak magnetic fields. These fields alter the precession frequency of the surrounding protons and, therefore, may create a small change in the measured MR phase and͞or MR magnitude signal. Magnitude changes are caused by a destructive addition of multiple different frequency offsets within a voxel. Phase changes are measurable if a substantial proportion of protons in a voxel have the same frequency offset.MR imaging of weak magnetic field changes has been demonstrated in phantoms (7-11), in snail ganglia (12, 13), and in the human body by using experimentally applied current (14). Although not conclusive, reports of using MRI to detect neuronal activity-based signal changes ...

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Section: Discussionmentioning

confidence: 99%

Direct magnetic resonance detection of neuronal electrical activity

Petridou

Plenz²,

Silva

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

100

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“…Details of the acquisition parameters and data processing methods have been published previously. 4 The brain slice from the averaged diffusion-weighted image volume on which the MR spectroscopic volume-of-interest had been placed was windowed on a fixed signal intensity to optimize diffusion signal contrast between normal and abnormal tissue. A voxel grid (5ϫ5 voxels or 4.7ϫ4.7 mm) was superimposed over the image ( Figure 1A) and a neuroradiologist blinded to all other data classified each voxel as abnormal or normal tissue according to its appearance on the first scan (averaged diffusion-weighted image).…”

Section: Methodsmentioning

confidence: 99%

Choline and Creatine Are Not Reliable Denominators for Calculating Metabolite Ratios in Acute Ischemic Stroke

Maniega

Cvoro

Armitage

et al. 2008

Stroke

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Background and Purpose-Choline and creatine are commonly used as denominators for other metabolites in ischemic stroke spectroscopy, assuming that they do not change. We investigated their concentration variation over time after stroke. Methods-Choline and creatine concentrations were measured by proton MR spectroscopic imaging in 51 patients at 5 times up to 3 months after stroke. Results-Choline and creatine levels changed significantly in the ischemic region. Choline was significantly reduced during the first 2 weeks after stroke onset (Pϭ0.034). Creatine was significantly reduced during the whole period of the study (Pϭ0.011). Conclusion-Choline and creatine concentrations are not reliable denominators for metabolite ratios in acute stroke because their levels vary significantly in ischemic brain regions.

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“…The shift is measured between the water peak and a reference peak that remains constant with temperature, such as lipids (48) or N-acetyl-aspartate in the brain (49). This internal reference makes spectroscopic methods relatively immune to field drifts and interscan motion and allows for absolute temperature measurements (49), which have been demonstrated in the human brain (50).…”

Section: Spectroscopic Imaging Using the Prf Shiftmentioning

confidence: 99%

MR thermometry

Rieke

Pauly

2008

Magnetic Resonance Imaging

1,022

952

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Minimally invasive thermal therapy as local treatment of benign and malignant diseases has received increasing interest in recent years. Safety and efficacy of the treatment require accurate temperature measurement throughout the thermal procedure. Noninvasive temperature monitoring is feasible with magnetic resonance (MR) imaging based on temperature-sensitive MR parameters such as the proton resonance frequency (PRF), the diffusion coefficient (D), T 1 and T 2 relaxation times, magnetization transfer, the proton density, as well as temperature-sensitive contrast agents. In this article the principles of temperature measurements with these methods are reviewed and their usefulness for monitoring in vivo procedures is discussed. Whereas most measurements give a temperature change relative to a baseline condition, temperature-sensitive contrast agents and spectroscopic imaging can provide absolute temperature measurements. The excellent linearity and temperature dependence of the PRF and its near independence of tissue type have made PRF-based phase mapping methods the preferred choice for many in vivo applications. Accelerated MRI imaging techniques for real-time monitoring with the PRF method are discussed. Special attention is paid to acquisition and reconstruction methods for reducing temperature measurement artifacts introduced by tissue motion, which is often unavoidable during in vivo applications.

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Measurement of regional brain temperature using proton spectroscopic imaging: validation and application to acute ischemic stroke

Cited by 78 publications

References 27 publications

Direct magnetic resonance detection of neuronal electrical activity

Direct magnetic resonance detection of neuronal electrical activity

Choline and Creatine Are Not Reliable Denominators for Calculating Metabolite Ratios in Acute Ischemic Stroke

MR thermometry

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