High resolution MRI and MRS: A feasibility study for the investigation of focal cerebral ischemia in mice

Hesselbarth, Daniel; Franke, Claudia; Hata, Ryuji; Brinker, Gerrit; Hoehn‐Berlage, Mathias

doi:10.1002/(sici)1099-1492(199812)11:8<423::aid-nbm538>3.0.co;2-v

Cited by 42 publications

(39 citation statements)

References 16 publications

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“…In some experiments, no lesion was apparent in T 2 -weighted imaging before reperfusion (12). In others, both early T 2 decrease and later T 2 increase were observed after transient MCAO in rats (11,24) and permanent MCAO in rats (15) and mice (25). In the transient MCAO model, full recovery of ADC to preocclusion levels usually occurs after 30 -60 min of reperfusion if occlusion time is less than 30 min; partial recovery is expected if occlusion time does not exceed 90 min, and no recovery until 2-7 d with longer occlusion times (9,11,12,24).…”

mentioning

confidence: 99%

ADC characterization of region‐specific response to cerebral perfusion deficit in rats by MRI at 9.4 T

Yushmanov

Wang

Liachenko

et al. 2002

Magnetic Resonance in Med

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Region-specific cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) of water in the rat brain were quantified in vivo by high-field MRI (9.4 T) for 6 -7 h after middle cerebral artery occlusion (MCAO). Upon occlusion, average CBF fell from about 1.5-2 ml/g/min to below 0.5 ml/g/min in cortical areas and the amygdala, and below 0. The apparent diffusion coefficient (ADC) of water, which is measurable noninvasively by MRI, has been proposed as a reliable parameter for early detection of brain ischemia (1-3). ADC was shown to be sensitive to acute ischemia within minutes of occurrence (4). Currently, the intraluminal thread model of middle cerebral artery occlusion (MCAO) in rats (5-7) is generally accepted as a standard model of focal cerebral ischemia. In this model, cerebral blood flow (CBF) measurements are usually carried out to determine adequate occlusion (in both permanent and transient MCAO models) and reperfusion (in the transient model) (8 -14). When describing quantitative changes in cerebral perfusion and ADC values, data are usually reported as averages over 1) very small local regions (of several pixels in size) inside the involved brain structures (9,11), or 2) the whole lesion region, with reference to the symmetric contralateral region or to the whole contralateral hemisphere (12,15).In perfusion and ADC studies with the MCAO model in rats, two issues deserve further elaboration. First, the detailed regional dynamics of ADC and CBF, averaged over specific macroscopic brain regions, remains for the most part unexplored. Second, variability in experimental approaches and animals used in the studies results in a certain diversity of experimental findings. Even more important is that the definition of occlusion based on perfusion measurements is not always sufficiently rigorous, and may lead to different cellular responses in the occluded area. To characterize ischemic damage more quantitatively, stringent criteria are needed. An ADC-based definition of occlusion appears to be more adequate, since it is associated with cellular response to ischemia. This feature also makes ADC a suitable candidate for clinical use.CBF measurements are usually performed by laser-Doppler flowmetry (8,14,16) or perfusion-weighted magnetic resonance imaging (MRI). Qualitative perfusion-weighted images may be produced using paramagnetic contrast agents and echo-planar imaging (EPI) (bolus-tracking), and relative CBF indexes may be obtained (11-13). An alternative technique has been developed that uses arterial spin tagging and thus does not need any exogenous contrast agents (17). The arterial spin tagging technique was shown to be suitable for noninvasive quantitative measurements of CBF (17)(18)(19). MRI at high magnetic field (7 T and above) ensures better sensitivity in perfusion measurements (20). The variability in magnetic fields, however, may contribute to lower consistency in results obtained, especially when the difference in magnetic relaxation times is concerned.Variability in animal responses to...

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confidence: 99%

ADC characterization of region‐specific response to cerebral perfusion deficit in rats by MRI at 9.4 T

Yushmanov

Wang

Liachenko

et al. 2002

Magnetic Resonance in Med

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“…Newer techniques include the use of diffusion and perfusion imaging, also MRS for determining certain metabolites. 62,63 Many groups have used experimental MCA ligation combined with hypoxia in rats or mice as models for human stroke. 64 DWI sequences are especially powerful in detecting early ischemia, and many studies have used this resource in animal imaging, along with perfusion studies that are capable of visualizing the penumbra-the area at risk for infarction that potentially can be salvaged (FIG.…”

Section: Figmentioning

confidence: 90%

“…MRS studies have also been conducted, mainly looking at the lactate peak, which becomes prominent when anaerobic glycolysis predominates. 62,63,66 Another important aspect is the NAA peak that may show decrease in completed strokes, but may remain normal if the animals still can recover from the ischemic event. 67 MRA 68 and cerebral blood volume/cerebral blood flow studies 38 have been done and evaluated in several stroke models.…”

Section: Figmentioning

confidence: 99%

Magnetic resonance imaging, microscopy, and spectroscopy of the central nervous system in experimental animals

et al. 2005

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Summary:Over the last two decades, microscopic resolution in vivo magnetic resonance imaging (MRI) techniques have been developed and extensively used in the study of animal models of human diseases. Standard MRI methods are frequently used in clinical studies and in the general clinical practice of human neurological diseases. This generates a need for similar studies in experimental animal research. Because small rodents are the most commonly used species as animal models of neurological diseases, the MRI techniques need to be able to provide microscopic resolution and high signal-to-noise ratio images in relatively short time. Small animal MRI systems use very high field-strength magnets, which results in higher signal to noise ratio; however, the contrast characteristics of live tissue are different at these field strengths. In addition to standard MRI techniques, several new applications have been implemented in experimental animals, including diffusion and perfusion studies, MR angiography, functional MRI studies, MRI tractography, proton and phosphorous spectroscopy, cellular and molecular imaging using novel contrast methods. Here we give an overview of how to establish a small animal imaging facility with the goal of CNS imaging. We describe the basic physical processes leading to MR signal generation, highlighting the differences between standard clinical MRI and small animal MRI. Finally, typical findings in the most common neurological disease categories and novel MRI/magnetic resonance spectroscopy methods used in their study are also described.

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“…These generally require classic MR imaging modalities, including T1, T2, and proton density imaging. Newer techniques include diffusion and perfusion imaging and MRS for determining certain metabolites [116,117]. Many groups have used experimental middle cerebral artery ligation combined with hypoxia in rats or mice as models for human stroke (FIG.…”

Section: Stroke Modelsmentioning

confidence: 99%

“…MRS studies have been conducted with the aim of looking at the lactate peak, which becomes prominent when anaerobic glycolysis predominates [116,117,123]. Another important aspect is the N-acetyl-aspartate peak that may show a decrease in completed strokes, but may remain normal if the animals still can recover from the ischemic event [124].…”

Section: Stroke Modelsmentioning

confidence: 99%

MRI in Rodent Models of Brain Disorders

et al. 2011

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Summary: Magnetic resonance imaging (MRI) is a wellestablished tool in clinical practice and research on human neurological disorders. Translational MRI research utilizing rodent models of central nervous system (CNS) diseases is becoming popular with the increased availability of dedicated small animal MRI systems. Projects utilizing this technology typically fall into one of two categories: 1) true "pre-clinical" studies involving the use of MRI as a noninvasive disease monitoring tool which serves as a biomarker for selected aspects of the disease and 2) studies investigating the pathomechanism of known human MRI findings in CNS disease models. Most small animal MRI systems operate at 4.7-11.7 Tesla field strengths. Although the higher field strength clearly results in a higher signalto-noise ratio, which enables higher resolution acquisition, a variety of artifacts and limitations related to the specific absorption rate represent significant challenges in these experiments. In addition to standard T1-, T2-, and T2*-weighted MRI methods, all of the currently available advanced MRI techniques have been utilized in experimental animals, including diffusion, perfusion, and susceptibility weighted imaging, functional magnetic resonance imaging, chemical shift imaging, heteronuclear imaging, and 1 H or 31 P MR spectroscopy. Selected MRI techniques are also exclusively utilized in experimental research, including manganese-enhanced MRI, and cell-specific/molecular imaging techniques utilizing negative contrast materials. In this review, we describe technical and practical aspects of small animal MRI and provide examples of different MRI techniques in anatomical imaging and tract tracing as well as several models of neurological disorders, including inflammatory, neurodegenerative, vascular, and traumatic brain and spinal cord injury models, and neoplastic diseases.

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High resolution MRI and MRS: A feasibility study for the investigation of focal cerebral ischemia in mice

Cited by 42 publications

References 16 publications

ADC characterization of region‐specific response to cerebral perfusion deficit in rats by MRI at 9.4 T

ADC characterization of region‐specific response to cerebral perfusion deficit in rats by MRI at 9.4 T

Magnetic resonance imaging, microscopy, and spectroscopy of the central nervous system in experimental animals

MRI in Rodent Models of Brain Disorders

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