Multiple echo frequency-domain image contrast: Improved signal-to-noise ratio and T2 (T*2) weighting

Yang, Qing; Demeure, Roger; Dardzinski, Bernard J.; Arnold, Blake W.; Smith, Michael B.

doi:10.1002/(sici)1522-2594(199902)41:2<423::aid-mrm30>3.0.co;2-m

Cited by 19 publications

(21 citation statements)

References 21 publications

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“…Work in this laboratory demonstrated advantages of HiSS MRI of the breast (30). Other work suggests that spectral/spatial MRI in various forms, including multiple gradient echo imaging (31), is advantageous for functional and anatomic MRI (30 -37). The advantages include improved fat suppression or fat/water separation, increased anatomic detail, and strong T 2 * contrast with reduced artifacts due to intravoxel dephasing effects.…”

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confidence: 99%

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

Medved

Zamora

et al. 2003

Magnetic Resonance Imaging

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Purpose:To evaluate the effect of varying spectral resolution on image quality of high spectral and spatial resolution (HiSS) images. Materials and Methods:Eight women with suspicious breast lesions and six healthy volunteers were scanned using echo-planar spectroscopic imaging (EPSI) at 1.5 Tesla with 0.75-to 1-mm in-plane resolution and 2.3-to 2.6-Hz spectral resolution. Time domain data were truncated to obtain proton spectra in each voxel with varying (2.6 -83.3 Hz) resolution. Images with intensity proportional to water signal peak heights were synthesized. Changes in water signal line shape following contrast injection were analyzed.Results: Fat suppression is optimized at ϳ10-Hz spectral resolution and is significantly improved by removal of wings of the fat resonance. This was accomplished by subtracting a Lorentzian fit to the fat resonance from the proton spectrum. The water resonance is often inhomogeneously broadened, and very high spectral resolution is necessary to resolve individual components. High spectral resolution is required for optimal contrast in anatomic features with very high T 2 * (e.g., within a lesion) and for detection of often subtle effects of contrast agents on water signal line shape. Conclusion:Despite a trade-off between the spectral resolution and signal-to-noise ratio, it is beneficial to acquire data at the highest spectral resolution currently attainable at 1.5 Tesla.

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confidence: 99%

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

Medved

Zamora

et al. 2003

Magnetic Resonance Imaging

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“…Unfortunately, the susceptibility variations induced by paramagnetic relaxation compounds reduce tissue T 2 s, which makes differentiable T 2 -weighted contrast a challenge at high fields. This work demonstrates the efficacy of a 3D CPMG acquisition and the multiecho frequency domain image contrast (MEFIC) method (20) for obtaining T 2 -weighted images of actively stained mouse brain with high SNR and CNR. Though this method shows promise, to the best of our knowledge few studies have investigated its application.…”

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confidence: 90%

Enhanced T₂ contrast for MR histology of the mouse brain

Sharief

Johnson

2006

Magnetic Resonance in Med

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A 3D Carr-Purcell-Meiboom-Gill (CPMG) sequence was implemented to obtain enhanced T 2 contrast in actively stained (perfusion with fixative and contrast agent) mouse brains at 9.4 T. Short interecho spacing was used to minimize diffusion and susceptibility losses. The sequence produced 16 3D volumes with an interecho spacing of 7 ms for isotropic 43--resolution images of the mouse brains in a scan time of 4 hr. To enhance the signal-to-noise ratio (SNR) and contrast, the multiecho frequency domain image contrast (MEFIC) method was applied, resulting in a composite image with T 2 -weighted contrast. The high SNR and contrast thus achieved revealed aspects of mouse brain morphology, such as multiple cortical layers, groups of thalamic nuclei, layers of the inferior and superior colliculus, and molecular and granular layers of the cerebellum, with a high degree of definition and contrast that was not previously achieved in Magnetic resonance histology (MRH) (1) has become a vital tool for a wide range of applications in pathology, neurobiology, and developmental biology. The use of superconducting magnets at high field strengths, specialized RF coils, and fast switching gradients has enabled resolution of Ն50 in the rodent brain (2,3). MRH offers an attractive complement to conventional histology, which is labor-and time-intensive. 3D images from MRH allow sectioning to be performed along any plane without the need for alignment and matching. The high soft-tissue contrast and signal-to-noise ratio (SNR) that it provides in the brain makes MRH particularly appealing for our specific application, i.e., morphometry in the mouse brain. Neuromorphometry includes volumetric analysis, shape information, and spatial organization of structures, which form the basis of morphological phenotyping of mouse models.A prerequisite for morphometry studies in the brain, however, is the ability to visually discriminate one structure from another. MRH exploits the inherent tissue properties of proton density, diffusion, spin-lattice relaxation (T 1 ), and spin-spin relaxation (T 2 ) to emphasize differences among tissue types and indicate the presence of pathology. An accurate assessment of these properties at high fields can guide the selection of scan parameters for maximum differential contrast of structures in the rodent brain. The high magnetic field strengths used in MRH ensure an SNR increase by a power in the range of 1-1.75 of the magnetic field strength (4). However, an imagequality metric of greater utility in the differentiation of tissues is the contrast-to-noise ratio (CNR) (5,6). The CNR in MRI is driven by tissue properties of T 1 , T 2 , proton density, and diffusion. However, the behavior of these properties at high magnetic fields makes it difficult to achieve optimal contrast between tissues. Previous studies (7-9) showed an increase in tissue T 1 s and a decrease in tissue T 2 s as the strength of the magnetic field increased. The long T 1 s necessitate inordinately long repetition times (TRs) to obtain truly T 2 ...

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“…Gradient echo-based sequences are especially prone to these artifacts. Several methods have been proposed to reduce these artifacts, including the GESEPI sequence [14,15]. In gradient echo imaging, slice selection correction methods have also been tried and successfully used [16,17].…”

Section: Differences Between Small Animal Imaging and Human Mri: Advamentioning

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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Multiple echo frequency-domain image contrast: Improved signal-to-noise ratio and T2 (T*2) weighting

Cited by 19 publications

References 21 publications

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

Enhanced T₂ contrast for MR histology of the mouse brain

MRI in Rodent Models of Brain Disorders

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Multiple echo frequency-domain image contrast: Improved signal-to-noise ratio and T2 (T*2) weighting

Cited by 19 publications

References 21 publications

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

The effect of varying spectral resolution on the quality of high spectral and spatial resolution magnetic resonance images of the breast

Enhanced T2 contrast for MR histology of the mouse brain

MRI in Rodent Models of Brain Disorders

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Product

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Enhanced T₂ contrast for MR histology of the mouse brain