Gradient and Spin-Echo (GRASE) Imaging
Magnetic resonance (MR) imaging pulse sequences are developed through an evolutionary process rather than by entirely de nova invention. Useful new imaging sequences evolve by combining new and existing methodology. For example, spin warp phase encoding was incorporated into selective line scan imaging to produce contemporary 2D FT gradient echo imaging (4). The incorporation of a 180° RF refocusing pulse into 2D FT gradient echo imaging yielded spin echo imaging (1). Spin echo images and gradient echo images differ considerably in their static field inhomogeneity and susceptibility artifacts, tissue contrast and the effects of blood flow. Elimination of field inhomogeneity artifacts allowed for much later echo times, increasing T2 contrast in spin echo images, which is extremely useful for tissue characterization in medical diagnosis. Development of pulse sequences may in retrospect appear straightforward. In reality, there are often major difficulties in removing unanticipated image artifacts in new imaging sequences for which solutions often require more creativity than do the original sequence. Imaging with multiple spin echoes was hypothetically suggested as a simple variant of gradient refocused echo-planar imaging (EPI) but without consideration of artifacts from stimulated echo magnetization. It took years and contributions from several scientists [19, 31] to overcome stimulated echo artifacts for successful implementation of spin-echo train imaging.
KeywordsPhase Error Spin Echo Field Inhomogeneity CPMG Sequence Read Period
Unable to display preview. Download preview PDF.
- 3.Edelstein WA, Hutchison JM, Johnson G, Redpath TW, Mallard JR (1980) UK Patent no GB2,079,463A, methods of producing image information from objects (priority date: 3/14/ 1980)Google Scholar
- 7.Feinberg DA, Hale JD (1986) Inner-volume echo planar imaging in book of abstracts. Proceedings of 5th annual meeting, Society of Magnetic Resonance in Medicine, p 950Google Scholar
- 8.Feinberg DA, Oshio K (1991) US Patent no 5,270,654 Ultra-fast multi-section MRI using gradient and spin echo (GRASE) imaging (priority date: 7/6/1991)Google Scholar
- 10.Feinberg DA, Oshio K (1991) Gradient-echo time shifting in fast imaging. In: Book of abstracts (works in progress), 10th annual meeting, Society of Magnetic Resonance in Medicine, San Francisco, p 1239Google Scholar
- 13.Feinberg DA (1993) GRASE imaging provides image quality and speed, Diagnostic Imaging. Miller Freeman, 2: p 71–78Google Scholar
- 17.Feinberg DA, Kiefer B (1994) High resolution imaging of the brain with GRASE (TGSE). First meeting of the Society of Magnetic Resonance in Medicine. J Magn Res Imaging 4(P):48Google Scholar
- 18.Feinberg DA, Kiefer B (1994) High speed T2-weighted imaging of the liver with single-shot GRASE (TGSE). First meeting of the Society of Magnetic Resonance in Medicine. J Magn Reson Imaging 4(P):48Google Scholar
- 22.Kiefer B, Hollenbach HP, Feinberg DA (1994) T2-weighted imaging with long echo train 3D turbo gradient spin-echo for neurological applications with high resolution. Second meeting of the Society of Magnetic Resonance in Medicine, San Francisco, 1994Google Scholar
- 29.Oshio K, Jolesz F (1994) Fast T1-weighted imaging with multiexcitation EPI. Proceedings from the 1st meeting of the Society of Magnetic Resonance, p 37Google Scholar
- 30.Rofsky NM, Weinreb JC, Safir J, Mercado C, Goldman JP, Megibow AJ (1994) Comparison of fat suppression techniques for hepatic MR imaging: turbo-SE, breath-hold turbo-SE, GRASE, and turbo STIR. First meeting of the Society of Magnetic Resonance in Medicine. J Magn Reson Imaging 4(P):66CrossRefGoogle Scholar
- 31.Strobel B, Ratzel D (1984) US Patent no 4,697,148. Process for the excitation of a sample for NMR tomography (priority date: 4/18/84)Google Scholar