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Inmr acronym11/3/2022 ![]() ![]() ![]() T2-like contrast (T2*) can be obtained with increasing echo time (TE), as with conventional SE imaging. Spin-density images can be obtained with a GE technique with short TR if a small flip angle is used. For steady-state sequences where the TR is shorter than the T2, tissues with long T1 and T2 will show preferentially increased signal with increasing flip angle. Spoiled GE sequences will be more T1-weighted with higher flip angles approaching 90°. Flip angle is a powerful modifier of GE contrast. If the T2 of interest is long (e.g., CSF), then the steady-state sequence will give the familiar CSF myelogram effect. For tissue with a short T2 (e.g., fat, muscle), or sequences requiring long TR, the spoiled and steady-state sequences look the same. Inmr acronym free#In steady-state sequences (fast-imaging steady precession, steady-state free precession, and GRASS), this transverse magnetization is maintained and stabilizes after a few pulses. Spoiled sequences (fast low-angle shot and spoiled gradient-recalled acquisition in steady state ) destroy the residual transverse magnetization after each alpha pulse. There are two types of GE imaging spoiled and steady-state. Intrinsic to good image quality in GE imaging is the choice of flip angle, which has optimal values for specific TRs and tissue types, the Ernst angle (the longer the T1 of the tissue, the smaller the best flip angle). This gradient-driven echo allows for rapid imaging with very short repetition time (TR). Gradient echo (GE) imaging does not use a 180° pulse to achieve the echo. No apologies are offered for potentially sending the interested and highly motivated reader down an ultimately useless sequence road. Existing literature tends to be preliminary, and reports findings in few patients. Thirdly, and as is often the case with rapidly changing technology, the sequences may be quickly put into clinical use without much support in the scientific literature. Second, the majority of sequences discussed were obtained at mid and high field (1–1.5 T) therefore, I cannot attest to their usefulness at lower field strength. Cord and CSF motion studies will not be covered, and peripheral nerve evaluations such as the lumbar and cervical plexi have been reviewed recently (1, 2). First, a few disclaimers: this review is necessarily limited, and I do not presume to cover every conceivable pulse sequence. This review will focus on some new sequences that might have real clinical impact on spinal imaging, as well as new applications of some older techniques. Even more choices are potentially available, but have shown little clinical use. Fortunately, a convergence of these forces has also occurred, allowing for current sequences with high C/N and short examination times.Ī myriad of choices are available for spine imaging, often with a bewildering array of names, acronyms, and parameters. Many novel MR imaging techniques have been developed with one of two driving forces behind them-increased speed of acquisition or improved lesion detection. This should be in a form that is quick and easy to interpret, and eliminates tedious multiple imaging manipulation and off-line processing. From a minimalist standpoint, what is desired is enough contrast to noise (C/N) in the shortest imaging time to provide diagnostic accuracy. The goal is to provide a voxel size that provides adequate yet small enough signal-to-noise (S/N) ratios for contrast resolution that provide the necessary spatial resolution. These choices will be influenced by the anatomic area to be studied, the desired field of view (FOV), spatial resolution, and contrast needs. In the performance of any MR examination, major decisions include selection of the appropriate coil, imaging plane, slice thickness, imaging matrix, number of excitations, and pulse-sequence parameters. Nevertheless, despite being somewhat overshadowed by their flashier cephalad cousins, significant advances have been made in sequence design and implementation that will directly impact the ease and confidence of spinal disease interpretation. With the tremendous technical advances in MR imaging of the brain, such as perfusion, diffusion, and blood oxygenation level-dependent (BOLD) functional imaging, and contrast-enhanced MR angiography, the continued advances in MR imaging of the spine unfortunately may be overlooked. ![]()
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