SPRITE MRI with Prepared Magnetization and Centrick-Space Sampling

Mastikhin, Igor V.; Balcom, Bruce J.; Prado, Pablo J.; Kennedy, Christopher

doi:10.1006/jmre.1998.1612

Cited by 86 publications

(72 citation statements)

References 25 publications

(21 reference statements)

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“…Segmented acquisitions are required with these approaches. Various methods have been developed for this type of characterization (61,62). The low peak B 1 presently available on whole-body clinical MR systems may limit the utility of SPRITE methods, but human in vivo measurements have been made (63).…”

Section: Spi and Spritementioning

confidence: 99%

Clinical ultrashort echo time imaging of bone and other connective tissues

2006

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The background underpinning the clinical use of ultrashort echo time, SPRITE and other pulse sequences for imaging bone and other connective tissues with short T 2 is reviewed. Features of the basic physics relevant to UTE imaging are described, including the consequences when the radiofrequency pulse duration is of the order of T 2 so that rotation of tissue magnetization into the transverse plane is incomplete. Consequences of the broad linewidth of short T 2 components are also discussed, including partial saturation by off-resonance fat suppression pulses as well as those used in multislice and multiecho imaging. The need for rapid data acquisition of the order of T 2 is explained. The basic two-dimensional UTE pulse sequence with its half excitation pulse and radial imaging from the centre of k-space is described, together with options that suppress fat and/or reduce the signal from long T 2 components. The basic features of SPRITE and other sequences with very short TE are described. Image interpretation is discussed. Clinical features of the imaging of cortical bone, tendons, ligaments, menisci, periosteum and the spine are illustrated. The source of the short T 2 signal in these tissues is predominantly collagen and water tightly bound to collagen. Short T 2 components in all of these tissues are detectible and may show high signals. Possible future developments are outlined, as are technical limitations of clinical magnetic resonance systems.

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Section: Spi and Spritementioning

confidence: 99%

Clinical ultrashort echo time imaging of bone and other connective tissues

2006

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“…To improve the efficiency of the SPI sequence and significantly reduce the mechanical vibrations, the single point ramped imaging with the T 1 enhancement (SPRITE) technique was introduced 9 followed by later modifications. [10][11][12] SPRITE uses gradual gradient switching (stepfunction-like), avoiding large gradient ramps between successive phase-encoding steps. However, because of the large currents flowing through the gradient coils, overheating can become an issue for long experiments.…”

Section: ½1mentioning

confidence: 99%

Improvements in MR imaging of solids through gradient waveform optimization

2011

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Magnetic resonance imaging (MRI) is known to provide a useful approach for the exploration of the chemistry and dynamics of a wide range of soft condensed materials. However, its application to solids has been limited to those materials with relatively narrow resonances. The time needed to obtain an image of a solid with a given resolution and signal-to-noise ratio (SNR) is directly proportional to the line width of the resonance. For MRI to become practical for the imaging of solids it will have to rely on the development and use of MR sequences that avoid the issues raised by line broadening of the resonance. In this paper we review the latest contributions towards MR imaging of solids from our laboratory, in particular, applications using optimized gradient waveforms. Acoustic noise reduction and SNR improvement obtained with modifications of the standard single-point imaging sequence are presented and discussed using examples.

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“…Fortunately, due to much progress in modern MRI technologies, ultra-short T 2 * imaging sequences are becoming more routinely used in many areas of research. Pulse sequences able to capture signals from ultra-short T 2 * spins have been around for some years now (UTE [1], BLAST/RUFIS [2], SPI [3], SPRITE [4] and centric-SPRITE [5]). Generally, these techniques require using a short radiofrequency pulse, which means high peak power, to excite a broad and relatively flat band of resonance frequencies in the presence of an encoding gradient.…”

Section: Introductionmentioning

confidence: 99%

Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

Kobayashi¹,

Idiyatullin²,

Corum³

et al. 2011

AIP Conference Proceedings

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We describe a fundamentally different approach to MRI referred to as SWIFT (sweep imaging with Fourier transformation). SWIFT exploits time-shared RF excitation and signal acquisition, allowing capture of signal from spins with extremely short transverse relaxation time, T 2 *. The MR signal is acquired in gaps inserted into a broadband frequency-swept excitation pulse, which results in acquisition delays of only 1 -2 microseconds. In SWIFT, 3D k-space is sampled in a radial manner, whereby one projection of the object is acquired in the gaps of each frequencyswept pulse, allowing a repetition time (TR) on the order of the pulse length (typically 1 -3 milliseconds). Since the orientation of consecutive projections varies in a smooth manner (i.e., only small increments in the values of the x, y, z gradients occur from view to view), SWIFT scanning is close to inaudible and is insensitive to gradient timing errors and eddy currents. SWIFT images can be acquired in scan times similar to and sometimes faster than conventional 3D gradient echo techniques. With its ability to capture signals from ultrashort T 2 * spins, SWIFT promises to expand the role of MRI in areas of research where MRI previously played no or negligible role. In this article, we show wood and tooth images obtained with SWIFT as examples of materials with ultrashort T 2 *. Early experience suggests SWIFT can play a role in materials science and porous media research.

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SPRITE MRI with Prepared Magnetization and Centrick-Space Sampling

Cited by 86 publications

References 25 publications

Clinical ultrashort echo time imaging of bone and other connective tissues

Clinical ultrashort echo time imaging of bone and other connective tissues

Improvements in MR imaging of solids through gradient waveform optimization

Detecting Fleeting MRI Signals with Frequency-Modulated Pulses

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