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Inhomogeneity compensation in magnet...

Morrell, Glen R.

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Inhomogeneity compensation in magnetic resonance imaging.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Inhomogeneity compensation in magnetic resonance imaging./
作者:	Morrell, Glen R.
面頁冊數:	150 p.
附註:	Adviser: Albert Macovski.
Contained By:	Dissertation Abstracts International59-08B.
標題:	Engineering, Electronics and Electrical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9901560
ISBN:	0591986299

Inhomogeneity compensation in magnetic resonance imaging.
Morrell, Glen R.

Inhomogeneity compensation in magnetic resonance imaging. - 150 p.

Adviser: Albert Macovski.

Thesis (Ph.D.)--Stanford University, 1998.

Magnetic resonance is used to create images of the human body through the interaction of protons with static and time-varying magnetic fields. Most imaging methods assume perfectly uniform magnetic fields. In practice, the fields suffer from inhomogeneity due to constraints on coil design and magnetic susceptibility differences within the body. Field inhomogeneity degrades the quality of images formed by almost any magnetic resonance imaging (MRI) technique. It is a pervasive and persistent problem in MRI.

ISBN: 0591986299Subjects--Topical Terms:

626636
Engineering, Electronics and Electrical.

Inhomogeneity compensation in magnetic resonance imaging.
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100 1 $a Morrell, Glen R. $3 1258306
245 1 0 $a Inhomogeneity compensation in magnetic resonance imaging.
300 $a 150 p.
500 $a Adviser: Albert Macovski.
500 $a Source: Dissertation Abstracts International, Volume: 59-08, Section: B, page: 4340.
502 $a Thesis (Ph.D.)--Stanford University, 1998.
520 $a Magnetic resonance is used to create images of the human body through the interaction of protons with static and time-varying magnetic fields. Most imaging methods assume perfectly uniform magnetic fields. In practice, the fields suffer from inhomogeneity due to constraints on coil design and magnetic susceptibility differences within the body. Field inhomogeneity degrades the quality of images formed by almost any magnetic resonance imaging (MRI) technique. It is a pervasive and persistent problem in MRI.
520 $a Compensation of field inhomogeneity has traditionally been retrospective, consisting of image processing applied to the data after the MRI experiment is complete. This process fails for many MRI techniques. We present a new approach in which the MRI experiment itself is adapted to the field inhomogeneity, which is measured prior to the imaging experiment.
520 $a We have developed the technique of three-dimensional spectral-spatial excitation as a means of creating spectrally selective excitations whose center frequency of excitation varies as a function of spatial location within an imaging plane. This variation is tailored to the measured inhomogeneity of the main field. We have demonstrated through in vivo water-only imaging studies that this technique can achieve spectrally selective excitation in the presence of main field inhomogeneity which causes conventional spectrally selective excitation to fail.
520 $a We have also applied the technique of dynamic shimming to a few commonly used multi-slice imaging techniques which are particularly sensitive to main field inhomogeneity. Dynamic shimming involves the real-time modification of shim currents and center frequencies during the scan to optimally compensate for main field inhomogeneity measured in each slice of a multi-slice scan. In vivo studies show marked improvement in multi-slice fat saturation, single-shot echo-planar, and fast spiral imaging with dynamic shimming, as compared to conventional shimming optimized over the entire imaging volume.
520 $a We also present a novel method of mapping the radio-frequency (RF) excitation field which is useful over a wide range of field inhomogeneity, with accuracy and insensitivity to noise which compares favorably with existing techniques. This technique could be combined with multi-dimensional excitation to compensate for inhomogeneity in both the main field and the RF field.
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791 $a Ph.D.
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