Abstract：
:The effects of varying the inversion or excitation RF pulse flip angles on image contrast and imaging time have been investigated in IR imaging theoretically, with phantoms and with normal volunteers. Signal intensity in an IR pulse sequence as a function of excitation, inversion and refocusing pulse flip angles was calculated from the solution to the Bloch equations and was utilized to determine the contrast behavior of a lesion/liver model. Theoretical and experimental results were consistent with each other. With the TI chosen to suppress the fat signal, optimization of the excitation pulse flip angle results in an increase in lesion/liver contrast or allows reduction in imaging time which, in turn, can be traded for an increased number of averages. This, in normal volunteers, improved spleen/liver contrast-to-noise ratio (9.0 vs. 5.7, n = 8, p less than 0.01) and suppressed respiratory ghosts by 33% (p less than 0.01). Reducing or increasing the inversion pulse from 180 degrees results in shorter TI needed to null the signal from the tissue of interest. Although this decreases the contrast-to-noise ratio, it can substantially increase the number of sections which can be imaged per given TR in conventional IR imaging or during breathold in the snapshot IR (turboFLASH) technique. Thus, the optimization of RF pulses is useful in obtaining faster IR images, increasing the contrast and/or increasing the number of imaging planes.
journal_name
Magn Reson Imagingjournal_title
Magnetic resonance imagingauthors
Vinitski S,Albert S,Mitchell DG,Tasciyan TA,Rifkin MDdoi
10.1016/0730-725x(92)90481-esubject
Has Abstractpub_date
1992-01-01 00:00:00pages
207-15issue
2eissn
0730-725Xissn
1873-5894pii
0730-725X(92)90481-Ejournal_volume
10pub_type
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更新日期：2000-02-01 00:00:00
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更新日期：2001-12-01 00:00:00
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journal_title：Magnetic resonance imaging
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更新日期：1995-01-01 00:00:00
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