HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chavhan, G. B. Articles by Shroff, M. M. PubMed PubMed Citation Articles by Chavhan, G. B. Articles by Shroff, M. M. Related Collections Magnetic Resonance Imaging Physics and Basic Science

Steady-State MR Imaging Sequences: Physics, Classification, and Clinical Applications¹

¹ From the Department of Diagnostic Imaging, Hospital for Sick Children and University of Toronto, 555 University Ave, Toronto, ON, Canada M5G 1X8 (G.B.C., P.S.B., H.L.M.C., M.M.S.); and Jankharia Imaging Center, Mumbai, India (B.G.J.). Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received February 23, 2007; revision requested May 18; final revision received October 5; accepted October 24. All authors have no financial relationships to disclose. Address correspondence to G.B.C. (e-mail: drgovindchavhan{at}yahoo.com).

Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reached: preexcitation signal (S–) from echo reformation; and postexcitation signal (S+), which consists of free induction decay. Depending on the signal sampled and used to form an image, steady-state sequences can be classified as (a) postexcitation refocused (only S+ is sampled), (b) preexcitation refocused (only S– is sampled), and (c) fully refocused (both S+ and S– are sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steady-state sequences have revolutionized cardiac imaging and have become the standard for anatomic functional cardiac imaging and for the assessment of myocardial viability because of their good signal-to-noise ratio and contrast-to-noise ratio and increased speed of acquisition. They are also useful in abdominal and fetal imaging and hold promise for interventional MR imaging. Because steady-state sequences are now commonly used in MR imaging, radiologists will benefit from understanding the underlying physics, classification, and clinical applications of these sequences.

© RSNA, 2008