Education Exhibit
نویسندگان
چکیده
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 Sis sampled), and (c) fully refocused (both S+ and Sare sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steadystate 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.
منابع مشابه
Assessing the impact of community-based education on dental school finances: introduction to the report.
ADEA ANNUAL SESSION PROCEEDINGS, 2011 ADEA Bylaws. 2011;75(7):889–907. ADEA Executive Director’s Report. Richard W. Valachovic. 2011;75(7):851–6. ADEA Mission Statement and Strategic Directions, 2011–14. 2011;75(7):908–9. ADEA President’s Address. Sandra C. Andrieu. 2011; 75(7):844–7. ADEA President-Elect’s Address. Leo E. Rouse. 2011; 75(7):848–9. ADEA Staff (as of June 2011). 2011;75(7):996. ...
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