Influence of MT effects on T(2) quantification with 3D balanced steady-state free precession imaging.

Abstract

Signal from balanced steady-state free precession is affected by magnetization transfer. To investigate the possible effects on derived T(2) values using variable nutation steady-state free precession, magnetization transfer-effects were modulated by varying the radiofrequency pulse duration only or in combination with variable pulse repetition time. Simulations reveal a clear magnetization transfer dependency of T(2) when decreasing radiofrequency pulse duration, reaching maximal deviation of 34.6% underestimation with rectangular pulses of 300 μs duration. The observed T(2) deviation evaluated in the frontal white matter and caudate nucleus shows a larger underestimation than expected by numerical simulations. However, this observed difference between simulation and measurement is also observed in an aqueous probe and can therefore not be attributed to magnetization transfer: it is an unexpected sensitivity of derived T(2) to radiofrequency pulse modulation. As expected, the limit of sufficiently long radiofrequency pulse duration to suppress magnetization transfer-related signal modulations allows for proper T(2) estimation with variable nutation steady-state free precession. © 2010 Wiley-Liss, Inc.