Correction of errors caused by imperfect inversion pulses in MR imaging measurement of T1 relaxation times.
Spin-lattice (T1) relaxation times were measured by an inversion-recovery magnetic resonance imaging method with a slice-selective inversion pulse (SIP), a non-selective rectangular inversion pulse (RIP), or a B1-insensitive adiabatic inversion pulse (AIP). Data analysis either assumed perfect inversion (two-parameter fit) or allowed for imperfect inversion (three-parameter fit). Imperfect inversion pulses caused low T1 values in phantoms with a two-parameter fit, while three-parameter T1 estimates were accurate over the range 430-2670 ms. A difference of approximately 10% between two-parameter and three-parameter T1 values in normal human brain tissue was attributed to B1 inhomogeneity with the slice-selective inversion pulse and rectangular inversion pulse, to the slice profile with the slice-selective inversion pulse, and to T2 effects for the adiabatic inversion pulse. Any T1 method that relies on accurate flip angles may have a significant systematic error in vivo. Phantom accuracy does not ensure accuracy in vivo, because phantoms may have a more homogeneous B1 field and a longer T2 than do biological samples.
Kingsley
P B
PB
Department of Radiology, North Shore University Hospital, Manhasset, NY 11030, USA. kingsley@nshs.edu
Ogg
R J
RJ
Reddick
W E
WE
Steen
R G
RG
D000328:Adult; D001921:Brain / Q000033:anatomy & histology; D003627:Data Interpretation, Statistical; D003951:Diagnostic Errors / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D012016:Reference Values; D013997:Time Factors