Assessment of scanner performance and normalization of estimated relaxation rate values

The purpose of this study was to develop and test a method for the assessme nt of Magnetic Resonance (MR) scanner performance suitable for routine brai n MR studies and for normalization of calculated relaxation times. We hypot hesized that regular monitoring of machine performance changes could provid e a helpful normalization tool for calculating tissue MR parameters, thus c ontributing to support their use for longitudinal and comparative studies o f both normal and diseased tissues. The method is based on the acquisition of phantom images during routine bra in studies with standard spin-echo sequences. MR phantom and brain tissue p arameters were used to assess the influence of machine related changes on r elaxation parameter estimates. Experimental results showed that scanner per formance may affect relaxation rate estimates. Phantom and in vivo results indicate that the correction method yields a reduction in variability of es timated phantom R1 values up to 29% and of R1 for different brain structure s up to 17%. These findings support the validity of using brain coil phanto ms for routine system monitoring and correction of tissue relaxation rates. (C) 2001 Elsevier Science Inc. All rights reserved.