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A simple correction for B1 field errors in magnetization transfer ratio measurements by Rebecca S. Samson; Claudia A.M. Wheeler-Kingshott; Mark R. Symms; Daniel J. Tozer; Paul S. Tofts is a Medicine article available to read on EtoBox.

What is A simple correction for B1 field errors in magnetization transfer ratio measurements about?

B1 errors are a problem in magnetization transfer ratio (MTR) measurements because the MTR value is dependent on the amplitude of the magnetization transfer (MT) pulse. B1 errors can arise from radiofrequency (RF) nonuniformity (caused by the RF coil, or skin effect and dielectric resonance in the subject's head) and also from inaccurate setting of the transmitter output when compensating for varying amounts of loading of the RF coil. B1 errors, and hence MTR errors, may be up to 5-10%, a large source of error in quantitative MR measurements. Radiofrequency nonuniformity may cause MTR histograms to be broadened. The dependence of MTR on B1 was modeled using binary spin bath theory, with a continuous wave (CW) approximation. For B1 reductions of up to 20%, normalized plots for different brain tissue types could be approximated by a single line, indicating that a systematic correction could be applied to MTR measurements with a known B1 error, regardless of tissue type. On a 1.5-T scanner with a birdcage coil, MTR was measured in 18 tissue types in five controls. The MT pulse amplitude was reduced in steps from its nominal value by up to 20%. Averaging data over all controls and tiss

Who reads A simple correction for B1 field errors in magnetization transfer ratio measurements?

Author

Rebecca S. Samson; Claudia A.M. Wheeler-Kingshott; Mark R. Symms; Daniel J. Tozer; Paul S. Tofts

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 0730-725X)

Published

2006

Language

EN

Field

Medicine (Health Sciences)