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Quantitative amide proton transfer imaging with reduced interferences from magnetization transfer asymmetry for human brain tumors at 3T
Author(s) -
Zhao Xuna,
Wen Zhibo,
Li Chunmei,
Chen Min,
Wang Yi,
Gao JiaHong
Publication year - 2015
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.25411
Subject(s) - magnetization transfer , asymmetry , nuclear magnetic resonance , saturation (graph theory) , physics , magnetic resonance imaging , medicine , radiology , mathematics , quantum mechanics , combinatorics
Purpose To develop a novel analysis method to evaluate quantitative amide proton transfer (qAPT) effects with reduced interference of conventional magnetization transfer effect. Methods A modified Z‐spectrum is generated by a fitting procedure that achieves an effectively reduced magnetization transfer asymmetry. A qAPT map is then produced by subtraction of the original Z‐spectrum from the modified version. This approach has been tested on both healthy volunteers and patients with brain tumors. Comparisons are made between the maps of qAPT and the commonly‐used MTR asym (3.5 ppm) at different saturation powers. The negative background (NB) in MTR asym (3.5 ppm) image is recovered from the difference between the MTR asym (3.5 ppm) and qAPT maps. Results Both qAPT and MTR asym (3.5 ppm) are strongly dependent on saturation power. At a saturation power below 2 µT, the MTR asym (3.5 ppm) map is dominated by the NB rather than the APT effects for healthy brain tissue. Similar to the MTR asym (3.5 ppm) image, the qAPT image exhibits strong and robust tumor contrast. Conclusion The newly‐developed analysis method of qAPT is able to obtain a quantitative APT effect with less inferences from magnetization transfer asymmetry as compared to the conventional MTR asym (3.5 ppm) and can be used to evaluate human brain tumors at 3T. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc. Magn Reson Med 74:208–216, 2015. © 2014 Wiley Periodicals, Inc.