APT-weighted and NOE-weighted image contrasts in glioma with different RF saturation powers based on magnetization transfer ratio asymmetry analyses
Article first published online: 9 MAY 2013
© 2013 Wiley Periodicals, Inc.
Magnetic Resonance in Medicine
Volume 70, Issue 2, pages 320–327, August 2013
How to Cite
Zhou, J., Hong, X., Zhao, X., Gao, J.-H. and Yuan, J. (2013), APT-weighted and NOE-weighted image contrasts in glioma with different RF saturation powers based on magnetization transfer ratio asymmetry analyses. Magn Reson Med, 70: 320–327. doi: 10.1002/mrm.24784
- Issue published online: 23 JUL 2013
- Article first published online: 9 MAY 2013
- Manuscript Accepted: 3 APR 2013
- Manuscript Revised: 11 MAR 2013
- Manuscript Received: 19 JAN 2013
- National Institutes of Health; Grant numbers: R01EB0 09731, R01EB015032, R01CA166171, and R21EB015555; Grant sponsor: National Natural Science Foundation of China; Grant number: 81128006; Grant sponsor: Hong Kong RGC; Grant numbers: CUHK418811 and SEG---CUHK02
Additional Supporting Information may be found in the online version of this article.
|mrm24784-sup-0001-suppfig1.pdf||106K||FIG. S1. Average z-spectra and MTRasym spectra of egg yolk and egg white (n = 4) with different RF saturation powers. a: z-spectra of egg yolk. b: MTRasym spectra of egg yolk. c: zspectra of eggwhite. d: MTRasym spectra of egg white.There were no visible APT signals in the downfield z-spectra of egg yolk at all RF saturation powers (a). However, there were visible NOE signals in the upfield z-spectra of egg yolk at lower RF saturation powers (0.6 and 0.9 μT). There were noticeable APT signals at a frequency difference of 3.5 ppm from water in the downfield z-spectra of egg white (c), corresponding to about 8.3 ppm in the proton MR spectra. Similarly, there were visible NOE signals in the upfield z-spectra of egg white at lower RF saturation powers. The presence of the APT effects in the egg white became more pronounced in the MTRasym spectra (d), showing that the APT signal intensities were maximized at the RF saturation powers of 3.2 μT.|
|mrm24784-sup-0002-suppfig2.pdf||129K||FIG. S2. Average z-spectra, MTRasym spectra, and MTRasym-difference spectra for 9L brain tumors (9-12 days post-implantation, n = 8) with different RF saturation powers. a: z-spectra of contralateral normal brain tissue. b: MTRasym spectra of contralateral normal brain tissue. c: zspectra of the tumors. d: MTRasym spectra of the tumors. e: MTRasym-difference spectra, defined by MTRasym(tumor) - MTRasym(normal).There were weak but visible APT signals (at a frequency difference of 3.5 ppm downfield from water) in the downfield z-spectra of the contralateral normal-appearing brain region (a) and the tumor (c), particularly at lower RF saturation powers (e.g., 0.6 μT). In addition, there were visible NOE signals (at a frequency difference of 2.5 − 4.5 ppm upfield from water) in the upfield z-spectra of these tissue entities. When the MT asymmetry was analyzed, the resulting MTRasym curves showed a varying MT asymmetry with a feature that was dependent on the applied RF powers. Particularly in the case of the contralateral brain region at the lower RF saturation powers (e.g., 0.6 μT), this varying MT asymmetry was near to zero or positive close to the bulk water resonance and then became negative for most large offsets (b). Notably, similar to the egg white case (Supporting Information Fig. S1d), the tumor MTRasym(3.5ppm) signals were maximized at 3.2 μT (d). We defined the MTRasym difference as: MTRasym(tumor) - MTRasym(normal). It is interesting that the MTRasym-difference spectra (e), most of which showed the highest peak at the offset of 3.5 ppm, were maximized at the RF saturation powers of 0.6−1.3 μT.|
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