Abstract
Introduction
Cerebral microbleeds have been observed in normal-appearing brain tissue of patients with glioma years after receiving radiation therapy. The contrast of these paramagnetic lesions varies with field strength due to differences in the effects of susceptibility. The purpose of this study was to compare 3T and 7T MRI as platforms for detecting cerebral microbleeds in patients treated with radiotherapy using susceptibility-weighted imaging (SWI).
Methods
SWI was performed with both 3T and 7T MR scanners on ten patients with glioma who had received prior radiotherapy. Imaging sequences were optimized to obtain data within a clinically acceptable scan time. Both T2*-weighted magnitude images and SWI data were reconstructed, minimum intensity projection was implemented, and microbleeds were manually identified. The number of microbleeds was counted and compared among datasets.
Results
Significantly more microbleeds were identified on SWI than magnitude images at both 7T (p = 0.002) and 3T (p = 0.023). Seven-tesla SWI detected significantly more microbleeds than 3T SWI for seven out of ten patients who had tumors located remote from deep brain regions (p = 0.016), but when the additional three patients with more inferior tumors were included, the difference was not significant.
Conclusion
SWI is more sensitive for detecting microbleeds than magnitude images at both 3T and 7T. For areas without heightened susceptibility artifacts, 7T SWI is more sensitive to detecting radiation therapy-induced microbleeds than 3T SWI. Tumor location should be considered in conjunction with field strength when selecting the most appropriate strategy for imaging microbleeds.
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Acknowledgments
The authors would like to thank Andre Cote, Adam Elkhaled, Angela Jakary and Trey Jalbert for their work in MR image acquisition and Bert Jimenez and Mary McPolin for their clinical coordination of patient MR scans. This work was supported by UC Discovery grant ITL-BIO04-10148, which is an academic-industry partnership grant with General Electric Healthcare, a UCSF REAC Cohn & Simon Memorial Fund and a fellowship from the Graduate Education in Medical Sciences (GEMS) training program funded by Howard Hughes Medical Institute (HHMI).
Conflict of interest
Grant support for this project was funded in part by GE Healthcare.
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This study was presented in part at the 20th annual meeting of the International Society for Magnetic Resonance in Medicine, 2012, Melbourne, Australia.
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Bian, W., Hess, C.P., Chang, S.M. et al. Susceptibility-weighted MR imaging of radiation therapy-induced cerebral microbleeds in patients with glioma: a comparison between 3T and 7T. Neuroradiology 56, 91–96 (2014). https://doi.org/10.1007/s00234-013-1297-8
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DOI: https://doi.org/10.1007/s00234-013-1297-8