Magnetic resonance imaging of low-grade and high-grade gliomas at 7 Tesla
Bixia Chen1,2, Philipp Dammann1,2, Stefan Maderwald1, Soeren Johst1, Tobias Schoemberg1,2, Lale Umutlu1,3, Harald H. Quick1,4, Mark Edward Ladd1,5, Ulrich Sure2, and Karsten Henning Wrede1,2

1Erwin L. Hahn Institute for MRI, University of Duisburg-Essen, Essen, Germany, 2Department of Neurosurgery, University Hospital Essen, University of Duisburg-Essen, Essen, Germany, 3Institute of Diagnostic and Interventional Radiology and Neuroradiology, University of Duisburg-Essen, Essen, Germany, 4High Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany, 5Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

Synopsis

Magnetic resonance imaging (MRI) plays a major role in diagnosis, multimodal treatment planning, and follow-up of low-grade and high-grade gliomas. In this prospective study, 24 patients were intra-individually examined at 3 Tesla (T) and 7T utilizing MPRAGE, T2 TSE, T2 FLAIR, and SWI sequences. Image evaluation had special focus on intra-tumoral structures, vascularization, intra-lesional hemorrhages, and contrast uptake. At 7T, intra-tumoral structures were depicted in excellent image quality. Especially SWI was superior at 7T compared to 3T and revealed microhemorrhages and vascularization patterns correlating with histopathology, possibly providing an additional imaging predictor for future grading of malignant gliomas.

Introduction

Gliomas are the most common primary brain tumors in adults with an estimated incidence of 12/100,000 cases per year. Magnetic resonance imaging (MRI) plays a major role in diagnosis, multimodal treatment planning, and follow-up of low-grade and high-grade gliomas. This prospective study aims to evaluate low-grade and high-grade gliomas using 7 Tesla (T) MRI in comparison to the current gold standard 3T MRI.

Material and Methods

Twenty-four patients suffering from low-grade and high-grade gliomas underwent preoperative MRI scans at 3T and 7T, respectively. The study group was comprised of 14 male and 10 female patients. The mean age was 50 years (range: 23 – 82 years). The local university institutional review board approved the study, and written informed consent was obtained before each examination. 3T imaging was performed on a whole-body MRI system (Magnetom Skyra, Siemens Healthcare GmbH, Erlangen, Germany) with a gradient system enabling a maximum amplitude of 45 mT/m and a slew rate of 200 mT/m/ms, using a vendor-provided 20-channel receive head/neck coil. Ultra-high-field 7T images were acquired on a whole-body MRI system (Magnetom 7T, Siemens Healthcare GmbH, Erlangen, Germany) with a gradient system of 38 mT/m maximum amplitude and a slew rate of 200 mT/m/ms, utilizing a 32-channel transmit/receive head coil (Nova Medical, Wilmington, USA). Acquired imaging sequences included non-enhanced and gadolinium-enhanced T1-weighted magnetization-prepared rapid acquisition gradient-echo1 (MPRAGE), susceptibility weighted imaging2 (SWI), T2-weighted turbo spin echo3 (TSE), and T2-weighted fluid-attenuated inversion recovery (FLAIR) (Fig. 1). Presence of adverse effects (e.g. general discomfort, nausea, heat sensations) was assessed and documented after each examination. Images were evaluated in consensus reading by two experienced raters with special focus on intra-tumoral structures, vascularization, intra-lesional hemorrhage, and contrast uptake. These findings were additionally correlated with histopathological gradings in all cases.

Results

All MRI examinations were tolerated well without report of any adverse effects. Tumors were located frontal (n=8), temporal (n=8), fronto temporal (n=2), parietal (n=2), occipital (n=2), frontoparietal (n=1), and infiltrating the corpus callosum (n=1). Histological diagnoses included: glioblastoma multiforme (WHO IV, n=8), anaplastic astrocytoma (WHO III, n=7), oligoastrocytoma (WHO II, n=3), anaplastic oligoastrocytoma (WHO III, n=2), fibrillary astrocytoma (WHO II, n=1), diffuse astrocytoma (WHO II, n=1), gemistocytic astrocytoma (WHO II, n=1), and gliosarcoma (WHO IV, n=1) (Fig. 2). Visualization of intra-tumoral structures by T1-weighted MPRAGE was superior at 7T compared to 3T due to improved image contrast (Fig. 3). Malignant gliomas showed microhemorrhages and sub-millimeter vascularization in ultra-high-resolution SWI at 7T, only vaguely delineated at 3T (Fig. 4). Depiction of tumor necrosis and perifocal edema was excellent in T2 TSE and T2 FLAIR images at both field strengths.

Discussion and Conclusion

Ultra-high-field 7T MRI can depict intra-tumoral structures in excellent image quality. Especially SWI was superior at 7T compared to 3T and revealed microhemorrhages and vascularization patterns that correlated with tumor grading. Further evaluation with focus on SWI in high-grade gliomas is warranted, as it might provide an additional imaging predictor for future grading scores of malignant gliomas.

Acknowledgements

The research leading to these results has received funding from the Interne Forschungsförderung Essen (IFORES), University Hospital Essen, University of Duisburg-Essen.

References

1. Wrede KH, Johst S, Dammann P et al. Caudal image contrast inversion in MPRAGE at 7 Tesla: problem and solution. Acad Radiol 2012 Feb;19(2):172-8.

2. Dammann P, Barth M, Zhu Y et al. Susceptibility weighted magnetic resonance imaging of cerebral cavernous malformations: prospects, drawbacks, and first experience at ultra-high field strength (7-Tesla) magnetic resonance imaging. Neurosurg Focus 2010 Sep;29(3).

3. Theysohn JM, Kraff O, Maderwald S et al. The human hippocampus at 7 T-in vivo MRI. Hippocampus 2009 Jan;19(1):1-7.

Figures

Figure 1: Imaging parameters for T1-weighted MPRAGE, SWI, T2 TSE, and T2 FLAIR sequences at 3T and 7T.

Figure 2: Histopathological findings and frequencies of WHO grade II (green), WHO grade III (yellow) and WHO grade IV (red) tumors are displayed.

Figure 3: This 51-year-old patient suffered from a glioblastoma multiforme (WHO IV) located in the trigone of the right lateral ventricle. Shown are gadolinium-enhanced 3T and 7T MPRAGE images. Contrast-enhancing tumor regions (arrows) and intra-tumoral structures are better delineated in 7T examinations compared to 3T.

Figure 4: Gliomas (asterisks) in SWI at 3T (a, b, c) and 7T (d, e, f). Diffuse astrocytoma (a, d) with homogeneous intra-tumoral structure. Pathological vascularization at 7T (e, arrow) in an anaplastic astrocytoma, vaguely visible at 3T (b). Delineation of microhemorrhages in glioblastoma at 7T (f, arrow) is superior to 3T.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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