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. 2012 Mar 1;82(3):e493-500.
doi: 10.1016/j.ijrobp.2011.05.046. Epub 2011 Oct 12.

7-Tesla susceptibility-weighted imaging to assess the effects of radiotherapy on normal-appearing brain in patients with glioma

Janine M Lupo  1 , Cynthia F Chuang, Susan M Chang, Igor J Barani, Bert Jimenez, Christopher P Hess, Sarah J Nelson
Affiliations

7-Tesla susceptibility-weighted imaging to assess the effects of radiotherapy on normal-appearing brain in patients with glioma

Janine M Lupo et al. Int J Radiat Oncol Biol Phys. .

Abstract

Purpose: To evaluate the intermediate- and long-term imaging manifestations of radiotherapy on normal-appearing brain tissue in patients with treated gliomas using 7T susceptibility-weighted imaging (SWI).

Methods and materials: SWI was performed on 25 patients with stable gliomas on a 7 Tesla magnet. Microbleeds were identified as discrete foci of susceptibility that did not correspond to vessels. The number of microbleeds was counted within and outside of the T2-hyperintense lesion. For 3 patients, radiation dosimetry maps were reconstructed and fused with the 7T SWI data.

Results: Multiple foci of susceptibility consistent with microhemorrhages were observed in patients 2 years after chemoradiation. These lesions were not present in patients who were not irradiated. The prevalence of microhemorrhages increased with the time since completion of radiotherapy, and these lesions often extended outside the boundaries of the initial high-dose volume and into the contralateral hemisphere.

Conclusions: High-field SWI has potential for visualizing the appearance of microbleeds associated with long-term effects of radiotherapy on brain tissue. The ability to visualize these lesions in normal-appearing brain tissue may be important in further understanding the utility of this treatment in patients with longer survival.

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Figures

Figure 1
Figure 1
7T SWI (left) and 3T T2-FLAIR (right) images of (A) a grade II oligoastrocytoma 4 years post-chemotherapy, (B) a grade III ependymoma 2 years post-RT, (C) a grade II oligoastrocytoma 4 years post-RT, and (D) a grade III oligoastrocytoma 8 years post-RT. Red arrows denote microhemorrhages.
Figure 2
Figure 2
Plots of microbleed counts over time. (A) Total lesion count as a function of time for all patients who received RT (circles) and did not receive RT (squares) for all patients individually (left) and binned by years (right). (B) Percentage of microbleeds found outside the T2-lesion (T2L, triangles) and extending into the contralateral hemisphere (diamonds) as a function of time since RT for each individual RT patient (left) and when clustered by time (right).
Figure 3
Figure 3
Example of a patient with a grade III oligodendroglioma scanned serially. Microhemorrhages do not appear until over 2 years after having received radiation. The number of hemorrhages quadruples after 3 years post-RT.
Figure 4
Figure 4
Example of a grade III oligodendroglioma ~12 years post-RT with hemorrhages located both within and beyond the T2-lesion.
Figure 5
Figure 5
Radiation dosimetry contour lines overlaid on 7T SWI images. In (A), a grade II oligoastrocytoma 4.7 years post completion of RT with none of 28 total microbleeds in the contralateral hemisphere. In (B), a grade III oligodendroglioma 3.2 years post-RT with 5 of 25 total microbleeds existing in the controlateral hemisphere.
See this image and copyright information in PMC

References

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