Dynamic susceptibility contrast perfusion imaging of radiation effects in normal‐appearing brain tissue: Changes in the first‐pass and recirculation phases

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Abstract
Purpose: To identify radiation‐induced changes in the cerebral vasculature of healthy tissue in the first four months following radiotherapy through the analysis of dynamic‐susceptibility contrast perfusion imaging.Materials and Methods: Dynamic gradient‐echo imaging was performed on 22 patients during injection of a bolus of Gd‐DTPA contrast. The relative cerebral blood volume (rCBV), maximum ΔR2* of the first passage of the bolus, and a recirculation parameter were derived from gamma‐variate fits of the dynamic data. The white matter (WM) rCBV and peak heights were estimated through correlation with segmented T1‐weighted images. A percent recovery to baseline was also computed to further describe the recirculation phase.Results: A significant elevation of the recirculation phase was observed at doses > 15 Gy at two months following radiotherapy. This was reflected in an increased recirculation parameter in the fitted curves in the 15–30, 30–45, and >45 Gy dose groups to 2.8%, 3.8%, and 2.4% above the <15 Gy voxels, as well as in a decline in percent recovery to baseline. A trend toward lower rCBV and peak heights was observed at that same time point.Conclusion: The observed results suggest a dose‐dependent decline in vessel density and increase in vascular permeability and/or tortuosity in irradiated normal‐appearing brain tissue at two months following radiotherapy. J. Magn. Reson. Imaging 2005;21:683–693.

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