Radiation injury versus malignancy after stereotactic radiosurgery for brain metastases: Impact of time-dependent changes in lesion morphology on MRI

Abstract

Background. We sought to determine whether radiation-induced injuries could be distinguished from malignancy after stereotactic radiosurgery (SRS) by analyzing time-dependent changes in lesion morphology on sequential MRI for up to 55min. Methods. In 31 consecutive patients treated with SRS for brain metastases, the time-dependent changes in lesion morphology were analyzed on MRI 2min, 15min, and 55min after contrast administration and on subtraction images. A simultaneous, matched-pairs approach was used for quantitative region of interest analysis of the area of the lesion. Qualitative analysis comprised the shape of the border, the structure of the interior area, the presence of leptomeningeal enhancement, and feeding vessels. The signal intensity changes of the border and the interior area of the lesions over time were assessed visually. The time-dependent changes in the 2 entities were compared. Results. Twenty radiation-induced injuries and 21 malignancies were analyzed. A significant interaction effect between time point and diagnosis (P