Assessment of brain metastases with dynamic susceptibility-weighted contrast-enhanced MR imaging: initial results

To assess if preradiation and early follow-up regional cerebral blood volume (CBV) measurements can help predict treatment outcome in patients with cerebral metastases and to evaluate regional CBV changes in tumor and normal tissue after radiosurgery.

In 18 patients, dynamic susceptibility-weighted contrast material-enhanced magnetic resonance (MR) imaging was performed with a 1.5-T unit, which allowed an absolute quantification of the regional CBV. Measurements were performed prior to and at 6 weeks and 3 months after therapy. Treatment outcome was classified according to tumor volume changes at 6 months. The regional CBV of the metastases and the normal adjacent brain tissue were determined with a region-of-interest analysis. Regional CBV values were correlated with the patient outcome to assess the sensitivity and specificity of dynamic susceptibility-weighted contrast-enhanced MR imaging.

The pretherapeutic regional CBV was not able to help predict a treatment outcome; however, the method proved to be highly sensitive and specific for treatment outcome prediction at the 6-week follow-up. A decrease of the regional CBV value helped predict the treatment outcome with a sensitivity of more than 90%. The tumor volume change alone had a sensitivity of only 64%. The measured regional CBV values of normal brain tissue and their ratio were comparable to physiologic data and remained unchanged with therapy.

The results suggest that dynamic susceptibility-weighted contrast-enhanced MR imaging is a useful method for the assessment of radiosurgically treated brain metastases. The implemented technique with determination of the arterial input function enables an absolute quantification of the regional CBV and prediction of tumor response.