Assessing perfusion changes during whole brain irradiation for patients with cerebral metastases

Purpose: To assess perfusion changes within brain and correlate these with clinical symptoms during whole brain radiotherapy (WBRT) for cerebral metastases. Materials and methods: Fourteen patients with cerebral metastases underwent dynamic CT perfusion scans during palliative whole brain irradiation. Perfusion scans were performed on Day 1 prior to initial radiotherapy treatment, then on Day 2, and on Day 5 immediately after completion of radiotherapy. Measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and capillary surface area permeability product (PS) were performed for each perfusion scan, and daily symptom assessment was taken prior to initial perfusion scan and thereafter prior to each daily radiation treatment. Results: Utilizing Day 1 as baseline, a 19% increase (P=0.033) was noted in PS at Day 2, (median 1.47 ml/100 g/min), which returned to Day 1 range at Day 5 (median 1.31 ml/100 g/min). When symptoms were correlated with perfusion parameters, a statistically significant association between change in MTT with change in headache scores was observed, baseline to Day 2 (P=0.019), and a trend between change in nausea scores with change in CBV (P=0.059) as well as change in MTT (P=0.098), baseline to Day 5. Conclusion: This study has demonstrated the feasibility of a non-invasive technique to assess changes occurring within the human brain during a course of radiation treatment. Dynamic perfusion tomography provides insight into the pathophysiological processes taking place and allows correlation with patient symptomatology.