Non Tumor Perfusion Changes Following Stereotactic Radiosurgery to Brain Metastases.
OBJECTIVE
To evaluate early perfusion changes in normal tissue following stereotactic radiosurgery (SRS).


METHODS
Nineteen patients harboring twenty-two brain metastases treated with SRS were imaged with dynamic susceptibility magnetic resonance imaging (DSC MRI) at baseline, 1 week and 1 month post SRS. Relative cerebral blood volume and flow (rCBV and rCBF) ratios were evaluated outside of tumor within a combined region of interest (ROI) and separately within gray matter (GM) and white matter (WM) ROIs. Three-dimensional dose distribution from each SRS plan was divided into six regions: (1) <2 Gy; (2) 2-5 Gy; (3) 5-10 Gy; (4) 10-12 Gy; (5) 12-16 Gy; and (6) >16 Gy. rCBV and rCBF ratio differences between baseline, 1 week and 1 month were compared. Best linear fit plots quantified normal tissue dose-dependency.


RESULTS
Significant rCBV ratio increases were present between baseline and 1 month for all ROIs and dose ranges except for WM ROI receiving <2 Gy. rCBV ratio for all ROIs was maximally increased from baseline to 1 month with the greatest changes occurring within the 5-10 Gy dose range (53.1%). rCBF ratio was maximally increased from baseline to 1 month for all ROIs within the 5-10 Gy dose range (33.9-45.0%). Both rCBV and rCBF ratios were most elevated within GM ROIs. A weak, positive but not significant association between dose, rCBV and rCBF ratio was demonstrated. Progressive rCBV and rCBF ratio increased with dose up to 10 Gy at 1 month.


CONCLUSIONS
Normal tissue response following SRS can be characterized by dose, tissue, and time specific increases in rCBV and rCBF ratio.
Department of Medical Imaging, Division of Neuroradiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada Department of Biomedical Physics, Ryerson University, Toronto, Ontario, Canada.
Raphael
R
Jakubovic
Department of Radiation Oncology, Odette Cancer Centre of the Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
Arjun
A
Sahgal
Department of Radiation Oncology, Odette Cancer Centre of the Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
Mark
M
Ruschin
Department of Biomedical Physics, Ryerson University, Toronto, Ontario, Canada.
Ana
A
Pejović-Milić
Department of Medical Imaging, Division of Neuroradiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
Rachael
R
Milwid
Department of Medical Imaging, Division of Neuroradiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada richard.aviv@sunnybrook.ca.
Richard I
RI
Aviv
D001932:Brain Neoplasms / Q000098:blood supply* / Q000175:diagnosis / Q000556:secondary / Q000601:surgery*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000379:methods; D011879:Radiotherapy Dosage
Brain; Cancer; Dynamic susceptibility; Imaging; MR perfusion; Metastases; Normal tissue response