Advanced MRI Scan Before and After Radiation Therapy for the Detection of Intracranial Metastasis

PRIMARY OBJECTIVES: I. Conspicuity: Ia. To assess the conspicuity of idealized T1 and T2 imaging at detecting brain metastases at baseline. (Quantitative MRI) Ib. To assess the conspicuity (CNR) of chemical exchange saturation transfer (CEST) imaging at detecting brain metastases at baseline. (CEST MRI) Ic. To assess the conspicuity (CNR) of advances in difference equations (Adv Diff) at detecting brain metastases at baseline. (Multiple B Value Diffusion Imaging \[Adv Diff\]) Id. To assess the conspicuity of gradient- and spin-echo (GESE) dynamic susceptibility contrast (DSC) and standard Gradient Echo (GE) DSC at detecting brain metastases at baseline. (GESE DSC perfusion imaging) SECONDARY OBJECTIVES: I. Conspicuity: Ia. To assess the conspicuity of T2 imaging at detecting brain metastases on a per-patient basis at follow-up scans and on a per-lesion basis at baseline and at follow-up time points. (Quantitative MRI) Ib. To assess the conspicuity (CNR) of CEST imaging at detecting brain metastases on a per-patient basis at follow-up scans and on a per-lesion basis at baseline and at follow-up time points. (CEST MRI) Ic. To assess the conspicuity (CNR) of Adv Diff at detecting brain metastases on a per-patient basis at follow-up scans and on a per-lesion basis at baseline and at follow-up time points. (Multiple B Value Diffusion Imaging \[Adv Diff\]) Id. To assess the conspicuity of GESE DSC and standard Gradient Echo (GE) DSC at detecting brain metastases on a per-patient basis at follow-up scans and on a per-lesion basis at baseline and at follow-up time points. (GESE DSC perfusion imaging) II. Treatment response. IIa. To assess the trend of idealized quantitative T1 and T2 values of brain metastases compared to normal brain parenchyma following treatment with stereotactic radiosurgery. (Quantitative MRI) IIb. To assess the ability of CEST imaging to differentiate radiation necrosis from progressive disease in brain metastases following stereotactic radiosurgery. (CEST MRI) IIc. To assess whether Adv Diff can differentiate radiation necrosis from progressive disease in brain metastases following stereotactic radiosurgery. (Multiple B Value Diffusion Imaging \[Adv Diff\]) IId. To assess whether GESE DSC improves differentiation of radiation necrosis from progressive disease in brain metastases following stereotactic radiosurgery compared to standard GE DSC. (GESE DSC perfusion imaging) IIe. To assess the ability of Adv arterial spin labeling (ASL) to differentiate radiation necrosis from progressive disease in brain metastases following stereotactic radiosurgery. (Multiple inversion time \[TI\] ASL "Adv ASL" perfusion) OUTLINE: Patients undergo conventional and advanced MRI scans over 60 minutes within 14 days before the start of scheduled brain radiation treatment. Patients then undergo 7 additional MRI scans over 60 minutes each between 4-16 weeks apart. Patients may receive gadolinium and/or iopamidol during MRI scans.