**2.5 Functional MRI**

fMRI is used to detect abnormalities in brain areas adjacent to AVM borders or deficits in specific cognitive tasks correlated with regions affected by it [41]. fMRI can help to evaluate AVM margins and aid in preventing damage to surrounding brain tissue during interventional sessions. AVMs are congenital pathologies. Thus, it is suggested that the developing brain neuroplasticity will present different fMRI images for healthy and pathologic cases. Caramia et al. used fMRI and transcranial magnetic stimulation (TMS)—which directly explore cortical neurons' electrical activity—and showed cortical motor areas reorganized in the AVM containing hemisphere [51]. The main limitation of fMRI is that it does not directly detect AVMs as MRI does. Therefore, it should be used as a treatment planning tool rather than for standard diagnostics [23].

#### **2.6 Magnetic resonance angiography**

MRA is valuable in providing AVMs with 3D angiographic images and hemodynamic data [23]. MRA techniques are characterized by two main parameters—flow and contrast. State-of-the-art MRA techniques are:

• Time-of-flight (TOF) MRA: TOF-MRA or inflow angiography enhances blood flow areas by shortening the MRI echo time (TE) parameter, thus reducing the *Advocating Intraluminal Radiation Therapy in Cerebral Arteriovenous Malformation Treatment DOI: http://dx.doi.org/10.5772/intechopen.89662*

execution number in each flow-related voxel in comparison with stationary voxels. This results in flow patterns appearing brighter. The technique can also aid in finding residual AVMs [41]. However, Lee et al. report the accuracy and specificity rates of only 75–78 and 68% respectively, which leaves DSA at the front-end [52].

