The Predictive Value of 3D Time-of-Flight MR Angiography in Assessment of Brain Arteriovenous Malformation Obliteration after Radiosurgery

1, Overestimation of nidus obliteration: a 0.90-mL tectal bAVM, which is clearly visible on MR imaging₁ (A and C white arrows). A−F, Both observers determined this bAVM to be obliterated on MR imaging₂ (B and D) almost 3 years later. However DSA₂, performed 6 weeks after MR imaging₂, still demonstrates a small nidus (E and F, white arrows) with early venous drainage toward the lateral sinus (F, white arrowheads). 2, Successful determination of nidus obliteration in the case of a 3.68-mL-deep temporal bAVM (straight white arrow, A−C). On the basis of MR imaging₂, both observers agreed that the nidus was obliterated 25 months after radiosurgery (D). Obliteration was angiographically confirmed 6 weeks later (E and F). 3, Underestimation of nidus obliteration: a small 0.17-mL central bAVM that was previously partially treated by endovascular embolization (A, C, and E). Because of hyperintensity on MR imaging₂ (B, white vertical arrow), both observers judged this bAVM to be patent 1 year after radiosurgery (B and D). However DSA₂ (F), performed 2 months after MR imaging₂, demonstrates absence of the previously present early venous drainage (E, white arrowhead). 4, Successful determination of a remaining nidus in case of a patent 2.32-mL tectal bAVM (white horizontal arrow, A and B). On the basis of MR imaging₂, both observers agreed that the nidus was patent 4 years after radiosurgery (C and D). The presence of a remnant nidus was angiographically confirmed 6 weeks later, when early venous drainage toward the straight sinus was observed (white arrowhead, E).