PMC4001427_01
MRI and DSA image before SRS. (a) Contrast-enhanced T1W MR images reveal an AVM in the right temporal lobe. A nidus (arrow) and dilated draining veins (arrowheads) are visible. (b) ASL-MRI show high signal intensity in both the nidus (arrow) and distal portion of the draining veins (arrowheads). (c) A DSA image also reveals the AVM corresponding to MRI findings (arrow). (d) An SRS radiation-dose distribution image is shown.
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Contrast-enhanced MRI was performed with a 3.0-T clinical MRI scanner (Signa Excite HD, GE Healthcare, Milwaukee, WI, USA) and revealed a Spetzler-Martin grade III AVM in the right temporal lobe (Fig. 1a). These imaging techniques showed high signal intensity in the both nidus and distal portion of the draining veins (Fig. 1b). These MRI findings were also confirmed by DSA (Fig. 1c). Stereotactic radiosurgery was performed, in which the nidus and marginal areas were irradiated with 22 Gy and 20 Gy, respectively (Fig. 1d).
Longitudinal series of MR images after SRS. At 3 months after SRS, the nidus (arrow) had shrunk slightly on conventional MRI (MR angiography [MRA], T2W images, and contrast-enhanced T1W images), while high signal intensity on the ASL-MRI was unchanged. At 14 months, the high signal intensity of draining veins (arrowheads) on ASL-MRI was observed more proximally than on pre-SRS images, and shrinkage of the nidus and dilated draining veins was seen on other MR images. Finally, when the high flows in the nidus and dilatation of the draining veins had become unclear on T2W images and MRA at 24 months, the high signal intensity on ASL-MRI had also completely disappeared. Note that contrast-enhanced T1W images shows ring-like enhancements, probably due to radiation necrosis.
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ASL-MRI were performed at 3, 14, 24, and 30 months after SRS (Fig. 2).