MR angiography of aneurysm models of various shapes and neck sizes

To investigate the signal intensity of lateral and terminal saccular aneurysm models with differing neck sizes using three-dimensional time-of-flight (TOF) MR angiography with various imaging parameters. The study included four lateral and four terminal saccular aneurysm models with pulsatile flow. The height and fundus diameter were 10 mm; the neck diameters were 2.5 mm, 5 mm, 7.5 mm, and 10 mm, respectively. Each aneurysm model was examined with fast imaging with steady-state precession MR sequences with parameters of 20-140/7 (repetition time/echo time) and flip angles of 10 degrees to 30 degrees. Signal intensity was measured and compared among the models. Three-dimensional TOF MR angiography with the shorter repetition time and/or larger flip angle showed weaker signal intensity in the aneurysm models. Stronger signal intensity was obtained in the terminal saccular aneurysm models and/or the models with a wider neck than in the lateral saccular aneurysm models and/or the models with a narrower neck. In some aneurysm models, longer repetition times produced greater signal intensity than that of background brain models, but not in aneurysms with narrow necks. Noncontrast 3-D TOF MR angiography delineated terminal saccular aneurysms and/or aneurysms with wider necks and did not delineate lateral saccular aneurysms and/or aneurysms with narrower necks. Longer repetition times are recommended to allow the spins flowing into the aneurysms to recover.