Two-dimensional time-of-flight MR angiography of the lower extremities: artifacts and pitfalls.

Abstract

method for noninvasive imaging of peripheral vascular disease. Two dimensional (2D) time-of-flight (TOF) MR an giography is the most common technique used for evaluation of the pelvic and infrainguinal arteries [11. This pictorial essay presents pit falls and artifacts that may be encountered dur ing clinical MR angiography of the lower extremities. Knowledge of these imaging find ings is essential for accurate interpretation of peripheral 2D TOF MR angiography. MR imaging was performed in a l.5-T Signa scanner (General Electric Medical Systems, Milwaukee, WI). The 2D TOF MR angiograms were acquired in the axial plane in standard body, head, or extremity coils with a spoiled gradient-recalledpulse se quence and flip angles of 45°for the pelvis and 600 for the extremities. The slice thick ness was 2.9 mm and field of view was 32 cm in the body coil; 2.0 mm and 22 cm, re spectively, in the head coil; and 2.0 mm and 16cm, respectively, in the extremity coil. Im aging parameters were TR range/TE range, 29—32/6.7—7.1; first-order gradient moment nulling (flow compensation); tracking infe nor saturation (usually 20 mm below the slice); 256 x 128 matrix; one excitation; and phase encoding from anterior to posterior. Three-dimensional sequences were acquired in the body coil using a fast spoiled gradient recalled or spoiled gradient-recalled pulse se quence; 45_600 flip angle; TR rangeiTE range, 10.6—32/2. 1—6.9; 28—60partitions, 2—2.5mm thick; 36-cm field of view; 256 x 128-256 ma trix; one excitation; and dynamic gadolinium enhancement in all cases [2J. Signal loss in a patent vessel from satura tion of in-plane flow is one of the most com mon pitfalls in 2D TOF MR angiography. When the path of a vesselcausesblood to re