High-resolution Multiphase Contrast-enhanced Three-dimensional MR Angiography Compared with Two-dimensional Time-of-Flight MR Angiography for the Identification of Pedal Vessels

Abstract

The authors prospectively evaluated optimized multiphase high-resolution (HR) Gadolinium (Gd)-enhanced three-dimensional (3D) magnetic resonance (MR) angiography and standard two-dimensional (2D) time-of-flight (TOF) MR angiography for their ability to delineate distal calf and pedal vessels. Twelve patients (20 limbs) with limb-threatening peripheral arterial occlusive disease underwent HR Gd-enhanced and 2D TOF MR angiography to identify targets for distal bypass. Imaging of the region of the ankle and foot was performed on a 1.5 T system with a head coil. A standard 2D TOF MR angiography sequence was performed first. The HR Gd-enhanced MR angiography sequence was then performed after injection of 0.01-0.2 mmol/kg of gadodiamide, allowing the acquisition of multiple consecutive coronal partitions, each in 18-25 seconds. Two experienced angiographers independently analyzed both studies. Comparison with intraoperative conventional angiography was available in 10 limbs. HR Gd-enhanced MR angiography allowed significantly faster imaging time (P <.0001) and larger coverage area (P <.0001) than 2D TOF MR angiography. All segments seen on 2D TOF MR angiography were visualized on HR Gd MR angiography, and significantly more suitable targets were seen well on HR Gd-enhanced MR angiography than on 2D TOF MR angiography (mean targets per limb: 3.9 +/- 1.9 vs 2.6 +/- 1.5, respectively; P =.02). In addition, HR Gd-enhanced MR angiography allowed better visualization of the arcuate pedal branch than 2D TOF MR angiography (P <.0001). Excellent correlation was demonstrated between HR Gd-enhanced MR angiography and intraoperative angiography in 29 segments (binary similarity coefficient, 0.90). A significantly higher percentage of artifacts adversely affected image interpretation with 2D TOF MR angiography than with HR Gd-enhanced MR angiography (14 limbs vs five limbs, P <.001). Artifacts on HR Gd-enhanced MR angiography included suboptimal mask in two limbs, venous contamination in one patient (two limbs), and motion artifact in one limb, although the studies remained diagnostic in all cases. HR Gd-enhanced MR angiography identified more distal target vessels with greater confidence than 2D TOF MR angiography. Optimized HR Gd-enhanced MR angiography may replace 2D TOF MR angiography as the gold standard examination for evaluation of distal runoff.