Nonenhanced methods for lower‐extremity MRA: A phantom study examining the effects of stenosis and pathologic flow waveforms at 1.5T

Abstract

Purpose To evaluate the signal properties of 2D time of flight (TOF), quiescent-interval single-shot (QISS), ECG-gated 3D fast spin-echo (FBI), and ungated 3D fast spin-echo ghost (Ghost) magnetic resonance angiography (MRA) over a range of flow velocities in a pulsatile flow phantom with a 50% diameter stenosis at 1.5T. Materials and Methods Blood-mimicking fluid was pumped at eight peak flow velocities through a stenotic region in triphasic and monophasic waveforms. Vascular signal proximal, within, and distal to the stenosis was measured from the source images of the four MRA methods. Coronal maximum intensity projection images were used to compare image quality. Results TOF and QISS signal trends were similar, but QISS exhibited the most consistent signal across velocities. At high velocities (≥42.4 cm/s), TOF showed post-stenotic signal loss that was not observed with QISS. FBI and Ghost signals peaked at low velocities (3.9–9.7 cm/s) without flow compensation and at high velocities (≥64.6 cm/s) with flow compensation. Conclusion FBI and Ghost demonstrated dependence on blood flow velocity and flow compensation. TOF was sensitive to flow artifacts at high velocities. QISS proved most robust for accurately depicting the normal lumen and stenosis under a wide range of flow conditions. Monophasic and triphasic flow did not appreciably affect the signal performance of any method.

Nonenhanced peripheral MR-angiography (MRA) at 3 Tesla: evaluation of quiescent-interval single-shot MRA in patients undergoing digital subtraction angiography

“…However, specificity and image quality were significantly higher for QISS-MRA compared to Native SPACE-MRA. These study results confirm in vitro data indicating a superiority of QISS-MRA over subtractive MRA techniques [29].…”

“…Image quality of QISS-MRA was non-diagnostic in 2-3 % of the vessel segments. Non-diagnostic Vessel segments: Aorta (1), AIC right and left common iliac artery (2, 3), AIE right and left external iliac artery (4,5), AFC right and left common femoral artery (6, 7), AFP right and left deep femoral artery (8,9), AFS right and left proximal and distal superficial femoral artery (10)(11)(12)(13), AP right and left proximal, middle, and distal popliteal artery (14)(15)(16)(17)(18)(19), ATA right and left proximal and distal anterior tibial artery (20)(21)(22)(23), TFT right and left tibiofibular trunk (24,25), PTA right and left proximal and distal posterior tibial artery (26)(27)(28)(29), and AF right and left proximal and distal fibular artery (30)(31)(32)(33) image quality was attributed to off-resonance artifacts. Off-resonance refers to a deviation of the local spins' resonant frequency in relation to the nominated scanner center frequency and is caused by main field inhomogeneities or magnetic susceptibilities [21].…”

“…The arterial vascular tree was divided into 32 segments for analysis of image quality and diagnostic performance: abdominal aorta (1), pelvic vessel segments including right and left common iliac artery (2, 3), right and left external iliac artery (4,5), and right and left common femoral artery (6,7), thigh vessel segments including right and left deep femoral artery (8,9), right and left proximal and distal superficial femoral artery (10-13), right and left proximal, middle, and distal popliteal artery (14)(15)(16)(17)(18)(19), and calf vessel segments including right and left proximal and distal anterior tibial artery (20)(21)(22)(23), right and left tibiofibular trunk (24,25), right and left proximal and distal posterior tibial artery (26)(27)(28)(29), and right and left proximal and distal fibular artery (30-33). Two blinded readers (M.W.…”

Non‐contrast enhanced MR angiography: Physical principles

“…This 2D overlap reduces the coverage efficiency of the technique. The 2D TOF technique is notorious for depicting false stenoses at the carotid notch due to reduced inflow refreshment caused by the angle of the vessel orientation (42). Also, the 2D TOF technique commonly generates signal voids in the carotid bulb due to recirculating flow patterns (43).…”

“…Due to the requirement of two scan acquisitions and multiple R-wave intervals, the methods are generally slow. Due to the inherent flow-spoiling effects of FSE, very fast and/or turbulent flow, like poststenotic flow, generates a flow void even in the BA scan (42). Since the BA scan and the DA scan depict vessels with low signals in this region, a signal void appears in the subtraction angiogram leading to a tendency toward overestimation of stenosis.…”