CONTRAST-TO-NOISE-RATIO MEASUREMENTS IN 3-DIMENSIONAL MAGNETIC-RESONANCE ANGIOGRAPHY

RATIONALE AND OBJECTIVES. The authors report on the development and preliminary validation of a technique for measuring contrast-to-noise ratio (CNR) at all points along selected vessel segments in the original three-dimensional magnetic resonance angiography (MRA) dataset. METHODS. Contrast-to-noise ratio dependencies on flow rate, field of view, and flip angle were measured on images from a conventional time-of-flight MRA pulse sequence using constant flow in a branching vascular phantom. An estimate of the inherent variability of the technique was obtained from multiple scans of a flow phantom and a human volunteer. RESULTS. The overall standard deviation (SD) of the CNR was found to be approximately 6.1% of the average CNR value for the flow phantom study and 7.3% for the human study. Vessel CNR was found to increase with field of view and was found to become nonuniform for low flow rate and/or high flip angles. CONCLUSION. In general, such CNR measurements allow the investigation of the mechanism of signal loss and general technique optimization in MRA.