OBSERVER PERFORMANCE METHODOLOGIES FOR EVALUATING BLOOD-VESSEL VISIBILITY IN MR ANGIOGRAMS USING ACCURATE GEOMETRIC REGISTRATION TO HIGH-RESOLUTION X-RAY ANGIOGRAMS

Receiver operator characteristic (ROC) and two alternative forced choi ce (2AFC) methodologies for quantitatively assessing vessel visibility in MR angiography (MRA) were examined using x-ray angiography images as truth, The methodologies required MRA projection images with the sa me orientation and magnification as the x-ray images, Geometric distor tions limited the quality of the registration. The observer performanc e measurements were compared to vessel contrast-to-noise ratio (CNR) m easurements. Receiver bandwidth (RBW) and magnetization transfer (MT) effects in 3D time-off-light MRA were evaluated, Overall, applying MT significantly increased all three measurements while decreasing the RB W significantly improved the 2AFC and CNR measurements, The relative i mportance of both effects on the 2AFC measure increased as vessel diam eter decreased, although statistical significance was limited by small samples for diameters less than approximately 0.7 mm, These results d emonstrate the usefulness of these observer performance methodologies for MRA technique assessment.