Comparison of methods for instantaneous angiographic blood flow measurement

Several different algorithms have been reported for measurement of blood fl ow rates and velocities from digital x-ray angiograms. We compare four vide odensitometric methods: (1) distance-density curve matching (DDCM), (2) dis tance-density curve matching with curve-fitting (DDCM-F), (3) bolus mass tr acking with curve-fitting (BMT-F) and (4) fluid continuity method (FCM). We tested the flow algorithms with simulated angiograms and with images obtai ned from a programmable Bow phantom under clinically realistic flow and con trast injection conditions including imperfect mixing. All methods perform well for simulated angiograms. On phantom angiograms with constant flow, al l methods tended to underestimate flow velocities by at least 7% and demons trate high variability between consecutive measurements. The FCM demonstrat ed relatively low variability, but a large negative bias. The DDCM method w as moderately biased and had the highest variability. The BMT-F method demo nstrated the lowest bias (-7.1%) and the lowest variability both within (27 %) and between (27%) studies. No method yields reliable measurements near t he peak contrast opacification, when little or no gradient of contrast is p resent. The extrapolating version of the BMT-F method was also the most rob ust for estimation of interframe displacements longer than the field of vie w. (C) 1999 American Association of Physicists in Medicine.