An automatic image processing algorithm for initiating and terminating intracoronary 
OFDI pullback

Intracoronary optical frequency domain imaging (OFDI) provides high resolution, three-dimensional views of coronary artery microstructure, but requires a non-occlusive saline/contrast purge to displace blood for clear artery views. Recent studies utilized manual pullback initiation/termination based on real-time image observation. Automated pullback initiation/termination by real-time OFDI signal analysis would enable more efficient data acquisition. We evaluate the use of simple imaging parameters to automatically and robustly differentiate between diagnostic-quality clear artery wall (CAW) versus blood-obstructed fields (BOF). Algorithms are tested using intracoronary OCT human data retrospectively and intracoronary OFDI swine and human data prospectively. In prospective analysis of OFDI swine data, the sensitivity and specificity of the ratio of second and first moments (contrast parameter) were 99.6% and 97.2%, respectively. In prospective analysis of OFDI clinical data, the contrast parameter yielded 96.0% sensitivity and 94.5% specificity. Accuracy improved further by analyzing sequential frames. These results indicate the algorithm may be utilized with intracoronary OFDI for initiating and terminating automated pullback and digital data recording.