Background: Non-occlusive technique is universally accepted for acquisition of coronary optical coherence tomography (OCT), but the amount of contrast infused is still inconsistently calculated. Proposed herein, is an empirical formula for accurate contrast volume calculation.

Methods: In an observational prospective study, contrast volume of consecutive patients undergoing OCT was either calculated with formula, or eyeballed based on manufacturer recommendations. The quality of pullback, defined as % of high quality cross-sections (CS) in the segment of interest (SOI), was analyzed by two independent operators and compared between groups, together with the amount of contrast per pullback.

Results: Sixty patients (115 pullbacks, 4252 CS) were imaged using the formula, vs. 18 patients (22 pullbacks, 777 CS) eyeballing the contrast volume. The formula group used 18 mm/s as pullback speed more often (82.6% vs. 40.9%, p = 0.0001), but there were no significant differences between groups in SOI length or vessel imaged. The formula resulted in higher pullback quality than eyeballing (96.55% vs. 63.55%, p < 0.0001), interobserver agreement Kappa 0.903 (p < 0.0001), and tended to use less contrast per pullback than the eyeball group (13.03 mL vs. 14.55 mL, p = 0.057). After adjusting for pullback speed, SOI length and vessel in multivariate linear regression, the use of the formula significantly reduced the amount of contrast in 4.50 mL on average.

Conclusions: Optical coherence tomography acquisition with the non-occlusive technique can be substantially eased with the use of a novel formula to calculate the contrast volume required. This method optimises the quality of the images whilst reducing the amount of contrast per pullback.