Estimating the resolution of a commercial optical coherence tomography system with limited spatial sampling

Optical coherence tomography (OCT) is becoming increasingly widespread as an experimental tool for clinical investigation, facilitated by the development of commercial instruments. In situ performance evaluation of such 'black box' systems presents a challenge, where the instrument hardware and software can limit access to important configuration parameters and raw data. Two key performance metrics for imaging systems are the point-spread function (PSF) and the associated modulation transfer function (MTF). However, previously described experimental measurement techniques assume user-variable spatial sampling and may not be appropriate for the characterization of deployed commercial instruments. Characterization methods developed for other modalities do not address this issue and rely upon experimental accuracy. Therefore, in this paper we propose a method to characterize the PSF of a commercial OCT microscope that uses OCT images of three-dimensional PSF phantoms to produce an oversampled estimate of the system PSF by combining spatially coincident measurements. This method does not rely upon any strong a priori assumption of the PSF morphology, requires no modification to the system sampling configuration or additional experimental procedure. We use our results to determine the PSF and MTF across the B-scan image plane of a commercial OCT system.