Modulation transfer function measurement of scanning reflectance microscopes.
Real-time medical imaging systems such as reflectance confocal microscopes and optical coherence microscopes are being tested in multiple-patient and multiple-center clinical trials. The modulation transfer function (MTF) of these systems at any given time influences the image information content and can affect the interpretation of the images. MTF is difficult to measure in real-time scanning systems when imaging at the Nyquist limit. We describe a measurement technique similar to the electronic imaging resolution standards ISO-12233 (electronic cameras) that can be applied to scanned spot imaging systems with asynchronous pixel clocks. This technique requires the acquisition of a single image of a reflective stripe object. An asynchronous pixel clock induces subpixel jitter in the edge location. The jitter is removed using a Fourier method, and an oversampled edge response function is calculated using algorithms developed in MATLAB. This technique provides fast, simple to use, and repeatable full-width at half maximum lateral resolution and MTF measurements based on only one test image. We present the results for reflectance confocal microscopes operating at 0.9 numerical aperture.
Wang
Zhao
Z
University of Rochester, Department of Biomedical Engineering, Wilmot Building, Rochester, New York 14627, USA. zhaowang@bme.rochester.edu
Glazowski
Christopher E
CE
Zavislan
James M
JM
D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000379:methods* / Q000592:standards*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000592:standards*; D018613:Microscopy, Confocal / Q000295:instrumentation* / Q000592:standards*; D019047:Phantoms, Imaging / Q000592:standards; D011785:Quality Assurance, Health Care / Q000592:standards*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States