Prof. Carl Bassi Profile

Prof. Carl Bassi

at Univ of Missouri-St Louis

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Publications (2)

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SPIE Journal Paper | 22 May 2015

Comparison of retinal image evaluation techniques in novice clinicians

Christopher Putnam, Alex Permann, Carl Bassi

JMI, Vol. 2, Issue 02, 025502, (May 2015) https://doi.org/10.1117/12.10.1117/1.JMI.2.2.025502

KEYWORDS: Pathology, Image analysis, Nerve, Photography, Optic nerve, Scanning electron microscopy, Computer simulations, Focus stacking software, Visualization, Macula

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Retinal fundus evaluation is learned through experience and training. This study aimed to determine the image presentation characteristics and the accompanying evaluation techniques, which led to the most accurate and efficient retinal pathology detection method. Phase I included 25 novice clinicians asked to evaluate 14 different pathologies using spatial versus temporal image presentations. Phase II included 25 different novice clinicians asked to evaluate five different simulated pathologies at three different pixel sizes presented in both spatial and temporal image presentations. Accuracy and speed of recognition were evaluated between the spatial and temporal presentations of the same simulated pathology. In phase l, subjects were significantly faster at simulated pathology detection using a temporal presentation with a 95% accuracy rate versus a spatial presentation with a 79% accuracy rate. In phase II, subjects demonstrated significant differences in speed of detection using the temporal technique at all 3 pixel number sizes with the greatest difference in detection times shown at the smallest retinal defects. Accuracy and speed of recognition in simulated pathology assessment were improved in a temporal presentation and the greatest improvements were demonstrated at the smallest pixel numbers.

Proceedings Article | 3 March 2010 Paper

Spectral characterization of an ophthalmic fundus camera

Clayton Miller, Carl Bassi, Dale Brodsky, Timothy Holmes

Proceedings Volume 7550, 75501U (2010) https://doi.org/10.1117/12.844855

KEYWORDS: Cameras, Sensors, Eye, Imaging systems, Retina, Photons, Reflectivity, CCD cameras, Xenon, Charge-coupled devices

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A fundus camera is an optical system designed to illuminate and image the retina while minimizing stray light and backreflections. Modifying such a device requires characterization of the optical path in order to meet the new design goals and avoid introducing problems. This work describes the characterization of one system, the Topcon TRC-50F, necessary for converting this camera from film photography to spectral imaging with a CCD. This conversion consists of replacing the camera's original xenon flash tube with a monochromatic light source and the film back with a CCD. A critical preliminary step of this modification is determining the spectral throughput of the system, from source to sensor, and ensuring there are sufficient photons at the sensor for imaging. This was done for our system by first measuring the transmission efficiencies of the camera's illumination and imaging optical paths with a spectrophotometer. Combining these results with existing knowledge of the eye's reflectance, a relative sensitivity profile is developed for the system. Image measurements from a volunteer were then made using a few narrowband sources of known power and a calibrated CCD. With these data, a relationship between photoelectrons/pixel collected at the CCD and narrowband illumination source power is developed.

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