Abstract
Purpose::
To obtain quantitative fluorescein angiograms that are independent of instrument setup and operator influence.
Methods::
Sets of five standard fluorescein solutions were developed that mimic the environmental conditions of the plasma and vitreous compartments of the eye. Images of the eye fundus (after patient dye administration) and these sets of standard fluorescein solutions were simultaneously obtained at different focal planes via a beam splitter and lens system that was attached to an HRA scanning laser ophthalmoscope (Heidelberg Instruments Inc., Heidelberg, Germany) which allowed establishment of calibration plots at the same instrument settings that imaged the eye. Software was developed that calculated the calibration plots and used them to convert the angiography gray-scale images into absolute concentration image maps for both the vitreous and the plasma compartments. The quality of the concentration image maps were determined by the software by calculating the instrument performance parameters, i.e., linearity, detection threshold, dynamic range and windows of analysis from each of the calibration plots. This methodology provided calibration data for both the plasma and vitreous compartments with each image that is obtained.
Results::
Our results revealed that the concentration image maps generated by the system described in the method section were independent of the instrument setup and operator. Furthermore, the concentration maps were comparable over time for the same patient and between patients imaged either in the same or different laboratories.
Conclusions::
This methodology provides a breakthrough in fluorescence angiography in that it allows direct comparison between different fluorescein angiograms either from the same patient over time or across patients and laboratories.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical • image processing