The fundus collage is used to digitize the location, appearance, and perimeter of the tumor base on the retinal surface with respect to retinal landmarks that can also be identified in CT imaging space. In this way, the entire fundus collage can be fused with the CT based 3D model of the eye.
Two landmarks that are readily identifiable in fundus photography are the optic disc and macula. The location of the optic disc can be closely estimated in 3D CT (or MR) imaging space by reconstructing a meridian plane which bisects the eye and passes through the center of the optic nerve. This meridian plane, by definition, will also pass through the posterior pole of the eye. The posterior pole can be closely estimated in the fundus photos because the macula is adjacent to the pole.
Therefore, in order to accomplish the fundus-CT fusion, the fundus collage MUST contiguously include as much of the tumor as can be photographed as well as the macula and optic disc. Many fundus camera systems now provide collages in either printed or digital format. Best results in PS will be obtained if the background surrounding the collage is colored black as illustrated below.
Collage of 4 narrow field of view photos. This collage was provided as a .jpg file. This is the type of collage Plaque Simulator expects by default. Border space surrounding the images should be filled with true black (RGB = 0,0,0). Black pixels will become transparent when the images are applied to 2D and 3D surfaces.
If a camera provided collage is not available, a set of individual fundus photos can be imported into Adobe's Photoshop application. If the individual photos are provided in printed form, the prints can be scanned with a flatbed scanner (e.g. Epson Perfection series) and saved as .jpg files. Printed images can be scanned in 24 bit color or 8 bit monochrome.
Single wide angle photo that also came as a .jpg file. Plaque Simulator can handle wide angle photos by simply disabling the "autocorrect" feature when digitizing the tumor on the retinal diagram.
In this example a page of flourescein angiograms provided by an ophthalmologist were scanned in 8 bit monochrome (256 shades of gray) at 200 dpi using a flatbed scanner.
A "digital collage" of the fundus was prepared in Photoshop which includes the tumor, the optic disk and the macula.
This collage was saved in .jpg file format for subsequent importation into Plaque Simulator.
These are some now obsolete examples of suitable fundus images and collages which were prepared "manually" in the late 1980s by cutting & pasting real photographic prints and then scanned.