This tutorial illustrates the use of Photoshop CS5 (newer versions of Photoshop will be similar) to create a rescaled fundus photo collage for export to Plaque Simulator with optional fusion of fluorescein angiography.
The final result is illustrated on the right. The 3 source images are illustrated below.
The sample source images may be found in the tutorial images section of the PS6 full download for version 6.1.9 or later (e.g. Plaque Simulator Folder/Plaque Simulator Data/(Tutorial Images)/PS6/Photoshop Tutorial/).
In this tutorial we will:
Fluorescein angiography is a technique for examining the circulation of the retina and choroid using a fluorescent dye and a specialized camera. In the fluorescein angiography image a choroidal melanoma typically shows a mottled hyperflourescence and diffuse late staining of the mass and its overlying subretinal fluid.
Fusing a fluorescein angiography image with the retinal collage can at times help to locate the fovea and to differentiate tumor from other forms of retinal damage that give an abnormal appearance to portions of the retina.
The pixel dimensions of images imported into PS6 (e.g. CT MPRs, ultrasound, fundus collages) should not exceed roughly 800 x 800 pixels. PS6 also expects all images to be initially calibrated at 72 dpi, ie each pixel being an OSX printer point of 1/72nd inch. PS6 can import and handle images that do not meet these specifications but interactive responsiveness will degrade, and PS6 patient file and .pdf document size could become very large.
In the Image Size window, observe that the original image dimensions of 2392x2048 pixels are much larger than required by Plaque Simulator. We should rescale the image to roughly 800 pixels wide at a resolution of 72 dpi. Begin by enabling the constrain proportions checkbox and setting the resample image menu at the bottom of the window to bicubic sharper.
Next, change the pixel dimensions and document size popup menus from pixels to percent. The width and height fields will change to read 100%. Then change the document size resolution from 100 to 72 pixels/inch.
Lastly change the pixel dimensions width from 100% to 33.33% (800 pixels is roughly 1/3 of the original width). Changing any text field will synchronize all the other fields when constrain proportions is enabled. Click the OK button to close the Image Size window.
Photo1.jpg just after opening in Photoshop CS5 is 2392 x 2048 pixels at 100 dpi. This is too large for efficient use in Plaque Simulator.
Photo1.jpg rescaled by 1/3 to 797 x 683 pixels at 72 dpi for best performance with Plaque Simulator.
Repeat the process for Photo2.
Photo2.jpg just after opening in Photoshop CS5 is 2392 x 2048 pixels at 100 dpi. This is too large for efficient use in Plaque Simulator.
Photo2.jpg rescaled by 1/3 to 797 x 683 pixels at 72 dpi for best performance with Plaque Simulator.
The file FluoresceinAngiography.jpg is already a good size for Plaque Simulator at 768x768 pixels. All we need to do is change the original dpi from 96 to 72. In the Image Size window, change the pixel dimensions and document size popup menus from pixels to percent. The width and height fields will change to read 100%.
Then change the document size resolution from 100 to 72 pixels/inch. Click the OK button to close the Image Size window.
To make a collage of the retina using the two photos we will convert the photos into Photoshop layers. By making one of the layers translucent we will use the optic disc and blood vessels as landmarks to assemble the collage.
To fuse the fluorescein angiography (FA) image with the fundus collage we will add the FA image as a translucent Photoshop layer and then rotate and rescale the FA layer to match the fundus collage using the disc and blood vessels as landmarks.
In the FluoresceinAngiography.jpg window of Photoshop:
In the recently created collage window (now titled fundus.jpg) of Photoshop:
To prepare the collage for export to plaque simulator we will next flatten the image from 3 layers down to a single layer, fill the extra space surrounding the collage with black, crop the image to fit the useful part of collage, and lastly save the collage as a .jpg file.
In the Photoshop tool palette: