In the Image window, open and calibrate the fundus photo collage.

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.

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.

• Bring the Retinal Diagram window to the front by clicking the cursor in it.
• If it is not visible, select the Retinal Diagram item from the Window menu.

• If a calibrated fundus photo collage has been prepared, the Photo button in the Retinal Diagram tumor controls group will be functional.
• If the Photo button is disabled (ie dimmed) it means either you haven't yet calibrated the fundus image, you never opened a fundus image in the Image window or you accidentally put it into the wrong image buffer.
• Click the Photo button to add the collage to the diagram.
• The slider to the left of the Photo button adjusts the transparency of the collage background. The expected color of the collage background is black.
• Plaque Simulator will automatically select the approriate eye (ie left or right) based on the orientation of the fundus collage calibration tool.
• The optic disc in the photo should now be centered within the orange circle in the diagram and the posterior pole in the photo should be at the center of the diagram.

In the tumor controls group:

• Select tumor #1.
• Click the Clear button to delete the current tumor.

In the footer buttons group:

• Use the Zoom In function to enlarge and center the tumor in the window.

• In the tumor controls group click the Tumor button to begin tumor digitization.
• Move the cursor to an easily recognizable and convenient starting point on the tumor perimeter.
• Depress the mouse button, and begn tracing the perimeter of the tumor.
• Continue either clockwise or counter-clockwise. Counter clockwise is illustrated.
• Once tumor digitization has begun, you may optionally depress the mouse button continuously as you trace the perimeter, or you may release the button and digitize points individually by clicking on them. Digitization will continue until the polygon defining the tumor perimeter is closed.
• The perimeter polygon will automatically close when the cursor returns to the starting point.
• Alternatively, you can stop digitizing just short of the starting point and press the spacebar on the keyboard to autocomplete the polygon.

• For proper display on the polar retinal diagram, the pixels of the fundus collage must be circumferentially warped as a function of radial distance from the pole. Plaque Simulator (PS) defaults to doing this after the tumor has been digitized in order to preserve maximum image quality during the digitization process.
• Distortion of the original image is insignificant near the center of the retinal diagram, but becomes noticable at the equator and is very significant for locations in the anterior hemisphere.
• Once digitization of the tumor perimeter is complete, PS warps the tumor perimeter (if Auto Correct Tumor in the Diagram menu is enabled) and offers to warp the fundus collage for proper display on the retinal diagram.
• If you are finished with all retinal digitizations answer yes, otherwise you can manually warp the photo collage at a later time.

• In this example, the tumor was digitized using the original image, and then the tumor and image were circumferentially warped for correct mapping onto the polar diagram.
• The tumor apex defaults to the geometric center of the tumor base. You can move it elsewhere by enabling apex cursor mode and dragging it.
• Select the shape of the tumor (Peak, Dome or Mushroom) using the buttons in the tumor control group.
• By default, a 2 mm margin is automatically generated surrounding the tumor base. You can change the margin when setting the tumor apex height.
• Click the Apex button and enter the tumor height as measured from ultrasound studies.