The Retinal Diagram (aka funduscopic diagram) window is used to enter the height of the tumor apex and to digitize the tumor perimeter and (optionally) other landmarks such as blood vessels on the retinal surface. The recommended method is to digitize a calibrated fundus image. If you don't have a fundus collage, or the tumor is too anterior to photograph, you can still draw the tumor directly on the diagram based on size and location estimates derived from ultrasound and CT or MR imaging.
To dispose of an existing tumor perimeter, click the Clear button next to the Tumor button. You can move the entire tumor to any location on the diagram by placing the cursor into tumor drag mode and simply clicking within the tumor and dragging. The perimeter will circumferentially warp as appropriate to acount for radial position on the polar diagram. You can also control the shape of the tumor by draging the apex marker.
The following tutorial illustrates digitization of a posteriorly located tumor using a fundus collage and subsequent circumferential warping of the tumor and collage for correct mapping onto the polar retinal diagram.
Retina window set to Left eye with plaque, coordinate, and muscle displays disabled.
Note: for low altitude tumors such as this example (2.2 mm) it is advisable to set the Rx point at an altitude of about 4 to 5 mm in order to assure dosimetric coverage of the 2 mm margin surrounding the base.
Plaque Simulator's current auto-margin function is only able to properly expand spherical polygons that have convex perimeters.
For tumors with concave perimeters, such as illustrated on the right, you can manually edit the base margin to maintain the desired (e.g. 2 mm) spacing.