Prepare the ultrasound measurements

Ultrasound is the most reliable method of measuring the shape of the tumor dome and altitude at the tumor apex. Sometimes tumor altitude can also be obtained from CT images if you can reconstruct a CT meridian slice which passes through the tumor apex. Fundus photos do not provide any altitude information at all.

Following the COMS convention, Plaque Simulator defines the altitude of the tumor apex as the distance from the inner sclera to the apex, and assumes the sclera is 1 mm thick under the tumor. Hence, the apex of a tumor of altitude 5 mm is actually 6 mm from the external sclera, and will also be 6 mm from the concave facial surface of a plaque assuming the plaque is touching the external sclera at the tumor base.

Ultrasound is also used to measure the nominal radial and circumferential dimensions of the tumor base. Tumor dimensions determined by ultrasound should be cross-checked with the dimensions obtained from fundus photos and CT imaging. If the various methods of measurement yield similar results you will have greater confidence in the validity of the model.

The most common tumor shapes are domes, peaks and mushrooms. Some examples are illustrated below.

Managing the size of ultrasound images

Try to keep the size of digitized ultrasound images under 1000x1000 pixels. If you scan the images yourself from hardcopy try a scanning resolution of 200 dpi or less. If you receive the images in electronic form such as .jpg files and the width is greater than 1000 pixels, use a program such as Adobe Photoshop to reduce the image size.


1. For example, lets say your original image arrives as a .jpg file that is 1920x1200 pixels at 150 dpi.


2. In the Photoshop image resizer, change the menus from pixels to percent, set the width and height to 50 (percent) and the resolution to 72 dpi (in MacOS a printer point is 1/72nd of an inch). Enable constrain proportions and select bicubic sharper from the lower menu. Click OK to exit the dialog.


3. The resulting image will be 960 x 600 pixels at 72 dpi. Its file size will be reduced from 6.59 MB to 1.65 MB. There is no advantage in Plaque Simulator to use images, be they MPRs, ultrasound, fundus, eye pictures or whatever... whose width or height exceeds 1000 pixels.

Dome shaped tumors

Peak shaped tumors

Mushroom and button shaped tumors