The problem faced by the group was to design a model that could simulate the same type of electrical properties of the breast. The model of the breast consisted of a long hollow plastic cylinder with a radius of 10 cm. A copper pipe was inserted into this cylinder.
The plastic cylinder represents the outer skin of a breast, the air inside the tube represents the fatty cells and lobes the breast consists of, and the copper pipe represents the tumor. Although the contrast between air and a copper tube is much higher than the contrast that would be found between real breast tissue and a tumor, the copper was used because the high contrast would give easily determinable test data.
For test purposes it was decided that the object to be illuminated with radiation would be rotated at different angles. The group decided that the object would be rotated with the use of stepper motors. One was used to rotate the test cylinder, and the other to raise and lower the object.
The testing of the drive control system commenced before the completion of the structure that would rotate the phantom breast model. The motors were wired independently of the structure and tested on the same DOS platform that would be used when the rotating structure would be completed. The testing was conducted under unloaded conditions with encouraging results. The drive program and motors performed as expected allowing for lifting and rotating sequences to be performed as expected.