An electronic device for digitizing radiotherapy films for the construction of tissue compensators

An electronic device was designed that measures film optical density and may be attached to the sonic pen of an x,y graphics terminal. Therapy portal films may be digitized by moving the assembly across the film by hand. Data is measured at a rate of 40 data points per second; hence, a large film can be digitized in about 5 min. Supporting computer software constructs a matrix array of optical densities covering the area of the film, converts optical density to dose, and plots tissue compensators. The concept of designing compensators from port films is reviewed. Phantom studies were performed to show that the compensators so designed are satisfactory for clinical application.