Visualisation of dynamic surface data for a patient display to reduce movement during radiotherapy

The accuracy of radiotherapy treatment is dependent on the ability of the patient to maintain a pre-planned, fixed position during each radiotherapy fraction. We present a new visual feedback device that will allow patients to assist in controlling and maintaining their position during both setup and treatment. We use an optical sensor system to gather real-time positional data about the patient during radiotherapy. When the mean-surface, calculated by taking optical data over a number of breathing periods, is subtracted from each sequential surface in a dataset the result is a simple flexing surface lamina. The movement of this lamina about the zero position indicates the deviation from the mean reference surface. This makes it an ideal, intuitive visualisation approach for describing the motion of a patient around their planned setup position. We present our method for determining individually achievable bounds for the patient motion and the use of simple threshold bars and colours to indicate those bounds to the patient. We also present a method for associating a body texture with the mean reference surface and the results of an early demonstration of the device with national patient representatives. Copyright © 2011 ACTA Press.