Virtual reality in external beam and brachytherapy radiation therapy planning and practice

Planning volume definition, organs at risk contouring and dose distribution calculation in the treated volume are the steps which must be performed for each patient who need to be treated with external beam radiation therapy or brachytherapy. In the past, when only 2D treatment planning systems were available simulation was done on patient's contours drawn using pantographs or similar devices. For external beam radiation it was also possible to shield some areas of the treating fields with cerrobend blocks to avoid to irradiate organs at risk. More recently single CT slices have been used to plan the treatment, but only since when computerized 3D rendering and planning software are available a full rendering of treatment planned volume, organs at risk and calculated isodose is possible. All these steps must be simulated before therapy will start and modern software give us today the opportunity to simulate the whole treatment: beams shape, entrance angles and linear accelerator movements for external beam radiotherapy or sources number and position for brachytherapy. We can virtually simulate also customized fields of treatment we use to shield organs at risk and the distribution of the dose on the "virtual body" of the patient who contains the "virtual target". These parameters can also be modified and we can look to the changes occurred to beam position and shape or to dose distribution in real time. This application of "virtual reality" is called "virtual simulation" and represents one of the most important tools in radiotherapy practice. Actually safe and efficient radiation oncology could not be performed without it.