Goals and Clinical Benefits

The goal of the IGRT process is to improve the accuracy of the radiation field placement, and to reduce the exposure of healthy tissue during radiation treatments. In years past, larger planning target volume (PTV) margins were used to compensate for localization errors during treatment. (Jaffray et al. 1999) This resulted in healthy human tissues receiving unnecessary doses of radiation during treatment. PTV margins are the most widely used method to correct geometric uncertainties. By improving precision and accuracy through IGRT, radiation is decreased to surrounding healthy tissues, allowing for increased radiation to the tumour for control. (Jaffray et al. 1999)

Currently, certain radiation therapy techniques employ the process of Intensity Modulation Radiotherapy. (IMRT) This form of radiation treatment uses computers and linear accelerators to sculpt a three-dimensional radiation dose map, specific to the target’s location, shape and motion characteristics. Because of the level of precision required for IMRT, detailed data must be gathered about tumour locations. The single most important area of innovation in clinical practice is the reduction of the planning target volume margins around the location. The ability to avoid more normal tissue and/or employ dose escalation strategies is a direct by-product of the ability to execute therapy with the most accurate geometric precision. (Jaffray et al. 1999)

IGRT will continue to increase the amount of data collected throughout the course of therapy. Over the course of time, whether for an individual or a population of patients, this information will allow for the continued assessment and further refinement of treatment techniques. The clinical benefit for the patient is the ability to monitor and adapt to changes that may occur during the course of radiation treatment. Such changes can include tumour shrinkage or expansion, or changes in shape of the tumour and surrounding anatomy. (Jaffray et al. 1999)