Thanks to technical advances and the sophisticated radiation therapy units available today, we are able to administer highly sophisticated treatments with enormous precision. The problem is that the human body is not so precise and there are absolutely normal physiological movements in all the organs in our body. This variability in the location of each organ limits the precision of the treatment administered, producing a series of uncertainties and errors. Compensating for this situation means extending the margins of the treatment areas, and this inevitably involves irradiating more normal tissue than strictly necessary, producing more side effects and increasing the risk of long term effects.
These uncertainties and treatment-area margins can be reduced using image-guided radiation therapy, or IGRT. The special feature of this treatment technique is that each day, once the patient is placed on the treatment table and before beginning the session, the position of the organ to be treated and that of healthy neighbouring organs is checked and compared to the theoretical position where they should be. If everything is in the right place we can be sure that the treatment will be applied correctly and the session can begin. If the position is not correct and there is a displacement of 1 mm or more, the system analyses the differences and the treatment table is moved to compensate for them. Once the new position has been verified as correct, the corresponding fraction can then be safely administered.
With IGRT we can be sure that the treatment is applied exactly where it should be every day and that neighbouring healthy structures that are not to be subject to radiation are really outside of the field of irradiation. The great advantage is that the uncertainties practically disappear and so the safety margin that must be included around the organ being treated is minimal. This considerably reduces the amount of healthy tissue irradiated, thus improving treatment tolerance and reducing the frequency and seriousness of any side effects.