(Linear Accelerator of the Varian brand and TrueBeam type equipped with an advanced imaging system MV, KV, and CBCT and a PerfectPitch table with 6 degrees of freedom (6DoF) with two additional rotational axes, pitch, and roll, facilitating movements centered on the isocenter, we can administer very sophisticated treatments with a high level of precision and reproducibility.
In fact, the human body is not as precise; indeed, all organs in our body exhibit completely normal physiological movements. This variability in the position of each organ limits the precision with which the treatment can be administered, leading to a series of uncertainties and errors. To compensate for these, the treatment field margins need to be widened, which inevitably implies irradiating more normal tissue than strictly necessary, causing more side effects and increasing the risk of long-term sequelae.
To reduce these uncertainties and the treatment field margins, image-guided radiotherapy (IGRT) is used. The peculiarity of this treatment technique is that, each day, once the patient is placed on the treatment table and before the corresponding session is carried out, the position of the organ to be treated and the surrounding healthy organs is verified and compared with the theoretical position they should be in. If the position is correct, we are reassured about the proper execution of the treatment and proceed to administer the corresponding session. If the position is not correct and the displacement is equal to or greater than 1 mm, the system analyzes the existing displacements and the movements of the treatment table needed to compensate for them. Once the table movements are performed, the new position must be verified as correct, and if so, the corresponding fraction is then delivered.
Thanks to IGRT, we are assured that the treatment is carried out each day in the desired location and that the surrounding healthy structures, which should not be irradiated, are truly situated outside the irradiation fields. The major advantage is that uncertainties are almost eliminated, meaning that the safety margin around the organ to be treated is minimal, and the amount of healthy tissue irradiated decreases significantly; this results in improved treatment tolerance and a reduction in the frequency and severity of side effects.
