The effect of the tongue and groove of the multileaf collimator on dose distribution: examination of results of measurements and treatment planning system

Abstract

Multileaf collimators play an important role in the field of radiotherapy and are widely used today. The effect of multileaf collimator structure on dose distribution should be well investigated and whether treatment planning systems reflect these effects on dose distribution should be examined. In our study, we examined the effect of tongue-and-groove on irregular fields and intensity-modulated radiotherapy plan. We also investigated the depth dependence of the tongue-and-groove effect. All fields are created in RayStation treatment planning system. Data obtained from treatment planning systems were compared with data obtained with 2-dimensional dose-measuring devices. We found the tongue-and-groove effect consistent in both measurements in single field measurements. We calculated dose reductions due to tongue-and-groove effect between 6% and 14%. When we examined the tongue-and-groove effect at different depths, we observed that the tongue-and-groove effect decreased as the depth increased. Although the tongue-and-groove effect did not create significant results on the dose distribution in multi-field use, we observed that this effect could occur at the edge of the field. Dose differences due to multileaf collimator structure should be examined by clinics. In addition, the extent to which treatment planning system takes these effects into account should be checked with some measurements. Otherwise, undesirable dose differences may be seen in the patient.