Zernike morphological description of dose distributions in radiotherapy and radiosurgery

Dose conformity is a key parameter in radiotherapy and radiosurgery, measuring the correspondence between the dose distribution generated by a Treatment Planning System (TPS) and the target volume to be treated, the Planning Target Volume (PTV). In this work, we propose a method based on the expansion of dose distributions and PTVs using three-dimensional Zernike polynomials, with conformity quantified through comparison of their moments. For this study, and for the purpose of treatment plan comparisons, data from 20 patients comprising 80 datasets exported from the TPS were analyzed. These datasets included imaging data (PTVs) and dose distributions corresponding to three treatment modalities: three-dimensional conformal radiotherapy, intensity-modulated radiotherapy (IMRT), and volumetric modulated arc therapy (VMAT). The Zernike framework enables the definition of a parameter space in which a metric can be established to quantify differences among treatment plans. To calibrate this metric and its relation to treatment efficiency, both radiosurgery and radiotherapy datasets also were used. The results show that the distance in parameter space decreases as treatment efficiency increases, indicating that this metric provides a suitable measure for quantifying efficiency. Overall, the proposed method introduces a systematic approach for analyzing dose distributions, with potential extensions to applications in artificial intelligence.