A study on the conversion of prescribed dose for radiotherapy of logistic nanodosimetry model and microdosimetric kinetic model based on gamma analysis / 中华放射肿瘤学杂志

ABSTRACT

Objective:To validate the feasibility of the gamma analysis method in the study of prescription dose conversion between logistic nanodosimetry model (LNDM) and microdosimetric kinetic model (MKM) basing on the Chinese self-developed model LNDM by applying clinical experiences of National Institute of Radiological Science (NIRS).Methods:Physical dose distributions derived from the MKM- and LNDM-based carbon ion treatment plans were compared via the method of gamma analysis under the open-source treatment planning platform matRad. In this way, the prescribed dose conversion factor between the MKM- and LNDM-based treatment plans was obtained. Using water phantoms, the influence of geometric shape, size, depth of target volume (TV), prescribed dose and field setting on the conversion factor was investigated comprehensively. Moreover, preliminary verification of the acquired conversion factor was conducted on the C-shape model and a case of liver cancer patient.Results:The conversion factor depended on the field setting rather than the TV shape. Under the condition of single field, the conversion factor was positively correlated with the size and depth of TV, and the prescribed dose. Moreover, the conversion factor was successfully verified using the C-shape model and the patient with liver cancer, where the gamma passing rates (2%/2 mm) of the physical dose distribution generated by the MKM and LNDM treatment plans were 92.79% and 91.19%, respectively.Conclusions:The conversion factors (f=D LNDM/D MKM) obtained in this study might provide guidance for the prescribed dose setting during the carbon ion treatment planning based on the LNDM. Besides, the gamma analysis method could be used for the study of the prescribed dose conversion between different models.