ESTRO 2024 - Abstract Book

S3607

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

the prescribed dose. Roundness [5] and sphericity [6] of the lesions were calculated using 3D Slicer. A new coefficient, the asymmetry quotient (Q asym =ø max /ø eff ), was introduced to determine lesion asymmetry, relating the maximum lesion diameter (ø max ) obtained directly from planning software to the effective diameter of a volumetric equivalent sphere (ø eff ) derived from the PTV. To investigate the correlation between the dosimetric asymmetry parameters CI and DSI, Spearman's correlation was performed and data analysis was conducted using IBM SPSS.

Results:

Our analysis revealed that Q asym demonstrated a robust correlation with dosimetric properties of dose distribution such as CI and DSI over various volume categories (see Table 1).

Particularly for smaller volumes (categories 1 and 2), the correlation of Q asym with CI and DSI was significant and strong, indicating high sensitivity of the index to the effects of lesion asymmetry in these cases. For larger volumes (categories 3 and 4), all three asymmetry parameters (roundness, sphericity, Q asym ) correlated equally, suggesting consistent validity of these indicators in this regard. It is important to note that these correlations were found exclusively for DCA. Interestingly, VMAT showed generally no significant correlations with the asymmetry