ESTRO 2024 - Abstract Book

S3671

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

ESTRO 2024

Figure 1: Correlation Matrix for all evaluated parameters

Especially the correlation of resulting plan parameters (such as CI, Coverage, or Bridging dose) describing the plan quality with geometric factors that were somehow input parameters for plan creation (such as tumor volume, number of metastases, and the distance between lesions) was evaluated.

The impact of purely geometric factors, including distance to the isocenter, geometric depth, and distance to the adjacent metastasis, on the plan quality determining metrics (CI and Bridging Dose) is illustrated in Figure 2.

Smaller geometric depths (distances to the surface) of metastases result in greater benefits (absolute differences) in local CI with VMAT as opposed to DCA. Metastases situated near the surface offer the potential for improved treatment plan quality with VMAT due to the utilization of monitor unit modulation and the flexibility in aperture shape modulation, particularly benefiting from the use of 5mm leaves.

Likewise, the smaller the distance between a target and its nearest metastasis, the more pronounced the benefit (absolute difference) in bridging dose with VMAT in comparison to DCA.