A simple knowledge-based tool for stereotactic radiosurgery pre-planning.

Area of Science:

• Medical Physics
• Radiation Oncology
• Neurosurgery

Background:

• Stereotactic radiosurgery (SRS) for intracranial lesions requires precise dosimetry to minimize normal brain tissue exposure.
• The volume of normal brain receiving at least 12 Gy (V12) is a critical predictor of radiation necrosis.
• Current methods for V12 assessment necessitate complete treatment plan generation, which can be time-consuming.

Purpose of the Study:

• To develop and validate a predictive model for estimating V12 in SRS plans.
• To provide a tool for setting realistic planning goals and parameters before treatment plan construction.
• To reduce planning time and resource utilization in SRS.

Main Methods:

• Retrospective analysis of 50 single-isocenter SRS treatment plans (collimator cone arc therapy - CAT).
• Re-planning cases using dynamic conformal arc therapy (DCAT) and applying scaling arguments for dose variations.
• Development of a phenomenological expression relating total V12 (TV12) to planning target volume (PTV) and prescription dose (PD).

Main Results:

• A predictive model was established to estimate TV12 as a function of PTV and PD for both CAT and DCAT plans.
• The relationship between conformity index (CI) and TV12 was elucidated, varying by plan type, PTV, and PD.
• The model allows for the suggestion of realistic planning parameters and goals prior to detailed plan creation.

Conclusions:

• The developed model offers a cost-effective method for estimating V12, aiding in the optimization of SRS treatment planning.
• This approach can guide clinicians in setting achievable dosimetric objectives, potentially reducing the incidence of radiation necrosis.
• The model is particularly valuable in settings lacking advanced pre-planning software, requiring minimal resources for implementation.