Novel application of an adapted virtual cone technique for the radiosurgical treatment of a 3 mm brain metastasis with a standard multileaf collimator.

The virtual cone is an innovative MLC-based technique for generating dose distributions comparable to those of physical stereotactic cones. Initially designed for functional radiosurgery applications using a high-definition multileaf collimator (MLC) with 2.5 mm leaf width, this technique has been adapted to a standard 5 mm MLC system for treating small brain metastases. The adapted technique uses preconfigured location-specific control point sequences to produce spherical dose distributions with sharp dose gradients, and facilitates efficient planning through parallelizable template-based workflows. This report highlights the use of the adapted virtual cone technique for treating a 57-year-old patient with a 3 mm brain metastasis from metastatic papillary thyroid carcinoma using a standard multileaf collimator.