Dynamic arc radiosurgery field shaping: a comparison with static field conformal and noncoplanar circular arcs

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiosurgery Techniques

Background:

• Advances in field-shaping technology and linac multileaf collimator (MLC) integration enable novel radiosurgery approaches.
• Stereotactic radiosurgery (SRS) aims to deliver precise high doses of radiation to target lesions while sparing normal tissue.

Purpose of the Study:

• To model and compare dose distributions from three SRS delivery techniques: conventional circular arcs, static conformal fields, and dynamic arc field-shaping.
• To evaluate the effectiveness of these techniques in achieving target coverage and minimizing dose to organs at risk.

Main Methods:

• A simulated target of overlapping spheres was used for planning simplicity.
• Three clinical cases with varying target sizes (0.50–9.79 cm³) and complexity (3–16 isocenters) were analyzed.
• Dose coverage (90% isodose for conformal/dynamic, 50% for circular) and sparing of normal brain/adjacent structures were primary goals.

Main Results:

• Conventional circular arcs with multiple isocenters result in significant dose heterogeneity for large/irregular targets.
• Static conformal and dynamic arc techniques achieve highly homogeneous target doses, similar to single isocenter approaches.
• Conformal techniques demonstrate reduced peripheral dose compared to multiple-isocenter circular arcs, especially with increased beams or arc angles.

Conclusions:

• Dynamic arc field-shaping is an efficient and accurate SRS method.
• This technique effectively delivers homogeneous target doses and minimizes peripheral dose to surrounding structures.