Clinical implementation of intensity-modulated arc therapy

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Intensity-modulated radiation therapy (IMRT) is a sophisticated radiation delivery technique.
• Intensity-modulated arc therapy (IMAT) utilizes rotational beams for IMRT delivery, with continuously changing field shapes.
• Clinical implementation and dosimetric evaluation of IMAT are crucial for its adoption.

Purpose of the Study:

• To clinically implement the intensity-modulated arc therapy (IMAT) technique.
• To evaluate the dosimetry of IMAT in comparison with conventional three-dimensional (3D) conformal techniques.

Main Methods:

• IMAT was planned using forward planning software, approximating arcs as multiple shaped fields.
• Conventional 3D conformal plans and inverse-planned fixed gantry IMRT plans were generated for comparison.
• Treatment delivery involved synchronized gantry rotation and multileaf collimator (MLC) motion, with dosimetric accuracy verified using phantoms and dry runs.

Main Results:

• IMAT achieved highly conformal dose distributions using two to five arcs.
• IMAT plans demonstrated superior target dose uniformity and reduced doses to normal structures compared to 3D conformal plans.
• Dosimetric accuracy was high, with measured doses within -0.54 +/- 1.72% of predicted doses and isodose contours matching predictions within 2 mm.

Conclusions:

• IMAT is a feasible and accurate technique for delivering highly conformal radiation doses.
• IMAT shows potential to rival slice-based and fixed-field IMRT techniques with optimized treatment planning.
• The efficient delivery using existing linear accelerators and MLCs makes IMAT a practical radiation therapy option.