Intensity modulated arc therapy (IMAT) with centrally blocked rotational fields

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Techniques

Background:

• Intensity-modulated arc therapy (IMAT) offers precise radiation delivery.
• Classical blocks are used for shielding in radiotherapy.
• Combining IMAT with blocks can enhance dose modulation and critical structure protection.

Purpose of the Study:

• To propose and evaluate a new intensity-modulated beam (IMB) delivery technique.
• To combine IMAT features with classical blocks for improved radiation therapy.
• To assess the efficacy of this technique for treating annular target volumes with central critical structures.

Main Methods:

• Developed a new IMAT technique using centrally placed blocks to modulate intensity profiles.
• Applied linear optimization to precalculated dose profiles for segment determination.
• Utilized an analytical method to decompose rotational beam fluence profiles into subfields.
• Experimentally verified calculated dose profiles using radiotherapy films and phantoms.

Main Results:

• The proposed technique requires only three to seven segments for effective treatment.
• Achieved 95% dose coverage for the planning target volume (PTV).
• Maintained critical structure dose below 30% of the maximum dose.
• Experimental verification showed agreement within 5% for dose profiles.
• Demonstrated a total beam time of 77 seconds for a three-field irradiation.

Conclusions:

• The new IMAT technique with classical blocks is effective for specific treatment geometries.
• It offers precise dose modulation and superior critical structure sparing.
• The method is efficient, requiring few segments and minimal treatment time.
• This technique shows promise for generalization to patient treatments and offers advantages over existing conformal radiotherapy methods.