Applications of two-step intensity modulated arc therapy

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Organs at risk (OARs) are often located within or adjacent to target volumes, posing a challenge for dose delivery.
• Conventional radiotherapy techniques may compromise OAR sparing or target coverage when OARs are surrounded by the target volume.

Purpose of the Study:

• To introduce and evaluate a novel "two-step intensity modulated arc therapy" (two-step IMAT) method.
• To demonstrate the feasibility of achieving dose homogeneity in concave target volumes while sparing adjacent organs at risk.

Main Methods:

• The two-step IMAT involves a primary rotational technique to reduce dose to the OAR.
• A secondary, narrow rotational field is applied tangentially to the concave target, enhancing dose in that region.
• This approach aims to homogenize dose distribution without significantly increasing OAR dose.

Main Results:

• The two-step IMAT method successfully achieved sufficient dose homogeneity in target volumes surrounding OARs.
• Demonstrated applicability in diverse clinical scenarios, including head and neck tumors, spinal cord proximity cases, and breast cancer patients with challenging chest wall anatomy.
• Modifications of the technique further ensured adequate dose distribution.

Conclusions:

• Double rotation techniques, such as two-step IMAT, provide effective dose homogeneity for concave targets.
• These methods offer excellent sparing of adjacent organs at risk.
• The technique is time-efficient and a viable alternative until widespread routine use of intensity-modulated radiation therapy (IMRT) is feasible.