Four-dimensional intensity-modulated radiotherapy planning for dynamic multileaf collimator tracking radiotherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-guided radiotherapy

Background:

• Respiratory motion significantly challenges precise tumor targeting in radiotherapy.
• Dynamic multileaf collimator (DMLC) technology offers potential for real-time tumor tracking.
• Accurate dose delivery requires accounting for intra-fractional motion.

Purpose of the Study:

• To develop a four-dimensional intensity-modulated radiotherapy (4D-IMRT) planning method for DMLC-based tumor tracking.
• To incorporate respiratory motion into the IMRT planning process.
• To optimize aperture shapes and leaf movements for dynamic tumor tracking.

Main Methods:

• Utilized optimal deformation concept for aperture placement across respiratory phases.
• Employed a direct aperture optimization (4D-DAO) method.
• Integrated simulated annealing and conjugate gradients algorithms for segment shape and monitor unit optimization.
• Validated against simulated and real 4D computed tomography (4DCT) data, comparing with 3D conformal radiotherapy (3DCRT).

Main Results:

• The 4D-DAO method significantly improved dose distribution compared to 3DCRT.
• Enhanced dose conformity and normal tissue sparing were observed.
• The technique remained effective even with DMLC leaf velocity limitations.

Conclusions:

• The proposed 4D-IMRT planning method enables effective tumor motion tracking.
• The approach optimizes segment shapes and leaf trajectories for dynamic treatment.
• This method enhances normal tissue protection during radiotherapy for moving tumors.