An efficient rectangular optimization method for sparse orthogonal collimator based small animal irradiation.

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Preclinical Research

Background:

• Intensity-modulated radiotherapy (IMRT) is crucial for clinical cancer treatment, requiring accurate preclinical models.
• Small animal IMRT faces hardware and software challenges for miniaturized targets.
• Sparse orthogonal collimators (SOC) offer a simplified hardware approach for small animal IMRT.

Purpose of the Study:

• To investigate and evaluate a significantly improved rectangular aperture optimization (RAO) algorithm for complex mouse irradiation using SOC.
• To enhance computational performance and accelerate the optimization process for small animal IMRT planning.

Main Methods:

• Reformulated matrix multiplication in the data fidelity term to avoid Kronecker products, improving computational efficiency.
• Employed the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA) to accelerate the optimization problem.
• Evaluated the improved algorithm on four mouse cases, including liver, brain tumor, U-target, and total marrow irradiation (TMI).

Main Results:

• sIMRT plans showed comparable planning target volume (PTV) statistics (within 1%) to idealistic IMRT for simpler targets.
• For TMI, sIMRT significantly reduced PTV and organ-at-risk (OAR) hot spots (Dmax) by up to 31.5%.
• sIMRT achieved comparable conformity to idealistic IMRT with minor increases in R50 and Integral Dose.

Conclusions:

• The improved sIMRT optimization method enables rapid plan creation (<1 min) for small targets.
• Complex total marrow irradiation (TMI) planning is feasible with this advanced sIMRT approach.
• This method achieves dosimetry comparable to idealistic IMRT, advancing preclinical radiotherapy research.