A novel inverse optimization based three-dimensional conformal radiotherapy technique in craniospinal irradiation

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Craniospinal irradiation (CSI) is crucial for treating medulloblastoma.
• Traditional forward-planned 3D conformal radiotherapy (f3DCRT) faces challenges with field junctions and beam edge matching.
• Intensity-modulated radiotherapy (IMRT) offers improved dose distribution but can be complex.

Purpose of the Study:

• To develop and evaluate a novel inverse optimization-based three-dimensional conformal radiotherapy (i3DCRT) technique for CSI.
• To compare the dosimetric performance of i3DCRT against f3DCRT and IMRT.
• To assess the impact of patient positioning (supine vs. prone) on treatment planning.

Main Methods:

• Retrospective analysis of imaging data from 20 medulloblastoma patients (10 pediatric, 10 adult).
• Creation of three treatment plans per patient: i3DCRT, f3DCRT, and IMRT.
• Comparative evaluation based on conformity index, homogeneity index, and doses to organs at risk (OARs).

Main Results:

• i3DCRT demonstrated superior conformity and homogeneity compared to f3DCRT.
• i3DCRT achieved significant dose reductions to the esophagus and heart versus f3DCRT.
• i3DCRT provided dose distributions comparable to IMRT with lower monitor units per fraction (MU/fx) than IMRT and similar to f3DCRT.

Conclusions:

• The novel i3DCRT technique effectively addresses limitations of f3DCRT in CSI.
• i3DCRT offers a promising alternative, achieving IMRT-like plan quality with potentially reduced complexity and treatment time.
• This technique enhances OAR sparing and improves overall treatment plan quality for CSI.