Four-Dimensional Dose Reconstruction for Scanned Proton Therapy Using Liver 4DCT-MRI

Area of Science:

• Medical Imaging
• Radiation Oncology
• Computational Anatomy

Background:

• Four-dimensional computed tomography-magnetic resonance imaging (4DCT-MRI) is an advanced image-processing technique.
• It simulates multiple 4D computed tomography (4DCT) datasets using static CT data and motion information from 4D MRI.
• This technique is valuable for motion modeling in radiation therapy.

Purpose of the Study:

• To evaluate different motion extraction approaches for 4DCT-MRI.
• To compare the accuracy of 4DCT-MRI against traditional 4DCT using liver cases.
• To assess dosimetric agreement for radiation dose calculations.

Main Methods:

• Generated 4DCT-MRI using two methods: subject-specific motion from 4DMRI and population-based motion from a volunteer library.
• Compared generated 4DCT-MRI datasets with 4DCT using scanned proton 4D dose calculations (4DDC).
• Utilized gamma analysis (3%/3 mm) to assess dosimetric agreement within the clinical target volume (CTV).

Main Results:

• Subject-specific 4DCT-MRI achieved high dosimetric agreement (93% ± 8%) with 4DCT within the CTV.
• The population-based approach showed significantly lower agreement (79% ± 14%) with 4DCT.
• These findings highlight differences in accuracy between the two motion modeling strategies.

Conclusions:

• 4DCT-MRI enhances motion modeling for dose calculations by incorporating realistic motion patterns.
• Subject-specific liver modeling in 4DCT-MRI is more accurate than population-based methods.
• Subject-specific 4DCT-MRI is promising for clinical applications like improved target delineation and patient-specific quality assurance.