A deconvolution approach for PET-based dose reconstruction in proton radiotherapy

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Nuclear Imaging

Background:

• Proton radiotherapy utilizes proton beams, leading to activated positron emitters for dose verification via positron emission tomography (PET).
• PET images are not directly proportional to radiation dose, necessitating methods to compare predicted and measured images for treatment verification.
• Current PET prediction methods rely on Monte Carlo simulations or filtering approaches involving dose convolution.

Purpose of the Study:

• To develop and evaluate a dose reconstruction method that reverses the convolution-based PET estimation approach.
• To address the challenges of deconvolution as an ill-posed inverse problem using regularization techniques.
• To generalize the dose deconvolution method for both homogeneous and inhomogeneous media and account for multiple positron emitters.

Main Methods:

• A deconvolution approach was developed to reverse the convolution-based PET estimation of radiation dose.
• Regularization techniques were employed to ensure stable solutions for the ill-posed deconvolution problem.
• The method was extended to handle inhomogeneous media and incorporate the influence of short-lived positron emitters in PET imaging.

Main Results:

• The dose reconstruction method successfully reversed PET estimation in simulations for both homogeneous and inhomogeneous media.
• The method demonstrated robustness despite noise and artifacts present in measured PET images.
• Simulations confirmed the extended method's capability to process PET images with multiple positron emitters.

Conclusions:

• The developed dose reconstruction method provides a viable approach for accurate dose verification in proton radiotherapy using PET imaging.
• The method's ability to handle complex scenarios, including noise, artifacts, and multiple emitters, enhances its clinical applicability.
• Further validation with experimental data is warranted to fully establish the clinical utility of this deconvolution-based dose reconstruction technique.