A spectral reconstruction algorithm for two-plane Compton cameras

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiation Oncology

Background:

• Hadron therapy requires real-time monitoring for precise treatment delivery.
• Current monitoring methods lack the reliability needed for widespread clinical adoption.
• Compton imaging systems offer potential for prompt gamma emission monitoring during irradiation.

Purpose of the Study:

• To develop and evaluate a spectral reconstruction method for prompt gamma imaging.
• To improve the extraction of spatial and spectral information from Compton imaging events.
• To assess the feasibility of real-time treatment monitoring in hadron therapy.

Main Methods:

• Implementation of a spectral reconstruction method within a list-mode maximum likelihood expectation maximization algorithm.
• Generation of a four-dimensional image in the joint spatial-spectral domain.
• Analytical modeling of system response and Monte Carlo integration for sensitivity calculation.

Main Results:

• The proposed method simultaneously recovers spectral and spatial information under ideal conditions.
• Monte Carlo simulations identified mispositioning and energy loss as key degradation factors.
• Accurate reconstruction of experimental point-like sources and identification of complex phantom distributions were achieved.

Conclusions:

• The spectral reconstruction method shows potential for prompt gamma imaging in hadron therapy.
• Detector limitations, specifically gamma interaction point mispositioning and energy loss, need to be addressed for clinical application.
• Further advancements are needed to overcome these limitations for realistic scenarios.