Spectral optimization for measuring electron density by the dual-energy computed tomography coupled with balanced...

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Medical Imaging

Background:

• Dual-energy computed tomography (DECT) shows promise for electron density measurement in particle radiotherapy planning.
• Current DECT methods lack the precision required for accurate electron density determination in treatment planning.

Purpose of the Study:

• To develop and evaluate a novel DECT technique using a balanced filter method with a conventional X-ray tube.
• To optimize spectral parameters for precise electron density and effective atomic number imaging.

Main Methods:

• Calculated beam-hardening error and air kerma for spectral optimization of DECT with balanced filters.
• Utilized a cylindrical water phantom (50 cm diameter) and varied phantom sizes (5-50 cm).
• Selected optimal beam parameters including tube voltage and balanced filter materials (Tb/Hf, Bi/Mo).

Main Results:

• Optimized parameters predict effective electron density measurement with low beam-hardening errors (0.3% for electron density, 0.03% for effective atomic number) across phantom sizes.
• The balanced filter DECT method achieved 1/10th the beam-hardening errors of conventional DECT.
• The balanced filter method demonstrated higher effectiveness in electron density measurement despite a twofold increase in radiation dose.

Conclusions:

• The balanced filter DECT method offers a more effective approach for electron density measurement in particle radiotherapy planning compared to conventional DECT.
• Further advancements in low-exposure imaging and higher-output X-ray tubes are needed for clinical application.