Dual energy imaging using a clinical on-board imaging system

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Radiological Sciences

Background:

• Dual energy (DE) imaging uses two X-ray energies to create enhanced soft tissue contrast images.
• While established in diagnostic radiology for lung malignancy detection, DE imaging is not yet clinically used in radiotherapy.
• Image-guided radiotherapy (IGRT) requires precise tumor localization, where improved soft tissue visualization is beneficial.

Purpose of the Study:

• To evaluate the feasibility of implementing DE imaging on a commercial on-board imaging system for radiotherapy applications.
• To determine optimal imaging parameters for DE subtraction to maximize tumor detectability.
• To assess the potential of DE imaging to improve soft tissue contrast for lung cancer patients undergoing IGRT.

Main Methods:

• Construction of simple and anthropomorphic phantoms for DE imaging analysis.
• Acquisition of planar kilovoltage (kV) X-ray images at varying energies and milliampere-seconds (mAs).
• Development of software for DE image subtraction and quantitative assessment of tumor detectability using signal-difference-to-noise ratio (SDNR).

Main Results:

• DE subtraction effectively suppressed high-density objects in both phantoms.
• The optimal imaging parameters identified were 140 kVp (1.0 mAs) and 60 kVp (3.2 mAs).
• This technique achieved a higher SDNR than the reference technique at a comparable or lower radiation dose.

Conclusions:

• DE imaging is feasible using a commercial on-board imaging system for radiotherapy.
• The developed DE subtraction technique can enhance soft tissue visualization.
• This approach holds potential for improving tumor detection and visualization in image-guided lung cancer radiotherapy.