An algorithm to calculate physical density of biomedical objects having 3 ≤ Z_eff ≤ 20: an application study using...

Area of Science:

• Medical Physics
• Radiology
• Biomedical Engineering

Background:

• Photon-counting computed tomography (PC-CT) offers advanced quantitative imaging capabilities for X-ray diagnosis.
• Conventional CT methods have limitations in providing detailed physical property information of biological tissues.
• Developing algorithms for accurate material decomposition is crucial for PC-CT applications.

Purpose of the Study:

• To propose and validate a novel algorithm for calculating the effective physical density (ρeff) of biological objects.
• To enable physical interpretation of contrast mechanisms in X-ray imaging using effective atomic number (Zeff) and ρeff.
• To demonstrate the algorithm's independence from substance-specific calibration.

Main Methods:

• Developed an algorithm to determine ρeff by fitting interaction cross sections to linear attenuation coefficients derived from virtual monochromatic images (VMIs).
• Integrated Zeff analysis, feeding back information to refine ρeff calculation.
• Validated the algorithm using a clinical PC-CT scanner with various phantoms and samples.

Main Results:

• The algorithm successfully calculated ρeff for water with a 4.5% uncertainty.
• Demonstrated that contrast factors can be physically interpreted using Zeff and ρeff, a capability beyond conventional CT.
• The procedure does not require calibration with specific substances, allowing analysis of diverse materials.

Conclusions:

• The proposed algorithm enables accurate ρeff calculation for biological objects using PC-CT data.
• This method allows for a deeper physical understanding of image contrast, moving beyond empirical CT values.
• The algorithm is expected to enhance diagnostic information in X-ray imaging, particularly with PC-CT and dual-energy CT systems.