Dual- and multi-energy CT: approach to functional imaging

Area of Science:

• Medical physics and imaging science
• Radiological physics

Background:

• X-ray photon energy spectra after absorbers reveal elemental composition, enabling tissue characterization.
• Dual-energy CT (DECT) differentiates materials by analyzing photoelectric and Compton effects using two X-ray spectra.
• DECT allows elemental concentration determination via three-material decomposition algorithms.

Purpose of the Study:

• To review the principles of dual- and multi-energy CT imaging.
• To discuss hardware approaches for these advanced CT techniques.
• To explore the clinical applications of multi-energy CT imaging.

Main Methods:

• DECT employs two X-ray spectra for material differentiation based on photoelectric and Compton interactions.
• Multi-energy CT (MECT) utilizes energy-sensitive photon-counting detectors to sample attenuation curves at multiple energy levels.
• MECT detects element-specific k-edge discontinuities in the photoelectric cross-section within narrow energy bands.

Main Results:

• MECT offers higher accuracy in concurrently identifying multiple materials compared to DECT.
• The detailed material distribution data from MECT provide insights beyond conventional morphological CT.
• MECT approaches the capabilities of functional imaging by providing specific material information.

Conclusions:

• Multi-energy CT imaging, particularly with photon-counting detectors, significantly enhances material differentiation and elemental analysis.
• These advanced CT techniques offer more detailed insights into tissue composition, moving towards functional imaging applications.
• The review covers fundamental principles, hardware, and clinical potential of DECT and MECT.