Spectral CT in radiotherapy: physics, principles, clinical applications, and future outlooks

Area of Science:

• Medical Imaging Physics
• Radiotherapy Technology
• Oncology Applications

Background:

• Conventional single-energy CT (SECT) struggles to differentiate materials with similar Hounsfield units.
• Previous reviews focused on physics and general oncologic uses of dual-/multi-energy CT.
• This review examines spectral CT specifically for radiotherapy applications.

Purpose of the Study:

• To evaluate spectral CT technologies and their radiotherapy-specific applications.
• To highlight spectral CT's role in simulation, contouring, dose calculation, and treatment monitoring.
• To discuss workflow implementation and quality assurance for spectral CT in radiotherapy.

Main Methods:

• Comprehensive literature review of spectral CT technologies.
• Summary of radiotherapy-specific applications: target delineation, dose calculation, functional evaluation, treatment response assessment, quality assurance, and clinical implementation.

Main Results:

• Spectral CT generates virtual monoenergetic images (VMI), iodine maps, and electron density (ED)/stopping power ratio (SPR) maps.
• Low-energy VMIs improve tumor delineation; high-energy VMIs reduce dose calculation uncertainties near implants.
• ED/SPR maps enhance dose planning accuracy; iodine quantification serves as a functional biomarker for tumor response.

Conclusions:

• Spectral CT advances precision radiotherapy with improved anatomical clarity and functional quantification.
• Challenges include quality assurance standardization, motion management, and treatment planning system integration.
• The combination of spectral CT and artificial intelligence promises personalized cancer treatment strategies.