Phase-selective image reconstruction of the lungs in small animals using Micro-CT

Area of Science:

• Medical Imaging
• Small Animal Imaging
• Micro-Computed Tomography (micro-CT)

Background:

• Physiological motion, such as respiration, causes artifacts in small animal imaging.
• Existing methods for motion compensation often require additional hardware or complex setups.
• High-quality imaging of rodent lungs is crucial for preclinical research, especially in oncology.

Purpose of the Study:

• To develop and validate a novel strategy for motion-uncompensated sampling and image reconstruction in rodent lung micro-CT.
• To enable phase-selective reconstruction of respiratory cycles without external respiratory gating hardware.
• To improve image quality and reduce artifacts in micro-CT scans of free-breathing mice.

Main Methods:

• Rapid micro-CT sampling of free-breathing mice without respiratory gating hardware.
• Post-acquisition analysis of projection images to derive a respiratory signal.
• Application of weighting factors based on the respiratory signal to favor specific respiratory phases (e.g., end-inspiration, end-expiration).
• Utilizing an iterative reconstruction algorithm, Simultaneous Algebraic Reconstruction Technique with Total Variation minimization (SART-TV), for image reconstruction.
• Implementation of the SART-TV algorithm on a graphics processing unit (GPU) for reduced reconstruction time.
• Validation through simulations and in vivo scans of mice with primary lung cancers using a dual tube/detector micro-CT system.

Main Results:

• The proposed method successfully derives a respiratory signal from projection data post-acquisition.
• Iterative reconstruction using SART-TV with phase-selective weighting effectively compensates for respiratory motion artifacts.
• Reconstructions favoring specific respiratory phases were achieved despite uncorrelated sampling and respiratory cycles.
• The GPU implementation significantly reduced reconstruction time.
• The approach demonstrated feasibility in preclinical lung cancer imaging in mice.

Conclusions:

• A novel, hardware-free gating strategy for rodent lung micro-CT imaging has been presented.
• The SART-TV iterative reconstruction algorithm combined with phase-selective weighting effectively overcomes physiological motion artifacts.
• This technique offers improved image quality for small animal lung imaging and has potential applications in cardiac imaging if ECG is acquired.