Ventilation measurements using fast-helical free-breathing computed tomography

Area of Science:

• Medical Imaging
• Pulmonary Function Testing
• Computational Anatomy

Background:

• Accurate lung ventilation measurement is crucial for diagnosing and managing respiratory diseases.
• Traditional methods like 4D CT and breath-hold scans have limitations, including sorting artifacts and inability to capture dynamic breathing processes.

Purpose of the Study:

• To evaluate the efficacy of multiple fast-helical free-breathing computed tomography (FHFBCT) scans for quantitative ventilation measurement.
• To compare the performance of a novel registration technique with a published method for ventilation analysis.

Main Methods:

• Ten patients underwent 25 FHFBCT scans with simultaneous real-time breathing surrogate monitoring.
• Regions-of-interest in the upper lungs were analyzed using a novel registration technique incorporating a conservation-of-mass criterion (ΔΓ).
• Voxel-by-voxel ventilation was calculated based on the Jacobian slope relative to breathing amplitude.

Main Results:

• The novel registration method significantly improved the conservation-of-mass criterion by nearly 50% compared to the published technique (ΔΓ reduced from 0.153 to 0.079).
• Ventilation patterns and magnitudes varied across patients, with minimal differences in average ventilation between registration methods.
• The secondary registration demonstrated improved correspondence between Jacobian and density ratios, indicating enhanced accuracy.

Conclusions:

• Multiple FHFBCT scans provide a viable method for free-breathing lung ventilation measurements.
• This approach overcomes limitations of 4D CT by eliminating sorting artifacts and offers benefits over breath-hold scans by capturing dynamic respiratory motion.
• FHFBCT enables characterization of dynamic breathing processes, offering a more comprehensive understanding of lung function.