4D CT image acquisition errors in SBRT of liver identified using correlation.

Area of Science:

• Medical Imaging Physics
• Radiological Sciences

Background:

• Four-dimensional CT (4D CT) is a promising imaging modality for reducing respiratory motion artifacts.
• Accurate 4D CT reconstruction assumes a consistent correlation between internal organ movement and external surrogate signals.

Purpose of the Study:

• To evaluate the correlation between internal organ motion and external surrogate signals in 4D CT.
• To investigate the impact of breathing irregularities on this correlation and its implications for image quality.

Main Methods:

• Retrospective analysis of 21 4D CT scans from five patients.
• Utilized a real-tissue liver phantom with solid water and liver tissue for baseline correlation analysis.
• Correlated superior-inferior fiducial motion with anterior-posterior surrogate marker motion.

Main Results:

• High correlation coefficients (≥0.98) were observed with sinusoidal motion in phantoms.
• Patient data revealed instances of significantly decreased or lost correlation.
• Irregular breathing patterns and incorrect CT phase assignments were identified as sources of correlation disruption.

Conclusions:

• The correlation between internal organ motion and external surrogates in 4D CT can be compromised by non-regular breathing.
• Deviations in breathing patterns and improper phase assignments negatively impact 4D CT data accuracy.
• Daily patient-specific correlation analysis is crucial for detecting changes that affect image quality.