Technical Note: Volumetric computed tomography for radiotherapy simulation and treatment planning

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Diagnostic Radiology

Background:

• Motion artifacts in 4D-CT scans, caused by small axial fields-of-view (aFOV), hinder accurate radiotherapy for lung and liver tumors.
• These artifacts can compromise treatment accuracy, leading to geographic misses and suboptimal dose calculations.

Purpose of the Study:

• To evaluate the utility of a 256-slice volumetric CT (vCT) scanner for 4D-CT simulation in radiotherapy.
• To assess the impact of a large aFOV on image quality and relative electron density (RED) curves for dose calculations.

Main Methods:

• Acquired 4D-CT images using a 256-slice vCT scanner with varying aFOVs (40-160 mm).
• Assessed image quality by evaluating CT number linearity, uniformity, noise, and low-contrast resolution.
• Correlated image quality metrics with aFOV to determine clinical significance.

Main Results:

• Image quality metrics were generally within expected ranges across different aFOVs.
• CT numbers for Teflon, Delrin, and air showed a statistically significant correlation with aFOV.
• Observed deviations in CT numbers were not clinically significant, indicating minimal impact on dose calculation.

Conclusions:

• Volumetric CT (vCT) with large aFOV is suitable for 4D-CT simulation in radiation therapy.
• vCT can potentially reduce motion artifacts, improving accuracy in radiotherapy planning.