A practical method for measuring rotation angles in partial-angle CT scan by using CTDI phantoms, metal rods, and a...

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Dosimetry

Background:

• Partial-angle computed tomography (CT) is vital for image-guided interventions.
• Accurate X-ray tube rotation angle measurement is critical for dose evaluation in CT systems, especially during partial rotations (180°-240°).
• Existing methods lack reliability for measuring actual rotation angles in partial-angle CT scans.

Purpose of the Study:

• To propose and validate a method for measuring rotation angles in partial-angle CT scans.
• To improve dose evaluation accuracy by integrating measured angles into Monte Carlo simulations.
• To enhance quality assurance for rotation angles and promote appropriate dose management in CT procedures.

Main Methods:

• Developed a technique using metal rods within a CT dose index phantom to measure X-ray attenuation and determine rotation angles.
• Incorporated measured angles and dose profiles into Monte Carlo simulations for validation.
• Performed measurements using CT fluoroscopy and angiography systems.

Main Results:

• The proposed method demonstrated small discrepancies between displayed and measured rotation angles (3.4% for CT fluoroscopy, 8.1% for angiography).
• Dose evaluation accuracy improved, with maximum discrepancies reduced by 9.0% for CT fluoroscopy and 4.8% for angiography compared to conventional methods.
• Validated the accuracy of Monte Carlo simulations against measured dose profiles and rotation angles.

Conclusions:

• The novel method provides reliable rotation angle measurement for partial-angle CT scans.
• This technique significantly enhances the accuracy of dose evaluation in CT fluoroscopy and angiography.
• Facilitates quality assurance and supports appropriate radiation dose management in interventional radiology.