SU-E-I-38: Optimizing CT Slice Width Measurements.

Area of Science:

• Medical Imaging Physics
• Radiological Quality Assurance
• Computed Tomography (CT) Performance Evaluation

Background:

• Bead and wire ramps have been standard tools for CT slice width evaluation for nearly 40 years.
• These methods are established for quality assurance (QA) testing of CT scanners.
• Understanding their comparative performance and limitations is crucial for accurate CT imaging.

Purpose of the Study:

• To investigate the differences, advantages, and limitations between bead and wire ramps for CT slice width measurement.
• To evaluate the impact of varying field of view (FOV) and focal spot size on measurement accuracy and precision.
• To provide guidance on selecting the optimal ramp type and imaging parameters for different slice thicknesses.

Main Methods:

• Utilized the Catphan® 700 phantom, containing both bead and wire ramps, for direct comparison.
• Acquired 428 CT slices across various thicknesses (0.5-10 mm) using three different scanner models.
• Analyzed image data using Image Owl Catphan® QA software, including studies on FOV and focal spot variations.

Main Results:

• Bead ramps provided more accurate and precise thickness estimations for thin slices (0.5 mm).
• Wire ramps demonstrated superior precision for thicker slices (8-10 mm), while performance was comparable for 2-4 mm slices.
• Small FOV (100 mm) and small focal spot size significantly improved measurement accuracy, especially for thin slices with wire ramps.

Conclusions:

• For thin CT slices, bead ramps are recommended, particularly with a small FOV and small focal spot.
• For thick CT slices, wire ramps offer better precision, though bead ramps yield comparable average accuracy.
• The choice of ramp and optimization of imaging parameters are critical for precise CT slice width QA.