pitch
In helical CT, the ratio of table advancement per rotation to the total beam collimation, affecting image quality and radiation dose.
Full Definition
Pitch in helical CT scanning refers to the ratio of table advancement per X-ray tube rotation to the total beam collimation width. A pitch of 1.0 indicates that the table advances exactly the width of the beam per rotation, providing optimal image quality with no gap or overlap in coverage. Pitch values less than 1.0 result in overlapping helical data, improving image quality but increasing radiation dose, while pitch values greater than 1.0 create faster scanning with potential gaps in coverage and reduced image quality. In oncologic CT protocols, pitch selection balances scan speed, image quality, and radiation dose considerations. Appropriate pitch selection is crucial for maintaining diagnostic image quality while optimizing patient throughput and dose management.
Usage
Usage note: Express as a decimal ratio (e.g., 0.8, 1.0, 1.5) without units.
In Context
- "Use a pitch of 1.2 for routine chest CT to balance speed and image quality." — CT protocol specification
- "Reduce pitch to 0.8 for high-resolution lung imaging to minimize artifacts." — Technical parameter adjustment