CTDIvol and DLP are the two most commonly used metrics for quantifying patient radiation dose in CT. Multiple technical strategies exist for minimising radiation exposure during CT examinations.

Dose Indices: CTDIvol and DLP

Term Definition & Calculation Clinical Relevance
CTDIvol Volume CT Dose Index — reflects average dose per slice within the scanned volume, accounting for helical pitch. Calculated as: CTDIw/pitch Measures dose intensity of the scan protocol for standardized phantoms
DLP Dose-Length Product — quantifies total exposure, calculated as: CTDIvol × scan length (cm) Estimates total amount of radiation imparted to the patient over the scanned region

Techniques to Control CT Radiation Dose

Technique Key Principle
Tube Current Reduction Lowering mA reduces dose linearly. Adjust for patient size.
Tube Current Modulation Automated adjustment of mA in real time based on patient attenuation.
Voltage (kVp) Reduction Using lower kVp for appropriately sized patients, notably in pediatrics.
Higher Pitch Higher table speed reduces dose, especially in helical CT.
Scan Range Limitation Restricting scan length to clinical area of interest only.
Iterative Reconstruction Allows diagnostic image quality at lower dose by reducing noise.
Avoiding Unnecessary Scans Referrals should be justified; alternative modalities (US/MRI) preferred when suitable.
Single-Phase over Multi-Phase Use the fewest necessary scan phases; avoid routine pre/post and delayed series unless indicated.

Summary: