Variation of patient dose in head CT

Area of Science:

• Medical Physics
• Radiology
• Radiation Dosimetry

Background:

• Computed tomography (CT) radiation dose is influenced by equipment and operator-dependent factors.
• Variations in CT dose can impact patient safety and diagnostic accuracy.
• Understanding these variations is crucial for optimizing CT examinations.

Purpose of the Study:

• To investigate the variability of absorbed dose in head CT scans.
• To quantify the differences in CT dose index (CTDI) and mid-scan dose (Dmid) across multiple CT scanners.
• To identify factors contributing to dose variations in clinical practice.

Main Methods:

• Thermoluminescence dosimetry (TLD) was used to measure absorbed dose in cylindrical and anthropomorphic head phantoms.
• Computed Tomography Dose Index (CTDI) and mid-scan dose (Dmid) were calculated for 14 different CT scanners.
• Dose profiles were analyzed to assess variations in radiation distribution.

Main Results:

• The mean CTDIw was 60.0 mGy and the mean Dmid was 45.8 mGy across 14 scanners.
• Normalized CTDIw and Dmid varied by up to a factor of 2.2 between scanners.
• Patient absorbed dose, particularly for the lens, could vary considerably (up to 16.2-fold) when considering all influencing factors.

Conclusions:

• Both equipment-related and operator-dependent factors significantly influence head CT radiation dose.
• Dmid provides a more representative measure of absorbed dose in human tissues compared to CTDIw.
• Standardization of CT scanning protocols and increased operator awareness are essential for dose reduction and patient safety.