Light beam diaphragm collimation errors and their effects on radiation dose for pelvic radiography

Area of Science:

• Medical Imaging Physics
• Radiological Sciences
• Radiation Protection

Background:

• Accurate X-ray beam collimation is crucial for minimizing patient radiation dose.
• Collimation errors can lead to unnecessary radiation exposure and compromised image quality.
• Understanding the extent and impact of collimation errors is essential for quality assurance in diagnostic radiology.

Purpose of the Study:

• To quantify collimation errors in X-ray rooms during anteroposterior pelvic examinations.
• To determine the impact of identified collimation errors on radiation dose, specifically Dose Area Product (DAP).

Main Methods:

• Collimation errors were assessed using a test tool at various heights simulating patient thickness in nine X-ray rooms.
• Simulated collimation errors (-27% to 18%) were applied to a pelvic phantom to measure DAP changes.
• Standard anteroposterior pelvic radiography techniques were employed with automatic exposure control.

Main Results:

• Most X-ray machines exhibited smaller irradiated fields than visually set, with errors ranging from -16% to +0.4%.
• Simulated field size increases of 1 cm in the superior/inferior plane increased DAP by 5%, while lateral increases raised DAP by 4%.
• Combined increases in both planes resulted in a 4% DAP rise.

Conclusions:

• Collimation errors in the studied clinical setting were minimal, predominantly resulting in underirradiation.
• Even minor collimation inaccuracies can significantly influence DAP, with greater impact in the superior/inferior axis.
• Further multi-center studies are recommended, but findings suggest adherence to strict radiation safety regulations.