Comparison of radiation and light field congruence between a developed collimator test tool and a standard collimator test tool in the general X-ray units of Lamphun Province hospitals

Abstract

Background: Assessment of radiation and light-field congruence is a key quality-control procedure for general X-ray machines. This process typically requires a standard collimator test tool, which can be costly. Therefore, the author developed an innovative collimator test tool as a cost-effective alternative for evaluating the congruence between the radiation field and the collimator light field.

Objectives: The present study aims to evaluate and compare radiation and light-field congruence measured using the developed collimator test tool and a standard tool on general X-ray units across eight hospitals in Lamphun Province.

Materials and methods: The developed collimator test tool was constructed from an etched stainless-steel plate measuring 20×25 cm, with scale resolutions of 2.5 mm and 5 mm. The standard collimator test tool (GAMMEX, Model 161B) is made from a brass plate of the same dimensions with a scale resolution of 5 mm. Measurements followed the 2023 diagnostic X-ray quality standards established by the Department of Medical Sciences, Ministry of Public Health. Radiation and light field borders were measured three times on each of four sides, yielding a total of 96 measurements. Error and percentage error were calculated, and a paired-sample t-test analysis was performed.

Results: Comparison of radiation and light-field congruence between the developed collimator and the standard collimator test tools revealed a maximum error of 0.5 mm, corresponding to a percentage error of 3%, which is below the acceptable limits of 1 mm or 5%. Statistical analysis using a paired-sample t-test (p<0.05) indicated no significant difference between measurements obtained from the two test tools (p≥0.05).

Conclusion: The developed collimator test tool can be used as an alternative to the standard tool for radiation and light field congruence testing in general X-ray units. It offers a cost-effective option for self-quality control and monitoring in radiology departments while maintaining the same measurement accuracy.