Dose management for X-ray and CT: Systematic comparison of exposition values from two institutes to diagnostic reference levels and use of results for optimisation of exposition

Abstract

Purpose: In 2 institutions exposure values were evaluated and compared with the 2010 updated diagnostic reference levels (DRL) and possibilities for decreasing the dose assessed. Materials and Methods: Mean exposure values obtained during a 3-month period were calculated for all modalities (X-ray: imaging plate system and digital detector; dual-source 64- and 16- slice spiral CT) as well as examination types were compared to old diagnostic reference levels in addition to DRLs introduced in 2010. Then 10 examinations of all modalities and types were accompanied by a medical physicist and optimized stepwise if necessary. Results: The mean values of X-ray examinations were above DRL. All accompanied examinations were beyond DRL except lateral lumbar spine (LSP) and lateral thoracic X-ray, which were elevated due to statistical outliers from morbidly obese patients or patients with metallic implants. For a-p LSP tube voltage was increased. While image quality was maintained, dose area product (DAP) was reduced by 50% to123±61 cGy·cm2 for LSP a-p and 30% for lateral LSP to 229±116 cGy·cm2. For CT examinations, dose was below DRL. Accompanied examinations of the lumbar spine performed on a 16-slice spiral CT demonstrated a result 68% above DRL with dose length product (DLP) of 840±252 cGy·cm. For optimization, pitch and tube voltage were stepwise increased and DLP reduced below DRL. Conclusion: Systematic analysis of our internal exposure values on the occasion of adaptation of DRL is crucial for prompt detection of exceeded values independently from assessment by the responsible authority and initiation of proper measures for decreasing exposure dose. Hereby active dose management is attained. Key Points: •Analysis of exposure values for high data volumes obtained from the Radiology Information System (RIS) is possible independent of weight. •Summation of small groups of patients with different weights might result in high exposure values (DRL 70kg). •If high exposure values are observed in small groups of patients, individual analysis of examinations is mandatory. •Active dose management can be obtained by an analysis of average exposure of all examinations obtained during a specific observation period. • Potential for optimization of exposure values might be possible even they fall below DRL. Citation Format: •Schäfer S, Alejandre-Lafont E, Schmidt T etal. Dose Management for X-Ray and CT: Systematic Comparison of Exposition Values from two Institutes to Diagnostic Reference Levels and Use of Results for Optimisation of Exposition. Fortschr Röntgenstr 2014; 186: 785-794 © Georg Thieme Verlag KG Stuttgart, New York.