Feasibility of Displayed Exposure Index in Iec Standard Framework as a Dose Optimisation Tool for Digital Radiography Systems

Abstract

International Electrotechnical Commission (IEC) established the framework for the use of exposure index (EI) for evaluating the exposure conditions with various digital systems. In this study, we investigated the feasibility of EI, as per the IEC, by comparing the EIs obtained through manual calculated and that displayed on the console of two computed radiography (CR) and digital radiography (DR) systems with radiation beam qualities of RQA3,5,7 and 9. As a result, both two systems indicated an uncertainty of less than 20% for both calculated and displayed EI with all beam qualities except displayed EI obtained by RQA3. However, the displayed EI values were different even under the same exposure conditions because of the characteristics of the imaging receptor materials, such as BaFI or CsI, of two systems. Therefore, when an operator attempts to introduce displayed EI for managing radiation dose, it is essential to understand the characteristics of the digital system.

Proper Management of the Clinical Exposure Index Based on Body Thickness Using Dose Optimization Tools in Digital Chest Radiography: A Phantom Study

“…According to a previous study, the uncertainty of displayed EI was higher than that of manually calculated EI, but both EIs indicated allowable uncertainty (<20%), as per IEC standards. This discrepancy occurred due to the differences of digital characteristics between manually calculated and automatically displayed EI because of the differences of the digital characteristic curve used for the calculation [ 14 ]. However, the IEC standard recommended an EI uncertainty of under 20%, thus, if the displayed EI satisfied within the range of uncertainty (<20%), the digital radiation detector would be regarded as under good quality-controlled status [ 11 , 13 , 14 ].…”

“…This discrepancy occurred due to the differences of digital characteristics between manually calculated and automatically displayed EI because of the differences of the digital characteristic curve used for the calculation [ 14 ]. However, the IEC standard recommended an EI uncertainty of under 20%, thus, if the displayed EI satisfied within the range of uncertainty (<20%), the digital radiation detector would be regarded as under good quality-controlled status [ 11 , 13 , 14 ]. Moreover, it is reported that prior to using the EI, understanding the characteristics of digital system is necessary [ 13 , 14 ].…”

“…Before using the EI in a clinical situation, the user should identify the characteristics of the digital system, such as whether the uncertainty of the EI value in calibration conditions is according to IEC 62494-1 [ 11 , 14 ]. The IEC specifies that EI should be calculated by uniformly irradiating the relevant image region with the radiation quality (RQA) 5 in the absence of a subject and using the central 10% of the relevant image region as the value of interest (VOI) [ 11 ].…”

“…Previous studies have reported the usefulness of EI, as per IEC standards, which can be achieved using a quality control tool and an effective radiation dose monitoring system. Park et al investigated the possibility of using it as a quality control tool by using displayed EI, as per IEC standards, and also revealed that the usefulness of clinical EI, EI T , and DI, which could be recorded in DICOM header tags for monitoring the ESD based on the national diagnostic reference levels (DRLs) [ 13 , 14 ]. In clinical situations, there are several trials that have introduced the clinical EI, EI T , and DI to optimize medical radiation use [ 15 , 16 , 17 ].…”

“…However, the calculation of EI depends on the beam quality and the image receptor dose. There is a possibility that EI cannot reflect the ESD, as the size of the patient varies [ 14 ]. Nowadays, an automatic exposure control (AEC) system is commonly employed to adjust an optimal sensitivity of radiograph regardless of the patient size, thus, the tube current product time (mAs) would vary with the size of the patient to maintain the identical quality of radiograph [ 18 ].…”