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

Abstract

In radiography, the exposure index (EI), as per the International Electrotechnical Commission standard, depends on the incident beam quality and exposure dose to the digital radiography system. Today automatic exposure control (AEC) systems are commonly employed to obtain the optimal image quality. An AEC system can maintain a constant incident exposure dose on the image receptor regardless of the patient thickness. In this study, we investigated the relationship between body thickness, entrance surface dose (ESD), EI, and the exposure indicator (S value) with the aim of using EI as the dose optimization tool in digital chest radiography (posterior–anterior and lateral projection). The exposure condition from the Korean national survey for determining diagnostic reference levels and two digital radiography systems (photostimulable phosphor plate and indirect flat panel detector) were used. As a result, ESD increased as the phantom became thicker with constant exposure indicator, which indicates similar settings to an AEC system, but the EI indicated comparatively constant values without following the tendency of ESD. Therefore, body thickness should be considered under the AEC system for introducing EI as the dose optimization tool in digital chest radiography.

Feasibility of new patient dose management tool in digital radiography: Using clinical exposure index data of mobile chest radiography in a large university hospital

“…This study conducted, additional experiments to utilize clinical EI to monitor the patient dose. Based on the result that clinical EI varies according to patient body shape under the same exposure conditions confirmed through previous studies [ 18 ] and data analysis in section 2.2 of this paper, the conversion formula was developed to derive the entrance surface dose (ESD) from clinical EI.…”

“…However, the EI of the radiographic images used in this study showed various distributions. Even if the same dose was exposed, the EI could vary due to the difference in the detector's incident dose depending on the patient's body thickness through the phantom experiment in a previous study [ 18 , 19 ]. Accordingly, in this study, the effect of a patient's body shape on EI was confirmed using actual clinical image data.…”

“…Previous studies are being conducted to monitor the patient dose using EI as per the IEC standard [ [14] , [15] , [16] , [17] , [18] ]. This study conducted, additional experiments to utilize clinical EI to monitor the patient dose.…”

“…However, the clinical EI also shows a proportional relationship with the incident dose on the detector [ 15 , 17 ]. Therefore, several studies have demonstrated the utility of the EI as a real-time dose-monitoring tool [ [14] , [15] , [16] , [17] , [18] ].…”

“…In addition, the possibility of using clinical EI as a dose-monitoring tool was suggested by setting an appropriate target exposure index (EI T ) based on national diagnostic reference levels (DRLs) [ 15 , 17 ]. A study was conducted on the considerations when using EI as a dose monitoring tool in clinical practice through the change in EI according to the patient's thickness in an environment where an automatic exposure control (AEC) system is applied [ 18 ].…”