Evaluation of the effects of subject thickness on the exposure index in digital radiography

Abstract

The exposure index (EI) was proposed as a new X-ray dose index by the International Electrotechnical Commission (IEC) and has since been implemented as an international standard. The EI is calculated by use of an approximation equation under IEC-specified calibration conditions. However, several factors encountered in clinical practice, including the patient's body thickness and the tube voltage, differ with regard to these calibration conditions. We, therefore, require a solid water phantom-based function that can incorporate the IEC-specified conditions and different subject thicknesses to evaluate the effects of subject thickness on the EI. Here, we assumed average thicknesses of 10 cm for a child, 15 cm for slender patients, and 21 cm for an average adult abdomen and we evaluated errors, that are included in the EI, which were calculated by use of the function. Our results suggested that the EI depends on the subject thickness. At the 21-cm thickness (average adult abdomen), the display EI exhibited a small error level. In contrast, EI values calculated from the calibration conditions exhibited maximum errors that were as high as 34 % at the lower subject thicknesses (10 and 15 cm), suggesting a significant influence of the subject thickness on the EI. In conclusion, the EI should be used cautiously during the examination of children and thin patients, with a complete understanding of the discrepancy revealed by our study results.

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

“…However, the clinical EI of both chest PA and LAT projection did not indicate a similar tendency with ESD, and the phantom distance compared with those of ESD. Takaki et al reported that the EI, as per the IEC standards framework, depends on the PMMA phantom thickness, and thus EI should be introduced cautiously for children and thin patients [ 26 ]. Sánchez et al proposed that the thickness-based techniques for portable pediatric abdomen radiography should be used to reduce the variability in EI because default pediatric protocols do not adequately characterize the patient size, which is the principal determinant of proper imaging technique [ 27 ].…”

Characterization and validation of the thorax phantom Lungman for dose assessment in chest radiography optimization studies

“…A number of factors contribute to this variation in EI value, including variable collimation 35 and segmentation by the EI algorithm. There is also the known dependence of EI with patient thickness: 36 patients with different thickness and anatomy will produce a change in the beam quality, which then influences the EI value. 16 In Fig.…”

Evaluation of Exposure Index Values for Conventional Radiology Examinations: Retrospective Study in Governmental Hospitals at West Bank, Palestine

“…To remove the noise level on image in DR system, the radiologic technologists (RTs) is forced to raise the image parameters. However, the increase in the image parameters produce a readable image (Takaki et al, 2016) (Muntaser S Ahmad et al, 2019). The extent of the increase in parameters increase radiation dose to patients.…”

“…The EI is used as a quality control tool to check the image quality, because the EI is proportional to the square signal to noise ratio (SNR) (Takaki et al, 2016) (Martin et al, 2017). The EI values for radiological examinations vary according to the manufacturer, each of manufacturer has specific values for the EI.…”