Article

FEASIBILITY OF DISPLAYED EXPOSURE INDEX IN IEC STANDARD FRAMEWORK AS A DOSE OPTIMISATION TOOL FOR DIGITAL RADIOGRAPHY SYSTEMS

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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.

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Article
In digital radiography (DR) systems, the sensitivity index, also known as the exposure indicator, exhibits unique behavior, depending on the manufacturer. The exposure index (EI) was introduced by the International Electrotechnical Commission to standardize the sensitivity indices of DR systems produced by different manufacturers for general radiography. This EI value is directly proportional to the dose incident on the imaging detector, providing valuable insight into exposure dose levels and radiographic noise. Recently, technological advancements have enabled some DR systems to display the EI value on the console immediately after exposure. This study investigated the characteristics of the displayed EI value and radiographic noise for an indirect flat-panel detector across four X-ray beam qualities based on added aluminum filters: RQA3, 5, 7, and 9. The displayed EI values for all the X-ray beam qualities proportionally increased to the dose incident on the detector. However, the displayed EI values for RQA3 deviated from those for RQA5, 7, and 9 at the same doses incident on the imaging detector. Furthermore, the Wiener spectrum (WS) was used to evaluate radiographic noise. For similar EI values, the WS of RQA3, which had the highest dose incident on the imaging detector, was slightly lower than those of other X-ray beam qualities. Our findings suggest that the relationship between the displayed EI and radiographic noise varies with the X-ray beam quality.
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The clinical anteroposterior (AP) chest images taken with a mobile radiography system were analyzed in this study to utilize the clinical exposure index (EI) as a patient dose-monitoring tool. The digital imaging and communications in medicine header of 6048 data points exposed under the 90 kVp and 2.5 mAs were extracted using Python for identifying the distribution of clinical EI. Even under the same exposure conditions, the clinical EI distribution was 137.82–4924.38. To determine the cause, the effect of a patient's body shape on EI was confirmed using actual clinical chest AP image data binarized into 0 and 255-pixel values using Python. As a result, the relationship between the direct X-ray area of the chest AP image, the higher the clinical EI, the larger the rate of the direct X-ray area. A conversion equation was also derived to infer entrance surface dose through clinical EI based on the patient thickness. This confirmed the possibility of directly monitoring patient dose through EI without a dosimeter in real-time. Therefore, to use the clinical EI of the mobile radiography system as a patient dose-monitoring tool, the derivation method of clinical EI considers several factors, such as the relationship between patient factors.
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Objective: To present an optimized examination model by analyzing the risk of disease and image quality according to the combination of the ion chamber of automatic exposure control (AEC) with digital radiography (DR). Methods: The X-ray quality was analyzed by first calculating the percentage average error (PAE) of DR. After that, when using AEC, the combination of the ion chambers was the same as the left and centre and right, right and centre, left and centre, centre, right, and left, for a total of six. Accordingly, the entrance surface dose (ESD), risk of disease, and image quality were evaluated. ESD was obtained by attaching a semiconductor dosimeter to the L4 level of the lumbar spine, and then irradiating X-rays to dosimeter centre through average and standard deviation of radiation dose. The calculated ESD was input into the PCXMC 2.0 programme to evaluate disease risk caused by radiation. Meanwhile, image quality according to chamber combination was quantified as the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) through Image J. Results: X-ray quality of DR used in the experiment was within the normal range of±10. ESD of six ion chamber combinations was 1.363mGy, 0.964mGy, 0.946mGy, 0.866mGy, 0.748mGy, 0.726mGy for lumbar anteroposterior (AP), and the lumbar lateral values were 1.126mGy, 0.209mGy, 0.830mGy, 0.662mGy, 0.111mGy, and 0.250mGy, respectively. Meanwhile, disease risk analyzed through PCXMC 2.0 was bone marrow, colon, liver, lung, stomach, urinary and other tissue cancer, and disease risk showed a tendency to increase in proportion to ESD. SNR and CNR recorded the lowest values when three chambers were combined and did not show proportionality with dose, while showed the highest values when two chambers were combined. Conclusion: In this study, combination of three ion chambers showed the highest disease risk and lowest image quality. Using one ion chamber showed the lowest disease risk, but lower image quality than two ion chambers. Therefore, if considering all above factors, combination of two ion chambers can optimally maintain the disease risk and image quality. Thus, it is considered an optimal X-ray examination parameter.
Article
Background: The International Electrotechnical Commission established the concept of the exposure index (EI), target exposure index (EIT) and deviation index (DI). Some studies have conducted to utilize the EI as a patient dose monitoring tool in the digital radiography (DR) system. Objective: To establish the appropriate clinical EIT, this study aims to introduce the diagnostic reference level (DRL) for general radiography and confirm the usefulness of clinical EI and DI. Methods: The relationship between entrance surface dose (ESD) and clinical EI is obtained by exposure under the national radiography conditions of Korea for 7 extremity examinations. The EI value when the ESD is the DRL is set as the clinical EIT, and the change of DI is then checked. Results: The clinical EI has proportional relationship with ESD and is affected by the beam quality. When the clinical EIT is not adjusted according to the revision of DRLs, there is a difference of up to 2.03 in the DI value and may cause an evaluation error of up to 1.6 time for patient dose. Conclusions: If the clinical EIT is periodically managed according to the environment of medical institution, the appropriate patient dose and image exposure can be managed based on the clinical EI, EIT, and DI.
Article
Full-text available
The International Electrotechnical Commission (IEC) 62494-1 has defined the exposure index (EI) that have a proportional relationship with the dose incident on the image receptor, and target exposure index (EI T), deviation index (DI). In this study, an appropriate EI T for skull radiography was established through the diagnostic reference level (DRL) and changes in DI were confirmed. Entrance surface dose (ESD) and EI were obtained using the computed radiography system displayed the EI as per IEC on console and skull phantom by experiment based on the national average exposure conditions announced in 2012 and 2019. And appropriate EI T was established by applying the DRL in 2012 and 2019. As a results, the EI T is changed according to the change in the DRL, and the exposure condition that becomes the ideal DI according to the change in the EI T also has a difference of about 1.41 times. DRL is recommended to optimize the patient dose, however it is difficult to measure in real time at medical institutions whereas EI and DI are displayed on the console at the same time as exposure. When the EI T is set based on the DRL and the DI is closed to an ideal value, it is useful as a patient dose management tool. Therefore, when the EI T is periodically managed along with the revision of the DRLs, the patient dose can be optimized through the EI, EI T and DI.
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Full-text available
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.
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The International Electrotechnical Commission introduced the concepts of exposure index (EI), target exposure index (EI T) and deviation index (DI) to manage and optimize patient dose in real time. In this study, we have proposed an appropriate method for setting the EI T based on the Korean national diagnostic reference levels (DRLs). Furthermore, we evaluated the use of clinical EI, EI T and DI as tools for patient dose optimization in clinical environments by observing the changes in DI with those in EI T. According to the Korean national exposure conditions, we conducted experiments on three representative radiographic examinations (chest posterior-anterior, lateral and abdomen anterior-posterior) of clinical environments. As the exposure conditions and DRLs varied, the clinical EI, EI T and DI also varied. These results reveal that the clinical EI, EI T and DI can be used as tools for optimizing the patient dose if EI T is periodically and properly updated.
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We measured physical image properties of a flat panel detector (FPD) system and a computed radiography (CR) system, targeting to a low dose range (reference dose: 2.58×10(-7) C/kg: to 1/20 dose). Input-output properties, pre-sampled modulation transfer functions (pre-sampled MTFs), and normalized noise power spectra for an FPD system equipped with a CsI scintillator (FPDcsi) and a CR system with an imaging plate coated with storage phosphor (CR) were measured at the low dose range for radiation quality of RQA3 (≍50 skV) and RQA5 (≍70 kV), and detective quantum efficiencies (DQEs) were calculated. In addition, in order to validate the DQE results, component fractions of Poisson and multiplicative and additive noise were analyzed using relative standard deviation analysis. The DQE values of FPDcsi were decreased with dose decrease, and contrarily to these, those of CR were increased. At the 1/10 and 1/20 doses for RQA3, the DQEs of FPDcsi and CR became almost the same. From the results of RSD analysis, it was proved that the main cause of DQE deterioration on FPDcsi are non-negligible additive (electronic) noise, and the DQE improvement on CR was caused by both of significant multiplicative (structure) noise and very low electronic noise. The DQE results were validated by comparing burger phantom images of each dose and radiation quality.
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To find the tube voltage that results in the highest image quality per effective dose unit for chest and pelvis radiography, respectively, using image plates. Two anthropomorphic phantoms (chest and pelvis) were imaged with several different tube voltages. The mA s settings were chosen so that the effective dose to the phantom was the same, regardless of the tube voltage, for the two examinations, respectively. The quality of the images was evaluated by six experienced radiologists using visual grading analysis. For both the chest and the pelvis examinations, the image quality increased when the tube voltage was reduced compared with the standard settings (125 and 70 kV for chest and pelvis, respectively), which were used for screen-film radiography previously. The image quality of image plate radiography can be increased by lowering the tube voltage compared with the one that was used for screen-film radiography.
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Over the last 50 years, diagnostic imaging has grown from a state of infancy to a high level of maturity. Many new imaging modalities have been developed. However, modern medical imaging includes not only image production but also image processing, computer-aided diagnosis (CAD), image recording and storage, and image transmission, most of which are included in a picture archiving and communication system (PACS). The content of this paper includes a short review of research and development in medical imaging science and technology, which covers (a) diagnostic imaging in the 1950s, (b) the importance of image quality and diagnostic performance, (c) MTF, Wiener spectrum, NEQ and DQE, (d) ROC analysis, (e) analogue imaging systems, (f) digital imaging systems, (g) image processing, (h) computer-aided diagnosis, (i) PACS, (j) 3D imaging and (k) future directions. Although some of the modalities are already very sophisticated, further improvements will be made in image quality for MRI, ultrasound and molecular imaging. The infrastructure of PACS is likely to be improved further in terms of its reliability, speed and capacity. However, CAD is currently still in its infancy, and is likely to be a subject of research for a long time.
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