An assessment of exposure indices in computed radiography for the posterior–anterior chest and the lateral lumbar spine

Radiation Protection among South African Diagnostic Radiographers-A Mixed Method Study

ABSTRACT

Worldwide, radiographers' radiation protection practices vary. In South Africa, evidence of diagnostic radiographers' suboptimal radiation protection practices has been reported, but the reasons for these practices and suggestions to improve practices were lacking. Therefore, this study explored radiation protection among South African diagnostic radiographers. This study used an explanatory, sequential, mixed-method approach. Data were collected in three phases. Phase I, the quantitative phase, used an online questionnaire and respondents from Phase I interested in participating in Phase II, the qualitative phase, were interviewed, yielding 13 in-depth semi-structured telephone interviews. In Phase III, eight radiography managers co-constructed change strategies to optimize radiation protection in South Africa in two focus group interviews. Radiation protection was suboptimal despite diagnostic radiographers having a good attitude, subjective norm and perceived behavioral control toward radiation protection and optimal radiation protection knowledge. Varying attitudes to radiation protection, lack of resources, and support from radiography management and healthcare teams contributed to suboptimal radiation protection practices. Radiography managers suggested increasing radiation protection awareness, ameliorating the diminished stature of the radiographer in the healthcare team, and increasing the availability of optimal quality resources. South African diagnostic radiographers' radiation protection knowledge was optimal, but the implementation of radiation protection varied and was influenced by multiple factors. A radiation protection culture supported by management is advocated to optimize radiation protection. However, ultimately radiation protection practices are incumbent on the individual radiographers' choice to practice radiation protection.

Exploring the reliability of the exposure index with a range of kV and mAs values: An experimental study

INTRODUCTION

The exposure index (EI) is a numerical post-exposure tool that provides feedback to diagnostic radiographers undertaking digital X-ray examinations. The EI seeks to provide an indicator of the quantity of incident ionising radiation imparted on an image receptor. However, any large increase to X-ray intensity could interfere with the calculation of the EI. The aim of this paper was to evaluate detector overexposure by increasing X-ray beam intensity and quantifying the resultant effect on the EI.

METHODS

A porcine hip was purchased and exposed with varying tube potentials (50 to 110 kVp) and tube current-time products (5 to 100 mAs). Entrance surface dose (ESD) and EI values were determined for each exposure. For each acquisition parameter, two dose readings were collected. Linear regression was utilised to ascertain the relationship between the EI and varying tube exposures.

RESULTS

Tube exposures between 50 and 80 kVp demonstrated strong positive linear correlation coefficients (r = 0.993, p <0.001; r = 0.999, p <0.001; r = 0.983, p <0.001; r = 0.925, p <0.001) between ESD and EI. However, upon increasing tube exposures (90 to 110 kVp), interference with the EI calculation was demonstrated, which impacted both linearity, strength and direction of correlation (90 kVp r = 0.083, p = .248; 100 kVp r = -0.066, p = .479; 110 kVp r = -0.110, p = .601). Consequently, the use of higher tube exposures demonstrated variability with the EI by not demonstrating an expected positive linear relationship, which remained the initial expectation in this study.

CONCLUSION

The EI value is generally associated with providing reliable feedback to radiographers, yet this paper identifies some unexpected findings at high tube exposures (90 to 110 kVp). In short, this experiment provides insight that the EI value demonstrates inconsistent values within certain energy ranges.

IMPLICATIONS FOR PRACTICE

The findings have implications because it identifies variability of EI values at higher tube exposures. EI values may, therefore, not be helpful in providing meaningful feedback to radiographers when making changes to exposure factors.

Diagnostic radiography students' experiences of a practical method demonstrating the effect of milliampere-second in digital X-ray imaging systems

BACKGROUND

The effect of exposure technique factors varies between analogue and digital X-ray imaging systems (DR). Understanding these variations is paramount to optimising radiation protection, yet radiographers are unclear about these effects. A practical method to demonstrate milliampere second (mAs) effect in DR was developed to assist diagnostic radiography students in understanding exposure technique factors in DR.

OBJECTIVES

To explore second-year diagnostic radiography students' experiences of a practical method to demonstrate the effect of mAs in DR.

METHODS

A qualitative research approach employing an open-ended questionnaire explored second-year diagnostic radiography students' experiences of the practical method demonstrating the effect of mAs in DR. Twenty students participated in the study, and the data collected underwent thematic analysis.

RESULTS

Students appreciated working in small groups and provided suggestions to improve the practical method's instruction sheet. Most students' predicted outcome differed from the actual outcome of the demonstration. Seeing and documenting the effect of mAs in DR not only enhanced students' understanding of it but showed the implications of increasing mAs on image quality and radiation exposure.

CONCLUSION

Students found that the practical method enhanced their understanding of mAs and exposure technique factors in DR. Additionally, the practical method highlighted exposure creep in DR and radiographers' role in protecting patients from overexposure to ionising radiation in the digital era.

Optimising default radiographic exposure factors using Deviation Index

INTRODUCTION

Radiographers have a duty to ensure that radiation doses to patients are as low as reasonably achievable. With digital technologies, exposure factors which achieve the optimum balance between image noise and patient dose must be sought. In digital radiography, Deviation Index (DI) values provide the radiographer with feedback on the appropriateness of individual exposures but can also be tracked as part of a departmental quality assurance programme.

METHODS

In November 2017, exposure logs were extracted from six digital radiography (DR) x-ray systems, collated and analysed. Five examinations were identified which frequently produced DI values outside the manufacturer's recommended Optimal Range (-3 to +2). Incremental improvements were made to the default exposure settings for these examinations via a cyclical process of modification and re-evaluation. A full data collection exercise was then repeated in April 2019.

RESULTS

At baseline, 10,658 out of 29,637 (36.0%) exposures had DI values outside the manufacturer's recommended Optimal Range, but for some individual examinations the proportion was as high as 547 out of 725 (74.5%). Following multiple optimisation cycles, the overall proportion of examinations outside the Optimal Range had fallen to 7611 out of 26,759 (28.4%). Default milliampere-seconds (mAs) values for these examinations were reduced by between 22% and 50%.

CONCLUSION

A marked reduction in patient doses can be achieved through a departmental programme of DI value monitoring and targeted optimisation of default exposure settings.

IMPLICATIONS FOR PRACTICE

DI values should be routinely monitored as part of routine quality assurance programmes. Radiographers have a responsibility to ensure that they possess a clear understanding of DI values and that appropriate exposure settings are selected for each individual patient.

Retrospective evaluation of exposure indicators: a pilot study of exposure technique in digital radiography

INTRODUCTION

Digital radiography lacks visual clues of exposure techniques used to obtain radiographs, therefore manufacturers have included exposure indicators (EIs). EIs provides feedback about exposure techniques used and evaluating EIs will yield much needed information about exposure trends used in digital radiography.

METHODS

A retrospective explorative quantitative study was conducted at nine randomly selected imaging departments in Gauteng, South Africa. Data pertaining to EI was retrospectively collected using quota sampling and compared to manufacturer recommended (MR) standards.

RESULTS

A total of 1422 EIs were collected. 50% of these were within the MR standard. 27% of EI indicated overexposure and 23% indicated underexposure.

CONCLUSIONS

Greater evidence of overexposure was noted in the retrospective analysis of the EI. This pilot study shows the need for further investigation into exposure technique practices in digital radiography and the need for measures to halt the evidenced overexposure.

Optimisation of radiation dose and image quality in mobile neonatal chest radiography

PURPOSE

To optimise the radiation dose and image quality for chest radiography in the neonatal intensive care unit (NICU) by increasing the mean beam energy.

METHODS

Two techniques for the acquisition of NICU AP chest X-ray images were compared for image quality and radiation dose. 73 images were acquired using a standard technique (56 kV, 3.2 mAs and no additional filtration) and 90 images with a new technique (62 kV, 2 mAs and 2 mm Al filtration). The entrance surface air kerma (ESAK) was measured using a phantom and compared between the techniques and against established diagnostic reference levels (DRL). Images were evaluated using seven image quality criteria independently by three radiologists. Images quality and radiation dose were compared statistically between the standard and new techniques.

RESULTS

The maximum ESAK for the new technique was 40.20 μGy, 43.7% of the ESAK of the standard technique. Statistical evaluation demonstrated no significant differences in image quality between the two acquisition techniques.

CONCLUSIONS

Based on the techniques and acquisition factors investigated within this study, it is possible to lower the radiation dose without any significant effects on image quality by adding filtration (2 mm Al) and increasing the tube potential. Such steps are relatively simple to undertake and as such, other departments should consider testing and implementing this dose reduction strategy within clinical practice where appropriate.

A comparative assessment of entrance surface doses in analogue and digital radiography during common radiographic examinations

Digital radiography is often performed at a higher dose rate than analogue radiography for image acquisition. The authors measured the Entrance Surface Dose (ESD) of analogue and digital radiography techniques for 14 radiographic examinations from randomly selected medical centres in the central district of Korea. It was that the mean ESD of the digital examinations was 2.84 mGy (range, 0.37-6.38 mGy) and that of the analogue examinations was 1.83 mGy (range, 0.38-4.74 mGy), resulting in a 55.25 % higher ESD for digital technique. Although this survey is not completely representative of Korea, findings of this study indicate a need for closer exposure management in digital radiography to minimise patient dose.

Retrospective evaluation of exposure index (EI) values from plain radiographs reveals important considerations for quality improvement

INTRODUCTION

Following X-ray exposure, radiographers receive immediate feedback on detector exposure in the form of the exposure index (EI).

PURPOSE

To identify whether radiographers are meeting manufacturer-recommended EI (MREI) ranges for routine chest, abdomen and pelvis X-ray examinations under a variety of conditions and to examine factors affecting the EI.

METHODS

Data on 5000 adult X-ray examinations including the following variables were collected: examination parameters, EI values, patient gender, date of birth, date and time of examination, grid usage and the presence of implant or prosthesis. Descriptive statistics were used to summarize each data set and the Mann-Whitney U test was used to determine significant differences, with P < 0.05 indicating significance for all tests.

RESULTS

Most examinations demonstrated EI values that were outside the MREI ranges, with significantly higher median EI values recorded for female patient radiographs than those for male patients for all manufacturers, indicating higher detector exposures for all units except for Philips digital radiography (DR), where increased EI values indicate lower exposure (P = 0.01). Median EI values for out of hours radiography were also significantly higher compared with normal working hours for all technologies (P ≤ 0.02). Significantly higher median EI values were demonstrated for Philips DR chest X-rays without as compared to those with the employment of a grid (P = 0.03), while significantly lower median EI values were recorded for Carestream Health computed radiography (CR) chest X-rays when an implant or prosthesis was present (P = 0.02).

CONCLUSIONS

Non-adherence to MREIs has been demonstrated with EI value discrepancies being dependent on patient gender, time/day of exposure, grid usage and the presence of an implant or prosthesis. Retrospective evaluation of EI databases is a valuable tool to assess the need of quality improvement in routine DR.

A method to derive appropriate exposure parameters from target exposure index and patient thickness in pediatric digital radiography

BACKGROUND

Little information exists concerning appropriate exposure and measuring overall patient dose in pediatric digital radiography.

OBJECTIVE

To establish a convenient method of appropriate exposure from target exposure index (EI) and thickness in pediatric digital radiography and estimate patient entrance-surface dose (ESD) and dose-area product (DAP) associated with chest, abdomen and pelvis radiography.

MATERIALS AND METHODS

A formula was deduced to calculate appropriate mAs changed with children's weight and height. EI was used to control image quality. With this formula, dose-optimized procedures were carried out. Data were collected from 180 pediatric examinations, including chest, abdomen and pelvis anterior-posterior (AP) projections. The children were divided into the following age bands: newborns (0-28 days), infants (28 days-2 years) and older children (2-7 years). In each age band, ten children were exposed with the calculated appropriate mAs and EI values were kept steady in appropriate range (referred as target group) and ten children were exposed to the factors routinely used in practice (referred to as the routine group). DAP to children was measured with a DAP meter, and ESD was calculated using measured DAP and data from the National Radiological Protection Board. Data were compared between groups.

RESULTS

ESD ranges in the target group were 32-202 μGy (chest AP), 57-333 μGy (abdomen AP) and 52-372 μGy (pelvis AP). For every radiographic procedure, chi-square Student's t tests showed a significant difference in average ESD and DAP between the two groups (P < 0.005). Most ESD values from the routine group were two times higher than those from the target group.

CONCLUSIONS

The study established a convenient method to set appropriate exposure parameters (mAs) to reach a target EI using the child's weight and height in pediatric radiography. By this method, ESD and DAP can be significantly reduced in children.

Evaluation of two objective methods to optimize kVp and personnel exposure using a digital indirect flat panel detector and simulated veterinary patients

It is important to optimize digital radiographic technique settings for small animal imaging in order to maximize image quality while minimizing radiation exposure to personnel. The purpose of this study was to evaluate two objective methods for determining optimal kVp values for an indirect flat panel digital detector. One method considered both image quality and personnel exposure as endpoints and one considered only image quality. Phantoms simulated veterinary patients of varying thicknesses with lesions of varying sizes. Phantoms were exposed to a range of kVp values (60, 81, 100, and 121), using different mAs settings for each phantom. Additionally, all phantoms were exposed to a standard test exposure of 100 kVp/2.5 mAs. Scattered radiation was recorded and used as a measure of personnel exposure. When personnel exposure was considered, a figure of merit was calculated as an endpoint of optimization. The optimal kVp value for each phantom was determined based on the highest signal difference-to-noise ratio with or without inclusion of the figure of merit. When personnel exposure was not considered, increasing kVp resulted in higher signal difference-to-noise ratios and personnel exposure increased when both patient thickness and kVp increased. Findings indicated that a single standard technique of 100 kVp/2.5 mAs was only optimal for most medium-sized patients. Images of thinner patients should be made with a lower kVp. Very large patients require a higher kVp than 100 regardless of the optimization method used. Personnel exposure from optimized techniques was low and not expected to exceed annual occupational dose limits.

Dose optimization for different medical imaging tasks from exposure index, exposure control factor, and MAS in digital radiography

In radiographic examination, not all medical imaging tasks require the same level of image quality or diagnostic information. Criteria should be established for different imaging tasks to avoid excessive doses where there is no clear net benefit in the diagnosis or the image quality. An exposure index provided by manufacturers would be a useful tool for this purpose. This study aims to establish an optimum exposure index to be used as a guideline for clinical imaging tasks to minimize radiation exposure for chest digital radiography. A three-level classification of image quality (high, medium, and low) for chest imaging tasks was carried out. An anthropomorphic phantom was employed to establish minimum exposure index and exposure (mAs) for clinical imaging task type I (corresponding to high image quality). The exposures of medium and low quality images derived from it. Thirty patients were exposed consecutively with these optimized exposure factors, and clinical tasks were considered, while another 30 patients were exposed with the exposure factors routinely used in practice. Image quality was assessed objectively by a consensus panel. The optimized exposure provided a significant reduction of the mean exposure index from 1,556 to 1,207 (p < 0.0001) and mean patient's entrance surface dose from 0.168 mGy to 0.092 mGy (p < 0.0001). The results show that a clinical-task-determined radiographic procedure is more conducive to radiation protection of patients. In this study, the posteroanterior chest imaging examination was chosen as an example. This procedure can also apply to other body parts and views.

Exposure creep in computed radiography: a longitudinal study

PURPOSE

Exposure creep is the gradual increase in x-ray exposures over time that results in increased radiation dose to the patient. It has been theorized as being a phenomenon that results from the wide-exposure latitude of computed radiography (CR) and direct/indirect digital radiography (DR). This project evaluates radiographic exposures over 43 months to determine if exposure creep exists and if measures can be applied to halt or reverse exposure creep trends.

METHODS

Exposure indices were initially recorded over 29 months between August 2007 and December 2009 from the intensive and critical care unit (ICCU) and the emergency department (ED) departments where manual CR exposures were used. The data from this period were then assessed and the exposure indexes (EI) values from the radiographic images were compared to the radiology department criteria of EI values between 1400 to 1800 as being in the optimal exposure range. EI values below this were considered underexposed and over this as overexposed. An intervention was required to be used in ICCU and implemented in January 2010 to halt a noted trend of overexposure. The EI value for each chest x-ray (CXR) was recorded in the patients' ICCU records and was to be used by radiologic technologists/radiographers in determine exposure factors in subsequent CXR. After the intervention, EI values were recorded and evaluated for an additional 15 months between February 2010 and March 2011.

RESULTS

Between August 2007 and December 2009, 17,678 ICCU CXR images and 69,327 ED x-ray examinations were evaluated for over- and underexposure. A trend was noted in ICCU that showed a significant increase (P = .023) in EI values from the beginning to the end of the evaluation. No such trend was seen in the ED EI values (P = .120). After the intervention in ICCU, the overexposure trend was halted.

CONCLUSIONS

Exposure creep has been show to exist. It is surmised that this occurs where judgment to determine the correct radiographic exposure factors is needed when taking into account a large range of patient sizes. It has also been shown that providing radiologic technologists/radiographers with previous EI values for the same x-ray examination can halt a trend of exposure creep.

Investigation into Factors Influencing Fuji S-Value Using an Extremity Phantom

Exposure indices are provided by manufacturers to give an indication of exposure for computed radiography (CR). Although there are recommended ranges for exposure index values for various examinations, they may be affected by a number of other factors in addition to exposure. This study using an extremity phantom found collimation to be the most important factor influencing the S-value for a Fuji CR system. It is therefore essential that collimation is kept as tight as possible without excluding relevant anatomy. CR imaging plates should be processed rapidly after exposure to prevent loss of information stored in the latent image. The reliability of the S-value exposure index as an indicator of exposures can be increased with better understanding of how it works, and by practical application of this knowledge to radiography.

Dicoogle - an open source peer-to-peer PACS

Picture Archiving and Communication Systems (PACS) have been widely deployed in healthcare institutions, and they now constitute a normal commodity for practitioners. However, its installation, maintenance, and utilization are still a burden due to their heavy structures, typically supported by centralized computational solutions. In this paper, we present Dicoogle, a PACS archive supported by a document-based indexing system and by peer-to-peer (P2P) protocols. Replacing the traditional database storage (RDBMS) by a documental organization permits gathering and indexing data from file-based repositories, which allows searching the archive through free text queries. As a direct result of this strategy, more information can be extracted from medical imaging repositories, which clearly increases flexibility when compared with current query and retrieval DICOM services. The inclusion of P2P features allows PACS internetworking without the need for a central management framework. Moreover, Dicoogle is easy to install, manage, and use, and it maintains full interoperability with standard DICOM services.

Automated detection of changes in patient exposure in digital projection radiography using exposure index from DICOM header metadata

PURPOSE

Automated collection of image data from DICOM headers enables monitoring of patient dose and image quality parameters. Manual monitoring is time consuming, owing to the large number of exposure scenarios, thus automated methods for monitoring needs to be investigated. The aim of the present work was to develop and optimise such a method.

MATERIAL AND METHODS

Exposure index values from digital systems in projection radiography were collected over a period of five years, representing data from 1.2 million projection images. The exposure index values were converted to detector dose and an automated method for detection of sustained level shifts in the resulting detector dose time series was applied using the statistical analysis tool R. The method combined handling of outliers, filtering and estimation of variation in combination with two different statistical rank tests for level shift detection. A set of 304 time series representing central body parts was selected and the level shift detection method was optimised using level shifts identified by ocular evaluation as the gold standard.

RESULTS

Two hundred and eighty-one level changes were identified that were deemed in need of further investigation. The majority of these changes were abrupt. The sensitivity and specificity of the optimised and automated detection method concerning the ocular evaluation were 0.870 and 0.997, respectively, for detected abrupt changes.

CONCLUSIONS

An automated analysis of exposure index values, with the purpose of detecting changes in exposure, can be performed using the R software in combination with a DICOM header metadata repository containing the exposure index values from the images. The routine described has good sensitivity and acceptable specificity for a wide range of central body part projections and can be optimised for more specialised purposes.

DICOM Metadata repository for technical information in digital medical images

The diagnostic medical image contains, apart from the pixel data, a detailed description of how the image was produced. The information reveals details on image geometry, radiation data as well as more complex quality index in a varying degree, mostly dependent on the age of the equipment. There is no simple way to retrieve, process and display this data in a general image workstation.

MATERIAL AND METHODS

Since November 2004 a DICOM metadata repository has been used to record image header parameters. The automated data extraction, storage and display are based on simple standard programming and have performed without malfunction since the start, today containing metadata from 18 million images.

RESULTS

The data in the metadata repository has been used in dose optimization for a Computed Radiography image plate system, analyzing the exposure index and making use of the possibilities to organize the data in examinations, projections as well as examination rooms. Analysis of exposure index in the context of these parameters shows promising qualities as it makes detection of dosimetric problems as well as follow-up of dose adjustments simpler. Current work is aimed at creating a vendor independent platform and to further develop methods to support dose optimization for flat panel direct digital detectors and computed tomography (CT) systems. The possibilities to detect equipment malfunction will be further investigated.

Correlation of image quality with exposure index and processing protocol in a computed radiography system

The correlation of image quality with the exposure index (EI) and the processing protocol was investigated in a Kodak computed radiography (CR) system using clinical radiographs and a water phantom containing an aluminium and a copper step-wedge. The phantom was exposed to different dose levels and the acquired images were processed using four clinical protocols. The quality of these images was evaluated in terms of image brightness, contrast and noise. In clinical radiographs, there was no straightforward correlation of image quality with EI. In phantom images, higher EI values improved contrast and reduced noise but after a point this improvement does not justify the implied increase in patient dose. Image brightness, contrast and noise were also strongly dependent on the processing protocol. To obtain the images of satisfactory quality with the Kodak CR system, a dose slightly higher than those used in 400 relative speed screen-film systems and a processing protocol designated for the specific radiographic examination are required.