Optimisation in general radiography

Patient dose and associated exposure parameters in pelvic x-ray examinations: dependence on radiographic system

Technological differences between computed radiography (CR) and digital radiography (DR) systems can influence patient doses and exposure parameters in pelvic x-ray examinations. The presence of radiosensitive organs in the pelvic region underscores the need to optimize these parameters for both CR and DR systems. This prospective study aimed to compare the patient doses and exposure parameters for adult patients undergoing pelvic x-ray examinations using CR and DR systems, based on data from Sri Lanka. The study included data from 56 x-ray examinations, with 25 using CR and 31 using DR. Patient demographic characteristics and exposure parameters (kVp: kilovoltage peak, mAs: tube current-exposure time product) were recorded, and patient doses were measured in terms of the kerma-area product (PKA) using a PKA meter. Despite similar mean weight and body mass index (BMI), the CR systems showed significantly higher mean kVp (7.4%), mAs (16.4%), and PKA (29.7%) than the DR systems (CR - kVp: 73.2, mAs: 37.8, PKA: 2.29 Gy cm2; DR - kVp: 67.8, mAs: 31.6, PKA: 1.61 Gy cm2). The Mann-Whitney U test revealed statistically significant differences in PKA and kVp between the CR and DR systems (p < 0.05). Furthermore, even with lower patient weight and BMI, the mean mAs and PKA in this study were substantially higher than those reported in the literature for both CR and DR systems. These results suggest the need to optimize current mAs settings for the studied hospitals and introduce radiographic system-specific exposure parameters and reference dose levels for pelvic x-ray examinations in order to enhance patient protection.

Dose optimization in newborn abdominal radiography: Assessing the added value of additional filtration on radiation dose and image quality using an anthropomorphic phantom

Background

Abdominal radiographs remain useful in newborns. Given the high radiation sensitivity of this population, it is necessary to optimize acquisition techniques to minimize radiation exposure.

Objective

Evaluate the effects of three additional filtrations on radiation dose and image quality in abdominal X-rays of newborns using an anthropomorphic phantom.

Material and method

Abdominal radiographs of an anthropomorphic newborn phantom were performed using acquisition parameters ranging from 55 to 70 kV and from 0.4 to 2.5 mAs, without and with three different additional filtrations: 0.1 mm copper (Cu) + 1 mm aluminum (Al), 0.2 mm copper + 1 mm aluminum, and 2 mm aluminum. For each X-ray the dose area product (DAP) was measured, the signal-to-noise ratio (SNR) was calculated, and image quality (IQ) was evaluated by two blinded radiologists using the absolute visual grading analysis (VGA) method.

Results

Adding an additional filtration resulted in a significant reduction in DAP, with a decrease of 42% using 2 mm Al filtration, 65% with 0.1 mm Cu + 1 mm Al filtration, and 78% with 0.2 mm Cu + 1 mm Al filtration (p < 0.01). The addition of 2 mm aluminum filtration does not significantly decrease the SNR (p = 0.31), CNR (p = 0.52) or the IQ (p = 0.12 and 0.401 for reader 1 and 2, respectively). However, adding copper-containing filtration leads to a significant decrease in, SNR, CNR and IQ.

Conclusion

Adding a 2 mm Al additional filtration for abdominal radiographs in newborns can significantly reduce the radiation dose without causing a significant decrease in image quality.

Potentials of additional copper filtration on radiation dose and image quality for adults underwent digital chest X-ray imaging in Dubai Health Authority - UAE

OBJECTIVE

To explore the potentials of adding copper (Cu) filter on image quality and patient dose of adult patients underwent chest X-ray examination METHODS: Patients were divided into four groups. Group 1, patients were exposed with no added Cu filter (standard or control), group 2 a 0.1 mm Cu filter was added, group 3 acquired with 0.2 mm Cu filter and group 4 performed with 0.3 mm Cu filter. Exposure index (EI), entrance surface dose (ESD) and dose area product (DAP) were recorded from the modality and retrospectively analyzed. The visual grading analysis score (VGAS) was used to evaluate image quality. Mann-Whitney T-Test and one-way ordinary ANOVA Test were used to evaluate statistical differences including gender-based findings.

RESULTS

EI, ESD and DAP data for a total of 784 patients (422 male and 362 female) that underwent indirect digital chest radiography exam were collected. Image quality was maintained when adding 0.1 mm Cu filter achieved with ∼19% DAP reduction. Female showed a significant DAP reduction comparing to male registered in the same group.

CONCLUSIONS

Reducing dose when using indirect digital chest radiography is possible with no trade-off on image quality. No loss of image quality was reported, images were broadly comparable.

IMPLICATIONS FOR PRACTICE

This study highlights the importance of utilizing the additional copper filter in digital chest radiography.

Performance of automatic exposure control on dose and image quality: comparison between slot-scanning and flat-panel digital radiography systems

BACKGROUND

EOSedge™^* (EOS Imaging, Paris, France) is an X-ray imaging system using automatic exposure control (AEC) with tube current modulation, in order to optimize dose deposition in patients.

PURPOSE

This study aims at characterizing EOSedge organ dose deposition in comparison to a digital radiography (DR) system and the previous EOS system (EOS-1st generation), in relation to their respective image quality levels.

METHOD

Organ doses were measured in an anthropomorphic female adult phantom and a 5-year-old pediatric phantom using optically stimulated luminescence (OSL) dosimeters, which were carefully calibrated within the studied energy range. Organ doses were recorded on the EOSedge and the Fuji Visionary DRF (Fujifilm Medical Systems U.S.A., Inc, Lexington, MA). The resulting effective doses were compared to the EOS-1st-generation values present in the literature. Image quality assessment was carried out on end-user images. Quantitative image quality metrics were computed for all tested modalities on a quality assurance phantom. Qualitative assessment of EOSedge image quality was based on anthropomorphic phantom acquisitions against the EOS-1st-generation system, and on clinical images against the tested DR system.

RESULTS

For a full-spine exam, and on the female adult phantom (respectively, the pediatric phantom), an effective dose of 92 μSv (respectively, 32 μSv) was obtained on EOSedge, and 572 μSv (respectively, 179 μSv) on the DR system; these values were compared to effective dose values of 290 μSv (respectively, 200 μSv) from the literature on EOS-1st generation, leading to an effective dose reduction factor of 6 with respect to the DR system, and of 3-6 with respect to EOS-1st generation. EOSedge provides the best compromise between contrast-to-noise ratio (CNR) and dose, with more consistent CNR values than the other tested modalities, in a range of attenuation from 10 to 40 cm of poly(methyl methacrylate) (PMMA). Within this range, EOSedge is also comparable to DR for 10 and 20 cm of PMMA, and better than DR for 30 and 40 cm of PMMA, both in terms of spatial resolution and low-contrast detection. The anatomical landmarks of interest in the follow-up of spinal deformities can be detected in all tested modalities.

CONCLUSION

Results showed that EOSedge provides significant dose reduction factors for full spine imaging in both adults and children compared to the other tested modalities, without compromising image quality. We believe that this work could help raise awareness on the capabilities of modern X-ray systems, when equipped with appropriate AEC strategies, to perform ultra-low-dose, long-axis images.

Assessing the accuracy of a new 3D2D registration algorithm based on a non-invasive skin marker model for navigated spine surgery

Purpose

We assessed the accuracy of a new 3D2D registration algorithm to be used for navigated spine surgery and explored anatomical and radiologic parameters affecting the registration accuracy. Compared to existing 3D2D registration algorithms, the algorithm does not need bone-mounted or table-mounted instruments for registration. Neither does the intraoperative imaging device have to be tracked or calibrated.

Methods

The rigid registration algorithm required imaging data (a pre-existing CT scan (3D) and two angulated fluoroscopic images (2D)) to register positions of vertebrae in 3D and is based on non-invasive skin markers. The algorithm registered five adjacent vertebrae and was tested in the thoracic and lumbar spine from three human cadaveric specimens. The registration accuracy was calculated for each registered vertebra and measured with the target registration error (TRE) in millimeters. We used multivariable analysis to identify parameters independently affecting the algorithm’s accuracy such as the angulation between the two fluoroscopic images (between 40° and 90°), the detector-skin distance, the number of skin markers applied, and waist circumference.

Results

The algorithm registered 780 vertebrae with a median TRE of 0.51 mm [interquartile range 0.32–0.73 mm] and a maximum TRE of 2.06 mm. The TRE was most affected by the angulation between the two fluoroscopic images obtained (p < 0.001): larger angulations resulted in higher accuracy. The algorithm was more accurate in thoracic vertebrae (p = 0.004) and in the specimen with the smallest waist circumference (p = 0.003). The algorithm registered all five adjacent vertebrae with similar accuracy.

Conclusion

We studied the accuracy of a new 3D2D registration algorithm based on non-invasive skin markers. The algorithm registered five adjacent vertebrae with similar accuracy in the thoracic and lumbar spine and showed a maximum target registration error of approximately 2 mm. To further evaluate its potential for navigated spine surgery, the algorithm may now be integrated into a complete navigation system.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11548-022-02733-w.

Efficacy of the scatter correction algorithm in portable chest radiography

PURPOSE

Portable chest radiographs (CXRs) continue to be a vital diagnostic tool for emergency and critical care medicine. The scatter correction algorithm (SCA) is a post-processing algorithm aiming to reduce scatter within portable images. This study aimed to assess whether the SCA improved image quality (IQ) in portable CXRs.

METHODS

Objective and subjective IQ assessments were undertaken on both phantom and clinical images, respectively. For objective analysis, attenuators were placed on the anterior surface of the patient's thorax to simulate pathologies present within uniform regions of the phantom's lung and heart. Phantom CXRs were acquired with three different tube-current-times (mAs). Phantom images were processed with different SCA strengths. Contrast to noise ratios (CNR) within the attenuator were determined for each algorithm strength and compared to non-SCA images. For subjective analysis, two independent radiologists graded 30 clinical images with and without the SCA activated. The images were graded for IQ in different anatomical structures and overall diagnostic confidence.

RESULTS

Objectively, most strengths of the SCA improved the CNR in both regions. However, a detrimental effect was recorded for some algorithm strengths in regions of high contrast. Subjectively, both observers recorded the SCA significantly improved IQ in clinical CXRs in all anatomical regions. Observers indicated the greatest improvement in the lung and hilar regions, and least improvement in the chest wall and bone. All images with and without the SCA were deemed diagnostic.

CONCLUSION

This study shows the potential radiation dose neutral IQ improvement when using an SCA in clinical patient CXRs.

Efficiency of novel shielding curtains combined with pulsed irradiation for reducing radiation exposure in an operating room: Human renal collecting system phantom study

OBJECTIVE

To evaluate the impact of novel shielding curtains combined with pulsed irradiation mode to protect medical radiation workers from radiation exposure during ureteroscopy.

METHODS

0.25 mm Pb equivalent novel shielding curtains were mounted to the caudal and bilateral sides of the operating table in the ureteroscopy setting. C-arm was positioned as per normal in the operating room with the X-ray tube under the patient table. A water-filled anthropomorphic renal collecting system phantom was positioned in the standard position on the operating table that was set at a height of 100 cm. The ionization chambers were also positioned at a height of 100 cm and set in eight positions. We took measurements at distances of 50, 100, 150, and 200 cm from the phantom with the focus directed toward the X-ray tube. We measured the spatial distribution of the scattered radiation dose in four combinations: (1) continuous irradiation mode without novel shielding curtains; (2) pulsed irradiation mode (11 films per second) without novel shielding curtains; (3) continuous irradiation mode with novel shielding curtains; and (4) pulsed irradiation mode with novel shielding curtains. Continuous or pulsed irradiation was activated for 30 s each time.

RESULTS

Pulsed irradiation mode with novel shielding curtains was a significantly more efficient method than other combinations to reduce scattered radiation exposure in this study (P < 0.001). There was approximately a 95% reduction in scattered radiation exposure with the pulsed irradiation mode with novel shielding curtains set up as compared with continuous irradiation mode without novel shielding curtains.

CONCLUSION

Combining a novel shielding curtain and using a low pulse radiation setting can greatly reduce radiation exposure during ureteroscopic procedures.

Neonatal digital chest radiography- should we be using additional copper filtration?

OBJECTIVES

Copper filtration removes lower energy X-ray photons, which do not enhance image quality but would otherwise contribute to patient radiation dose. This study explores the use of additional copper filtration for neonatal mobile chest imaging.

METHODS

A controlled factorial-designed experiment was used to determine the effect of independent variables on image quality and radiation dose. These variables included: copper filtration (0 Cu, 0.1 Cu and 0.2 Cu), exposure factors, source-to-image distance and image receptor position (direct / tray). Image quality was evaluated using absolute visual grading analysis (VGA) and contrast-to-noise ratio (CNR) and entrance surface dose (ESD) was derived using an ionising chamber within the central X-ray beam.

RESULTS

VGA, CNR and ESD significantly reduced (p < 0.01) when using added copper filtration. For 0.1 Cu, the percentage reduction was much greater for ESD (60%) than for VGA (14%) and CNR (20%), respectively. When compared to the optimal combinations of parameters for incubator imaging using no copper filtration, an increase in kV and mAs when using 0.1-mm Cu resulted in better image quality at the same radiation dose (direct) or, equal image quality at reduced dose (in-tray). The use of 0.1-mm Cu for neonatal chest imaging with a corresponding increase in kV and mAs is therefore recommended.

CONCLUSION

Using additional copper filtration significantly reduces radiation dose (at increased mAs) without a detrimental effect on image quality.

ADVANCES IN KNOWLEDGE

This is the first study, using an anthropomorphic phantom, to explore the use of additional Cu for digital radiography neonatal chest imaging and therefore helps inform practice to standardise and optimise this imaging examination.

IMPACT OF COLLIMATION ON RADIATION EXPOSURE IN ADULT AND PAEDIATRIC DIGITAL X-RAY IMAGING

This study aimed to evaluate the collimation practices and quantify the overexposure due to extensive X-ray field area. The study was carried out in four digital X-ray units (including one paediatric X-ray unit). A total of 749 X-ray projections (555 adult and 194 paediatric) were evaluated. In adult X-ray units, the radiation field size was two times larger than the electronically collimated field. In the paediatric unit, the radiation field was 3.7 times larger than the electronic collimated field. The average additional entrance surface dose due to the excess radiation field used in a paediatric X-ray unit varied between 9.3 (2.5%) and 201.4 $\mu $Gy (10.9%). Therefore, proper pre-patient collimation should be applied whenever feasible, which reduces the patient radiation dose considerably.

STATUS OF RADIATION DOSE LEVELS IN PAEDIATRIC CHEST RADIOGRAPHY IN A TERTIARY HOSPITAL IN GHANA

Determination of appropriate radiation doses to paediatric patients in accordance with the as low as reasonably achievable (ALARA) principle is important, as it allows for effective optimization of imaging techniques. This study assessed the status of radiation dose levels in paediatric patients undergoing chest X-ray examinations at a tertiary hospital in Ghana. A population encompassing 86 paediatric patients categorised as infants (<1 y), young children (1-5 y) and older children (6-12 y) was selected using a quasi-experimental study design. The patients' anatomical data and X-ray beam exposure parameters were used to indirectly calculate the entrance surface doses (ESDs) received during the examinations. The infants received the highest mean ESD of 196 μGy (uncertainty = 0.37) compared to 158 μGy (uncertainty = 0.46) among the older children. The risk of developing radiation-induced biological effects was therefore higher for infant patients. The ESDs were generally higher than the internationally recommended reference doses. Careful adoption of internationally accepted exposure factors (high tube voltage and low tube load) is most recommended to optimise the dose.

Local diagnostic reference levels for routine chest X-ray examinations at a public sector hospital in central South Africa

BACKGROUND

Dose optimisation is a radiation protection guideline recommended by the International Commission on Radiological Protection (ICRP) for adherence to the 'as low as reasonably achievable' (ALARA) principle. Diagnostic reference levels (DRLs) are used to optimise patients' radiation protection for diagnostic and interventional procedures and are particularly useful for frequently performed examinations such as chest X-rays.

AIM

To establish the local diagnostic reference levels (LDRLs) for routine chest X-rays.

SETTING

Public sector hospital, Northern Cape province, South Africa.

METHODS

Sixty patients referred for chest X-rays fulfilling the inclusion criteria participated in this study. Patients were ≥ 18 years of age and weighed between 60 kg and 80 kg. Consent for participation was obtained. The entrance skin air kerma (ESAK) was measured by using the indirect method recommended by the International Atomic Energy Agency (IAEA). Statistical software (SAS version 9.2) was used to determine the LDRLs for chest X-rays in three different rooms. In two rooms, computed radiography (CR) was used and the other one was a digital radiography (DR) unit. The LDRL values at the research site were compared with various published international values.

RESULTS

LDRLs for chest X-rays were established. The CR LDRL value for the posteroanterior (PA) chest projection was higher than the DR (flat panel detector [FPD]) LDRL value. The LDRLs of the PA chest projections were 0.3 mGy for CR and 0.2 mGy for DR. The lateral (LAT) chest projection LDRL value was 0.8 mGy for both CR and DR (FPD) projections. The resultant LDRL between rooms at the research site was 0.3 mGy for PA 0.3 mGy and 0.8 mGy for LAT chest projections.

CONCLUSION

The LDRLs for chest X-rays established at this research site were lower than internationally reported DRLs. We recommend that LDRLs for routine chest X-rays should be repeated every 3 years, according to the ICRP.

CONTRIBUTION

Currently, no established or published DRL values prescribed by the Directorate of Radiation Control (DRC) are available in South Africa. The LDRLs established for routine chest X-ray examinations at this research site can serve as a guideline for the establishment of DRL values for other anatomical regions at the research site and other radiology departments in the country.

Correlation of image quality parameters with tube voltage in X-ray dark-field chest radiography: a phantom study

Grating-based X-ray dark-field imaging is a novel imaging modality with enormous technical progress during the last years. It enables the detection of microstructure impairment as in the healthy lung a strong dark-field signal is present due to the high number of air-tissue interfaces. Using the experience from setups for animal imaging, first studies with a human cadaver could be performed recently. Subsequently, the first dark-field scanner for in-vivo chest imaging of humans was developed. In the current study, the optimal tube voltage for dark-field radiography of the thorax in this setup was examined using an anthropomorphic chest phantom. Tube voltages of 50–125 kVp were used while maintaining a constant dose-area-product. The resulting dark-field and attenuation radiographs were evaluated in a reader study as well as objectively in terms of contrast-to-noise ratio and signal strength. We found that the optimum tube voltage for dark-field imaging is 70 kVp as here the most favorable combination of image quality, signal strength, and sharpness is present. At this voltage, a high image quality was perceived in the reader study also for attenuation radiographs, which should be sufficient for routine imaging. The results of this study are fundamental for upcoming patient studies with living humans.

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

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.

Inter-rater reliability in quality assurance (QA) of pediatric chest X-rays

PURPOSE

The goal of the study is to determine the inter-rater agreement on multiple factors that were utilized to evaluate the quality of pediatric chest X-ray exams from different levels of healthcare provision in an African setting.

METHODS

The image quality of pediatric chest X-rays from 3 South African medical centers of varying level of healthcare service were retrospectively assessed by 3 raters for 12 quality factors including: (1) absent body parts; (2) under inspiration; (3) patient rotation; (4) scapula in the way; (5) patient kyphosis/lordosis; (6) artefact/foreign body; (7) central vessel visualization; (8) peripheral vessels visualization; (9) poor collimation; and (10) trachea and bronchi visualization; (11) post-cardiac vessel visualization; and (12) absent or wrong image orientation. Analysis was performed using the Brennan--Prediger coefficient of agreement for inter-rater reliability and Cochran's Q statistic and McNemar's test for inter-rater bias.

RESULTS

1077 X-rays were reviewed. The least difference between observers in the frequency of the errors was noticed for factors (1) absent body parts and (12) absent or wrong image orientation with almost perfect agreement between raters. κ score for these two factors among all raters and between each pair of raters was more than 0.95 with no significant inter-rater bias. Conversely, there was poor agreement for the remaining factors with the least agreed on being factor (3) patient rotation with a κ score of 0.23. This was followed by factors (2) under inspiration (κ score of 0.32) and factors (4) scapula in the way (κ score of 0.35) respectively. There was significant inter-rater bias for all these three factors.

CONCLUSION

Many of the factors used to assess the quality of a chest X-ray in children demonstrate poor reliability despite mitigation against variations in training, standard quality definitions and level of healthcare service provision. New definitions, objective measures and recording tools for assessing pediatric chest radiographic quality are required.

[Relationship between Radiation Quality and Image Quality in Digital Chest Radiography: Validation Study Using Human Soft Tissue-equivalent Phantom]

PURPOSE

To evaluate image quality for chest radiography at different radiation qualities, using phantoms with scatter fractions similar to those of lungs.

METHODS

Two base phantoms with 10 and 4 cm thicknesses, respectively, made of a soft tissue-equivalent material, were used to mimic the X-ray attenuation of the human lung. Two plates with soft tissue- and bone-equivalent materials, respectively, were placed on the base phantom as contrast objects. The image data were obtained with the same entrance surface dose in each radiation quality. Six radiation qualities generated using 120 and 90 kV, and additional copper filters with thicknesses 0, 0.1, and 0.2 mm were selected. The signal-difference-to-noise ratio (SdNR) and a contrast ratio of the soft tissue to the bone were measured for the six radiation qualities.

RESULTS

The thicker the additional filter, the better the SdNR at both tube voltages. The SdNR values were not significantly different between 120 and 90 kV for the same filter thickness. The contrast ratio was higher at 120 than at 90 kV by approximately 8%.

CONCLUSIONS

Because of the advantage of the contrast ratio and the highest SdNR, the radiation quality with 120 kV and 0.2-mm copper filtration was the best. It was indicated that the conventional tube voltage of 120 kV remains to be better than the lower tube voltage of 90 kV.

Modifications to mobile chest radiography technique during the COVID-19 pandemic - implications of X-raying through side room windows

INTRODUCTION

Modifications to common radiographic techniques have resulted from the challenges presented by the COVID-19 pandemic. Reports exist regarding the potential benefits of undertaking mobile radiography through side room windows. The aim of this study was to evaluate the impact on image quality and exposure factors when undertaking such examinations.

METHODS

A phantom based study was undertaken using a digital X-ray room. Control acquisitions, using a commercially available image quality test tool, were performed using standard mobile chest radiography acquisition factors. Image quality (physical and visual), incidence surface air kerma (ISAK), Exposure Index (EI) and Deviation Index (DI) were recorded. Image quality and radiation dose were further assessed for two additional (experimental) scenarios, where a side room window was located immediately adjacent to the exit port of the light beam diaphragm. The goal of experimental scenario one was to modify exposure factors to maintain the control ISAK. The goal of experimental scenario two was to modify exposure factors to maintain the control EI and DI. Dose and image quality data were compared between the three scenarios.

RESULTS

To maintain the pre-window (control) ISAK (76 μGy), tube output needed a three-fold increase (90 kV/4 mAs versus 90 kV/11.25 mAs). To maintain EI/DI a more modest increase in tube output was required (90 kV/8 mAs/ISAK 54 μGy). Physical and visual assessments of spatial resolution and signal-to-noise ratio were indifferent between the three scenarios. There was a slight statistically significant reduction in contrast-to-noise ratio when imaging through the glass window (2.3 versus 1.4 and 1.2; P = 0.005).

CONCLUSION

Undertaking mobile X-ray examinations through side room windows is potentially feasible but does require an increase in tube output and is likely to be limited by minor reductions in image quality.

IMPLICATIONS FOR PRACTICE

Mobile examinations performed through side room windows should only be used in limited circumstances and future clinical evaluation of this technique is warranted.

Review of Artificial Intelligence Techniques in Imaging Data Acquisition, Segmentation, and Diagnosis for COVID-19

The pandemic of coronavirus disease 2019 (COVID-19) is spreading all over the world. Medical imaging such as X-ray and computed tomography (CT) plays an essential role in the global fight against COVID-19, whereas the recently emerging artificial intelligence (AI) technologies further strengthen the power of the imaging tools and help medical specialists. We hereby review the rapid responses in the community of medical imaging (empowered by AI) toward COVID-19. For example, AI-empowered image acquisition can significantly help automate the scanning procedure and also reshape the workflow with minimal contact to patients, providing the best protection to the imaging technicians. Also, AI can improve work efficiency by accurate delineation of infections in X-ray and CT images, facilitating subsequent quantification. Moreover, the computer-aided platforms help radiologists make clinical decisions, i.e., for disease diagnosis, tracking, and prognosis. In this review paper, we thus cover the entire pipeline of medical imaging and analysis techniques involved with COVID-19, including image acquisition, segmentation, diagnosis, and follow-up. We particularly focus on the integration of AI with X-ray and CT, both of which are widely used in the frontline hospitals, in order to depict the latest progress of medical imaging and radiology fighting against COVID-19.

Deep Convolutional Approaches for the Analysis of COVID-19 Using Chest X-Ray Images From Portable Devices

The recent human coronavirus disease (COVID-19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given the effects of COVID-19 in pulmonary tissues, chest radiography imaging plays an important role in the screening, early detection, and monitoring of the suspected individuals. Hence, as the pandemic of COVID-19 progresses, there will be a greater reliance on the use of portable equipment for the acquisition of chest X-ray images due to its accessibility, widespread availability, and benefits regarding to infection control issues, minimizing the risk of cross-contamination. This work presents novel fully automatic approaches specifically tailored for the classification of chest X-ray images acquired by portable equipment into 3 different clinical categories: normal, pathological, and COVID-19. For this purpose, 3 complementary deep learning approaches based on a densely convolutional network architecture are herein presented. The joint response of all the approaches allows to enhance the differentiation between patients infected with COVID-19, patients with other diseases that manifest characteristics similar to COVID-19 and normal cases. The proposed approaches were validated over a dataset specifically retrieved for this research. Despite the poor quality of the chest X-ray images that is inherent to the nature of the portable equipment, the proposed approaches provided global accuracy values of 79.62%, 90.27% and 79.86%, respectively, allowing a reliable analysis of portable radiographs to facilitate the clinical decision-making process.

Optimisation of radiographic acquisition parameters for direct digital radiography: A systematic review

INTRODUCTION

The objective of this systematic review was to uncover and synthesise all available literature regarding appropriate acquisition parameters for direct digital radiography. It sought to either confirm current practices as optimal, or to uncover practices that may produce more optimised results.

METHODS

A comprehensive search of published and unpublished literature was undertaken to find studies that evaluated how adjustment of different acquisition parameters affected subjective image quality and patient radiation dose. Eight hundred and fifty-eight studies were retrieved for title and abstract screening. Eighty-nine studies were retrieved for full-text screening, and 23 were included for review and methodological quality screening.

RESULTS

Narrative synthesis of the 23 included studies revealed limited evidence to guide any potential change or acceptance of currently accepted best practice. Meta-analysis was unable to be performed for any of the included studies due to high levels of methodological heterogeneity. A key finding of this review was that the goals of optimisation research varied greatly across the included studies.

CONCLUSION

Significant methodological heterogeneity in the included studies limited the number of clinically relevant findings that would give evidence to an acceptance of, or suggest changes to, currently accepted best practice. Improving consistency in approach across future works of technique optimisation will ensure future systematic reviews will be able to provide strong evidence and meta-analysis will be able to be performed.

IMPLICATIONS FOR CLINICAL PRACTICE

This review highlights that in the literature, studies of optimisation of radiographic acquisition parameters have varying goals. This methodological heterogeneity limits the applicability of systematic reviews and precludes the use of meta-analysis. The authors recommend that a framework for optimisation research be produced as a priority to help improve homogeneity in future research.

Does dose optimisation in digital panoramic radiography affect diagnostic performance?

OBJECTIVES

To compare the overall diagnostic performance of digital panoramic radiographs obtained with low-dose protocols and to estimate the absorbed dose in the head and neck.

MATERIALS AND METHODS

Forty-eight panoramic radiographs were obtained from eight imaging phantoms using six exposure protocols of progressively lower tube voltages (kVp) and currents (mA), as follows: (1) 70 kVp and 12.5 mA, (2) 66 kVp and 10 mA, (3) 66 kVp and 8 mA, (4) 66 kVp and 5 mA, (5) 66 kVp and 4 mA and (6) 66 kVp and 3.2 mA. Five oral radiologists independently evaluated the images and reported all detectable radiographic findings. Intra-examiner reproducibility was assessed by re-evaluation of 25% of the images. The data were analysed using the McNemar and weighted Kappa tests. Absorbed doses of the six protocols were obtained from thermoluminescent dosimeters placed inside a Rando phantom and compared using one-way ANOVA with post hoc Tukey (α = 0.05).

RESULTS

The overall diagnostic performance of panoramic radiographs obtained with low-dose protocols did not differ from that of panoramic radiographs obtained with the highest dose (p > 0.05). Moreover, substantial agreement was observed between all protocols. Protocol 1 resulted in the highest absorbed dose and protocols 4, 5 and 6 in the lowest absorbed doses, with the difference being significant (p ≤ 0.05).

CONCLUSION

Although digital panoramic radiography is considered a relatively low-dose examination, the radiation dose can be further reduced without negatively affecting its overall diagnostic performance.

CLINICAL RELEVANCE

Considering the risks associated with X-rays, digital panoramic radiographs can be obtained at even lower exposure levels.

Evaluating the principles of radiation protection in diagnostic radiologic examinations: collimation, exposure factors and use of protective equipment for the patients and their companions

INTRODUCTION

Producing appropriate diagnostic images along with patient radiation protection is the goal of radiography. Due to the advancements of radiography, concerns about observing the principles of radiation protection exist. Therefore, this study aimed to evaluate the observance of the principles of radiation protection in radiographic examinations with emphasis on field size collimation, suitability of exposure factors and the use of protective equipment for the patients and their companions.

METHODS

Using a cross-sectional study design, two radiography students on their final year of study observed 100 radiographic examinations from the imaging departments of five educational hospitals. The SPSS version 24 software was used to analyse the results.

RESULTS

The radiation field collimation was obtained in 46% of the studied radiographs. Patients had companions present during the examination in 26% of the studies; however, protective equipment was only used for 4% of the patients' companions, and no protective equipment was applied for patients. The observance rate of the various principles of radiation protection including field size restriction, the use of protective equipment for the patients and their companions, and suitability of the selected exposure factors was on average 44.6%.

CONCLUSION

The observance rate of the principles of radiation protection was insufficient in the studied educational hospitals, specifically in field size collimation and the use of protective equipment for the patients and their companions. Therefore, emphasis on the strict implementation of the radiation protection guidelines and continuous training of radiographers are required.

Design of band-pass filters in fluoroscopy by experimental and simulation methods for the 40 keV energy X-ray

This study was carried out empirical computational and to design filters that while eliminating low-energy radiations according to the conventional methods attenuate high-energy beams that do not fundamentally affect images quality improvement and the absorbed patient dose reduction as well. In this regard, the impacts of thickness and filter material were examined on the contrast, resolution, absorbed patient dose, and image quality. We found that the use of filters increases the resolution, image quality and reduces the output dose intensity greatly, and the 0.1 mm thickness tin element was selected as the most suitable element for the filter.

A comparison of perceived diagnostic image quality in direct digital panoramic images between standard and advanced external GOP image processing

Objective: The objective of the present study was to study the effect of adaptive image processing (GOP processing) on the visibility of anatomical structures in direct digital panoramic images. Material and methods: The study comprised panoramic images of 50 consecutive adult individuals aged 18-60 years. Nine dentists working with dental radiology compared the structural image quality of all standard-processed and GOP-processed panoramic images for six anatomical structures, using a six-point scale for visual grading characteristics analysis. Results: For all anatomic structures a statistically significant difference in favour of the GOP was found. Conclusions: The present study shows that it is possible to improve perceived diagnostic image quality of direct digital panoramic radiography using GOP technology compared to the manufacturers' standard processing. Manufacturers' image-processing programs can be further developed, as there is a possibility of improving the perceived diagnostic content of an image with external processing.

Optimization of tube voltage in X-ray dark-field chest radiography

Grating-based X-ray dark-field imaging is a novel imaging modality which has been refined during the last decade. It exploits the wave-like behaviour of X-radiation and can nowadays be implemented with existing X-ray tubes used in clinical applications. The method is based on the detection of small-angle X-ray scattering, which occurs e.g. at air-tissue-interfaces in the lung or bone-fat interfaces in spongy bone. In contrast to attenuation-based chest X-ray imaging, the optimal tube voltage for dark-field imaging of the thorax has not yet been examined. In this work, dark-field scans with tube voltages ranging from 60 to 120 kVp were performed on a deceased human body. We analyzed the resulting images with respect to subjective and objective image quality, and found that the optimum tube voltage for dark-field thorax imaging at the used setup is at rather low energies of around 60 to 70 kVp. Furthermore, we found that at these tube voltages, the transmission radiographs still exhibit sufficient image quality to correlate dark-field information. Therefore, this study may serve as an important guideline for the development of clinical dark-field chest X-ray imaging devices for future routine use.

Impact of body part thickness on AP pelvis radiographic image quality and effective dose

INTRODUCTION

Within medical imaging variations in patient size can generate challenges, especially when selecting appropriate acquisition parameters. This experiment sought to evaluate the impact of increasing body part thickness on image quality (IQ) and effective dose (E) and identify optimum exposure parameters.

METHODS

An anthropomorphic pelvis phantom was imaged with additional layers (1-15 cm) of animal fat as a proxy for increasing body thickness. Acquisitions used the automatic exposure control (AEC), 100 cm source to image distance (SID) and a range of tube potentials (70-110 kVp). IQ was evaluated physically and perceptually. E was estimated using PCXMC software.

RESULTS

For all tube potentials, signal to noise ratio (SNR) and contrast to noise ratio (CNR) deceased as body part thickness increased. 70 kVp produced the highest SNR (46.6-22.6); CNR (42.8-17.6). Visual grading showed that the highest IQ scores were achieved using 70 and 75 kVp. As thickness increases, E increased exponentially (r = 0.96; p < 0.001). Correlations were found between visual and physical IQ (SNR r = 0.97, p < 0.001; CNR r = 0.98, p < 0.001).

CONCLUSION

To achieve an optimal IQ across the range of thicknesses, lower kVp settings were most effective. This is at variance with professional practice as there is a tendency for radiographers to increase kVp as thickness increases. Dose reductions were experienced at higher kVp settings and are a valid method for optimisation when imaging larger patients.

Antero-posterior (AP) pelvis x-ray imaging on a trolley: Impact of trolley design, mattress design and radiographer practice on image quality and radiation dose

INTRODUCTION

Physical and technical differences exist between imaging on an x-ray tabletop and imaging on a trolley. This study evaluates how trolley imaging impacts image quality and radiation dose for an antero-posterior (AP) pelvis projection whilst subsequently exploring means of optimising this imaging examination.

METHODS

An anthropomorphic pelvis phantom was imaged on a commercially available trolley under various conditions. Variables explored included two mattresses, two image receptor holder positions, three source to image distances (SIDs) and four mAs values. Image quality was evaluated using relative visual grading analysis with the reference image acquired on the x-ray tabletop. Contrast to noise ratio (CNR) was calculated. Effective dose was established using Monte Carlo simulation. Optimisation scores were derived as a figure of merit by dividing effective dose with visual image quality scores.

RESULTS

Visual image quality reduced significantly (p < 0.05) whilst effective dose increased significantly (p < 0.05) for images acquired on the trolley using identical acquisition parameters to the reference image. The trolley image with the highest optimisation score was acquired using 130 cm SID, 20 mAs, the standard mattress and platform not elevated. A difference of 12.8 mm was found between the image with the lowest and highest magnification factor (18%).

CONCLUSION

The acquisition parameters used for AP pelvis on the x-ray tabletop are not transferable to trolley imaging and should be modified accordingly to compensate for the differences that exist. Exposure charts should be developed for trolley imaging to ensure optimal image quality at lowest possible dose.

Radiographer Delivered Fluoroscopy Reduces Radiation Exposure During Endoscopic Urological Procedures

INTRODUCTION

The 1999 Ionising Radiation Regulations recommend that medical professionals using ionising radiation should aim to keep exposure as 'low as reasonably practicable'. Urologists regularly use fluoroscopy during endoscopic surgical procedures. In some institutions, this is delivered by a radiographer whereas in others, it is delivered by the urological surgeon.

OBJECTIVES

To determine if radiographer-delivered fluoroscopy can reduce the exposure to ionising radiation during urological procedures.

METHODS

An analysis of 395 consecutive patients, who underwent endoscopic urological procedures requiring fluoroscopy, was performed simultaneously across two institutions, over a 4 month period. 321 patients were matched and included in the analysis.

RESULTS

Radiographer delivered fluoroscopy was associated with reduced ionising radiation exposure for retrograde pyelography procedures ED 0.09626 vs. 1.323 mSev, p= 0.0003, and endoscopic stone surgeries ED 0.3066 Vs. 0.5416 mSev, p=0.0039, but not for ureterorenoscopic stone surgeries 0.4880 vs. 0.2213 mSev, p=0.8292.

CONCLUSION

Radiographer delivered fluoroscopy could reduce the patient's exposure to ionising radiation for some urological procedures.

Optimization of image quality and patient dose in radiographs of paediatric extremities using direct digital radiography

OBJECTIVE

The purpose of this study was to evaluate the effect of beam quality on the image quality (IQ) of ankle radiographs of paediatric patients in the age range of 0-1 year whilst maintaining constant effective dose (ED).

METHODS

Lateral ankle radiographs of an infant foot phantom were taken at a range of tube potentials (40.0-64.5 kVp) with and without 0.1-mm copper (Cu) filtration using a Trixell Pixium 4600 detector (Trixell, Morains, France). ED to the patient was computed for the default exposure parameters using PCXMC v. 2.0 and was fixed for other beam qualities by modulating the tube current-time product. The contrast-to-noise ratio (CNR) was measured between the tibia and adjacent soft tissue. The IQ of the phantom images was assessed by three radiologists and a reporting radiographer. Four IQ criteria were defined each with a scale of 1-3, giving a maximum score of 12. Finally, a service audit of clinical images at the default and optimum beam qualities was undertaken.

RESULTS

The measured CNR for the 40 kVp/no Cu image was 12.0 compared with 7.6 for the default mode (55  0.1 mm Cu). An improvement in the clinical IQ scores was also apparent at this lower beam quality.

CONCLUSION

Lowering tube potential and removing filtration improved the clinical IQ of paediatric ankle radiographs in this age range.

ADVANCES IN KNOWLEDGE

There are currently no UK guidelines on exposure protocols for paediatric imaging using direct digital radiography. A lower beam quality will produce better IQ with no additional dose penalty for infant extremity imaging.

Effect of Different Tube Potential Settings on Caries Detection using PSP Plate and Conventional Film

PURPOSE

To compare intraoral Phosphor Stimulable Plate digital system and intraoral film using different tube settings on incipient proximal caries detection.

MATERIALS AND METHODS

Five blocks, with five teeth each, were radiographically examined using phosphor plates and F-speed films. The images were acquired in 07 different tube potentials from 50-80 kV. The films were digitized. Three oral radiologists scored the images for the presence of caries using a 5-point rating scale. The areas under ROC curve were calculated. The influence of tube kilovoltage was verified by ANOVA and pair wise comparisons performed using Tukey test.

RESULTS

Mean ROC curve areas varied from 0.446-0.628 for digital images and 0.494-0.559 for conventional images. The tube setting of 70 kV presented the best result both for digital and conventional images. Considering the image type separately, 70 kV scored highest followed by 75 and 65 kV for digital images (p=0.084). For conventional image modality, even though 70 kV presented the best result, it did not differ significantly from 80 kV, not differing from 60 and 55 kV, which did not differ from 75, 65 and 50 kV (p=0.53).

CONCLUSION

Phosphor plate digital images seem to be more susceptible to tube setting potential variations then digitized film images.

Dose Optimization in Lumbar Spine Radiographic Examination by Air Gap Method at CR and DR Systems: A Phantom Study

OBJECTIVE

This study aims at investigating the feasibility of replacing an antiscatter grid with an air gap to achieve dose reduction for lumbar spine radiography while retaining image quality at an acceptable diagnostic level.

METHODS

Frontal and lateral projections of lumbar spine radiographic examinations were performed on an anthropomorphic phantom. Nongrid images of both the computed radiography (CR) and digital radiography (DR) systems with air gap thickness ranging from 0 to 25 cm were produced and compared with their corresponding grid images. Dose measurements using thermoluminescent dosimeters at the ovary and testes regions of the phantom were conducted. The image quality of all the images was evaluated by five radiographers using image quality score and visual grading analysis tests. Data on dose measurements and image quality tests were input for statistical analysis. The dose area product (DAP) of all the examinations was recorded and input for the computation of effective doses using a PC-based Monte Carlo program (PCXMC 2.0; STUK, Helsinki, Finland).

RESULTS

Significant dose reduction effects on the ovaries of 60.2%-74.1% and 55.1%-73.3% were found, respectively, at the frontal and lateral projections of nongrid lumbar spine examinations compared with their corresponding grid ones in both the CR and DR systems. Results on the image quality score and visual grading analysis tests showed that nongrid images with 10-cm and 5-cm of air gap thicknesses respective to the frontal and lateral images of the lumbar spine were rated with the highest scores. In general, a dose reduction effect using the air gap method was found to be more pronounced in the CR system compared with the DR system. Nevertheless, the CR system delivered a 2.4-4.5 times higher ovary dose respective to the frontal and lateral projections of lumbar spine examinations compared with the DR system.

CONCLUSIONS

Ten and 5 centimeters were found to be the optimal air gap thicknesses respective to the frontal and lateral lumbar spine radiographic examinations of the tested Rando phantom (Alderson Laboratories, Stamford, CT) in both the CR and DR systems. Significant dose reduction effects on both the ovary and testes regions of the nongrid examinations were shown. The effective dose computed from PCMCX 2.0 reflected that the risk of cancer induction was halved when an antiscatter grid was replaced by the nongrid method with an optimal air gap thickness in the tested examinations. Further reduction on cancer risk could be achieved by using DR instead of the CR system.

Radiographers' professional knowledge regarding parameters and safety issues in plain radiography: a questionnaire survey

OBJECTIVE

To review the knowledge of radiographers and examine the possible sociodemographic and situational contributors to this knowledge.

METHODS

A questionnaire survey was devised and distributed to a cohort of 120 radiographers. Each questionnaire contained two sections. In the first section, background data, including sex, age, highest academic level, grade point average (GPA), length of time from graduation, work experience as a radiographer and the status of previous refresher course(s), were collected. The second section contained 17 multiple-choice questions concerning radiographic imaging parameters and safety issues.

RESULTS

The response rate was 63.8%. In univariate analytic model, higher academic degree (p < 0.001), higher GPA (r(2) = 0.11; p = 0.001), academic workplace (p = 0.04) and taking previous refresher course(s) (p = 0.01) were significantly associated with higher knowledge score. In multivariate analytic model, however, higher academic degree (B = 1.62; p = 0.01), higher GPA (B = 0.50; p = 0.01) and taking previous refresher course(s) (B = -1.26; p = 0.03) were independently associated with higher level of knowledge. Age, sex, length of time from graduation and work experience were not associated with the respondents' knowledge score.

CONCLUSION

Academic background is a robust indicator of a radiographer's professional knowledge. Refresher courses and regular knowledge assessments are highly recommended.

ADVANCES IN KNOWLEDGE

This is the first study in the literature that examines professional knowledge of radiographers in terms of technical and safety issues in plain radiography. Academic degree, GPA and refresher courses are independent predictors of this knowledge. Regular radiographer professional knowledge checks may be recommended.