Dose reduction in patients undergoing chest imaging: digital amorphous silicon flat-panel detector radiography versus conventional film-screen radiography and phosphor-based computed radiography

Effectiveness of one-shot dual-energy subtraction chest radiography with flat-panel detector in distinguishing between calcified and non-calcified nodules

The purpose of this study was to evaluate the added value of the soft tissue image obtained by the one-shot dual-energy subtraction (DES) method using a flat-panel detector compared with the standard image alone in distinguishing calcified from non-calcified nodules on chest radiographs. We evaluated 155 nodules (48 calcified and 107 non-calcified) in 139 patients. Five radiologists (readers 1 - 5) with 26, 14, 8, 6 and 3 years of experience, respectively, evaluated whether the nodules were calcified using chest radiography. CT was used as the gold standard of calcification and non-calcification. Accuracy and area under the receiver operating characteristic curve (AUC) were compared between analyses with and without soft tissue images. The misdiagnosis ratio (false positive plus false negative ratios) when nodules and bones overlapped was also examined. The accuracy of all radiologists increased after adding soft tissue images (readers 1 - 5: 89.7% vs. 92.3% [P = 0.206], 83.2% vs. 87.7% [P = 0.178], 79.4% vs. 92.3% [P < 0.001], 77.4% vs. 87.1% [P = 0.007], and 63.2% vs. 83.2% [P < 0.001], respectively). AUCs for all the readers improved, except for reader 2 (readers 1 - 5: 0.927 vs. 0.937 [P = 0.495], 0.853 vs. 0.834 [P = 0.624], 0.825 vs. 0.878 [P = 0.151], 0.808 vs. 0.896 [P < 0.001], and 0.694 vs. 0.846 [P < 0.001], respectively). The misdiagnosis ratio for nodules that overlapped with the bone decreased after adding soft tissue images in all readers (11.5% vs. 7.6% [P = 0.096], 17.6% vs. 12.2% [P = 0.144], 21.4% vs. 7.6% [P < 0.001], 22.1% vs. 14.5% [P = 0.050] and 35.9% vs. 16.0% [P < 0.001], respectively), particularly that of readers 3 - 5. In conclusion, the soft tissue images obtained using one-shot DES with a flat-panel detector have added value in distinguishing calcified from non-calcified nodules on chest radiographs, especially for less experienced radiologists.

Relationship between the visual evaluation of pathology visibility and the physical measure of low contrast detail detectability in neonatal chest radiography

INTRODUCTION

The detectability of low contrast detail (LCD) is a method used to assess image quality (IQ) in neonatal radiography; however, there is a lack of data on the relationship between LCD detectability and visual IQ. The study aims at investigating the relationship between the LCD detectability and visual IQ and pathology visibility (PV).

METHODS

Several acquisition parameters were employed to obtain a group of images from a neonatal Gammex chest phantom. Three observers applied relative visual grading analysis (VGA) for assessing the IQ and PV. A simulated pneumothorax visibility (PNV) and simulated hyaline membrane disease visibility (HMV) represented PV. Next, a CDRAD 2.0 phantom was radiographed utilising the same acquisition protocols, and several paired images were obtained. With the use of CDRAD analyser software, the detectability of LCD was assessed and expressed by an image quality figure inverse (IQFi_inv) metric. The correlation between the IQF_inv and each of IQ, PNV and HMV was examined.

RESULTS

The physical measure (IQF_inv) and the visual assessment of IQ were shown to be strongly correlated (r = 0.95; p < 0.001). Using Pearson's correlation, the IQF_inv, PNV, and HMV were found to be strongly correlated (r = 0.94; p < 0.001) and (r = 0.92; p < 0.001), correspondingly.

CONCLUSION

Results of the study show that physical measures of LCD detectability utilising the CDRAD 2.0 phantom is strongly corelated with visual IQ and PV (PNV and HMV) and can be used to evaluate IQ when undertaking neonatal chest radiography (CXR).

IMPLICATIONS FOR PRACTICE

This study establishes the feasibility of utilising the physical measure (IQF_inv) and the CDRAD 2.0 phantom in routine quality assurance and neonatal CXR optimisation studies.

Detection of pulmonary nodules with scoutless fixed-dose ultra-low-dose CT: a prospective study

OBJECTIVES

To determine the accuracy of scoutless, fixed-dose ultra-low-dose (ULD) CT compared to standard-dose (SD) CT for pulmonary nodule detection and semi-automated nodule measurement, across different patient sizes.

METHODS

Sixty-three patients underwent ULD and SD CT. Two readers examined all studies visually and with computer-aided detection (CAD). Nodules detected on SD CT were included in the reference standard by consensus and stratified into 4 categories (nodule category, NODCAT) from the Dutch-Belgian Lung Cancer Screening trial (NELSON). Effects of NODCAT and patient size on nodule detection were determined. For each nodule, volume and diameter were compared between both scans.

RESULTS

The reference standard comprised 173 nodules. For both readers, detection rates on ULD versus SD CT were not significantly different for NODCAT 3 and 4 nodules > 50 mm³ (reader 1: 93% versus 89% (p = 0.257); reader 2: 96% versus 98% (p = 0.317)). For NODCAT 1 and 2 nodules < 50 mm³, detection rates on ULD versus SD CT dropped significantly (reader 1: 66% versus 80% (p = 0.023); reader 2: 77% versus 87% (p = 0.039)). Body mass index and chest circumference did not influence nodule detectability (p = 0.229 and p = 0.362, respectively). Calculated volumes and diameters were smaller on ULD CT (p < 0.0001), without altering NODCAT (84% agreement).

CONCLUSIONS

Scoutless ULD CT reliably detects solid lung nodules with a clinically relevant volume (> 50 mm³) in lung cancer screening, irrespective of patient size. Since detection rates were lower compared to SD CT for nodules < 50 mm³, its use for lung metastasis detection should be considered on a case-by-case basis.

KEY POINTS

• Detection rates of pulmonary nodules > 50 mm³are not significantly different between scoutless ULD and SD CT (i.e. volumes clinically relevant in lung cancer screening based on the NELSON trial), but were different for the detection of nodules < 50 mm³(i.e. volumes still potentially relevant in lung metastasis screening). • Calculated nodule volumes were on average 0.03 mL or 9% smaller on ULD CT, which is below the 20-25% interscan variability previously reported with software-based volumetry. • Even though a scoutless, fixed-dose ULD CT protocol was used (CTDI_vol0.15 mGy), pulmonary nodule detection was not influenced by patient size.

[Usefulness of Combining Post-processing Scatter Correction and an Anti-scatter Grid in Chest Standing Radiography]

PURPOSE

The aim of this study was to evaluate the usefulness of combining post-processing scatter correction (IG) and an anti-scatter grid (RG) in chest radiography.

METHOD

To determine the combination protocol (Hyb) that was closed to RG 12:1 (RG12), we measured the content rate of scattered radiation for each combination (RG12, IG12, RG3-12+IG3-12). Task-based modulation transfer function (MTF_Task) and SDNR were evaluated using RG12, IG12, and Hyb. Additionally, seven radiologists performed visual evaluation by using chest phantom.

RESULT

The protocol of Hyb was RG8+IG3. In SDNR, Hyb (RG8+IG3) was equal to or higher than RG12, and MTF_Task was equal in all grid systems. Hyb (RG8+IG3) was significantly superior to RG12 in visual evaluation.

CONCLUSION

The combining post-processing scatter correction should be useful for improving inspection throughput and reducing the risk of grid's damage.

Neonatal chest radiography: Influence of standard clinical protocols and radiographic equipment on pathology visibility and radiation dose using a neonatal chest phantom

INTRODUCTION

Little is known about the variations in pathology visibility (PV) and their corresponding radiation dose values for neonatal chest radiography, between and within hospitals. Large variations in PV could influence the diagnostic outcome and the variations in radiation dose could affect the risk to patients. The aim of this study is to compare the PV and radiation dose for standard neonatal chest radiography protocols among a series of public hospitals.

METHODS

A Gammex 610 neonatal chest phantom was used to simulate the chest region of neonates. Radiographic acquisitions were conducted on 17 X-ray machines located in eight hospitals, utilising their current neonatal chest radiography protocols. Six qualified radiographers assessed PV visually using a relative visual grading analysis (VGA). Signal to noise ratios (SNR) and contrast to noise ratios (CNR) were measured as a measure of image quality (IQ). Incident air kerma (IAK) was measured using a solid-state dosimeter.

RESULTS

PV and radiation dose varied substantially between and within hospitals. For PV, the mean (range) VGA scores, between and within the hospitals, were 2.69 (2.00-3.50) and 2.73 (2.33-3.33), respectively. For IAK, the mean (range), between and within the hospitals, were 24.45 (8.11-49.94) μGy and 34.86 (22.26-49.94) μGy, respectively.

CONCLUSION

Between and within participating hospitals there was wide variation in the visibility of simulated pathology and radiation dose (IAK).

IMPLICATIONS FOR PRACTICE

X-ray units with lower PV and higher doses require optimisation of their standard clinical protocols. Institutions which can offer acceptable levels of PV but with lower radiation doses should help facilitate national optimisation processes.

EYE LENS DOSES OF RADIOLOGY TECHNOLOGISTS WHO ASSIST PATIENTS DURING RADIOGRAPHY

The International Commission on Radiological Protection (ICRP) revised a drastic decrease of the annual eye equivalent dose limit. The present study aimed to evaluate the amounts of radiation to which the eye lenses of radiological technologists (RT) become exposed and the effects of wearing lead glasses on dose reduction while assisting patients during radiographic assessments. Lens equivalent doses (Hp(3)) were measured at the neck using personal dosemeter. In addition, Hp(3) was estimated by converting air kerma determined using small optically stimulated luminescence (OSL) dosemeters at six positions on lead glasses near the eyes and at the neck. The estimated mean Hp(3) from personal dosemeter at the neck varied from 3.92 to 18.6 mSv/y. Compare to OSL for which the dose varies from 8.95 to 54.75 mSv/y, personal dosimeter underestimate Hp(3).Therefore, Hp(3) for RT might exceed the revised eye equivalent dose limit 20 mSv/y recommended by the ICRP.

Needle-based storage-phosphor detector radiography is superior to a conventional powder-based storage phosphor detector and a high-resolution screen-film system in small patients (budgerigars and mice)

This method comparison study used radiographs of 20 mice and 20 budgerigars to investigate comparability between computed radiography (CR) and high-resolution screen-film systems and study the effects of reduced radiation doses on image quality of digital radiographs of small patients. Exposure settings used with the mammography screen-film system (SF) were taken as baseline settings. A powder-based storage-phosphor system (CR_P) and a needle-based storage-phosphor system (CR_N) were used with the same settings (D/100%) and half the detector dose (D/50%). Using a scoring system four reviewers assessed five criteria per species covering soft tissue and bone structures. Results were evaluated for differences between reviewers (interobserver variability), systems and settings (intersystem variability, using visual grading characteristic analysis). Correlations were significant (p ≤ 0.05) for interobserver variability in 86.7% of the cases. Correlation coefficients ranged from 0.206 to 0.772. For mice and budgerigars, the CR_N system was rated as superior to the SF and CR_P system for most criteria, being significant in two cases each. Comparing the SF and CR_P system, the conventional method scored higher for all criteria, in one case significantly. For both species and both digital systems, dose reduction to 50% resulted in significantly worse scores for most criteria. In summary, the needle-based storage-phosphor technique proved to be superior compared to the conventional storage-phosphor and mammography screen-film system. Needle-based detector systems are suitable substitutes for high-resolution screen–film systems when performing diagnostic imaging of small patients. Dose reduction to 50% of the corresponding dose needed in high-resolution film-screen systems cannot be recommended.

A novel method for comparing radiation dose and image quality, between and within different x-ray units in a series of hospitals

OBJECTIVES

To develop a novel method for comparing radiation dose and image quality (IQ) to evaluate adult chest x-ray (CXR) imaging among several hospitals.

METHODS

CDRAD 2.0 phantom was used to acquire images in eight hospitals (17 digital x-ray units) using local adult CXR protocols. IQ was represented by image quality figure inverse (IQF_inv), measured using CDRAD analyser software. Signal to noise ratio, contrast to noise ratio and conspicuity index were calculated as additional measures of IQ. Incident air kerma (IAK) was measured using a solid-state dosimeter for each acquisition. Figure of merit (FOM) was calculated to provide a single estimation of IQ and radiation dose.

RESULTS

IQ, radiation dose and FOM varied considerably between hospitals and x-ray units. For IQF_inv, the mean (range) between and within the hospitals were 1.42 (0.83-2.18) and 1.87 (1.52-2.18), respectively. For IAK, the mean (range) between and within the hospitals were 93.56 (17.26-239.15) μGy and 180.85 (122.58-239.15) μGy, respectively. For FOM, the mean (range) between and within hospitals were 0.05 (0.01-0.14) and 0.03 (0.02-0.05), respectively.

CONCLUSIONS

The suggested method for comparing IQ and dose using FOM concept along with the new proposed FOM, is a valid, reliable and effective approach for monitoring and comparing IQ and dose between and within hospitals. It is also can be beneficial for the optimisation of x-ray units in clinical practice. Further optimisation for the hospitals/x-ray units with low FOM are required to minimise radiation dose without degrading IQ.

An investigation into the validity of utilising the CDRAD 2.0 phantom for optimisation studies in digital radiography

OBJECTIVES

To determine if a relationship exists between low contrast detail (LCD) detectability using the CDRAD 2.0 phantom, visual measures of image quality (IQ) and simulated lesion visibility (LV) when performing digital chest radiography (CXR).

METHODS

Using a range of acquisition parameters, a CDRAD 2.0 phantom was used to acquire a set of images with different levels of image quality. LCD detectability using the CDRAD 2.0 phantom, represented by an image quality figure inverse (IQF_inv) metric, was determined using the phantom analyser software. A Lungman chest phantom was loaded with two simulated lesions, of different sizes/placed in different locations, and was imaged using the same acquisition factors as the CDRAD 2.0 phantom. A relative visual grading analysis (VGA) was used by seven observers for IQ and LV evaluation of the Lungman images. Correlations between IQF_inv, IQ and LV were investigated.

RESULTS

Pearson's correlation demonstrated a strong positive correlation (r = 0.91; p < 0.001) between the IQ and the IQF_inv. Spearman's correlation showed a good positive correlation (r = 0.79; p < 0.001) and (r = 0.68; p < 0.001) between the IQF_inv and the LV for the first lesion (left upper lobe) and the second lesion (right middle lobe), respectively.

CONCLUSIONS

From results presented in this study, the automated evaluation of LCD detectability using CDRAD 2.0 phantom is likely to be a suitable option for IQ and LV evaluation in digital CXR optimisation studies. Advances in knowledge: This research establishes the potential of the CDRAD 2.0 phantom in digital CXR optimisation studies.

Image quality assessment with dose reduction using high kVp and additional filtration for abdominal digital radiography

PURPOSE

Dose reduction using additional filters with high kilovoltage peak (kVp) for abdominal digital radiography has received much attention recently. We evaluated image quality with dose reduction in abdominal digital radiography by using high kVp and additional copper filters at a tertiary hospital.

METHODS

Between June 2016 and July 2016, 82 patients underwent abdominal digital radiography using 80 kVp in X-ray room 1 and 82 were imaged using 92 kVp with 0.1-mm copper filtration in X-ray room 2. The effective dose was calculated using a PC-based Monte Carlo program. Image quality of the abdominal radiography acquired in the two rooms was evaluated using a five-point ordinal scale, as well as the signal-to-noise and contrast-to-noise ratios.

RESULTS

The mean effective dose decreased by 25.8% and 25.7% for the supine and standing positions, respectively, when abdominal digital radiography using 92 kVp with 0.1-mm copper filtration was performed. In the 20 patients who performed abdominal digital radiography twice in each room, visual grading scores for visualisation of psoas outlines and kidney outlines are higher in room 1. However, there was no statistical significant difference of visual grading scores among the 124 patients who underwent only one abdominal radiography in the room 1 or 2 (P > 0.05).

CONCLUSIONS

Dose reduction for abdominal digital radiography can be achieved with comparable image quality by performing abdominal digital radiography using 92 kVp with 0.1-mm copper filtration, despite the higher AEC dose.

[Propose for the Benchmark Dose (BD) for the Optimization of Protection in Medical Exposure in General Radiography]

The goal of this research was to create the most appropriate index dose for the optimization of protection in medical exposure in general radiography in Kanagawa prefecture. We distributed questionnaires to 272 medical institutions in Kanagawa prefecture. The investigation period was from October 2015 to February 2016. Entrance surface dose (ESD) was used as the index dose. Investigated regions in general radiography were the adult chest, adult abdomen, and infant chest (anterior-posterior projections for all regions). The effective response rate was 35%. ESD was significantly lower with a flat panel detector (FPD) than with computed radiography (CR) in all regions (adult chest and abdomen: p<0.001; infant chest: p<0.05) [e.g., mean (±standard deviation) ESD in the adult chest was 0.16±0.06 mGy with FPD and 0.24±0.10 mGy with CR]. In the infant chest with CR, ESD was significantly higher using a grid (0.15±0.07 mGy) compared to not using a grid (0.10±0.05 mGy; p<0.05). Based on these results, we propose the benchmark dose of each medical equipment, such as adult chest: FPD, 0.2 mGy; CR, 0.3 mGy.

Excess Radiation to Newborns Hospitalized in the Intensive Care Unit

Newborns in intensive care units are generally subjected to a great number of X-rays procedures and to the risk of radiation-induced damage. This study evaluated a possible excess radiation by excess of radiographs, excess of dose per radiograph or under-collimation of the X-ray beam. The mean of X-rays per newborn was 12 (1-65) during a mean hospitalization of 29 d (1-226 d). The mean frequency was 0.8 X-ray exposures per newborn. About 13% of X-rays were performed without a well-defined clinical motivation. The mean entrance surface dose of 72 μGy was higher than in most of comparative studies. Under-collimation caused non-thoracic structures to appear frequently on chest radiographs. This study indicates a possible reduction in X-rays exposures by applying the justification principle for each X-ray procedure, recommends a multiprofessional work in the attempt to dose optimization, and shows need of correctly use of collimation system to avoid irradiation of non-thoracic structures.

DOSE EVALUATION FOR DIGITAL X-RAY IMAGING OF PREMATURE NEONATES

X-ray radiography is a commonly used diagnostic method for premature neonates. However, because of higher radiosensitivity and young age, premature neonates are more sensitive to the detrimental effects of ionising radiation. Therefore, it is important to monitor and optimise radiation doses at the neonatal intensive care unit (NICU). The number of x-ray examinations, dose-area product (DAP) and effective doses are evaluated for three Dutch NICUs using digital flat panel detectors. Thorax, thorax-abdomen and abdomen protocols are included in this study. Median number of examinations is equal to 1 for all three hospitals. Median DAP ranges between 0.05 and 1.02 μGy m2 for different examination types and different weight categories. These examinations result in mean effective doses between 4 ± 4 and 30 ± 10 μSv per examination. Substantial differences in protocols and doses can be observed between hospitals. This emphasises the need for up-to-date reference levels formulated specifically for premature neonates.

Quantitative assessment of Pulmonary Alveolar Proteinosis (PAP) with ultra-dose CT and correlation with Pulmonary Function Tests (PFTs)

Background

The purpose of this study was to investigate whether ultra-low-dose chest computed tomography (CT) can be used for visual assessment of CT features in patients with pulmonary alveolar proteinosis (PAP) and to evaluate the relationship between the quantitative analysis of the ultra-low-dose CT scans and the pulmonary function tests (PFTs).

Methods

Thirty-eight patients (mean [SD] age, 44.47 [12.28] years; 29 males, 9 females) with PAP were enrolled and subjected to two scans each with low-dose CT (reference parameters: 120 kV and 50 mAs) and ultra-low-dose CT (reference parameters, 80 kV, 25 mAs). Images were reconstructed via filtered back projection (FBP) for low-dose CT and iterative reconstruction (IR) for ultra-low-dose CT. All patients underwent PFT. The Visual analysis for ground glass opacity (GGO) is performed. The quantitative CT and PFT results were analyzed by canonical correlations.

Results

The mean body mass index (BMI) was 25.37±3.26 kg/m². The effective radiation doses were 2.30±0.46 and 0.24±0.05 mSv for low-dose and ultra-low-dose CT, respectively. The size-specific dose estimates were 5.81±0.81 and 0.62±0.09 mSv for low-dose and ultra-low-dose CT. GGOs and interlobular septal thickening were observed bilaterally in all patients. The average visual GGO score was lower in the upper field (2.67±1.24) but higher in the middle and lower fields (3.08±1.32 and 3.08±0.97, respectively). The average score for the whole lung was 2.94±1.19. There is a significant correlation between PFTs and quantitative of ultra-low-dose CT (canonical loading = 0.78).

Conclusions

Ultra-low-dose CT has the potential to quantify the lung parenchyma changes of PAP. This technique could provide a sensitive and objective assessment of PAP and has good relation with PFTs. In addition, the radiation dose of ultra-low-dose CT was very low.

Image acquisition in general radiography: The utilisation of DDR

OBJECTIVE

This article explores image acquisition with DDR. General radiographic technology continues to advance therefore it remains paramount to continually reflect on DDR hardware and software amongst radiographers in an imaging modality that constitutes approximately 90% of all radiological examinations.

METHOD

This article reports findings from a wider ethnographic study of two general radiography environments in the United Kingdom (UK). Participant observation and semi-structured interviews were the methods used to uncover original data.

RESULTS

Two key themes are discussed. Firstly, 'the extent of DDR knowledge' amongst radiographers is examined. The findings uncover that not all radiographers have an adequate knowledge base with DDR technology. Secondly, 'pitfalls and near misses with DDR' is discussed. This theme highlights the potential danger of radiographers 'over-repeating' X-ray examinations, coincided with the occurrence of radiological incidents whereby a patient is exposed to ionising radiation with no added benefit.

CONCLUSION

This paper concludes by challenging the current 'skill base' to operate DDR equipment. In addition, new pitfalls and near misses are highlighted, which may help forestall radiation incidents in the future. Dose and image optimisation remain central tenets to the role of the radiographer.

ADVANCES IN KNOWLEDGE

Few studies have challenged image acquisition with DDR. This study adds to existing knowledge by uncovering original phenomena that may initiate discussions within the radiography community and continually enhance healthcare delivery.

Organ Doses From Diagnostic Medical Radiography-Trends Over Eight Decades (1930 to 2010)

This study provides a retrospective assessment of doses to 13 organs for the most common radiographic examinations conducted between the 1930s and 2010, taking into account typical technical parameters used for radiography during those years. This study is intended to be a resource on changes in medical diagnostic radiation exposure over time with a specific purpose of supporting retrospective epidemiological studies of radiation health risks. The authors derived organ doses to the brain, esophagus, thyroid, red bone marrow, lungs, breast, heart, stomach, liver, colon, urinary bladder, ovaries, and testes based on 14 common radiographic procedures and compared, when possible, with doses reported in the literature. These dose estimates were based on radiographic exposure parameters described in textbooks widely used by radiologic technologists in training from 1939 to 2010. The derived estimated doses presented here are believed to be representative of typical organs for an average-size adult who might be considered to be similar to the reference person. There were large variations in organ doses noted among the different types of radiographic examinations. Doses were highest in organs within the area imaged and next highest in organs in close proximity to the area imaged. Estimated organ doses have declined substantially [overall 22-fold (±38)] over time as a consequence of changes in technology, imaging protocols and protective measures. For some examinations, only slight differences were observed in doses for the decades of the 1960s, 1970s, and 1980s due to minor changes in technical parameters. Substantial dose reductions were observed in the 1990s and 2000s.

The impact of greyscale inversion for nodule detection in an anthropomorphic chest phantom: a free-response observer study

Objective:

The aim of this work was to assess the impact of greyscale inversion on nodule detection on posteroanterior chest X-ray images. Previous work has attempted this, with no consensus opinion formed. We assessed the value of “fast-flicking” between standard and inverted display modes for nodule detection.

Methods:

Six consultant radiologists (with 5–32 years' reporting experience) completed an observer task under the free-response paradigm. An anthropomorphic chest phantom was loaded with 50 different configurations of simulated nodules (1–4 nodules per case) measuring 5, 8, 10 and 12 mm in spherical diameter; each configuration represented a single case. In addition, 25 cases contained no nodules. Images were displayed in three modes: (i) standard, (ii) inverted and (iii) fast-flicking between standard and inverted display modes. Each observer completed the study in a different order of display (i, ii, iii) using a calibrated 5-megapixel monitor. Nodules were localized with mouse clicks and ratings assigned using a 1–10 discrete slider-bar confidence scale. Rjafroc (Pittsburgh, PA) was used for data analysis; differences in nodule detection performance were considered significant at 0.05.

Results:

The observer-averaged weighted jackknife alternative free-response receiver-operating characteristic figures of merit were 0.715 (standard), 0.684 (inverted) and 0.717 (fast-flicking). Random-reader fixed-case analysis revealed no statistically significant difference between any treatment pair [F(2,8) = 1.22; p = 0.345].

Conclusion:

No statistically significant difference in nodule detection was found for the three display conditions.

Advances in knowledge:

We have investigated the impact of fast-flicking between standard and inverted display modes for the detection of nodules. We found no benefit.

Optimized imaging of the midface and orbits

A variety of imaging techniques are available for imaging the midface and orbits. This review article describes the different imaging techniques based on the recent literature and discusses their impact on clinical routine imaging. Imaging protocols are presented for different diseases and the different imaging modalities.

[Examination for Effectiveness of Scatter Correction in Portable Chest Radiography]

OBJECTIVES

The aim of this study was to evaluate the effectiveness of scatter correction in the portable chest radiography.

METHODS

Digital radiographies were performed without anti-scatter grid (grid), with the scatter correction and with the grid ratio of 3 : 1 in this study. The scatter fraction and the detectability of low contrast signals were measured using the four acrylic phantoms of different thicknesses. The chest phantom radiographs were assessed subjectively, in random order, by six radiologic technologists.

RESULTS

The scatter fraction was higher in the no-grid technique, and was lower for the grid technique. The detectability of low contrast signals did not significantly differ between the scatter correction and the grid technique (p>0.05). The area under the receiver operating characteristic curve for the grid technique was higher than that for the scatter correction technique (0.888 vs. 0.855), although no significant difference was found between the grid and the scatter correction technique (p> 0.05). The ability to detect the nasogastric tube was significantly better in the grid technique (p<0.001).

DISCUSSION

In the scatter correction technique, the ability of scatter removal increased as the scatter fraction increased. The scatter correction technique was unnecessary to extremely accurate alignment. In addition, patient dose can be reduced by the scatter correction technique.

CONCLUSIONS

It seemed to be effective for the scatter correction in the portable chest radiography.

Assessment of patient dose and optimization levels in chest and abdomen CR examinations at referral hospitals in Tanzania

The aim of this study was to evaluate the radiation doses to patient during chest and abdomen CR examinations, and assess the related level of optimization at five referral hospitals in Tanzania. The international code of practice for dosimetry in diagnostic radiology was applied to determine the entrance surface air kerma (ESAK) to patients. The level of optimization was assessed from low‐contrast objects scores of phantom images at different exposures. The results show that mean ESAK varied from 0.16 to 0.37 mGy for chest PA and from 2 to 6 mGy for abdomen AP. Assuming similar patient and phantom attenuations, the optimization performed at all facilities was consistent with phantom evaluations in terms of tube potential settings in use. However, all facilities seemed to operate at higher tube load values above 5 mAs for chest examination, which can lead to unnecessary patient doses. Inadequate initial training on CR technology explains in large proportion the inappropriate use of exposure parameters.

PACS numbers: 87.50.up, 87.59bd

Impact of a training course on the quality of chest radiography to diagnose pulmonary tuberculosis

SETTING

Socio-economically underprivileged urban areas in the Philippines.

OBJECTIVE

To assess the performance of radiological technicians (RTs) 3 years after their participation in a training course to improve the quality of chest X-ray (CXR) and to test a monitoring visit after the course.

DESIGN

A cross-sectional and observational study including on-site monitoring of X-ray facilities in Manila and Quezon City and assessment of CXR films taken by 23 RTs who previously attended a training course in 2009 or 2010. The sum of the assessment scores for each of six assessment factors at four points, i.e., before and after the training course that had been previously analysed, and before and after the monitoring visits that were currently analysed, were compared.

RESULTS

Two assessment sum scores, identification mark or patient positioning, did not show significant differences. However, assessment of density, contrast, sharpness and artefact significantly improved after the training course, and before and after the monitoring visit, compared with before the training. There were no significant differences in any of the assessment factors before and after the monitoring visits.

CONCLUSION

The training course appears to have had a long-term effect on maintaining CXR quality. The post-training monitoring visit did not significantly improve CXR quality.

Radiation exposure in total ankle replacement

BACKGROUND

Radiation exposure from diagnostic imaging procedures is associated with increased cancer risk. No published data currently exist regarding ionizing radiation exposure in total ankle replacement surgery. This study quantified intraoperative fluoroscopic dose and duration during ankle replacement surgery and examined patient and technical factors affecting the level of exposure.

METHODS

Fifty-five patients underwent ankle replacement using STAR, Salto-Talaris, or INBONE total ankles. Intraoperative fluoroscopic dose and duration, patient demographics, implant design, and accompanying additional procedures were documented for each case. The relationship between each relevant variable and radiation dose and time was determined.

RESULTS

The mean fluoroscopic dose and duration for all cases were 1.15 ± 0.84 milliGray per case and 77 ± 34 seconds per case, respectively. There was a positive correlation between the absorbed radiation dose and the duration of fluoroscopy (r = .50, P < .001). The mean fluoroscopic doses were 1.53 milliGray, 0.99 milliGray, and 0.88 milliGray for INBONE, STAR, and Salto-Talaris prostheses, respectively. Fluoroscopic dose was significantly influenced by implant design (P = .035), with implants using an intramedullary referencing guide associated with higher radiation doses. After excluding cases requiring additional procedures, the fluoroscopic time and radiation dose associated with intramedullary referencing guide implants continued to exceed those of the other implants, but the differences were no longer statistically significant (P = .22, P = .09, respectively).

CONCLUSION

The average patient radiation dose during total ankle replacement was approximately one-fifth the recommended maximum yearly radiation exposure. The radiation dose was positively associated with fluoroscopy duration. Among factors controllable by the surgeon, selection of an implant with an extramedullary alignment system and conscious effort to minimize duration of fluoroscopy can reduce harmful radiation exposure and decrease cancer risk in total ankle replacement patients and associated operating room personnel.

LEVEL OF EVIDENCE

Level III, comparative series.

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.

[Dose reduction and adequate image quality in digital radiography: a contradiction?]

CLINICAL/METHODICAL ISSUE

Dose reduction and adequate image quality in digital radiography - a contradiction?

STANDARD RADIOLOGICAL METHODS

Digital radiography has already replaced traditional screen-film systems.

METHODICAL INNOVATIONS

Substantial improvements in both dose efficiency and spatial resolution demonstrate the rapid developments in digital radiography.

PERFORMANCE

Needle-detector systems have shown up to a 50% dose reduction compared to traditional screen-film systems. There is also a dose reduction capability of up to 50% comparing direct radiography (DR) systems to computed radiography (CR) systems for chest X-rays. However, despite the most recent achievements of CR technology, the dose efficiency of DR systems (caesium iodide flat-panel detector) is unparalleled.

ACHIEVEMENTS

The progress in detector technology has contributed to dose reduction and improved image quality, while saving time and providing a higher examination rate.

PRACTICAL RECOMMENDATIONS

The use of dose indicators and longitudinal dose control are important to avoid substantial accidental dose increase. The dose applied to patients should fall markedly below the defined diagnostic reference levels within the European Union. Regular quality control, as well as continuous education and training of medical and technical personnel, contribute to ensure that the ALARA (as low as reasonably achievable) principle is consistently followed.

Optimizing imaging quality and radiation dose by the age-dependent setting of tube voltage in pediatric chest digital radiography

Objective

The quality and radiation dose of different tube voltage sets for chest digital radiography (DR) were compared in a series of pediatric age groups.

Materials and Methods

Forty-five hundred children aged 0-14 years (yr) were randomly divided into four groups according to the tube voltage protocols for chest DR: lower kilovoltage potential (kVp) (A), intermediate kVp (B), and higher kVp (C) groups, and the fixed high kVp group (controls). The results were analyzed among five different age groups (0-1 yr, 1-3 yr, 3-7 yr, 7-11 yr and 11-14 yr). The dose area product (DAP) and visual grading analysis score (VGAS) were determined and compared by using one-way analysis of variance.

Results

The mean DAP of protocol C was significantly lower as compared with protocols A, B and controls (p < 0.05). DAP was higher in protocol A than the controls (p <0.001), but it was not statistically significantly different between B and the controls (p = 0.976). Mean VGAS was lower in the controls than all three protocols (p < 0.001 for all). Mean VGAS did not differ between protocols A and B (p = 0.334), but was lower in protocol C than A (p = 0.008) and B (p = 0.049).

Conclusion

Protocol C (higher kVp) may help optimize the trade-off between radiation dose and image quality, and it may be acceptable for use in a pediatric age group from these results.

Computed tomography of the chest with model-based iterative reconstruction using a radiation exposure similar to chest X-ray examination: preliminary observations

OBJECTIVES

The purpose of this study was to assess the diagnostic image quality of ultra-low-dose chest computed tomography (ULD-CT) obtained with a radiation dose comparable to chest radiography and reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) in comparison with standard dose diagnostic CT (SDD-CT) or low-dose diagnostic CT (LDD-CT) reconstructed with FBP alone.

METHODS

Unenhanced chest CT images of 42 patients acquired with ULD-CT were compared with images obtained with SDD-CT or LDD-CT in the same examination. Noise measurements and image quality, based on conspicuity of chest lesions on all CT data sets were assessed on a five-point scale.

RESULTS

The radiation dose of ULD-CT was 0.16 ± 0.006 mSv compared with 11.2 ± 2.7 mSv for SDD-CT (P < 0.0001) and 2.7 ± 0.9 mSv for LDD-CT. Image quality of ULD-CT increased significantly when using MBIR compared with FBP or ASIR (P < 0.001). ULD-CT reconstructed with MBIR enabled to detect as many non-calcified pulmonary nodules as seen on SDD-CT or LDD-CT. However, image quality of ULD-CT was clearly inferior for characterisation of ground glass opacities or emphysema.

CONCLUSION

Model-based iterative reconstruction allows detection of pulmonary nodules with ULD-CT with radiation exposure in the range of a posterior to anterior (PA) and lateral chest X-ray.

Utility of digital radiography for the screening of pneumoconiosis as compared to analog radiography: radiation dose, image quality, and pneumoconiosis classification

The purpose of this study was to compare digital radiography (DR) and analog radiography (AR) for the screening of pneumoconiosis with respect to radiation dose, image quality, and pneumoconiosis classification. DR was performed on 50 subjects who were enrolled for an examination of pneumoconiosis (Digital Diagnost™, Philips, Netherlands), and AR (MXO-15B, Toshiba, Japan) was performed the same day after the study was approved by the Institutional Review Board and written informed consent was obtained from all subjects. Entrance surface doses (ESDs) of DR and AR were measured using a glass dosimeter attached to a Rando human phantom (Alderson Co., U.S.) under exposure conditions commonly used in clinical practice in Korea. Visibilities on all images were evaluated using a 5-point scale by four chest radiologists using a modified form of the European Chest Guidelines (EUR 16260). All the images were classified using the ILO's guidelines by referencing standard analog radiographs. ESDs of DR were significantly lower than those of AR (0.15 mGy vs. 0.21 mGy, p < 0.05). All anatomic structures were significantly more visible by DR images (p < 0.0001), especially the left main bronchus, ribs, and thoracic spine. Body mass index did not correlate with anatomic structure visibility by DR (r = -0.029, p = 0.842) or AR images (r = -0.076, p = 0.602). Overall intra- and inter-reader agreements for DR images were significantly higher than for AR images. DR offers improved image quality with a significant reduction of up to 23.6% in radiation dose and more accurate pneumoconiosis classification than AR.

Assessment of patient doses in CR examinations throughout a large health region

Optimization and standardization of radiographic procedures in a health region minimizes patient exposure while producing diagnostic images. This report highlights the dose variation in common computed radiography (CR) examinations throughout a large health region. The RadChex cassette was used to measure the radiation exposure at the table or wall bucky in 20 CR rooms, in seven hospitals, using CR technology from two vendors. Exposures were made to simulate patient exposure (21 cm polymethyl methacrylate) under standard conditions for each bucky: 81 kVp at 100 cm for anteroposterior abdomen table bucky exposures (180 cm for posteroanterior chest wall bucky exposures), using the left, the right, or the center automatic exposure control (AEC) cells. Protocol settings were recorded. An average of 37% variation was found between AEC chambers, with a range between 4% and 137%. A 60% difference in dose was discovered between manufacturers, which was the result of the manufacture's image processing algorithm and subsequently corrected via software updates. Finally, standardizing AEC cell selection during common chest examinations could reduce patient dose by up to 30%. In a large health region, variation in exam protocols can occur, leading to unnecessary patient dose from the same type of examination. Quality control programs must monitor exam protocols and AEC chamber calibration in CR to ensure consistent, minimal, patient dose, regardless of hospital or CR vendor. Furthermore, this report highlights the need for communication between radiologists, technologists, medical physicist, service engineers, and manufacturers required to optimize CR protocols.

[Physical image properties of digital radiography systems in low dose range]

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.

Tomosynthesis in pulmonary cystic fibrosis with comparison to radiography and computed tomography: a pictorial review

The purpose of this pictorial review is to illustrate chest imaging findings of cystic fibrosis (CF) using tomosynthesis (digital tomography), in comparison to radiography and computed tomography (CT). CF is a chronic systemic disease where imaging has long been used for monitoring chest status. CT exposes the patient to a substantially higher radiation dose than radiography, rendering it unsuitable for the often needed repeated examinations of these patients. Tomosynthesis has recently appeared as an interesting low dose alternative to CT, with an effective dose of approximately 0.08 mSv for children and 0.12 mSv for adults. Tomosynthesis is performed on the same X-ray system as radiography, adding only about 1 min to the normal examination time. Typical pulmonary changes in CF such as mucus plugging, bronchial wall thickening, and bronchiectases are shown in significantly better detail with tomosynthesis than with traditional radiography. In addition, the cost for a tomosynthesis examination is low compared to CT. To reduce the radiation burden of patients with CF it is important to consider low dose alternatives to CT, especially in the paediatric population. Tomosynthesis has a lower radiation dose than CT and gives a superior visualisation of pulmonary CF changes compared to radiography. It is important to further determine the role of tomosynthesis for monitoring disease progression in CF.

Correlation of contrast-detail analysis and clinical image quality assessment in chest radiography with a human cadaver study

PURPOSE

To determine the correlation between the clinical and physical image quality of chest images by using cadavers embalmed with the Thiel technique and a contrast-detail phantom.

MATERIALS AND METHODS

The use of human cadavers fulfilled the requirements of the institutional ethics committee. Clinical image quality was assessed by using three human cadavers embalmed with the Thiel technique, which results in excellent preservation of the flexibility and plasticity of organs and tissues. As a result, lungs can be inflated during image acquisition to simulate the pulmonary anatomy seen on a chest radiograph. Both contrast-detail phantom images and chest images of the Thiel-embalmed bodies were acquired with an amorphous silicon flat-panel detector. Tube voltage (70, 81, 90, 100, 113, 125 kVp), copper filtration (0.1, 0.2, 0.3 mm Cu), and exposure settings (200, 280, 400, 560, 800 speed class) were altered to simulate different quality levels. Four experienced radiologists assessed the image quality by using a visual grading analysis (VGA) technique based on European Quality Criteria for Chest Radiology. The phantom images were scored manually and automatically with use of dedicated software, both resulting in an inverse image quality figure (IQF). Spearman rank correlations between inverse IQFs and VGA scores were calculated.

RESULTS

A statistically significant correlation (r = 0.80, P < .01) was observed between the VGA scores and the manually obtained inverse IQFs. Comparison of the VGA scores and the automated evaluated phantom images showed an even better correlation (r = 0.92, P < .001).

CONCLUSION

The results support the value of contrast-detail phantom analysis for evaluating clinical image quality in chest radiography.

Development of standard digital images for pneumoconiosis

We developed the standard digital images (SDIs) to be used in the classification and recognition of pneumoconiosis. From July 3, 2006 through August 31, 2007, 531 retired male workers exposed to inorganic dust were examined by digital (DR) and analog radiography (AR) on the same day, after being approved by our institutional review board and obtaining informed consent from all participants. All images were twice classified according to the International Labour Office (ILO) 2000 guidelines with reference to ILO standard analog radiographs (SARs) by four chest radiologists. After consensus reading on 349 digital images matched with the first selected analog images, 120 digital images were selected as the SDIs that considered the distribution of pneumoconiosis findings. Images with profusion category 0/1, 1, 2, and 3 were 12, 50, 40, and 15, respectively, and a large opacity were in 43 images (A = 20, B = 22, C = 1). Among pleural abnormality, costophrenic angle obliteration, pleural plaque and thickening were in 11 (9.2%), 31 (25.8%), and 9 (7.5%) images, respectively. Twenty-one of 29 symbols were present except cp, ef, ho, id, me, pa, ra, and rp. A set of 120 SDIs had more various pneumoconiosis findings than ILO SARs that were developed from adequate methods. It can be used as digital reference images for the recognition and classification of pneumoconiosis.

Copper filtration in pediatric digital X-ray imaging: its impact on image quality and dose

The effect of copper (Cu) filtration on image quality and dose in different digital X-ray systems was investigated. Two computed radiography systems and one digital radiography detector were used. Three different polymethylmethacrylate blocks simulated the pediatric body. The effect of Cu filters of 0.1, 0.2, and 0.3 mm thickness on the entrance surface dose (ESD) and the corresponding effective doses (EDs) were measured at tube voltages of 60, 66, and 73 kV. Image quality was evaluated in a contrast-detail phantom with an automated analyzer software. Cu filters of 0.1, 0.2, and 0.3 mm thickness decreased the ESD by 25-32%, 32-39%, and 40-44%, respectively, the ranges depending on the respective tube voltages. There was no consistent decline in image quality due to increasing Cu filtration. The estimated ED of anterior-posterior (AP) chest projections was reduced by up to 23%. No relevant reduction in the ED was noted in AP radiographs of the abdomen and pelvis or in posterior-anterior radiographs of the chest. Cu filtration reduces the ESD, but generally does not reduce the effective dose. Cu filters can help protect radiosensitive superficial organs, such as the mammary glands in AP chest projections.

Detection of chest trauma with whole-body low-dose linear slit digital radiography: a multireader study

OBJECTIVE

The objective of our study was to compare the performance of low-dose linear slit digital radiography (DR) with computed radiography (CR) for the detection of trauma sequelae in the chest including rib fractures, pneumothorax, and lung contusion.

MATERIALS AND METHODS

Eighty trauma victims (62 males, 18 females; mean age, 51.5 years) with a total of 612 rib fractures and 80 consecutive patients without rib fractures (59 males, 21 females; mean age, 39.5 years) were retrospectively analyzed. All patients had undergone whole-body linear slit DR and consecutive chest CT, and 87 patients underwent follow-up CR of the chest within 24 hours of DR and CT. Four blinded readers assessed image quality, rib fracture localization with diagnostic confidence, and the presence of pneumothorax and lung contusion on linear slit DR and CR images. Sensitivity for rib fractures and image quality were compared using the Wilcoxon's test. For the detection of pneumothorax and lung contusion, the difference in the areas under the receiver operating characteristic curves were calculated.

RESULTS

The rate of correctly identified rib fractures was higher (true-positive findings per image, 2.55 vs 2.21, respectively; p = 0.02), the rate of missed fractures was lower (false-negative findings per image, 4.98 vs 6.19; p = 0.02), and the diagnostic confidence was greater (2.03 vs 1.73 on a 3-point scale; p = 0.01) with linear slit DR than with CR, respectively. Image quality and performance for detecting pneumothorax and lung contusion with both techniques were not statistically different (p = 0.22, 0.85, and 0.55, respectively).

CONCLUSION

Linear slit DR is a reliable substitute for CR in the initial evaluation of chest trauma, with better sensitivity for detecting rib fractures and similar performance in assessing pneumothorax and lung contusion.