Flat-panel Detector System Research Articles

Data analysis of average glandular dose in mammography toward revision of the diagnostic reference level of Japan.

Diagnostic reference level (DRL) for mammography for 2015 and 2020 has been published by J-RIME. More new dose studies are needed to revise the next DRL. In preparation for the next revision of the DRL for mammography, this study investigated data from the Japan Central Organization on Quality Assurance of Breast Cancer Screening on the mean average glandular dose (AGD) for institutional image accreditation in 2019-2023 and the relationship between the average at eligible institutions to date and the type of breast X-ray system. The 95th percentile values of the AGD distributions for the Computed Radiography (CR) and Flat Panel Detector (FPD) systems were 2.5mGy and 2.0mGy, respectively. Moreover, it is assumed that AGD is decreasing due to the spread of FPD systems, and it is expected that the further spread of FPD systems and systems with W/Rh target/filter will reduce AGD in future.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

Dose Reduction in Medical Radiography: Advancing Veterinary Diagnostic Solutions

In this study, we investigated photon attenuation using an anti-scatter lead grid with a flat panel detector (FPD) and aimed to mitigate it by implementing a linear array detector (LAD). We developed a mechanical system that facilitates X-ray scans using the LAD. For comparison, we selected a standard FPD unit. To assess the differences in entrance skin dose (ESD) between the LAD and FPD systems, we initially utilized anthropomorphic phantoms, followed by water phantoms for exposure tests. Results showed that at a water depth of 10 cm, the ESD from the LAD was 22% lower than that from the FPD. At 30 cm this ratio was increased up to 40%. As water thickness increased, the benefits of using LAD became more evident, demonstrated by a lower ESD. This finding highlights the potential utility of implementing this equipment in veterinary radiography, particularly for imaging animals and their anatomical sites with thicker tissues.

The fabrication and characterization of direct conversion flat panel X-ray imager with TlBr film

The novel direct conversion flat panel detectors (FPDs) utilizing thallium bromide (TlBr) films are developed and characterized in this study. Thin TlBr films, deposited using an evaporation technique, achieved thicknesses of 10 μm and 50 μm. A pixel sensor array, with a pixel size of 235 × 235 μm2 and a sensitive area of 29.61 × 39.48 mm2, was developed using low-temperature polysilicon thin-film transistor (LTPS TFT) technology as the initial study to explore performance characteristics of developed imaging system. The TlBr film was characterized based on the current-voltage (I–V) profile, showing a resistivity of 2.78 × 1010 Ω·cm. The LTPS TFT showed a leakage current of about 10−13 A, while the noise of TlBr FPD system was around 104 e− rms, primarily limited by the readout system. The detector system was characterized using radiation from an X-ray tube with a voltage in the range of 30 kV–100 kV and a current of 2 mA, involving an X-ray test chart as the object with the processing time of 18.15–18.30 ms per frame. Based on the contrast and contrast-to-noise ratio (CNR) values, the 10 μm and 50 μm TlBr FPD clearly captured the image in operation between 30 kV and 100 kV. The 50 μm TlBr FPD demonstrated improved sensitivity, showing pixel values with 10 times higher intensity and enhanced line pair detail at 30 kV X-ray operation. The 10 μm TlBr achieved spatial resolution of 267 μm full width at half maximum (FWHM), while the 50 μm TlBr achieved 250 μm FWHM. In the X-ray imaging demonstration, the shape and structure of anchovy was clearly distinguished. The TlBr film FPD presents promising potential for a room temperature X-ray imager.

Photon counting-energy integrating hybrid flat panel detector systems for image-guided interventions: an experimental proof-of-concept

Objective. Current C-arm x-ray systems equipped with scintillator-based flat panel detectors (FPDs) lack sufficient low-contrast detectability and spectral, high-resolution capabilities much desired for certain interventional procedures. Semiconductor-based direct-conversion photon counting detectors (PCDs) offer these imaging capabilities, although the cost of full field-of-view (FOV) PCD is still too high at the moment. The purpose of this work was to present a hybrid photon counting-energy integrating FPD design as a cost-effective solution to high-quality interventional imaging. Approach. In the proposed hybrid detector design, the central scintillator and thin-film transistor elements in the FPD are replaced with a semiconductor PCD module to upgrade the imaging capabilities of the C-arm system while preserving the full FOV coverage. The central PCD module can be used for high-quality 2D and 3D region-of-interest imaging with improved spatial- and temporal-resolution as well as spectral resolving capability. An experimental proof-of-concept was conducted using a 30 × 2.5 cm2 CdTe PCD and a 40 × 30 cm2 CsI(Tl)-aSi(H) FPD. Main results. Phantom and in vivo animal studies show (1) improved visualization of small stent wires in both 2D and 3D images due to the better spatial resolution of the PCD; (2) dual-energy angiography imaging capability by using the spectral PCD; (3) better conspicuity of small peripheral iodinated vessels (contrast-to-noise ratio improvement range: (29%, 151%)); (4) the central PCD outputs can be fused seamlessly with the surrounding scintillator detector outputs to provide full field imaging: A post-processing chain was developed by leveraging the PCD’s spectral information to match the image contrast of the PCD images to the surrounding scintillator detector, followed by spatial filtering of the PCD image to match noise texture and spatial resolution. Significance. The hybrid FPD design provides a cost-effective option to upgrade C-arm systems with spectral and ultra-high resolution capabilities without interfering with the clinical need for full FOV imaging.

Projected lung area using dynamic X-ray (DXR) with a flat-panel detector system and automated tracking in patients with chronic obstructive pulmonary disease (COPD)

ObjectivesTo assess the association of projected lung area (PLA) measured by DXR with demographic data, pulmonary function, and COPD severity, and to generate PLA over time curves using automated tracking. MethodsThis retrospective study recruited healthy volunteers and COPD patients. Participants were classified into three groups: normal, COPD mild and COPD severe. PLA was calculated from the manually traced bilateral lung contours. PLA over time curves were produced using automated tracking, which was used to calculate slope and intercept by approximate line during forced expiration. The correlation of PLA, difference of PLA between end-inspiration and end-expiration (ΔPLA), slope, and intercept with demographic data and pulmonary function tests were investigated. The difference of PLA, ΔPLA, intercept, and slope among three groups were also evaluated. ResultsThis study enrolled 45 healthy volunteers and 32 COPD patients. COPD severe group had larger PLA in both lungs at tidal/forced end-inspiration/expiration, smaller slope, and larger intercept than normal group (p < 0.001). PLA was correlated with % forced expiratory volume in one second (%FEV1) (rs from −0.42 to −0.31, p ≤ 0.01). ΔPLA in forced breathing showed moderate correlation with vital capacity (VC) (rs = 0.58, p < 0.001), while ΔPLA in tidal breathing showed moderate correlation with %FEV1 (rs = -0.52, p < 0.001) as well as mild correlation with tidal volume (rs = 0.24, p = 0.032). Intercept was slightly underestimated compared with manually contoured PLA (p < 0.001). ConclusionCOPD patients had larger PLA than healthy volunteers. PLA and ΔPLA in tidal breathing showed mild to moderate correlation with %FEV1.

Evaluation of Radiation Dose Reduction and its Effect on Image Quality for Different Flat-Panel Detectors.

Purpose:To evaluate the image quality of semi-anatomical chest radiographs acquired using low radiation doses from seven different flat-panel detector (FPD) systems.Materials and Methods:Radiographs of a semi-anatomical chest phantom were acquired at 70 and 110 kVp using 7 different FPDs from 5 vendors. Radiation doses were measured using a dose-area-product (DAP) meter. To standardize measurements across all FPDs, DAP value of 51.05 μGym2 obtained at 70 kVp and 9.43 μGym2 at 110 kVp was used as reference in this study. Radiation doses were reduced by manually adjusting mAs for both tube potentials in all FPD systems to achieve acceptable image quality. Contrast-to-noise ratio, signal-to-noise ratio and figure of merit (FOM) in lung, heart, and diaphragm for all images were analyzed.Results:In comparison with set standard protocol, radiation dose reduction of 20%, 21%, 21.6%, 59.5%, 60.7%, 62.2%, and 67.6% with optimal image quality was observed in Prognosys Prorad, GE Definium 8000, Siemens Fusion, Fujifilm FGX, Fujifilm FGXR, Philips Digital Diagnost and Siemens Aristos at 70 kVp. At 110 kVp, dose reduction of 15.7% and 34.8% was possible only for Philips Digital Diagnost and Siemens Aristos. FOM was high at 110 kVp even when radiation doses were reduced by a factor 2 when compared to 70 kVp in all digital radiography systems.Conclusion:This study demonstrates the feasibility of using a semi-anatomical chest phantom in the optimization of radiation dose and image quality. The FOM was a good indicator in assessing image quality between different detectors.

A new stationary grid, with grid lines aligned to pixel lines with submicron‐order precision, to suppress grid artifacts

We have developed a new stationary grid named a pixel-aligned grid (PA grid), in which the grid lines are aligned to the pixel lines with submicron-order precision. Further, we have evaluated its performance relative to that of a conventional grid combined with grid-line removal (GLR) processing. A flat-panel detector system of an indirect type, with a pixel pitch of 150μm, was employed. Four PA grids having a grid ratio of 6:1 associated with abdominal bedside radiography, with the grid-line pitch (GP) varied around the target value of 150μm, were produced. Blank images were obtained with four PA grids for measuring the period and amplitude of the grid artifact. In performance evaluation, acrylic and anthropomorphic abdominal phantom images were used with the PA grid, a conventional grid (40 lines/cm, grid ratio 6:1), and no grids. The grid artifacts were evaluated by power spectrum (PS) analysis. Also, the signal-to-noise ratio (SNR) improvement factor (KSNR ) was measured. Grid artifacts were hardly recognizable with PA grids with GP errors of 0.3μm and 0.6μm because of the prolonged grid artifact periods. The measured artifact amplitudes of these PA grids were less than 0.6%. Furthermore, the PA grids did not produce notable frequency peaks in PS. In contrast, the conventional grid without GLR processing produced two conspicuous peaks. With GLR processing, notable reductions in PS were observed around the two peak frequencies, which caused blurring in bone structures. For the acrylic thickness of 20cm, the KSNR s for the PA grid were around 1.4, suggesting some SNR improvement in abdominal bedside radiography. The present study has demonstrated that PA grids with their grid-line pitches close to the pixel-line pitch within errors of 0.6μm produce grid artifact-free images without any signal losses. Thus, the proposed PA grid will prove to be effective and useful in various clinical applications.

Correlations between cardiovascular parameters and image parameters on dynamic chest radiographs in a porcine model under fluid loading.

Latest digital radiographic technology permits dynamic chest radiography during the cardiac beating and/or respiration, which allows for real-time observation of the lungs. This study aimed to assess the capacity of dynamic flat-panel detector (FPD) imaging without the use of contrast media to estimate cardiovascular parameters based on image parameters of a porcine model under fluid loading. Three domestic pigs were intubated, and mechanical ventilation was provided using a ventilator under anesthesia. A porcine model involving circulatory changes induced by fluid loading (fluid infusion/blood removal) was developed. Sequential chest radiographs of the pigs were obtained using a dynamic FPD system within the first 5 min after fluid loading. Image parameters such as the size of the heart shadow and mean pixel values in the lungs were measured, and correlations between fluid loading and cardiovascular parameters (blood pressure [BP], cardiac output [CO], central venous pressure [CVP], and pulmonary arterial pressure [PAP]) were analyzed based on freedom-adjusted coefficients of determination (Rf2). Fluid loading was correlated with radiographic lung density and the size of the heart shadow. Radiographic lung density was correlated with the left and right heart system-related parameters BP, CO, CVP, and PAP. The size of the heart shadow correlated with the left heart system-related parameters CO and BP. Dynamic FPD imaging allows for the relative evaluation of cardiovascular parameters based on image parameters. This diagnostic method provides radiographic image information and estimates relative circulatory parameters.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12194-021-00626-2.

Development of a 3D Printed Dynamic Phantom for Assessing Image Lag in Fluoroscopy

Evaluating the visibility of stationary and moving objects is a requirement in Flat Panel Detector (FPD) systems, especially with fluoroscopy. One undesired phenomenon with dynamic fluoroscopic images is the potential artifact caused by image lag in the detector. Image lag is a delay known to degrade image quality. Therefore, it is an important factor in dynamic fluoroscopy. However, it is not routinely checked. Commercial phantoms by NEMA and LEEDS offer the use of rotatable objects to assess lag.

Detection of Pulmonary Embolism Using a Novel Dynamic Flat-Panel Detector System in Monkeys.

Recently, dynamic chest radiography (DCR) was developed to evaluate pulmonary function using a flat-panel detector (FPD), which can evaluate blood flow in the pulmonary artery without injection of contrast agents. This study investigated the ability of a FPD to measure physiological changes in blood flow and to detect pulmonary embolism (PE) in monkeys.Methods and Results:DCR was performed in 5 monkeys using a FPD. Regions of interest (ROI) were placed in both lung fields of the image, and maximum changes in pixel value (∆pixel value) in the ROI were measured during 1 electrocardiogram cardiac cycle. Next, a PE model was induced using a Swan-Ganz catheter and additional images were taken. The ∆pixel value of the lungs in normal and PE models were compared in both supine and standing positions. The lung ∆pixel value followed the same cycle as the monkey electrocardiogram. ∆pixel values in the upper lung field decreased in the standing as compared to the supine position. In the PE model, the ∆pixel value decreased in the area of pulmonary blood flow occlusion and increased in the contralateral lung as compared to the normal model (normal model 1.287±0.385, PE model occluded side 0.428±0.128, PE model non-occluded side 1.900±0.431). A FPD could detect postural changes in pulmonary blood flow and its reduction caused by pulmonary artery occlusion in a monkey model.

A proposed combination of flat-panel detector and mobile X-ray systems for low-dose image-guided central venous catheter insertion

A central venous catheter (CVC) should be inserted at the optimum position to infuse medicines, blood products, nutrients, or fluids. Positioning of the catheter tip is commonly performed under landmark or fluoroscopic guidance. However, Japanese regulations do not allow the performing of fluoroscopy-guided procedures outside of the fluoroscopy room. We hypothesized that a new image-guided CVC placement technique by combining a wireless flat-panel detector (FPD) and a mobile X-ray system could be applied at the bedside to support CVC insertion. A CVC attached to a chest phantom in conjunction with the polymethyl methacrylate (PMMA) phantom was imaged, contrast-to-noise ratio (CNR) was measured with images, and radiologists and emergency physicians rated the catheter images using a Likert scale for visual evaluation. The minimum dose of the FPD and mobile X-ray system was reduced by at least 98% compared with that of the X-ray fluoroscopy system. The CNR decreased with the increasing PMMA phantom thickness. However, results of the visual evaluation were maintained at the clinically usable score with low-dose imaging up to a 6-cm thickness of the PMMA phantom. In conclusion, the combination of FPD and mobile X-ray systems is particularly effective in the emergency room setting where such procedures are required to be performed with urgency.

Comparison of dynamic flat-panel detector-based chest radiography with nuclear medicine ventilation-perfusion imaging for the evaluation of pulmonary function: A clinical validation study.

Dynamic chest radiography (DCR) is a flat-panel detector (FPD)-based functional lung imaging technique capable of measuring temporal changes in radiographic lung density due to ventilation and perfusion. The aim of this study was to determine the diagnostic performance of DCR in the evaluation of pulmonary function based on changes in radiographic lung density compared to nuclear medicine lung scans. This study included 53 patients with pulmonary disease who underwent DCR and nuclear medicine imaging at our institution. Dynamic chest radiography was conducted using a dynamic FPD system to obtain sequential chest radiographs during one breathing cycle. The maximum change in the average pixel value (Δmax ) was measured, and the percentage ofΔmax in each lung region, calculated relative to the sum of all lung regions (Δmax %), was calculated for each factor (ventilation and perfusion). The Δmax % was compared with the accumulation of radioactive agents (radioactive agents%) on ventilation and perfusion scans in each lung and lung region using correlation coefficients and scatter plots. The ratio of ventilation to perfusion Δmax % was calculated and compared with nuclear medicine ventilation-perfusion (V/Q) findings in terms of sensitivity and specificity for V/Q mismatch in each lung region. There was a high correlation between Δmax % and radioactive agents% for each lung (Ventilation: r=0.81, perfusion: r=0.87). However, correlation coefficients were lower (0.37 to 0.80) when comparing individual lung regions, with the upper lung regions showing the lowest correlation coefficients. The sensitivity and specificity of DCR for V/Q mismatch were 63.3% (19/30) and 60.1% (173/288), respectively. Motion artifacts occasionally increased Δmax %, resulting in false negatives. Ventilation and perfusion Δmax % correlated reasonably with radioactive agents% on ventilation and perfusion scans. Although the regional correlations were lower and the detection performance for V/Q mismatch was not enough for clinical use at the moment, these results suggest the potential for DCR to be used as a functional imaging modality that can be performed without the use of radioactive contrast agents. Further technical improvement is required for the implementation of DCR-based V/Q studies.

Proposed diagnostic reference levels for general radiography and mammography in Japan

Diagnostic reference levels (DRLs 2015) in Japan were first published in 2017, on the Japan Network for Research and Information on Medical Exposures network. Medical facilities in Japan are now presumably reconsidering radiation doses at their facilities and approaching protection optimisation through the application of DRLs 2015. However, since more than 3 years have elapsed since publication, radiation doses received by patients in Japan may have diverged from DRLs 2015. We therefore undertook the present study. Based on our questionnaire survey implemented in 2017, we estimated the entrance skin dose (ESD) under general radiography fields and the mean glandular dose (MGD) under mammography, to compile a report on the doses received by patients under general radiography fields and mammography, and to propose new DRLs as replacements for DRLs 2015. Radiation doses under general radiography fields and mammography were estimated from the results of the 2017 questionnaire survey and applied to determine new DRLs at 75% values of dose distributions in general radiography fields and at 95% values of dose distributions in mammography. Among all the modes for general radiography fields and mammography, median ESD and MGD were significantly smaller with flat panel detector systems than with computed radiography systems. Comparison of the results with DRLs 2015 values showed a trend toward decreases in all imaging methods of the general radiography fields and mammography ranging from 5.0% (child chest radiography) to 31.7% (skull radiography). Moreover, responses showed that DRLs 2015 were recognised and used for comparison at many facilities. We have described the doses received by patients in general radiography fields and mammography in 2017 and proposed new DRLs as replacements for DRLs 2015. The DRLs we proposed for general radiography fields and mammography were determined to be lower than DRLs 2015 for all modes.

Combination system in advanced image processing for improving image contrast and a conventional row-ratio grid for an indirect flat-panel detector system: An experimental study

Conventional grids with high grid ratios are not ideal for use in bedside radiography because of the difficulty in maintaining the required alignment. To address this issue, the potential usefulness of a combination system that employs removal processing software for scattered radiation and a conventional grid with a low grid ratio (3:1) for an indirect-conversion-type flat-panel detector system was evaluated by measuring image quality and observer performance. The hypothetical grid ratios for the software were 2:1, 3:1, 6:1, 8:1, and 10:1. The scatter fraction of the combination system was lower than that of the software alone. Significant improvement was observed in the effect of scattered radiation removal up to a hypothetical software grid ratio of 6:1. However, the Wiener spectrum increased (radiographic noise degraded) with an increase in the hypothetical grid ratio. The contrast ratios of the combination system were improved compared to those of the software alone for anthropomorphic chest radiographs. An observer test was also conducted using the contrast-detail phantom. The combination system indicated higher low-contrast detectability compared to the software alone, although there were no statistical differences between the hypothetical grid ratios of 6:1, 8:1, and 10:1 in all combinations of the software alone and the combination system. We concluded that a combination system with software that uses a hypothetical grid ratio of 6:1 or more and a 3:1 conventional grid would be more useful for reducing the scattered radiation component compared to the software alone with a hypothetical higher grid ratio for thicker objects.

Measurement Accuracy of CT Beam Width with a Portable Flat-panel Detector

X-ray film or computed radiography (CR) system has been employed in clinical setting, and these devices are gradually replaced by portable flat-panel detector (FPD) systems. They may be employed to measure the beam width instead of the traditional CR system. In this study, we estimated the accuracy of beam width measured by the portable FPD system. A CR cassette and FPD were placed at the isocenter, and the pixel values were measured in a single axial CT scanning at a tube potential of 80 kVp, tube currents of 10-40 mA (5 mA steps), and tube rotation time of 0.5 s. Then, the FPD was sandwiched between 0.5 mm copper plate and 2 mm lead plate to avoid the pixel saturation and artifact from the FPD electronic substrates. The beam widths were measured at selected nominal beam widths (40, 80, 120 and 160 mm) using a double exposure technique (tube currents of 10 and 20 mA). Log-linear relationships for two systems were obtained between the pixel value and radiation exposure for parameters less than or equal to 12.5 mAs. A test for the equivalence with confidence intervals showed that the measurement accuracy of the CR and FPD systems was equivalent. The portable FPD system could be utilized for the measurement of the CT beam width as well as CR system.

The Large Individual Differences in the Range of Hip Joint Motion Rather Than Lumbar Spine Motion Affect Dynamic Spinopelvic Rhythm.

Introduction Global spinal balance and its relationship to the pelvis have received much attention, and various formulae have been used to predict postoperative spinopelvic alignment for spinal surgery. However, previous studies had limitations because no consideration was given to the dynamic factor. Methods Fifteen healthy adults without any lumbar disorder (group A) and 9 L4-spondylolisthesis patients (Group B) volunteered to participate in the study. Sequential images were captured with the subjects in the standing position with maximal forward bending followed by backward bending using a dynamic flat panel detector system. Spinopelvic parameters (LL: lumbar lordosis, SA: sacrofemoral angle, SS: sacral slope, PI: pelvic incidence, DP: distance of the horizontal movement of the pelvis) were evaluated. We also investigated the relationship between LL and SA (lumbar/hip [L/H] ratio) as the spinopelvic rhythm. Results In group A, the mean change in LL was 83.2 ± 9.5°; change in SA, 45.4 ± 16.6°; SS, 42.6 ± 8.9°; PI, 43.2 ± 7.7°; DP, 15.7 ± 3.4 cm, and L/H ratio, 3.6 ± 2.7. However, spinopelvic rhythm changed over time, because the change in LL was larger than the change in SA from the middle of the rising motion to the upright position. In group B, the mean change in LL was 50.3 ± 8.0°; SA, 56.9 ± 16.0°; SS, 27.5 ± 13.5°; PI, 47.4 ± 10.4°; DP, 12.7 ± 6.8 cm; and L/H ratio, 1.0 ± 0.5. Conclusions When compared with the change in LL, individual differences were largely noted in the change in SA. These results demonstrated that the range of hip joint motion under physiological conditions, unlike anatomical motion, differed substantially between individuals. Therefore, spinopelvic rhythm is dependent on the change in SA.

Optimal beam quality for chest flat panel detector system: realistic phantom study.

To investigate optimal beam quality for chest flat panel detector (FPD) system by semi-quantitatively assessment using a realistic lung phantom. Chest FPD radiographs were obtained on a realistic lung phantom with simulated lung opacities using various X-ray tube voltage levels (90-140kV) with/without copper filter. Entrance skin dose was set to maintain identical for all images (0.1mGy). Three chest radiologists unaware of the exposure settings independently evaluated the image quality of each simulated opacity and normal structure using a 5-point scale (+ 2: clearly superior to the standard; + 1: slightly superior to the standard; 0: equal to the standard; - 1: slightly inferior to the standard; - 2: clearly inferior to the standard). The traditional FPD image obtained at a tube voltage of 120kV was used as the standard. The scores of image quality were statistically compared using the Wilcoxon rank test with Bonferroni correction. FPD images using 90-kV shot with copper filter were superior to the traditional 120-kV shot without filter with respect to the visibility of vertebra, pulmonary vessels, and nodules overlapping diaphragm and heart (p < 0.05). There was no significant difference with respect to the visibility of all other simulated lung opacities (lung nodules except for overlying diaphragm/heart and honeycomb opacity) between each tube voltage level with/without copper filter and the traditional 120-kV shot without filter. Image quality of FPD images using 90kV with copper filtration is superior to that using standard tube voltage when dose is identical. • FPD image quality using 90kV with filter is superior to that using traditional beam. • Ninety-kilovolt shot with copper filter may be suitable for chest FPD image. • Clinical study dealing with chest FPD beam optimization would be warranted.

Time-resolved quantitative evaluation of diaphragmatic motion during forced breathing in a health screening cohort in a standing position: Dynamic chest phrenicography

Objective: To assess diaphragmatic motion during forced breathing in a health screening center cohort by time-resolved quantitative analysis using dynamic chest radiography and demonstrate the characteristics and associations with demographics and pulmonary function of participants.Materials and methods: This prospective study includes 174 volunteers (99 males; median 57, range 36–93 years old) that underwent dynamic chest radiography with a flat panel detector system during forced breathing in a standing position. We automatically tracked and recorded the positions of the top of the diaphragms and the excursions on images of each participant and calculated peak motion speeds based on the data. We investigated the associations with demographics and pulmonary function statistically.Results: The average excursions of the diaphragms during forced breathing were 49.1 ± 17.0 mm (right; mean ± standard deviation) and 52.1 ± 15.9 mm (left). The peak motion speeds were 26.7 ± 10.0 mm/s (right) and 32.2 ± 12.4 mm/s (left) in the inspiratory phase and 22.1 ± 12.7 mm/s (right) and 24.3 ± 10.3 mm/s (left) in the expiratory phase. Excursions and peak motion speeds of the left diaphragm were significantly greater than the right. Higher body mass index (BMI) and vital capacity (VC) were associated with greater excursions and faster peak motion speeds of the diaphragms.Conclusions: Time-resolved quantitative analysis of the diaphragms with dynamic chest radiography demonstrated the characteristics of diaphragmatic motion during forced breathing in a health screening cohort. Higher BMI and VC were associated with excursions and peak motion speeds of the diaphragms.