[Paradigm Shift in Respiratory Diagnosis: Current Status and Future Prospects of Dynamic Chest Radiography].

Dynamic chest radiography (DCR) is a flat-panel detector (FPD) -based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view of FPDs permits real-time observation of motion/kinetic findings on the entire lungs, right and left diaphragm, ribs, and chest wall; heart wall motions; respiratory changes in lung density; and diameter of the intrathoracic trachea. Since the dynamic FPDs had been developed in the early 2000s, we focused on the potential of dynamic FPDs for functional X-ray imaging and have launched a research project for the development of an imaging protocol and digital image-processing techniques for the DCR. The quantitative analysis of motion/kinetic findings is helpful for a better understanding of pulmonary function, because the interpretation of dynamic chest radiographs is challenging and time-consuming for radiologists, pulmonologists, and surgeons. Recent clinical studies have demonstrated the usefulness of DCR combined with the digital image processing techniques for the evaluation of pulmonary function and circulation. Especially, there is a major concern in color-mapping images based on dynamic changes in radiographic lung density, where pulmonary impairments can be detected as color defects, even without the use of contrast media or radioactive medicine. Dynamic chest radiography is now commercially available for the use in general X-ray room and therefore can be deployed as a simple and rapid means of functional imaging in both routine and emergency medicine. This review article describes the current status and future prospects of DCR, which might bring a paradigm shift in respiratory diagnosis.

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.

Chest Dynamic-Ventilatory Digital Radiography in Chronic Obstructive or Restrictive Lung Disease.

OBJECTIVE: The aim of this study was to identify the relationships between parameters obtained from dynamic-ventilatory digital radiography (DR) and ventilatory disorders. METHODS: This study comprised 273 participants with respiratory diseases who underwent spirometry and functional residual capacity measurements (104 with normal findings on spirometry as controls, 139 with an obstructive lung disorder, 30 with a restrictive lung disorder) were assessed by dynamic-ventilatory DR. Sequential chest radiography images of the patient's slow and maximum breathing were captured at 15 frames per second by a dynamic flat-panel imaging system. The system measured the following parameters: lung area at maximum inspiration divided by height (lung area_in/height), changes in tracheal diameter due to respiratory motions, rate of tracheal narrowing, diaphragmatic motion, and rate of change in lung area due to respiratory motion. Relationships between these parameters and ventilatory disorders were analyzed. RESULTS: Lung area_in/height in patients with restrictive disorders showed significant decreases. Tracheal diameter change and tracheal narrowing rate in patients with obstructive disorders were significantly increased compared to both the control participants and patients with restrictive disorders. Patients with obstructive disorders and patients with restrictive disorders showed decreased diaphragmatic motion and lung area change rate. With the restrictive disorders as references, the area under the curve (AUC), sensitivity and specificity of lung area_in/height were 0.88, 0.77, and 0.88, respectively. With the obstructive disorders as references, the AUC, sensitivity and specificity of tracheal narrowing rate were 0.67, 0.53 and 0.81, respectively. CONCLUSION: Dynamic-ventilatory DR shows potential as a method for the detection and evaluation of ventilatory disorders in patients with respiratory diseases.

Dynamic Chest X-Ray Using a Flat-Panel Detector System: Technique and Applications.

Dynamic X-ray (DXR) is a functional imaging technique that uses sequential images obtained by a flat-panel detector (FPD). This article aims to describe the mechanism of DXR and the analysis methods used as well as review the clinical evidence for its use. DXR analyzes dynamic changes on the basis of X-ray translucency and can be used for analysis of diaphragmatic kinetics, ventilation, and lung perfusion. It offers many advantages such as a high temporal resolution and flexibility in body positioning. Many clinical studies have reported the feasibility of DXR and its characteristic findings in pulmonary diseases. DXR may serve as an alternative to pulmonary function tests in patients requiring contact inhibition, including patients with suspected or confirmed coronavirus disease 2019 or other infectious diseases. Thus, DXR has a great potential to play an important role in the clinical setting. Further investigations are needed to utilize DXR more effectively and to establish it as a valuable diagnostic tool.

Dynamic-Ventilatory Digital Radiography in Air Flow Limitation: A Change in Lung Area Reflects Air Trapping.

OBJECTIVE: The aim of this study was to determine the utility of dynamic-ventilatory digital radiography (DR) for pulmonary function assessment in patients with airflow limitation. METHODS: One hundred and eighteen patients with airflow limitation (72 patients with lung cancer before surgery, 35 patients with chronic obstructive pulmonary disease [COPD], 6 patients with asthma, and 5 patients with asthma-COPD overlap syndrome) were assessed with dynamic-ventilatory DR. The patients were instructed to inhale and exhale slowly and maximally. Sequential chest X-ray images were captured in 15 frames per second using a dynamic flat-panel imaging system. The relationship between the lung area and the rate of change in the lung area due to respiratory motion with respect to pulmonary function was analyzed. RESULTS: The rate of change in the lung area from maximum inspiration to maximum expiration (Rs ratio) was associated with the RV/TLC ratio (r = 0.48, p < 0.01) and the percentage of the predicted FEV1 (r = -0.33, p < 0.01) in patients with airflow limitations. The Rs ratio also decreased in an FEV1-dependent manner. CONCLUSION: The rate of change in the lung area due to respiratory motion evaluated with dynamic DR reflects air trapping. Dynamic DR is a potential tool for the comprehensive assessment of pulmonary function in patients with COPD.

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.

Detection of Pulmonary Embolism Based on Reduced Changes in Radiographic Lung Density During Cardiac Beating Using Dynamic Flat-panel Detector: An Animal-based Study.

RATIONALE AND OBJECTIVES: To assess the capacity of dynamic flat-panel detector imaging without the use of contrast media to detect pulmonary embolism (PE) based on temporal changes in radiographic lung density during cardiac beating. MATERIALS AND METHODS: Sequential chest radiographs of six pigs were acquired using a dynamic flat-panel detector system. A porcine model of PE was developed, and temporal changes in pixel values in the imaged lungs were analyzed during a whole cardiac cycle. Mean differences in temporal changes in pixel values between affected and unaffected lobes were assessed using the paired t test. To facilitate visual evaluation, temporal changes in pixel values were depicted using a colorimetric scale and were compared to the findings of contrast-enhanced images. RESULTS: Affected lobes exhibited a mean reduction of 49.6% in temporal changes in pixel values compared to unaffected lobes within the same animals, and a mean reduction of 41.3% compared to that before vessel blockage in the same lobe. All unaffected lobes exhibited significantly-increased changes in pixel values after vessel blockage (p < 0.01). In all PE models, there were color-deficient areas with shapes and locations that matched well with the perfusion defects confirmed in the corresponding contrast-enhanced images. CONCLUSION: Dynamic chest radiography enables the detection of perfusion defects in the lobe unit based on temporal changes in image density, even without the use of contrast media. Quantification and visualization techniques provide a better understanding of the circulation-induced changes depicted in dynamic chest radiographs.

Recovery of 3D rib motion from dynamic chest radiography and CT data using local contrast normalization and articular motion model.

Dynamic chest radiography (2D x-ray video) is a low-dose and cost-effective functional imaging method with high temporal resolution. While the analysis of rib-cage motion has been shown to be effective for evaluating respiratory function, it has been limited to 2D. We aim at 3D rib-motion analysis for high temporal resolution while keeping the radiation dose at a level comparable to conventional examination. To achieve this, we developed a method for automatically recovering 3D rib motion based on 2D-3D registration of x-ray video and single-time-phase computed tomography. We introduce the following two novel components into the conventional intensity-based 2D-3D registration pipeline: (1) a rib-motion model based on a uniaxial joint to constrain the search space and (2) local contrast normalization (LCN) as a pre-process of x-ray video to improve the cost function of the optimization parameters, which is often called the landscape. The effects of each component on the registration results were quantitatively evaluated through experiments using simulated images and real patients' x-ray videos obtained in a clinical setting. The rotation-angle error of the rib and the mean projection contour distance (mPCD) were used as the error metrics. The simulation experiments indicate that the proposed uniaxial joint model improved registration accuracy. By searching the rotation axis along with the rotation angle of the ribs, the rotation-angle error and mPCD significantly decreased from 2.246 ±â€¯1.839° and 1.148 ±â€¯0.743 mm to 1.495 ±â€¯0.993° and 0.742 ±â€¯0.281 mm, compared to simply applying De Troyer's model. The real-image experiments with eight patients demonstrated that LCN improved the cost function space; thus, robustness in optimization resulting in an average mPCD of 1.255 ±â€¯0.615 mm. We demonstrated that an anatomical-knowledge based constraint and an intensity normalization, LCN, significantly improved robustness and accuracy in rib-motion reconstruction using chest x-ray video.

Pulmonary Function Diagnosis Based on Respiratory Changes in Lung Density With Dynamic Flat-Panel Detector Imaging: An Animal-Based Study.

OBJECTIVES: The aims of this study were to address the relationship between respiratory changes in image density of the lungs and tidal volume, to compare the changes between affected and unaffected lobes, and to apply this new technique to the diagnosis of atelectasis. MATERIALS AND METHODS: Our animal care committee approved this prospective animal study. Sequential chest radiographs of 4 pigs were obtained under respiratory control with a ventilator using a dynamic flat-panel detector system. Porcine models of atelectasis were developed, and the correlation between the tidal volume and changes in pixel values measured in the lungs were analyzed. The mean difference in respiratory changes in pixel values between both lungs was tested using paired t tests. To facilitate visual evaluation, respiratory changes in pixel values were visualized in the form of a color display, that is, as changes in color scale. RESULTS: Average pixel values in the lung regions changed according to forced respiration. High linearity was observed between changes in pixel values and tidal volume in the normal models (r = 0.99). Areas of atelectasis displayed significantly reduced changes in pixel values (P < 0.05). Of all atelectasis models with air trapping and air inflow restriction, 92.7% (19/20) were visualized as color-defective or color-marked areas on functional images, respectively. CONCLUSION: Dynamic chest radiography allows for the relative evaluation of tidal volume, the detection of ventilation defects in the lobe unit, and a differential diagnosis between air trapping and air inflow restriction, based on respiratory changes in image density of the lungs, even without the use of contrast media.

Sonographic classification of testicular tumors by tissue harmonic imaging: experience of 58 cases.

PURPOSE: To evaluate the relationship between our proposed sonographic classification of testicular tumors by tissue harmonic imaging and histological type. METHODS: We retrospectively analyzed 58 testicular tumors and tumor-like lesions [seminomatous germ cell tumor (SGCT): 28; non-seminomatous germ cell tumor (NSGCT): 16; lymphoid and hematopoietic tumor (LHT): 7; Leydig cell tumor: 1; epidermal cyst: 2; and tumor of paratesticular structure (TPS): 4]. We divided a sonographic image into six types for morphological criteria and three types for color Doppler criteria. We examined the relationship between the sonographic classification and histological type. RESULTS: For morphological criteria, there were 21 cases of Type I (36%), 15 Type II (26%), 9 Type III (15%), five Type IV (9%), five Type V (9%), and three Type VI (5%). For color Doppler criteria, there were 47 cases classified as hypervascular (81%), eight as hypovascular (14%), and three as avascular (5%). Most of the SGCTs were divided into types I and II; the NSGCTs into types III, IV, and V; the LHTs into only type II; and the TPSs into type VI. CONCLUSION: We established a sonographic classification of testicular tumors with various histological types. This sonographic classification is potentially useful for estimating the histological type of testicular tumors.

Functional dynamic radiography with computer analysis-for physiological chest imaging and kinematic joint imaging.

We developed a functional digital radiography system that provides physiological and functional information of the chest and/or joints using an X-ray flat-panel detector (FPD) system. During chest examination, sequential chest radiographs are taken from inspiration to expiration in order to analyze diaphragmatic movements. Pixel value changes in localized areas of the lung are then assessed to analyze ventilation and circulation. For limb joints, such as the wrist, shoulder, and knee, sequential radiographs during flexion and extension or rotational movement are considered, and movement angles are analyzed. These imaging techniques and quantitative analyses are promising in screening examinations because they provide physiological and functional information. The entrance surface dose for the detector is approximately 1.9 mGy for chest examination, which is comparable to the dose limit recommended by the International Atomic Energy Agency. Recent related studies are reviewed in this paper.

Kinematic radiography of the hip joint after hip resurfacing arthroplasty.

This study aimed to evaluate the usefulness of dynamic radiography using a dynamic flat-panel detector (FPD) system after hip resurfacing arthroplasty (HRA). A total of 32 hips of 26 patients who underwent HRA were included. Sequential images of active abduction in the supine position and flexion in the 45° semilateral position were obtained using the FPD system. We examined the imaging findings of impingement between the acetabular component and femoral neck with cooperative motion at maximal exercise. Moreover, the central component coordinate of the acetabulum and femoral head sides was measured. For abduction motion, impingement was detected in two (6.3 %) hips between the superior portion of the femoral neck and acetabular component. For flexion motion, impingement was detected in 19 (59.4 %) hips. There were no findings of subluxation between the acetabular component and femoral neck after impingement, but cooperative motion of lumbar and pelvic flexion was observed. There was no significant difference in the center-to-center distance regardless of the presence or absence of impingement. Detailed postoperative kinematics of the hips after HRA showed that the proposed dynamic FPD system could reveal acquired impingement and cooperative motion as dynamic images and possibly reveal findings that would be unobservable using static images.

[Development of Digital Subtraction Angiography Method for Pediatric Cardiac Angiography Using Subtraction Technique with Heart Rate].

Digital subtraction angiography (DSA) has been used in head and abdomen. However, in recent years, the use of cardiac DSA has been reported. In this report, we discuss the development of a DSA method with heart rate to clearly visualize blood vessels of pediatric patients. The patients included five children who underwent pulmonary artery angioplasty. We used a process to resize the original images and performed two kinds of subtraction methods as well as visually evaluated the images and performed comparisons between pairs of images using the Scheffe's method. Subtraction techniques were used to eliminate motion artifacts of the heart, thoracic vertebra, ribs, and diaphragm. Visualization of the image of blood vessels of pulmonary arteries using the subtraction technique with heart rate was superior to the visualization of the conventional DSA images of peripheral blood vessels of the lung and pulmonary arteries. Use of subtraction technique with heart rate makes it possible to obtain more detailed information on pediatric cardiac angiography images noninvasively.

Estimation of organ doses and effective doses in image-guided respiration-gated radiotherapy.

Dose conformity in thoracic and abdominal ion-beam radiotherapy is degraded by respiratory motion. To improve conformity, an image-guided respiration-gated system can be used in the treatment room. The purpose of this study was to estimate the organ doses and effective doses to patients from an image-guided respiration-gated system. Glass dosemeters were inserted into an adult anthropomorphic phantom and were attached to the surface on the phantom. The phantom was placed on the treatment couch, and the imaging dose from fluoroscopy was evaluated. In addition to the organ doses, the effective doses were also estimated according to the ICRP Publication 103. The irradiation time is over 3-5 min per beam angle. When image acquisition conditions were assumed for thoracic treatment, the effective doses and maximal skin doses were 0.48-0.79 mSv and 5.9-9.9 mGy, respectively. The estimated doses can be the base data for considering radiological protection in the radiotherapy.

[Motion Analysis of Lumbar Spine and Hip Joint on Sequential Radiographs Acquired with a Dynamic Flat-panel Detector (FPD) System].

PURPOSE: To design an evaluation method for lumbar spine and hip joint function using dynamic radiography using a flat-panel detector (FPD) system. METHOD: Sixteen healthy subjects (males; age range, 22-60 years; median, 27 years) and 9 patients (7 males and 2 females; age range, 67-85 years; median, 73 years) with L4 degenerative spondylolisthesis were examined using a dynamic FPD system (CANON Inc.). Sequential images were captured with the subjects in the standing position with maximal forward bending followed by backward bending for 10 s. The lateral lumbar radiographs were obtained at 2 frames/s (fps). The flexion-extension angles of L1 and S1 were measured on those images. RESULTS AND DISCUSSION: The range of motion (ROM) of the lumbar joints was significantly larger in the healthy group (82.4 ± 8.7°) than in the disease group (50.4 ± 8.5°; p<0.05). The ROM of the pelvic region was significantly smaller in the healthy group (26.9 ± 17.1°) than in the disease group (53.1 ± 17.6°; p<0.05). The healthy subjects exhibited a normal lumbar-pelvic rhythm. In the disease group, hip joint movements tended to be completed earlier compared with those in the healthy group. In the disease group, the loss of lumbar flexibility was compensated by an increase in hip joint motion due to the lumbar disease. CONCLUSION: The dynamic FPD system is a convenient imaging modality for the diagnosis of lumbar diseases through the assessment of locomotive function in the lumbar spine and hip joints.

[Phantom Study on Dose Reduction Using Iterative Reconstruction in Low-dose Computed Tomography for Lung Cancer Screening].

We investigated dose reduction ability of an iterative reconstruction technology for low-dose computed tomography (CT) for lung cancer screening. The Sinogram Affirmed Iterative Reconstruction (SAFIRE) provided in a multi slice CT system, Somatom Definition Flash (Siemens Healthcare) was used. An anthropomorphic chest phantom (N-1, Kyoto Kagaku) was scanned at volume CT dose index (CTDIvol) of 0.50-11.86 mGy with 120 kV. For noise (standard deviation) and contrast-to-noise ratio (CNR) measurements, CTP486 and CTP515 modules in the Catphan (The Phantom Laboratory) were scanned. Radiological technologists were participated in the perceptual comparison. SAFIRE reduced the SD values by approximately 50% compared with filter back projection (FBP). The estimated dose reduction rates by SAFIRE determined from the perceptual comparison was approximately 23%, while 75% dose reduction rate was expected from the SD value reduction of 50%.