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Recently, interest and advances in artificial intelligence (AI) including deep learning for medical images have surged. As imaging plays a major role in the assessment of pulmonary diseases, various AI algorithms have been developed for chest imaging. Some of these have been approved by governments and are now commercially available in the marketplace. In the field of chest radiology, there are various tasks and purposes that are suitable for AI: initial evaluation/triage of certain diseases, detection and diagnosis, quantitative assessment of disease severity and monitoring, and prediction for decision support. While AI is a powerful technology that can be applied to medical imaging and is expected to improve our current clinical practice, some obstacles must be addressed for the successful implementation of AI in workflows. Understanding and becoming familiar with the current status and potential clinical applications of AI in chest imaging, as well as remaining challenges, would be essential for radiologists and clinicians in the era of AI. This review introduces the potential clinical applications of AI in chest imaging and also discusses the challenges for the implementation of AI in daily clinical practice and future directions in chest imaging.

Objective. To unify the style of computed tomography (CT) images from multiple sources, we propose a novel multi-domain image translation network to convert CT images from different scan parameters and manufacturers by simply changing a routing vector. Approach. Unlike the existing multi-domain translation techniques, our method is based on a shared encoder and a routable decoder architecture to maximize the expressivity and conditioning power of the network. Main results. Experimental results show that the proposed CT image conversion can minimize the variation of image characteristics caused by imaging parameters, reconstruction algorithms, and hardware designs. Quantitative results and clinical evaluation from radiologists also show that our method can provide accurate translation results. Significance. Quantitative evaluation of CT images from multi-site or longitudinal studies has been a difficult problem due to the image variation depending on CT scan parameters and manufacturers. The proposed method can be utilized to address this for the quantitative analysis of multi-domain CT images.

OBJECTIVE Patients with chronic obstructive pulmonary disease (COPD) are known to be at risk of osteoporosis. The purpose of this study was to evaluate the association between thoracic vertebral bone density measured on chest CT (DThorax) and clinical variables, including survival, in patients with COPD. MATERIALS AND METHODS A total of 322 patients with COPD were selected from the Korean Obstructive Lung Disease (KOLD) cohort. DThorax was measured by averaging the CT values of three consecutive vertebral bodies at the level of the left main coronary artery with a round region of interest as large as possible within the anterior column of each vertebral body using an in-house software. Associations between DThorax and clinical variables, including survival, pulmonary function test (PFT) results, and CT densitometry, were evaluated. RESULTS The median follow-up time was 7.3 years (range: 0.1-12.4 years). Fifty-six patients (17.4%) died. DThorax differed significantly between the different Global Initiative for Chronic Obstructive Lung Disease stages. DThorax correlated positively with body mass index (BMI), some PFT results, and the six-minute walk distance, and correlated negatively with the emphysema index (EI) (all p < 0.05). In the univariate Cox analysis, older age (hazard ratio [HR], 3.617; 95% confidence interval [CI], 2.119-6.173, p < 0.001), lower BMI (HR, 3.589; 95% CI, 2.122-6.071, p < 0.001), lower forced expiratory volume in one second (FEV₁) (HR, 2.975; 95% CI, 1.682-5.262, p < 0.001), lower diffusing capacity of the lung for carbon monoxide corrected with hemoglobin (DLCO) (HR, 4.595; 95% CI, 2.665-7.924, p < 0.001), higher EI (HR, 3.722; 95% CI, 2.192-6.319, p < 0.001), presence of vertebral fractures (HR, 2.062; 95% CI, 1.154-3.683, p = 0.015), and lower DThorax (HR, 2.773; 95% CI, 1.620-4.746, p < 0.001) were significantly associated with all-cause mortality and lung-related mortality. In the multivariate Cox analysis, lower DThorax (HR, 1.957; 95% CI, 1.075-3.563, p = 0.028) along with older age, lower BMI, lower FEV₁, and lower DLCO were independent predictors of all-cause mortality. CONCLUSION The thoracic vertebral bone density measured on chest CT demonstrated significant associations with the patients' mortality and clinical variables of disease severity in the COPD patients included in KOLD cohort.

We aimed to evaluate the performance of a fully automated quantitative software in detecting interstitial lung abnormalities (ILA) according to the Fleischner Society guidelines on routine chest CT compared with radiologists' visual analysis.This retrospective single-centre study included participants with ILA findings and 1:2 matched controls who underwent routine chest CT using various CT protocols for health screening. Two thoracic radiologists independently reviewed the CT images using the Fleischner Society guidelines. We developed a fully automated quantitative tool for detecting ILA by modifying deep learning-based quantification of interstitial lung disease and evaluated its performance using the radiologists' consensus for ILA as a reference standard.A total of 336 participants (mean age, 70.5 ± 6.1 years; M:F = 282:54) were included. Inter-reader agreements were substantial for the presence of ILA (weighted κ, 0.74) and fair for its subtypes (weighted κ, 0.38). The quantification system for identifying ILA using a threshold of 5 % in at least one zone showed 67.6 % sensitivity, 93.3 % specificity, and 90.5 % accuracy. Eight of 20 (40 %) false positives identified by the system were underestimated by readers for ILA extent. Contrast-enhancement in a certain vendor and suboptimal inspiration caused a true false-positive on the system (all P 0.05). The best cut-off value of abnormality extent detecting ILA on the system was 3.6 % (sensitivity, 84.8 %; specificity 92.4 %).Inter-reader agreement was substantial for ILA but only fair for its subtypes. Applying an automated quantification system in routine clinical practice may aid the objective identification of ILA.

Background Evaluation of interstitial lung disease (ILD) at CT is a challenging task that requires experience and is subject to substantial interreader variability. Purpose To investigate whether a proposed content-based image retrieval (CBIR) of similar chest CT images by using deep learning can aid in the diagnosis of ILD by readers with different levels of experience. Materials and Methods This retrospective study included patients with confirmed ILD after multidisciplinary discussion and available CT images identified between January 2000 and December 2015. Database was composed of four disease classes: usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia, and chronic hypersensitivity pneumonitis. Eighty patients were selected as queries from the database. The proposed CBIR retrieved the top three similar CT images with diagnosis from the database by comparing the extent and distribution of different regional disease patterns quantified by a deep learning algorithm. Eight readers with varying experience interpreted the query CT images and provided their most probable diagnosis in two reading sessions 2 weeks apart, before and after applying CBIR. Diagnostic accuracy was analyzed by using McNemar test and generalized estimating equation, and interreader agreement was analyzed by using Fleiss κ. Results A total of 288 patients were included (mean age, 58 years ± 11 [standard deviation]; 145 women). After applying CBIR, the overall diagnostic accuracy improved in all readers (before CBIR, 46.1% [95% CI: 37.1, 55.3]; after CBIR, 60.9% [95% CI: 51.8, 69.3]

Background We aimed to compare the myocardial ischemic burden assessed using semi-quantitative and quantitative analysis of computed tomography-myocardial perfusion imaging (CT-MPI) with that of single-photon emission computed tomography (SPECT). Methods From 2011 to 2013, 97 patients who underwent CT-MPI and SPECT were evaluated. The extent and severity of perfusion defects were assessed on a 5-point scale using a standard 16-segment model, and were expressed as summed stress score (SSS) and summed difference score (SDS). Receiver operating characteristic (ROC) curves for quantitative parameters were generated for the diagnosis of abnormal perfusion defect (SSS ≥ 4) and presence of ischemia (SDS ≥ 2) on SPECT. Results On CT-MPI, 298 (19.2%) of the 1552 segments showed perfusion abnormalities during stress, whereas perfusion abnormalities were shown in 179 (11.5%) segments on SPECT-MPI. On a per-person basis, there was good agreement, with intraclass correlation coefficients of 0.78 for SSS and 0.72 for SDS. A significant reduction of attenuation in stress and myocardial perfusion reserve index, along with an increase in % defect volume of CT-MPI, were demonstrated as the degree of perfusion defect or ischemia on SPECT increased. On the ROC curves, % defect volume on CT-MPI demonstrated the highest area under the curve: 0.91 for abnormal perfusion defect and 0.89 (all p Conclusions Semi-quantitative analysis of CT-MPI showed good accordance with SPECT. A quantitative approach for CT-MPI, especially % defect volume, may provide additional value in the identification of myocardial perfusion abnormalities. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT01696006 .

OBJECTIVE Emphysema and small-airway disease are the two major components of chronic obstructive pulmonary disease (COPD). We propose a novel method of quantitative computed tomography (CT) emphysema air-trapping composite (EAtC) mapping to assess each COPD component. We analyzed the potential use of this method for assessing lung function in patients with COPD. MATERIALS AND METHODS A total of 584 patients with COPD underwent inspiration and expiration CTs. Using pairwise analysis of inspiration and expiration CTs with non-rigid registration, EAtC mapping classified lung parenchyma into three areas: Normal, functional air trapping (fAT), and emphysema (Emph). We defined fAT as the area with a density change of less than 60 Hounsfield units (HU) between inspiration and expiration CTs among areas with a density less than -856 HU on inspiration CT. The volume fraction of each area was compared with clinical parameters and pulmonary function tests (PFTs). The results were compared with those of parametric response mapping (PRM) analysis. RESULTS The relative volumes of the EAtC classes differed according to the Global Initiative for Chronic Obstructive Lung Disease stages (p < 0.001). Each class showed moderate correlations with forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity (FVC) (r = -0.659-0.674, p < 0.001). Both fAT and Emph were significant predictors of FEV1 and FEV1/FVC (R² = 0.352 and 0.488, respectively; p < 0.001). fAT was a significant predictor of mean forced expiratory flow between 25% and 75% and residual volume/total vital capacity (R² = 0.264 and 0.233, respectively; p < 0.001), while Emph and age were significant predictors of carbon monoxide diffusing capacity (R² = 0.303; p < 0.001). fAT showed better correlations with PFTs than with small-airway disease on PRM. CONCLUSION The proposed quantitative CT EAtC mapping provides comprehensive lung functional information on each disease component of COPD, which may serve as an imaging biomarker of lung function.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous condition with variable clinical and pathophysiologic features. Functional information of the lungs is important to understand the complex pathophysiology of COPD. With recent technical advances in the CT imaging and magnetic resonance imaging (MRI), various imaging techniques have been used for the evaluation of functional changes in COPD. The quantitative CT imaging can be used to objectively assess the severity of emphysema, airway wall changes, air trapping, and other comorbidities, which are correlated with functional aspect of COPD. The dual-energy CT imaging and functional MRI can directly assess and visualize the functional changes such as ventilation, perfusion, and ventilation–perfusion relationship with anatomically matched structural information of the lung in COPD. In this chapter, we will review the current technical status of functional imaging briefly, and focus on its clinical applications, limitations, and some of the most recent works in COPD.

Background/Aims To evaluate the geographic and demographic variabilities of the quantitative parameters of computed tomography perfusion (CTP) of the left ventricular (LV) myocardium in patients with normal coronary artery on computed tomography angiography (CTA). Methods From a multicenter CTP registry of stress and static computed tomography, we retrospectively recruited 113 patients (mean age, 60 years; 57 men) without perfusion defect on visual assessment and minimal (< 20% of diameter stenosis) or no coronary artery disease on CTA. Using semiautomatic analysis software, quantitative parameters of the LV myocardium, including the myocardial attenuation in stress and rest phases, transmural perfusion ratio (TPR), and myocardial perfusion reserve index (MPRI), were evaluated in 16 myocardial segments. Results In the lateral wall of the LV myocardium, all quantitative parameters except for MPRI were significantly higher compared with those in the other walls. The MPRI showed consistent values in all myocardial walls (anterior to lateral wall: range, 25% to 27%; p = 0.401). At the basal level of the myocardium, all quantitative parameters were significantly lower than those at the mid- and apical levels. Compared with men, women had significantly higher values of myocardial attenuation and TPR. Age, body mass index, and Framingham risk score were significantly associated with the difference in myocardial attenuation. Conclusions Geographic and demographic variabilities of quantitative parameters in stress myocardial CTP exist in healthy subjects without significant coronary artery disease. This information may be helpful when assessing myocardial perfusion defects in CTP.

Purpose The purpose of this study was to identify and characterize the 100 top-cited articles in pulmonary imaging. Materials and methods From the database of Journal Citation Reports, 274 journals whose scope included pulmonary imaging were selected. The Web of Science search tools were then used to identify the 100 top-cited articles in the subject of pulmonary imaging published in these journals. The parameters used to analyze the characteristics of the 100 top-cited articles were journal (including subject category and impact factor), publication year, number of citations and annual citations, department and institution of authors, country of origin, article type, imaging technique, and topic. Results The 100 top-cited articles in pulmonary imaging were published between 1953 and 2012, with 43 published between 2000 and 2009. Citations ranged from 199 to 1447, and annual citations ranged from 5.1 to 314. The majority of articles were published in radiology or imaging journals (n=64), originated in the United States (n=49), were original articles (n=87), used computed tomography (n=66), and were based on the topic of pulmonary thromboembolism (n=18). Department of Radiology, Mayo Clinic (n=7), and Department of Radiology, University of British Columbia and Vancouver General Hospital (n=7), were the leading institutions, and Muller NL (n=11) was the most prolific author. Conclusions Our study lists the 100 top-cited articles in pulmonary imaging, provides an insight into historical developments, and allows for recognition of advances in this field.

OBJECTIVE To assess the regional ventilation in patients with asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) using xenon-ventilation dual-energy CT (DECT), and to compare it to that in patients with COPD. MATERIALS AND METHODS Twenty-one patients with ACOS and 46 patients with COPD underwent xenon-ventilation DECT. The ventilation abnormalities were visually determined to be 1) peripheral wedge/diffuse defect, 2) diffuse heterogeneous defect, 3) lobar/segmental/subsegmental defect, and 4) no defect on xenon-ventilation maps. Emphysema index (EI), airway wall thickness (Pi10), and mean ventilation values in the whole lung, peripheral lung, and central lung areas were quantified and compared between the two groups using the Student's t test. RESULTS Most patients with ACOS showed the peripheral wedge/diffuse defect (n = 14, 66.7%), whereas patients with COPD commonly showed the diffuse heterogeneous defect and lobar/segmental/subsegmental defect (n = 21, 45.7% and n = 20, 43.5%, respectively). The prevalence of ventilation defect patterns showed significant intergroup differences (p < 0.001). The quantified ventilation values in the peripheral lung areas were significantly lower in patients with ACOS than in patients with COPD (p = 0.045). The quantified Pi10 was significantly higher in patients with ACOS than in patients with COPD (p = 0.041); however, EI was not significantly different between the two groups. CONCLUSION The ventilation abnormalities on the visual and quantitative assessments of xenon-ventilation DECT differed between patients with ACOS and patients with COPD. Xenon-ventilation DECT may demonstrate the different physiologic changes of pulmonary ventilation in patients with ACOS and COPD.

To investigate the reproducibility of computer-aided detection (CAD) for detection of pulmonary nodules and masses for consecutive chest radiographies (CXRs) of the same patient within a short-term period. A total of 944 CXRs (Chest PA) with nodules and masses, recorded between January 2010 and November 2016 at the Asan Medical Center, were obtained. In all, 1092 regions of interest for the nodules and mass were delineated using an in-house software. All CXRs were randomly split into 6:2:2 sets for training, development, and validation. Furthermore, paired follow-up CXRs (n = 121) acquired within one week in the validation set, in which expert thoracic radiologists confirmed no changes, were used to evaluate the reproducibility of CAD by two radiologists (R1 and R2). The reproducibility comparison of four different convolutional neural net algorithms and two chest radiologists (with 13- and 14-years’ experience) was conducted. Model performances were evaluated by figure-of-merit (FOM) analysis of the jackknife free-response receiver operating curve and reproducibility rates were evaluated in terms of percent positive agreement (PPA) and Chamberlain’s percent positive agreement (CPPA). Reproducibility analysis of the four CADs and R1 and R2 showed variations in the PPA and CPPA. Model performance of YOLO (You Only Look Once) v2 based eDenseYOLO showed a higher FOM (0.89; 0.85–0.93) than RetinaNet (0.89; 0.85–0.93) and atrous spatial pyramid pooling U-Net (0.85; 0.80–0.89). eDenseYOLO showed higher PPAs (97.87%) and CPPAs (95.80%) than Mask R-CNN, RetinaNet, ASSP U-Net, R1, and R2 (PPA: 96.52%, 94.23%, 95.04%, 96.55%, and 94.98%; CPPA: 93.18%, 89.09%, 90.57%, 93.33%, and 90.43%). There were moderate variations in the reproducibility of CAD with different algorithms, which likely indicates that measurement of reproducibility is necessary for evaluating CAD performance in actual clinical environments.

To develop a model for differentiating the predominant subtype-based prognostic groups of lung adenocarcinoma using CT radiomic features, and to validate its performance in comparison with radiologists’ assessments. A total of 993 patients presenting with invasive lung adenocarcinoma between March 2010 and June 2016 were identified. Predominant histologic subtypes were categorized into three groups according to their prognosis (group 0: lepidic; group 1: acinar/papillary; group 2: solid/micropapillary). Seven hundred eighteen radiomic features were extracted from segmented lung cancers on contrast-enhanced CT. A model-development set was formed from the images of 893 patients, while 100 image sets were reserved for testing. A least absolute shrinkage and selection operator method was used for feature selection. Performance of the radiomic model was evaluated using receiver operating characteristic curve analysis, and accuracy on the test set was compared with that of three radiologists with varying experiences (6, 7, and 19 years in chest CT). Our model differentiated the three groups with areas under the curve (AUCs) of 0.892 and 0.895 on the development and test sets, respectively. In pairwise discrimination, the AUC was highest for group 0 vs. 2 (0.984). The accuracy of the model on the test set was higher than the averaged accuracy of the three radiologists without statistical significance (73.0% vs. 61.7%, p = 0.059). For group 2, the model achieved higher PPV than the observers (85.7% vs. 35.0–48.4%). Predominant subtype-based prognostic groups of lung adenocarcinoma were classified by a CT-based radiomic model with comparable performance to radiologists. • A CT-based radiomic model differentiated three prognosis-based subtype groups of lung adenocarcinoma with areas under the curve (AUCs) of 0.892 and 0.895 on development and test sets, respectively. • The CT-based radiomic model showed near perfect discrimination between group 0 and group 2 (AUCs, 0.984–1.000). • The accuracy of the CT-based radiomic model was comparable to the averaged accuracy of the three radiologists with 6, 7, and 19 years of clinical experience in chest CT (73.0% vs. 61.7%, p = 0.059), achieving a higher positive predictive value for group 2 than the observers (85.7% vs. 35.0–48.4%).

Sixteen of 45 patients with severe fever with thrombocytopenia (36%) were admitted to an intensive care unit; 9 (56%) developed invasive pulmonary aspergillosis (IPA) within a median of 8 days (range, 2–11). Mortality was higher in the IPA vs non-IPA patients and in those without vs with antifungal therapy.

Background: The full-scale airway network (FAN) flow model shows excellent agreement with limited functional imaging data but requires further validation prior to clinical use. Purpose: To validate the ventilation distributions computed with the FAN flow model with xenon ventilation from xenon-enhanced dual-energy (DE) CT in participants with chronic obstructive pulmonary disease (COPD). Materials and Methods: in this prospective study, the FAN model extracted structural data from xenon-enhanced DE CT images of men with COPD scanned between June 2012 and July 2013 to compute gas ventilation dynamics. The ventilation distributions on the middle cross-section plane, percentage lobar ventilation, and ventilation heterogeneity quantified by the coefficient of variation (CV) were compared between xenon-enhanced DE CT imaging and the FAN model. The relationship between the ventilation parameters with the densitometry and pulmonary function test results was demonstrated. The agreements and correlations between the parameters were measured using the concordance correlation coefficient and the Pearson correlation coefficient. Results: Twenty-two men with COPD (mean age, 67 years +/- 7 [standard deviation]) were evaluated. The percentage lobar ventilation computed with FAN showed a strong positive correlation with xenon-enhanced DE CT data (r = 0.7, P < .001). Ninety-five percent of lobar ventilation CV differences lay within 95% confidence intervals. Correlations of the percentage lobar ventilation were negative for percentage emphysema (xenon-enhanced DE CT: r = -0.38, P < .001; FAN: r = -0.23, P = .02) but were positive for percentage normal tissue volume (xenon-enhanced DE CT: r = 0.78, P < .001; FAN: r = 0.45, P < .001). Lung CVs of FAN revealed negative correlations with the spirometry results (CVFAN vs percentage predicted forced expiratory volume in 1 second: r = -0.75, P < .001; CVFAN vs ratio of forced expiratory volume in 1 second to forced vital capacity: r = -0.67, P < .001). Conclusion: The full-scale airway network modeled lobar ventilation in patients with chronic obstructive pulmonary disease correlated with the xenon-enhanced dual-energy CT imaging data. (C) RSNA, 2020, Cancer Research UKCancer Research UK [C5255]; Engineering and Physical Sciences Research CouncilUK Research & Innovation (UKRI)Engineering & Physical Sciences Research Council (EPSRC) [A16466]; NIHR Oxford Biomedical Research CentreNational Institute for Health Research (NIHR), Supported by the Cancer Research UK (grant C5255), Engineering and Physical Sciences Research Council (grant A16466), and NIHR Oxford Biomedical Research Centre.

The assessment of pulmonary function, including ventilation and perfusion status, is important in addition to the evaluation of structural changes of the lung parenchyma in various pulmonary diseases. The dual-energy computed tomography (DECT) technique can provide the pulmonary functional information and high resolution anatomic information simultaneously. The application of DECT for the evaluation of pulmonary function has been investigated in various pulmonary diseases, such as pulmonary embolism, asthma and chronic obstructive lung disease and so on. In this review article, we will present principles and technical aspects of DECT, along with clinical applications for the assessment pulmonary function in various lung diseases.

OBJECTIVES The aim of this study was to assess the feasibility of combined xenon-enhanced ventilation (V) and iodine-enhanced perfusion (Q) dual-energy computed tomography (DECT) to evaluate regional V and Q status in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS Combined V and Q DECT imaging was performed in 52 prospectively enrolled male COPD patients. Virtual noncontrast images, V maps, and Q maps were anatomically coregistered with deformable registration and evaluated using in-house software. After normalization of the V and Q values of each pixel, normalized V and Q, V/Qratio, and VQmin (ie, the smaller of the V and Q in each pixel) maps were generated. For visual analysis, the V/Qratio pattern was determined to be matched, mismatched, or reversed mismatched and compared with the regional disease patterns--emphysema with/without bronchial wall thickening, bronchial wall thickening, or normal parenchyma--in each segment. The mean V, Q, V/Qratio, and VQmin values and the standard deviation of the V/Qratio (V/QSD) of each patient were quantified and compared with pulmonary function test (PFT) parameters using the Pearson correlation test. RESULTS Segments with normal parenchyma showed a matched V/Qratio pattern, whereas segments with bronchial wall thickening commonly showed a reversed mismatched V/Qratio pattern. In the emphysema areas, the matched, mismatched, and reversed mismatched patterns were mixed without a dominant pattern. In quantitative analysis, the mean V, Q, VQmin, and V/Qratio values were significantly and positively correlated with PFT parameters (r = 0.290-0.819; P < 0.05). The V/QSD was significantly and negatively correlated with PFT parameters (r = -0.439 to -0.736; P < 0.001). VQmin values showed the best correlation with PFT parameters (r = 0.483-0.819; P < 0.001). CONCLUSIONS Visual and quantitative assessment of the regional V, Q, V/Qratio, and VQmin is feasible with combined V and Q DECT imaging and significantly correlate with PFT results in COPD patients. Assessing disease patterns using conventional computed tomography images may not provide correct evaluation of regional V and Q in COPD patients with emphysema.

Objective To assess the performance of content-based image retrieval (CBIR) of chest CT for diffuse interstitial lung disease (DILD). Materials and methods The database was comprised by 246 pairs of chest CTs (initial and follow-up CTs within two years) from 246 patients with usual interstitial pneumonia (UIP, n = 100), nonspecific interstitial pneumonia (NSIP, n = 101), and cryptogenic organic pneumonia (COP, n = 45). Sixty cases (30-UIP, 20-NSIP, and 10-COP) were selected as the queries. The CBIR retrieved five similar CTs as a query from the database by comparing six image patterns (honeycombing, reticular opacity, emphysema, ground-glass opacity, consolidation and normal lung) of DILD, which were automatically quantified and classified by a convolutional neural network. We assessed the rates of retrieving the same pairs of query CTs, and the number of CTs with the same disease class as query CTs in top 1-5 retrievals. Chest radiologists evaluated the similarity between retrieved CTs and queries using a 5-scale grading system (5-almost identical; 4-same disease; 3-likelihood of same disease is half; 2-likely different; and 1-different disease). Results The rate of retrieving the same pairs of query CTs in top 1 retrieval was 61.7% (37/60) and in top 1-5 retrievals was 81.7% (49/60). The CBIR retrieved the same pairs of query CTs more in UIP compared to NSIP and COP (p = 0.008 and 0.002). On average, it retrieved 4.17 of five similar CTs from the same disease class. Radiologists rated 71.3% to 73.0% of the retrieved CTs with a similarity score of 4 or 5. Conclusion The proposed CBIR system showed good performance for retrieving chest CTs showing similar patterns for DILD.

Purpose Objective of this study was to evaluate the effectiveness of the iterative reconstruction of high-pitch dual-source chest CT (IR-HP-CT) scanned with low radiation exposure compared with low dose chest CT (LDCT). Materials and methods This study was approved by the institutional review board. Thirty healthy adult volunteers (mean age 44 years) were enrolled in this study. All volunteers underwent both IR-HP-CT and LDCT. IR-HP-CT was scanned with 120 kVp tube voltage, 30 mAs tube current and pitch 3.2 and reconstructed with sinogram affirmed iterative reconstruction. LDCT was scanned with 120 kVp tube voltage, 40 mAs tube current and pitch 0.8 and reconstructed with B50 filtered back projection. Image noise, and signal to noise ratio (SNR) of the infraspinatus muscle, subcutaneous fat and lung parenchyma were calculated. Cardiac motion artifact, overall image quality and artifacts was rated by two blinded readers using 4-point scale. The dose-length product (DLP) (mGy∙cm) were obtained from each CT dosimetry table. Scan length was calculated from the DLP results. The DLP parameter was a metric of radiation output, not of patient dose. Size-specific dose estimation (SSDE, mGy) was calculated using the sum of the anteroposterior and lateral dimensions and effective radiation dose (ED, mSv) were calculated using CT dosimetry index. Results Approximately, mean 40% of SSDE (2.1 ± 0.2 mGy vs. 3.5 ± 0.3 mGy) and 34% of ED (1.0 ± 0.1 mSv vs. 1.5 ± 0.1 mSv) was reduced in IR-HP-CT compared to LDCT (P < 0.0001). Image noise was reduced in the IR-HP-CT (16.8 ± 2.8 vs. 19.8 ± 3.4, P = 0.0001). SNR of lung and aorta of IR-HP-CT showed better results compared with that of LDCT (22.2 ± 5.9 vs. 33.0 ± 7.8, 1.9 ± 0.4 vs 1.1 ± 0.3, P < 0.0001). The score of cardiac pulsation artifacts were significantly reduced on IR-HP-CT (3.8 ± 0.4, 95% confidence interval, 3.7‒4.0) compared with LDCT (1.6 ± 0.6, 95% confidence interval, 1.3‒1.8) (P < 0.0001). SNR of muscle and fat, beam hardening artifact and overall subjective image quality of the mediastinum, lung and chest wall were comparable on both scans (P ≥ 0.05). Conclusion IR-HP-CT with 120 kVp and 30 mAs tube setting in addition to an iterative reconstruction reduced cardiac motion artifact and radiation exposure while representing similar image quality compared with LDCT.

Intramural esophageal dissection (IED) is an uncommon yet important clinical entity characterized by a rupture or fissure in the esophageal submucosal layer. IED could occur spontaneously or secondary to direct extrinsic injury to the esophageal mucosa. Traditionally, IED has been diagnosed on the swallowing study using water-soluble contrast agents or barium. For alternative diagnostic modalities, upper gastrointestinal endoscopy and chest computed tomography have been frequently performed. However, to the best of our knowledge, the transabdominal ultrasonography (USG) appearance of IED has not been reported in the literature yet. We report an interesting case of IED, which was initially diagnosed on the transabdominal USG.

Aim To assess the relationship between chest computed tomography (CT) findings of patients with toxocariasis and levels of serological markers. Materials and methods A total of 38 cases of patients diagnosed with toxocariasis by enzyme-linked immunosorbent assay (ELISA), CT, and serological markers were retrospectively reviewed. The presence of nodule with or without ground-glass opacity (GGO) halo, consolidation, focal GGO, pleural effusion, and lymphadenopathy at chest CT were evaluated. Statistical analysis was performed with the Fisher's exact test. Results The most common chest CT findings were nodule ( n = 12, 31.6%) and focal GGO ( n = 12, 31.6%). In patients with normal eosinophil levels, focal GGO ( n = 9, 37.5%) was the most common finding. In contrast, nodule with a GGO halo ( n = 7, 50%) was the most common finding in the eosinophilia group. Nodule with a GGO halo was more common in the eosinophilia group, with a statistically significant difference ( p = 0.017). Nodule was more common in the eosinophilia group, and focal GGO was more common in the normal eosinophil group. Conclusion The most common chest CT findings in toxocariasis were nodule with or without GGO halo, and focal GGO. In the eosinophilia group, nodule with a GGO halo was significantly more frequent. Other CT findings did not show a statistically significant relationship with serological markers.

Anaplastic lymphoma kinase (ALK) inhibitor-related pneumonitis (ALK-IIP) is relatively rare but sometimes fatal, so the timely diagnosis of ALK-IIP is important for enabling prompt management. However, the detailed radiologic characteristics and clinical course of ALK-IIP are still unclear. This study was performed to investigate the clinical and radiologic characteristics and risk factors of ALK-IIP in patients with non-small cell lung cancer (NSCLC).A total of 250 NSCLC patients who had been treated with ALK inhibitors were retrospectively enrolled. Chest computed tomography (CT) was classified into 4 CT patterns using the 2013 guideline for idiopathic interstitial pneumonia: cryptogenic organizing pneumonia (COP), hypersensitivity pneumonitis (HP), acute interstitial pneumonia (AIP), and nonspecific interstitial pneumonia. Clinical characteristics including toxicity grading and treatment course were analyzed in regarding to CT patterns. Clinical characteristics were compared between patients with ALK-IIP and without ALK-IIP.ALK-IIP was identified in 11 patients (4.4%). The most common CT pattern was the COP pattern (n = 7, 63.6%) and followed by HP and AIP patterns (both, n = 2, 18.2%). ALK-IIP showed pneumonitis toxicity grade ranged from 1 to 4, and AIP pattern had the highest toxicity grade, followed by HP and COP patterns (median grade: 3.5, 2.5, 1). All of the patients with the COP pattern were successfully treated, while half of patients with the AIP pattern died during treatment. The smoking history and extrathoracic metastasis were more frequent in patients with ALK-IIP (P < .005). The smoking history was associated with a higher incidence of ALK-IIP (odds ratio: 3.586, 95% confidence interval: 1.058-13.432, P = .049).ALK-IIP showed a spectrum of chest CT patterns, which reflected the toxicity grades. The COP pattern was the most common CT pattern of ALK-IIP, and patients with ALK-IIP of the COP pattern were successfully treated. ALK inhibitors should be used with caution in NSCLC patients with smoking history.

Supplemental Digital Content is available in the text, Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by SFTS virus (SFTSV) which involves multiple organ systems, including lungs. However, there is limited data on lung involvement of SFTS. Therefore, the present study investigated the chest radiographic findings of SFTS, including computed tomography (CT), and compared these with those of scrub typhus, which is the most common tick-borne illness in South Korea and share risk factors and occur in similar settings. Medical records of patients with confirmed SFTS and scrub typhus in a tertiary hospital in Seoul (South Korea), between January 2014 and June 2018, were reviewed. Initial chest radiography and CT were reviewed by 2 experienced radiologists. A total of 39 patients with SFTS and 101 patients with scrub typhus were analyzed. All patients except 3 patients with scrub typhus in both groups received chest radiography. Cardiomegaly (90%) and patchy consolidation with ground glass opacity (GGO) pattern (31%) were more common in SFTS group than scrub typhus group (20%, P

OBJECTIVE The aim of this study was to describe computed tomography (CT) findings of nontuberculous mycobacterial (NTM) pulmonary infection in patients with idiopathic interstitial pneumonias (IIP) in comparison with those in patients without IIP. METHODS From November 2001 to October 2012, 810 patients in the NTM registry were retrospectively reviewed. Among them, 42 patients (mean age, 69.7 years; 32 men and 10 women) who were diagnosed as having IIP by either histological or radioclinical criteria were included in our study. Eighty-two age- and sex-matched immunocompetent patients with NTM pulmonary infection and without IIP were selected as the control group. Medical records and CT scans were reviewed. Formal radiologic reports obtained before diagnosis of NTM infection were also reviewed. RESULTS Lobar/segmental consolidation (85.7%) was the most common CT finding in the IIP group, whereas branching centrilobular nodules (95.1%), traction bronchiectasis (79.3%), and volume decrease (58.5%) were common in the control group. Frequencies of these findings were significantly different between the 2 groups (P < 0.001). Most of consolidations were associated with cavity (83.3%) without dominant zonal distribution. Pneumonia or fungal infection (n = 20) was the most common radiologic diagnosis in the IIP group. CONCLUSIONS The NTM pulmonary infection in IIP patients is characterized as lobar/segmental consolidation with/without cavity, different to immunocompetent patients without IIP, and can mimic other diseases especially bacterial/fungal infection.

Although imaging of patient with COPD in not recommended in clinical practice, many researches and drug trial include imaging studies in evaluation of COPD. In particular, thin-section volumetric CT covering the whole lung with following quantitative assessment has been accepted one of the essential components of studies. This chapter encompasses the whole aspect of CT in COPD, including basic CT physics, radiation dose consideration, diagnosis and visual assessment of COPD, fundamentals of quantitative assessment of emphysema, airway wall thickening, and air trapping and its clinical values. Assessment of other components of COPD includes chest wall changes, vascular changes, osteoporosis, and so on. In addition, new emerging imaging methods such as MRI, dual-energy CT, PET, and optical imaging to evaluate not only morphologic but also functional aspects of lung in COPD will be introduced. Functional imaging includes direct visualization of ventilation, perfusion, chest wall motion, and inflammation. The promising results of early studies will be introduced, highlighting the potential of imaging approach for the future studies.

OBJECTIVE This study aimed to determine optimal strength of sinogram-affirmed iterative reconstruction (SAFIRE) and to evaluate image quality (IQ) of low-dose chest computed tomography (LDCT) using SAFIRE compared with iterative reconstruction in image space (IRIS) and filtered back projection (FBP). METHODS Thirty patients underwent LDCT. Computed tomography (CT) was reconstructed using 5 strengths of SAFIRE (S1-S5), IRIS, and FBP. Objective noise of CT was measured. Two radiologists evaluated CT for subjective IQ, beam-hardening artifacts, and overall IQ. RESULTS Measured noise was highest in FBP, followed by S1, S2, S3, IRIS, S4, and S5. S2 and S3 demonstrated significantly higher overall IQ scores than the other strengths (P < 0.05). Overall IQ and beam-hardening artifacts of S2 and S3 were significantly better than those in FBP and IRIS (P < 0.001). CONCLUSIONS S2 or S3 strengths of SAFIRE can be used practically in clinical routines and may have more potential than IRIS and FBP for LDCT with improved IQ.

Objective To retrospectively analyze computed tomography (CT) and clinical findings of patients with subcutaneous panniculitis-like T-cell lymphoma (SPTCL). Materials and methods The CT findings were retrospectively assessed in 8 patients (6 men, 2 women; age range, 23-60 years; mean age, 39.8 years) with pathologically proven SPTCL. The tumor location, number, distribution, size, and morphological characteristics on CT were evaluated, as were maximum standardized uptake values on positron emission tomography. We also evaluated patient symptoms, laboratory findings, immunophenotype, involvement of bone marrow, treatment, and outcomes. Results All 8 patients had multiple (range, 4 to numerous) soft tissue lesions involving subcutaneous fat tissue of the chest, abdominal wall, back, and buttock. Lesions varied in size (range, 0.5-10 cm) and showed reticular (n = 1), nodular (n = 4), and diffuse infiltrative (n = 3) patterns. Three patients had lesions involving the entire thickness of fat tissue, 3 had partial lesions, and 2 had variable lesions. Skin thickening was mild in 4 patients, moderate in 2, and severe in 2; fascia thickening was mild in 3 patients, moderate in one, severe in one, and variable in 2. In 7 patients, lesions were accompanied by engorged supplying vessels. At onset, maximum standardized uptake values varied from 1.2 to 4.7, decreasing to 0.0 to 4.2. Five patients had αβ type and one had γδ type. Clinical outcome varied: two remain alive with disease, two had no disease, and one died. Conclusions The SPTCL is characterized by multiple, nodular, or diffuse soft tissue lesions involving subcutaneous fat tissue, accompanied by engorged vessels and skin and fascial thickening. Patients vary in presentation and in treatment outcomes.

To compare the parenchymal attenuation change between inspiration/expiration CTs with dynamic ventilation change between xenon wash-in (WI) inspiration and wash-out (WO) expiration CTs.52 prospectively enrolled COPD patients underwent xenon ventilation dual-energy CT during WI and WO periods and pulmonary function tests (PFTs). The parenchymal attenuation parameters (emphysema index (EI), gas-trapping index (GTI) and air-trapping index (ATI)) and xenon ventilation parameters (xenon in WI (Xe-WI), xenon in WO (Xe-WO) and xenon dynamic (Xe-Dyna)) of whole lung and three divided areas (emphysema, hyperinflation and normal) were calculated on virtual non-contrast images and ventilation images. Pearson correlation, linear regression analysis and one-way ANOVA were performed.EI, GTI and ATI showed a significant correlation with Xe-WI, Xe-WO and Xe-Dyna (EI R = -.744, -.562, -.737; GTI R = -.621, -.442, -.629; ATI R = -.600, -.421, -.610, respectively, p 0.01). All CT parameters showed significant correlation with PFTs except forced vital capacity (FVC). There was a significant difference in GTI, ATI and Xe-Dyna in each lung area (p 0.01).The parenchymal attenuation change between inspiration/expiration CTs and xenon dynamic change between xenon WI- and WO-CTs correlate significantly. There are alterations in the dynamics of xenon ventilation between areas of emphysema.• The xenon ventilation change correlates with the parenchymal attenuation change. • The xenon ventilation change shows the difference between three lung areas. • The combination of attenuation and xenon can predict more accurate PFTs.

To compare the radiation dose and image quality, focused mainly on cardiac pulsation artifact, between high-pitch low-dose chest computed tomography (HP-LDCT) and standard low-dose chest CT (LDCT).One hundred patients underwent HP-LDCT (50 patients) or LDCT (50 patients). Scan parameters were the same except for the pitch and gantry rotation time: 3.0 vs. 1.2 and 0.28s vs. 0.5s, respectively. Objective image noise at five regions and subjective image quality, such as noise, artifacts, cardiac pulsation artifacts, and overall diagnostic acceptability, were evaluated using a five-point scale. The significance level for all tests was set at P0.05.The dose-length products (DLPs) with HP-LDCT and LDCT were 90.2±4.3mGycm and 103.1±6.4mGycm, respectively (P0.01). DLP of HP-LDCT showed a 13% reduction versus LDCT. Objective image noise was not significantly different. Cardiac pulsation artifacts showed a significant reduction on HP-LDCT (P0.01). Other subjective image quality parameters of HP-LDCT were similar to those of LDCT. The overall diagnostic acceptability of HP-LDCT was better than that of LDCT (P0.01).HP-LDCT showed a 13% mean radiation dose reduction with no deterioration in image quality due to cardiac pulsation artifacts.

The aim of this study is to compare the thin section computed tomography (CT) characteristics of the early local tumor recurrence with those of the stump deformity or granulation tissue after the resection of squamous cell carcinoma (SCC). Twenty-nine consecutive patients with local recurrence after definitive SCC operation from April 2006 to September 2012 were included in our study. Pre- and postoperative CT findings from these patients were retrospectively reviewed and compared with those in the age- and sex-matched 29 patients with the stump deformity or granulation tissue at stump site after definitive SCC operation, by 2 radiologists. We evaluated the initial tumor stage, tumor size, and tumor location in relation with the bronchus on preoperative CT scan. On postoperative CT scan, we evaluated the size, CT characteristics, and involvement pattern of the suspected soft tissue around the stump site, and the distance between surgical staples and soft tissue at the stump site. Tumor stage, tumor size, and tumor location in relation with the bronchus on preoperative CT scan were not significantly different between 2 groups, while lymph node stage was more advanced in the local recurrence group. On postoperative CT scan, the size of suspected soft tissue at stump site is significantly larger, and the distance between stump staples and suspected soft tissue was significantly longer in the local recurrence group than control group (median; 19 mm and 3 mm; 18 mm and 0 mm, respectively, P

Methods Twenty nine consecutive patients with local recurrence after definitive SCC operation from April 2006 to September 2012 were included. Preand post-operative CT from these patients were retrospectively reviewed and compared with those in ageand gender-matched 29 patients with stump deformity or granulation tissue at stump site after the definitive SCC operation, by two chest radiologists.

OBJECTIVES To compare a new integral-based half-band method (IBHB) and a conventional full-width half-maximum (FWHM) method in measuring peripheral airway dimensions at airway phantoms and thin-section computed tomography of chronic obstructive pulmonary disease (COPD). METHODS The IBHB was validated and compared using airway phantoms and 50 patients with COPD. Airway parameters (wall area percentage [WA%], mean lumen radius, and mean wall thickness) were measured at fourth to sixth generations of the right apical bronchus. Matched results from 2 methods were compared and correlated with forced expiratory volume (FEV) in 1 second (FEV1), FEV1 / forced vital capacity (FVC), and global initiative for chronic obstructive lung disease (GOLD) stage. Linear regression analysis was performed using airway dimensions and emphysema index. RESULTS The IBHB generated more accurate measurements at phantom study. Measured airway parameters by both methods at thin-section computed tomography study were significantly different (all P < 0.05, paired t test). The IBHB method-measured WA% and wall thickness were significantly smaller. Mean WA% with IBHB also showed better correlation than that with FWHM (FEV1, r = -0.52 vs -0.28; FEV1 / FVC, r = -0.41 vs r = -0.20; GOLD, 0.52 vs 0.33, respectively). Linear regression analysis revealed fifth-generation WA% measured by IBHB was an independent variable, and addition to emphysema index increased predictability (FEV1, r = 0.63; FEV1 / FVC, r = 0.61; GOLD, r = 0.70). CONCLUSIONS The new IBHB measured peripheral airway dimensions differently than FWHM and showed better correlations with functional parameters in COPD.

To study the differences in computed tomographic (CT) characteristics between patients with advanced lung adenocarcinoma who have anaplastic lymphoma kinase (ALK) gene rearrangement and those who have epidermal growth factor receptor (EGFR) mutations.This retrospective study was approved by the institutional review board. Informed consent was waived. Patients with stage IV adenocarcinoma (n = 198) were enrolled from November 2004 to December 2013, including 68 patients with ALK rearrangement and 130 with EGFR mutation. Two independent radiologists evaluated the main tumor in each patient and determined its size, type, margins, lymph node metastasis, and intrathoracic metastasis (lung, pleural or pericardial, or bone). A multiple logistic regression model was applied to discriminate clinical and CT characteristics between the types of mutation.The κ index for assessment of tumor and node stage between radiologists was 0.8530 to 0.9388. Most of the main tumors in patients with both types of mutation appeared as solid masses. In univariate analysis, patients with an ALK rearrangement were younger (P.001) and were more likely to be men (P = .001), to have never smoked (P = .002), and to have pleural or pericardial metastases (P.05) compared with those with EGFR mutations. In multivariate analysis, lobulated margins (odds ratio, 4.815; 95% confidence interval [CI]: 1.789, 12.961; P = .002), N2 or N3 lymph node involvement (odds ratio, 2.445; 95% CI: 1.005, 5.950; P = .049), and lymphangitic lung metastasis (odds ratio, 8.485; 95% CI: 2.238, 32.170; P = .002) were more common in patients with ALK rearrangement than in those with EGFR mutation. The area under the receiver operating characteristic curve was 0.855.Adenocarcinomas with ALK rearrangement appeared as solid masses with lobulated margins at CT and were more likely to be associated with lymphangitic metastasis, advanced lymph node metastasis, and pleural or pericardial metastasis than were tumors with EGFR mutations.

One objective was to evaluate the air trapping index (ATI), measured by inspiration/expiration CT, in COPD patients and nonsmokers. Another objective was to assess the association between the pulmonary function test (PFT) and CT parameters such as ATI or other indices, separately in the whole lung, in emphysema, and in hyperinflated and normal lung areas. One hundred and thirty-eight COPD patients and 29 nonsmokers were included in our study. The ATI, the emphysema index (EI), the gas trapping index (Exp -856) and expiration/inspiration ratio of mean lung density (E/Iratio of MLD) were measured on CT. The values of the whole lung, of emphysema, and of hyperinflated and normal lung areas were compared and then correlated with various PFT parameters. Compared with nonsmokers, COPD patients showed a higher ATI in the whole lung and in each lung lesion (all P

We conducted a retrospective analysis to evaluate the diagnostic outcomes of CT-guided aspiration and core biopsy of 305 pulmonary nodules measuring less than 1 cm.We determined the diagnostic yield of using CT-guided aspiration and core biopsy to analyze 305 lesions in 290 patients. Diagnostic performance was evaluated according to the biopsy method, including aspiration alone, core biopsy alone, and combination use, and the consistency of the nodule, including solid, partly solid ground-glass opacity (GGO), and pure GGO. Final diagnoses were established in 268 of the 305 lesions (87.9%). Nondiagnostic biopsy results were obtained for 27 of the 268 lesions (10.1%).The overall sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of malignancy were 93.1% (148 of 159 lesions), 98.8% (81/82), 99.3% (148/149), and 88.0% (81/92), respectively; diagnostic accuracy was 95.0% (229/241). Using multivariate logistic regression analysis, we found that aspiration alone was a significant independent risk factor associated with diagnostic failure (odds ratio, 3.199; p = 0.001).The use of CT-guided aspiration and core biopsy resulted in a high diagnostic yield for pulmonary nodules smaller than 1 cm. The use of the aspiration method alone was an independent risk factor associated with diagnostic failure.

Pulmonary emphysema is a pathologic condition characterized by permanently enlarged airspaces distal to the terminal bronchiole with destruction of the alveolar walls. Functional information of the lungs is important to understand the pathophysiology of emphysema and that of chronic obstructive pulmonary disease. With the recent developments in magnetic resonance imaging (MRI) techniques, functional MRI with variable MR sequences can be used for the evaluation of different physiological and anatomic changes seen in cases of pulmonary emphysema. In this review article, we will focus on a brief description of each method, results of some of the most recent work, and the clinical application of such knowledge.