Perspective on Management of Low-Dose Computed Tomography Findings on Low-Dose Computed Tomography Examinations for Lung Cancer Screening. From the International Association for the Study of Lung Cancer Early Detection and Screening Committee

Lung cancer screening using low-dose computed tomography (LDCT) carefully implemented has been found to reduce deaths from lung cancer. Optimal management starts with selection of eligibility criteria, counseling of screenees, smoking cessation, selection of the regimen of screening which specifies the imaging protocol, and workup of LDCT findings. Coordination of clinical, radiologic, and interventional teams and ultimately treatment of diagnosed lung cancers under screening determine the benefit of LDCT screening. Ethical considerations of who should be eligible for LDCT screening programs are important to provide the benefit to as many people at risk of lung cancer as possible. Unanticipated diseases identified on LDCT may offer important benefits through early detection of leading global causes of death, such as cardiovascular diseases and chronic obstructive pulmonary disease, as the latter may result from conditions such as emphysema and bronchiectasis, which can be identified early on LDCT. This report identifies the key components of the regimen of LDCT screening for lung cancer which include the need for a management system to provide data for continuous updating of the regimen and provides quality assurance assessment of actual screenings. Multidisciplinary clinical management is needed to maximize the benefit of early detection, diagnosis, and treatment of lung cancer. Different regimens have been evolving throughout the world as the resources and needs may be different, for countries with limited resources. Sharing of results, further knowledge, and incorporation of technologic advances will continue to accelerate worldwide improvements in the diagnostic and treatment approaches.

ACR Lung-RADS v2022: Assessment Categories and Management Recommendations

The ACR created the Lung CT Screening Reporting and Data System (Lung-RADS) in 2014 to standardize the reporting and management of screen-detected pulmonary nodules. Lung-RADS was updated to version 1.1 in 2019 and revised size thresholds for nonsolid nodules, added classification criteria for perifissural nodules, and allowed for short-interval follow-up of rapidly enlarging nodules that may be infectious in etiology. Lung-RADS v2022, released in November 2022, provides several updates including guidance on the classification and management of atypical pulmonary cysts, juxtapleural nodules, airway-centered nodules, and potentially infectious findings. This new release also provides clarification for determining nodule growth and introduces stepped management for nodules that are stable or decreasing in size. This article summarizes the current evidence and expert consensus supporting Lung-RADS v2022.

ACR Lung-RADS v2022: Assessment Categories and Management Recommendations

The American College of Radiology created the Lung CT Screening Reporting and Data System (Lung-RADS) in 2014 to standardize the reporting and management of screen-detected pulmonary nodules. Lung-RADS was updated to version 1.1 in 2019 and revised size thresholds for nonsolid nodules, added classification criteria for perifissural nodules, and allowed for short-interval follow-up of rapidly enlarging nodules that may be infectious in etiology. Lung-RADS v2022, released in November 2022, provides several updates including guidance on the classification and management of atypical pulmonary cysts, juxtapleural nodules, airway-centered nodules, and potentially infectious findings. This new release also provides clarification for determining nodule growth and introduces stepped management for nodules that are stable or decreasing in size. This article summarizes the current evidence and expert consensus supporting Lung-RADS v2022.

Risk factors for lung function decline in systemic sclerosis-associated interstitial lung disease in a large single-centre cohort

OBJECTIVES

The aim of this study was to identify risk factors of percent predicted forced vital capacity (ppFVC) decline in patients with SSc-associated interstitial lung disease (SSc-ILD).

METHODS

We identified 484 patients with SSc who had HRCT Chest, of which 312 with ILD. Those with serial pulmonary function tests were included in a longitudinal analysis (n = 184). Linear mixed effect models were fitted to assess the decline in ppFVC over time, and to explore the effect of demographics and baseline characteristics on ppFVC decline.

RESULTS

The majority of SSc-ILD patients were female (76.3%) and 51.3% had diffuse cutaneous subset. The mean (s.d.) age was 53.6 (12.7) years, median disease duration since first non-RP symptoms was 2.6 years, and 48.4% of the patients had ILD extent >20% on HRCT. In the univariate analysis, longer disease duration (>2.37 years), ILD extent >20%, and anti-topoisomerase I (ATA) positivity were significantly associated with ppFVC decline. In the multivariate analysis, the only statistically significant variable associated with ppFVC decline was ATA positivity. The overall group's mean decline in ppFVC was -0.28% (P-value 0.029), with -0.13% (n = 163) in those who were alive and -8.28% (P-value 0.0002 for the change in ppFVC trajectory) in patients who died within 2 years.

CONCLUSION

Our study confirms that ppFVC is a marker of survival in SSc-ILD, supporting its use for risk stratification to identify patients who may benefit from earlier interventions and treatment. Our study also supports the role of ATA positivity as a predictive marker for ppFVC decline in this population.

Utility of Nipple Markers in the Era of Digital Imaging

PURPOSE

Nipple markers maybe used to decrease the recall of patients undergoing chest radiography by aiding in distinguishing between a nipple shadow and lung nodule. We evaluated the use of digital chest radiographs in clinical practice including accuracy of placement and markers that do not contribute to interpretation (ie, projected outside the lung fields). We also evaluated the recall rate for additional imaging in patients who received nipple markers compared to those who did not.

MATERIAL AND METHODS

In this Institutional Review Board approved retrospective study, 1000 consecutive outpatient frontal and lateral chest radiographs performed in 2018 for which nipple markers were provided to patients formed the study group. Three cardiothoracic radiologists evaluated the images for the presence of markers and accuracy of placement. The recall rate was calculated over a 3-year period from March 21, 2016 and March 21, 2019.

RESULTS

One or both markers were missing without an explanation (such as mastectomy), misplaced or outside the lung fields in 57.8% (578/1000) of studies. The 3-year recall rate for all chest radiographs was very low (0.03%; 42/135,792) and was lower for patients provided nipple markers (0.007%; 5/62,587) than those who were not (0.05%; 37/73,205) ( P <0.001).

CONCLUSIONS

The low overall recall rate and high prevalence of inaccurate marker placement or markers that do not contribute to interpretation (ie, outside the lung fields) does not justify the routine use of nipple markers for chest radiography.

POS0902 RISK FACTORS FOR LUNG FUNCTION DECLINE IN SYSTEMIC SCLEROSIS INTERSTITIAL LUNG DISEASE IN A LARGE SINGLE-CENTER COHORT

Background

Systemic sclerosis associated interstitial lung disease (SSc-ILD) is the leading cause of scleroderma-related mortality.

Objectives

This work identifies factors associated with SSc-ILD decline on pulmonary function testing (PFT).

Methods

This single center cohort identified 312 patients with ILD as determined by high resolution chest. 184 patients (59% of 312) completed baseline and serial PFTs (with at least two follow-up PFTs) and were included in this analysis. Mixed linear models were fit to assess the decline in the percent predicted forced vital capacity (ppFVC) over time. Demographics, disease factors, autoantibodies, and ILD features were included in the univariate mixed linear model; those achieving a p-value <0.20 were included in the multivariable mixed linear model. Patients were followed longitudinally, with survival as an endpoint identified using the National Death Registry Index, reviewing death certificates, and hospital records.

Results

The 184 patients were an average of 53.2 [12.1] years old; the median [IQR] disease duration from the first non-Raynaud’s phenomenon symptom was 1.8 [0.7, 4.8] years. SSc subtype was diffuse in 55.4% (n=102), limited in 32.6% (n=60), overlap syndrome in 8.2% (n=15), and SSc sine scleroderma in 3.87% (n=7). Serologies were positive for anti-topoisomerase I (ATA), anti-centromere and anti-RNA polymerase III in 31.4% (n=53/169), 10.4% (16/154) and 22.9% (25/109) respectively. Mean ppFVC was 70.8 (18.9) and ppDLco 57.2 (20.8). Whole lung involvement (WLI%) of ≥20% on visual read was found in 49.3% of subjects (74/150 (49.3%)) where quantification was available. Over a median of 4.9 (2.4, 6.8) years, 21 patients (11.4%) died. The ppFVC declined a mean of 0.28/year in the overall group. There were differences in terms of ppFVC decline/year between patients who died in the first 2 years (n=10, -8.28%), 2-8 years (n=5, -3.89%), after 8 years (n=6, -1.00%), or who were still alive (n=163, -0.13%). The primary cause of death was ILD (6/21, 28.6%); those who died in the first 2 years most often died from progressive ILD (4/6, 67%). Factors significantly associated with decline in ppFVC on univariate analyses, included longer disease duration (ref. < median, P=0.0048), ATA positivity (ref. negative, P=0.0081), and WLI ≥20% (ref. 0-20%, P=0.0484). In multivariate analysis the only statistically significant variable associated with decline in ppFVC/ year was ATA positivity.

Conclusion

In a large single center cohort of SSc-ILD, ATA positivity is a risk factor for developing progressive SSc-ILD, consistent with other SSc-ILD cohorts. Stratifying patients by survival demonstrates that lung function declines dramatically in those who died within 2 years, whose main cause of death was progressive ILD. These data support the growing need to identify risk factors for disease severity and risk for progression, and to target intervention in patients most likely to develop progressive SSc-ILD1,2.

References

[1]Roofeh D, Lin CJF, Goldin JG, et al. Tocilizumab Prevents Progression of Early Systemic Sclerosis Associated Interstitial Lung Disease. Arthritis Rheum. 2021

[2]Roofeh D, Lescoat A, Khanna D. Treatment for systemic sclerosis-associated interstitial lung disease. Curr Opin Rheumatol. 2021

Disclosure of Interests

None declared

Combining chest X-rays and electronic health record (EHR) data using machine learning to diagnose acute respiratory failure

OBJECTIVE

When patients develop acute respiratory failure (ARF), accurately identifying the underlying etiology is essential for determining the best treatment. However, differentiating between common medical diagnoses can be challenging in clinical practice. Machine learning models could improve medical diagnosis by aiding in the diagnostic evaluation of these patients.

MATERIALS AND METHODS

Machine learning models were trained to predict the common causes of ARF (pneumonia, heart failure, and/or chronic obstructive pulmonary disease [COPD]). Models were trained using chest radiographs and clinical data from the electronic health record (EHR) and applied to an internal and external cohort.

RESULTS

The internal cohort of 1618 patients included 508 (31%) with pneumonia, 363 (22%) with heart failure, and 137 (8%) with COPD based on physician chart review. A model combining chest radiographs and EHR data outperformed models based on each modality alone. Models had similar or better performance compared to a randomly selected physician reviewer. For pneumonia, the combined model area under the receiver operating characteristic curve (AUROC) was 0.79 (0.77-0.79), image model AUROC was 0.74 (0.72-0.75), and EHR model AUROC was 0.74 (0.70-0.76). For heart failure, combined: 0.83 (0.77-0.84), image: 0.80 (0.71-0.81), and EHR: 0.79 (0.75-0.82). For COPD, combined: AUROC = 0.88 (0.83-0.91), image: 0.83 (0.77-0.89), and EHR: 0.80 (0.76-0.84). In the external cohort, performance was consistent for heart failure and increased for COPD, but declined slightly for pneumonia.

CONCLUSIONS

Machine learning models combining chest radiographs and EHR data can accurately differentiate between common causes of ARF. Further work is needed to determine how these models could act as a diagnostic aid to clinicians in clinical settings.

Screening for Lung Cancer in Individuals Who Never Smoked: An International Association for the Study of Lung Cancer Early Detection and Screening Committee Report

Screening with low-dose computed tomography of high-risk individuals with a smoking history reduces lung cancer mortality. Current screening guidelines and eligibility criteria can miss more than 50% of lung cancers, and in some geographic areas, such as East Asia, a large proportion of the missed lung cancers are in never-smokers. Although randomized trials revealed the benefits of screening for people who smoke, these trials generally excluded never-smokers. Thus, the feasibility and effectiveness of lung cancer screening of individuals who never smoked are uncertain. Several known and suspected risk factors for lung cancers in never-smokers such as exposure to secondhand smoke, occupational carcinogens, radon, air pollution, and pulmonary diseases, such as chronic obstructive pulmonary disease and interstitial lung diseases, and intrinsic factors, such as age, are well noted. In this regard, knowledge of risk factors may make possible quantification and prediction of lung cancer risk in never smokers. It is worth considering if and how never smokers could be included in population-based screening programs. As the implementation of these programs is challenging in many countries owing to multiple factors and the epidemiologic differences by global regions, these issues will need to be evaluated in each country taking into account various factors, including accuracy of risk assessment and cost-effectiveness of screening in never smokers. This report aims to outline current knowledge on risk factors for lung cancer in never smokers to propose research strategies for this topic and initiate a broader discussion on lung cancer screening of never smokers. Similar considerations can be made in current and ex-smokers, which do not fulfill the current screening inclusion criteria, but otherwise are at increased risk. Although screening of never smokers may in the future be effectively conducted, current evidence to support widespread implementation of this practice is lacking.

A controlled statistical study to assess measurement variability as a function of test object position and configuration for automated surveillance in a multicenter longitudinal COPD study (SPIROMICS)

PURPOSE

A test object (phantom) is an important tool to evaluate comparability and stability of CT scanners used in multicenter and longitudinal studies. However, there are many sources of error that can interfere with the test object-derived quantitative measurements. Here the authors investigated three major possible sources of operator error in the use of a test object employed to assess pulmonary density-related as well as airway-related metrics.

METHODS

Two kinds of experiments were carried out to assess measurement variability caused by imperfect scanning status. The first one consisted of three experiments. A COPDGene test object was scanned using a dual source multidetector computed tomographic scanner (Siemens Somatom Flash) with the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) inspiration protocol (120 kV, 110 mAs, pitch = 1, slice thickness = 0.75 mm, slice spacing = 0.5 mm) to evaluate the effects of tilt angle, water bottle offset, and air bubble size. After analysis of these results, a guideline was reached in order to achieve more reliable results for this test object. Next the authors applied the above findings to 2272 test object scans collected over 4 years as part of the SPIROMICS study. The authors compared changes of the data consistency before and after excluding the scans that failed to pass the guideline.

RESULTS

This study established the following limits for the test object: tilt index ≤0.3, water bottle offset limits of [-6.6 mm, 7.4 mm], and no air bubble within the water bottle, where tilt index is a measure incorporating two tilt angles around x- and y-axis. With 95% confidence, the density measurement variation for all five interested materials in the test object (acrylic, water, lung, inside air, and outside air) resulting from all three error sources can be limited to ±0.9 HU (summed in quadrature), when all the requirements are satisfied. The authors applied these criteria to 2272 SPIROMICS scans and demonstrated a significant reduction in measurement variation associated with the test object.

CONCLUSIONS

Three operator errors were identified which significantly affected the usability of the acquired scan images of the test object used for monitoring scanner stability in a multicenter study. The authors' results demonstrated that at the time of test object scan receipt at a radiology core laboratory, quality control procedures should include an assessment of tilt index, water bottle offset, and air bubble size within the water bottle. Application of this methodology to 2272 SPIROMICS scans indicated that their findings were not limited to the scanner make and model used for the initial test but was generalizable to both Siemens and GE scanners which comprise the scanner types used within the SPIROMICS study.

Utility and Associated Risk of Pulmonary Embolism Computed Tomography Scans in the Michigan Lupus Cohort

OBJECTIVE

Systemic lupus erythematosus patients are frequently evaluated for chest pain and may have multiple pulmonary embolism (PE) computed tomography (CT) scans. This study was undertaken to determine the incidence of pulmonary embolism in the University of Michigan Lupus Cohort patients who have undergone PE CT scans and to estimate the associated increased risk of breast and lung cancer from radiation exposure.

METHODS

We reviewed records of patients in the University of Michigan Lupus Cohort (n = 854) and determined the number and outcome of PE CT scans. Radimetrics software was used to perform individualized calculations of radiation dose to the lung and breast of each patient. We used this dose information, the patient's age at the time of scan, and risks according to the Biological Effects of Ionizing Radiation, report VII, to estimate the increased incidence risks of breast and lung cancer.

RESULTS

A total of 182 of 856 patients (21%) underwent 357 PE CT scans. The overall rate of positivity was 7.5%. For patients undergoing their first through third scans, the rate of positivity for PE was 8.8%, whereas patients undergoing their fourth through tenth scans had 1.6% positivity. The highest increase in incidence risk was 0.87% for breast and 0.62% for lung.

CONCLUSION

Patients with multiple previous PE CT scans had lower likelihood of a positive result on subsequent scans and higher risks of malignancy. The magnitude of risk should not discourage performance of PE CT when clinically indicated.

Lung cancer screening, version 1.2015: featured updates to the NCCN guidelines

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Lung Cancer Screening provide recommendations for selecting individuals for lung cancer screening, and for evaluation and follow-up of nodules found during screening, and are intended to assist with clinical and shared decision-making. These NCCN Guidelines Insights focus on the major updates to the 2015 NCCN Guidelines for Lung Cancer Screening, which include a revision to the recommendation from category 2B to 2A for one of the high-risk groups eligible for lung cancer screening. For low-dose CT of the lung, the recommended slice width was revised in the table on "Low-Dose Computed Tomography Acquisition, Storage, Interpretation, and Nodule Reporting."

Performance of Lung-RADS in the National Lung Screening Trial: a retrospective assessment

BACKGROUND

Lung cancer screening with low-dose computed tomography (LDCT) has been recommended, based primarily on the results of the NLST (National Lung Screening Trial). The American College of Radiology recently released Lung-RADS, a classification system for LDCT lung cancer screening.

OBJECTIVE

To retrospectively apply the Lung-RADS criteria to the NLST.

DESIGN

Secondary analysis of a group from a randomized trial.

SETTING

33 U.S. screening centers.

PATIENTS

Participants were randomly assigned to the LDCT group of the NLST, were aged 55 to 74 years, had at least a 30-pack-year history of smoking, and were current smokers or had quit within the past 15 years.

INTERVENTION

3 annual LDCT lung cancer screenings.

MEASUREMENTS

Lung-RADS classifications for LDCT screenings. Lung-RADS categories 1 to 2 constitute negative screening results, and categories 3 to 4 constitute positive results.

RESULTS

Of 26 722 LDCT group participants, 26 455 received a baseline screening; 48 671 screenings were done after baseline. At baseline, the false-positive result rate (1 minus the specificity rate) for Lung-RADS was 12.8% (95% CI, 12.4% to 13.2%) versus 26.6% (CI, 26.1% to 27.1%) for the NLST; after baseline, the false-positive result rate was 5.3% (CI, 5.1% to 5.5%) for Lung-RADS versus 21.8% (CI, 21.4% to 22.2%) for the NLST. Baseline sensitivity was 84.9% (CI, 80.8% to 89.0%) for Lung-RADS versus 93.5% (CI, 90.7% to 96.3%) for the NLST, and sensitivity after baseline was 78.6% (CI, 74.6% to 82.6%) for Lung-RADS versus 93.8% (CI, 91.4% to 96.1%) for the NLST.

LIMITATION

Lung-RADS criteria were applied retrospectively.

CONCLUSION

Lung-RADS may substantially reduce the false-positive result rate; however, sensitivity is also decreased. The effect of using Lung-RADS criteria in clinical practice must be carefully studied.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Computerized detection of noncalcified plaques in coronary CT angiography: evaluation of topological soft gradient prescreening method and luminal analysis

PURPOSE

The buildup of noncalcified plaques (NCPs) that are vulnerable to rupture in coronary arteries is a risk for myocardial infarction. Interpretation of coronary CT angiography (cCTA) to search for NCP is a challenging task for radiologists due to the low CT number of NCP, the large number of coronary arteries, and multiple phase CT acquisition. The authors conducted a preliminary study to develop machine learning method for automated detection of NCPs in cCTA.

METHODS

With IRB approval, a data set of 83 ECG-gated contrast enhanced cCTA scans with 120 NCPs was collected retrospectively from patient files. A multiscale coronary artery response and rolling balloon region growing (MSCAR-RBG) method was applied to each cCTA volume to extract the coronary arterial trees. Each extracted vessel was reformatted to a straightened volume composed of cCTA slices perpendicular to the vessel centerline. A topological soft-gradient (TSG) detection method was developed to prescreen for NCP candidates by analyzing the 2D topological features of the radial gradient field surface along the vessel wall. The NCP candidates were then characterized by a luminal analysis that used 3D geometric features to quantify the shape information and gray-level features to evaluate the density of the NCP candidates. With machine learning techniques, useful features were identified and combined into an NCP score to differentiate true NCPs from false positives (FPs). To evaluate the effectiveness of the image analysis methods, the authors performed tenfold cross-validation with the available data set. Receiver operating characteristic (ROC) analysis was used to assess the classification performance of individual features and the NCP score. The overall detection performance was estimated by free response ROC (FROC) analysis.

RESULTS

With our TSG prescreening method, a prescreening sensitivity of 92.5% (111/120) was achieved with a total of 1181 FPs (14.2 FPs/scan). On average, six features were selected during the tenfold cross-validation training. The average area under the ROC curve (AUC) value for training was 0.87 ± 0.01 and the AUC value for validation was 0.85 ± 0.01. Using the NCP score, FROC analysis of the validation set showed that the FP rates were reduced to 3.16, 1.90, and 1.39 FPs/scan at sensitivities of 90%, 80%, and 70%, respectively.

CONCLUSIONS

The topological soft-gradient prescreening method in combination with the luminal analysis for FP reduction was effective for detection of NCPs in cCTA, including NCPs causing positive or negative vessel remodeling. The accuracy of vessel segmentation, tracking, and centerline identification has a strong impact on NCP detection. Studies are underway to further improve these techniques and reduce the FPs of the CADe system.

Coronary CT angiography (cCTA): automated registration of coronary arterial trees from multiple phases

Coronary computed tomography angiography (cCTA) is a commonly used imaging modality for the evaluation of coronary artery disease. cCTA is generally reconstructed in multiple cardiac phases because different coronary arteries may be better visualized in some phases than in others due to the periodic cardiac motion. We are developing an automated registration method for coronary arterial trees from multiple-phase cCTA that has potential application in building a 'best-quality' tree to facilitate image analysis and detection of stenotic plaques. Given the segmented left or right coronary arterial (LCA or RCA) trees from the multiple phases as input, the adjacent phase pairs, where displacements are relatively small, are registered by a specifically designed method based on a cubic B-spline with fast localized optimization (CBSO). For the phase pairs with large displacements, a global registration using an affine transform with quadratic terms and nonlinear simplex optimization (AQSO) is followed by a local registration using CBSO to refine the AQSO registered volumes. 26 LCA and 26 RCA trees with six cCTA phases from 26 patients were used for registration evaluation. The average distances for the tree pairs between the adjacent phases with small displacements before and after CBSO registration were 0.96  ±  0.79 and 0.76  ±  0.61 mm respectively for LCA, and 0.93  ±  0.97 and 0.64  ±  0.43 mm, respectively for RCA. The average distance differences before and after registration were statistically significant (p < 0.001) for both LCA and RCA trees. The average distances for the distant phases with large displacements before registration, after AQSO registration, and finally after the CBSO registration were 2.85  ±  1.46, 1.62  ±  0.76, and 0.97  ±  0.43 mm, respectively for LCA, and 4.03  ±  2.36, 2.18  ±  1.11, and 0.97  ±  0.44 mm, respectively for RCA. The average distance differences between every two consecutive stages of registration were statistically significant. The corresponding phases of LCA and RCA trees were aligned to an average of less than 1 mm, providing a basis for a best-quality tree construction.

Smoking-related idiopathic interstitial pneumonia

Cigarette smoking is a key factor in the development of numerous pulmonary diseases. An international group of clinicians, radiologists and pathologists evaluated patients with previously identified idiopathic interstitial pneumonia (IIP) to determine unique features of cigarette smoking. Phase 1 (derivation group) identified smoking-related features in patients with a history of smoking (n=41). Phase 2 (validation group) determined if these features correctly predicted the smoking status of IIP patients (n=100) to participants blinded to smoking history. Finally, the investigators sought to determine if a new smoking-related interstitial lung disease phenotype could be defined. Phase 1 suggested that preserved forced vital capacity with disproportionately reduced diffusing capacity of the lung for carbon monoxide, and various radiographic and histopathological findings were smoking-related features. In phase 2, the kappa coefficient among clinicians was 0.16 (95% CI 0.11-0.21), among the pathologists 0.36 (95% CI 0.32-0.40) and among the radiologists 0.43 (95% CI 0.35-0.52) for smoking-related features. Eight of the 100 cases were felt to represent a potential smoking-related interstitial lung disease. Smoking-related features of interstitial lung disease were identified in a minority of smokers and were not specific for smoking. This study is limited by its retrospective design, the potential for recall bias in smoking history and lack of information on second-hand smoke exposure. Further research is needed to understand the relationship between smoking and interstitial lung disease.

National lung screening trial: variability in nodule detection rates in chest CT studies

PURPOSE

To characterize the variability in radiologists' interpretations of computed tomography (CT) studies in the National Lung Screening Trial (NLST) (including assessment of false-positive rates [FPRs] and sensitivity), to examine factors that contribute to variability, and to evaluate trade-offs between FPRs and sensitivity among different groups of radiologists.

MATERIALS AND METHODS

The HIPAA-compliant NLST was approved by the institutional review board at each screening center; all participants provided informed consent. NLST radiologists reported overall screening results, nodule-specific findings, and recommendations for diagnostic follow-up. A noncalcified nodule of 4 mm or larger constituted a positive screening result. The FPR was defined as the rate of positive screening examinations in participants without a cancer diagnosis within 1 year. Descriptive analyses and mixed-effects models were utilized. The average odds ratio (OR) for a false-positive result across all pairs of radiologists was used as a measure of variability.

RESULTS

One hundred twelve radiologists at 32 screening centers each interpreted 100 or more NLST CT studies, interpreting 72 160 of 75 126 total NLST CT studies in aggregate. The mean FPR for radiologists was 28.7% ± 13.7 (standard deviation), with a range of 3.8%-69.0%. The model yielded an average OR of 2.49 across all pairs of radiologists and an OR of 1.83 for pairs within the same screening center. Mean FPRs were similar for academic versus nonacademic centers (27.9% and 26.7%, respectively) and for centers inside (25.0%) versus outside (28.7%) the U.S. "histoplasmosis belt." Aggregate sensitivity was 96.5% for radiologists with FPRs higher than the median (27.1%), compared with 91.9% for those with FPRs lower than the median (P = .02).

CONCLUSION

There was substantial variability in radiologists' FPRs. Higher FPRs were associated with modestly higher sensitivity.

Prevalence and clinical correlates of bronchoreversibility in severe emphysema

Chronic obstructive pulmonary disease (COPD) exhibits airflow obstruction that is not fully reversible. The importance of bronchoreversibility remains controversial. We hypothesised that an emphysematous phenotype of COPD would be associated with decreased bronchoreversibility. 544 patients randomised to the medical arm of the National Emphysema Treatment Trial formed the study group. Participants underwent multiple measurements of bronchoreversibility on a mean of four sessions over 1.91 yrs. They were also characterised by measures of symptoms, quality of life and quantitative measures of emphysema by computed tomography. Mean baseline forced expiratory volume in 1 s (FEV(1)) in this patient population is 24% predicted. 22.2% of patients demonstrated bronchoreversibility on one or more occasions using American Thoracic Society/European Respiratory Society criteria. Few patients (0.37%) had bronchoreversibility on all completed tests. Patients who demonstrated bronchoreversibility were more likely to be male, and have better lung function and less emphysema. 64% of patients demonstrated large (> or =400 mL) changes in forced vital capacity (FVC). In a severe emphysema population, bronchoreversibility as defined by change in FEV(1) is infrequent, varies over time, and is more common in males and those with less severe emphysema. Improvements in FVC, however, were demonstrated in the majority of patients.

Computer-aided diagnosis of pulmonary nodules on CT scans: improvement of classification performance with nodule surface features

The purpose of this work is to develop a computer-aided diagnosis (CAD) system to differentiate malignant and benign lung nodules on CT scans. A fully automated system was designed to segment the nodule from its surrounding structured background in a local volume of interest (VOI) and to extract image features for classification. Image segmentation was performed with a 3D active contour method. The initial contour was obtained as the boundary of a binary object generated by k-means clustering within the VOI and smoothed by morphological opening. A data set of 256 lung nodules (124 malignant and 132 benign) from 152 patients was used in this study. In addition to morphological and texture features, the authors designed new nodule surface features to characterize the lung nodule surface smoothness and shape irregularity. The effects of two demographic features, age and gender, as adjunct to the image features were also investigated. A linear discriminant analysis (LDA) classifier built with features from stepwise feature selection was trained using simplex optimization to select the most effective features. A two-loop leave-one-out resampling scheme was developed to reduce the optimistic bias in estimating the test performance of the CAD system. The area under the receiver operating characteristic curve, A(z), for the test cases improved significantly (p < 0.05) from 0.821 +/- 0.026 to 0.857 +/- 0.023 when the newly developed image features were included with the original morphological and texture features. A similar experiment performed on the data set restricted to primary cancers and benign nodules, excluding the metastatic cancers, also resulted in an improved test A(z), though the improvement did not reach statistical significance (p = 0.07). The two demographic features did not significantly affect the performance of the CAD system (p > 0.05) when they were added to the feature space containing the morphological, texture, and new gradient field and radius features. To investigate if a support vector machine (SVM) classifier can achieve improved performance over the LDA classifier, we compared the performance of the LDA and SVMs with various kernels and parameters. Principal component analysis was used to reduce the dimensionality of the feature space for both the LDA and the SVM classifiers. When the number of selected principal components was varied, the highest test A(z) among the SVMs of various kernels and parameters was slightly higher than that of the LDA in one-loop leave-one-case-out resampling. However, no SVM with fixed architecture consistently performed better than the LDA in the range of principal components selected. This study demonstrated that the authors' proposed segmentation and feature extraction techniques are promising for classifying lung nodules on CT images.

Sex differences in severe pulmonary emphysema

RATIONALE

Limited data on sex differences in advanced COPD are available.

OBJECTIVES

To compare male and female emphysema patients with severe disease.

METHODS

One thousand fifty-three patients (38.8% female) evaluated for lung volume reduction surgery as part of the National Emphysema Treatment Trial were analyzed.

MEASUREMENTS AND MAIN RESULTS

Detailed clinical, physiological, and radiological assessment, including quantitation of emphysema severity and distribution from helical chest computed tomography, was completed. In a subgroup (n = 101), airway size and thickness was determined by histological analyses of resected tissue. Women were younger and exhibited a lower body mass index (BMI), shorter smoking history, less severe airflow obstruction, lower Dl(co) and arterial Po(2), higher arterial Pco(2), shorter six-minute walk distance, and lower maximal wattage during oxygen-supplemented cycle ergometry. For a given FEV(1)% predicted, age, number of pack-years, and proportion of emphysema, women experienced greater dyspnea, higher modified BODE, more depression, lower SF-36 mental component score, and lower quality of well-being. Overall emphysema was less severe in women, with the difference from men most evident in the outer peel of the lung. Females had thicker small airway walls relative to luminal perimeters.

CONCLUSIONS

In patients with severe COPD, women, relative to men, exhibit anatomically smaller airway lumens with disproportionately thicker airway walls, and emphysema that is less extensive and characterized by smaller hole size and less peripheral involvement.

Effect of left atrial circumferential ablation for atrial fibrillation on left atrial transport function

BACKGROUND

The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described.

OBJECTIVES

The purpose of this study was to determine the effect of LA circumferential ablation on LA function.

METHODS

Gated, multiphase, dynamic contrast-enhanced computed tomographic (CT) scans of the chest with three-dimensional reconstructions of the heart were used to calculate the LA ejection fraction (EF) in 36 patients with paroxysmal (n = 27) or chronic (n = 9) AF (mean age 55 +/- 11 years) and in 10 control subjects with no history of AF. Because CT scans had to be acquired during sinus rhythm, a CT scan was available both before and after (mean 5 +/- 1 months) LA circumferential ablation (LACA) in only 10 patients. A single CT scan was acquired in 8 patients before and in 18 patients after LACA ablation. Radiofrequency catheter ablation was performed using an 8-mm-tip catheter to encircle the pulmonary veins, with additional lines along the mitral isthmus and the roof.

RESULTS

In patients with paroxysmal AF, LA EF was lower after than before LACA (21% +/- 8% vs 32 +/- 13%, P = .003). LA EF after LA catheter ablation was similar among patients with paroxysmal AF and those with chronic AF (21% +/- 8% vs 23 +/- 13%, P = .7). However, LA EF after LA catheter ablation was lower in all patients with AF than in control subjects (21% +/- 10% vs 47% +/- 5%, P < .001).

CONCLUSION

During medium-term follow-up, restoration of sinus rhythm by LACA results in partial return of LA function in patients with chronic AF. However, in patients with paroxysmal AF, LA catheter ablation results in decreased LA function. Whether the impairment in LA function is severe enough to predispose to LA thrombi despite elimination of AF remains to be determined.

Computed tomographic analysis of the anatomy of the left atrium and the esophagus: implications for left atrial catheter ablation

BACKGROUND

During left atrial (LA) catheter ablation, an atrioesophageal fistula can develop as a result of thermal injury of the esophagus during ablation along the posterior LA. No in vivo studies have examined the relationship of the esophagus to the LA. The purpose of this study was to describe the topographic anatomy of the esophagus and the posterior LA by use of CT.

METHODS AND RESULTS

A helical CT scan of the chest with 3D reconstruction was performed in 50 patients (mean age, 54+/-11 years) with atrial fibrillation before an ablation procedure. Consecutive axial and sagittal sections of the CT scan were examined to determine the relationship, size, and thickness of the tissue layers between the LA and the esophagus. The mean length and width of the esophagus in contact with the posterior LA were 58+/-14 and 13+/-6 mm, respectively. The esophagus had a variable course along the posterior LA. The esophagus was close (10+/-6 mm from the ostia) and parallel to the left-sided pulmonary veins (PVs) in 56% of patients and had an oblique course from the left superior PV to the right inferior PV in 36% of patients. The mean thicknesses of the posterior LA and anterior esophageal walls were 2.2+/-0.9 and 3.6+/-1.7 mm, respectively. In 98% of patients, there was a fat layer between the esophagus and the posterior LA. However, this layer was often discontinuous.

CONCLUSIONS

The esophagus and posterior LA wall are in close contact over a large area that may often lie within the atrial fibrillation ablation zone, and there is marked variation in the anatomic relationship of the esophagus and the posterior LA. Both the esophageal and atrial walls are quite thin. However, a layer of adipose tissue may serve to insulate the esophagus from thermal injury, explaining why atrioesophageal fistulas are rare.

Effects of left atrial ablation of atrial fibrillation on size of the left atrium and pulmonary veins

OBJECTIVES

The purpose of this study was to determine the effect of left atrial circumferential ablation on the size of the left atrium and pulmonary veins (PVs).

BACKGROUND

The long-term effects of left atrial circumferential ablation on left atrial and PV size and anatomy have not been analyzed in quantitative fashion.

METHODS

PV and left atrial sizes were analyzed in 41 consecutive patients (mean age 54 +/- 12 years) with paroxysmal (n = 25) or chronic (n = 16) atrial fibrillation. Computed tomography of the chest with three-dimensional reconstruction was performed before and 4 +/- 2 months after left atrial circumferential ablation. Left atrial circumferential ablation was performed to encircle the PVs 1 to 2 cm from the ostia, using a power output of 70 W. Additional ablation lines were created in the posterior left atrium and mitral isthmus. Radiofrequency energy also was delivered within the circles and at the PV ostia in 51% of patients at a reduced power output of 35 W.

RESULTS

At 6 months, 36 patients (88%) were in sinus rhythm without antiarrhythmic drug therapy, including 3 patients (7%) who developed persistent left atrial flutter and underwent subsequent successful ablation of atrial flutter. There was a 15 +/- 16% decrease in left atrial volume (P < .01) and 10 +/- 35% decrease in PV ostial area (P < .01), without focal narrowing, in patients with a successful outcome. Focal PV stenosis did not occur in any of the 41 patients.

CONCLUSIONS

Maintenance of sinus rhythm after left atrial circumferential ablation is associated with reduced left atrial and PV ostial size. Left atrial circumferential ablation for atrial fibrillation does not cause PV stenosis.

Computed Tomographic Scanning Reduces Cost and Time of Complete Spine Evaluation

BACKGROUND

We hypothesize that data collected from computed tomographic (CT) scans obtained for workup of chest or abdominal injuries provide data that are sufficient to screen for spinal fractures and will decrease the cost and time of spine evaluation after trauma.

METHODS

We reviewed plain radiographs from 55 selected trauma patients who also underwent CT scanning of the chest, abdomen, and pelvis. We also timed the radiologic workup of 50 consecutive trauma patients to determine the time required to complete radiographic spine evaluation.

RESULTS

Forty-seven patients had thoracolumbar fractures. Thirteen patients were found to have 33 thoracolumbar spine fractures identified by CT scan but not plain radiography. Fractures were found on initial trauma CT scans of the chest, abdomen, and pelvis obtained to evaluate for visceral injuries. No injuries seen on plain film were missed on CT scan.

CONCLUSION

We recommend using the data acquired from CT scans to evaluate the spine, supplementing them with additional studies only when needed for further clarification.

Anatomy of the pulmonary veins in patients with atrial fibrillation and effects of segmental ostial ablation analyzed by computed tomography

INTRODUCTION

The anatomic arrangement of pulmonary veins (PVs) is variable. No prior studies have quantitatively analyzed the effects of segmental ostial ablation on the PVs. The aim of this study was to determine the effect of segmental ostial radiofrequency ablation on PV anatomy in patients with atrial fibrillation (AF).

METHODS AND RESULTS

Three-dimensional models of the PVs were constructed from computed tomographic (CT) scans in 58 patients with AF undergoing segmental ostial ablation to isolate the PVs and in 10 control subjects without a history of AF. CT scans were repeated approximately 4 months later. PV and left atrial dimensions were measured with digital calipers. Four separate PV ostia were present in 47 subjects; 3 ostia were present in 2 subjects; and 5 ostia were present in 9 subjects. The superior PVs had a larger ostium than the inferior PVs. Patients with AF had a larger left atrial area between the PV ostia and larger ostial diameters than the controls. Segmental ostial ablation resulted in a 1.5 +/- 3.2 mm narrowing of the ostial diameter. A 28% to 61% focal stenosis was present 7.6 +/- 2.2 mm from the ostium in 3% of 128 isolated PVs. There were no instances of symptomatic PV stenosis during a mean follow-up of 245 +/- 105 days.

CONCLUSION

CT of the PVs allows identification of anatomic variants prior to catheter ablation procedures. Segmental ostial ablation results in a significant but small reduction in ostial diameter. Focal stenosis occurs infrequently and is attributable to delivery of radiofrequency energy within the PV.

The pulmonary and systemic distribution and elimination of perflubron from adult patients treated with partial liquid ventilation

OBJECTIVE

To assess the pulmonary and systemic distribution and elimination of perflubron (C(8)F(17)Br(1); LiquiVent; Alliance Pharmaceutical; San Diego, CA) during and following the period of partial liquid ventilation.

DESIGN

Prospective phase I and II clinical trial.

SETTING

Adult surgical ICU.

PATIENTS

Eighteen adult patients (mean +/- SEM age, 37.9 +/- 3.4 years) with severe respiratory failure, some of whom required extracorporeal life support (72%), and who were managed with partial liquid ventilation with perflubron.

INTERVENTIONS

Perflubron was administered into the trachea, and gas ventilation of the perfluorocarbon-filled lung (partial liquid ventilation) was then performed. Additional doses were administered daily for from 1 to 7 days, with a median cumulative dose of 31 mL/kg (range, 3 to 60 mL/kg).

MEASUREMENTS AND MAIN RESULTS

Patient blood samples were evaluated by gas chromatography for serum perflubron levels. Sequential lateral and anteroposterior radiographs were assessed, using a 5-point rating scale, for the degree of perflubron fill following the final dose. Samples of expired gas were collected, and the rate of loss of perflubron in the expired gas was measured by gas chromatography. Mean serum perflubron levels increased to 0.16 +/- 0.05 mg/dL at 24 h following administration of the initial dose. A mean maximum level of 0.26 +/- 0.05 mg/dL of perflubron was present in the serum 24 h following the administration of the last dose. This level slowly trended downward to 0.18 +/- 0.06 mg/dL over the ensuing 7 days (p = 0.281). Perflubron elimination via expired gas occurred at a mean rate of 9.4 +/- 3.0 mL/h at 1 h, and 1.0 +/- 0.4 mL/h at 48 h after the last dose (p = 0.012). By radiologic evaluation, perflubron was eliminated from the lungs progressively from 4.2 +/- 0.2 at the time of administration of the last dose, to 2.8 +/- 0.3 at 4 days later (p < 0.001). Perflubron tended to distribute and remain for longer periods in the dependent regions of the lung when compared to the nondependent regions (96-h perflubron fill score: posterior, 3.8 +/- 0.5; anterior, 1.9 +/- 0.4; p = 0.004).

CONCLUSIONS

Perflubron is eliminated at a maximum rate of 9.4 +/- 3.0 mL/h by evaporative loss from the airways and is retained in greater amounts in the dependent lung regions when compared to the nondependent lung regions. There is a low but measurable maximum blood concentration of 0.26 +/- 0.05 mg/dL in patients after perflubron administration, which did not decrease significantly after cessation of partial liquid ventilation.

An introduction to academic radiology

If you are a junior faculty member or are thinking of pursuing an academic career path, and you have read this far, you may be feeling somewhat overwhelmed. Keep all of this in perspective with your own personal goals and your "nonacademic" life outside the medical center. The multifaceted career of an academic radiologist may span 20-30 years or more. Whichever aspect of an academic career suits you best now may not be what suits you best 5 or 10 years from now. While you should be concentrating on the publication of manuscripts as an assistant professor, the other aspects, particularly administration and participation in organized radiology, may play a larger role in your career as you become more senior.