Classifying Future Healthcare Utilization in COPD Using Quantitative CT Lung Imaging and Two-Step Feature Selection via Sparse Subspace Learning with the CanCOLD Study.

RATIONALE: Although numerous candidate features exist for predicting risk of higher risk of healthcare utilization in patients with chronic obstructive pulmonary disease (COPD), the process for selecting the most discriminative features remains unclear. OBJECTIVE: The objective of this study was to develop a robust feature selection method to identify the most discriminative candidate features for predicting healthcare utilization in COPD, and compare the model performance with other common feature selection methods. MATERIALS AND METHODS: In this retrospective study, demographic, lung function measurements and CT images were collected from 454 COPD participants from the Canadian Cohort Obstructive Lung Disease study from 2010-2017. A follow-up visit was completed approximately 1.5 years later and participants reported healthcare utilization. CT analysis was performed for feature extraction. A two-step hybrid feature selection method was proposed that utilized: (1) sparse subspace learning with nonnegative matrix factorization, and, (2) genetic algorithm. Seven commonly used feature selection methods were also implemented that reported the top 10 or 20 features for comparison. Performance was evaluated using accuracy. RESULTS: Of the 454 COPD participants evaluated, 161 (35%) utilized healthcare services at follow-up. The accuracy for predicting subsequent healthcare utilization for the seven commonly used feature selection methods ranged from 72%-76% with the top 10 features, and 77%-80% with the top 20 features. Relative to these methods, hybrid feature selection obtained significantly higher accuracy for predicting subsequent healthcare utilization at 82% ± 3% (p < 0.05). Selected features with the proposed method included: DLCO, FEV1, RV, FVC, TAC, LAA950, Pi-10, LAA856, LAC total hole count, outer area RB1, wall area RB1, wall area and Jacobian. CONCLUSION: The hybrid feature selection method identified the most discriminative features for classifying individuals with and without future healthcare utilization, and increased the accuracy compared to other state-of-the-art approaches.

CAR and CSTR Cardiac Computed Tomography (CT) Practice Guidelines: Part 2-Non-Coronary Imaging.

The cardiac computed tomography (CT) practice guidelines provide an updated review of the technological improvements since the publication of the first Canadian Association of Radiologists (CAR) cardiac CT practice guidelines in 2009. An overview of the current evidence supporting the use of cardiac CT in the most common clinical scenarios, standards of practice to optimize patient preparation and safety as well as image quality are described. Coronary CT angiography (CCTA) is the focus of Part I. In Part II, an overview of cardiac CT for non-coronary indications that include valvular and pericardial imaging, tumour and mass evaluation, pulmonary vein imaging, and imaging of congenital heart disease for diagnosis and treatment monitoring are discussed. The guidelines are intended to be relevant for community hospitals and large academic centres with established cardiac CT imaging programs.

CAR and CSTR Cardiac Computed Tomography (CT) Practice Guidelines: Part 1 Coronary CT Angiography (CCTA).

Imaging the heart is one of the most technically challenging applications of Computed Tomography (CT) due to the presence of cardiac motion limiting optimal visualization of small structures such as the coronary arteries. Electrocardiographic gating during CT data acquisition facilitates motion free imaging of the coronary arteries. Since publishing the first version of the Canadian Association of Radiologists (CAR) cardiac CT guidelines, many technological advances in CT hardware and software have emerged necessitating an update. The goal of these cardiac CT practice guidelines is to present an overview of the current evidence supporting the use of cardiac CT in various clinical scenarios and to outline standards of practice for patient safety and quality of care when establishing a cardiac CT program in Canada.

Lung imaging patterns in connective tissue disease-associated interstitial lung disease impact prognosis and immunosuppression response.

OBJECTIVES: Interstitial lung disease (ILD) in connective tissue diseases (CTD) have highly variable morphology. We aimed to identify imaging features and their impact on ILD progression, mortality and immunosuppression response. METHODS: Patients with CTD-ILD had high-resolution chest computed tomography (HRCT) reviewed by expert radiologists blinded to clinical data for overall imaging pattern (usual interstitial pneumonia [UIP]; non-specific interstitial pneumonia [NSIP]; organizing pneumonia [OP]; fibrotic hypersensitivity pneumonitis [fHP]; and other). Transplant-free survival and change in percent-predicted forced vital capacity (FVC) were compared using Cox and linear mixed effects models adjusted for age, sex, smoking, and baseline FVC. FVC decline after immunosuppression was compared with pre-treatment. RESULTS: Of 645 CTD-ILD patients, the frequent CTDs were systemic sclerosis (n = 215), rheumatoid arthritis (n = 127), and inflammatory myopathies (n = 100). NSIP was the most common pattern (54%), followed by UIP (20%), fHP (9%), and OP (5%). Compared with UIP, FVC decline was slower for NSIP (1.1%/year, 95%CI 0.2, 1.9) and OP (3.5%/year, 95%CI 2.0, 4.9), and mortality was lower for NSIP (HR 0.65, 95%CI 0.45, 0.93) and OP (HR 0.18, 95%CI 0.05, 0.57), but higher in fHP (HR 1.58, 95%CI 1.01, 2.40). The extent of fibrosis also predicted FVC decline and mortality. After immunosuppression, FVC decline was slower compared with pre-treatment in NSIP (by 2.1%/year, 95%CI 1.4, 2.8), with no change for UIP or fHP. CONCLUSION: Multiple radiologic patterns are possible in CTD-ILD, including a fHP pattern. NSIP and OP were associated with better outcomes and response to immunosuppression, while fHP had worse survival compared with UIP.

Core and Advanced Thoracic Imaging Curricula to Guide Residency and Fellowship Training: A Framework From the Canadian Society of Thoracic Radiology.

RATIONALE: A well-defined curriculum with goals and objectives is an inherent part of every radiology training program. MATERIALS AND METHODS: Following a needs assessment, the Canadian Society of Thoracic Radiology Education Committee developed a thoracic imaging curriculum using a mixed- method approach, complimentary to the cardiac curriculum published as a separate document. RESULTS: The Thoracic Imaging Curriculum consists of two separate yet complimentary parts: a Core Curriculum, aimed at residents in-training, with the main goal of building a strong foundational knowledge, and an Advanced Curriculum, designed to build upon the core knowledge and guide a more in-depth subspecialty training. CONCLUSION: The curricular frameworks aim to enhance the educational experience of residents and fellows and provide an educational framework for clinical supervisors and residency and fellowship program directors. SUMMARY STATEMENT: The Canadian Society of Thoracic Radiology championed the creation of Cardiovascular and Thoracic Imaging curricula encompassing clinical knowledge and technical, communication, and decision-making skills with the goal of providing direction to a strong foundational knowledge for residents and to guide specialty training for fellowship programs.

Integration and Application of Radiologic Patterns From Clinical Practice Guidelines on Idiopathic Pulmonary Fibrosis and Fibrotic Hypersensitivity Pneumonitis.

BACKGROUND: Clinical practice guidelines separately describe radiologic patterns of usual interstitial pneumonia (UIP) and fibrotic hypersensitivity pneumonitis (fHP), without direction on whether or how to apply these approaches concurrently within a single patient. RESEARCH QUESTION: How can we integrate guideline-defined radiologic patterns to diagnose interstitial lung disease (ILD) and what are the pitfalls associated with described patterns that require reassessment in future guidelines? STUDY DESIGN AND METHODS: Patients from the Canadian Registry for Pulmonary Fibrosis underwent detailed reevaluation in standardized multidisciplinary discussion. CT scan features were quantified by chest radiologists masked to clinical data, and guideline-defined patterns were assigned. Clinical data then were provided to the radiologist and an ILD clinician, who jointly determined the leading diagnosis. RESULTS: Clinical-radiologic diagnosis in 1,593 patients was idiopathic pulmonary fibrosis (IPF) in 26%, fHP in 12%, connective tissue disease-associated ILD (CTD-ILD) in 34%, idiopathic pneumonia with autoimmune features in 12%, and unclassifiable ILD in 10%. Typical and probable UIP patterns corresponded to a diagnosis of IPF in 66% and 57% of patients, respectively. Typical fHP pattern corresponded to an fHP clinical diagnosis in 65% of patients, whereas compatible fHP was nonspecific and associated with CTD-ILD or IPAF in 48% of patients. No pattern ruled out CTD-ILD. Gas trapping affecting > 5% of lung parenchyma on expiratory imaging was an important feature broadly separating compatible and typical fHP from other patterns (sensitivity, 0.77; specificity, 0.91). INTERPRETATION: An integrated approach to guideline-defined UIP and fHP patterns is feasible and supports > 5% gas trapping as an important branch point. Typical or probable UIP and typical fHP patterns have moderate predictive values for a corresponding diagnosis of IPF and fHP, although occasionally confounded by CTD-ILD; compatible fHP is nonspecific.

National Core and Advanced Cardiac Imaging Curricula: A Framework From the Canadian Society of Thoracic Radiology Education Committee.

RATIONALE: Well-defined curriculum with goals and objectives is an inherent part of every radiology residency program. MATERIALS AND METHODS: Following a needs assessment, the Canadian Society of Thoracic Radiology education committee developed a cardiac imaging curriculum using a mixed method collaborative approach. RESULTS: The Cardiovascular Imaging Curricula consist each of two separate yet complimentary granular parts: a Core Curriculum, aimed at residents in-training, with the main goal of building a strong foundational knowledge and an Advanced Curriculum, designed to build upon the core knowledge and guide a more in-depth fellowship subspecialty training. CONCLUSION: The curricular frameworks aim to enhance the educational experience of trainees (residents and fellows) and provide an educational framework for clinical supervisors and residency and fellowship program directors. SUMMARY STATEMENT: The Canadian Society of Thoracic Radiology (CSTR) championed the creation of Cardiovascular and Thoracic Imaging curricula encompassing clinical knowledge and technical, communication, and decision-making skills with the goal of providing direction to a strong foundational knowledge for residents and to guide specialty training for fellowship programs.

Quantitative computed tomography and visual emphysema scores: association with lung function decline.

Background: Computed tomography (CT) visual emphysema score is a better predictor of mortality than single quantitative CT emphysema measurements in COPD, but there are numerous CT measurements that reflect COPD-related disease features. The purpose of this study was to determine if linear combinations of quantitative CT measurements by principal component analysis (PCA) have a greater association with forced expiratory volume in 1 s (FEV1) lower limit of normal (LLN) annualised change (ΔFEV1) than visual emphysema score in COPD. Methods: In this retrospective, longitudinal study, demographic, spirometry and CT images were acquired. CT visual emphysema score and quantitative analysis were performed; low attenuation area <950 HU (LAA950) and 12 other quantitative CT measurements were investigated. PCA was used for CT feature extraction. Multiple linear regression models for baseline FEV1 LLN and 6-year ΔFEV1 were used to determine associations with visual emphysema score and CT measurements. A total of 725 participants were analysed (n=299 never-smokers, n=242 at-risk and n=184 COPD). Results: Quantitative CT measures (LAA950 and PCA components) were independently statistically significant (p<0.05) in predicting baseline FEV1 LLN, whereas visual emphysema score was not statistically significant in any baseline model. When predicting 6-year ΔFEV1, only visual emphysema score was significant (p<0.05) in models with LAA950 and PCA combination of emphysema measurements. In the model with PCA using all CT measurements predicting 6-year ΔFEV1, visual emphysema score (p=0.021) along with one PCA component (p=0.004) were statistically significant. Conclusions: PCA with a combination of CT measurements reflecting several different COPD-related disease features independently predicted baseline lung function and increased the relative importance of quantitative CT compared with visual emphysema score for predicting lung function decline.

Knowledge and Perceptions of Competency-Based Medical Education in Diagnostic Radiology Post-Graduate Medical Education: Identifying Priorities and Developing a Framework for Professional Development Activities.

Introduction: We evaluated knowledge and perceptions of an established Competency-Based Medical Education (CBME) model developed by the Royal College of Physicians and Surgeons of Canada, Competence by Design (CBD), and identified evidence-informed priorities for professional development activities (PDAs). Materials and Methods: Teaching faculty and residents at a single, large diagnostic radiology post-graduate medical education (PGME) program were eligible to participate in this cross-sectional, survey-based study. Knowledge of CBD was evaluated through multiple choice questions (MCQs), which assessed participants' understanding of major principles and terms associated with CBD. Participants' perceptions of the anticipated impact of CBD on resident education and patient care were evaluated and priorities for PDAs were identified, which informed a framework for CBD PDAs. Results: Fifty faculty and residents participated. The faculty and resident response rates were 11.6% (n = 29/249) and 55.3% (n = 21/38), respectively. The mean ± standard deviation overall score on MCQs was 39.0% ± 20.4%. The majority of participants perceived the impact of CBD on resident education to be equivocal and to not impact patient care. Knowledge of CBD was not statistically significantly associated with participants' perceptions of the impact of CBD on either resident education or patient care (P > .05). Delivery of high-quality feedback was the greatest priority identified for PDAs. Discussion: Our results and proposed CBD PDAs framework may help to guide diagnostic radiology PGME programs in designing evidence-informed PDAs, which may meaningfully contribute to the successful implementation of CBD in diagnostic radiology PGME. As diagnostic radiology PGME programs throughout the world increasingly implement CBME models, evidence-informed PDAs will become of increasing importance.

Preparedness of Residents and Medical Students for the Transition to Competence by Design in Diagnostic Radiology Post-Graduate Medical Education.

Introduction: This needs assessment evaluated residents' and medical students' knowledge of Competence by Design (CBD), perceived benefits of and challenges or barriers to the transition to CBD for residents, and perceived overall preparedness for the transition to CBD in diagnostic radiology. Materials and Methods: All diagnostic radiology residents and medical students in Canada were eligible to participate in this national cross-sectional, questionnaire-based needs assessment. Knowledge of CBD was evaluated through participants' self-reported rating of their knowledge of CBD on a 5-point Likert scale. Perceived benefits of and challenges or barriers to the transition to CBD for residents were rank ordered. Participants' overall self-reported preparedness for the transition to CBD was assessed on a 5-point Likert scale. Data were summarized by descriptive statistics and bivariate analyses were conducted as appropriate. Results: Ninety-four residents (n = 77) and medical students (n = 17) participated in this needs assessment. Participants' mean ± standard deviation self-reported rating of their overall knowledge of CBD was 2.86 ± .94. Provision of meaningful feedback to learners and learners' ability to identify their own educational needs were among the highest ranked perceived benefits of the transition to CBD, while demands on time and increased frequency of evaluation were among the highest ranked perceived challenges or barriers to the transition to CBD. Few participants reported being either "prepared" (4.7%) or "somewhat prepared" (14.0%) for the transition to CBD. Conclusion: Preparedness for the transition to CBD in diagnostic radiology may be improved. Targeted interventions to augment the preparedness of residents and medical students should be considered.

Accuracy, Reproducibility and User Experience With Standardized Instructions for Measurement of Total Kidney Volume in Autosomal Dominant Polycystic Kidney Disease.

PURPOSE: Total kidney volume (TKV) measurement is integral in clinical management of autosomal dominant polycystic kidney disease (ADPKD) but the gold standard of measurement via stereology/manual planimetry is time-consuming and not readily available to clinicians. This study assessed whether standardized measurement instructions based on an ellipsoid equation enhanced TKV assessment on computed tomographic (CT) images of the kidneys as determined by accuracy, reproducibility, efficiency and/or user acceptability. METHODS: Participating radiologists were randomized to perform TKV measurements with or without standardized instructions. All participants measured the same 3 non-contrast, low-dose CT scans. Accuracy was assessed as variation from TKV measurements obtained by planimetry. Intraclass correlation coefficients and time to complete the measurements were assessed. Surveys assessed prior experience with TKV measurement and user acceptability of the instructions. RESULTS: 49 radiologists participated. There was no difference in accuracy or measurement time between instructed and non-instructed participants. There was a trend towards greater reproducibility with standardized instructions (ICC .8 vs .6). 92% of respondents indicated the instructions were easy to use, 86% agreed the instructions would enhance their comfort with TKV measurement and 75% agreed they would recommend these instructions to colleagues. CONCLUSIONS: Instructed and non-instructed participants demonstrated similar accuracy and time required for TKV measurement, but instructed participants had a trend towards greater reproducibility. There was high acceptability including enhanced user confidence with the instructions. Standardized instructions may be of value for radiologists seeking to improve their confidence in providing clinicians with TKV measurements necessary to appropriately manage this patient population.

Ischemia With Nonobstructive Coronary Arteries: Insights From the ISCHEMIA Trial.

BACKGROUND: Ischemia with nonobstructive coronary arteries (INOCA) is common clinically, particularly among women, but its prevalence among patients with at least moderate ischemia and the relationship between ischemia severity and non-obstructive atherosclerosis severity are unknown. OBJECTIVES: The authors investigated predictors of INOCA in enrolled, nonrandomized participants in ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches), sex differences, and the relationship between ischemia and atherosclerosis in patients with INOCA. METHODS: Core laboratories independently reviewed screening noninvasive stress test results (nuclear imaging, echocardiography, magnetic resonance imaging or nonimaging exercise tolerance testing), and coronary computed tomography angiography (CCTA), blinded to results of the screening test. INOCA was defined as all stenoses <50% on CCTA in a patient with moderate or severe ischemia on stress testing. INOCA patients, who were excluded from randomization, were compared with randomized participants with ≥50% stenosis in ≥1 vessel and moderate or severe ischemia. RESULTS: Among 3,612 participants with core laboratory-confirmed moderate or severe ischemia and interpretable CCTA, 476 (13%) had INOCA. Patients with INOCA were younger, were predominantly female, and had fewer atherosclerosis risk factors. For each stress testing modality, the extent of ischemia tended to be less among patients with INOCA, particularly with nuclear imaging. There was no significant relationship between severity of ischemia and extent or severity of nonobstructive atherosclerosis on CCTA. On multivariable analysis, female sex was independently associated with INOCA (odds ratio: 4.2 [95% CI: 3.4-5.2]). CONCLUSIONS: Among participants enrolled in ISCHEMIA with core laboratory-confirmed moderate or severe ischemia, the prevalence of INOCA was 13%. Severity of ischemia was not associated with severity of nonobstructive atherosclerosis. (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches [ISCHEMIA]; NCT01471522).

Outcomes With Intermediate Left Main Disease: Analysis From the ISCHEMIA Trial.

BACKGROUND: Patients with significant (≥50%) left main disease (LMD) have a high risk of cardiovascular events, and guidelines recommend revascularization to improve survival. However, the impact of intermediate LMD (stenosis, 25%-49%) on outcomes is unclear. METHODS: Randomized ISCHEMIA (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches) participants who underwent coronary computed tomography angiography at baseline were categorized into those with (25%-49%) and without (<25%) intermediate LMD. The primary outcome was a composite of cardiovascular mortality, myocardial infarction (MI), or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. The primary quality of life outcome was the Seattle Angina Questionnaire summary score. RESULTS: Among the 3699 participants who satisfied the inclusion criteria, 962 (26%) had intermediate LMD. Among invasive strategy participants with intermediate LMD on coronary computed tomography angiography, 49 (7.0%) had significant (≥50% stenosis) left main stenosis on invasive angiography. Patients with intermediate LMD had a higher risk of cardiovascular events in the unadjusted but not in the fully adjusted model compared with those without intermediate LMD. An invasive strategy increased procedural MI and decreased nonprocedural MI with no significant difference for other outcomes including the primary end point. There was no meaningful heterogeneity of treatment effect based on intermediate LMD status except for nonprocedural MI for which there was a greater absolute reduction with invasive management in the intermediate LMD group (-6.4% versus -2.0%; Pinteraction=0.049). The invasive strategy improved angina-related quality of life and the benefit was durable throughout follow-up without significant heterogeneity based on intermediate LMD status. CONCLUSIONS: In the ISCHEMIA trial, there was no meaningful heterogeneity of treatment benefit from an invasive strategy regardless of intermediate LMD status except for a greater absolute risk reduction in nonprocedural MI with invasive management in those with intermediate LMD. An invasive strategy increased procedural MI, reduced nonprocedural MI, and improved angina-related quality of life. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT01471522.

Review of Challenges to the Implementation of Competence by Design in Post-Graduate Medical Education: What Can Diagnostic Radiology Learn from the Experience of Other Specialty Disciplines?

Competence by Design (CBD) is a medical education initiative instituted by the Royal College of Physicians and Surgeons of Canada to improve the training of resident physicians in specialty disciplines. CBD integrates Competency Based Medical Education with traditional specialty discipline post-graduate medical education (PGME) training through the application of an organizational framework of competencies. Various specialty disciplines in Canada have transitioned to CBD since 2017 in a staggered approach. Diagnostic radiology PGME programs in Canada are expected to transition to CBD in 2022 for the incoming resident physician cohort. This article reviews potential challenges to the implementation of CBD in diagnostic radiology PGME programs and proposes evidence-informed targeted strategies and solutions to address these challenges. It is important for diagnostic radiology PGME programs to understand the challenges pertaining to the implementation of CBD so that they may be able to successfully implement this or similar medical education initiatives in their programs. Moreover, as radiology subspecialty PGME programs, such as nuclear medicine, interventional radiology, neuroradiology, and pediatric radiology, likewise transition to CBD and diagnostic radiology PGME programs internationally increasingly implement other Competency Based Medical Education models, the implications of the challenges pertaining to the implementation of CBD will further become of increasing importance.

Oncologic Outcomes Associated With MRI-detected Extramural Venous Invasion (mrEMVI) in Rectal Cancer: A Systematic Review and Meta-analysis.

BACKGROUND: The role of MRI-detected EMVI (mrEMVI) as a reliable prognostic factor in rectal cancer has been emphasized in recent years but this finding remains underreported by many institutions. OBJECTIVE: This review aimed to demonstrate the importance of pre- and post-treatment MRI-detected EMVI as independent prognostic factors of adverse oncologic outcomes in patients undergoing neoadjuvant therapy followed by total mesorectal excision. METHODS: This review was designed using the PRISMA guidelines. The following electronic databases were searched from January 2002 to January 2020: CENTRAL, Ovid MEDLINE, PubMed, and Ovid Embase. Main outcomes included DFS and overall survival (OS). Other outcomes of interest comprised positive resection margin and synchronous metastases. RESULTS: Seventeen studies involving a total of 3821 patients were included for data synthesis. For preneoadjuvant treatment mrEMVI, pooled hazard ratio (HR) estimate for DFS was 2.30 (95% confidence intervals (CI) 1.54-3.44) for higher recurrence in mrEMVI-positive patients. mrEMVI-positive patients were found to have a lower OS with a pooled HR of 1.68 (95%CI 1.27-2.22). Pooled risk ratio for synchronous metastasis was 4.11 (95%CI 2.80-6.02) for mrEMVI-positivity. For postneoadjuvant treatment EMVI (ymrEMVI), positive status showed a lower DFS with a pooled HR of 2.04 (95%CI 1.55-2.69). Risk ratio of having a positive resection margin status was 2.95 (95%CI 1.75-4.98) for ymrEMVI-positive patients. CONCLUSIONS: This review showed that oncologic outcomes are significantly worse for both pre- and post-neoadjuvant treatment mrEMVI-positive patients. MRI-detected EMVI should be consistently reported in rectal cancer staging and may provide guidance for the targeted use of additional systemic therapy.

Spatial Dependence of CT Emphysema in Chronic Obstructive Pulmonary Disease Quantified by Using Join-Count Statistics.

Background Existing CT emphysema measurements quantify the extent or clustering of emphysema voxels in chronic obstructive pulmonary disease (COPD); however, these measurements do not quantify how those voxels are clustered. Purpose To develop a CT measurement to quantify the "compactness" of emphysema voxels, called the normalized join count (NJC), and to determine whether the NJC measurement differentiates COPD disease severity and correlates with lung function and visual emphysema scores. Materials and Methods In this secondary analysis of a prospective study, lung function and CT images were obtained from the Canadian Cohort Obstructive Lung Disease study visit 1 from 2009 to 2013. Participants were categorized as never-smokers, at risk, mild COPD, or moderate-severe COPD. Diffusion capacity for carbon monoxide/alveolar volume was measured. CT emphysema was scored visually by radiologists. CT measurements included the percentage low-attenuation area with attenuation less than -950 HU (%LAA-950insp), low-attenuation cluster (LAC), and lowest 15th percentile point of the CT lung density histogram. NJC was developed to measure compactness of CT emphysema voxels. An analysis of variance determined differences between groups. Multivariable ridge regression determined association between CT measurements with lung function and radiologist scores. Results A total of 1294 participants (750 men; mean age, 67 years ± 10) were analyzed (277 never-smokers, 306 at risk, 427 mild COPD, and 284 moderate-severe COPD). NJC, %LAA-950insp, and LAC measurements were higher in moderate-severe COPD than in never-smokers and at-risk participants (P < .05 for all comparisons), but only NJC was different between mild and ;moderate-severe COPD (mean, 1.98% ± 3.61 vs 1.44% ± 2.14; P < .05). In multivariable regression analysis, among all CT measurements NJC had the greatest relative contribution to diffusion capacity for carbon monoxide/alveolar volume (P = .002) and visual emphysema score (P < .001). Conclusion The relationship of normalized join count with severity of chronic obstructive pulmonary disease may indicate that the assessment of this disease is dependent on the number of low attenuating voxels or the size of clusters and the spatial arrangement of such voxels. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Grenier in this issue.