Direct reconstruction of anatomical change in low-dose lung nodule surveillance.

Purpose: In sequential imaging studies, there exists rich information from past studies that can be used in prior-image-based reconstruction (PIBR) as a form of improved regularization to yield higher-quality images in subsequent studies. PIBR methods, such as reconstruction of difference (RoD), have demonstrated great improvements in the image quality of subsequent anatomy reconstruction even when CT data are acquired at very low-exposure settings. Approach: However, to effectively use information from past studies, two major elements are required: (1) registration, usually deformable, must be applied between the current and prior scans. Such registration is greatly complicated by potential ambiguity between patient motion and anatomical change-which is often the target of the followup study. (2) One must select regularization parameters for reliable and robust reconstruction of features. Results: We address these two major issues and apply a modified RoD framework to the clinical problem of lung nodule surveillance. Specifically, we develop a modified deformable registration approach that enforces a locally smooth/rigid registration around the change region and extend previous analytic expressions relating reconstructed contrast to the regularization parameter and other system dependencies for reliable representation of image features. We demonstrate the efficacy of this approach using a combination of realistic digital phantoms and clinical projection data. Performance is characterized as a function of the size of the locally smooth registration region of interest as well as x-ray exposure. Conclusions: This modified framework is effectively able to separate patient motion and anatomical change to directly highlight anatomical change in lung nodule surveillance.

Longitudinal assessment of interstitial lung disease in single lung transplant recipients with scleroderma.

OBJECTIVE: To investigate the natural history of fibrotic lung disease in recipients of a single lung transplant for scleroderma-associated interstitial lung disease (ILD). METHODS: Global ILD (including ground glass, nodular opacities and fibrosis) was categorized into severity quintiles on first and last post-transplant CT scans, and percent fibrosis by manual contouring was also determined, in nine single lung transplant recipients. Quantitative mean lung densities and volumes for the native and allograft lungs were also acquired. RESULTS: In the native lung, global ILD severity quintile worsened in two cases and percent fibrosis worsened in four cases (range 5-28%). In the lung allograft, one case each developed mild, moderate and severe ILD; of these, new fibrotic ILD (involving <10% of lung) occurred in two cases and acute cellular rejection occurred in one. The average change in native lung density over time was +2.2 Hounsfield Units per year and lung volume +1.4 ml per year, whereas the allograft lung density changed by -5.5 Hounsfield Units per year and total volume +27 ml per year (P = 0.011 and P = 0.039 for native vs allograft density and volume comparisons, respectively). CONCLUSIONS: While the course of ILD in the native and transplanted lungs varied in this series, these cases illustrate that disease progression is common in the native lung, suggesting that either the immune process continues to target autoantigens or ongoing fibrotic pathways are active in the native lung. Mild lung disease may occur in the allograft after several years due to either allograft rejection or recurrent mild ILD.

Comparing Frailty Markers in Predicting Poor Outcomes after Transcatheter Aortic Valve Replacement.

INTRODUCTION: Frailty is an important component of risk prognostication in transcatheter aortic valve replacement (TAVR). Objective markers of frailty, including sarcopenia, the modified Frailty Index (mFI), and albumin levels, have emerged, but little is known how such markers compare to each other in predicting outcomes after TAVR. We sought to define and compare these markers in predicting long-term outcomes after TAVR. METHODS: Patients who underwent TAVR at our institution from 2011 to 2016 were included. Indexed cross-sectional areas of the lumbosacral muscles on preoperative computed tomography scans were used to assess sarcopenia. Optimal cutoffs for sarcopenia were defined using a statistically validated method. mFI was calculated using an 11-point scale of clinical characteristics. The primary outcome was 2-year all-cause mortality. Adjusted survival analysis was used to analyze outcomes. RESULTS: A total of 381 patients were included in this study. Sarcopenia of the psoas muscles was associated with an increased risk of mortality on univariate (HR: 2.3, P = 0.01) and multivariate (HR: 2.5, P = 0.01) analysis. Sarcopenia of the paravertebral muscles was associated with increased risk of mortality only on univariate analysis (HR: 2.1, P = 0.03). Increased preoperative albumin levels were associated with decreased risk of mortality on univariate (HR: 0.3, P < 0.01) and multivariate analysis (HR: 0.3, P < 0.01). The (mFI) was not associated with mortality on univariate or multivariate analysis. DISCUSSION: Novel cutoffs for sarcopenia of the psoas muscles were determined and associated with decreased survival after TAVR. Sarcopenia and albumin levels may be better tools for risk prediction than mFI in TAVR.

Prediction of lung cancer risk at follow-up screening with low-dose CT: a training and validation study of a deep learning method.

Background: Current lung cancer screening guidelines use mean diameter, volume or density of the largest lung nodule in the prior computed tomography (CT) or appearance of new nodule to determine the timing of the next CT. We aimed at developing a more accurate screening protocol by estimating the 3-year lung cancer risk after two screening CTs using deep machine learning (ML) of radiologist CT reading and other universally available clinical information. Methods: A deep machine learning (ML) algorithm was developed from 25,097 participants who had received at least two CT screenings up to two years apart in the National Lung Screening Trial. Double-blinded validation was performed using 2,294 participants from the Pan-Canadian Early Detection of Lung Cancer Study (PanCan). Performance of ML score to inform lung cancer incidence was compared with Lung-RADS and volume doubling time using time-dependent ROC analysis. Exploratory analysis was performed to identify individuals with aggressive cancers and higher mortality rates. Findings: In the PanCan validation cohort, ML showed excellent discrimination with a 1-, 2- and 3-year time-dependent AUC values for cancer diagnosis of 0·968±0·013, 0·946±0·013 and 0·899±0·017. Although high ML score cohort included only 10% of the PanCan sample, it identified 94%, 85%, and 71% of incident and interval lung cancers diagnosed within 1, 2, and 3 years, respectively, after the second screening CT. Furthermore, individuals with high ML score had significantly higher mortality rates (HR=16·07, p<0·001) compared to those with lower risk. Interpretation: ML tool that recognizes patterns in both temporal and spatial changes as well as synergy among changes in nodule and non-nodule features may be used to accurately guide clinical management after the next scheduled repeat screening CT.

Sarcopenia of the Psoas Muscles Is Associated With Poor Outcomes Following Lung Transplantation.

BACKGROUND: Sarcopenia, a known component of frailty, defined by diminished cross-sectional area of the psoas muscles, is associated with poor outcomes after a range of surgical procedures. However, little is known of the relationship between sarcopenia of the psoas muscles (SPM) and long-term survival, decline in pulmonary function, and graft failure after lung transplantation. METHODS: We reviewed patients who underwent primary lung transplantation at our institution from 2011 to 2014. Cross-sectional areas of the psoas muscles at the L4 vertebral level were measured using preoperative computed tomography. Gender-based cutoff values for sarcopenia were generated and validated. The primary outcomes were 1-, 2-, and 3-year all-cause mortality, forced expiratory volume in 1 second values, and graft function. Adjusted logistic regression and survival analysis was used to analyze outcomes. RESULTS: Ninety-five patients were included in this study; 39 (41.1%) patients were considered sarcopenic. SPM was significantly associated with short-term and midterm mortality on multivariate analysis (1 year: odds ratio [OR], 8.7, p = 0.017; 2 years: OR, 12.7, p < 0.01; 3 years: OR, 13.4, p < 0.01). Survival analysis showed significantly decreased survival in sarcopenic patients at 3 years (35.9% versus 76.8%; p < 0.01). SPM is also associated with decreased forced expiratory volume in 1 second (coefficient, -17.3; p = 0.03). Adjusted Cox analysis showed an increased hazard for all-cause mortality (hazard ratio, 5.8, p < 0.01) and graft failure (hazard ratio, 14.7, p < 0.01) in sarcopenic patients. CONCLUSIONS: This study demonstrates a significant association between SPM and death, pulmonary function, and graft failure in patients receiving a lung transplant. Determining SPM preoperatively may be a useful component of frailty assessment and a predictor of survival in this patient population.

Added Value of Computer-aided CT Image Features for Early Lung Cancer Diagnosis with Small Pulmonary Nodules: A Matched Case-Control Study.

Purpose To test whether computer-aided diagnosis (CAD) approaches can increase the positive predictive value (PPV) and reduce the false-positive rate in lung cancer screening for small nodules compared with human reading by thoracic radiologists. Materials and Methods A matched case-control sample of low-dose computed tomography (CT) studies in 186 participants with 4-20-mm noncalcified lung nodules who underwent biopsy in the National Lung Screening Trial (NLST) was selected. Variables used for matching were age, sex, smoking status, chronic obstructive pulmonary disease status, body mass index, study year of the positive screening test, and screening results. Studies before lung biopsy were randomly split into a training set (70 cancers plus 70 benign controls) and a validation set (20 cancers plus 26 benign controls). Image features from within and outside dominant nodules were extracted. A CAD algorithm developed from the training set and a random forest classifier were applied to the validation set to predict biopsy outcomes. Receiver operating characteristic analysis was used to compare the prediction accuracy of CAD with the NLST investigator's diagnosis and readings from three experienced and board-certified thoracic radiologists who used contemporary clinical practice guidelines. Results In the validation cohort, the area under the receiver operating characteristic curve for CAD was 0.9154. By default, the sensitivity, specificity, and PPV of the NLST investigators were 1.00, 0.00, and 0.43, respectively. The sensitivity, specificity, PPV, and negative predictive value of CAD and the three radiologists' combined reading were 0.95, 0.88, 0.86, and 0.96 and 0.70, 0.69, 0.64, and 0.75, respectively. Conclusion CAD could increase PPV and reduce the false-positive rate in the early diagnosis of lung cancer. © RSNA, 2017 Online supplemental material is available for this article.

HIV Infection Is Independently Associated with Increased CT Scan Lung Density.

RATIONALE AND OBJECTIVES: Noninfectious pulmonary complications are common among HIV-infected individuals and may be detected early by quantitative computed tomography (CT) scanning. The association of HIV disease markers with CT lung density measurement remains poorly understood. MATERIALS AND METHODS: One hundred twenty-five participants free of spirometry-defined lung disease were recruited from a longitudinal cohort study of HIV-infected and HIV-uninfected individuals to undergo standardized CT scan of the chest. Parenchymal density for the entire lung volume was calculated using computerized software. Qualitative assessment of CT scans was conducted by two radiologists masked to HIV status. Linear regression models were developed to determine the independent association of markers of HIV infection on inspiratory scan mean lung density (MLD). RESULTS: HIV-infected participants had a significantly higher MLD (denser lung) compared to HIV-uninfected participants (-815 Hounsfield unit [HU] vs -837 HU; P = 0.002). After adjusting for relevant covariates, HIV infection was independently associated with 19.9 HU higher MLD (95% CI 6.04 to 33.7 HU; P = 0.005). In qualitative assessment, only ground glass attenuation and cysts were noted more commonly among HIV-infected individuals compared to HIV-uninfected individuals (34% vs 17% [P = 0.045] and 27% vs 10% [P = 0.03], respectively). No qualitative radiographic abnormalities attenuated the association between HIV infection and increased MLD. CONCLUSIONS: HIV infection is independently associated with increased lung density. Although qualitative CT abnormalities were common in this cohort, only ground glass attenuation and cysts were noted more frequently in HIV-infected participants, suggesting that the increased lung density observed among HIV-infected individuals may be associated with subclinical inflammatory lung changes.

Remote reading of coronary CTA exams using a tablet computer: utility for stenosis assessment and identification of coronary anomalies.

The feasibility of remote reading of coronary CT examinations on tablet computers has not been evaluated. The purpose of this study is to evaluate the accuracy of coronary CT angiography reading using an iPad compared to standard 3D workstations. Fifty coronary CT angiography exams, including a spectrum of coronary artery disease and anatomic variants, were reviewed. Coronary CT angiography exams were interpreted by two readers independently on an iPad application (Siemens Webviewer) and a clinical 3D workstation at sessions 2 weeks apart. Studies were scored per vessel for severity of stenosis on a 0-3 scale (0 none, 1 <50 %, 2 ≥50-69 %, 3 ≥70 %). Coronary anomalies were recorded. A consensus read by two experienced cardiac imagers was used as the reference standard. Level of agreement with the reference for iPad and 3D workstations was compared. Multivariate logistic regression was used to analyze the relationship between agreement and display type and to adjust for inter-reader differences. For both readers, there was no significant difference in agreement with the reference standard for per-vessel stenosis scores using either the 3D workstation or the iPad. In a multivariable logistic regression analysis including reader, workstation, and vessel as co-variates, there was no significant association between workstation type or reader and agreement with the reference standard (p > 0.05). Both readers identified 100 % of coronary anomalies using each technique. Reading of coronary CT angiography examinations on the iPad had no influence on stenosis assessment compared to the standard clinical workstation.

Mosaic Attenuation: Etiology, Methods of Differentiation, and Pitfalls.

Mosaic attenuation is a commonly encountered pattern on computed tomography that is defined as heterogeneous areas of differing lung attenuation. This heterogeneous pattern of attenuation is the result of diverse causes that include diseases of the small airways, pulmonary vasculature, alveoli, and interstitium, alone or in combination. Small airways disease can be a primary disorder, such as respiratory bronchiolitis or constrictive bronchiolitis, or be part of parenchymal lung disease, such as hypersensitivity pneumonitis, or large airways disease, such as bronchiectasis and asthma. Vascular causes resulting in mosaic attenuation are typically chronic thromboembolic pulmonary hypertension, which is characterized by organizing thrombi in the elastic pulmonary arteries, or pulmonary arterial hypertension, a heterogeneous group of diseases affecting the distal pulmonary arterioles. Diffuse ground-glass opacity can result in a mosaic pattern related to a number of processes in acute (eg, infection, pulmonary edema), subacute (eg, organizing pneumonia), or chronic (eg, fibrotic diseases) settings. Imaging clues that can assist the radiologist in pinpointing a diagnosis include evidence of large airway involvement, cardiovascular abnormalities, septal thickening, signs of fibrosis, and demonstration of airtrapping at expiratory imaging.

Coronary computed tomography angiography for the assessment of acute chest pain in the emergency department: evidence, guidelines, and tips for implementation.

Acute chest pain is an important clinical challenge and a major reason for presentation to the emergency department. Although multiple imaging techniques are available to assess such patients, considerable interest has focused on the use of coronary computed tomography (CT) angiography. Three recent multicenter trials have demonstrated the value of coronary CT angiography (CCTA) to diagnose patients with acute coronary syndrome (ACS) rapidly and accurately. Guidelines developed on the basis of these and other studies suggest that CCTA is optimally used in patients with low to intermediate risk for ACS. A related protocol, the triple rule-out scan, may be valuable if overlapping symptoms occur, particularly between those of ACS and pulmonary embolism. In developing a program to perform CCTA in the emergency room, it is important to work closely with emergency physicians and cardiologists to maximize appropriate use of this technique and to develop appropriate protocols that minimize radiation dose. Ongoing efforts to improve existing capabilities of CCTA include better characterization of coronary plaque and the use of CT fractional flow reserve and perfusion techniques.

The appendix may protect against Clostridium difficile recurrence.

BACKGROUND & AIMS: Several risk factors have been identified for the development of recurrent Clostridium difficile infection (CDI) that alter host immunity and disrupt colonic flora. Although the function of the appendix has been debated, its active, gut-associated lymphoid tissue and biofilm production indicate potential roles in recovery from initial CDI and protection against recurrent CDI. We investigated whether the presence or absence of an appendix is associated with CDI recurrence. METHODS: We reviewed the medical records of adult inpatients with CDI who were admitted to a tertiary-care teaching hospital from 2005 to 2007 to identify those with and without an appendix. The primary dependent variable for statistical analysis was CDI recurrence. RESULTS: In a multivariate analysis of 11 clinical variables, the presence of an appendix was associated inversely with CDI recurrence (P < .0001; adjusted relative risk, .398). Age older than 60 years also was associated with CDI recurrence (P = .0280; adjusted relative risk, 2.44). CONCLUSIONS: The presence of an appendix has a significant and independent, inverse association with CDI recurrence, but this finding requires validation in a prospective study. Assessing the presence or absence of an appendix might be useful in predicting CDI recurrence.