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Objectives: To investigate changes in chest CT between 3 and 12 months and associations with disease severity in patients hospitalized for COVID-19 during the first wave in 2020. Materials and methods: Longitudinal cohort study of patients hospitalized for COVID-19 in 2020. Chest CT was performed 3 and 12 months after admission. CT images were evaluated using a CT severity score (CSS) (0–12 scale) and recoded to an abbreviated version (0–3 scale). We analyzed determinants of the abbreviated CSS with multivariable mixed effects ordinal regression. Results: 242 patients completed CT at 3 months, and 124 (mean age 62.3±13.3, 78 men) also at 12 months. Between 3 and 12 months (n = 124) CSS (0–12 scale) for ground-glass opacities (GGO) decreased from median 3 (25th–75th percentile: 0–12) at 3 months to 0.5 (0–12) at 12 months (p<0.001), but increased for parenchymal bands (p<0.001). In multivariable analysis of GGO, the odds ratio for more severe abbreviated CSS (0–3 scale) at 12 months was 0.11 (95%CI 0.11 0.05 to 0.21, p<0.001) compared to 3 months, for WHO severity category 5–7 (high-flow oxygen/non-invasive ventilation/ventilator) versus 3 (non-oxygen use) 37.16 (1.18 to 43.47, p = 0.032), and for age ≥60 compared to <60 years 4.8 (1.33 to 17.6, p = 0.016). Mosaicism was reduced at 12 compared to 3 months, OR 0.33 (95%CI 0.16 to 0.66, p = 0.002). Conclusions: GGO and mosaicism decreased, while parenchymal bands increased from 3 to 12 months. Persistent GGO were associated with initial COVID-19 severity and age ≥60 years. [ABSTRACT FROM AUTHOR]

Background: Lung cancer is the most common cause of cancer-related death worldwide and therefore there has been a growing demand for low-dose computed tomography (LDCT) protocols. Purpose: To investigate and evaluate the dose and image quality of patients undergoing lung cancer screening (LCS) using LDCT in Norway. Materials and Methods: Retrospective dosimetry data, volumetric CT dose index (CTDIvol) and dose-length product (DLP), from 70 average-size and 70 large-size patients who underwent LDCT scan for LCS were included in the survey. Effective dose and size-specific dose were calculated for each examination and were compared with the American Association of Physicists in Medicine (AAPM) requirement. For a quantitative image quality analysis, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were determined for different regions in the chest with two iterative reconstruction techniques, iDose and Iterative Model Reconstruction. Differences in dose and image quality between average-size and large-size patients were evaluated by Independent sample t test, and Wilcoxon signed rank test within the same patient group. Results: The independent sample t test revealed significant differences (p <.05) in dose values between average-size and large-size patients. Mean CTDIvol and DLP for average-size patients were 2.8 mGy and 115 mGy.cm, respectively, with appropriate increment for the large-size patients. Image quality (image noise, SNR, and CNR) did not significantly differ between patient groups when images were reconstructed with a model based iterative reconstruction algorithm. Conclusion: The screening protocol assessed in this study resulted in CTDIvol values that were compliant with AAPM recommendation. No significant differences in objective image quality were found between patient groups. [ABSTRACT FROM AUTHOR]

Background: We present the final results of the effect of lung cancer screening with low-dose CT on the smoking habits of participants in a 5-year screening trial. Methods: The Danish Lung Cancer Screening Trial (DLCST) was a 5-year screening trial that enrolled 4104 subjects; 2052 were randomised to annual low-dose CT (CT group) and 2052 received no intervention (control group). Participants were current and ex-smokers (=4 weeks abstinence from smoking) with a tobacco consumption of =20 pack years. Smoking habits were determined annually. Missing values for smoking status at the final screening round were handled using two different models. Results: There were no statistically significant differences in annual smoking status between the CT group and control group. Overall the ex-smoker rates (CT + control group) significantly increased from 24% (baseline) to 37% at year 5 of screening (p<0.001). The annual point prevalence quit rate increased from 11% to 24% during the five screening rounds; the ex-smokers' relapse rate remained stable, around 11%, across the same period. Conclusions: Screening with low-dose CT had no extra effect on smoking status compared with the control group, but overall the screening programme probably promoted smoking cessation. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Contamination, defined as screening in the control arm, may dilute the statistical power of randomised screening trials. We investigated the rate of contamination in DLCST during 4 years of annual CT screening. Methods: DLCST is a randomised trial involving 4104 healthy current and ex smokers. 2052 subjects were randomised to annual low dose chest CT scans (CT group) and 2052 were given no intervention (control group). The study is performed in collaboration with the NELSON trial (Nederlands Leuvens Screening Onderzoek) and mortality data will be pooled at the end. We defined contamination as off study CT scan received for lung cancer screening purposes. Annually during the screening period, the participants were asked whether they had received a CT scan and if so the purpose. The causes were divided into the following categories: ‘Off study screening for lung cancer’, ‘Investigation of lung symptoms’, ‘Investigation of incidental finding on chest radiograph’, ‘Participation in other scientific trial involving chest CT’, and finally ‘Chest CT for other reasons’. Results: Response rates were high in both groups: 86.1% (control group), 93.6% (CT group) p <0.001. Control group: 199 out of 7065 answers (2.8%) indicating acquisition of a chest CT during 4 years of the trial. Three answers fulfilled the definition of contamination, while 8 received chest CT due to involvement in other scientific trials. 126 reported CT scans as part of investigation for other diseases, while 10 and 52 went through investigations for abnormal chest radiograph and lung symptoms, respectively. CT group: Significantly lower number of answers (n =134) indicated acquisition of an off study chest CT. None had received off study lung cancer screening. Three were involved in other scientific trials, while 17 and 115 went through investigation of lung symptoms and chest CT for other reasons, respectively. Conclusion: Although the frequency of off study chest CT was significantly higher in the control group, it was relatively small in both randomisation groups, and thus contamination seems to be modest and acceptable in the DLCST. Clinical Trial no.: Clinical Trials.gov Protocol Registration System (identification no. NCT00496977). [Copyright &y& Elsevier]

Objectives: This study presents the experiences of percutaneous CT-guided needle biopsy at a university hospital in Norway. Methods: A retrospective examination of all mediastinal biopsy procedures between April 2015 and August 2019 was performed at Akershus University Hospital in Norway. We registered patient and procedure characteristics, along with lesion pathology and characteristics including localization according to anatomical and Felson mediastinal compartments. Results: The study included 48 procedures, conducted in 45 patients (29 men and 16 women) with a mean age of 60,5 years. Pneumothorax occurred in 12 procedures (60% of the transpulmonary procedures) and pneumomediastinum in 18 procedures (38%). Pneumothorax was only seen in procedures with transpulmonal access. Four of the pneumothorax cases required pleural drainage. Diagnostic yield was 96%. We found significant (p = 0,006), moderate to high association between anatomical compartment localization and histopathological diagnosis (Cramér's V = 0,49) for tumours selected for CT-guided percutaneous biopsy. Felson's compartment division on the other hand, did not show any significant associations. Conclusion: We found CT-guided percutaneous needle biopsy of mediastinal tumours to be an effective and safe procedure with a diagnostic yield of 96%. The main complications were pneumothorax and pnumomediastinum, with a relatively low chest drainage rate. Anatomical mediastinum compartment showed a significant, moderate to high association with the histopathological diagnosis for tumours selected for percutaneous CT-guided biopsies, where most malignancies were seen in the anterior compartment. [ABSTRACT FROM AUTHOR]

Background: Low-dose CT (LDCT) chest protocols have widespread clinical applications for many indications; as a result, there is a need for protocol assessment prior to standardization. Dalhousie University and Oslo Metropolitan University have a formally established cooperative relationship. Purpose: The purpose is to assess radiation dose and image quality for LDCT chest protocols in seven different hospital locations in Norway and Canada. Material and methods: Retrospective dosimetry data, volumetric CT dose index (CTDIvol), and dose length product (DLP) from 240 average-sized patients as well as CT protocol parameters were included in the survey. Effective dose (ED) and size-specific dose estimate (SSDE) were calculated for each examination. For a quantitative image quality analysis, noise, CT number, and signal-to-noise ratio (SNR) were determined for three regions in the chest. The contrast-to-noise ratio (CNR) was calculated for lung parenchyma in comparison to the subcutaneous fat. Differences in dose and image quality were evaluated by a single-factor ANOVA test. A two-sample t -test was performed to determine differences in means between individual scanners. Results: The ANOVA test revealed significant differences (p <.05) in dose values for all scanners, including identical scanner models. Statistically significant differences (p <.05) were determined in mean values of the SNR distributions between the scanners in all three measured regions in the chest, as well as the CNR values. Conclusion: The observed variations in dose and image quality measurements, even within the same hospitals and between identical scanner models, indicate a potential for protocol optimization in the involved hospitals in both countries. [ABSTRACT FROM AUTHOR]

Objectives: Complications after CT-guided lung biopsy is a burden both for the individual patient and for the overall healthcare. Pneumothorax is the most common complication. This study determined the association between lung function tests and pneumothorax and chest drainage following CT-guided lung biopsy in consecutive patients in a large university hospital. Results: We prospectively registered 875 biopsy procedures from 786 patients in one institution from January 27th 2012 to March 1st 2017 and recorded complications including pneumothorax with or without chest drainage. Lung function data from 637 patients undergoing 710 of the procedures were available. The association of lung function measures with pneumothorax with or without chest drainage was assessed using multivariable logistic regression analyses. Diffusion capacity for carbon monoxide (DLCO) below 4.70 mmol/min/kPa was associated with increased occurrence of pneumothorax and chest drainage after CT guided lung biopsy. We found no association between FEV1, RV and occurrence of pneumothorax and chest drainage. We found low DLCO to be a risk factor of pneumothorax and chest drainage after CT-guided lung biopsy. This should be taken into account in planning and performing the procedure. [ABSTRACT FROM AUTHOR]

Objectives: Indirect computed tomography venography (CTV) is often the next imaging modality for deep vein thrombosis (DVT) when sonography is inconclusive. Our aim was to investigate the impact of scan delay and patient factors on contrast enhancement (CE) and examination quality in CTV. Methods: Patients with clinical suspicion or clinical mimics of DVT in one large hospital were enrolled. Age, sex, body weight, height, heart rate, systolic blood pressure and cardiac output were registered. CTV of the popliteal veins was obtained at 30 s intervals at 30–210 s delays. The proportions of examinations with CE exceeding predefined cut-offs were estimated and subjective examination quality was rated. Changes in CE with time, and associations between patient factors and time to peak contrast enhancement (TPCE) were modelled with mixed effects non-linear and linear regression, respectively. Results: The CE increased with increasing scan delay and reached a plateau from 120 to 210 s. The percentages of examinations achieving enhancement above cut-offs across all thresholds from 70 to 100 HU were higher at 120 s compared to 90 s (p < 0.001). After 120 s, there were no differences across scan delays for any thresholds. No patient factors showed a significant effect on TPCE. The percentage of examinations rated as acceptable was higher at 120 s compared to 90 s (p < 0.001). After 120 s, there were no statistically significant differences across scan delays. Conclusions: No patient factors were associated with TPCE in CTV. A fixed scan delay of 120–210 s yielded the best examination quality. Key Points: • Contrast enhancement reached a plateau at scan delay between 90 and 120 s. • A scan delay of 120–210 s yielded the best examination quality. • No patient factors were associated with time to peak contrast enhancement. [ABSTRACT FROM AUTHOR]

Background The effects of low-dose CT screening on disease stage shift, mortality and overdiagnosis are unclear. Lung cancer findings and mortality rates are reported at the end of screening in the Danish Lung Cancer Screening Trial. Methods 4104 men and women, healthy heavy smokers/former smokers were randomised to five annual low-dose CT screenings or no screening. Two experienced chest radiologists read all CT scans and registered the location, size and morphology of nodules. Nodules between 5 and 15 mm without benign characteristics were rescanned after 3 months. Growing nodules (>25% volume increase and/or volume doubling time<400 days) and nodules >15 mm were referred for diagnostic workup. In the control group, lung cancers were diagnosed and treated outside the study by the usual clinical practice. Results Participation rates were high in both groups (screening: 95.5%; control: 93.0%; p<0.001). Lung cancer detection rate was 0.83% at baseline and mean annual detection rate was 0.67% at incidence rounds (p=0.535). More lung cancers were diagnosed in the screening group (69 vs 24, p<0.001), and more were low stage (48 vs 21 stage I-IIB non-small cell lung cancer (NSCLC) and limited stage small cell lung cancer (SCLC), p=0.002), whereas frequencies of high-stage lung cancer were the same (21 vs 16 stage IIIA-IV NSCLC and extensive stage SCLC, p=0.509). At the end of screening, 61 patients died in the screening group and 42 in the control group (p=0.059). 15 and 11 died of lung cancer, respectively (p=0.428). Conclusion CT screening for lung cancer brings forward early disease, and at this point no stage shift or reduction in mortality was observed. More lung cancers were diagnosed in the screening group, indicating some degree of overdiagnosis and need for longer follow-up. INSET: Key messages. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a method for airway tree segmentation that uses a combination of a trained airway appearance model, vessel and airway orientation information, and region growing. We propose a voxel classification approach for the appearance model, which uses a classifier that is trained to differentiate between airway and non-airway voxels. This is in contrast to previous works that use either intensity alone or hand crafted models of airway appearance. We show that the appearance model can be trained with a set of easily acquired, incomplete, airway tree segmentations. A vessel orientation similarity measure is introduced, which indicates how similar the orientation of an airway candidate is to the orientation of the neighboring vessel. We use this vessel orientation similarity measure to overcome regions in the airway tree that have a low response from the appearance model. The proposed method is evaluated on 250 low dose computed tomography images from a lung cancer screening trial. Our experiments showed that applying the region growing algorithm on the airway appearance model produces more complete airway segmentations, leading to on average 20% longer trees, and 50% less leakage. When combining the airway appearance model with vessel orientation similarity, the improvement is even more significant than only using the airway appearance model, with on average 7% increase in the total length of branches extracted correctly. [Copyright &y& Elsevier]

Objectives: We present an analysis of predictors of pneumothorax, and pneumothorax requiring chest drainage after CT-guided lung biopsy, in one of the largest Scandinavian dataset presented. Methods: We prospectively registered 875 biopsy procedures from 786 patients in one institution from January 27, 2012, to March 1, 2017, and recorded complications including pneumothorax with or without chest drainage, and multiple variables we assumed could be associated with complications. We performed multivariable logistic regression analysis to identify predictors of pneumothorax and pneumothorax requiring chest drainage. Results: Of the biopsied lesions, 65% were malignant, 29% benign, and 6% inconclusive. Pneumothorax occurred in 39% of the procedures and chest drainage was performed in 10%. In multivariable analysis, significant predictors of pneumothorax were emphysema (OR 1.92), smaller lesion size (OR 0.83, per 1 cm increase in lesion size), lateral body position during procedure (OR 2.00), longer needle time (OR 1.09, per minute), repositioning of coaxial needle with new insertion through pleura (OR 3.04), insertion through interlobar fissure (OR 5.21), and shorter distance to pleura (OR 0.79, per 1 cm increase in distance). Predictors of chest drainage were emphysema (OR 4.01), lateral body position (OR 2.61), and needle insertion through interlobar fissure (OR 4.17). Conclusion: Predictors of pneumothorax were emphysema, lateral body position, needle insertion through interlobar fissure, repositioning of coaxial needle with new insertion through pleura, and shorter distance to pleura. The finding of lateral body position as a predictor of pneumothorax is not earlier described. Emphysema, lateral body position, and needle insertion through interlobar fissure were also predictors of chest drainage. Key Points: • Pneumothorax is a frequent complication to CT-guided lung biopsy; a smaller fraction of these complications needs chest drainage. • Predictors for pneumothorax are emphysema, smaller lesion size, lateral body position, longer needle time, repositioning of coaxial needle with new insertion through pleura, needle insertion through the interlobar fissure, and shorter distance to pleura. • Predictors for requirement for chest drainage post CT-guided lung biopsy are emphysema, lateral body position, and needle insertion through the interlobar fissure. [ABSTRACT FROM AUTHOR]

Introduction:We review the current knowledge of CT screening for lung cancer and present an expert-based, joint protocol for the proper implementation of screening in the Nordic countries. Materials and methods:Experts representing all the Nordic countries performed literature review and concensus for a joint protocol for lung cancer screening. Results and discussion:Areas of concern and caution are presented and discussed. We suggest to perform CT screening pilot studies in the Nordic countries in order to gain experience and develop specific and safe protocols for the implementation of such a program. [ABSTRACT FROM PUBLISHER]

This study presents a fully automatic, data-driven approach for texture-based quantitative analysis of chronic obstructive pulmonary disease (COPD) in pulmonary computed tomography (CT) images. The approach uses supervised learning where the class labels are, in contrast to previous work, based on measured lung function instead of on manually annotated regions of interest (ROIs). A quantitative measure of COPD is obtained by fusing COPD probabilities computed in ROIs within the lung fields where the individual ROI probabilities are computed using a k nearest neighbor (kNN) classifier. The distance between two ROIs in the kNN classifier is computed as the textural dissimilarity between the ROIs, where the ROI texture is described by histograms of filter responses from a multi-scale, rotation invariant Gaussian filter bank. The method was trained on 400 images from a lung cancer screening trial and subsequently applied to classify 200 independent images from the same screening trial. The texture-based measure was significantly better at discriminating between subjects with and without COPD than were the two most common quantitative measures of COPD in the literature, which are based on density. The proposed measure achieved an area under the receiver operating characteristic curve (AUC) of 0.713 whereas the best performing density measure achieved an AUC of 0.598. Further, the proposed measure is as reproducible as the density measures, and there were indications that it correlates better with lung function and is less influenced by inspiration level. [ABSTRACT FROM PUBLISHER]