Lung imaging methods: indications, strengths and limitations.

Imaging methods are fundamental tools to detect and diagnose lung diseases, monitor their treatment and detect possible complications. Each modality, starting from classical chest radiographs and computed tomography, as well as the ever more popular and easily available thoracic ultrasound, magnetic resonance imaging and nuclear medicine methods, and new techniques such as photon counting computed tomography, radiomics and application of artificial intelligence, has its strong and weak points, which we should be familiar with to properly choose between the methods and interpret their results. In this review, we present the indications, strengths and main limitations of methods for chest imaging.

Discrepancy Between Achieved and Vendor-Predicted Ablation Zones in the Lung: Contributing Factors.

PURPOSE: Several factors are known to affect lung ablation zones. Questions remain as to why there are discrepancies between achieved and vendor-predicted ablation zones and what contributing factors can be modified to balance therapeutic effects with avoidance of complications. This retrospective study of lung tumour microwave ablation analyses day 1 post-treatment CT to assess the effects of lesion-specific and operator-dependent factors on ablation zones. METHODS AND MATERIALS: Consecutive patients treated at a tertiary centre from 2018 to 2021 were included. All ablations were performed using a single microwave ablation device under lung isolation. The lung tumours were categorised as primary or secondary, and their "resistance" to ablation was graded according to their locations. Intraprocedural pulmonary inflation was assessed as equal to or less than the contralateral non-isolated lung. Ablation energy was categorised as high, medium, or low. Ablation zone dimensions were measured on day 1 CT and compared to vendor reference charts. Ablations with multiple needle positions or indeterminate boundaries were excluded. RESULTS: A total of 47 lesions in 31 patients were analysed. Achieved long axes are longer than predicted by 5 mm or 14% (p < 0.01) without overall short axis discrepancy. Secondary tumours (p = 0.020), low-resistance location (p < 0.01), good lung inflation (p < 0.01), low (p = 0.003) and medium (p = 0.038) total energy produce lengthened long axes by 4-6 mm or 10-19%. High total energy results in shorter than predicated short axes by 6 mm or 18% (p = 0.010). CONCLUSION: We identified several factors affecting ablation zone dimensions which may have implications for ablation planning and the avoidance of complications.

Radiomics-based decision support tool assists radiologists in small lung nodule classification and improves lung cancer early diagnosis.

BACKGROUND: Methods to improve stratification of small (≤15 mm) lung nodules are needed. We aimed to develop a radiomics model to assist lung cancer diagnosis. METHODS: Patients were retrospectively identified using health records from January 2007 to December 2018. The external test set was obtained from the national LIBRA study and a prospective Lung Cancer Screening programme. Radiomics features were extracted from multi-region CT segmentations using TexLab2.0. LASSO regression generated the 5-feature small nodule radiomics-predictive-vector (SN-RPV). K-means clustering was used to split patients into risk groups according to SN-RPV. Model performance was compared to 6 thoracic radiologists. SN-RPV and radiologist risk groups were combined to generate "Safety-Net" and "Early Diagnosis" decision-support tools. RESULTS: In total, 810 patients with 990 nodules were included. The AUC for malignancy prediction was 0.85 (95% CI: 0.82-0.87), 0.78 (95% CI: 0.70-0.85) and 0.78 (95% CI: 0.59-0.92) for the training, test and external test datasets, respectively. The test set accuracy was 73% (95% CI: 65-81%) and resulted in 66.67% improvements in potentially missed [8/12] or delayed [6/9] cancers, compared to the radiologist with performance closest to the mean of six readers. CONCLUSIONS: SN-RPV may provide net-benefit in terms of earlier cancer diagnosis.

A Comparison of Long-Term Outcomes in Patients Managed With Venovenous Extracorporeal Membrane Oxygenation in the First and Second Waves of the COVID-19 Pandemic in the United Kingdom.

OBJECTIVES: Early studies of venovenous extracorporeal membrane oxygenation (ECMO) in COVID-19 have revealed similar outcomes to historical cohorts. Changes in the disease and treatments have led to differences in the patients supported on venovenous ECMO in the first and second waves. We aimed to compare these two groups in both the acute and follow-up phase. DESIGN: Retrospective single-center cohort study comparing mortality at censoring date (November 30, 2021) and decannulation, patient characteristics, complications and lung function and quality of life (QOL-by European Quality of Life 5 Dimensions 3 Level Version) at first follow-up in patients supported on venovenous ECMO between wave 1 and wave 2 of the COVID-19 pandemic. SETTING: Critical care department of a severe acute respiratory failure service. PATIENTS: Patients supported on ECMO for COVID-19 between wave 1 (March 17, 2020, to August 31, 2020) and wave 2 (January 9, 2020, to May 25, 2021). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One hundred twenty-three patients were included in our analysis. Survival at censoring date (χ 2 , 6.35; p = 0.012) and decannulation (90.4% vs 70.0%; p < 0.001) was significantly lower in the second wave, while duration of ECMO run was longer (12.0 d [18.0-30.0 d] vs 29.5 d [15.5-58.3 d]; p = 0.005). Wave 2 patients had longer application of noninvasive ventilation (NIV) prior to ECMO and a higher frequency of barotrauma. Patient age and NIV use were independently associated with increased mortality (odds ratio 1.07 [1.01-1.14]; p = 0.025 and 3.37 [1.12-12.60]; p = 0.043, respectively). QOL and lung function apart from transfer coefficient of carbon monoxide corrected for hemoglobin was similar at follow-up across the waves. CONCLUSIONS: Most patients with COVID-19 supported on ECMO in both waves survived in the short and longer term. At follow-up patients had similar lung function and QOL across the two waves. This suggests that ECMO has an ongoing role in the management of a carefully selected group of patients with COVID-19.

Pulmonary hypertension: the hallmark of acute COVID-19 microvascular angiopathy?

In situ pulmonary arterial thrombosis in COVID-19 is not visible on CTPA. However, the presence of CT-measured right heart and pulmonary artery dilatation in COVID-19 is likely attributable to this process and may be a possible surrogate for its detection. https://bit.ly/3g7z5TV.

COVID-protected pathways for image-guided lung cancer intervention during the COVID-19 pandemic: A cohort study.

OBJECTIVES: To compare the experience of COVID-protected and mixed cohort pathways in COVID-19 transmission at a tertiary referral hospital for elective CT-guided lung biopsy and ablation during the COVID-19 pandemic. METHODS: From September 2020 to August 2021, patients admitted for elective thoracic intervention were treated at a tertiary hospital (Site 1). Site 1 received patients for extracorporeal membrane oxygenation (ECMO) and invasive ventilation in the treatment of COVID-19. Shared imaging, theater, and hallway facilities were used.From April 2020 to August 2020, patients admitted for elective thoracic intervention were treated at a COVID-protected hospital (Site 2). No patients with suspected or confirmed COVID-19 were treated at Site 2.Patients were surveyed for clinical and laboratory signs of COVID-19 infection up to 30 days post-procedure. RESULTS: At Sites 1 and 2, patients (2.4%) were tested positive for COVID-19 at 10 and 14 days post-procedure.At Site 2, there were no COVID-19 positive cases within 30 days of undergoing elective thoracic intervention. CONCLUSION: A mixed-site method for infection control could represent a pragmatic approach to the management of elective procedures during the COVID-19 pandemic or for similar illnesses. ADVANCES IN KNOWLEDGE: Mixed-cohort infection control is possible in the prevention of nosocomial COVID-19 infection.

Dual-energy Computed Tomographic Pulmonary Angiography Accurately Estimates Lobar Perfusion Before Lung Volume Reduction for Severe Emphysema.

PURPOSE: To assess if dual-energy computed tomographic pulmonary angiography (DECTPA) derived lobar iodine quantification can provide an accurate estimate of lobar perfusion in patients with severe emphysema, and offer an adjunct to single-photon emission CT perfusion scintigraphy (SPECT-PS) in assessing suitability for lung volume reduction (LVR). MATERIALS AND METHODS: Patients with severe emphysema (forced expiratory volume in 1 s <49% predicted) undergoing evaluation for LVR between May 2018 and April 2020 imaged with both SPECT-PS and DECTPA were included in this retrospective study. DECTPA perfused blood volume maps were automatically segmented and lobar iodine mass was estimated and compared with lobar technetium (Tc99m) distribution acquired with SPECT-PS. Pearson correlation and Bland-Altman analysis were used for intermodality comparison between DECTPA and SPECT-PS. Univariate and adjusted multivariate linear regression were modelled to ascertain the effect sizes of possible confounders of disease severity, sex, age, and body mass index on the relationship between lobar iodine and Tc99m values. Effective radiation dose and adverse reactions were recorded. RESULTS: In all, 123 patients (64.5±8.8 y, 71 men; mean predicted forced expiratory volume in 1 s 32.1 ±12.7%,) were eligible for inclusion. There was a linear relationship between lobar perfusion values acquired using DECTPA and SPECT-PS with statistical significance ( P <0.001). Lobar relative perfusion values acquired using DECTPA and SPECT-PS had a consistent relationship both by linear regression and Bland-Altman analysis (mean bias, -0.01, mean r2 0.64; P <0.0001). Individual lobar comparisons demonstrated moderate correlation ( r =0.79, 0.78, 0.84, 0.78, 0.8 for the right upper, middle, lower, left upper, and lower lobes, respectively, P <0.0001). The relationship between lobar iodine and Tc99m values was not significantly altered after controlling for confounders including symptom and disease severity, age, sex, and body mass index. CONCLUSIONS: DECTPA provides an accurate estimation of lobar perfusion, showing good agreement with SPECT-PS and could potentially streamline preoperative assessment for LVR.

Persistent isolated impairment of gas transfer following COVID-19 pneumonitis relates to perfusion defects on dual-energy computed tomography.

A novel iodine perfusion score correlates with breathlessness and D LCO in patients post-#COVID19 without obvious interstitial disease on CT, suggesting that lung perfusion assessment may be useful in patients without another cause of dyspnoea https://bit.ly/3U6E2f5.

Implications of incidental findings from lung screening for primary care: data from a UK pilot.

Regional lung cancer screening (LCS) is underway in England, involving a "lung health check" (LHC) and low-dose CT scan for those at high risk of cancer. Incidental findings from LHCs or CTs are usually referred to primary care. We describe the proportion of participants referred from the West London LCS pilot to primary care, the indications for referral, the number of general practitioner (GP) attendances and consequent changes to patient management, and provide an estimated cost-burden analysis for primary care. A small proportion (163/1542, 10.6%) of LHC attendees were referred to primary care, primarily for suspected undiagnosed chronic obstructive pulmonary disease (55/163, 33.7%) or for QRISK® (63/163, 38.7%) assessment. Ninety one of 159 (57.2%) participants consenting to follow-up attended GP appointments; costs incurred by primary care were estimated at £5.69/LHC participant. Patient management changes occurred in only 36/159 (22.6%) referred participants. LHCs result in a small increase to primary care workload provided a strict referral protocol is adhered to. Changes to patient management arising from incidental findings referrals are infrequent.

Prevalence of Thrombotic Complications in ICU-Treated Patients With Coronavirus Disease 2019 Detected With Systematic CT Scanning.

OBJECTIVES: Severe coronavirus disease 2019 is associated with an extensive pneumonitis and frequent coagulopathy. We sought the true prevalence of thrombotic complications in critically ill patients with severe coronavirus disease 2019 on the ICU, with or without extracorporeal membrane oxygenation. DESIGN: We undertook a single-center, retrospective analysis of 72 critically ill patients with coronavirus disease 2019-associated acute respiratory distress syndrome admitted to ICU. CT angiography of the thorax, abdomen, and pelvis were performed at admission as per routine institution protocols, with further imaging as clinically indicated. The prevalence of thrombotic complications and the relationship with coagulation parameters, other biomarkers, and survival were evaluated. SETTING: Coronavirus disease 2019 ICUs at a specialist cardiorespiratory center. PATIENTS: Seventy-two consecutive patients with coronavirus disease 2019 admitted to ICU during the study period (March 19, 2020, to June 23, 2020). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: All but one patient received thromboprophylaxis or therapeutic anticoagulation. Among 72 patients (male:female = 74%; mean age: 52 ± 10; 35 on extracorporeal membrane oxygenation), there were 54 thrombotic complications in 42 patients (58%), comprising 34 pulmonary arterial (47%), 15 peripheral venous (21%), and five (7%) systemic arterial thromboses/end-organ embolic complications. In those with pulmonary arterial thromboses, 93% were identified incidentally on first screening CT with only 7% suspected clinically. Biomarkers of coagulation (e.g., d-dimer, fibrinogen level, and activated partial thromboplastin time) or inflammation (WBC count, C-reactive protein) did not discriminate between patients with or without thrombotic complications. Fifty-one patients (76%) survived to discharge; 17 (24%) patients died. Mortality was significantly greater in patients with detectable thrombus (33% vs 10%; p = 0.022). CONCLUSIONS: There is a high prevalence of thrombotic complications, mainly pulmonary, among coronavirus disease 2019 patients admitted to ICU, despite anticoagulation. Detection of thrombus was usually incidental, not predicted by coagulation or inflammatory biomarkers, and associated with increased risk of death. Systematic CT imaging at admission should be considered in all coronavirus disease 2019 patients requiring ICU.

Imaging of Cardiac Infections: A Comprehensive Review and Investigation Flowchart for Diagnostic Workup.

Infections of the cardiovascular system may present with nonspecific symptoms, and it is common for patients to undergo multiple investigations to arrive at the diagnosis. Echocardiography is central to the diagnosis of endocarditis and pericarditis. However, cardiac computed tomography (CT) and magnetic resonance imaging also play an additive role in these diagnoses; in fact, magnetic resonance imaging is central to the diagnosis of myocarditis. Functional imaging (fluorine-18 fluorodeoxyglucose-positron emission tomography/CT and radiolabeled white blood cell single-photon emission computed tomography/CT) is useful in the diagnosis in prosthesis-related and disseminated infection. This pictorial review will detail the most commonly encountered cardiovascular bacterial and viral infections, including coronavirus disease-2019, in clinical practice and provide an evidence basis for the selection of each imaging modality in the investigation of native tissues and common prostheses.

Baseline Results of the West London lung cancer screening pilot study - Impact of mobile scanners and dual risk model utilisation.

OBJECTIVES: The West London lung screening pilot aimed to identify early-stage lung cancer by targeting low-dose CT (LDCT) to high risk participants. Successful implementation of screening requires maximising participant uptake and identifying those at highest risk. As well as reporting pre-specified baseline screening metrics, additional objectives were to 1) compare participant uptake between a mobile and hospital-based CT scanner and 2) evaluate the impact on cancer detection using two lung cancer risk models. METHODS: From primary care records, ever-smokers aged 60-75 were invited to a lung health check at a hospital or mobile site. Participants with PLCOM2012 6-yr risk ≥1.51 % and/or LLPv2 5-yr risk ≥2.0 % were offered a LDCT. Lung cancer detection rate, stage, and recall rates are reported. Participant uptake was compared at both sites (chi-squared test). LDCT eligibility and cancer detection rate were compared between those recruited under each risk model. RESULTS: Of 8366 potential participants invited, 1047/5135 (20.4 %) invitees responded to an invitation to the hospital site, and 702/3231 (21.7 %) to the mobile site (p = 0.14). The median distance travelled to the hospital site was less than to the mobile site (3.3 km vs 6.4 km, p < 0.01). Of 1159 participants eligible for a scan, 451/1159 (38.9 %) had a LLPv2 ≥2.0 % only, 71/1159 (6.1 %) had a PLCOM2012 ≥1.5 % only; 637/1159 (55.0 %) met both risk thresholds. Recall rate was 15.9 %. Lung cancer was detected in 29/1145 (2.5 %) participants scanned (stage 1, 58.6 %); 5/29 participants with lung cancer did not meet a PLCOM2012 threshold of ≥1.51 %; all had a LLPv2 ≥2.0 %. CONCLUSION: Targeted screening is effective in detecting early-stage lung cancer. Similar levels of participant uptake at a mobile and fixed site scanner were demonstrated, indicating that uptake was driven by factors in addition to scanner location. The LLPv2 model was more permissive; recruitment with PLCOM2012 alone would have missed several cancers.