Validation study of machine-learning chest radiograph software in primary and emergency medicine.

AIM: To evaluate the performance of a machine learning based algorithm tool for chest radiographs (CXRs), applied to a consecutive cohort of historical clinical cases, in comparison to expert chest radiologists. MATERIALS AND METHODS: The study comprised 1,960 consecutive CXR from primary care referrals and the emergency department (992 and 968 cases respectively), obtained in 2015 at a UK hospital. Two chest radiologists, each with >20 years of experience independently read all studies in consensus to serve as a reference standard. A chest artificial intelligence (AI) algorithm, Lunit INSIGHT CXR, was run on the CXRs, and results were correlated with those by the expert readers. The area under the receiver operating characteristic curve (AUROC) was calculated for the normal and 10 common findings: atelectasis, fibrosis, calcification, consolidation, lung nodules, cardiomegaly, mediastinal widening, pleural effusion, pneumothorax, and pneumoperitoneum. RESULTS: The ground truth annotation identified 398 primary care and 578 emergency department datasets containing pathologies. The AI algorithm showed AUROC of 0.881-0.999 in the emergency department dataset and 0.881-0.998 in the primary care dataset. The AUROC for each of the findings between the primary care and emergency department datasets did not differ, except for pleural effusion (0.954 versus 0.988, p<0.001). CONCLUSIONS: The AI algorithm can accurately and consistently differentiate normal from major thoracic abnormalities in both acute and non-acute settings, and can serve as a triage tool.

Coronary artery calcification is associated with mortality independent of pulmonary embolism severity: a retrospective cohort study.

AIM: To assess coronary artery calcification (CAC) and vascular calcification in patients with pulmonary embolism (PE) and correlate this with mortality. MATERIALS AND METHODS: PE severity was quantified using computed tomography pulmonary angiography (CTPA) in 400 consecutive cases using the modified Miller score (1-5, mild; 6-11, moderate; 12-16, severe). Right ventricle strain was assessed using the right/left ventricle diameter (RV/LV) ratio. CAC score (CACS) was assessed using a four-point scale (CACS mild 1-3, moderate 4-8, severe 9-12) for each vessel and summed to give the total CACS. Follow-up for mortality was obtained at 3 years. RESULTS: PE severity was classified as mild in 48%, moderate in 21%, and severe in 32% of cases. The median modified Miller score was 6 (Interquartile range [IQR] 2, 14) and median total CACS was 2 (IQR 0, 7). All-cause mortality occurred in 128 (32%) patients. Patients with CAC were three times more likely to die than patients without CAC (Hazard ratio [HR] 2.96; 95% CI 1.84, 4.77; p<0.001), and patients with severe CAC were at the highest risk (HR 4.62; 95% CI 2.73, 7.83, p<0.001). Gender, modified Miller score and RV/LV ratio were not predictive of mortality. In multivariate analysis both CACS and age were independent predictors of 3-year all-cause mortality. Of the patients with CAC who died, the presence of coronary artery disease was only documented in 34 (32%). CONCLUSION: CACS is an independent predictor of all-cause mortality in patients with PE, and has important implications for subsequent patient management.

Positron Emission Tomography and Magnetic Resonance Imaging of Cellular Inflammation in Patients with Abdominal Aortic Aneurysms.

OBJECTIVES: Inflammation is critical in the pathogenesis of abdominal aortic aneurysm (AAA) disease. Combined (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography with computed tomography (PET-CT) and ultrasmall superparamagnetic particles of iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) are non-invasive methods of assessing tissue inflammation. The aim of this study was to compare these techniques in patients with AAA. MATERIALS AND METHODS: Fifteen patients with asymptomatic AAA with diameter 46 ± 7 mm underwent PET-CT with (18)F-FDG, and T2*-weighted MRI before and 24 hours after administration of USPIO. The PET-CT and MRI data were then co-registered. Standardised uptake values (SUVs) were calculated to measure (18)F-FDG activity, and USPIO uptake was determined using the change in R2*. Comparisons between the techniques were made using a quadrant analysis and a voxel-by-voxel evaluation. RESULTS: When all areas of the aneurysm were evaluated, there was a modest correlation between the SUV on PET-CT and the change in R2* on USPIO-enhanced MRI (n = 70,345 voxels; r = .30; p < .0001). Although regions of increased (18)F-FDG and USPIO uptake co-localised on occasion, this was infrequent (kappa statistic 0.074; 95% CI 0.026-0.122). (18)F-FDG activity was commonly focused in the shoulder region whereas USPIO uptake was more apparent in the main body of the aneurysm. Maximum SUV was lower in patients with mural USPIO uptake. CONCLUSIONS: Both (18)F-FDG PET-CT and USPIO-MRI uptake identify vascular inflammation associated with AAA. Although they demonstrate a modest correlation, there are distinct differences in the pattern and distribution of uptake, suggesting a differential detection of macrophage glycolytic and phagocytic activity respectively.

Long-term adverse effects associated with isolated below-knee deep-vein thrombosis: a 10-year follow-up study.

AIM: To assess the effect of the presence and locality of symptomatic lower-limb deep vein thrombosis (DVT) on mortality and morbidity following contrast venography (CV), the reference standard for diagnosing below-knee DVT, with a view to determining the prevalence of recurrent episodes of DVT and post-thrombotic syndrome (PTS). MATERIALS AND METHODS: Patients with clinical DVT undergoing investigation using CV were prospectively recorded. By retrospective case note examination and mortality data evaluation, 347 patients with DVT were matched with negative controls for mortality follow-up. Long-term complications were recorded. RESULTS: Fifty-one (14.7%) of the DVT patients were diagnosed with PTS and 43 (12.4%) with possible PTS in the 10 years following presentation. The relative risk for developing definite PTS was 0.544 for below- versus above-knee DVT; 9.9% with below-knee DVT had PTS, and 9% had probable PTS. Recurrent DVT occurred in 23.3% of patients with proximal DVT as opposed to 12.6% of patients with isolated below-knee DVT. CONCLUSIONS: Morbidity is greater in patients with proximal DVT; however, a significant, albeit smaller, proportion of patients with isolated below-knee DVT develop recurrent DVT and PTS. Below-knee DVT carries sufficient morbidity and mortality to warrant vigilance in diagnosis and management of this condition.

Ten years of imaging for pulmonary embolism: too many scans or the tip of an iceberg?

AIM: To examine the number and nature of investigations performed for suspected pulmonary embolism (PE) in a large teaching hospital and the change in incidence and severity of PE over a decade. MATERIALS AND METHODS: In this retrospective study, all patients investigated for suspected PE using computed tomography pulmonary angiography (CTPA) or lung scintigraphy during 10 years to March 2012 were identified and their records reviewed. In the final year, all reportedly positive CTPA cases were reviewed and PE severity calculated, for comparison with similar historical data. RESULTS: From 2002 to 2012, total annual investigations for suspected acute PE increased by 163% (805 to 2121). CTPA increased by 325% (475 to 2019). Detection of PE increased by 121% (193 to 426 per annum), with stable distribution of severity scores. The positive scan rate decreased from 24% to 20%. The mean age of patients being investigated for PE increased from 56 to 63 years. CONCLUSIONS: Increased detection of PE is not due to disproportionate increase in small PEs, but to increased detection of PE of all severities. This finding supports the hypothesis that PE is more common in the general population than previously appreciated, which may represent an iceberg phenomenon of previously undetected disease.

Imaging of cardiovascular risk in patients with Turner's syndrome.

Turner's syndrome is a disorder defined by an absent or structurally abnormal second X chromosome and affects around 1 in 2000 newborn females. The standardised mortality ratio in Turner's syndrome is around three-times higher than in the general female population, mainly as a result of cardiovascular disorders. Most striking is the early age at which Turner's syndrome patients develop the life-threatening complications of cardiovascular disorders compared to the general population. The cardiovascular risk stratification in Turner's syndrome is challenging and imaging is not systematically used. The aim of this article is to review cardiovascular risks in this group of patients and discuss a systematic imaging approach for early identification of cardiovascular disorders in these patients.

Aortic stenosis, atherosclerosis, and skeletal bone: is there a common link with calcification and inflammation?

AIMS: The pathophysiology of aortic stenosis shares many similarities with atherosclerosis and skeletal bone formation. Using non-invasive imaging, we compared aortic valve calcification and inflammation activity with that measured in atherosclerosis and bone. METHODS AND RESULTS: Positron emission and computed tomography was performed using 18F-sodium fluoride (18F-NaF, calcification) and 18F-fluorodeoxyglucose (18F-FDG, inflammation) in 101 patients with calcific aortic valve disease (81 aortic stenosis and 20 aortic sclerosis). Calcium scores and positron emission tomography tracer activity (tissue-to-background ratio; TBR) were measured in the aortic valve, coronary arteries, thoracic aorta, and bone. Over 90% of the cohort had coexistent calcific atheroma, yet correlations between calcium scores were weak or absent (valve vs. aorta r(2) = 0.015, P = 0.222; valve vs. coronaries r(2) = 0.039, P = 0.049) as were associations between calcium scores and bone mineral density (BMD vs. valve r(2) = 0.000, P = 0.766; vs. aorta r(2) = 0.052, P = 0.025; vs. coronaries r(2) = 0.016, P = 0.210). 18F-NaF activity in the valve was 28% higher than in the aorta (TBR: 2.66 ± 0.84 vs. 2.11 ± 0.31, respectively, P < 0.001) and correlated more strongly with the severity of aortic stenosis (r(2) = 0.419, P < 0.001) than 18F-NaF activity outwith the valve (valve vs. aorta r(2) = 0.167, P < 0.001; valve vs. coronary arteries r(2) = 0.174, P < 0.001; valve vs. bone r(2) = 0.001, P = 0.806). In contrast, 18F-FDG activity was lower in the aortic valve than the aortic atheroma (TBR: 1.56 ± 0.21 vs. 1.81 ± 0.24, respectively, P < 0.001) and more closely associated with uptake outwith the valve (valve vs. aorta r(2) = 0.327, P < 0.001). CONCLUSION: In patients with aortic stenosis, disease activity appears to be determined by local calcific processes within the valve that are distinct from atherosclerosis and skeletal bone metabolism.

Iterative reconstruction and individualized automatic tube current selection reduce radiation dose while maintaining image quality in 320-multidetector computed tomography coronary angiography.

AIM: To assess the effect of two iterative reconstruction algorithms (AIDR and AIDR3D) and individualized automatic tube current selection on radiation dose and image quality in computed tomography coronary angiography (CTCA). MATERIALS AND METHODS: In a single-centre cohort study, 942 patients underwent electrocardiogram-gated CTCA using a 320-multidetector CT system. Images from group 1 (n = 228) were reconstructed with a filtered back projection algorithm (Quantum Denoising Software, QDS+). Iterative reconstruction was used for group 2 (AIDR, n = 379) and group 3 (AIDR3D, n = 335). Tube current was selected based on body mass index (BMI) for groups 1 and 2, and selected automatically based on scout image attenuation for group 3. Subjective image quality was graded on a four-point scale (1 = excellent, 4 = non-diagnostic). RESULTS: There were no differences in age (p = 0.975), body mass index (p = 0.435), or heart rate (p = 0.746) between the groups. Image quality improved with iterative reconstruction and automatic tube current selection [1.3 (95% confidence intervals (CI): 1.2-1.4), 1.2 (1.1-1.2) and 1.1 (1-1.2) respectively; p < 0.001] and radiation dose decreased [274 (260-290), 242 (230-253) and 168 (156-180) mGy cm, respectively; p < 0.001]. CONCLUSION: The application of the latest iterative reconstruction algorithm and individualized automatic tube current selection can substantially reduce radiation dose whilst improving image quality in CTCA.

Hyperpolarised 3He MRI versus HRCT in COPD and normal volunteers: PHIL trial.

The aim of the present study was to apply hyperpolarised (HP) (3)He magnetic resonance imaging (MRI) to identify patients with chronic obstructive pulmonary disease (COPD) and alpha(1)-antitrypsin deficiency (alpha(1)-ATD) from healthy volunteers and compare HP (3)He MRI findings with high-resolution computed tomography (HRCT) in a multicentre study. Quantitative measurements of HP (3)He MRI (apparent diffusion coefficient (ADC)) and HRCT (mean lung density (MLD)) were correlated with pulmonary function tests. A prospective three centre study enrolled 122 subjects with COPD (either acquired or genetic) and age-matched never-smokers. All diagnostic studies were completed in 94 subjects (52 with COPD; 13 with alpha(1)-ATD; 29 healthy subjects; 63 males; and 31 females; median age 62 yrs). The consensus assessment of radiologists, blinded for other test results, estimated nonventilated lung volume (HP (3)He MRI) and percentage diseased lung (HRCT). Quantitative evaluation of all data for each centre consisted of ADC (HP (3)He MRI) and MLD measurements (HRCT), and correlation with forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) indicating airway obstruction, and the diffusing capacity of the lung for carbon monoxide (D(L,CO)) indicating alveolar destruction. Using lung function tests as a reference, regional analysis of HP (3)He MRI and HRCT correctly categorised normal volunteers in 100% and 97%, COPD in 42% and 69% and alpha(1)-ATD in 69% and 85% of cases, respectively. Direct comparison of HP (3)He MRI and CT revealed 23% of subjects with moderate/severe structural abnormalities had only mild ventilation defects. In comparison with lung function tests, ADC was more effective in separating COPD patients from healthy subjects than MLD (p<0.001 versus 0.038). ADC measurements showed better correlation with D(L,CO) than MLD (r = 0.59 versus 0.29). Hyperpolarised (3)He MRI correctly categorised patients with COPD and normal volunteers. It offers additional functional information, without the use of ionising radiation whereas HRCT gives better morphological information. We showed the feasibility of a multicentre study using different magnetic resonance systems.

PET scan in clinically suspected paraneoplastic neurological syndromes: a 6-year prospective study in a regional neuroscience unit.

BACKGROUND: The role of PET in the diagnosis of paraneoplastic neurological syndromes (PNS) has previously been reported in retrospective studies, from specialized neuro-oncology units, often selecting patients with positive paraneoplastic antibodies. OBJECTIVES: To prospectively assess the usefulness of PET in detecting malignancy in patients clinically suspected of having PNS. METHODS: PET was performed in patients suspected of PNS within 4 weeks of the normal CT body scan. All patients were followed up. RESULTS: Eighty patients suspected of having PNS underwent PET. 18/80 (23%) were abnormal and suspicious of malignancy. The total number of definite and probable PNS with abnormal PET was 11/18 (61%). The total number of definite and probable PNS with a normal PET was 3/62 (5%). Only 50% of patients with biopsy-proven malignancy were positive for paraneoplastic antibodies. The prevalence of abnormal PET in patients presenting with classical PNS was 41% as opposed to 21% in patients with non-classical PNS. The sensitivity and specificity of PET in diagnosing PNS was 75% and 87% respectively. CONCLUSIONS: PET is a valuable tool in clinically suspected PNS. Its use should not be restricted to specialized neuro-oncology units or in patients with positive paraneoplastic antibodies. Positive yield is the highest amongst patients with classical PNS.

Multimodality quantitative assessments of myocardial perfusion using dynamic contrast enhanced magnetic resonance and 15O-labelled water positron emission tomography imaging.

Kinetic modelling of myocardial perfusion imaging data allows the absolute quantification of myocardial blood flow (MBF) and can improve the diagnosis and clinical assessment of coronary artery disease (CAD). Positron emission tomography (PET) imaging is considered the reference standard technique for absolute quantification, whilst oxygen-15 (15O)-water has been extensively implemented for MBF quantification. Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has also been used for MBF quantification and showed comparable diagnostic performance against (15O)-water PET studies. We investigated for the first time the diagnostic performance of two different PET MBF analysis softwares PMOD and Carimas, for obstructive CAD detection against invasive clinical standard methods in 20 patients with known or suspected CAD. Fermi and distributed parameter modelling-derived MBF quantification from DCE-MRI was also compared against (15O)-water PET, in a subgroup of 6 patients. The sensitivity and specificity for PMOD was significantly superior for obstructive CAD detection in both per vessel (0.83, 0.90) and per patient (0.86, 0.75) analysis, against Carimas (0.75, 0.65), (0.81, 0.70), respectively. We showed strong, significant correlations between MR and PET MBF quantifications (r=0.83-0.92). However, DP and PMOD analysis demonstrated comparable and higher haemodynamic differences between obstructive versus (no, minor or non)-obstructive CAD, against Fermi and Carimas analysis. Our MR method assessments against the optimum PET reference standard technique for perfusion analysis showed promising results in per segment level and can support further multi-modality assessments in larger patient cohorts. Further MR against PET assessments may help to determine their comparative diagnostic performance for obstructive CAD detection.

Efficacy and safety of gadodiamide (Gd-DTPA-BMA) in renal 3D-magnetic resonance angiography (MRA): a phase II study.

PURPOSE: To determine the most efficacious dose of gadodiamide for three-dimensional (3D) contrast-enhanced (CE) magnetic resonance angiography (MRA) of the renal arteries on a patient level based on the sensitivity in detecting the main hemodynamically relevant (> or =50% or occlusion) renal artery stenosis (RAS) using intra-arterial digital subtraction angiography (IA DSA) as the gold standard. MATERIALS AND METHODS: This prospective, randomized, double-blind, parallel-group, multicenter study included 273 patients referred to IA DSA for suspected RAS. Patients underwent 3D CE MRA after injection of 0.01, 0.05, 0.1, or 0.2mmol/kg of body weight gadodiamide (0.5mmol/ml). The images were assessed for location and degree of RAS by independent blinded readers (MRA: three readers, IA DSA: one reader). Hypothesis testing for a significant trend in sensitivity across dose groups was based on the one-sided Cochran-Armitage style trend test for each independent MRA reader. RESULTS: The lowest dose group (0.01mmol/kg) proved non-efficacious in detecting hemodynamically relevant (i.e., > or =50% or occlusion) RAS. A statistically significant dose trend (p<0.001) was shown for each of the three independent readers. Depending on reader, the sensitivity obtained with 0.05, 0.1, and 0.2mmol/kg was 63.9-86.1%, 75.8-91.4% and 80.6-90.6%, the specificity was 66.7-73.9%, 59.3-75.0%, and 59.3-75.0% and accuracy was 67.8-78.9%, 75.4-77.4%, and 76.3-81.0%, for the three dose groups, respectively. There were eight non-severe adverse events (AEs). Three serious AEs occurring in one patient were judged not related to gadodiamide by the on-site investigator. CONCLUSION: A significant dose trend between the four doses examined was observed. The lowest dose (0.01mmol/kg) differed significantly from those of the other three doses. Based on the analysis of the primary and secondary endpoints, 0.1mmol/kg gadodiamide appears to be the most suitable dose in diagnosing hemodynamically relevant RAS. The present study also demonstrated gadodiamide to be safe and well tolerated.

'Presenting CXR phenotype of H1N1' flu compared with contemporaneous non-H1N1, community acquired pneumonia, during pandemic and post-pandemic outbreaks'.

AIMS: To review, phenotype and assess potential prognostic value of initial chest X-ray findings in patients with H1N1 influenza during seasonal outbreaks of 2009 and 2010, in comparison with non-H1N1, community acquired pneumonia (CAP). METHODS: We retrospectively identified 72 patients admitted to hospital with pneumonia during the seasons of 2009 and 2010. H1N1 cases were confirmed by virology PCR. Presenting chest X-rays were jointly read by 2 radiologists, who were 'blinded' to further patient details and divided into 6 zones. Total number of opacified zones, the pattern and distribution of changes and length of hospital stay were recorded. RESULTS: Patients with H1N1 demonstrated more opacified zones (mean of 2.9 compared with 2.0; p=0.006), which were bilateral in two-thirds compared with a quarter of those with non-H1N1 CAP (p=0.001). H1N1 radiographs were more likely to be 'patchy' versus 'confluent' changes of non-H1N1 CAP (p=0.03) and more often demonstrated peripheral distribution (p=0.01). H1N1 patients tended to stay in hospital longer (not significant; p=0.08). A positive correlation existed between number of affected zones and length of inpatient stay, which was statistically significant for the cohorts combined (p=0.02). The findings were the same for the two evaluated seasons. CONCLUSION: H1N1 patients demonstrated more extensive disease, which was more likely bilateral, 'patchy', and peripheral in distribution. With increasing global cases of H1N1, knowledge of the typical findings of the H1N1 presenting chest X-ray may assist with early triage of patients, particularly where rapid viral testing is not available.

MR imaging of the lungs with hyperpolarized helium-3 gas transported by air.

Hyperpolarized noble gas MRI shows promise in the functional imaging of the pulmonary air spaces. The production of hyperpolarized (HP) gas requires specialized laser optical pumping apparatus, which is not likely to be home built in the majority of clinical MRI radiology centres. There are two routes through which HP gas will be made available to hospitals for clinical use: either the apparatus will be installed locally at a considerable expense to the centre, or a central facility will produce the gas and then deliver it to remote MRI sites as and when required. In this study, the feasibility of transporting large quantities of HP gas for in vivo MR imaging from a remote production facility in Mainz, Germany, by airfreight to Sheffield, UK, was successfully demonstrated.

Retinal imaging as a source of biomarkers for diagnosis, characterization and prognosis of chronic illness or long-term conditions.

The black void behind the pupil was optically impenetrable before the invention of the ophthalmoscope by von Helmholtz over 150 years ago. Advances in retinal imaging and image processing, especially over the past decade, have opened a route to another unexplored landscape, the retinal neurovascular architecture and the retinal ganglion pathways linking to the central nervous system beyond. Exploiting these research opportunities requires multidisciplinary teams to explore the interface sitting at the border between ophthalmology, neurology and computing science. It is from the detail and depth of retinal phenotyping that novel metrics and candidate biomarkers are likely to emerge. Confirmation that in vivo retinal neurovascular measures are predictive of microvascular change in the brain and other organs is likely to be a major area of research activity over the next decade. Unlocking this hidden potential within the retina requires integration of structural and functional data sets, that is, multimodal mapping and longitudinal studies spanning the natural history of the disease process. And with further advances in imaging, it is likely that this area of retinal research will remain active and clinically relevant for many years to come. Accordingly, this review looks at state-of-the-art retinal imaging and its application to diagnosis, characterization and prognosis of chronic illness or long-term conditions.

Computed tomographic measures of airway morphology in smokers and never-smoking normals.

Bronchial wall area percent (WA% = 100 × wall area/total bronchial cross sectional area) is a standard computed tomographic (CT) measure of central airway morphology utilized in smokers with chronic obstructive pulmonary disease (COPD). Although it provides significant clinical correlations, the range of reported WA% is narrow. This suggests limited macroscopic change in response to smoking or that remodeling proportionally affects the airway wall and lumen dimensions such that their ratio is preserved. The objective of this study is to assess central airway wall area (WA), lumen area (Ai), and total bronchial area (Ao) from CT scans of 5,179 smokers and 92 never smoking normal subjects. In smokers, WA, Ai, and Ao were positively correlated with forced expiratory volume in 1 s (FEV1) expressed as a percent of predicted (FEV1%), and the WA% was negatively correlated with FEV1% (P < 0.0001 for all comparisons). Importantly, smokers with lower FEV1% tended to have airways of smaller cross-sectional area with lower WA. The increases in the WA% across GOLD stages of chronic obstructive pulmonary disease (COPD) can therefore not be due to increases in WA. The data suggest two possible origins for the WA% increases: 1) central airway remodeling resulting in overall reductions in airway caliber in excess of the decreased WA or 2) those with COPD had smaller native airways before they began smoking. In both cases, these observations provide an explanation for the limited range of values of WA% across stages of COPD.

Thrombus load and acute right ventricular failure in pulmonary embolism: correlation and demonstration of a "tipping point" on CT pulmonary angiography.

OBJECTIVES: The aim of this study was to determine the correlation between increasing pulmonary embolism thrombus load and right ventricular (RV) dilatation as demonstrated by CT pulmonary angiography (CTPA) and to assess the thrombus load threshold which indicates impending RV decompensation. METHODS: 2425 consecutive CTPAs were retrospectively analysed. Thrombus load using a modified Miller score (MMS), RV to left ventricular (RV:LV) ratio, presence of septal shift, and pulmonary artery and aorta size were analysed in 504 positive CTPA scans and a representative cohort of 100 negative scans. Results were correlated using non-parametric analysis (two-tailed t-test or χ(2) test) and Pearson's rank correlation. RESULTS: Increasing thrombus load correlated with a higher RV:LV ratio, with a statistically significant difference in RV:LV ratios between the negative and positive pulmonary embolism (PE) cohorts. Larger thrombus loads (MMS ≥12 vs MMS <12) were strongly correlated with RV strain (mean RV:LV ratio, 1.323 vs 0.930; p<0.0001). Smaller thrombus loads had no significant influence on RV strain. Septal shift was also more likely with an MMS of ≥12, as was an increase in pulmonary artery diameter (r=0.221, p<0.001). CONCLUSION: With increasing thrombus load in PE, there is CTPA evidence of RV decompensation with an MMS threshold of 12. This suggests a "tipping point" beyond which RV decompensation is more likely to occur. This is the first study to describe this tipping point between a thrombus load of MMS >12 and an increase in RV:LV ratio. This finding may help to improve risk stratification in patients with acute PE diagnosed by CTPA.

MRI of the lung (2/3). Why when how?

BACKGROUND: Among the modalities for lung imaging, proton magnetic resonance imaging (MRI) has been the latest to be introduced into clinical practice. Its value to replace X-ray and computed tomography (CT) when radiation exposure or iodinated contrast material is contra-indicated is well acknowledged: i.e. for paediatric patients and pregnant women or for scientific use. One of the reasons why MRI of the lung is still rarely used, except in a few centres, is the lack of consistent protocols customised to clinical needs. METHODS: This article makes non-vendor-specific protocol suggestions for general use with state-of-the-art MRI scanners, based on the available literature and a consensus discussion within a panel of experts experienced in lung MRI. RESULTS: Various sequences have been successfully tested within scientific or clinical environments. MRI of the lung with appropriate combinations of these sequences comprises morphological and functional imaging aspects in a single examination. It serves in difficult clinical problems encountered in daily routine, such as assessment of the mediastinum and chest wall, and even might challenge molecular imaging techniques in the near future. CONCLUSION: This article helps new users to implement appropriate protocols on their own MRI platforms. Main Messages • MRI of the lung can be readily performed on state-of-the-art 1.5-T MRI scanners. • Protocol suggestions based on the available literature facilitate its use for routine • MRI offers solutions for complicated thoracic masses with atelectasis and chest wall invasion. • MRI is an option for paediatrics and science when CT is contra-indicated.

MRI of the lung (3/3)-current applications and future perspectives.

BACKGROUND: MRI of the lung is recommended in a number of clinical indications. Having a non-radiation alternative is particularly attractive in children and young subjects, or pregnant women. METHODS: Provided there is sufficient expertise, magnetic resonance imaging (MRI) may be considered as the preferential modality in specific clinical conditions such as cystic fibrosis and acute pulmonary embolism, since additional functional information on respiratory mechanics and regional lung perfusion is provided. In other cases, such as tumours and pneumonia in children, lung MRI may be considered an alternative or adjunct to other modalities with at least similar diagnostic value. RESULTS: In interstitial lung disease, the clinical utility of MRI remains to be proven, but it could provide additional information that will be beneficial in research, or at some stage in clinical practice. Customised protocols for chest imaging combine fast breath-hold acquisitions from a "buffet" of sequences. Having introduced details of imaging protocols in previous articles, the aim of this manuscript is to discuss the advantages and limitations of lung MRI in current clinical practice. CONCLUSION: New developments and future perspectives such as motion-compensated imaging with self-navigated sequences or fast Fourier decomposition MRI for non-contrast enhanced ventilation- and perfusion-weighted imaging of the lung are discussed. Main Messages • MRI evolves as a third lung imaging modality, combining morphological and functional information. • It may be considered first choice in cystic fibrosis and pulmonary embolism of young and pregnant patients. • In other cases (tumours, pneumonia in children), it is an alternative or adjunct to X-ray and CT. • In interstitial lung disease, it serves for research, but the clinical value remains to be proven. • New users are advised to make themselves familiar with the particular advantages and limitations.

MRI of the lung (1/3): methods.

Proton magnetic resonance imaging (MRI) has recently emerged as a clinical tool to image the lungs. This paper outlines the current technical aspects of MRI pulse sequences, radiofrequency (RF) coils and MRI system requirements needed for imaging the pulmonary parenchyma and vasculature. Lung MRI techniques are presented as a "technical toolkit", from which MR protocols will be composed in the subsequent papers for comprehensive imaging of lung disease and function (parts 2 and 3). This paper is pitched at MR scientists, technicians and radiologists who are interested in understanding and establishing lung MRI methods. Images from a 1.5 T scanner are used for illustration of the sequences and methods that are highlighted. Main Messages • Outline of the hardware and pulse sequence requirements for proton lung MRI • Overview of pulse sequences for lung parenchyma, vascular and functional imaging with protons • Demonstration of the pulse-sequence building blocks for clinical lung MRI protocols.