John T. Murchison

Bone attenuation on routine chest CT correlates with bone mineral density on DXA in patients with COPD

Chronic obstructive pulmonary disease (COPD), although primarily a disease of the lungs, is associated with extrapulmonary effects such as muscle weakness and osteoporosis. Fractures owing to osteoporosis cause significant morbidity and mortality, particularly in patients with COPD. To prevent osteoporotic fractures, it is important to diagnose osteoporosis in an early stage and to start anti‐osteoporotic therapy in at‐risk patients. Because routine chest computed tomography (CT) is increasingly used to assess the extent of emphysema and airways disease in patients with COPD, we investigated whether simple attenuation measurement of the thoracic spine on routine chest CT may provide useful information on bone health in patients with COPD. Fifty‐eight patients with moderate to very severe COPD were included in our study. The average attenuation of thoracic vertebrae 4, 7, and 10 on chest CT was correlated with the lowest bone mineral density (BMD) of the hip and lumbar spine (L1 to L4) on dual‐energy X‐ray absorptiometry (DXA) in patients with COPD. The inter‐ and intra‐observer variabilities of the attenuation measurements were low as shown by Bland‐Altman plots. Pearsons correlation coefficient between the average attenuation of the three thoracic vertebrae and the lowest BMD of the hip and lumbar spine was high (ru2009=u20090.827, pu2009<u20090.001). A receiver‐operating characteristic (ROC) analysis of the area under the curve for osteoporosis was 0.969 (pu2009<u20090.001), corresponding to an attenuation threshold of 147 Hounsfield Units (HU). In conclusion, our data demonstrated that bone attenuation measured on routine chest CT correlated strongly with BMD assessed on DXA in patients with COPD. Routine chest CT may provide useful information on bone health in patients with COPD.

Chronic Pleuropulmonary Fibrosis and Elastosis of Aged Donkeys: Similarities to Human Pleuroparenchymal Fibroelastosis

BACKGROUNDnDonkey pulmonary fibrosis (DPF) is a spontaneous syndrome of aged donkeys with a high prevalence (35%). No previous detailed characterization of DPF has been performed. We sought to determine the similarities between DPF and recognized patterns of human pulmonary fibrosis.nnnMETHODSnWhole lungs were collected from 32 aged donkeys at routine necropsy. Gross examination revealed pulmonary fibrosis in 19 donkeys (DPF cases), whereas 13 (control cases) had grossly normal lungs. Eighteen whole inflated ex vivo lungs (11 DPF cases, seven control cases) were imaged with high-resolution CT (HRCT) scan, whereas the remainder were sectioned and photographed. Tissue samples were collected from all lungs for histopathologic evaluation using a standardized protocol. HRCT images and histology sections underwent independent blinded review. Lung tissue was analyzed for herpes virus, fungal hyphae, mycobacteria, and dust content.nnnRESULTSnTen of 19 DPF lungs were categorized as being consistent with pleuroparenchymal fibroelastosis (PPFE) according to previously defined histologic and imaging criteria. All 10 PPFE-like lungs had marked pleural and subpleural fibrosis, predominantly within the upper lung zone, with accompanying intraalveolar fibrosis and elastosis. Asinine herpesvirus was ubiquitously expressed within control and DPF lung tissue. No other etiologic agents were identified.nnnCONCLUSIONSnMany cases of DPF share key pathologic and imaging features with human PPFE, a rare interstitial pneumonia. Consequently, further study of DPF may help to elucidate the etiopathogenesis of human PPFE.

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

OBJECTIVESnThe 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.nnnMETHODSn2425 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 Pearsons rank correlation.nnnRESULTSnIncreasing 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).nnnCONCLUSIONnWith 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.

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

AIMnTo 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.nnnMATERIALS AND METHODSnIn 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.nnnRESULTSnFrom 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.nnnCONCLUSIONSnIncreased 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.

Lung cancer screening: Computed tomography or chest radiographs?

Worldwide, lung cancer is the leading cause of mortality due to malignancy. The vast majority of cases of lung cancer are smoking related and the most effective way of reducing lung cancer incidence and mortality is by smoking cessation. In the Western world, smoking cessation policies have met with limited success. The other major means of reducing lung cancer deaths is to diagnose cases at an earlier more treatable stage employing screening programmes using chest radiographs or low dose computed tomography. In many countries smoking is still on the increase, and the sheer scale of the problem limits the affordability of such screening programmes. This short review article will evaluate the current evidence and potential areas of research which may benefit policy making across the world.

Feasibility of radiation dose reduction using AIDR-3D in dynamic pulmonary CT perfusion.

AIMnTo assess the feasibility of radiation dose reduction with adaptive iterative dose reduction (AIDR-6 3D) reconstruction in dynamic pulmonary CT perfusion.nnnMATERIALS AND METHODSnCTP examinations of 10 patients acquired at 100 kVp/50 mAs were reconstructed with filtered back projection (FBP) and AIDR-3D. Artificial noise was added to raw data (pre-reconstruction projection data) to simulate lower tube current scanning. Radiodensity (in Hounsfield units), noise, and perfusion values were compared.nnnRESULTSnThere was no significant difference in noise between the full and simulated reduced tube current with AIDR-3D reconstruction (p = 1). There was significantly lower noise in lung tissue with AIDR-3D images when compared to reconstructions without AIDR-3D (p = 0.005) and no significant change in the radiodensity (p = 1; mean difference <6 HU). Mean perfusion values increased significantly at lower tube currents (25 and 12.5 mAs), compared to 50 mAs (p = 0.005). This effect was significantly greater in larger patients compared to thin patients.nnnCONCLUSIONnAIDR-3D produced significantly lower noise images than FBP-based algorithms and maintained consistent noise levels in lung at 12.5 mAs, indicating this algorithm is suitable for reduced dose lung perfusion imaging. Iterative reconstruction allows significant radiation dose reduction of up to fourfold in smaller patients, and up to twofold in the medium/large size patients. The increase in perfusion values at 25% simulated tube currents is attributed to attenuation bias.

Crowdsourcing Labels for Pathological Patterns in CT Lung Scans: Can Non-experts Contribute Expert-Quality Ground Truth?

This paper investigates what quality of ground truth might be obtained when crowdsourcing specialist medical imaging ground truth from non-experts. Following basic tuition, 34 volunteer participants independently delineated regions belonging to 7 pathological patterns in 20 scans according to expert-provided pattern labels. Participants’ annotations were compared to a set of reference annotations using Dice similarity coefficient (DSC), and found to range between 0.41 and 0.77. The reference repeatability was 0.81. Analysis of prior imaging experience, annotation behaviour, scan ordering and time spent showed that only the last was correlated with annotation quality. Multiple observers combined by voxelwise majority vote outperformed a single observer, matching the reference repeatability for 5 of 7 patterns. In conclusion, crowdsourcing from non-experts yields acceptable quality ground truth, given sufficient expert task supervision and a sufficient number of observers per scan.

Imaging of acute respiratory distress syndrome

IMPORTANCE OF THE FIELDnAcute respiratory distress syndrome (ARDS) describes a relatively common and frequently lethal syndrome at the severe end of the spectrum of acute lung injury. Onset of symptoms is usually within 72 h of the inciting event and complicates a wide variety of clinical disorders, ranging from infection to trauma. It may be defined as resistant hypoxaemia in the clinical setting of one of the group of recognised causes, in association with bilateral pulmonary infiltrates and in the absence of left atrial hypertension. Accurate diagnosis and differentiation from other treatable conditions is crucial.nnnAREAS COVERED IN THIS REVIEWnThis publication addresses the clinical and radiological features of ARDS, a review of the imaging technology with illustrations and differential diagnosis.nnnWHAT THE READER WILL GAINnThis paper will give insight into the strengths and weaknesses of imaging modalities used in the management of patients with ARDS.nnnTAKE HOME MESSAGEnImaging plays a vital role in the assessment of acute respiratory syndromes. Computed tomography is much more sensitive compared with chest radiography, and relatively under-utilised. Other methods, such as bedside ultrasound and impedance tomography, may have roles to play in the future.

Nebulisation of synthetic lamellar lipids mitigates radiation-induced lung injury in a large animal model

Methods to protect against radiation-induced lung injury (RILI) will facilitate the development of more effective radio-therapeutic protocols for lung cancer and may provide the means to protect the wider population in the event of a deliberate or accidental nuclear or radiological event. We hypothesised that supplementing lipid membranes through nebulization of synthetic lamellar lipids would mitigate RILI. Following pre-treatment with either nebulised lamellar lipids or saline, anaesthetised sheep were prescribed fractionated radiotherapy (30 Gray (Gy) total dose in five 6u2009Gy fractions at 3–4 days intervals) to a defined unilateral lung volume. Gross pathology in radio-exposed lung 37 days after the first radiation treatment was consistent between treatment groups and consisted of deep red congestion evident on the pleural surface and firmness on palpation. Consistent histopathological features in radio-exposed lung were subpleural, periarteriolar and peribronchial intra-alveolar oedema, alveolar fibrosis, interstitial pneumonia and type II pneumocyte hyperplasia. The synthetic lamellar lipids abrogated radiation-induced alveolar fibrosis and reduced alpha-smooth muscle actin (ASMA) expression in radio-exposed lung compared to saline treated sheep. Administration of synthetic lamellar lipids was also associated with an increased number of cells expressing dendritic cell-lysosomal associated membrane protein throughout the lung.

P178 5 year follow up of patients investigated for suspected pe. what further tests for suspected vte are performed and are they positive

The diagnosis of a Pulmonary Embolism (PE) is a challenging clinical problem, our approach to which has changed greatly since the introduction of Computed tomographic pulmonary angiography (CTPA). CTPA is now established as the imaging modality of choice for the diagnosis of PE, however there are concerns that CTPA causes the over-diagnosis of clinically irrelevant PE,1,2 and there is little data concerning the outcomes and further imaging following a CTPA at long follow-up times. Here we present long term follow-up of CTPAs over 5 years, looking at further imaging related to suspected thromboembolic disease after more than 2000 studies. After their initial CTPA, further studies were documented retrospectively using electronic patient records. Figure 1 demonstrates what further imaging for suspected venous thromboembolic event (VTE) patients had following their CTPAs scans over 5 years. In a one-year period, 24% of the negative studies, 38% of the positive, and 50% of the indeterminate studies had repeat testing for suspected thromboembolic disease. Indeterminate studies received repeat testing faster (p<0.001), and those with negative studies received fewer repeat tests (p<0. 001). Those with a positive initial result were more likely to have positive recurrent testing over the whole 5u2009year period, and these data also suggest a trend showing increased risk with positive PEs rather than other VTEs. Furthermore, although CTPAs had a very high calculated negative predictive value for excluding PE (over 99%), many patients went on to have repeat testing following a negative result. Understanding how test Results influence the predictive value of further testing is essential for effective risk stratification, and this work adds to the growing body of data examining the long-term implications of a CTPA result. Abstract P178 Figure 1 References Wiener RS, Schwartz LM, Woloshin S. Time trends in pulmonary embolism in the United States: Evidence of overdiagnosis. Arch Intern Med. American Medical Association2011;171(9):831–7. Morley NCD, Muir KC, Mirsadraee S, van Beek EJR, Murchison JT. Ten years of imaging for pulmonary embolism: Too many scans or the tip of an iceberg?Clin Radiol: Elsevier2015.