Serial evaluation of high-resolution CT findings in patients with pneumonia in novel swine-origin influenza A (H1N1) virus infection

Objectives

The purpose of our study was to review the changes in the serial high-resolution CT (HRCT) findings from patients with novel swine-origin influenza A (H1N1) virus (S-OIV) infection.

Methods

HRCT findings of 70 patients with presumed or laboratory-confirmed novel S-OIV infection were reviewed. The pattern (consolidation, ground glass, fibrosis and air trapping), distribution and extent of abnormality of the lesions on the HRCT were evaluated at different time points. To assess changes that occurred over time, the CT scans in 56 patients were examined in sequence.

Results

The most common CT findings in patients with S-OIV infection are ground-glass opacities with or without consolidation at the first week. The abnormalities peaked at the second week and resolved after that time, which resulted in substantial reduced residual disease at 4 weeks or later. The development of fibrosis was noted in the first week and peaked at the third week of illness (34.7%), then decreased slowly after that time. The mean time of air trapping being noted after the onset of symptoms was 55.5±20.6 days. Comparing the findings of initial CT, most results (96.4%) of follow-up chest CT findings showed improvement (p<0.01).

Conclusion

The abnormalities of ground-glass opacities and/or consolidation on initial CT scans tended to resolve to fibrosis, which then resolved completely or displayed substantially reduced residual disease. HRCT may show more changes in disease progression and play an important role in the evaluation of severe S-OIV.A novel swine-origin influenza A (H1N1) virus (S-OIV) was first reported in Mexico and became rampant globally later on in spring 2009 [1]. The World Health Organization declared the first Phase 6 global influenza pandemic of the century on 11 June 2009 [2]. During peak periods of influenza in autumn to winter of that year, a proportion of patients developed severe acute respiratory distress syndrome (ARDS), and some died of the disease. Serial chest radiography has been the main technique in the initial investigation of patients with suspected H1N1. However, multislice CT (MSCT) scanning is more sensitive than chest radiography, providing more detailed radiological features. Previous studies have reported that the predominant CT findings of disease were unilateral or bilateral multifocal peribronchovascular and/or subpleural ground-glass opacities (GGOs) with or without consolidation [1,3]. Little is known, however, about sequential MSCT findings during the subsequent course of pneumonia with H1N1. The purpose of this study was to evaluate the radiological changes on serial thin-section chest CT scans in patients with H1N1 during the acute and convalescent periods of the illness.     

Novel Influenza A (H1N1) Virus Infection in Children: Chest Radiographic and CT Evaluation

Objective

The purpose of this study was to evaluate the chest radiographic and CT findings of novel influenza A (H1N1) virus infection in children, the population that is more vulnerable to respiratory infection than adults.

Materials and Methods

The study population comprised 410 children who were diagnosed with an H1N1 infection from August 24, 2009 to November 11, 2009 and underwent chest radiography at Dankook University Hospital in Korea. Six of these patients also underwent chest CT. The initial chest radiographs were classified as normal or abnormal. The abnormal chest radiographs and high resolution CT scans were assessed for the pattern and distribution of parenchymal lesions, and the presence of complications such as atelectasis, pleural effusion, and pneumomediastinum.

Results

The initial chest radiograph was normal in 384 of 410 (94%) patients and abnormal in 26 of 410 (6%) patients. Parenchymal abnormalities seen on the initial chest radiographs included prominent peribronchial marking (25 of 26, 96%), consolidation (22 of 26, 85%), and ground-glass opacities without consolidation (2 of 26, 8%). The involvement was usually bilateral (19 of 26, 73%) with the lower lung zone predominance (22 of 26, 85%). Atelectasis was observed in 12 (46%) and pleural effusion in 11 (42%) patients. CT (n = 6) scans showed peribronchovascular interstitial thickening (n = 6), ground-glass opacities (n = 5), centrilobular nodules (n = 4), consolidation (n = 3), mediastinal lymph node enlargement (n = 5), pleural effusion (n = 3), and pneumomediastinum (n = 3).

Conclusion

Abnormal chest radiographs were uncommon in children with a swine-origin influenza A (H1N1) virus (S-OIV) infection. In children, H1N1 virus infection can be included in the differential diagnosis, when chest radiographs and CT scans show prominent peribronchial markings and ill-defined patchy consolidation with mediastinal lymph node enlargement, pleural effusion and pneumomediastinum.     

Chest radiography findings in adults with pandemic H1N1 2009 influenza

The current pandemic of a novel influenza A (H1N1) virus, commonly referred to as “swine flu”, began in Mexico in March 2009 and reached the UK in April 2009. By 21 July 2009, more than 850 suspected cases of influenza had been seen at Birmingham Heartlands Hospital (BHH), including 52 adults with laboratory-confirmed pandemic H1N1 influenza who were admitted. Of seven patients (13%) requiring intensive care, six needed mechanical ventilation, two needed extra-corporeal membrane oxygenation (ECMO) and one died. Of the 52 admitted adults, 42 (81%) had respiratory symptoms or signs and positive PCR tests for novel Influenza A (H1N1) virus. These patients also had chest radiographs (CXR) taken, which were abnormal for 12 patients (29%). Of these, six patients had bilateral consolidation, which was bibasal in three and widespread in three; all six had pleural effusions. A further six patients had unilateral consolidation with predominantly basal changes; one of these patients had a pleural effusion. The odds ratio for requiring intubation and ventilation with H1N1 influenza and an abnormal CXR was 29.0 (95% confidence interval 2.93–287.0). CXR changes were not common in swine flu, but a significant minority of those requiring admission had consolidation on their CXR. Those who required admission and had CXR changes are more likely to require intubation and ventilation than those without abnormalities on CXR.The current pandemic of a novel influenza A (H1N1) virus, commonly referred to as “swine flu”, began in Mexico in March 2009 and reached the UK in April 2009. The World Health Organization declared a global influenza pandemic on 11 June 2009. International reporting of individual cases was abandoned on 6 July 2009, by which date there had been 94 512 laboratory-confirmed cases and 429 deaths worldwide, mostly in the USA, Mexico, Canada and the UK [1]. By 21 July 2009, there were 17 181 European cases, 10 649 (67%) in the UK [2], of which most were in the West Midlands and London areas [3]. By 21 July 2009, 850 suspected cases of influenza had been seen at Birmingham Heartlands Hospital (BHH), including 52 adults with laboratory-confirmed pandemic H1N1 influenza whose admission was required [4] according to UK Department of Health criteria [5]. Of the seven (13%) who required intensive care, six required mechanical ventilation, 2 needed extra-corporeal membrane oxygenation (ECMO) and one died [6]. The proportions of patients requiring hospitalisation and intensive care are similar to those reported previously [7, 8]. We reviewed the radiography findings in adult patients admitted to our hospital with laboratory-confirmed pandemic H1N1 influenza, and compared these with previous reports from influenza outbreaks and pandemics.     

A comparative study of thin-section CT findings between seasonal influenza virus pneumonia and Streptococcus pneumoniae pneumonia

Objective:

To compare the pulmonary thin-section CT findings in patients with seasonal influenza virus pneumonia with Streptococcus pneumoniae pneumonia.

Methods:

The study group included 30 patients (20 males and 10 females; age range, 20–91 years; mean age, 55.9 years) with seasonal influenza virus pneumonia and 71 patients (47 males and 24 females; age range, 27–92 years; mean age, 67.5 years) with S. pneumoniae pneumonia.

Results:

The proportion of community-acquired infection was significantly higher in patients with influenza virus pneumonia than with S. pneumoniae pneumonia (p = 0.001). CT findings of ground-glass attenuation (GGA) (p = 0.012) and crazy-paving appearance (p = 0.03) were significantly more frequent in patients with influenza virus pneumonia than with S. pneumoniae pneumonia. Conversely, consolidation (p < 0.001), mucoid impaction (p < 0.001), centrilobular nodules (p = 0.04) and pleural effusion (p = 0.003) were significantly more frequent in patients with S. pneumoniae pneumonia than in those with influenza virus pneumonia.

Conclusion:

Pulmonary thin-section CT findings, such as consolidation and mucoid impaction may be useful in distinguishing between seasonal influenza virus pneumonia and S. pneumoniae pneumonia.

Advances in knowledge:

(1) Distinguishing seasonal influenza virus pneumonia with S. pneumoniae pneumonia is important. (2) The CT findings of GGA and crazy-paving appearance were more frequently found in patients with influenza virus pneumonia than in patients with S. pneumoniae pneumonia, whereas consolidation, mucoid impaction, centrilobular nodules and pleural effusion were more frequently found in patients with S. pneumoniae pneumonia.Influenza virus is responsible for seasonal epidemics of community-acquired pneumonia (CAP), with outbreaks occurring predominantly during the winter months. Secondary bacterial superinfections are the most frequent complications among fatal cases of seasonal and pandemic influenza.Streptococcus pneumoniae is the most common pathogen of CAP and is also responsible for the increasing frequency of nosocomial pneumonia.^1–3 The mortality related with pneumonia is affected by initial antibiotic therapy; therefore, early detection of S. pneumoniae pneumonia is important for reducing mortality. Moreover, S. pneumoniae has been identified as the most prominent causative agent for secondary bacterial pneumonia following influenza virus infection.⁴A rapid immunochromatographic membrane test was developed for the detection of S. pneumoniae antigens.⁵ It is a useful technique for the rapid diagnosis of S. pneumoniae pneumonia; however, it does have its limitations. For example, urinary antigens of S. pneumoniae pneumonia cannot be detected a few days after S. pneumoniae infection, and assay sensitivity is approximately 70–80%.There are several reports of the radiologic features of novel influenza virus pneumonia and S. pneumoniae pneumonia.^6–8 However, there are few reports of the CT findings of seasonal influenza virus pneumonia.^9–11 Furthermore, to the best of our knowledge, no studies comparing CT findings in patients with seasonal influenza virus pneumonia to those with S. pneumoniae pneumonia have been published. The present study therefore compared the pulmonary thin-section CT findings of patients with seasonal influenza virus pneumonia to those with S. pneumoniae pneumonia.     

Thin-Section CT Findings of Arc-Welders' Pneumoconiosis

Objective

To describe the thin-section CT findings of arc-welders'' pneumoconiosis.

Materials and Methods

Eighty-five arc-welders with a three to 30 (mean, 15)-year history of exposure underwent thin-section CT scanning. The extent of abnormalities detected was correlated with the severity of dyspnea and pulmonary function tests. For comparison, images of 43 smoking males (mean 25 pack-year) who underwent thin-section CT for other reasons (smokers'' group) were also analyzed.

Results

Fifty-four welders (63.5%) and six smokers (14.0%) showed positive findings. Predominant thin-section CT findings were poorly-defined centrilobular micronodules (30/54, 55.6%), branching linear structure (18/54, 33.3%), and ground-glass attenuation (6/54, 11.1%). In the smokers'' group, poorly-defined micronodules were found in four patients, branching linear structures in one, and ground-glass attenuation in one. In welders, the extent of abnormalities seen on thin-section CT showed no significant correlation with the severity of dyspnea or the results of pulmonary funotion test.

Conclusion

Poorly-defined centrilobular micronodules and branching linear structures were the thin-section CT findings most frequently seen in patients with arc-welders'' pneumoconiosis. Less commonly, extensive ground-glass attenuation was also seen.     

Lymphomatoid Granulomatosis: CT and FDG-PET Findings

Objective

Lymphomatoid granulomatosis (LG) is a rare, aggressive extranodal Epstein-Barr virus (EBV)-positive B-cell lymphoproliferative disease. The purpose of our study was to analyze the CT and fluorodeoxyglucose positron emission tomography (FDG-PET) findings of pulmonary LG.

Materials and Methods

Between 2000 and 2009, four patients with pathologically proven pulmonary LG and chest CT were identified. Two of these patients also had FDG-PET. Imaging features of LG on CT and PET were reviewed.

Results

Pulmonary nodules or masses with peribronchovascular, subpleural, and lower lung zonal preponderance were present in all patients. Central low attenuation (4 of 4 patients), ground-glass halo (3 of 4 patients), and peripheral enhancement (4 of 4 patients) were observed in these nodules and masses. An air-bronchogram and cavitation were seen in three of four patients. FDG-PET scans demonstrated avid FDG uptake in the pulmonary nodules and masses.

Conclusion

Pulmonary LG presents with nodules and masses with a lymphatic distribution, as would be expected for a lymphoproliferative disease. However, central low attenuation, ground-glass halo and peripheral enhancement of the nodules/masses are likely related to the angioinvasive nature of this disease. Peripheral enhancement and ground-glass halo, in particular, are valuable characteristic not previously reported that can help radiologists suggest the diagnosis of pulmonary LG.     

Evaluation of Tracheobronchial Diseases: Comparison of Different Imaging Techniques

Objective

To compare the clinical utility of the different imaging techniques used for the evaluation of tracheobronchial diseases.

Materials and Methods

Forty-one patients with tracheobronchial diseases [tuberculosis (n = 18), bronchogenic carcinoma (n = 10), congenital abnormality (n = 3), post-operative stenosis (n = 2), and others (n = 8)] underwent chest radiography and spiral CT. Two sets of scan data were obtained: one from routine thick-section axial images and the other from thin-section axial images. Multiplanar reconstruction (MPR) and shaded surface display (SSD) images were obtained from thin-section data. Applying a 5-point scale, two observers compared chest radiography, routine CT, thin-section spiral CT, MPR and SSD imaging with regard to the detection, localization, extent, and characterization of a lesion, information on its relationship with adjacent structures, and overall information.

Results

SSD images were the most informative with regard to the detection (3.95±0.31), localization (3.95±0.22) and extent of a lesion (3.85±0.42), and overall information (3.83±0.44), while thin-section spiral CT scans provided most information regarding its relationship with adjacent structures (3.56±0.50) and characterization of the lesion (3.51±0.61).

Conclusion

SSD images and thin-section spiral CT scans can provide valuable information for the evaluation of tracheobronchial disease.     

Lung ultrasound imaging in avian influenza A (H7N9) respiratory failure

Background

Lung ultrasound has been shown to identify in real-time, various pathologies of the lung such as pneumonia, viral pneumonia, and acute respiratory distress syndrome (ARDS). Lung ultrasound maybe a first-line alternative to chest X-ray and CT scan in critically ill patients with respiratory failure. We describe the use of lung ultrasound imaging and findings in two cases of severe respiratory failure from avian influenza A (H7N9) infection.

Methods

Serial lung ultrasound images and video from two cases of H7N9 respiratory failure requiring mechanical ventilation and extracorporeal membrane oxygenation in a tertiary care intensive care unit were analyzed for characteristic lung ultrasound findings described previously for respiratory failure and infection. These findings were followed serially, correlated with clinical course and chest X-ray.

Results

In both patients, characteristic lung ultrasound findings have been observed as previously described in viral pulmonary infections: subpleural consolidations associated or not with local pleural effusion. In addition, numerous, confluent, or coalescing B-lines leading to ‘white lung’ with corresponding pleural line thickening are associated with ARDS. Extension or reduction of lesions observed with ultrasound was also correlated respectively with clinical worsening or improvement. Coexisting consolidated pneumonia with sonographic air bronchograms was noted in one patient who did not survive.

Conclusions

Clinicians with access to point-of-care ultrasonography may use these findings as an alternative to chest X-ray or CT scan. Lung ultrasound imaging may assist in the efficient allocation of intensive care for patients with respiratory failure from viral pulmonary infections, especially in resource scarce settings or situations such as future respiratory virus outbreaks or pandemics.     

Perfusion-based assessment of disease activity in untreated and treated patients with aortitis and chronic periaortitis: correlation with CT morphological,clinical and serological data

Objective:

To evaluate the role of perfusion-based assessment of inflammatory activity in patients with treated and untreated aortitis and chronic periaortitis as compared with clinical and serological markers.

Methods:

35 patients (20 females; median age 66 years) with (peri) aortitis were retrospectively evaluated. All patients had clinical symptoms prompting at the time of imaging. All patients first underwent whole-body contrast-enhanced CT and subsequently segmental volume perfusion CT for assessment of the degree of vascularization of (peri) aortitis as a surrogate marker for inflammatory activity. Blood flow, blood volume, volume transfer constant (k-trans), time to peak and mean transit time were determined. The thickness of the increased connective tissue formation was measured. Perfusion data were correlated with clinical symptoms and acute-phase inflammatory parameters such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and leukocyte number.

Results:

21 of 35 patients were untreated and 14 of 35 had previous/ongoing immunosuppression. The interobserver agreement was good (κ = 0.78) for all perfusion parameters. Average values of perfusion parameters were higher in untreated patients but remained abnormally elevated in treated patients as well. Perfusion data and ESR and CRP correlated well both in aortitis (p < 0.05) and in periaortitis (p < 0.05). In periaortitis, perfusion parameters agreed well with ESR and CRP values (p < 0.05) only in untreated patients.

Conclusion:

Perfusion CT parameters in untreated aortitis and chronic periaortitis correlate well with serological markers with respect to disease activity assessment. However, in treated periaortitis, correlations were weak, suggesting an increased role for (perfusion-based) imaging.

Advances in knowledge:

Volume perfusion CT may be used for diagnosis of aortitis/periaortitis.     

Radiological findings in acute Haemophilus influenzae pulmonary infection

Objective

The aim of this study was to assess pulmonary thin-section CT findings in patients with acute Haemophilus influenzae pulmonary infection.

Methods

Thin-section CT scans obtained between January 2004 and March 2009 from 434 patients with acute H. influenzae pulmonary infection were retrospectively evaluated. Patients with concurrent infection diseases, including Streptococcus pneumoniae (n=76), Staphylococcus aureus (n=58) or multiple pathogens (n=89) were excluded from this study. Thus, our study group comprised 211 patients (106 men, 105 women; age range, 16–91 years, mean, 63.9 years). Underlying diseases included cardiac disease (n=35), pulmonary emphysema (n=23), post-operative status for malignancy (n=20) and bronchial asthma (n=15). Frequencies of CT patterns and disease distribution of parenchymal abnormalities, lymph node enlargement and pleural effusion were assessed by thin-section CT.

Results

The CT findings in patients with H. influenzae pulmonary infection consisted mainly of ground-glass opacity (n=185), bronchial wall thickening (n=181), centrilobular nodules (n=137) and consolidation (n=112). These abnormalities were predominantly seen in the peripheral lung parenchyma (n=108). Pleural effusion was found in 22 patients. Two patients had mediastinal lymph node enlargement.

Conclusion

These findings in elderly patients with smoking habits or cardiac disease may be characteristic CT findings of H. influenzae pulmonary infection.Haemophilus influenzae is an important pneumonia pathogen because of its severity, high incidence of complications and high mortality. This Gram-negative bacillus frequently colonises the human upper respiratory tract, especially the nasopharynx, and is considered to form part of the normal respiratory flora [1]. Most H. influenzae infections are the result of direct extension from the nasopharynx to the lower respiratory tract [1].H. influenzae infection has received increasing attention because it is an important factor in the acute exacerbation of chronic obstructive pulmonary disease (COPD) [1,2]. Acute exacerbation is a frequent event during the prolonged chronic course of COPD, which entails significant morbidity and mortality, and the main aetiology for the majority of episodes is infection.The mortality rate in patients with H. influenzae pneumonia has been reported as 10–42% [3-6]. Moreover, nosocomial outbreaks caused by H. influenzae have been reported [7]. Therefore, it is important to identify the risk factors associated with H. influenzae infection and to evaluate the radiological findings so that no time is lost in initiating appropriate management.Several studies have presented the clinical and microbiological findings in patients with H. influenzae infection [1-4,6,7]. The characteristics of H. influenzae pneumonia on plain radiography have also been described previously [1,8]. Recently, Nei et al [8] have described CT findings of Mycoplasma pneumoniae pneumonia and community-acquired pneumonia caused by other organisms, including 12 patients with H. influenzae pneumonia. The CT finding of bronchial wall thickening in patients with H. influenzae pneumonia was more common than in patients with Streptococcus pneumoniae or Klebsiella pneumoniae.However, to the best of our knowledge, no other English-language studies of pulmonary CT findings in patients with acute H. influenzae pneumonia have been published. This study aimed to assess the clinical findings and pulmonary thin-section CT findings in patients with acute H. influenzae pneumonia.     

Does Establishing a Safety Margin Reduce Local Recurrence in Subsegmental Transarterial Chemoembolization for Small Nodular Hepatocellular Carcinomas?

Objective

To test the hypothesis that a safety margin may affect local tumor recurrence (LTR) in subsegmental chemoembolization.

Materials and Methods

In 101 patients with 128 hepatocellular carcinoma (HCC) nodules (1-3 cm in size and ≤ 3 in number), cone-beam CT-assisted subsegmental lipiodol chemoembolization was performed. Immediately thereafter, a non-contrast thin-section CT image was obtained to evaluate the presence or absence of intra-tumoral lipiodol uptake defect and safety margin. The effect of lipiodol uptake defect and safety margin on LTR was evaluated. Univariate and multivariate analyses were performed to indentify determinant factors of LTR.

Results

Of the 128 HCC nodules in 101 patients, 49 (38.3%) nodules in 40 patients showed LTR during follow-up period (median, 34.1 months). Cumulative 1- and 2-year LTR rates of nodules with lipiodol uptake defect (n = 27) and those without defect (n = 101) were 58.1% vs. 10.1% and 72.1% vs. 19.5%, respectively (p < 0.001). Among the 101 nodules without a defect, the 1- and 2-year cumulative LTR rates for nodules with complete safety margin (n = 52) and those with incomplete safety margin (n = 49) were 9.8% vs. 12.8% and 18.9% vs. 19.0% (p = 0.912). In multivariate analyses, ascites (p = 0.035), indistinct tumor margin on cone-beam CT (p = 0.039), heterogeneous lipiodol uptake (p = 0.023), and intra-tumoral lipiodol uptake defect (p < 0.001) were determinant factors of higher LTR.

Conclusion

In lipiodol chemoembolization, the safety margin in completely lipiodolized nodule without defect will not affect LTR in small nodular HCCs.     

Cytomegalovirus Pneumonia: High-Resolution CT Findings in Ten Non-AIDS Immunocompromised Patients

Objective

To describe the HRCT findings of cytomegalovirus (CMV) pneumonia in non-AIDS immunocompromised patients.

Materials and Methods

This retrospective study involved the ten all non-AIDS immunocompromised patients with biopsy-proven CMV pneumonia and without other pulmonary infection encountered at our Medical Center between January 1997 and May 1999. HRCT scans were retrospectively analysed by two chest radiologists and decisions regarding the findings were reached by consensus.

Results

The most frequent CT pattern was ground-glass opacity, seen in all patients, with bilateral patchy (n = 8) and diffuse (n = 2) distribution. Other findings included poorly-defined small nodules (n = 9) and consolidation (n = 7). There was no zonal predominance. The small nodules, bilateral in eight cases and unilateral in one, were all located in the centrilobular region. Consolidation (n = 7), with patchy distribution, was bilateral in five of seven patients (71%). Pleural effusion and bilateral areas of thickened interlobular septa were seen in six patients (60%).

Conclusion

CMV pneumonia in non-AIDS immunocompromised patients appears on HRCT scans as bilateral mixed areas of ground-glass opacity, poorly-defined centrilobular small nodules, and consolidation. Interlobular septal thickening and pleural effusion are frequently associated.     

Pulmonary imaging of pandemic influenza H1N1 infection: relationship between clinical presentation and disease burden on chest radiography and CT

The potential for pulmonary involvement among patients presenting with novel swine-origin influenza A (H1N1) is high. To investigate the utility of chest imaging in this setting, we correlated clinical presentation with chest radiographic and CT findings in patients with proven H1N1 cases. Subjects included all patients presenting with laboratory-confirmed H1N1 between 1 May and 10 September 2009 to one of three urban hospitals. Clinical information was gathered retrospectively, including symptoms, possible risk factors, treatment and hospital survival. Imaging studies were re-read for study purposes, and CXR findings compared with CT scans when available. During the study period, 157 patients presented with subsequently proven H1N1 infection. Hospital admission was necessary for 94 (60%) patients, 16 (10%) were admitted to intensive care and 6 (4%) died. An initial CXR, carried out for 123 (78%) patients, was abnormal in only 40 (33%) cases. Factors associated with increased likelihood for radiographic lung abnormalities were dyspnoea (p<0.001), hypoxaemia (p<0.001) and diabetes mellitus (p = 0.023). Chest CT was performed in 21 patients, and 19 (90%) showed consolidation, ground-glass opacity, nodules or a combination of these findings. 4 of 21 patients had negative CXR and positive CT. Compared with CT, plain CXR was less sensitive in detecting H1N1 pulmonary disease among immunocompromised hosts than in other patients (p = 0.0072). A normal CXR is common among patients presenting to the hospital for H1N1-related symptoms without evidence of respiratory difficulties. The CXR may significantly underestimate lung involvement in the setting of immunosuppression.In late March 2009, an outbreak of respiratory illness caused by novel swine-origin influenza A virus (H1N1) was identified in Mexico [1]. In June that year, the World Health Organization (WHO) declared a global pandemic [2]. Since then the virus has spread worldwide and by 8 November 2009 more than 206 countries had reported laboratory-confirmed cases of H1N1 to the WHO, with more than 6250 related deaths [2, 3].Risk factors and clinical manifestations associated with H1N1 have been previously reported [4–9]. Significantly less attention has been given to the imaging findings of H1N1 that may serve as early indicators of the presence and impending severity of disease. Early recognition of radiological patterns may have an impact in timely management of critically ill patients with H1N1. We examined the chest X-ray (CXR) and CT findings in newly diagnosed cases of H1N1, and evaluated the relationship between risk factors, symptoms and extent of disease on the CXR compared with CT.     

Meticillin-resistant Staphylococcus aureus and meticillin-susceptible S. aureus pneumonia: comparison of clinical and thin-section CT findings

Objectives

The purpose of this study was to compare the clinical and thin-section CT findings in patients with meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-susceptible S. aureus (MSSA).

Methods

We retrospectively identified 201 patients with acute MRSA pneumonia and 164 patients with acute MSSA pneumonia who had undergone chest thin-section CT examinations between January 2004 and March 2009. Patients with concurrent infectious disease were excluded from our study. Consequently, our study group comprised 68 patients with MRSA pneumonia (37 male, 31 female) and 83 patients with MSSA pneumonia (32 male, 51 female). Clinical findings in the patients were assessed. Parenchymal abnormalities, lymph node enlargement and pleural effusion were assessed.

Results

Underlying diseases such as cardiovascular were significantly more frequent in the patients with MRSA pneumonia than in those with MSSA pneumonia. CT findings of centrilobular nodules, centrilobular nodules with a tree-in-bud pattern, and bronchial wall thickening were significantly more frequent in the patients with MSSA pneumonia than those with MRSA pneumonia (p=0.038, p=0.007 and p=0.039, respectively). In the group with MRSA, parenchymal abnormalities were observed to be mainly peripherally distributed and the frequency was significantly higher than in the MSSA group (p=0.028). Pleural effusion was significantly more frequent in the patients with MRSA pneumonia than those with MSSA pneumonia (p=0.002).

Conclusions

Findings from the evaluation of thin-section CT manifestations of pneumonia may be useful to distinguish between patients with acute MRSA pneumonia and those with MSSA pneumonia.Staphylococcus aureus is one of the most common and important pathogens involved in nosocomial pneumonia, particularly because of the development of meticillin-resistant S. aureus (MRSA) [1]. Pneumonia caused by MRSA is a clinically important type of pneumonia because of its severity, the high incidence of complications, and the increased mortality it causes in nosocomial pulmonary infections [2-4].In recent years, MRSA has also emerged as an increasingly important cause of community-acquired bacterial infection, often affecting healthy children and adults who have no apparent risk factors for infection. community-acquired MRSA strains causing life-threatening infections, such as necrotising pneumonia and necrotising fasciitis, have been found to frequently carry Panton–Valentine leukocidin (PVL) genes [5-7].The mortality of pneumonia is usually associated with inadequate initial antibiotic therapy; therefore, early recognition of S. aureus pneumonia is important for reducing morbidity and mortality. Meanwhile bacteriological evaluation may take time and cause a delay in diagnosis. As such, thin-section CT may be helpful in expediting differential diagnosis of infections and in the selection of appropriate antibiotics. Recently, a small number of reports have emerged describing thin-section CT findings in patients with pathogens, including Klebsiella pneumoniae, Mycoplasma pneumoniae and Chlamydia pneumoniae [8-11]. As for S. aureus pneumonia, several studies have shown differences in clinical findings between MRSA pneumonia and meticillin-susceptible S. aureus (MSSA) pneumonia [12-13]. In a radiological study, González et al [14] reported that there were no differences on chest radiographs between 32 patients with MRSA and 54 patients with MSSA. Nguyen and colleagues [15] reported CT findings in nine patients with community-acquired MRSA, whose conditions were characterised by extensive bilateral consolidation and frequent cavitation, which is commonly associated with rapid progression and clinical deterioration. However, there are currently very few reports with radiological findings in patients with MRSA or MSSA pneumonia. Moreover, to the best of our knowledge, no studies describing the comparison of CT findings in patients with MRSA with those with MSSA have been published. As such, the current study sought to evaluate thin-section CT findings of acute MRSA pneumonia compared with those with acute MSSA pneumonia.     

Nodular Ground-Glass Opacities on Thin-section CT: Size Change during Follow-up and Pathological Results

Objective

To evaluate the inter-group differences in growth and the pathological results of nodular ground-glass opacities (GGOs) according to their size and focal solid portions.

Materials and Methods

Ninety-six nodular GGOs in 55 individuals followed by CT for at least one month from an initial chest CT were included. Forty nodular GGOs in 30 individuals were pathologically confirmed to be: adenocarcinoma (n = 15), bronchioloalveolar carcinoma (BAC) (n = 11), atypical adenomatous hyperplasia (AAH) (n = 8), focal interstitial fibrosis (n = 5) and aspergillosis (n = 1). Lesions were categorized based on high-resolution CT findings: pure nodular GGO (PNGGO) ≤ 10 mm, PNGGO > 10 mm, mixed nodular GGO (MNGGO)≤ 10 mm, and MNGGO > 10 mm. In each group, the change in size during the follow-up period, the pathological results and the rate of malignancy were evaluated.

Results

Three MNGGO lesions, and none of the PNGGO, grew during the follow-up period. Resected PNGGOs ≤ 10 mm were AAH (n = 6), BAC (n = 5), and focal interstitial fibrosis (n = 1). Resected PNGGOs > 10 mm were focal interstitial fibrosis (n = 4), AAH (n = 2), BAC (n = 2), and adenocarcinoma (n = 2). Resected MNGGOs ≤ 10 mm were adenocarcinoma (n = 2), and BAC (n = 1). Resected MNGGOs > 10 mm were adenocarcinoma (n = 11), BAC (n = 3), and aspergillosis (n = 1).

Conclusion

Mixed nodular GGOs (MNGGOs) had the potential for growth; most were pathologically adenocarcinoma or BAC. By contrast, PNGGOs were stable for several months to years; most were AAH, BAC, or focal interstitial fibrosis.     

Digital Tomosynthesis for Evaluating Metastatic Lung Nodules: Nodule Visibility,Learning Curves,and Reading Times

Objective

To evaluate nodule visibility, learning curves, and reading times for digital tomosynthesis (DT).

Materials and Methods

We included 80 patients who underwent computed tomography (CT) and DT before pulmonary metastasectomy. One experienced chest radiologist annotated all visible nodules on thin-section CT scans using computer-aided detection software. Two radiologists used CT as the reference standard and retrospectively graded the visibility of nodules on DT. Nodule detection performance was evaluated in four sessions of 20 cases each by six readers. After each session, readers were unblinded to the DT images by revealing the true-positive markings and were instructed to self-analyze their own misreads. Receiver-operating-characteristic curves were determined.

Results

Among 414 nodules on CT, 53.3% (221/414) were visible on DT. The main reason for not seeing a nodule on DT was small size (93.3%, ≤ 5 mm). DT revealed a substantial number of malignant nodules (84.1%, 143/170). The proportion of malignant nodules among visible nodules on DT was significantly higher (64.7%, 143/221) than that on CT (41.1%, 170/414) (p < 0.001). Area under the curve (AUC) values at the initial session were > 0.8, and the average detection rate for malignant nodules was 85% (210/246). The inter-session analysis of the AUC showed no significant differences among the readers, and the detection rate for malignant nodules did not differ across sessions. A slight improvement in reading times was observed.

Conclusion

Most malignant nodules > 5 mm were visible on DT. As nodule detection performance was high from the initial session, DT may be readily applicable for radiology residents and board-certified radiologists.     

Hepatopulmonary Syndrome Induced by Common Bile Duct Ligation in a Rabbit Model: Correlation between Pulmonary Vascular Dilatation on Thin-Section CT and Angiography and Serum Nitrite Concentration or Endothelial Nitric Oxide Synthase (eNOS)1 Expression

Objective

To investigate the correlation between radiologic vascular dilatation and serum nitrite concentration and eNOS expression in the endothelial cell and pneumocyte in a rabbit model of hepatopulmonary syndrome induced by common bile duct ligation (CBDL).

Materials and Methods

Thin-section CT scans of the lung and pulmonary angiography were obtained 3 weeks after CBDL (n=6), or a sham operation (n=4), and intrapulmonary vasodilatation was assessed. The diameter and tortuosity of peripheral vessels in the right lower lobe by thin-section CT and angiography at the same level of the right lower lobe in all subjects were correlated to serum nitrite concentration and eNOS (endothelial nitric oxide synthase) expression as determined by immunostaining.

Results

The diameters of pulmonary vessels on thin-section CT were well correlated with nitrite concentrations in serum (r = 0.92, p < 0.001). Dilated pulmonary vessels were significantly correlated with an increased eNOS expression (r = 0.94, p < 0.0001), and the severity of pulmonary vessel tortuosity was found to be well correlated with serum nitrite concentration (r = 0.90, p < 0.001).

Conclusion

The peripheral pulmonary vasculature in hepatopulmonary syndrome induced by CBLD was dilated on thin-section CT and on angiographs. Our findings suggest that peripheral pulmonary vascular dilatations are correlated with serum nitrite concentrations and pulmonary eNOS expression.     

Influenza A virus: radiological and clinical findings of patients hospitalised for pandemic H1N1 influenza

Purpose

This paper describes the radiological and clinical findings identified in a group of patients with H1N1 influenza.

Materials and methods

Between May and mid-November 2009, 3,649 patients with suspected H1N1 influenza presented to our hospital. Our study population comprised 167 (91 male, 76 female patients, age range 11 months to 82 years; mean age 29 years) out of 1,896 patients with throat swab positive for H1N1 and clinical and laboratory findings indicative of viral influenza. All 167 patients were studied by chest X-ray (CXR), and 20 patients with positive CXR and worsening clinical condition also underwent computed tomography (CT). The following findings were evaluated on both modalities: interstitial reticulation (IR), nodules (N), ground-glass opacities (GGO), consolidations (CONS), bacterial superinfection and pulmonary complications.

Results

Ninety of 167 patients had positive CXR results. Abnormalities identified on CXR, variously combined and distributed, were as follows: 53 IR, 5 N, 13 GGO, 50 CONS; the predominant combination was represented by six GGO with CONS. Of the 20 CXR-positive cases also studied by CT, 17 showed pathological findings. The abnormalities identified on CT, variously combined and distributed, were as follows: 14 IR, 2 N, 5 GGO; the predominant combination was 10 GGO with CONS. Despite the differences between the two modalities, the principle radiological findings of bacterial superinfection were tree-in-bud pattern, consolidation with air bronchogram, and pleural and pericardial effusion. Fifteen of the 20 patients studied by both CXR and chest CT showed respiratory complications with bilateral and diffuse CONS on CXR and CT. Six of 15 died: 4/6 of acute respiratory distress syndrome and 2/6 of multiple organ failure.

Conclusions

Our study describes the radiological and clinical characteristics of a large population of patients affected by H1N1 influenza. CXR and chest CT identified the site and extent of the pulmonary lesions and documented signs of bacterial superinfection and pulmonary complications.