The application of high-resolution CT to diagnosis in diffuse parenchymal lung disease

High resolution computed tomography (CT) now has a central role in the evaluation of diffuse lung disease. It is of particular use in the formulation of a differential diagnosis. Whilst CT often conveys sufficient information to allow non-invasive diagnosis, it sometimes reveals atypical appearances, contributing to the continuing reclassification of diffuse lung disease and justifying histological evaluation in some patients. Thus, CT as a new technology does not always replace conventional diagnostic methods, but is best integrated with clinical assessment, other non-invasive investigations and surgical lung biopsy: this applies equally to clinical diagnosis and to the definition and reclassification of disease entities. In this article, we explore the optimal diagnostic use of CT. The limitations of CT series in simulating the clinical application of CT in the management of diffuse parenchymal lung disease highlight the need for an integrated approach to diagnosis, including corroborative data drawn from many sources. High-resolution computed tomography, when interpreted in the context of the pre-test probability, obviates invasive investigation in many cases. As descriptions of the CT appearances of individual diffuse lung diseases are refined, ongoing re-evaluation is required to establish which features can be regarded as pathognomonic, for diagnostic purposes, and how CT can be integrated into revised disease definitions so that the most clinically relevant diagnostic criteria are formulated.

Lung biopsy in diffuse parenchymal lung disease

This review sets out to define the role of surgical biopsy in the diagnosis and prognosis of diffuse parenchymal lung disease, the pros and cons of each procedure and the interpretation of the results in the context of clinical and other investigative data. Surgical lung biopsy remains the investigation with the greatest overall diagnostic sensitivity for diffuse parenchymal lung disease. Rates of diagnosis are approximately 90-95%, compared with approximately 70% for both high-resolution computed tomography (HRCT) and transbronchial biopsy. Although open lung biopsy, and more recently videoassisted thoracoscopic surgery, have good safety records, neither technique has been utilised as frequently as might be expected, with wide regional variation for various reasons. More recently, HRCT used in conjunction with clinical and other investigative modalities, has increased the accuracy of diagnosis for some diseases, including the majority of cases of cryptogenic fibrosing alveolitis (HRCT & bronchoalveolar lavage), Langerhans' cell histiocytosis (HRCT), lymphangioleiomyomatosis (HRCT), and silicosis (HRCT). At present, the vasculitides and the idiopathic interstitial pneumonias, other than cryptogenic fibrosing alveolitis, always require a surgical biopsy. As experience with high resolution computed tomography grows, it is possible that other diseases will be able to be diagnosed without surgical biopsy. These newer modalities of investigation do have appreciable limitations and where sufficient doubt exists about diagnosis, surgical lung biopsy must continue to be utilised.

Pneumonitis complicating methotrexate therapy for pustular psoriasis

We report a patient with pustular psoriasis who developed interstitial pneumonitis after receiving weekly methotrexate (MTX) therapy at an average dose of 20 mg for 26 years. The patient responded dramatically to withdrawal of the drug and administration of corticosteroids. Pulmonary toxicity is a rare adverse effect of MTX therapy and is particularly uncommon in psoriatics. As interstitial pneumonitis is a potentially fatal but reversible complication, early respiratory symptoms even in patients on low-dose MTX treatment should be appropriately investigated.

Reproducibility of the WHO/IASLC grading system for pre-invasive squamous lesions of the bronchus: a study of inter-observer and intra-observer variation

AIMS

Although many workers have graded pre-invasive squamous lesions arising in the bronchus, there has been no consensus classification system until the latest edition of the WHO/IASLC histological classification of pulmonary and pleural tumours. Because the value of any such system is dependent on its reproducibility, we have circulated a series of such lesions to a panel of histopathologists to assess interobserver and intra-observer variation when the WHO/IASLC classification was applied.

METHODS AND RESULTS

Colour transparencies of 28 pre-invasive squamous lesions were assessed by six histopathologists (two with a special interest in pulmonary pathology, two generalists and two trainees) on three separate occasions over a period of 3 months, using the criteria of the WHO/IASLC (mild, moderate and severe dysplasia, and in-situ carcinoma). An additional category of metaplasia was added for those cases that showed no dysplasia. Weighted kappa coefficents of agreement (K(w)) were used to evaluate paired observations with a standard quadratic weighting being employed, such that kappa coefficients corresponded to intra-class correlation coefficients. Wilcoxon's sign-ranked test was used to measure the statistical significance of group trends, when comparing kappa values for the three grading systems. Various 3-point systems were also assessed, through combination of the above groups. Intra-observer agreement was substantially better than interobserver variation (mean: 0.71 vs. 0.55). Between the various pathologist groups, inter-observer variation was relatively minor, although intra-observer variation was higher within the trainee pathologist group. Using weighted kappa values, there was no significant difference in either inter-observer or intra-observer agreement between the five point grading system and a 3-point system of metaplasia/mild, moderate and severe/in-situ grades. However, there was a significant increase in variation when a 3-point system of metaplasia/mild, moderate/severe and in-situ carcinoma was used.

CONCLUSION

This study shows levels of interobserver and intra-observer variation similar to those found in other grading systems in histopathology, with no significant decrease in variability found by abridging the system. The WHO/IASLC system is therefore recommended for future use in both clinical and research fields.

Acute respiratory distress syndrome caused by pulmonary and extrapulmonary injury: a comparative CT study

PURPOSE

To determine computed tomographic (CT) differences between acute respiratory distress syndrome (ARDS) due to pulmonary injury (ARDS(p)) and extrapulmonary injury (ARDS(ex)).

MATERIALS AND METHODS

CT appearances in 41 patients (27 male, 14 female; mean age, 47.1 years +/- 17.1 [SD]; age range, 17-79 years; those with ARDS(p), n = 16; those with ARDS(ex), n = 25) were categorized as typical or atypical of ARDS by two observers. The extent of individual CT patterns was also quantified.

RESULTS

Typical CT appearances were more frequent in ARDS(ex) than ARDS(p) (18 [72%] of 25 vs five [31%] of 16 patients, respectively; P <.01). Sensitivity, specificity, and accuracy of a typical CT pattern for the diagnosis of ARDS(ex) were 72%, 69%, and 71%, respectively. Atypical appearances were characterized by more extensive nondependent intense parenchymal opacification (IPO) (P =.03) and cysts (P =.05), whereas typical CT appearances had more extensive dependent IPO (P =.01). Typical appearances at CT were independently related to the cause of ARDS (odds ratio, 8.9; 95% CI: 1.8, 44.2; P <.01) but were independent of the time from intubation. Foci of nondependent IPO were more extensive in ARDS(p) (P =.05) than ARDS(ex), but this finding was ascribable to differences in time to CT (after intubation) between ARDS(p) and ARDS(ex).

CONCLUSION

The differentiation between ARDS(p) and ARDS(ex) can, with some caveats, be based on whether the CT appearances are typical or atypical of ARDS but not on any individual CT pattern in isolation.

Cryptogenic Organizing Pneumonia

The terms cryptogenic organizing pneumonia (COP) and idiopathic bronchiolitis obliterans with organizing pneumonia (BOOP) are synonymous. Typical COP should be viewed as a clinicopathological syndrome, consisting of respiratory and systemic symptoms (usually low-grade), patchy consolidation on chest radiography and computed tomography, a restrictive defect on pulmonary function testing, and the presence of buds of granulation tissue within the distal airways and alveolar spaces. In the correct clinical context, the diagnosis can be secured by transbronchial biopsy, with typical bronchoalveolar lavage features providing useful diagnostic support. In typical COP, corticosteroid therapy is highly effective; an early trial of withdrawal of treatment is appropriate because relapse of COP is not associated with a poor long-term outcome. Atypical forms of COP are outlined in this article, including focal, explosive, progressive fibrotic, and nonprogressive fibrotic variants. The occasional evolution of COP into a progressive fibrotic disorder is associated with a poor long-term outcome and poses particular therapeutic difficulties.

The prognostic significance of the histologic pattern of interstitial pneumonia in patients presenting with the clinical entity of cryptogenic fibrosing alveolitis

Lone cryptogenic fibrosing alveolitis (CFA) is a progressive interstitial lung disease, with a median survival of 3 to 6 yr from the onset of dyspnea. CFA can be subdivided into prognostically significant histopathologic patterns, including nonspecific interstitial pneumonia (NSIP). We reviewed 78 patients with a clinicopathologic diagnosis of CFA, biopsied between 1978 and 1989, to evaluate the prevalence and prognostic significance of these histopathologic patterns, in particular NSIP. Biopsy appearances were reclassified by two pulmonary histopathologists as usual interstitial pneumonia (UIP) (47%), NSIP (36%), or desquamative interstitial pneumonia (DIP)/respiratory bronchiolitis-associated interstitial lung disease (RBILD) (17%). The kappa coefficient of agreement between pathologists was 0.49. In 67 cases, follow-up was complete to death or 10 yr after biopsy, with 50 deaths during a median follow-up of 42 mo (UIP, 89%; NSIP, 61%, DIP/RBILD, 0%). Survival was highest in DIP/RBILD and higher in NSIP than UIP, p < 0.0005. When analysis was confined to patients with UIP or NSIP, the mortality of UIP remained higher, p < 0.01, but the 5-yr survival in patients with fibrotic NSIP was only 45%, indicating that this histologic appearance is often associated with a poor outcome. A response to treatment was more frequent in DIP/RBILD than in NSIP (p < 0.01) or UIP (p < 0.0005). This study confirms the prognostic value of subclassifying patients with CFA according to histopathologic pattern. However, in patients with clinically typical CFA, a histologic diagnosis of fibrotic NSIP needs to be interpreted with caution and does not necessarily denote a good outcome.

Nonspecific interstitial pneumonia: variable appearance at high-resolution chest CT

PURPOSE

To describe the computed tomographic (CT) findings in patients with nonspecific interstitial pneumonia (NSIP) and to compare these with the CT findings of other chronic infiltrative lung diseases.

MATERIALS AND METHODS

Findings in 50 patients with biopsy-proved NSIP and a CT scan were reviewed by two thoracic radiologists in consensus. After the findings were described, the observers judged whether the findings were compatible with previously published descriptions of NSIP or whether the findings would support the diagnosis of a different chronic infiltrative lung disease.

RESULTS

Eleven (22%) of the 50 patients had CT findings that were compatible with previous descriptions of NSIP. Sixteen (32%) patients had CT findings that were more compatible with usual interstitial pneumonia. The other 23 (46%) patients had findings that were nondiagnostic or most compatible with the diagnosis of another chronic infiltrative lung disease.

CONCLUSION

Contrary to previously published articles, there are a wide variety of CT findings in cases of NSIP.

Allergic bronchopulmonary aspergillosis in the asthma clinic. A prospective evaluation of CT in the diagnostic algorithm

OBJECTIVE

Allergic bronchopulmonary aspergillosis (ABPA) occurs in cases of atopic asthma and may result in important lung disease. Early diagnosis is essential as this disease is responsive to steroids. However, while asthma is common, ABPA is infrequently diagnosed. CT allows precision in the diagnosis of central bronchiectasis (which is virtually pathognomonic of ABPA) and may enable earlier diagnosis.

DESIGN

A prospective evaluation of 255 patients with asthma for ABPA, using skin prick testing (SPT) for Aspergillus fumigatus (AF) as a screening tool and incorporating CT into the diagnostic algorithm.

SETTING

Asthma clinic, Green Lane Hospital, Auckland, New Zealand.

PARTICIPANTS

Patients with asthma.

INTERVENTIONS

ABPA was diagnosed using "essential" criteria (ie, asthma, SPT positivity to AF, elevated serum total IgE, elevated serum AF-specific IgE, and pulmonary infiltrates seen on chest radiography or central bronchiectasis seen on CT scan) and "minimal essential" criteria (ie, asthma, SPT positivity, and central bronchiectasis).

MEASUREMENTS AND RESULTS

Two hundred fifty-five consecutive patients with asthma who consented to SPT were studied: 218 of 255 patients (86.8%) were atopic; and 47 of 255 patients (21.6%) were AF-positive, of whom 35 accepted further evaluation including CT scanning. A secure diagnosis of ABPA, satisfying all essential criteria, was evident in 9 of 35 patients (25.7%), a proportion that increased to 13 of 35 patients (37.1%) by using the minimal essential diagnostic criteria.

CONCLUSIONS

SPT positivity to AF was present in approximately 20% of patients in the asthma clinic. A diagnosis of ABPA is disclosed by CT in 25 to 40% of SPT-positive patients, depending on the selection of diagnostic criteria. These findings support the use of SPT as a screening tool in the asthma clinic and indicate that a routine CT scan is warranted in SPT-positive patients.

Human in vitro immune responses to Mycobacterium tuberculosis

SETTING

T helper cells can be divided into 2 subsets on the basis of their cytokine generation. T helper 1 cells secreting gamma interferon and interleukin 2 appear to be more prominent in patients with limited tuberculous disease.

OBJECTIVE

The purpose of this study was to evaluate human T helper cell immune responses to mycobacterial antigens in vitro and correlate these with the clinical features of patients with tuberculous infection or disease.

DESIGN

We studied 51 subjects and 11 controls who were grouped according to disease involvement as follows: 1) Mantoux negative, BCG negative, no disease; 2) Mantoux positive, no disease; 3) localized extrapulmonary; 4) healed pulmonary; 5) active pulmonary; and 6) miliary/disseminated. Peripheral blood mononuclear cells were cultured with PHA, PPD or Tetanus Toxoid, proliferation assessed and the supernatant analysed using an ELISA for IFN gamma. ELISA was also used to measure M. tuberculosis specific antibodies in the serum.

RESULTS

Mantoux size correlated with PPD proliferation r = 0.5, P = 0.005 and gamma IFN production r = 0.36, P < 0.01. All groups produced abundant gamma IFN although there was a trend toward higher production in groups 3 and 4. M. tuberculosis specific IgA (P = 0.003) and IgG1 (P = 0.002) was higher in groups 5 and 6. Those patients with limited disease (groups 2-4) had significantly lower levels of IgG4 than patients with severe disease (groups 5 & 6) (P < 0.02).

CONCLUSION

In conclusion patients with healed or extrapulmonary disease have immune responses in vitro suggestive of a TH1 (cell mediated immune) response, whereas patients with miliary/disseminated disease have antibody production suggestive of a TH2 response, together with high gamma IFN production. Both TH1 and TH2 responses may be necessary for host protection if there is a high bacillary load.

Lateral cavity wall thickening as an early radiographic sign of mycetoma formation

The sensitivity of chest radiography for the early detection of mycetoma formation within fibrotic cavities is poor. The purpose of this study was to determine the predictive value of the secondary sign of lateral cavity wall thickening for the detection of a radiographically occult mycetoma. The chest radiographs and CT scans of 70 patients who had a total of 109 fibrotic cavities on CT were reviewed by two observers. Dimensions of the cavity, mycetoma, and cavity wall thickness on chest radiography and CT scans were recorded. Mycetomas were visible in 41 of 99 cavities on chest radiographs and in 61 of 109 cavities on CT. Using CT as the gold standard for detecting the presence of mycetomas, the sensitivity of chest radiography for the presence of a mycetoma was 62 % and the specificity 94 %, and the positive and negative predictive values were 93 and 66 %, respectively. On logistic regression analysis, lateral wall thickness on chest radiography was predictive of the presence of a mycetoma (p < 0.0005) independent of other radiographic features. In patients with chronic fibrocavitary disease on chest radiography, the presence of lateral wall thickening is highly suggestive of an underlying mycetoma.

Airflow obstruction in bronchiectasis: correlation between computed tomography features and pulmonary function tests

BACKGROUND

An obstructive defect is usual in bronchiectasis, but the pathophysiological basis of airflow obstruction remains uncertain. High resolution computed tomographic (CT) scanning now allows quantitation of static morphological abnormalities, as well as dynamic changes shown on expiratory CT scans. The aim of this study was to determine which static and dynamic structural abnormalities on the CT scan are associated with airflow obstruction in bronchiectasis.

METHODS

The inspiratory and expiratory features on the CT scan of 100 patients with bronchiectasis undergoing concurrent lung function tests were scored semi-quantitatively by three observers.

RESULTS

On univariate analysis the extent and severity of bronchiectasis, the severity of bronchial wall thickening, and the extent of decreased attenuation on the expiratory CT scan correlated strongly with the severity of airflow obstruction; the closest relationship was seen between decreased forced expiratory volume in one second (FEV(1)) and the extent of decreased attenuation on the expiratory CT scan (R(s) = -0.55, p<0. 00005). On multivariate analysis bronchial wall thickness and decreased attenuation were consistently the strongest independent determinants of airflow obstruction. The extent of decreased attenuation was positively associated with the severity of bronchial wall thickness, but was not independently linked to gas transfer levels. Endobronchial secretions seen on CT scanning had no functional significance; the severity of bronchial dilatation was negatively associated with airflow obstruction after adjustment for other morphological features.

CONCLUSIONS

These findings indicate that airflow obstruction in bronchiectasis is primarily linked to evidence of intrinsic disease of small and medium airways on CT scanning and not to bronchiectatic abnormalities in large airways, emphysema, or retained endobronchial secretions.

Nitrofurantoin-induced lung disease: two cases demonstrating resolution of apparently irreversible CT abnormalities

A reticular pattern on high resolution CT (HRCT) invariably represents significant lung pathology and is the dominant feature of irreversible fibrosis. We present two cases of nitrofurantoin-induced pulmonary toxicity in which the initial HRCT showed a widespread reticular pattern and associated distortion of the lung parenchyma, thought to represent established fibrosis. Follow-up HRCT scans after withdrawal of the drug showed resolution of this supposedly irreversible pattern.

Evaluation of patients undergoing lung volume reduction surgery: ancillary information available from computed tomography

AIM

A number of imaging techniques have been used for the pre-operative assessment of patients for lung volume reduction surgery (LVRS). We evaluated whether data currently acquired from perfusion scintigrams and cine MR of the diaphragm are obtainable from high resolution CT (HRCT) of the thorax.

MATERIALS AND METHODS

Thirty patients taking part in a randomized controlled trial of LVRS against maximal medical therapy were evaluated. HRCT examinations (n= 30) were scored for (i) the extent and distribution of emphysema; (ii) the extent of normal pulmonary vasculature; and (iii) diaphragmatic contour, apparent defects and herniation. On scintigraphy, (n= 28), perfusion of the lower thirds of both lungs, as a proportion of total lung perfusion (LZ/T(PERF)), was expressed as a percentage of predicted values (derived from 10 normal control subjects). On cine MR (n= 25) hemidiaphragmatic excursion and coordination were recorded.

RESULTS

Extensive emphysema was present on HRCT (60% +/- 13.2%). There was strong correlation between the extent of normal pulmonary vasculature on HRCT and on perfusion scanning (r(s)= 0.85, P< 0.00005). Hemidiaphragmatic incoordination on MR was weakly associated with hemidiaphragmatic eventration on HRCT (P= 0.04).

CONCLUSION

The strong correlation between lung perfusion assessed by HRCT and lung perfusion on scintigraphy suggests that perfusion scintigraphy is superfluous in the pre-operative evaluation of patients with emphysema for LVRS.

A CT sign of chronic pulmonary arterial hypertension: the ratio of main pulmonary artery to aortic diameter

The aim of this study was to determine whether the ratio of the diameters of the main pulmonary artery and of the ascending aorta (rPA), as assessed on computed tomography (CT), is predictive of pulmonary arterial hypertension (PAH). We undertook a retrospective review of 50 patients with a wide range of pulmonary and cardiovascular diseases, who had undergone both chest CT and pulmonary arterial pressure measurements at right heart catheterization. Two independent observers made measurements of the diameter of the main pulmonary artery and of the ascending aorta on a single defined CT section. Body surface area (BSA, n = 48), pulmonary arteriolar resistance (n = 39), total lung capacity (n = 40), and aortic pressures (n = 50) were also recorded. rPA and pulmonary arterial diameter (dPA) were positively related to mean pulmonary artery pressure (Rs = 0.74, p < 0.0005 for both analyses). For patients younger than 50 years of age, mean pulmonary artery pressure correlated more strongly with rPA than dPA (Rs = 0.77, p < 0.00005, compared with Rs = 0.59, p < 0.005); and vice versa for patients older than 50 years of age (Rs = 0.63, p < 0.005, compared with Rs = 0.75, p < 0.00005). Using a mean pulmonary artery pressure greater than 20 mm Hg as indicative of PAH and a value of rPA > 1, the sensitivity, specificity, and positive and negative predictive values for determining PAH were 70% (26/37), 92% (12/13), 96% (26/27), and 52% (12/23), respectively. On multivariate analysis, rPA was positively related to mean pulmonary artery pressure (p < 0.0005), and negatively related to age (p < 0.0005), but was not related to BSA. By contrast, dPA showed some dependency on BSA (p < 0.0005), as well as on mean pulmonary arterial pressure. In patients younger than 50 years of age, we have found a strong correlation between rPA and mean pulmonary artery pressure in a heterogeneous study population, and this relationship is independent of BSA and sex. The presence of the sign "rPA > 1" is simple in practical CT reading to determine; if this is identified, there is a very high probability of pulmonary arterial hypertension, and clinicians should be alerted to this possibility.

Visual quantitation and observer variation of signs of small airways disease at inspiratory and expiratory CT

Areas of decreased pulmonary attenuation representing small airways disease can be identified on computed tomography (CT). The objective was to quantify differences between inspiratory and expiratory CT for the detection of signs of small airways disease by four observers. Observer variation and the superiority of a fine versus a coarse grading system were also evaluated. Inspiratory and expiratory CT scans of 106 patients with conditions characterized by small airways disease and 19 healthy individuals were assessed by four observers. The extent of decreased attenuation was scored on a fine scale to the nearest 5% and also semiquantitatively on a coarser 5-point scale. Decreased attenuation was more extensive on expiratory CT (median. 6.7%; 0-76.7%) than on inspiratory CT (median, 3.8%; 0-81.7%). The fine scoring system had unacceptable interobserver variation (coefficient of variation, 80% for inspiratory CT, 70% for expiratory CT). The semiquantitative system had acceptable interobserver agreement (inspiratory CT k(w) = 0.64; expiratory CT, k(w) = 0.69) and good intra-observer agreement (inspiratory CT, k(w) = 0.80; expiratory CT, k(w) = 0.64). The major CT sign of small airways disease is more confidently quantified on expiratory CT. A fine scoring system is associated with unacceptable observer variation, and a coarse semiquantitative system is more suitable for quantitative studies of small airways disease.

Normal adult values, diurnal variation, and repeatability of nasal nitric oxide measurement

Reports of elevated nasal nitric oxide (NO) levels in allergic rhinitis suggest that nasal NO levels could be a valuable marker of upper airway inflammation, provided that the reproducibility of nasal NO measurement is acceptable. The aims of this study were to evaluate the precision with which nasal NO levels can be measured at single point in time, and to quantify within-day and between-day variation. Nasal NO was measured using a modified chemiluminescence analyzer. Population data were normally distributed, as judged by testing for skewness and kurtosis. NO levels were not related to age or gender, and there was no evidence of diurnal variation. Sampling rates of 250 mL/minute and 500 mL/minute at a single point in time had acceptable reproducibility (coefficients of variation 10.2% and 6.6%, respectively). However, within-day variation (coefficient of variation 13.4%) and between-day variation (coefficient of variation 11.8%), at a sampling rate of 500 L/minute, were substantially higher. These findings highlight the importance of taking measurement variation into account, in the interpretation of NO levels, in clinical research and, potentially, in routine practice. In individual patients, an alteration of 20-25% in NO levels is required, to ensure that change is genuine and not ascribable to the noise of measurement.

Follicular bronchiolitis: thin-section CT and histologic findings

PURPOSE

To evaluate the thin-section computed tomographic (CT) findings of follicular bronchiolitis and compare them with the histologic findings.

MATERIALS AND METHODS

Thin-section CT scans obtained in 12 patients (age range, 24-77 years; mean age, 47 years) with follicular bronchiolitis proved at open lung biopsy were reviewed by two observers. Underlying conditions included rheumatoid arthritis (n = 8), mixed collagen vascular disorders (n = 2), autoimmune disorder (n = 1), and acquired immunodeficiency syndrome (n = 1). All patients had thin-section CT scans (1.0-1.5-mm collimation, 11 patients; 3.0-mm collimation, one patient; high-spatial-frequency reconstruction algorithm) obtained at 10-mm intervals through the chest.

RESULTS

The main CT findings included bilateral centrilobular (n = 12) and peribronchial (n = 5) nodules. All 12 patients had nodules smaller than 3 mm in diameter; six patients also had nodules 3-12 mm in diameter. Areas of ground-glass opacity were present in nine (75%) patients. Histologically, all patients had lymphoid hyperplasia along the bronchioles; eight had peribronchiolar lymphocytic infiltration.

CONCLUSION

The cardinal CT feature of follicular bronchiolitis consists of small centrilobular nodules variably associated with peribronchial nodules and areas of ground-glass opacity.

A comparison of methods for enhancing the detection of areas of decreased attenuation on CT caused by airways disease

PURPOSE

The purpose of this work was to investigate thin section CT image enhancement of subtle areas of decreased attenuation of the lung parenchyma in suspected airways disease.

METHOD

Forty-seven consecutive patients with chronic sputum production underwent pulmonary function tests and high resolution CT (HRCT). Single section inspiratory (INSP), expiratory (EXP), and minimum intensity projection (MINIP) images through the lower lobes were acquired. A histogram stretch was applied to the INSP and MINIP images, generating two further image formats. The five image types were compared for the extent of decreased attenuation, observer confidence, and correlations with pulmonary function tests.

RESULTS

Interobserver variation was lowest with MINIP images (mean weighted K: MINIP 0.70, INSP sections 0.65, other image formats < or =0.48). Observers were most confident with EXP and MINIP images. EXP sections identified more disease than MINIP images (p<0.001). Correlations with pulmonary function tests were similar for each image format.

CONCLUSION

The HRCT changes of small airways disease are enhanced with image postprocessing. MINIP images are associated with increased observer confidence and agreement as compared with HRCT alone.

Mechanism of mosaic attenuation of the lungs on computed tomography in induced bronchospasm

The purpose of this study was to investigate whether hypoxic pulmonary vasoconstriction is the major determinant of the computed tomography (CT) pattern of mosaic attenuation in asthmatic patients with induced bronchoconstriction. Thin-section CT was performed at suspended full inspiration immediately and 30 min after methacholine bronchoprovocation in 22 asthmatic subjects, who were randomly assigned to breathe room air (group A, n = 8), oxygen via nasal prongs at 5 l/min (group B, n = 8), and oxygen via face mask at 12 l/min (group C, n = 6). CT changes were quantified in terms of global lung density and density in hypodense and hyperdense areas. Lung parenchymal density increases were greatest in group C and greater in group B than in group A, globally (P = 0.03) and in hypodense regions (P = 0.01). On bivariate analysis, the only change in cross-sectional area was related to change in global density. In hypodense regions, density change was related both to reduction in cross-sectional area (P < 0.0005) and to oxygen administration (P = 0.01). After correction for changes in global lung density, only oxygen was independently related to density increase in hypodense areas (P = 0.02). In induced bronchoconstriction, the CT appearance of mosaic attenuation can be largely ascribed to hypoxic vasoconstriction rather than to changes in lung inflation.

Pericardial thickening or effusion in patients with pulmonary artery hypertension: a CT study

OBJECTIVE

The aim of the study was to determine the prevalence of pericardial thickening or effusion revealed by CT in patients with pulmonary artery hypertension.

MATERIALS AND METHODS

Forty-five patients underwent pulmonary artery catheterization and CT of the thorax. On CT, we measured the maximum pericardial thickness, total pericardial score (the sum of four measures of pericardial thickness), and thickness of the anterior pericardial recess. Patients were grouped according to mean pulmonary artery pressure: group 1, less than 21 mm Hg (n = 15); group 2, 21-35 mm Hg (n = 15); and group 3, greater than 35 mm Hg (n = 15).

RESULTS

The prevalence of an increased pericardial score and increased maximum pericardial thickening was higher in group 3 than in group 1 or group 2 (p = .02 and < .001, respectively). Anterior pericardial recess thickening was markedly increased in group 3 (p < .0001). For all patients, significant correlations (Spearman's rank correlation coefficient = .44-.56, p < .005-.0001) were found between mean pulmonary artery pressure and all pericardial measures.

CONCLUSION

On CT, pericardial thickening or effusion is a frequent finding in patients with severe pulmonary hypertension.

Acute respiratory distress syndrome: CT abnormalities at long-term follow-up

PURPOSE

To document abnormalities at computed tomography (CT) in adult survivors of acute respiratory distress syndrome (ARDS), to determine the relationships between CT patients during the acute phase and at follow-up, and to assess the effects of mechanical ventilation on the development of CT abnormalities.

MATERIALS AND METHODS

Thin-section CT scans were obtained during the acute illness and at follow-up in 27 patients with ARDS. The extent and distribution of individual CT patterns were independently analyzed.

RESULTS

At follow-up CT, a reticular pattern was the most prevalent (23 patients [85%]) and extensive CT abnormality, with a striking anterior distribution (more anterior distribution than posterior distribution, P < .001). A reticular pattern at follow-up was inversely correlated with the extent of intense parenchymal opacification on scans obtained during the acute illness (Spearman r = -0.26; P < .001). The extent of a reticular pattern at follow-up CT was independently related to the total duration of mechanical ventilation (P = .02) but was most strongly related to the duration of pressure-controlled inverse-ratio ventilation (P < .001).

CONCLUSION

A reticular pattern, with a striking anterior distribution, is a frequent finding of follow-up CT in ARDS survivors and is most strongly related to the duration of pressure-controlled inverse-ratio ventilation.

Pulmonary sarcoidosis: morphologic associations of airflow obstruction at thin-section CT

PURPOSE

To identify relationships between the obstructive defects of pulmonary sarcoidosis and the computed tomographic (CT) patterns of disease.

MATERIAL AND METHODS

CT scans obtained in 45 patients were scored semiquantitatively for extent of five CT patterns, and the functional importance of each pattern was evaluated.

RESULTS

The most prevalent CT patterns were decreased attenuation (n = 40), a reticular pattern (n = 37), and a nodular pattern (n = 36). At univariate and multivariate analyses, a reticular pattern was the main determinant of functional impairment, particularly airflow obstruction. The extent of a reticular pattern was independently associated with airflow obstruction, as shown by the inverse relationships with the forced expiratory volume in 1 second (FEV1) (P < .001), FEV1-forced vital capacity ratio (P < .01), maximum expiratory flow at 25% above residual volume (P < .001), and maximum expiratory flow at 50% above residual volume (P < .001) and the positive relationship with the residual volume-total lung capacity ratio (P < .001).

CONCLUSION

In sarcoidosis, CT features compatible with small airways disease are common but contribute little to airflow obstruction, particularly in more advanced disease, which is characterized by an extensive reticular pattern. A reticular pattern at CT is the major morphologic association of airflow obstruction.

Bronchiectasis following colectomy for Crohn's disease

Bronchiectasis developing following colectomy for ulcerative colitis has been reported in a few cases. This may be the first report of bronchiectasis developing after colectomy for Crohn's disease. The close temporal relationship to colectomy, lack of bacterial pathogens in the sputum, and an impressive response to oral steroids suggest a difference in pathogenesis from idiopathic bronchiectasis.