Monitoring bulky mediastinal disease with gallium-67, CT-scan and magnetic resonance imaging in Hodgkin's disease and high-grade non-Hodgkin's lymphoma.

Treatment of both Hodgkin's disease (HD) and high-grade non-Hodgkin's lymphoma (HG-NHL) with bulky presentation at diagnosis frequently results in residual masses detected radiologically. Conventional diagnostic radiology and computed tomography (CT) are generally unable to detect the differences between tumor tissue and fibrosis. Gallium-67-citrate (67Ga) SPECT and magnetic resonance imaging (MRI) can potentially differentiate residual active tumor tissue and fibrosis. Thirty-three patients with HD or HG-NHL presenting with bulky mediastinal disease were studied with CT, 67Ga SPECT, and MRI (only for 16 patients) at diagnosis, after two-thirds of their chemotherapy, at the end of chemotherapy, and after radiotherapy in order to evaluate the mediastinal region on the basis of persistence of residual masses and activity of pathological tissue. After treatment, all patients with 67Ga-negative (30/33) disease are still in continuous complete response. Among the three 67Ga-positive patients, 2 relapsed within one year and another one is still alive without evidence of disease. Regarding MRI, two patients were found to be positive, one of them concomitant with 67Ga-positivity; both patients survive in complete response. In lymphoma patients with bulky mediastinal presentation, the 67Ga SPECT remains the preferable imaging technique for monitoring and differentiating the eventual active residual tumor. In combination, CT and 67Ga SPECT represent a suitable complete imaging approach to the radiological diagnosis which may be useful in these particular patients. MRI could probably be considered as a second-line method and from our data would be used only in selected cases because of the high cost, accessibility, and lower specificity as opposed to 67Ga SPECT in evaluating potentially active residual disease.

Imaging of small airways disease, with emphasis on high resolution computed tomography.

Bronchioles are the airways less than 2-3 mm in diameter. Normal bronchioles cannot be reliably detected by means of high resolution computed tomography (HRCT). Nevertheless, in pathological cases, bronchiolar lesions can be identified by taking into account direct and indirect signs. On radiological grounds, bronchiolar lesions can be classified into four groups, on the basis of HRCT findings: 1) prevailing nodular opacities and "tree in bud" pattern; 2) consolidations or ground-glass opacities; 3) mosaic oligosemia with expiratory air-trapping; and 4) mixed cases. In this review, we present the main radiological and HRCT findings in four different entities, representing the more typical cases of bronchiolar pathology; bronchiolitis obliterans; bronchiolitis obliterans with organizing pneumonia; diffuse panbronchiolitis; and respiratory bronchiolitis with associated interstitial lung disease. HRCT sometimes allows a precise diagnosis of bronchiolar pathology; however, more often, it permits only a range of hypotheses to be advanced. More importantly, it allows a precise localization for biopsy procedures and an exact follow-up after institution of therapy. In normal subjects, less than 1% of the whole bronchial tree is visible on the standard chest radiograph. HRCT offers a good insight and invaluable information. New techniques, such as volumetric HRCT with sliding-thin-slab maximum- and minimum-intensity projections (MIP and minip) could represent an important additional tool in the evaluation of small airways disease.

Assessment of emphysema using high resolution CT, CT expiratory density mask, and plain chest films.

Pulmonary function tests (diffusing capacity for carbon monoxide of the lungs) and radiological imaging (plain chest film, high resolution computed tomography (CT) and CT expiratory density mask) were compared in the assessment of 29 patients with suspected airways obstruction. Conventional roentgenogram showed a good agreement with the diffusing capacity of the lungs and proved to be useful in predicting the presence of severe emphysema, but the extension of the disease was more precisely assessed by computed tomography. A good agreement was found between high resolution CT and density mask CT, although the "subjective" high resolution identified more patients with mild emphysema than the "automated" density mask. In conclusion, although the plain chest film is useful in the diagnosis of severe emphysema, CT (especially when high resolution is used) is helpful in identifying cases of mild disease and in diagnosing the type of emphysema.

[Thoracic lymphoma and AIDS]. / Lymphome thoracique et SIDA.

During the past 4 years, 122 patients with AIDS and 20 with thoracic lymphoma associated to AIDS were observed. There were 18 cases of non-Hodgkin's lymphoma, mostly at a high grade and a high b-cell stage (Burkitt's or Burkitt-like lymphoma) (16 cases). This prevalence reflects the general increase in the number of neoplasms secondary to immunosuppression, which goes along with the improvement of prevention and the control of opportunistic infections. Out of these 20 lymphomas in AIDS, 5 (25%) produced thoracic lesions; in 4 cases, the initial site of the disease was in a thoracic site. The frequency of such expressions is greater that reported in the literature. The radiological appearances are atypical relative to the classical signs of lymphoma in the general population, with predominantly nodular forms (60%) or peripheral, fast-growing masses that are likely to invade the thoracic wall. Isolate lymph node invasion is possible, as well as pleural effusion. Though not pathognomonic, this appearance is highly suggestive of lymphoma in AIDS (LDS) in HIV-positive patients. In all patients with pulmonary lymphoma, CT showed bilateral lesions in a greater number than plain radiography had shown, with morphological and CT appearances that allowed a correct approach of the diagnosis and an appropriate choice of the site of biopsy.

Hemodynamic estimation of chronic cor pulmonale by Doppler echocardiography. Clinical value and comparison with other noninvasive imaging techniques.

Pulmonary arterial pressure (PAP) represents an important prognostic factor in patients affected by chronic obstructive pulmonary disease (COPD). A noninvasive diagnostic approach is offered by several imaging techniques, such as chest X-ray, nuclear medicine, real-time sonography, color Doppler US, CT and MRI. However, at present a quantitative assessment of PAP is not achieved with reasonable precision with any of these techniques. Tricuspid regurgitation can be estimated by continuous wave Doppler but it may be difficult in patients with COPD. On the contrary, the severity of pulmonary hypertension can be accurately assessed with pulsed Doppler echocardiography from the subxiphoid region, using a general purpose US device. Nineteen adult patients with COPD were studied by duplex-Doppler from an oblique subxiphoid approach and right heart catheterization. The study was diagnostic in all cases with quality Doppler recordings. A significant relationship was found between AcT and pulmonary mean or systolic pressure at rest. An accurate prediction of PAP in COPD is possible by means of pulsed-Doppler also in low-grade hypertension. This technique is considered a simple and reliable adjunct to the noninvasive evaluation of COPD and represents a satisfactory alternative to the classical parasternal approach preferred by cardiologists but often not suitable for emphysematous patients. Radiologists who routinely use a general purpose US device are encouraged to try this new technique in the study of heart disease.

Use of chest sonography in acute-care radiology().

Diagnosis of acute lung disease is a daily challenge for radiologists working in acute-care areas. It is generally based on the results of chest radiography performed under technically unfavorable conditions. Computed tomography (CT) is undoubtedly more accurate in these cases, but it cannot always be performed on critically ill patients who need continuous care.The use of thoracic ultrasonography (US) has recently been proposed for the study of acute lung disease. It can be carried out rapidly at the bedside and does not require any particularly sophisticated equipment. This report analyzes our experience with chest sonography as a supplement to chest radiography in an Emergency Radiology Unit. We performed chest sonography - as an adjunct to chest radiography - on 168 patients with acute chest pathology. Static and dynamic US signs were analyzed in light of radiographic findings and, when possible, CT. The use of chest US improved the authors' ability to provide confident diagnoses of acute disease of the chest and lungs.

[Diffuse ground-glass opacity of the lung. A guide to interpreting the high-resolution computed tomographic (HRCT) picture]. / Opacità polmonare diffusa a vetro smerigliato ("ground glass"). Guida all'interpretazione del quadro con tomografia computerizzata ad alta risoluzione (TCAR).

The so-called ground glass pulmonary opacity is characterized by a slight increase in lung density, with persistent visibility of vascular structures and bronchial walls. If vessels are obscured, the term consolidation is preferred. This kind of pulmonary opacity, which may be patchy or diffuse, was well known in conventional radiology, but has been recently re-evaluated, following the increasingly widespread use of high resolution CT of the lung. Ground glass opacity is commonly observed in patients with early diffuse pulmonary infiltrative diseases. Though non-specific in itself, the sign is always very significant. Particularly, it could represent a useful sign of active and treatable abnormality in some diffuse pulmonary diseases, such as idiopathic pulmonary fibrosis and sarcoidosis. The ground glass opacity may also be observed in pulmonary edema, desquamative pneumonitis, Pneumocystis carinii pneumonia, alveolar proteinosis, hypersensitive pneumonitis and drug induced or radiation induced lung disease. This paper represents a contribution to the understanding of the pathologic bases of the ground glass pulmonary opacity and an introduction to its differential diagnosis.

Paraseptal emphysema mimicking unilateral lymphangitic carcinomatosis: CT findings.

A 65-year-old man with lung carcinoma is presented. Chest radiography showed unilateral Kerley B lines in the right midlung and base, suggestive of lymphangitic carcinomatosis. High resolution CT demonstrated that this finding was due to residual normal interlobular septa, suspended between areas of paraseptal emphysema.

[Use of computerized tomography in asthmatic patients]. / Impiego della Tomografia Computerizzata nel paziente asmatico.

This study was aimed at assessing the role of high resolution Computed Tomography (HRCT) in the asthmatic patient, during disease worsening. Chest radiography plays a major role in the assessment of the most common complications of asthma, such as pneumothorax, pneumomediastinum, or lobar collapse. Conventional CT and HRCT are sometimes used when a complication is suspected, particularly chronic eosinophilic pneumonia and allergic bronchopulmonary aspergillosis. We prospectively examined 31 asthmatic patients with clinical and functional worsening submitting them to chest radiographs and HRCT scans. In 5 of them, radiographic findings were suggestive of a complication: 3 patients presented allergic bronchopulmonary aspergillosis and 2 chronic eosinophilic pneumonia; in these cases HRCT confirmed the diagnosis and yielded other useful pieces of information, but did not change the prognosis or the therapeutic approach. In the remaining 26 patients, HRCT findings were abnormal in 61% of cases, while chest films were abnormal in 26% of cases only. An outstanding diagnostic contribution came from HRCT which demonstrated a high incidence of small airway disease and, above all, cylindrical bronchiectasis (53.8%), especially in the upper lobes. HRCT also demonstrated that asthma does not usually cause emphysematous destruction in the patients that never smoked. Even though our study enrolled only a small number of patients, the results suggest that asthma is a more destructive disease than previously believed and that HRCT could be a useful examination to perform even when chest film findings are normal.

[The assessment of pulmonary arterial pressure by pulsed Doppler in patients with obstructive pneumopathy]. / Valutazione della pressione arteriosa polmonare mediante Doppler pulsato nei pazienti affetti da pneumopatia ostruttiva.

The severity of pulmonary arterial hypertension can be assessed by duplex-Doppler echocardiography, a subxiphoid approach and a general-purpose duplex device. Normally, the peak Doppler flow velocity occurs in midsystole and the flow profile is parabolic (bullet-like). In pulmonary arterial hypertension, changes in vascular compliance cause maximal acceleration of blood in early systole, with shortening of pulmonary acceleration time (AcT, or time to peak velocity). In the more severe cases, a midsystolic notching is visible, related to rapid deceleration of blood flow, followed by a brief secondary increase in velocity in the late systole. We studied 19 adult patients with chronic obstructive pulmonary disease with duplex-Doppler examination, with a subxiphoid approach and right heart catheterization. The study was diagnostic in all cases with Doppler recordings of good quality. An relationship was found between AcT and pulmonary mean or systolic arterial pressure at rest. An evident accurate prediction of pulmonary arterial pressure in emphysematous patients is possible by means of pulsed Doppler, also in case of low-level hypertension. We believe this method to be a simple and reliable adjunct to the non-invasive work-up of emphysematous patients and to represent a good alternative to the classical parasternal approach, which is often not feasible in these patients.

[The assessment of the severity of pulmonary edema by computed tomography. A comparison between high-resolution computed tomography, objective evaluation with density masks and functional tests]. / Bilancio della gravità dell'enfisema polmonare mediante tomografia computerizzata. Confronto fra tomografia computerizzata ad alta risoluzione, valutazione obiettiva con maschera di densità e test funzionali.

The results of high-resolution computed tomography (HRCT) were correlated with those of pulmonary function tests, chest films and CT expiratory density mask values in the evaluation of pulmonary emphysema in 33 symptomatic subjects. Emphysema was quantitated with both subjective and objective measurements. Conventional chest films were useful to diagnose severe emphysema but its actual extent was more reliably evaluated with CT scoring systems. HRCT and density mask correlated well with function tests, but the former method exhibited stronger correlation with carbon monoxide diffusion capacity. The opposite was true for hyperinflation and expiratory obstruction variables. Subjective CT estimates, which are quick and easy to perform, were seen to correspond more specifically to the pathophysiologic derangement and should therefore be used to evaluate the anatomic extent of disease. The functional severity of emphysema correlated only with the overall extent of disease and not with its regional distribution in the upper or lower lungs. Finally, in 4 cases (12.1%) with low CT scores, FEV1 was reduced but diffusion capacity values were normal. In one of these patients HRCT showed signs of bronchiolitis. In fact, small airway disease might be a more critical factor in determining functional impairment than the actual anatomical emphysema.

[Thoracic lymphoma in AIDS]. / Linfomi toracici nell' AIDS.

Over the last 4 years, we observed 122 patients with AIDS and 20 with AIDS-related lymphomas (ARL) in the chest. Eighteen of the latter were non-Hodgkin's forms, mostly high-grade and high-stage B-cell (Burkitt or Burkitt-like) types (16 cases.) This prevalence reflects the overall increase in neoplasms secondary to immunodepression, which is parallel to improved prevention and control of opportunistic infections. Of 20 ARLs, 5 (25%) presented thoracic lesions; in 4 of them the onset of the disease was localized in the chest. The incidence of such manifestations is higher than that reported in the literature. Moreover, radiological features are quite atypical relative to the "classical" signs of lymphoma in the general population, with predominant (60%) nodules or quickly-growing peripheral masses which may subsequently invade chest walls. Isolated nodal enlargement is also a possible finding, as well as pleural effusion. This pattern, though not pathognomonic, is highly suggestive--in HIV-positive patients--of ARL. In all the patients with pulmonary lymphoma CT demonstrated bilateral lesions--more than conventional X-rays--with morphologic and densitometric features which helped make the correct diagnosis. Moreover, CT was helpful in choosing the appropriate site for biopsy.

[High-resolution computed tomography study (HRCT) in so-called emphysema B. The correlations between the radiogram, the anatomical findings yielded by high-resolution computed tomography and the clinico-functional assessment]. / Lo studio con tomografia computerizzata con alta risoluzione (TCAR) nel cosiddetto enfisema B. Correlazioni fra il radiogramma, i rilievi anatomici consentiti dalla tomografia computerizzata con alta risoluzione e la valutazione clinico-funzionale.

The results are reported of a prospective study on 28 emphysematous patients with clinical, functional and radiologic correlations. Thirteen of 28 patients had type-B, the clinical "blue and bloater", emphysema. The grade of emphysema was investigated on conventional chest films and on HRCT scans, with a visual scoring system. Hyperinflation was assessed on conventional chest films and correlated with the extent of emphysema on HRCT images and with functional impairment. In our series, the extent of emphysema in B-type patients was markedly lower than in other patients of the same age, with the same smoking habits, dyspnea and functional impairment. Moreover, the incidence of centrilobular involvement was higher, though not statistically significant. The B-type exhibited more severe dilatation of subsegmental pulmonary arteries (76.9% vs. 20% p < 0.001) and a striking incidence of small airway disease (84.6% vs. 26.6%, p < 0.002). This findings may explain the radiographic pattern of "increased vascularity" seen on chest films. Bronchiolectasis and small airway wall thickening are much more frequent in type-B emphysema, together with patchy areas of ground-glass opacity and small peripheral nodules. A close correlation was observed between signs of small airway disease on HRCT images and functional clinical impairment. Thus, the small airway disease might eventually prove to be a more critical factor in causing functional and hemodynamic impairment in B-type emphysema than the actual extent of centrilobular emphysema.

[Signs of inflammatory activity in thoracic sarcoidosis. A high-resolution computerized tomography study]. / Segni di attività infiammatoria nella sarcoidosi toracica. Studio con Tomografia Computerizzata ad alta risoluzione.

Sarcoidosis is characterized by the presence of non-caseating granulomas. Lymphadenopathy and diffuse parenchymal abnormalities often involve the chest. This study was aimed at finding out signs that could be suggestive of disease activity and if the lesions are reversible after therapy. Sixty-three patients underwent chest radiography, high resolution CT, functional studies, bronchoalveolar lavage and 67Ga scintigraphy. Twenty-three patients were followed-up. Lymphadenopathies, nodular opacities and acinar opacities resolved after steroid therapy; bronchiolectasies, bronchiectasies, septal thickening and parenchymal distorsion did not disappeared after therapy and are therefore considered as irreversible lesions. Ground glass opacities are an uncommon finding; they are due to fibrosis or to widespread interstitial granulomas rather than alveolitis. The prognostic meaning of ground glass opacities is uncertain. Therefore, disease activity findings are mainly lymphadenopathies, nodules and consolidations. Nevertheless these findings not necessarily imply a bad prognosis, as acute sarcoidosis seems to respond well to steroid therapy, even with complete remission. It remains debated if a CT study is worthwhile in all the new cases of sarcoidosis or only in the clinically more severe ones.

[The assessment of the activity of idiopathic pulmonary fibrosis by high-resolution computed tomography]. / Valutazione di attività della fibrosi idiopatica polmonare mediante Tomografia Computerizzata ad alta risoluzione.

The authors report the results of the study performed with high resolution CT (HRCT) in a group of 29 patients affected with idiopathic pulmonary fibrosis (IPF). Each patient underwent HRCT at the beginning of the study and after one year. A complete clinico-functional assessment was available in 20 cases and functional CT correlation was made in these patients; 15/20 subjects underwent immunosuppressive therapy with corticosteroids and cyclophosphamide. Disease severity was assessed with chest radiography and HRCT. On the basis of CT findings the patients were classified into three groups, according to Wells classification: predominant ground-glass pattern, mixed pattern and predominant reticular disease with honeycombing. Furthermore, a visual score was assigned to total disease extent and a different score to ground-glass and reticular opacities. Our data confirm the poor accuracy of chest radiography in assessing disease type and overall severity, versus the outstanding diagnostic accuracy of HRCT. We also found a high incidence of mediastinal adenopathies (37.9% of the patients) and signs of pulmonary arterial hypertension (62%), together with low extent of pulmonary emphysema (65.5% of the patients; mean extent: 5.4%). Ground-glass attenuation is an early sign of IPF and might suggest alveolitis activity. In our series, however, the patients with grade I disease were rare (6.8%), but likely to benefit from therapy. Different from Wells, we found no significant difference in the evolution of the patients with grade II versus grade III disease. Wells grading was useful in early disease assessment, but the visual score of total disease extent and the score of ground-glass and reticular opacities were much more useful in the follow-up because they can assess disease progression. Furthermore, in the few patients with predominant alveolitis, who improve after therapy, the relative prevalence of the reticular pattern might allocate the patient in a higher Wells group with a "paradoxical" worsening, if the visual score of the extent of the primary lesion is not used.

[Assessment of early complications of kidney transplantation. Is duplex-Doppler useful for the diagnosis of acute rejection?]. / Valutazione delle complicanze precoci del trapianto renale. Qual'è l'utilità del Doppler-duplex nella diagnosi del rigetto acuto?

The authors studied with duplex-Doppler US 28 renal transplant recipients in 31 clinically different episodes, during the early postoperative period. Morphological data were thus obtained, as well as hemodynamic information. According to the literature on the subject, a pulsatility index (PI) greater than 1.5 was considered as abnormal. US diagnosis was retrospectively compared with final clinical diagnosis and with response to therapy. In one case, the kidney was surgically removed. We evaluated US sensitivity and specificity in the diagnosis of acute rejection with real-time US, Doppler alone and combined with duplex. A PI greater than or equal to 1.5 corresponded to acute rejection, with 60% sensitivity and 85.7% specificity. With a PI greater than 1.8, sensitivity decreased to 50%, but specificity increased to 100%. The severest changes in Doppler waveforms had a bad prognostic significance. Besides poor specificity--which is so often emphasized in literature--our results chiefly demonstrated sensitivity limitations, partly corrigiable with real-time US signs, together with Doppler PI (sensitivity: 90%, specificity: 85.7%). Duplex-Doppler US, in spite of its well-known limitations, remains therefore a simple, rather reliable and non-invasive technique to study renal transplant complications.

[Bronchial involvement in sarcoidosis. Study with high resolution computerized tomography]. / II coinvolgimento bronchiale nella sarcoidosi. Studio con Tomografia Computerizzata con alta risoluzione.

We investigated the HRCT findings of bronchial abnormalities in thoracic sarcoidosis, the post-treatment reversibility of such patterns and their specificity for sarcoidosis. Sixty-one sarcoidosis patients were submitted to chest radiography and HRCT at onset. The diagnosis had transbronchial biopsy confirmation in all patients. HRCT was repeated in 21 patients after a cycle of steroid therapy. Sarcoidosis patients were randomized with 29 patients with diffuse infiltrative lung diseases of different nature. The HRCT findings of bronchial abnormalities follow: extrinsic bronchial compression or displacement by lymphadenopathies (regular/irregular), bronchial wall thickening (regular/irregular), bronchial lumen abnormalities, traction bronchiectasis and bronchiolectasis. Bronchial abnormalities were found in the first HRCT study in 44/61 sarcoidosis patients (72.1%), in 18 patients with extrinsic bronchial compression or displacement by lymphadenopathies (40.9%), in 2 with bronchiectasis or bronchiolectasis (4.5%) and in 24 with one or more other abnormalities (54.5%). Bronchial signs were found in 16/21 patients examined with HRCT after steroid therapy (76.1%). Bronchial abnormalities remained unchanged in 11 patients (68.7%), they improved or disappeared in 5 patients (31%) and appeared ex novo in 2 patients. HRCT patterns of bronchial abnormalities were found in 17/29 patients with other diseases (58.6%), with high rates of bronchial wall thickening and bronchiectasis or bronchiolectasis. The most common HRCT bronchial finding in sarcoidosis was extrinsic bronchial compression of displacement by lymphadenopathies. This was the only sign which could actually differentiate sarcoidosis from other patients (p < 0.01). Other signs (bronchial lumen abnormalities and bronchial wall thickening) were frequently found in both sarcoidosis and non-sarcoidosis patients and did not permit to distinguish the former from the latter. In our experience, HRCT findings of bronchial abnormalities were frequently observed in sarcoidosis patients, but they are not specific enough to diagnose sarcoidosis and their usefulness is limited in predicting posttreatment reversibility (activity evaluation) of this condition.

[Destructive spondylopathy in the dialysis patient. The diagnostic role of magnetic resonance]. / La spondilopatia destruente del dializzato. Ruolo diagnostico della risonanza magnetica.

Magnetic resonance imaging (MRI) was employed to study 7 long-term hemodialysis patients affected with destructive amyloid spondyloarthropathy. In the appropriate clinical setting, MRI proved to be more useful than conventional radiography or CT and more definitive in excluding infections. Indeed, MRI can replace more invasive procedures in making the correct diagnosis. Different than what is reported in literature, a high incidence of odontoid lesions (C2) was observed in our series, with extraosseous and extradural deposits of soft tissue masses (amyloid pseudotumors), subluxation, odontoid invagination and medullary compression. Bone lesions, involved disks and amyloid pseudotumors typically exhibited low-intensity signal on both T1- and T2-weighted sequences and no enhancement following Gd-DTPA injection. The use of MRI is thus suggested, especially at cervical level, also in case of relatively mild symptoms.

[Quantitative assessment of pulmonary emphysema with computerized tomography. Comparison of the visual score and high resolution computerized tomography, expiratory density mask with spiral computerized tomography and respiratory function tests]. / Valutazione quantitativa dell'enfisema polmonare mediante tomografia computerizzata. Confronto tra il punteggio visivo con alta risoluzione nell'inspirazione, maschera della densità automatica con Tomografia Computerizzata spirale nell'espirazione ed esami funzionali respiratori.

CT is the most accurate method to detect pulmonary emphysema in vivo. We compared prospectively two different methods for emphysema quantitation in 5 normal volunteers and 20 consecutive patients with chronic obstructive pulmonary disease (COPD). All subjects were submitted to function tests and HRCT; three scans were acquired at preselected levels during inspiration. The type and extent of pulmonary emphysema were defined, using the time-honored visual score system, by two independent observers under blind conditions. Disagreements were subsequently settled by consent. All subjects were also examined with expiratory spiral CT, using a density mask program, at two different cut-off levels (-850, -900 HU). Visual score and expiratory spiral density mask values (-850 HU) were significantly correlated (r = 0.86), but the visual extent of emphysema was always higher than shown by expiratory spiral CT. The emphysema extent assessed with both CT methods correlated with the function result of expiratory airflow obstruction and gas diffusion impairment (visual score versus forced expiratory volume in one second: r = -0.81, versus single breath carbon monoxide diffusion: r = -0.78. Spiral expiratory density mask -850 HU versus forced expiratory volume in one second: r = -0.85, versus single breath carbon monoxide diffusion: r = -0.77). When -900 HU was used as the cut-off value for the expiratory density mask, the correlation with single breath carbon monoxide diffusion worsened (r = -0.56). Visual score and expiratory density mask -850 HU gave similar results and permitted COPD patients to be clearly distinguished from normal controls (p < 0.01). Residual lung volume, measured with expiratory spiral CT correlated significantly with residual volume measured with the helium dilution technique (r = 0.66), but CT values were always higher than function results. We believe the true residual volume should lie somewhere in between the CT value and the function results with the helium dilution technique and conclude that the extent of pulmonary emphysema can be confidently assessed with CT methods. Finally, the simple visual score may be as reliable as such highly sophisticated new methods as the spiral expiratory density mask. Expiratory studies offer new insights into different normal and abnormal features of COPD and respiratory impairment.