European Respiratory Society
Imaging (out of print)

This book has been superseded by a newer edition.

Chest physicians use a wide variety of imaging techniques in their pursuit of accurate diagnosis and in the evaluation of treatment. Technical advances in computer science, continuous refinements in computed tomography, positron emission tomography as well as magnetic resonance imaging have profoundly transformed our way of visualising chest diseases. This issue of the European Respiratory Monograph aims to give an overview of developments in imaging and to describe direct clinical applications. Furthermore, diagnostic imaging strategies are discussed for a variety of highly prevalent respiratory pathologies, such as pulmonary embolism, idiopathic interstitial pneumonias and collagen-vascular disorders. Imaging facilities for screening and staging lung carcinoma are carefully reviewed in different chapters. The final goal of this issue of the Monograph is a more comprehensible use of currently available imaging technologies.

  • European Respiratory Society Monographs
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    Correspondence: A. Bankier, Dept of Radiology, Medical University of Vienna, Waehringer Guertel 18–20, A-1090 Vienna, Austria.

    This glossary of terms for thoracic radiology aims to familiarise the nonradiological reader with the most commonly used nomenclature in thoracic radiological reports. Knowledge of these terms is important to ensure the active communication between clinicians and radiologists in a clinical setting. Terms have been defined according to their anatomical correlates, and purely descriptive terms have been avoided. This nomenclature should thereby serve as an easy-to-read and easy-to-browse reference for the clinician in their daily routine.

  4. Page 23
    Correspondence: C. Schaefer-Prokop, Dept of Radiology, Amsterdam Medical Center, University of Amsterdam, Meibergdreef 9, NL-1100dd, Amsterdam, the Netherlands.

    Changing healthcare needs require tomorrow's diagnostic imaging service providers to rapidly produce the highest quality of images, transmit them broadly, display them in alternative ways, and then archive and retrieve them efficiently. To accomplish this, digital radiographical image-capture systems become the critical part.

    The promised benefits of digital radiography are numerous: faster availability of images, fewer repeat examinations, direct importation of patient identifiers from the radiology information system, compact storage, convenient retrieval, greater staff and clinician productivity and the potential for lower radiation doses.

    Computed radiography (CR) technology based on storage phosphor plates is well established. The system is cheap, has good reproducibility, and is robust. The physical size of the units could be decreased and throughput increased, while increasing image quality. Increased detector properties and dual reading have made CR technology to a dose-efficient system. A high resolution 4×4 k matrix does not appear to offer general diagnostic improvement in chest applications compared with a 2×2 k matrix.

    Direct radiography (DR) systems have been developed that convert X-ray signals into electric signals, either directly as in a selenium-based systems or indirectly as in the systems using a scintillator layer in combination with a-Si photodiodes. DR is the common name for a number of different technologies. The combination of high image quality with the potential for dose reduction represents a definite advantage of DR systems.

    The selenium drum, as a dedicated chest unit, offers high image quality at a 400-speed acquisition dose; however, its role has declined since the advent of DR systems.

    Currently it seems that hybrid solutions, in which both techniques, CR and DR, coexist, will probably remain prevalent in the foreseeable future.

  5. Page 39
    Correspondence: D. Tack, Dept of Radiology, RHMS-Clinique Louis Caty, Rue Louis Caty 136, B-7331, Baudour, Belgium.

    Since the early 1980s, computed tomography (CT) has been widely used as this technique provides precise anatomical details within the lungs, the mediastinum, and the chest wall. However, CT requires the use of X-rays, an ionising radiation. The collective radiation from CT is, therefore, in constant increase. As evaluated on atomic bomb survivors, ionising radiations induce an increase of the mortality by cancer, the rate being proportional to the dose. The radiation dose related to CT examinations is much higher than that related to chest radiographs, but both are in the field of so-called low-level radiations. In this range of radiation, as used for diagnostic purposes, no increase in cancer mortality has ever been detected.

    This chapter outlines the risk estimation in the field of low-level radiations, the various methods used to measure this radiation dose, CT parameters influencing the dose, dose comparisons between CT and most other imaging diagnostic techniques of the chest, the newly developed concept of low-dose CT, and discusses the most important unresolved questions regarding the dose in chest CT.

  6. Page 51
    Correspondence: T. Franquet, Dept of Radiology, Section of Thoracic Imaging, Hospital de Sant Pau, Universidad Autónoma de Barcelona, San Antonio Ma Claret 167, 08025 Barcelona, Spain.

    Imaging plays a crucial role in the detection and management of patients with pneumonia. This present chapter discusses the different imaging methods used in the diagnosis and management of suspected pulmonary infections. The imaging examination should always begin with conventional radiography. When the results of routine radiography are inconclusive, computed tomography is mandatory. The combination of pattern recognition with knowledge of the clinical setting is the best approach to the pulmonary infectious process. A specific pattern of involvement can help suggest a likely diagnosis in many instances. In AIDS patients, diffuse ground-glass and interstitial infiltrates are most commonly present in Pneumocystis carinii pneumonia whereas in the nonimmonosupressed patients, a segmental lobar infiltrate is suggestive of a bacterial pneumonia. Round pneumonia is more often encountered in children than in adults and is most often caused by Streptoccocus pneumoniae. Different combinations of parenchymal and pleural abnormalities may be suggestive for additional diagnoses. When an infectious pulmonary process is suspected, knowledge of the varied radiographical manifestations will narrow the differential diagnosis, helping to direct additional diagnostic measures, and serving as an ideal tool for follow-up examinations.

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    Correspondence: P. Scillia, Dept of Radiology, Erasme University Hospital, Route de Lennik 808, 1070 Brussels, Belgium.

    By definition, pulmonary oedema is an abnormal accumulation of water in the lung. Consequently, the computed tomography (CT) appearance of pulmonary oedema reflects the sequence of this accumulation. In early hydrostatic pulmonary oedema, CT scans show vascular engorgement and peribronchovascular cuffing, which increases with the severity of oedema and is associated in late stage, with consolidations. In acute respiratory distress syndrome, CT shows the proportion of injured parenchyma and depicts associated alterations as parenchymal infiltrate and consolidation, pleural effusion, and pneumothorax. These merely morphological findings can be complemented with data from objective CT analysis of the lung parenchyma. Indeed CT can assess lung water noninvasively. Correlated with hydrodynamic parameter, these objective measurements show that the increase of lung density parallels parenchymal fluid overload. These data also show that the occurrence of ground-glass opacities can precede the haemodynamic evidence of oedema.

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    Correspondence: M. Pistolesi, Dipartimento di Area Critica Medico Chirurgica, Unità Funzionale di Medicina Respiratoria, Università degli Studi di Firenze, Viale G. B. Morgagni 85-50134, Firenze, Italia.

    The diagnosis of pulmonary embolism (PE) is difficult because the clinical presentation is nonspecific and no single diagnostic test is sensitive enough and specific enough to exclude or confirm clinically suspected PE.

    Accurate clinical evaluation is the first and most important step to raise the suspicion of the disease and to set-up an appropriate diagnostic work-up. Several prospective studies have shown that pre-test clinical probability categorises patients into subgroups with different a prevalence for PE and that the positive and negative predictive value of various objective tests is strongly conditioned by the independently assessed pre-test clinical probability.

    Perfusion, rather than ventilation/perfusion, scanning should be the pulmonary vascular imaging technique of first choice for the management of patients with suspected PE because of its high sensitivity and negative predictive value. The clinical usefulness of spiral computed tomographical pulmonary angiography (CPTA) in the diagnosis of PE has not, as yet, been firmly established, since its sensitivity ranges from 57–100%, and its specificity from 78–100%. Such wide ranges are likely to reflect differences in the patients studied, as well as in the technology used.

    The diagnostic accuracy of CTPA in PE diagnosis is also dependent upon the location of emboli, since it is >90% for emboli involving central pulmonary vessels but decreases to much lower values for emboli confined to peripheral vessels. Recent and future technological developments of CTPA may greatly enhance the role of this technique in the diagnostic work-up of patients suspected of PE. The authors propose a noninvasive diagnostic strategy with high positive and negative predictive values, starting with a standardised assessment of clinical likelihood, followed by a perfusion lung scan and, eventually, by CTPA in patients with discordant clinical and scintigraphical findings.

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    Correspondence: D.M. Hansell, Dept of Radiology, Royal Brompton Hospital, Sydney Street, London, SW3 6NP, UK.

    Diseases affecting the small airways are difficult to detect by traditional diagnostic tests. Widespread involvement is needed before symptoms and abnormalities on pulmonary function testing or chest radiography become apparent. Obstruction of the bronchioles may be detected indirectly on computed tomography (CT) scans because regional under-ventilation results in reduced perfusion, which in turn is shown as a mosaic pattern of the lung parenchyma. When there is inflammation of the bronchioles with accompanying exudate, the airways may become directly visible on CT scans, e.g. in cases of diffuse panbronchiolitis. Quantification of the various morphological features of small-airways disease is possible from CT images and this increased precision has aided investigations of structure-function relationships. An understanding of the pathology and microscopic distribution of disease in relation to the airways allows some prediction of the likely CT appearances in this wide spectrum of conditions, and thus helps to refine differential diagnosis.

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    Correspondence: P.A. Gevenois, Dept of Radiology, Hôpital Erasme, Route de Lennik, 808, 1070 Brussels, Belgium.

    Accurate diagnosis and quantification of pulmonary emphysema during life is important to understand the natural history of the disease, to assess the extent of the disease, and to evaluate and follow-up therapeutic interventions. Since pulmonary emphysema is defined on pathological criteria, new methods of diagnosis and quantification should be validated by comparisons against histological references. Recent studies have addressed the capability of computed tomography (CT) to accurately quantify pulmonary emphysema. These studies, overviewed in this article, have been based on CT scans obtained after deep inspiration or expiration, on subjective visual grading and on objective measurements of attenuation values by using dedicated softwares providing numerical data, on two-dimensional and on three-dimensional approaches, and compared CT data with pulmonary function tests. More recently, textural analyses were applied on CT scans to assess the presence, the extent, and the types of emphysema.

    Quantitative CT has already been used in patient selection for surgical treatment of pulmonary emphysema and in pharmaco-therapeutical trials. However, despite numerous and extensive studies already available, this technique has not yet been standardised and important questions about how to best use the CT for the quantification of pulmonary emphysema are still unsolved.

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    Correspondence: S.M. Ellis, X-ray Dept, London Chest Hospital, Bonner Road, Bethnal Green, London E2 9JX, UK.

    The advent of high-resolution computed tomography (HRCT) has had a profound impact on the imaging of idiopathic interstitial pneumonitis (IIP). An increase in the understanding of the pathological processes occurring in the interstitium and alveolar airspaces in IIP, and observing a close correlation with high-resolution computed tomography (HRCT) findings has enabled radiology to provide discriminatory diagnostic information not possible from plain chest radiographs.

    This review summarises the various HRCT features that are associated with, and in some cases diagnostic of, specific IIPs but it must be emphasised that establishing a diagnosis requires clinical, radiological and often pathological information and even then will remain unclassified in some cases.

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    Correspondence: S.R. Desai, Dept of Radiology, King's College Hospital, Denmark Hill, London, SE5 9RS, UK.

    The management of lung disorders, as a consequence of collagen vascular disorder, is often difficult. Clinical evaluation alone will not detect or characterise the nature of lung involvement in many cases. Furthermore, the physiological profile in patients with collagen vascular disease may be complex, since pathological processes with opposing physiological effects often coexist.

    Histopathological examination of lung biopsy specimens in individual patients is notstraightforward because of issues of classification, observer variation between pathologists, and the multiplicity of pathological processes that can occur. Imaging studies are central to the management of patients with suspected lung disease in association with connective tissue disorders. In this regard, computed tomography (CT) has a central role; the sensitivity and accuracy of CT is higher than that of plain chest radiography. CT may also provide valuable clues about the morphological basis of sometimes complex lung pathology.

  13. Page 195

    Currently available results on computed tomography (CT) screening are all based on diagnostic-prognostic trials show that: 1) by appropriate definition of a positive result the work-up on baseline screening was confined to <15% and on annual repeat <6%, 2) screen diagnoses represented >95% of all diagnoses, and 3) >80% of all the diagnoses were of Stage I.

    With respect to the preliminary results of the significance of screen diagnoses, there was no evidence of over-diagnosis based on expert pathology review. Estimates based on growth rates, suggested that there were ≤15% baseline-diagnosed cancers and only very few of those were diagnosed on repeat screening. The preliminary results of the overall cure rate of screen-diagnosed lung cancer suggests that it may be raised to 50–60% as compared with that of usual care of 10% and that of chest radiographical screening of 20%.

    It is hoped that continued reporting of the long-term follow-up of diagnostic-prognostic trials which started in 1993 in the USA and Japan, together with preliminary results of the ongoing randomised trials will allow for progressive updating of the national policies for screening for lung cancer. It is also hoped that further analysis of the results of these trials will allow for the development of methodologies of evaluation which provide information on new diagnostic tests and their benefit in reducing death from cancer in a more reasonable time frame.

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    Correspondence: J. Verschakelen, Dept of Radiology, University Hospitals, Herestraat 49, B-3000 Leuven, Belgium.

    Computed tomography (CT) stays the routine imaging procedure for staging patients with nonsmall cell lung cancer because this technique provides the most detailed imaging information of the tumour and its extent. However, despite its high and continuously improving image quality, there are still a lot of cases where CT is not able to predict a correct tumour, metastases and node stage. Magnetic resonance imaging (MRI) may then be used, but MRI is not always able to solve the problem. Doing a positron emission tomography (PET) scan in addition to the CT examination is, at the present moment, probably the best way to perform TNM staging. This technique is especially valuable for mediastinal lymph node staging because it has a high negative predictive value meaning that a negative PET provides a >90% certainty of the absence of mediastinal lymph node metastases and justifies the ability to skip invasive diagnostic procedures and go directly to therapeutic surgery. Further studies are necessary, but it can be expected that PET can also be valuable during T-staging to differentiate between tumour and peritumoural atelectasis and inflammation. However, despite the fact that combining PET and CT improves the accuracy of mediastinal staging, very often a tissue diagnosis remains necessary. Mediastinoscopy is still generally considered the standard of care, although, newer minimally invasive biopsy techniques, such as transbronchial needle aspiration performed during bronchoscopy and especially endoscopic ultrasound with fine needle aspiration biopsy, receive increased attention in the literature. Most authors agree that an investigation for distant metastases should be started when the patient has signs and symptoms that might be caused by metastatic disease and when the patient has a primary tumour requiring extensive surgery. However, the approach to the detection of occult metastases remains controversial, both in terms of when to search and the optimal technique that should be used. PET can probably be important here also.

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    Correspondence: J.F. Vansteenkiste, Dept of Pulmonology, Respiratory Oncology Unit, University Hospital Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.

    Positron emission tomography (PET) is an excellent imaging modality for determining the metabolic status of tissues. The addition of 18F-2-fluoro-2-deoxy-glucose (FDG)-PET imaging to conventional imaging has consistently led to better accuracy in the diagnosis and staging of nonsmall cell lung cancer (NSCLC).

    PET is recommended for the assessment of a solitary pulmonary nodule, based on its excellent sensitivity and good specificity. However, the possibility of false-positive results in inflammatory lesions and false-negative results in metabolic low grade or subcentimetric lesions must be taken into account. PET is also recommended for the staging of untreated NSCLC with a potential for radical treatment. It gives additional value to conventional work-up for the evaluation of the mediastinum and extrathoracic structures. If the mediastinal staging is negative on PET, a mediastinoscopy may be omitted except in cases of a large central primary tumour, a large ipsilateral hilar adenopathy, or any primary tumour with low FDG-uptake. Pathological confirmation of positive mediastinal PET finding(s) or a solitary metastatic PET finding should be obtained before excluding patients from curative treatment.

    There is evidence that FDG-uptake on PET has independent prognostic value, and that measuring changes in FDG-uptake before and shortly after initiation of treatment is a sensitive marker of response, but improved standardisation and large-scale experience are needed before wide-spread use in these indications.

    PET is also useful in the evaluation of a persistent or new intrathoracic abnormality on computed tomography (CT) after radical therapy of NSCLC. PET influences radiotherapy planning in both NSCLC and small cell lung cancer, but the effect on outcome still needs to be demonstrated. The role of PET for mediastinal restaging after induction chemotherapy for locally advanced NSCLC needs further clarification.

    Recent combined PET-CT developments permit fusion of anatomic and functional information in one scanner, but the superiority of this approach compared with visual side-by-side comparison of PET and CT images still needs to be demonstrated.

  16. Page 265
    Correspondence: B. Ghaye, Dept of Medical Imaging, University Hospital Sart Tilman B 35, B–4000, Liège, Belgium.

    Interventional radiology is a technique based medical specialty, using all available imaging modalities (fluoroscopy, ultrasound, computed tomography: CT, magnetic resonance, angiography) for guidance of interventional techniques for diagnostic or therapeutic purposes. Actually, percutaneous transthoracic needle biopsy includes core needle biopsy besides fine needle aspiration. Any pleural, pulmonary or mediastinal fluid or gas collection is amenable to percutaneous pulmonary catheter drainage. Different energy modes can be used for transthoracic needle treatment of thoracic malignancies. Treatment of haemoptysis of bronchial artery or pulmonary artery origin, transcatheter embolisation of pulmonary arteriovenous malformations and pseudoaneurysms, angioplasty and stenting of the superior vena caval system and percutaneous foreign body retrieval are well established routine procedures, precluding unnecessary surgery. These techniques are safe and effective in experienced hands. CT is helpful in pre- and post-operative imaging of patients being considered for endobronchial stenting. Many procedures can be performed on an outpatient basis, thus increasing cost effectiveness of radiologically guided interventions in the thorax.

  17. Page 302
    Correspondence: G.R. Ferretti, Service Central de Radiologie et Imagerie Médicale, Centre Hospitalier Universitaire, Grenoble BP 217, F-38043 Grenoble cedex 09, France.

    Volume computed tomography (VCT) using multidetector technology allows for true high resolution volume acquisition of the entire thorax with 1-mm slice collimation during a single apnoea in a time ≤10 s. Combination of VCT acquisition with synchronous vascular enhancement gives rise of VCT angiography (VCTA). In the last decade, VCT and VCTA have revolutionised noninvasive diagnosis of thoracic diseases, modifying many diagnostic algorithms. Because VCT provides for isotropic voxels, two- and three-dimensional (3D) rendering techniques reach the same high quality in every direction of projection. As these 3D rendering techniques present the VCT data in formats other than the conventional trans-axial computed tomography slices, they can be summarised as virtual tools. The purpose of this review is to give the readers the most important technical aspects of virtual tools, to report their application to the thorax, to answer clinical and scientific questions, and to stress their importance for patient management, clinical decision making, and research.

  18. Page 325
    Correspondence: H-U. Kauczor, Dept of Radiology, Germen Cancer Research Centre, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.

    Traditionally, radiology of the lung was focused on imaging of structure, whereas only nuclear medicine provided a kind of functional assessment. New developments in magnetic resonance imaging (MRI) have opened up the field of functional imaging of ventilation. These techniques consist of administration of hyperpolarised noble gases, in particular helium-3 (3He), as well as oxygen, at different concentrations as tracer gases. Such studies predominantly provide regional details on gas distribution which can be assessed in a single breath-hold (ventilation defects) or dynamically (distribution kinetics) by 3He MRI or after averaging of multiple breaths (distribution defects) by oxygen-enhanced proton MRI. Additionally, investigations of oxygen uptake are feasible by both techniques, providing a complementary indirect assessment of pulmonary perfusion at the same time. Dedicated techniques also enable a novel approach to the characterisation of pulmonary microstructure. These new techniques have been applied in multiple preliminary studies especially: chronic airway disease, which have demonstrated a very high sensitivity for the detection of ventilation defects superior to computed tomography; nuclear medicine; or pulmonary function testing. With the introduction of standardised procedures, good reproducibility has been achieved. Together with quantifiable results these technique will now be applied to the detection and monitoring of the effects of drugs, e.g. bronchodilators. However, the specificity of ventilation MRI for a particular diagnosis is low. The assessment of clinical utility in chronic airway disease, chronic obstructive pulmonary disease, asthma, cystic fibrosis and bronchiolitis obliterans, is still ongoing.

  19. Page 343
    Correspondence: D.L. Levin, Dept of Radiology, Mail Code 8756, UCSD Medical Center, 200 West Arbor Drive, San Diego, CA 92103-8756, USA.

    Magnetic resonance imaging is infrequently used for the evaluation of suspected pulmonary disease. However, advanced techniques allow for both qualitative and quantitative evaluation of pulmonary blood flow. Currently, these techniques are limited primarily to the evaluation of suspected pulmonary embolism. However, they have the potential to contribute to greatly to the present understanding of normal pulmonary physiology and the development of pulmonary disease.