[Idiopathic pulmonary fibrosis : Radiological diagnosis in light of the current guidelines]

Idiopathic pulmonary fibrosis (IPF) is a specific form of chronic progressive fibrosing interstitial lung disease with a poor prognosis. High-resolution computed tomography (HRCT) plays an important role in the work-up of patients with suspected IPF. In HRCT IPF is characterized by the pattern of usual interstitial pneumonia (UIP). For a long time only supportive or immunosuppressive treatment was possible. The approval of antifibrotic agents in 2012 marked a turning point and triggered further clinical and scientific interest. Based on the recently gained knowledge the revised version of the international guidelines for the diagnosis of IPF was published in 2018, including instructions for HRCT interpretation. In this continued medical education article the relevant signs in HRCT are presented. The specifications given in the guidelines are elucidated.

[Mimics of lung cancer]

Lung cancer is a histologically, immunologically and therefore morphologically and functionally very heterogeneous group of neoplasms with the highest cancer mortality worldwide. Therefore, the range of diseases mimicking lung cancer is also very broad and includes congenital, infectious and inflammatory changes as well as other benign space-occupying lesions and other primary and secondary pulmonary neoplasms. The difficulty in radiology lies in the ability to diagnose lung cancer with a high degree of certainty. This must take the limits of the specific diagnosis, knowledge of the classical pitfalls and rare entities that can imitate lung cancer into consideration. Narrowing the differential diagnosis requires close interdisciplinary cooperation and consideration of the patient's clinical and medical history. An accurate analysis of the computed tomography (CT) pattern and distribution of the lesions as well as consideration of additional changes and involvement of other organ systems can be the key to the diagnosis. The use of fluorodeoxyglucose positron-emission tomography CT (FDG-PET-CT) is helpful only in a few mimics of lung cancer. The article describes clinical and radiological findings of mimics of lung cancer also pointing out the limitations of CT and PET-CT for the diagnosis.

[Cysts in the lung : A practical guide to differential diagnosis]

Solitary or multiple pulmonary cysts are a relatively rare finding and should always prompt the search for an underlying cause. High-resolution computed tomography (HRCT) plays a crucial role in the differential diagnosis with morphological findings, such as cyst shape and size, wall consistency, number, distribution and localization of the cysts being the important criteria. The differentiation of diseases with multiple, diffusely distributed cysts from diseases with single or grouped cysts facilitates the definition of the final diagnosis. Associated pulmonary findings, such as nodules, ground-glass opacities and fibrosis or pleural changes also play a role. Possible underlying diseases can have systemic, inhalative, traumatic, genetic or infectious causes.

Image Quality in Chest Radiography: Abstract

Image quality in chest radiography is an important, but complex, subject. The complicated anatomy of the chest, as well as the various ways that chest disease may manifest itself, require careful consideration of radiographic technique. The manner in which human observers deal with the complexity of chest images adds further dimensions to image analysis that are not found in other radiography examinations. This report describes many issues that are related to the quality of chest radiographic images. In so doing, it relies upon the very extensive literature on this topic, a topic that has been one of the most thoroughly studied in all of radiography. Strategies that are generally agreed to improve the quality of chest radiographs are described, as are approaches to the assessment of image quality.

Corrigendum: Towards automatic pulmonary nodule management in lung cancer screening with deep learning

This corrects the article DOI: 10.1038/srep46479.

Circulation stabilizing therapy and pulmonary high-resolution computed tomography in a porcine brain-dead model

BACKGROUND

Currently 80% of donor lungs are not accepted for transplantation, often due to fluid overload. Our aim was to investigate if forced fluid infusion may be replaced by a new pharmacological therapy to stabilize circulation after brain death in an animal model, and to assess therapy effects on lung function and morphology trough blood gas parameters and state-of-the-art High-resolution CT (HRCT).

METHODS

Brain death was caused by surgical decapitation. To maintain mean aortic pressure > 60 mmHg, pigs were treated with forced electrolyte solution infusion (GI; n = 6) or the pharmacological therapy (GII; n = 11). GIII (n = 11) were non-decapitated controls. Lung function was investigated with blood gases and lung morphology with HRCT.

RESULTS

GI pigs became circulatory instable 4-6 h after brain death in spite of forced fluid infusion, five pigs showed moderate to severe pulmonary edema on HRCT and median final PaO2 /FiO2 was 29 kPa (Q1; Q3; range 26; 40; 17-76). GII and GIII were circulatory stable (mean aortic pressure > 80 mmHg) and median final PaO2 /FiO2 after 24 h was 72 kPa (Q1; Q3; range 64; 76; 53-91) (GII) and 66 kPa (55; 78; 43-90) (GIII). On HRCT, only two pigs in GII had mild pulmonary edema and none in GIII. More than 50% of HRCT exams revealed unexpected lung disease even in spite of PaO2 /FiO2 > 40 kPa.

CONCLUSION

Pharmacological therapy but not forced fluid infusion prevented circulatory collapse and extensive HRCT verified pulmonary edema after acute brain death. HRCT was useful to evaluate lung morphology and revealed substantial occult parenchymal changes justifying efforts toward a more intense use of HRCT in the pre-transplant evaluation.

[Detection of lung nodules. New opportunities in chest radiography]

BACKGROUND

Chest radiography still represents the most commonly performed X-ray examination because it is readily available, requires low radiation doses and is relatively inexpensive. However, as previously published, many initially undetected lung nodules are retrospectively visible in chest radiographs.

STANDARD RADIOLOGICAL METHODS

The great improvements in detector technology with the increasing dose efficiency and improved contrast resolution provide a better image quality and reduced dose needs.

METHODICAL INNOVATIONS

The dual energy acquisition technique and advanced image processing methods (e.g. digital bone subtraction and temporal subtraction) reduce the anatomical background noise by reduction of overlapping structures in chest radiography. Computer-aided detection (CAD) schemes increase the awareness of radiologists for suspicious areas.

RESULTS

The advanced image processing methods show clear improvements for the detection of pulmonary lung nodules in chest radiography and strengthen the role of this method in comparison to 3D acquisition techniques, such as computed tomography (CT).

ASSESSMENT

Many of these methods will probably be integrated into standard clinical treatment in the near future. Digital software solutions offer advantages as they can be easily incorporated into radiology departments and are often more affordable as compared to hardware solutions.

[HRCT patterns of the most important interstitial lung diseases]

Interstitial lung diseases are a mixed group of diffuse parenchymal lung diseases which can have an acute or chronic course. Idiopathic diseases and diseases with an underlying cause (e.g. collagen vascular diseases) share the same patterns. Thin section computed tomography (CT) plays a central role in the diagnostic work-up. The article describes the most important interstitial lung diseases following a four pattern approach with a predominant nodular or reticular pattern or a pattern with increased or decreased lung density.

[Management of subsolid pulmonary nodules]

The finding of subsolid pulmonary nodules poses a frequent problem in the daily routine of the radiologist. The biological behavior of such subsolid lesions differs significantly from solid nodules. The risk of malignancy is significantly higher in subsolid nodules as compared to solid or purely ground glass opacities or nodules. The recommendations regarding the diagnostic management of subsolid nodules have been adapted according to the tendency of growth and the risk of malignancy. A benign etiology is also seen quite often in subsolid lesions and in this case they will show a reduction of size or disappear completely by the follow-up examination. Therefore, in many cases a short-term follow-up examination is primarily recommended. As the findings will often show no changes for a long period of time, further annual follow-up examinations over a longer, not yet specified period of time are recommended. Subsolid lesions that grow in size and/or show an increase in density or develop a solid part within a ground glass lesion should remain as suspected malignancies until proven otherwise.

[Conventional and CT diagnostics of bronchial carcinoma]

A number of important technical advances made in recent years in the area of both digital radiography as well as multidetector computed tomography (MDCT) have improved detection and staging of bronchial carcinoma. The aim of elaborate processing such as temporal subtraction, rib suppression, dual energy subtraction or CAD is to aid the radiologist in detecting lung tumors at the earliest stage possible. For both CT and radiography techniques the differentiation between true and false positive lesions seems to be the biggest challenge. MDCT with multiplanar projections is the imaging method of choice for staging of the extent of local tumor spread (T staging), while N staging and M staging are the domain of positron emission tomography (PET) or even better of integrated PET/CT. Management rules for follow-up of solid and semi-solid lesions seen in CT consider the risks of the patient and are summarized in international guidelines. In 2009 a new 7th edition of the TNM classification was published, which, among other aspects, sub-classifies tumor size more specifically and the presence of a satellite nodule in the tumor lobe is down-staged to T3 and no longer determines tumor resectability. The N staging was not modified. One of the most important new features is the fact that the new classification no longer applies only to non-small cell lung cancer (NSCLC) but also to SCLC and carcinoid tumors.

[Radiological diagnostics of Hodgkin- and non-Hodgkin lymphomas of the thorax]

Malignant lymphomas belong to the most important malignant diseases in western countries with an increasing incidence of Non-Hodgkin lymphoma. The thorax is the location of primary manifestation especially in patients with Hodgkin's disease. Progression of disease and therapy associated complications are frequently located in the chest. Based on morphological imaging criteria the two types of lymphoma cannot be differentiated, helpful for differentiation is, however, the way of disease spread. Primary and secondary thoracic lymphoma represent a diagnostic challenge in radiology: the patterns are variable in radiography as well as in computed tomography and alter under therapy. Radiological studies, especially CT, are an integral part of the staging process. MRI is considered advantageous for chest wall disease. PET as functional imaging technique has its proven role for staging of high grade lymphomas, the combination of functional and morphological information provided by PET-CT will become the first diagnostic standard in the future.

[Digital thorax radiography: flat-panel detector or storage phosphor plates]

Flat panel detectors are characterized by improved handling and increased dose efficiency. This allows for increasing of work flow efficiency and for reducing the exposure dose by about 50% compared to current systems with a sensitivity of 400. Whether the increased dose efficiency should be used to reduce acquisition dose or to increase image quality in the chest, will be shown by further clinical experience and will be also determined by the subjective preference of the radiologists. The decreased level of image noise opens new perspectives for image processing that way that elaborated multifrequency processing allows for optimizing the display of very small and low contrast structures that was so far limited by overlying image noise. Specialized applications of dual energy subtraction and temporal subtraction will also profit by the new detector technology and will be further driven forward in context with applications such as computed assisted diagnosis even though this is currently not yet broadly applied. Storage phosphor radiography still represents an important alternative technique based on its larger flexibility with respect to equipment configuration, its broader application options in intensive care and emergency radiology and due to economic reasons. These facts are further underlined by the fact that image quality also in storage phosphor radiography could be constantly increased by improving detector technology and image processing and consequently has a high standard.

New imaging techniques in the treatment guidelines for lung cancer

Computed tomography (CT) remains the main imaging technique for the preoperative staging and post-therapeutic evaluation of bronchogenic carcinoma. Spiral CT has already overcome some of the problems encountered with central or more extensive tumours. Multislice CT offers further improvement and allows for scanning of the whole chest within a single breath-hold using a thin-section high-resolution technique. Problem-adapted sections in arbitrary directions become available and provide an excellent spatial resolution. One can expect improved accuracy for the evaluation of transfissural tumour growth, chest wall involvement, mediastinal infiltration and lymph node staging. Despite recent advances in magnetic resonance (MR) techniques for imaging the chest, the role of MR for staging of bronchogenic carcinoma remains limited. It offers advantages such as the assessment of chest-wall involvement or mediastinal involvement in patients in whom CT remains equivocal. Lymph-node-specific MR contrast agents offer new diagnostic potential for the assessment of metastatic disease. New techniques for the display of three-dimensional data sets include volume rendering and virtual bronchoscopy. These techniques represent new tools for the evaluation and demonstration of pathology within the central tracheobronchial tree. Their most important application is the guidance of bronchoscopic biopsies. The assessment of an indeterminate pulmonary nodule is frequently based on positron emission tomography imaging. As an alternative, nodule vascularization (contrast enhancement patterns on CT or magnetic resonance imaging (MRI)), calcifications (absorption characteristics at various X-ray energies on CT or dual energy radiography), and morphological features (high resolution imaging at CT) can be used as the basis for nodule differentiation. The dynamics of contrast enhancement in CT or MRI can also be used for the assessment of tumour viability after chemotherapy. Lung cancer screening programmes are still controversial. Low-dose computed tomography scanning and computed assisted detection algorithms based on chest radiographs or computed tomography scans form the technical basis for such projects.

Changes in lung parenchyma after acute respiratory distress syndrome (ARDS): assessment with high-resolution computed tomography

The aim of this study was to evaluate the appearance, extent, and distribution of parenchymal changes in the lung after acute respiratory distress syndrome (ARDS) as a function of disease severity and therapeutic procedures. High-resolution computed tomography (HRCT), clinical examination, and lung function tests were performed in 15 patients, 6-10 months after ARDS. The appearance and extent of parenchymal changes were compared with the severity of ARDS, as well as with clinical and therapeutic data. Lung parenchymal changes resembling those found in the presence of pulmonary fibrosis were observed in 13 of 15 patients (87%). The changes were significantly more frequent and more pronounced in the ventral than in the dorsal portions of the lung ( p<0.01). A significant correlation was observed between the extent of lung alterations and the severity of ARDS ( p<0.01), and the duration in which patients had received mechanical ventilation either with a peak inspiratory pressure greater than 30 mmHg ( p<0.05), or with more than 70% oxygen ( p<0.01). Acute respiratory distress syndrome frequently is followed by fibrotic changes in lung parenchyma. The predominantly ventral distribution of these changes indicates that they may be caused by the ventilation regimen and the oxygen therapy rather than by the ARDS.

[Radiological diagnosis of adult respiratory distress syndrome (ARDS)]

The bedside chest radiograph represents the imaging modality of choice for diagnosis and monitoring of adult respiratory distress syndrome (ARDS). Imaging findings are strongly influenced by means of mechanical ventilation therapy. The chest radiograph is relatively insensitive and not specific for the diagnosis of complications such as pneumonia or interstitial emphysema. Computed tomography (CT) is suitable for quantitative assessment of lung compartments with respect to the degree of aeration and to tissue density values. With CT, the understanding of the underlying pathophysiology and the effects of ventilation therapy (PEEP) could be improved. The role of CT in the clinical routine is still limited due to the high risk to transport patients with ARDS.

High-resolution CT of diffuse interstitial lung disease: key findings in common disorders

High-resolution CT (HRCT) is the radiological imaging technique that most closely reflects changes in lung structure. It represents the radiological method of choice for the diagnostic work-up of patients with known or suspected diffuse interstitial lung disease. A single HRCT finding is frequently nonspecific, but the combination of the various HRCT findings together with their anatomic distribution can suggest the most probable diagnosis. The purpose of this article is to summarize the classic HRCT features of the most common diffuse interstitial lung diseases. Lists of differential diagnoses and distinguishing key features are provided to improve diagnostic confidence. The presence of classic HRCT features often obviates the need for biopsy. In patients with atypical findings, HRCT can be used to determine the most appropriate biopsy site.

[Current development sin the area of digital thoracic radiography]

All three currently commercially available systems for digital radiography of the chest such as the selenium drum, storage phosphor plates and the flat panel direct detector systems provide an excellent image quality that is at least equivalent or superior to that of conventional film. Reasons for that are the continuously improved detective or dose efficiency of the detector systems and an improved image processing. The new direct detector systems have the largest potential for dose reduction while storage phosphor and selenium radiographs are usually obtained with a dose comparable to that of a 400 speed system. Improved image processing algorithms allow for the production of digital images that are adapted to the conventional image characteristics within the lung regions combined with an increased transparency of the high absorption areas such as the retrocardial and retrodiaphragmatic regions.

[Chest X-ray of the neonate]

In diagnostic imaging of thoracic pathologies in mature and especially immature neonates, chest X-ray has a leading position. Profound knowledge of the normal chest X-ray and the potential physiological perinatal changes is the basic requirement for interpretation of the X-ray of a neonate. Childhood pathology: Many congenital and acquired diseases that the radiologist is faced with in neonatology are unknown in the imaging of adults. Many of these changes are life-threatening or may have an impact on the patient's future quality of life. Therefore early diagnosis in close cooperation with the paediatrician is essential. We give here an overview of the most important pathologic changes that the radiologist may be confronted with in daily routine.

[Spiral CT of the lung. Technique, findings, value]

Spiral CT allows for examination of the whole chest within a single breathhold. As compared to standard CT, spiral CT has an increased sensitivity for the detection of pulmonary nodules, of small mediastinal and bronchopulmonary lymph nodes, and of pleural plaques improves characterization of lesion morphology. New diagnostic applications include the detection of very subtle diffuse lung disease and the diagnosis of pulmonary embolism and vascular malformations. For the diagnosis of tracheobronchial pathology, spiral CT is an ideal supplement to bronchoscopy.

[Basic principles of vascular imaging with spiral CT]

Vascular investigations by CT have experienced a decisive advance and found a high acceptance since the introduction of fast volume scanning (spiral CT). We have investigated the underlying physical foundations and optimized the operational aspects of the method now introduced as CT angiography (CTA). Investigations are carried out with a table feed of 1-10 mm/s. Images are reconstructed at 1-2 mm separations by use of algorithms which optimize the layer profile. The parameters must be adapted to the region being investigated. The diagnosis is generally made with interactive cine runs; for this the original images, multiplanar reformations, 3D surface shaded displays (SSD), and maximum intensity projection (MIP) images are used. The 3D representations are discussed in the context of the principle and illustrative examples. Important applications for CTA are the evaluation of aortic aneurysms and dissections, pulmonary vessels, renal arteries, and vessel stents. CTA is characterized by short examination times, low invasiveness, and relatively low cost; in typical cases it is associated with an effective dose of 2-10 mSv. The advantages and disadvantages of the new method are discussed in terms of diagnostic value, image quality, patient dose, contrast medium techniques, and practical aspects in comparison to other angiographic methods.