[CF Lung Disease - a German S3 Guideline: Module 2: Diagnostics and Treatment in Chronic Infection with Pseudomonas aeruginosa]

Cystic Fibrosis (CF) is the most common autosomal-recessive genetic disease affecting approximately 8000 people in Germany. The disease is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene leading to dysfunction of CFTR, a transmembrane chloride channel. This defect causes insufficient hydration of the epithelial lining fluid which leads to chronic inflammation of the airways. Recurrent infections of the airways as well as pulmonary exacerbations aggravate chronic inflammation, lead to pulmonary fibrosis and tissue destruction up to global respiratory insufficiency, which is responsible for the mortality in over 90 % of patients. The main aim of pulmonary treatment in CF is to reduce pulmonary inflammation and chronic infection. Pseudomonas aeruginosa (Pa) is the most relevant pathogen in the course of CF lung disease. Colonization and chronic infection are leading to additional loss of pulmonary function. There are many possibilities to treat Pa-infection. This is a S3-clinical guideline which implements a definition for chronic Pa-infection and demonstrates evidence-based diagnostic methods and medical treatment for Pa-infection in order to give guidance for individual treatment options.

Imaging of Cystic Fibrosis Lung Disease and Clinical Interpretation

Progressive lung disease in cystic fibrosis (CF) is the life-limiting factor of this autosomal recessive genetic disorder. Increasing implementation of CF newborn screening allows for a diagnosis even in pre-symptomatic stages. Improvements in therapy have led to a significant improvement in survival, the majority now being of adult age. Imaging provides detailed information on the regional distribution of CF lung disease, hence longitudinal imaging is recommended for disease monitoring in the clinical routine. Chest X-ray (CXR), computed tomography (CT) and magnetic resonance imaging (MRI) are now available as routine modalities, each with individual strengths and drawbacks, which need to be considered when choosing the optimal modality adapted to the clinical situation of the patient. CT stands out with the highest morphological detail and has often been a substitute for CXR for regular severity monitoring at specialized centers. Multidetector CT data can be post-processed with dedicated software for a detailed measurement of airway dimensions and bronchiectasis and potentially a more objective and precise grading of disease severity. However, changing to CT was inseparably accompanied by an increase in radiation exposure of CF patients, a young population with high sensitivity to ionizing radiation and lifetime accumulation of dose. MRI as a cross-sectional imaging modality free of ionizing radiation can depict morphological hallmarks of CF lung disease at lower spatial resolution but excels with comprehensive functional lung imaging, with time-resolved perfusion imaging currently being most valuable.

KEY POINTS

• Hallmarks are bronchiectasis, mucus plugging, air trapping, perfusion abnormalities, and emphysema.• Imaging is more sensitive to disease progression than lung function testing.• CT provides the highest morphological detail but is associated with radiation exposure.• MRI shows comparable sensitivity for morphology but excels with additional functional information.• MRI sensitively depicts reversible abnormalities such as mucus plugging and perfusion abnormalities. Citation Format: • Wielpütz MO, Eichinger M, Biederer J et al. Imaging of Cystic Fibrosis Lung Disease and Clinical Interpretation. Fortschr Röntgenstr 2016; 188: 834 - 845.

[Role of MRI for detection and characterization of pulmonary nodules]

BACKGROUND

Due to physical and technical limitations, magnetic resonance imaging (MRI) has hitherto played only a minor role in image-based diagnostics of the lungs. However, as a consequence of important methodological developments during recent years, MRI has developed into a technically mature and clinically well-proven method for specific pulmonary questions.

OBJECTIVES AND METHODS

The purpose of this article is to provide an overview on the currently available sequences and techniques for assessment of pulmonary nodules and analyzes the clinical significance according to the current literature. The main focus is on the detection of lung metastases, the detection of primary pulmonary malignancies in high-risk individuals and the differentiation between pulmonary nodules of benign and malignant character.

RESULTS AND CONCLUSION

The MRI technique has a sensitivity of approximately 80 % for detection of malignant pulmonary nodules compared to the reference standard low-dose computed tomography (CT) and is thus somewhat inferior to CT. Advantages of MRI on the other hand are a higher specificity in differentiating malignant and benign pulmonary nodules and the absence of ionizing radiation exposure. A systematic use of MRI as a primary tool for detection and characterization of pulmonary nodules is currently not recommended due to insufficient data. The diagnostic potential of MRI for early detection and staging of malignant pulmonary diseases, however, seems promising. Therefore, further evaluation of MRI as a secondary imaging modality in clinical trials is highly warranted.

Functional magnetic resonance imaging of the lung

Beyond being a substitute for X-ray, computed tomography, and scintigraphy, magnetic resonance imaging (MRI) inherently combines morphologic and functional information more than any other technology. Lung perfusion: The most established method is first-pass contrast-enhanced imaging with bolus injection of gadolinium chelates and time-resolved gradient-echo (GRE) sequences covering the whole lung (1 volume/s). Images are evaluated visually or semiquantitatively, while absolute quantification remains challenging due to the nonlinear relation of T1-shortening and contrast material concentration. Noncontrast-enhanced perfusion imaging is still experimental, either based on arterial spin labeling or Fourier decomposition. The latter is used to separate high- and low-frequency oscillations of lung signal related to the effects of pulsatile blood flow. Lung ventilation: Using contrast-enhanced first-pass perfusion, lung ventilation deficits are indirectly identified by hypoxic vasoconstriction. More direct but still experimental approaches use either inhalation of pure oxygen, an aerosolized contrast agent, or hyperpolarized noble gases. Fourier decomposition MRI based on the low-frequency lung signal oscillation allows for visualization of ventilation without any contrast agent. Respiratory mechanics: Time-resolved series with high background signal such as GRE or steady-state free precession visualize the movement of chest wall, diaphragm, mediastinum, lung tissue, tracheal wall, and tumor. The assessment of volume changes allows drawing conclusions on regional ventilation. With this arsenal of functional imaging capabilities at high spatial and temporal resolution but without radiation burden, MRI will find its role in regional functional lung analysis and will therefore overcome the sensitivity of global lung function analysis for repeated short-term treatment monitoring.

Inter-observer reproducibility of semi-automatic tumor diameter measurement and volumetric analysis in patients with lung cancer

OBJECTIVES

Therapy monitoring in oncologic patient requires precise measurement methods. In order to improve the precision of measurements, we used a semi-automated generic segmentation algorithm to measure the size of large lung cancer tumors. The reproducibility of computer-assisted measurements were assessed and compared with manual measurements.

METHODS

CT scans of 24 consecutive lung cancer patients who were referred to our hospital over a period of 6 months were analyzed. The tumor sizes were measured manually by 3 independent radiologists, according to World Health Organization (WHO) and the Revised Response Evaluation Criteria in Solid Tumors (RECIST) guidelines. At least 10 months later, measurements were repeated semi-automatically on the same scans by the same radiologists. The inter-observer reproducibility of all measurements was assessed and compared between manual and semi-automated measurements.

RESULTS

Manual measurements of the tumor longest diameter were significantly (p < 0.05) smaller compared with the semi-automated measurements. The intra-rater correlations coefficients were significantly higher for measurements of longest diameter (intra-class correlation coefficients: 0.998 vs. 0.986; p < 0.001) and area (0.995 vs. 0.988; p = 0.032) using semi-automated compared with manual method. The variation coefficient for manual measurement of the tumor area (WHO guideline, 15.7% vs. 7.3%) and the longest diameter (RECIST guideline, 7.7% vs. 2.7%) was 2-3 times that of semi-automated measurement.

CONCLUSIONS

By using computer-assisted size assessment in primary lung tumor, interobserver-variability can be reduced to about half to one-third compared to standard manual measurements. This indicates a high potential value for therapy monitoring in lung cancer patients.

[Chronic obstructive pulmonary disease, periorbital and subconjunctival swelling]

A 70-year-old man with a history of chronic obstructive pulmonary disease (COPD) and dilative cardiomyopathy was referred due to acute dyspnea and chest pain. After spontaneous pneumothorax was confirmed by chest radiography, a chest tube was inserted into the right side. Persistent air bubbles escaping through the water seal of the drainage in synchrony with respiration indicated a bronchopleural fistula. A physical examination revealed orbital and subconjunctival emphysemas. Skull and chest computed tomography (CT) scans showed further massive cervical, thoracic and pulmonary subcutaneous emphysemas which are increased subcutaneous amounts of gas which can disperse along the fasciae. Cardinal sign is the sensation of air under the skin known as subcutaneous crepitation (similiar to touching rice crispies). Conditions causing subcutaneous emphysemas are trauma, medical treatment and intracutaneous gas production by bacteria. In this case, large amounts of air leaked out of the pleural space through the incision made for the chest tube into the subcutaneous tissue, mediastinum and retroperitoneum causing subcutaneous emphysemas. From there, ascending air spread along the fascial planes of the mediastinum and cervical area through the inferior orbital fissure to the orbits and eyelids causing orbital and subconjunctival emphysemas. On the basis of the progressive emphysemas and persistent pneumothorax, a second chest tube was inserted. Subsequently, the signs and symptoms disappeared completely.

[Dyspnea, fatigue and subpulmonary mass]

A 52-year-old man was referred for progressive dyspnea and fatigue. The medical history was unremarkable and there were no signs of late infections or previous tumorous diseases. Physical examination revealed diminished breath sounds and a dull tone over the right lower side. Routine blood tests, arterial blood gas and body plethysmography were all within normal ranges. Chest X-ray and thorax computed tomography (CT) showed the presence of a homogeneous subpulmonary mass with a diameter of 10 cm which had a water-like density of approximately 1 Hounsfield unit (HU). The presence of an extraordinary large pericardial cyst compromising the right lower lobe and therefore causing dyspnea was confirmed by video-assisted thoracoscopic surgery (VATS). Pericardial cysts are rare congenital mediastinal masses. They are usually asymptomatic and are usually found incidentally during routine chest X-ray, CT, magnetic resonance imaging (MRI) or echocardiography. Most pericardial cysts are situated at the right cardiophrenic angle. When reaching a relevant size they can cause symptoms such as dyspnea, coughing, chest pain and fatigue. The imaging studies most useful for diagnosis are CT, MRI and echocardiography. Differential diagnoses are diaphragmatic hernia, trapped pleural effusion or other pleural or mediastinal tumors.

MRI of the lung (1/3): methods

Proton magnetic resonance imaging (MRI) has recently emerged as a clinical tool to image the lungs. This paper outlines the current technical aspects of MRI pulse sequences, radiofrequency (RF) coils and MRI system requirements needed for imaging the pulmonary parenchyma and vasculature. Lung MRI techniques are presented as a “technical toolkit”, from which MR protocols will be composed in the subsequent papers for comprehensive imaging of lung disease and function (parts 2 and 3). This paper is pitched at MR scientists, technicians and radiologists who are interested in understanding and establishing lung MRI methods. Images from a 1.5 T scanner are used for illustration of the sequences and methods that are highlighted.

Main Messages

• Outline of the hardware and pulse sequence requirements for proton lung MRI

• Overview of pulse sequences for lung parenchyma, vascular and functional imaging with protons

• Demonstration of the pulse-sequence building blocks for clinical lung MRI protocols

[Moving pleural mass]

A 74-year-old man with bronchial carcinoma underwent radiofrequency ablation (RFA) due to poor pulmonary function. Therefore non-enhanced computed tomography (CT) of the chest was performed on two subsequent days. Besides the tumor, the CT scans showed a moving calcification in the pleural cavity. This extremely rare condition called thoracolithiasis is usually an incidental finding. Mostly it is asymptomatic and does not require any treatment. It should be considered as a differential diagnosis of a peripheral pulmonary nodule.

MRI of the lung (2/3). Why … when … how?

BACKGROUND

Among the modalities for lung imaging, proton magnetic resonance imaging (MRI) has been the latest to be introduced into clinical practice. Its value to replace X-ray and computed tomography (CT) when radiation exposure or iodinated contrast material is contra-indicated is well acknowledged: i.e. for paediatric patients and pregnant women or for scientific use. One of the reasons why MRI of the lung is still rarely used, except in a few centres, is the lack of consistent protocols customised to clinical needs.

METHODS

This article makes non-vendor-specific protocol suggestions for general use with state-of-the-art MRI scanners, based on the available literature and a consensus discussion within a panel of experts experienced in lung MRI.

RESULTS

Various sequences have been successfully tested within scientific or clinical environments. MRI of the lung with appropriate combinations of these sequences comprises morphological and functional imaging aspects in a single examination. It serves in difficult clinical problems encountered in daily routine, such as assessment of the mediastinum and chest wall, and even might challenge molecular imaging techniques in the near future.

CONCLUSION

This article helps new users to implement appropriate protocols on their own MRI platforms. Main Messages • MRI of the lung can be readily performed on state-of-the-art 1.5-T MRI scanners. • Protocol suggestions based on the available literature facilitate its use for routine • MRI offers solutions for complicated thoracic masses with atelectasis and chest wall invasion. • MRI is an option for paediatrics and science when CT is contra-indicated.

In vivo monitoring of cystic fibrosis-like lung disease in mice by volumetric computed tomography

The onset and spontaneous development of cystic fibrosis (CF) lung disease remain poorly understood. In the present study, we used volumetric computed tomography (VCT) as a new method for longitudinal in vivo monitoring of early lesions and disease progression in CF-like lung disease in β-epithelial Na(+) channel (ENaC)-transgenic (TG) mice. Using a VCT scanner prototype (80 kV, 50 mA·s, scan time 19 s and spatial resolution 200 μm), βENaC-TG mice and wild-type (WT) littermates were examined longitudinally at 10 time-points from neonatal to adult ages, and VCT images were assessed by qualitative and quantitative morphological parameters. We demonstrate that VCT detected early-onset airway mucus obstruction, diffuse infiltrates, atelectasis and air trapping as characteristic abnormalities in βENaC-TG mice. Furthermore, we show that early tracheal mucus obstruction predicted mortality in βENaC-TG mice and that the density of lung parenchyma was significantly reduced at all time-points in βENaC-TG compared with WT mice (median ± sem -558 ± 8 HU in WT versus -686 ± 16 HU in βENaC-TG at 6 weeks of age; p < 0.005). Our study demonstrates that VCT is a sensitive, noninvasive technique for early detection and longitudinal monitoring of morphological abnormalities of CF-like lung disease in mice, and may thus provide a useful tool for pre-clinical in vivo evaluation of novel treatment strategies for CF.

[New procedures. Comprehensive staging of lung cancer by MRI]

Lung cancer staging according to the TNM system is based on morphological assessment of the primary cancer, lymph nodes and metastases. All aspects of this important oncological classification are measurable with MRI. Pulmonary nodules can be detected at the clinically relevant size of 4-5 mm in diameter. The extent of mediastinal, hilar and supraclavicular lymph node affection can be assessed at the same time. The predominant metastatic spread to the adrenal glands and spine can be detected in coronal orientation during dedicated MRI of the lungs. Search focused whole body MRI completes the staging. Various additional MR imaging techniques provide further functional and clinically relevant information during a single examination. In the oncological context the most important techniques are imaging of perfusion and tumor motion. Functional MRI of the lungs complements the pure staging and improves surgical approaches and radiotherapy planning.

A hybrid breath hold and continued respiration-triggered technique for time-resolved 3D MRI perfusion studies in lung cancer

PURPOSE

Assessment of lung cancer perfusion is impaired by respiratory motion. Imaging times for contrast agent wash-out studies often exceed breath hold capabilities, and respiration triggering reduces temporal resolution. Temporally resolved volume acquisition of entire tumors is required to assess heterogeneity. Therefore, we developed and evaluated an MR measurement technique that exceeds a single breath hold, and provides a variable temporal resolution during acquisition while suspending breath-dependent motion.

MATERIALS AND METHODS

20 patients with suspected lung cancer were subjected to perfusion studies using a spoiled 3D gradient echo sequence after bolus injection of 0.07 mmol/kg body weight of Gd-DTPA. 10 acquisitions in expiratory breath hold were followed by 50 navigator-triggered acquisitions under free breathing. Post-processing allowed for co-registration of the 3D data sets. An ROI-based visualization of the signal-time curves was performed.

RESULTS

In all cases motion-suspended, time-resolved volume data sets (40 x 33 x 10 cm(3), voxel size: 2.1 x 2.1 x 5.0 mm(3)) were generated with a variable, initially high temporal resolution (2.25 sec) that was synchronized with the breath pattern and covered up to 8 1/2 min. In 7 / 20 cases a remaining offset could be reduced by rigid co-registration. The tumors showed fast wash-in, followed by rapid signal decay (8 / 20) or a plateau.

CONCLUSION

The feasibility of a perfusion study with hybrid breath hold and navigator-triggered time-resolved 3D MRI which combines high initial temporal resolution during breath hold with a long wash-out period under free breathing was demonstrated.

Lung hyperinflation: foe or friend?

Breath-hold divers employ glossopharyngeal insufflation (GI) in order to prevent the lungs from compressing at great depth and to increase intrapulmonary oxygen stores, thus increasing breath-hold time. The presented case study shows the physiological data and dynamic magnetic resonance imaging (dMRI) findings of acute hyperinflation, deliberately induced by GI, in a breath-hold diver and discusses the current state of knowledge regarding the associated hazards of this unique competitive sport. Static and dynamic lung volumes and expiratory flows were within the normal range, with vital capacity and peak expiratory flow being higher than the predicted values. Airway resistance and diffusing capacity of the lung for carbon monoxide were normal. Static compliance was normal and increased five-fold with hyperinflation. dMRI revealed a preserved shape of the thorax and diaphragm with hyperinflation. A herniation of the lung beneath the sternum and enlargement of the costodiaphragmatic angle were additional findings during the GI manoeuvre. After expiration, complete resolution to baseline was demonstrated. Hyperinflation can be physiological and even protective under abnormal physical conditions in the sense of acute adaptation to deep breath-hold diving. Dynamic magnetic resonance imaging is adequate for visualisation of the sequence of the glossopharyngeal insufflation manoeuvre and the complete reversibility of deliberate hyperinflation.

MR imaging of the chest: A practical approach at 1.5T

Magnetic resonance imaging (MRI) is capable of imaging infiltrative lung diseases as well as solid lung pathologies with high sensitivity. The broad use of lung MRI was limited by the long study time as well as its sensitivity to motion and susceptibility artifacts. These disadvantages were overcome by the utilisation of new techniques such as parallel imaging. This article aims to propose a standard MR imaging protocol at 1.5T and presents a spectrum of indications. The standard protocol comprises non-contrast-enhanced sequences. Following a GRE localizer (2D-FLASH), a coronal T2w single-shot half-Fourier TSE (HASTE) sequence with a high sensitivity for infiltrates and a transversal T1w 3D-GRE (VIBE) sequence with a high sensitivity for small lesions are acquired in a single breath hold. Afterwards, a coronal steady-state free precession sequence (TrueFISP) in free breathing is obtained. This sequence has a high sensitivity for central pulmonary embolism. Distinct cardiac dysfunctions as well as an impairment of the breathing mechanism are visible. The last step of the basic protocol is a transversal T2w-STIR (T2-TIRM) in a multi-breath holds technique to visualize enlarged lymph nodes as well as skeletal lesions. The in-room time is approximately 15min. The extended protocol comprises contrast-enhanced sequences (3D-GRE sequence (VIBE) after contrast media; about five additional minutes). Indications are tumorous lesions, unclear (malignant) pleural effusions and inflammatory diseases (vaskulitis). A perfusion analysis can be achieved using a 3D-GRE in shared echo-technique (TREAT) with a high temporal resolution. This protocol can be completed using a MR-angiography (3D-FLASH) with high spatial resolution. The in-room time for the complete protocol is approximately 30min.

Magnetic resonance-compatible-spirometry: principle, technical evaluation and application

The aim of this study was to assess the feasibility and accuracy of a novel magnetic resonance-compatible (MRc)-spirometer. The influence of body posture, magnetic resonance (MR)-setting and image acquisition on lung function was evaluated. Dynamic MR imaging (dMRI) was compared with simultaneously measured lung function. The development of the MRc-spirometer was based on a commercial spirometer and evaluated by flow-generator measurements and forced expiratory manoeuvres in 34 healthy nonsmokers (17 females and 17 males, mean age 32.9 yrs). Mean differences between forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC) were calculated and a sample paired t-test and Bland-Altman plots were generated. A total of 11 subjects underwent different subsequent MRc-spirometric measurements to assess the influence of the components of the MR system on lung function. The mean (95% confidence interval) difference of FEV(1) and FVC between the two systems was 0.004 (-0.04-0.04) L and 0.018 (-0.05-0.09) L, respectively. In the subgroup analysis, an influence of the MR-system on FEV(1) was found. FEV(1) correlated well with the dMRI measurement of the apico-diaphragmatic distance-change after the first second of forced expiration (r = 0.72). In conclusion, magnetic resonance-compatible-spirometry is feasible, reliable and safe. The magnetic resonance-setting only has a small influence on simultaneously measured forced expiratory volume in one second. Dynamic magnetic resonance imaging measurements correlate well with simultaneously acquired lung function parameters.

[MRI in mucoviscidosis (cystic fibrosis)]

Cystic fibrosis (CF) is a multi-systemic disease with major impact on the lungs. Pulmonary manifestation is crucial for the prognosis and life expectancy of patients. Imaging modalities and lung function tests reflect the pulmonary status in these patients. The standard imaging modality for diagnosis and follow-up of pulmonary changes is chest x-ray. The gold standard for the detection of parenchymal lung changes remains high resolution computed tomography (HRCT), but this is not used routinely for CF-patients due to radiation exposure. Magnetic resonance imaging (MRI) used to be of no importance in monitoring cystic fibrosis lung disease, as shown in studies from the 1980s and early 1990 s. The continuing improvement of MRI techniques, however, has allowed for an adequate application of this non-radiation method in diagnosing the major pulmonary findings in CF, in addition to the assessment of lung function.