Computed tomography and magnetic resonance imaging in cystic fibrosis lung disease

Lung Magnetic Resonance Imaging: Technical Advancements and Clinical Applications

ABSTRACT

Since lung magnetic resonance imaging (MRI) became clinically available, limited clinical utility has been suggested for applying MRI to lung diseases. Moreover, clinical applications of MRI for patients with lung diseases or thoracic oncology may vary from country to country due to clinical indications, type of health insurance, or number of MR units available. Because of this situation, members of the Fleischner Society and of the Japanese Society for Magnetic Resonance in Medicine have published new reports to provide appropriate clinical indications for lung MRI. This review article presents a brief history of lung MRI in terms of its technical aspects and major clinical indications, such as (1) what is currently available, (2) what is promising but requires further validation or evaluation, and (3) which developments warrant research-based evaluations in preclinical or patient studies. We hope this article will provide Investigative Radiology readers with further knowledge of the current status of lung MRI and will assist them with the application of appropriate protocols in routine clinical practice.

[Magnetic resonance imaging of the lung : State of the art]

Due to the low proton density of the lung parenchyma and the rapid signal decay at the air-tissue interfaces, for a long time the lungs were difficult to access using magnetic resonance imaging (MRI); however, technical advances could address most of these obstacles. Pulmonary alterations associated with tissue proliferation ("plus pathologies"), can now be detected with high diagnostic accuracy because of the locally increased proton density. Compared to computed tomography (CT), MRI provides a comprehensive range of functional imaging procedures (respiratory mechanics, perfusion and ventilation). In addition, as a radiation-free noninvasive examination modality, it enables repeated examinations for assessment of the course or monitoring of the effects of treatment, even in children. This article discusses the technical aspects, gives suggestions for protocols and explains the role of MRI of the lungs in the routine assessment of various diseases.

MRI and Pulmonary Function Tests' Results as Ventilation Inhomogeneity Markers in Children and Adolescents with Cystic Fibrosis

Magnetic resonance imaging (MRI) of the chest is becoming more available in the detection and monitoring of early changes in lung function and structure in patients with cystic fibrosis (CF). The aim of this study was to assess the relationship between pulmonary function tests (PFT) and perfusion deficits in CF children measured by MRI. We performed a retrospective analysis of the perfusion lung MRI scans and the results of spirometry, oscillometry, body plethysmography, single-breath carbon monoxide uptake, and multiple-breath washout technique (MBW). There were statistically significant correlations between the MRI perfusion scores and MBW parameters (2.5% LCI, M1/M0, M2/M0), spirometry parameters (FEV1, FVC, FEF25/75), reactance indices in impulse oscillometry (X5Hz, X10Hz), total lung capacity (TLC) measured in single breath carbon monoxide uptake, markers of air-trapping in body plethysmography (RV, RV/TLC), and the diffusing capacity of the lungs for carbon monoxide. We also observed significant differences in the aforementioned PFT variables between the patient groups divided based on perfusion scores. We noted a correlation between markers of functional lung deficits measured by the MRI and PFTs in CF children. MRI perfusion abnormalities were reflected sooner in the course of the disease than PFT abnormalities.

A Dual-Channel Deep Learning Approach for Lung Cavity Estimation From Hyperpolarized Gas and Proton MRI

BACKGROUND

Hyperpolarized gas MRI can quantify regional lung ventilation via biomarkers, including the ventilation defect percentage (VDP). VDP is computed from segmentations derived from spatially co-registered functional hyperpolarized gas and structural proton (1 H)-MRI. Although acquired at similar lung inflation levels, they are frequently misaligned, requiring a lung cavity estimation (LCE). Recently, single-channel, mono-modal deep learning (DL)-based methods have shown promise for pulmonary image segmentation problems. Multichannel, multimodal approaches may outperform single-channel alternatives.

PURPOSE

We hypothesized that a DL-based dual-channel approach, leveraging both 1 H-MRI and Xenon-129-MRI (129 Xe-MRI), can generate LCEs more accurately than single-channel alternatives.

STUDY TYPE

Retrospective.

POPULATION

A total of 480 corresponding 1 H-MRI and 129 Xe-MRI scans from 26 healthy participants (median age [range]: 11 [8-71]; 50% females) and 289 patients with pulmonary pathologies (median age [range]: 47 [6-83]; 51% females) were split into training (422 scans [88%]; 257 participants [82%]) and testing (58 scans [12%]; 58 participants [18%]) sets.

FIELD STRENGTH/SEQUENCE

1.5-T, three-dimensional (3D) spoiled gradient-recalled 1 H-MRI and 3D steady-state free-precession 129 Xe-MRI.

ASSESSMENT

We developed a multimodal DL approach, integrating 129 Xe-MRI and 1 H-MRI, in a dual-channel convolutional neural network. We compared this approach to single-channel alternatives using manually edited LCEs as a benchmark. We further assessed a fully automatic DL-based framework to calculate VDPs and compared it to manually generated VDPs.

STATISTICAL TESTS

Friedman tests with post hoc Bonferroni correction for multiple comparisons compared single-channel and dual-channel DL approaches using Dice similarity coefficient (DSC), average boundary Hausdorff distance (average HD), and relative error (XOR) metrics. Bland-Altman analysis and paired t-tests compared manual and DL-generated VDPs. A P value < 0.05 was considered statistically significant.

RESULTS

The dual-channel approach significantly outperformed single-channel approaches, achieving a median (range) DSC, average HD, and XOR of 0.967 (0.867-0.978), 1.68 mm (37.0-0.778), and 0.066 (0.246-0.045), respectively. DL-generated VDPs were statistically indistinguishable from manually generated VDPs (P = 0.710).

DATA CONCLUSION

Our dual-channel approach generated LCEs, which could be integrated with ventilated lung segmentations to produce biomarkers such as the VDP without manual intervention.

EVIDENCE LEVEL

4.

TECHNICAL EFFICACY

Stage 1.

TRACK-CF prospective cohort study: Understanding early cystic fibrosis lung disease

Background

Lung disease as major cause for morbidity in patients with cystic fibrosis (CF) starts early in life. Its large phenotypic heterogeneity is partially explained by the genotype but other contributing factors are not well delineated. The close relationship between mucus, inflammation and infection, drives morpho-functional alterations already early in pediatric CF disease, The TRACK-CF cohort has been established to gain insight to disease onset and progression, assessed by lung function testing and imaging to capture morpho-functional changes and to associate these with risk and protective factors, which contribute to the variation of the CF lung disease progression.

Methods and design

TRACK-CF is a prospective, longitudinal, observational cohort study following patients with CF from newborn screening or clinical diagnosis throughout childhood. The study protocol includes monthly telephone interviews, quarterly visits with microbiological sampling and multiple-breath washout and as well as a yearly chest magnetic resonance imaging. A parallel biobank has been set up to enable the translation from the deeply phenotyped cohort to the validation of relevant biomarkers. The main goal is to determine influencing factors by the combined analysis of clinical information and biomaterials. Primary endpoints are the lung clearance index by multiple breath washout and semi-quantitative magnetic resonance imaging scores. The frequency of pulmonary exacerbations, infection with pro-inflammatory pathogens and anthropometric data are defined as secondary endpoints.

Discussion

This extensive cohort includes children after diagnosis with comprehensive monitoring throughout childhood. The unique composition and the use of validated, sensitive methods with the attached biobank bears the potential to decisively advance the understanding of early CF lung disease.

Ethics and trial registration

The study protocol was approved by the Ethics Committees of the University of Heidelberg (approval S-211/2011) and each participating site and is registered at clinicaltrials.gov (NCT02270476).

EVALUATING THE EFFICACY OF HUMAN BRONCHIECTASISBASED ANTIBIOTIC THERAPY IN THE TREATMENT OF ORANGUTAN RESPIRATORY DISEASE SYNDROME

Unique among apes, orangutans (Pongo spp.) develop a chronic respiratory disease called orangutan respiratory disease syndrome (ORDS). The authors define ORDS as intermittent bacterial infection and chronic inflammation of any region or combination of regions of the respiratory tract, including the sinuses, air sacs, cranial bones, airways, and lung parenchyma. Infection in any of these areas can present acutely but then becomes recurrent, chronic, progressive, and ultimately fatal. The closest model to this disease is cystic fibrosis (CF) in people. We hypothesized that use of a 4-8-wk course of combined oral antibiotics used in the treatment of bronchiectasis in CF patients would lead to prolonged symptomatic and computed tomography (CT) scan improvement in orangutans experiencing early signs of ORDS. Nine adult Bornean orangutans (Pongo pygmaeus, eight males, one female, 18-29 yr of age) diagnosed with early ORDS-like respiratory disease underwent CT scan before initiation of treatment. Each animal received a combined course of azithromycin (400 mg 3/wk, mean 7 mg/kg) and levofloxacin (500 mg PO q24h, mean 8.75 mg/kg) for a period of 4-8 wk. CT scan was repeated 6-14 mon after completion of antibiotic treatment. Pretreatment CT showed that six of nine animals had lower respiratory pathology (airway disease, pneumonia, or both). All six orangutans had concurrent sinusitis, mastoiditis, airsacculitis, or a combination of these conditions. Upper respiratory disease alone was observed in three animals. CT showed improvement or resolution in four of five sinusitis cases, improvement in one of two instances of mastoiditis, resolution in five of six instances of airsacculitis, improvement or resolution in six of six instance of lower airway disease (P = 0.03, 95% CI 0.54-1.0], and resolution in five of five cases of pneumonia. Resolution of pretreatment clinical signs was observed in all nine animals. Two developed signs not present at pretreatment. These results show that combination antibiotic therapy with azithromycin and levofloxacin provides improvement in clinical signs and CT evidence of ORDS-related pathology, resulting in symptom-free status in some animals for up to 33 mon.

Best Practices: Imaging Strategies for Reduced-Dose Chest CT in the Management of Cystic Fibrosis-Related Lung Disease

OBJECTIVE. Cystic fibrosis (CF) is a multisystemic life-limiting disorder. The leading cause of morbidity in CF is chronic pulmonary disease. Chest CT is the reference standard for detection of bronchiectasis. Cumulative ionizing radiation limits the use of CT, particularly as treatments improve and life expectancy increases. The purpose of this article is to summarize the evidence on low-dose chest CT and its effect on image quality to determine best practices for imaging in CF. CONCLUSION. Low-dose chest CT is technically feasible, reduces dose, and renders satisfactory image quality. There are few comparison studies of low-dose chest CT and standard chest CT in CF; however, evidence suggests equivalent diagnostic capability. Low-dose chest CT with iterative reconstructive algorithms appears superior to chest radiography and equivalent to standard CT and has potential for early detection of bronchiectasis and infective exacerbations, because clinically significant abnormalities can develop in patients who do not have symptoms. Infection and inflammation remain the primary causes of morbidity requiring early intervention. Research gaps include the benefits of replacing chest radiography with low-dose chest CT in terms of improved diagnostic yield, clinical decision making, and patient outcomes. Longitudinal clinical studies comparing CT with MRI for the monitoring of CF lung disease may better establish the complementary strengths of these imaging modalities.

Time to get serious about the detection and monitoring of early lung disease in cystic fibrosis

Structural and functional defects within the lungs of children with cystic fibrosis (CF) are detectable soon after birth and progress throughout preschool years often without overt clinical signs or symptoms. By school age, most children have structural changes such as bronchiectasis or gas trapping/hypoperfusion and lung function abnormalities that persist into later life. Despite improved survival, gains in forced expiratory volume in one second (FEV₁) achieved across successive birth cohorts during childhood have plateaued, and rates of FEV₁ decline in adolescence and adulthood have not slowed. This suggests that interventions aimed at preventing lung disease should be targeted to mild disease and commence in early life. Spirometry-based classifications of 'normal' (FEV₁≥90% predicted) and 'mild lung disease' (FEV₁ 70%-89% predicted) are inappropriate, given the failure of spirometry to detect significant structural or functional abnormalities shown by more sensitive imaging and lung function techniques. The state and readiness of two imaging (CT and MRI) and two functional (multiple breath washout and oscillometry) tools for the detection and monitoring of early lung disease in children and adults with CF are discussed in this article.Prospective research programmes and technological advances in these techniques mean that well-designed interventional trials in early lung disease, particularly in young children and infants, are possible. Age appropriate, randomised controlled trials are critical to determine the safety, efficacy and best use of new therapies in young children. Regulatory bodies continue to approve medications in young children based on safety data alone and extrapolation of efficacy results from older age groups. Harnessing the complementary information from structural and functional tools, with measures of inflammation and infection, will significantly advance our understanding of early CF lung disease pathophysiology and responses to therapy. Defining clinical utility for these novel techniques will require effective collaboration across multiple disciplines to address important remaining research questions. Future impact on existing management burden for patients with CF and their family must be considered, assessed and minimised.To address the possible role of these techniques in early lung disease, a meeting of international leaders and experts in the field was convened in August 2019 at the Australiasian Cystic Fibrosis Conference. The meeting entitiled 'Shaping imaging and functional testing for early disease detection of lung disease in Cystic Fibrosis', was attended by representatives across the range of disciplines involved in modern CF care. This document summarises the proceedings, key priorities and important research questions highlighted.

Computed tomography in cystic fibrosis lung disease: a focus on radiation exposure

Thoracic computed tomography (CT) is the imaging reference method in the diagnosis, assessment and management of lung disease. In the setting of cystic fibrosis (CF), CT demonstrates increased sensitivity compared with pulmonary function tests and chest radiography, and findings correlate with clinical outcomes. Better understanding of the aetiology of CF lung disease indicates that even asymptomatic infants with CF can have irreversible pulmonary pathology. Surveillance and early diagnosis of lung disease in CF are important to preserve lung parenchyma and to optimise long-term outcomes. CF is associated with increased cumulative radiation exposure due to the requirement for repeated imaging from a young age. Radiation dose optimisation, important for the safe use of CT in children with CF, is best achieved in a team environment where paediatric radiologists work closely with paediatric respiratory physicians, physicists and radiography technicians to achieve the best patient outcomes. Despite the radiation doses incurred, CT remains a vital imaging tool in children with CF. Radiologists with special interests in CT dose optimisation and respiratory disease are key to the appropriate use of CT in paediatric imaging. Paediatric radiologists strive to minimise radiation dose to children whilst providing the best possible assessment of lung disease.

Ultra-low-dose chest CT in adult patients with cystic fibrosis using a third-generation dual-source CT scanner

INTRODUCTION

Chest computed tomography (CT) examinations are performed routinely in some cystic fibrosis (CF) centers in order to evaluate lung disease progression in CF patients. Continuous CT technological advancement in theory could allows a lower radiation exposure of CF patients during chest CT examinations without an image quality reduction, and this could become increasingly important over time in order to reduce the cumulative radiation dose effects given the continuous increase of CF patients predicted median survival.

OBJECTIVE

The aim of this study was to compare objective and subjective image quality and radiation dose between low-dose chest CT examinations performed in adult CF patients using a third-generation DSCT scanner and a 64-slices single-source CT (SSCT) scanner.

MATERIALS AND METHODS

Between January 2016 and August 2019, 81 CF patients underwent low-dose chest CT examinations using both a 64-slices SSCT scanner (2016-2017) and a third-generation DSCT scanner (2018-2019). Objective image noise standard deviation (INSD), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), overall subjective image quality (OSIQ), subjective image noise (SIN), subjective evaluation of streaking artifacts (SA), movement artifacts (MA) and edge resolution (ER), dose-length product (DLP), volume computed tomography dose index (CTDIvol) and effective radiation dose (ERD) were compared between DSCT and SSCT examinations. DSCT examinations consisted in spiral inspiratory end expiratory acquisitions. SSCT examinations consisted in spiral inspiratory acquisitions and five axial expiratory ones.

RESULTS

DSCT protocol showed statistically significant lower spiral inspiratory phase mean DLP, CTDIvol and ERD than SSCT protocol, with a 25% DLP, CTDIvol and ERD reduction. DSCT protocol showed statistically significant higher overall (inspiratory and expiratory phases) mean DLP, CTDIvol and ERD than SSCT protocol, with a 40% DLP, CTDIvol and ERD increase. Objective image quality (INSD, SNR and CNR) and SIN differences were not statistically significant, but subjective evaluation of DSCT images showed statistically significant better OSIQ and ER, as well as statistically significant lower SA and MA with respect to SSCT images.

CONCLUSIONS

To our knowledge, this is the first study evaluating chest CT image quality and radiation dose in adult CF patients using a third-generation DSCT scanner, and it showed that technological advancements could be used in order to reduce radiation exposure of volumetric examinations. The spiral inspiratory dose reduction can be obtained with concomitant improvements in subjective image quality with comparable objective quality. This will probably allow a wider use of this imaging modality in order to assess bronchiectasis and will probably foster spiral expiratory acquisition for small airways disease evaluation.

[Cystic fibrosis and computed tomography of the lungs]

With its high detail of morphological changes in lung parenchyma and airways as well as the possibilities for three-dimensional reconstruction, computed tomography (CT) represents a solid tool for the diagnosis and follow-up in patients suffering from cystic fibrosis (CF). Guidelines for standardized CT image acquisition in CF patients are still missing. In the mostly younger CF patients, an important issue is the well-considered use of radiation in CT imaging. The use of intravenous contrast agent is mainly restricted to acute emergency diagnostics. Typical morphological findings in CF lung disease are bronchiectasis, mucus plugging, or signs of decreased ventilation (air trapping) which can be detected with CT even in early stages. Various scoring systems that have become established over time are used to grade disease severity and for structured follow-up, e.g., in clinical research studies. With the technical development of CT, a number of postprocessing software tools were developed to help clinical reporting and overcome interreader differences for a standardized quantification. As an imaging modality free of ionizing radiation, magnetic resonance imaging (MRI) is becoming increasingly important in the diagnosis and follow-up of CF patients and is already frequently a substitute for CT for long-term follow-up at numerous specialized centers.

Comparison of single breath hyperpolarized 129 Xe MRI with dynamic 19 F MRI in cystic fibrosis lung disease

Purpose

To quantitatively compare dynamic ¹⁹F and single breath hyperpolarized ¹²⁹Xe MRI for the detection of ventilation abnormalities in subjects with mild cystic fibrosis (CF) lung disease.

Methods

Ten participants with stable CF and a baseline FEV1 > 70% completed a single imaging session where dynamic ¹⁹F and single breath ¹²⁹Xe lung ventilation images were acquired on a 3T MRI scanner. Ventilation defect percentages (VDP) values between ¹⁹F early‐breath, ¹⁹F maximum‐ventilation, ¹²⁹Xe low‐resolution, and ¹²⁹Xe high‐resolution images were compared. Dynamic ¹⁹F images were used to determine gas wash‐in/out rates in regions of ventilation congruency and mismatch between ¹²⁹Xe and ¹⁹F.

Results

VDP values from high‐resolution ¹²⁹Xe images were greater than from low‐resolution images (P = .001), although these values were significantly correlated (r = 0.68, P = .03). Early‐breath ¹⁹F VDP and max‐vent ¹⁹F VDP also showed significant correlation (r = 0.75, P = .012), with early‐breath ¹⁹F VDP values being significantly greater (P < .001). No correlation in VDP values were detected between either ¹⁹F method or high‐res ¹²⁹Xe images. In addition, the location and volume of ventilation defects were often different when comparing ¹²⁹Xe and ¹⁹F images from the same subject. Areas of ventilation congruence displayed the expected ventilation kinetics, while areas of ventilation mismatch displayed abnormally slow gas wash‐in and wash‐out.

Conclusion

In CF subjects, ventilation abnormalities are identified by both ¹⁹F and HP ¹²⁹Xe imaging. However, these ventilation abnormalities are not entirely congruent. ¹⁹F and HP ¹²⁹Xe imaging provide complementary information that enable differentiation of normally ventilated, slowly ventilated, and non‐ventilated regions in the lungs.

Imaging the Injured Lung: Mechanisms of Action and Clinical Use

Acute respiratory distress syndrome (ARDS) consists of acute hypoxemic respiratory failure characterized by massive and heterogeneously distributed loss of lung aeration caused by diffuse inflammation and edema present in interstitial and alveolar spaces. It is defined by consensus criteria, which include diffuse infiltrates on chest imaging-either plain radiography or computed tomography. This review will summarize how imaging sciences can inform modern respiratory management of ARDS and continue to increase the understanding of the acutely injured lung. This review also describes newer imaging methodologies that are likely to inform future clinical decision-making and potentially improve outcome. For each imaging modality, this review systematically describes the underlying principles, technology involved, measurements obtained, insights gained by the technique, emerging approaches, limitations, and future developments. Finally, integrated approaches are considered whereby multimodal imaging may impact management of ARDS.

Quantitative multivolume proton-magnetic resonance imaging in patients with cystic fibrosis lung disease: comparison with clinical indicators

This cross-sectional study aims to verify the relationship between quantitative multivolume proton-magnetic resonance imaging (¹H-MRI) and clinical indicators of ventilatory abnormalities in cystic fibrosis (CF) lung disease.Non-enhanced chest MRI, spirometry and multiple breath washout was performed by 28 patients (10-27 years) with CF lung disease. Images acquired at end-inspiration and end-expiration were registered by optical flow to estimate expiratory-inspiratory proton-density change (Δ¹H-MRI) as a measure of regional ventilation. Magnetic resonance images were also evaluated using a CF-specific scoring system.Biomarkers of CF ventilation impairment were defined from the Δ¹H-MRI as follows: Δ¹H-MRI median, Δ¹H-MRI quartile coefficient of variation (QCV) and percentage of low-ventilation volume (%LVV). Imaging biomarkers correlated to all the clinical measures of ventilation abnormality, with the strongest correlation between Δ¹H-MRI median and forced expiratory volume in 1 s (r²=0.44, p<0.001), Δ¹H-MRI QCV and lung clearance index (LCI) (r²=0.51, p<0.001) and %LVV and LCI (r²=0.66, p<0.001). Correlations were also found between imaging biomarkers of ventilation and morphological scoring.The study showed a significant correlation between quantitative multivolume MRI and clinical indicators of CF lung disease. MRI, as a non-ionising imaging technique, may be particularly attractive in CF care for longitudinal evaluation, providing a new imaging biomarker to detect early ventilatory abnormalities.

Organization of Patient Management and Fungal Epidemiology in Cystic Fibrosis

The achievement of a better life for cystic fibrosis (CF) patients is mainly caused by a better management and infection control over the last three decades. Herein, we want to summarize the cornerstones for an effective management of CF patients and to give an overview of the knowledge about the fungal epidemiology in this clinical context in Europe. Data from a retrospective analysis encompassing 66,616 samples from 3235 CF patients followed-up in 9 CF centers from different European countries are shown.

Comparison of Lung Clearance Index and Magnetic Resonance Imaging for Assessment of Lung Disease in Children with Cystic Fibrosis

RATIONALE

Early onset and progression of lung disease in children with cystic fibrosis (CF) indicates that sensitive noninvasive outcome measures are needed for diagnostic monitoring and early intervention clinical trials. The lung clearance index (LCI) and chest magnetic resonance imaging (MRI) were shown to detect early lung disease in CF; however, the relationship between the two measures remains unknown.

OBJECTIVES

To correlate the LCI with abnormalities detected by MRI and compare the sensitivity of the two techniques to detect responses to therapy for pulmonary exacerbations in children with CF.

METHODS

LCI determined by age-adapted multiple breath washout techniques and MRI studies were performed in 97 clinically stable children with CF across the pediatric age range (0.2-21.1 yr). Furthermore, LCI (n = 26) or MRI (n = 10) were performed at the time of pulmonary exacerbation and after antibiotic therapy. MRI was evaluated using a dedicated morphofunctional score.

MEASUREMENTS AND MAIN RESULTS

The LCI correlated with the global MRI score as well as MRI-defined airway wall abnormalities, mucus plugging, and abnormal lung perfusion in infants and toddlers (P < 0.05 to P < 0.001) and in older children (P < 0.001) with CF. LCI and MRI were sensitive to detect response to antibiotic therapy for pulmonary exacerbations.

CONCLUSIONS

Our results indicate that LCI and MRI may be useful complementary tools for noninvasive monitoring and as quantitative endpoints in early intervention trials in children with CF. In this context, MRI enables detection of disease heterogeneity, including regional mucus plugging associated with abnormal lung perfusion in early CF lung disease. Clinical trial registered with www.clinicaltrials.gov (NCT 02270476).

Detection and monitoring of lung inflammation in cystic fibrosis during respiratory tract exacerbation using diffusion-weighted magnetic resonance imaging

The aim was to investigate whether diffusion-weighted magnetic resonance imaging (DWI) detects and monitors inflammatory and lung function changes during respiratory tract exacerbations (RTE) treatment in patients with cystic fibrosis (CF).29 patients with RTE underwent DWI pre- and post-antibiotic treatment. A control group of 27 stable patients, matched for age and sex, underwent DWI with the same time gap as those undergoing RTE treatment. Clinical status and lung function were assessed at each DWI time point. The CF-MRI scoring system was used to assess structural lung changes in both CF groups.Significant reduction in the DWI score over the course of antibiotic treatment (p<0.0001) was observed in patients with RTE, but not in the control group. DWI score had a strong inverse correlation with clinical status (r=-0.504, p<0.0001) and lung function (r=-0.635, p<0.0001) in patients with RTE. Interestingly, there were persistent significant differences in the CF-MRI score between the RTE and control group at both baseline and follow-up (p<0.001), while the differences in DWI score were only observed at baseline (p<0.001).DWI is a promising imaging method for noninvasive detection of pulmonary inflammation during RTE, and may be used to monitor treatment efficacy of anti-inflammatory treatment.

MRI of cystic fibrosis lung manifestations: sequence evaluation and clinical outcome analysis

AIM

To evaluate different magnetic resonance imaging (MRI) sequences for diagnosis of pulmonary manifestations of cystic fibrosis (CF) in comparison to chest computed tomography (CT), including an extended outcome analysis.

MATERIALS AND METHODS

Twenty-eight patients with CF (15 male, 13 female, mean age 30.5±9.4 years) underwent CT and MRI of the lung. MRI (1.5 T) included different T2- and T1-weighted sequences: breath-hold HASTE (half Fourier acquisition single shot turbo spin echo) and VIBE (volumetric interpolated breath-hold examination, before and after contrast medium administration) sequences and respiratory-triggered PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) sequences with and without fat signal suppression, and perfusion imaging. CT and MRI images were evaluated by the modified Helbich and the Eichinger scoring systems. The clinical follow-up analysis assessed pulmonary exacerbations within 24 months.

RESULTS

The highest concordance to CT was achieved for the PROPELLER sequences without fat signal suppression (concordance correlation coefficient CCC of the overall modified Helbich score 0.93 and of the overall Eichinger score 0.93). The other sequences had the following concordance: PROPELLER with fat signal suppression (CCCs 0.91 and 0.92), HASTE (CCCs 0.87 and 0.89), VIBE (CCCs 0.84 and 0.85) sequences. In the outcome analysis, the combined MRI analysis of all five sequences and a specific MRI protocol (PROPELLER without fast signal suppression, VIBE sequences, perfusion imaging) reached similar correlations to the number of pulmonary exacerbations as the CT examinations.

CONCLUSION

An optimum lung MRI protocol in patients with CF consists of PROPELLER sequences without fat signal suppression, VIBE sequences, and lung perfusion analysis to enable high diagnostic efficacy and outcome prediction.

Lung function imaging methods in Cystic Fibrosis pulmonary disease

Monitoring of pulmonary physiology is fundamental to the clinical management of patients with Cystic Fibrosis. The current standard clinical practise uses spirometry to assess lung function which delivers a clinically relevant functional readout of total lung function, however does not supply any visible or localised information. High Resolution Computed Tomography (HRCT) is a well-established current 'gold standard' method for monitoring lung anatomical changes in Cystic Fibrosis patients. HRCT provides excellent morphological information, however, the X-ray radiation dose can become significant if multiple scans are required to monitor chronic diseases such as cystic fibrosis. X-ray phase-contrast imaging is another emerging X-ray based methodology for Cystic Fibrosis lung assessment which provides dynamic morphological and functional information, albeit with even higher X-ray doses than HRCT. Magnetic Resonance Imaging (MRI) is a non-ionising radiation imaging method that is garnering growing interest among researchers and clinicians working with Cystic Fibrosis patients. Recent advances in MRI have opened up the possibilities to observe lung function in real time to potentially allow sensitive and accurate assessment of disease progression. The use of hyperpolarized gas or non-contrast enhanced MRI can be tailored to clinical needs. While MRI offers significant promise it still suffers from poor spatial resolution and the development of an objective scoring system especially for ventilation assessment.

[MRI of the pulmonary parenchyma: Towards clinical applicability?]

Lung parenchyma has long been considered out of the scope of magnetic resonance imaging (MRI) clinical applicability. However, technological advances have emerged to soluce the technical difficulties and thus, applications in clinical practice have become realistic. Nevertheless, various approaches have been proposed and there is a need to synthetize the most recent literature data in order to envision a rationale to build lung MR protocols for clinical use. In addition, these technological innovations may modify the usual paradigms of lung MRI, which are still not consensual. Thus, lung MR protocols appear to be heterogeneous across expert centers in the current context. In this literature review, we ought to describe a rationale on the need to get an alternative to ionizing imaging modalities, in particular in the follow-up of patients with chronic lung diseases. We will describe the most recent technical advances regarding both morphological and functional MRI. Finally, we will conclude on the clinical applicability of MRI of the pulmonary parenchyma, as a routine or research tool.

Spirometer guided chest imaging in children: It is worth the effort!

PURPOSE

Computed tomography (CT) and magnetic resonance imaging (MRI) scans are used to assess and monitor several pediatric lung diseases. It is well recognized that lung volume at the moment of acquisition has a major impact on the appearance of lung parenchyma and airways. Importantly, the sensitivity of chest CT and MRI to detect bronchiectasis and gas trapping is highly dependent on adequate volume control during the image acquisition. This paper describes a feasible method to obtain accurate control of lung volume during chest imaging in pediatric patients with lung disease.

PROCEDURE

A procedure to obtain maximal respiratory manoeuvres with spirometry guidance during image acquisition for CT and MRI is described. This procedure requires training of the subject, an MRI compatible spirometer and close collaboration between a lung function scientist and the radiographer. A good to excellent target volume level for the inspiratory or expiratory scan can be achieved in around 90% of children. An important condition for this success rate is the training of the subject, executed prior to each chest CT or MRI, and instructions by the lung function scientist during the chest CT.

CONCLUSION

Implementing lung volume guidance with a spirometer is an important and feasible step to standardize chest imaging and to optimize the diagnostic yield of chest CT and MRI in children with lung disease. Training and the collaborative effort by a lung function scientist and radiographer is the key factor for success of this procedure. Pediatr Pulmonol. 2017;52:48-56. © 2016 Wiley Periodicals, Inc.

Global and regional lung function in cystic fibrosis measured by electrical impedance tomography

BACKGROUND

Electrical impedance tomography (EIT) delivers information about global and regional ventilation. Linearity of EIT during tidal breathing is known. We investigated the feasibility of EIT during lung function tests in pediatric patients with cystic fibrosis (CF) and healthy controls.

METHODS

Eleven CF patients and 11 age-matched controls underwent spirometry and simultaneous EIT. Global EIT results were scaled to spirometric forced vital capacity (FVC). Subsequently, global and regional "EIT-spirometry" was calculated and correlated with clinical findings, radiology, and lung function results before and after bronchospasmolysis (BSL).

RESULTS

Spirometry and global EIT results correlated essentially (r²  = 0.71-1.0, P < 0.001). While lung function results were comparable for both groups, EIT demonstrated inhomogeneous ventilation and individual changes after BSL.

CONCLUSIONS

EIT changes during forced expiration correlate with lung function parameters, clinical findings, and radiology. Regional analysis of EIT illustrates regional lung function and visualizes individual therapeutic effects. Pediatr Pulmonol. 2016;51:1191-1199. © 2016 Wiley Periodicals, Inc.

Quantitative computed tomography analysis of the airways in patients with cystic fibrosis using automated software: correlation with spirometry in the evaluation of severity

Objective

To perform a quantitative analysis of the airways using automated software, in computed tomography images of patients with cystic fibrosis, correlating the results with spirometric findings.

Materials and Methods

Thirty-four patients with cystic fibrosis were studied-20 males and 14 females; mean age 18 ± 9 years-divided into two groups according to the spirometry findings: group I (n = 21), without severe airflow obstruction (forced expiratory volume in first second [FEV1] > 50% predicted), and group II (n = 13), with severe obstruction (FEV1 ≤ 50% predicted). The following tracheobronchial tree parameters were obtained automatically: bronchial diameter, area, thickness, and wall attenuation.

Results

On average, 52 bronchi per patient were studied. The number of bronchi analyzed was higher in group II. The correlation with spirometry findings, especially between the relative wall thickness of third to eighth bronchial generation and predicted FEV1, was better in group I.

Conclusion

Quantitative analysis of the airways by computed tomography can be useful for assessing disease severity in cystic fibrosis patients. In patients with severe airflow obstruction, the number of bronchi studied by the method is higher, indicating more bronchiectasis. In patients without severe obstruction, the relative bronchial wall thickness showed a good correlation with the predicted FEV1.

VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE

The aims of this study were to assess the visibility of pulmonary structures in patients with cystic fibrosis (CF) in digital tomosynthesis (DTS) using computed tomography (CT) as reference and to investigate the dependency on anatomical location and observer experience. Anatomical structures in predefined regions of CT images from 21 patients were identified. Three observers with different levels of experience rated the visibility of the structures in DTS by performing a head-to-head comparison with visibility in CT. Visibility of the structures in DTS was reported as equal to CT in 34 %, inferior in 52 % and superior in 14 % of the ratings. Central and peripheral lateral structures received higher visibility ratings compared with peripheral structures anteriorly, posteriorly and surrounding the diaphragm (p ≤ 0.001). Reported visibility was significantly higher for the most experienced observer (p ≤ 0.01). The results indicate that minor pathology can be difficult to visualise with DTS depending on location and observer experience. Central and peripheral lateral structures are generally well depicted.

Computed tomography dose optimisation in cystic fibrosis: A review

Cystic fibrosis (CF) is the most common autosomal recessive disease of the Caucasian population worldwide, with respiratory disease remaining the most relevant source of morbidity and mortality. Computed tomography (CT) is frequently used for monitoring disease complications and progression. Over the last fifteen years there has been a six-fold increase in the use of CT, which has lead to a growing concern in relation to cumulative radiation exposure. The challenge to the medical profession is to identify dose reduction strategies that meet acceptable image quality, but fulfil the requirements of a diagnostic quality CT. Dose-optimisation, particularly in CT, is essential as it reduces the chances of patients receiving cumulative radiation doses in excess of 100 mSv, a dose deemed significant by the United Nations Scientific Committee on the Effects of Atomic Radiation. This review article explores the current trends in imaging in CF with particular emphasis on new developments in dose optimisation.

Diffusion weighted imaging in cystic fibrosis disease: beyond morphological imaging

OBJECTIVES

To explore the feasibility of diffusion-weighted imaging (DWI) to assess inflammatory lung changes in patients with Cystic Fibrosis (CF) METHODS: CF patients referred for their annual check-up had spirometry, chest-CT and MRI on the same day. MRI was performed in a 1.5 T scanner with BLADE and EPI-DWI sequences (b = 0-600 s/mm²). End-inspiratory and end-expiratory scans were acquired in multi-row scanners. DWI was scored with an established semi-quantitative scoring system. DWI score was correlated to CT sub-scores for bronchiectasis (CF-CT_BE), mucus (CF-CT_mucus), total score (CF-CT_total-score), FEV₁, and BMI. T-test was used to assess differences between patients with and without DWI-hotspots.

RESULTS

Thirty-three CF patients were enrolled (mean 21 years, range 6-51, 19 female). 4 % (SD 2.6, range 1.5-12.9) of total CF-CT alterations presented DWI-hotspots. DWI-hotspots coincided with mucus plugging (60 %), consolidation (30 %) and bronchiectasis (10 %). DWI_total-score correlated (all p < 0.0001) positively to CF-CT_BE (r = 0.757), CF-CT_mucus (r = 0.759) and CF-CT_total-score (r = 0.79); and negatively to FEV₁ (r = 0.688). FEV₁ was significantly higher (p < 0.0001) in patients without DWI-hotspots.

CONCLUSIONS

DWI-hotspots strongly correlated with radiological and clinical parameters of lung disease severity. Future validation studies are needed to establish the exact nature of DWI-hotspots in CF patients.

KEY POINTS

• DWI hotspots only partly overlapped structural abnormalities on morphological imaging • DWI strongly correlated with radiological and clinical indicators of CF-disease severity • Patients with more DWI hotspots had lower lung function values • Mucus score best predicted the presence of DWI-hotspots with restricted diffusion.

Assessment of CF lung disease using motion corrected PROPELLER MRI: a comparison with CT

OBJECTIVES

To date, PROPELLER MRI, a breathing-motion-insensitive technique, has not been assessed for cystic fibrosis (CF) lung disease. We compared this technique to CT for assessing CF lung disease in children and adults.

METHODS

Thirty-eight stable CF patients (median 21 years, range 6-51 years, 22 female) underwent MRI and CT on the same day. Study protocol included respiratory-triggered PROPELLER MRI and volumetric CT end-inspiratory and -expiratory acquisitions. Two observers scored the images using the CF-MRI and CF-CT systems. Scores were compared with intra-class correlation coefficient (ICC) and Bland-Altman plots. The sensitivity and specificity of MRI versus CT were calculated.

RESULTS

MRI sensitivity for detecting severe CF bronchiectasis was 0.33 (CI 0.09-0.57), while specificity was 100% (CI 0.88-1). ICCs for bronchiectasis and trapped air were as follows: MRI-bronchiectasis (0.79); CT-bronchiectasis (0.85); MRI-trapped air (0.51); CT-trapped air (0.87). Bland-Altman plots showed an MRI tendency to overestimate the severity of bronchiectasis in mild CF disease and underestimate bronchiectasis in severe disease.

CONCLUSIONS

Motion correction in PROPELLER MRI does not improve assessment of CF lung disease compared to CT. However, the good inter- and intra-observer agreement and the high specificity suggest that MRI might play a role in the short-term follow-up of CF lung disease (i.e. pulmonary exacerbations).

KEY POINTS

PROPELLER MRI does not match CT sensitivity to assess CF lung disease. PROPELLER MRI has lower sensitivity than CT to detect severe bronchiectasis. PROPELLER MRI has good to very good intra- and inter-observer variability. PROPELLER MRI can be used for short-term follow-up studies in CF.

Quiet Submillimeter MR Imaging of the Lung Is Feasible with a PETRA Sequence at 1.5 T

PURPOSE

To assess lung magnetic resonance (MR) imaging with a respiratory-gated pointwise encoding time reduction with radial acquisition (PETRA) sequence at 1.5 T and compare it with imaging with a standard volumetric interpolated breath-hold examination (VIBE) sequence, with extra focus on the visibility of bronchi and the signal intensity of lung parenchyma.

MATERIALS AND METHODS

The study was approved by the local ethics committee, and all subjects gave written informed consent. Twelve healthy volunteers were imaged with PETRA and VIBE sequences. Image quality was evaluated by using visual scoring, numbering of visible bronchi, and quantitative measurement of the apparent contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). For preliminary clinical assessment, three young patients with cystic fibrosis underwent both MR imaging and computed tomography (CT). Comparisons were made by using the Wilcoxon signed-rank test for means and the McNemar test for ratios. Agreement between CT and MR imaging disease scores was assessed by using the κ test.

RESULTS

PETRA imaging was performed with a voxel size of 0.86 mm(3). Overall image quality was good, with little motion artifact. Bronchi were visible consistently up to the fourth generation and in some cases up to the sixth generation. Mean CNR and SNR with PETRA were 32.4% ± 7.6 (standard deviation) and 322.2% ± 37.9, respectively, higher than those with VIBE (P < .001). Good agreement was found between CT and PETRA cystic fibrosis scores (κ = 1.0).

CONCLUSION

PETRA enables silent, free-breathing, isotropic, and submillimeter imaging of the bronchi and lung parenchyma with high CNR and SNR and may be an alternative to CT for patients with cystic fibrosis.

Novel outcome measures for clinical trials in cystic fibrosis

Cystic fibrosis (CF) is a common inherited condition caused by mutations in the gene encoding the CF transmembrane regulator protein. With increased understanding of the molecular mechanisms underlying CF and the development of new therapies there comes the need to develop new outcome measures to assess the disease, its progression and response to treatment. As there are limitations to the current endpoints accepted for regulatory purposes, a workshop to discuss novel endpoints for clinical trials in CF was held in Anaheim, California in November 2011. The pros and cons of novel outcome measures with potential utility for evaluation of novel treatments in CF were critically evaluated. The highlights of the 2011 workshop and subsequent advances in technologies and techniques that could be used to inform the development of clinical trial endpoints are summarized in this review. Pediatr Pulmonol. © 2014 The Authors. Pediatric Pulmonology published by Wiley Periodicals, Inc.

Magnetic resonance imaging of cystic fibrosis lung disease

Lung involvement in cystic fibrosis (CF) disease continues to be a major life-limiting factor of this autosomal recessive genetic disorder. Efforts made toward early diagnosis and advances in therapy have led to sustained survival of affected patients, and many are now of adult age. Because imaging provides detailed information on regional distribution of CF lung disease, repetitive imaging is required for severity assessment and therapy monitoring not only in clinical routine but also for interventional trials. Computed tomography has long succeeded chest radiograph because it provides the highest morphologic detail of airway and parenchymal changes. This is inseparably accompanied by an increase in radiation exposure to CF individuals, who are critically susceptible to, and may accumulate, relevant doses during their lifetime. Magnetic resonance imaging (MRI) as an ionizing radiation-free cross-sectional imaging modality is capable of depicting anatomic hallmarks of CF lung disease at lower spatial resolution but with enhanced tissue characterization. Comprehensive functional lung imaging (imaging of respiratory mechanics, ventilation, and lung perfusion) provides valuable additional information that cannot or can hardly be obtained by any other single diagnostic procedure. The present review article strives to present the current state of lung MRI in CF, as well as its future perspectives. Functional MRI of the CF lung is at the threshold of being considered a routine application, which, supporting early diagnosis, may help to further improve the survival of CF patients.

MR imaging of the chest in children

The application of magnetic resonance imaging (MRI) to diseases of the pediatric chest has been complicated, selective and cautious. More specifically, MRI of the pediatric lung has been a highly anticipated technique that has inherent great potential for improved imaging of the chest without the use of ionizing radiation. Practical issues impede the transition from multidetector computed tomography (MDCT) to MRI in some chest diseases in children, while other disease states are intrinsically easier to image using MRI. More rapid respiratory and cardiac rates, patient instability, sedation requirements, and the low physical density of water in the lung, hinder the requirement for maximal spatial and contrast resolution. This review is intended to serve as a functional review of the practical and currently applicable ways in which the transition of imaging the non-cardiac aspects of the pediatric chest from MDCT to MRI can be done in a clinically useful way.

HRCT and MRI of the lung in children with cystic fibrosis: comparison of different scoring systems

BACKGROUND

Chest imaging is essential in the assessment of respiratory disease in cystic fibrosis (CF). High-resolution computed tomography (HRCT) can detect progressive lung disease but involves significant delivered dose of ionizing radiation. Magnetic resonance imaging (MRI) is radiation-free but is rarely used in CF. Based on the limited information on the potential interest of chest MRI in CF pediatric patients, the aims of our study were: 1) to evaluate and compare the reproducibility of HRCT and MRI scores; and 2) to evaluate the agreement between HRCT and MRI scores using both Helbich and Eichinger scores.

METHODS

In this prospective study, CF children who were having a HRCT for their routine assessment were proposed to perform a chest MRI the same day. 17 patients were included (median age 12.7 years). Two radiologists scored independently HRCT (Helbich score) and MRI (Helbich and Eichinger scores); and established a consensus score. Concordance was assessed using the Intraclass Correlation Coefficient (ICC); and the inter-observer reproducibility between methods was compared using Fisher's Z test for dependent observations.

RESULTS

Concordance between readers was almost perfect for HRCT score (ICC = 96%) and MRI-Eichinger score (84%), and substantial for MRI-Helbich score (68%). Correlation was strong between HRCT and MRI (r = 0.86 and 0.91 for HRCT and respectively MRI-Eichinger and MRI-Helbich scores) and the concordance almost perfect and substantial (ICC = 86% and 78% for HRCT and respectively MRI-Eichinger and MRI-Helbich scores).

CONCLUSIONS

We showed that, in CF children, MRI could adequately visualize lung morphologic changes when compared with the "gold-standard" HRCT. Regarding the potential cancer risks from associated ionizing radiation with HRCT, these results lead us to propose larger intervals of time between two lung HRCTs with realization of lung MRI in the meantime.

Normalized T1 magnetic resonance imaging for assessment of regional lung function in adult cystic fibrosis patients--a cross-sectional study

BACKGROUND

Cystic fibrosis (CF) patients would benefit from a safe and effective tool to detect early-stage, regional lung disease to allow for early intervention. Magnetic Resonance Imaging (MRI) is a safe, non-invasive procedure capable of providing quantitative assessments of disease without ionizing radiation. We developed a rapid normalized T1 MRI technique to detect regional lung disease in early-stage CF patients.

MATERIALS AND METHODS

Conventional multislice, pulmonary T1 relaxation time maps were obtained for 10 adult CF patients with normal spirometry and 5 healthy non-CF control subjects using a rapid Look-Locker MRI acquisition (5 seconds/imaging slice). Each lung absolute T1 map was separated into six regions of interest (ROI) by manually selecting upper, central, and lower lung regions in the left and right lungs. In order to reduce the effects of subject-to-subject variation, normalized T1 maps were calculated by dividing each pixel in the absolute T1 maps by the mean T1 time in the central lung region. The primary outcome was the differences in mean normalized T1 values in the upper lung regions between CF patients with normal spirometry and healthy volunteers.

RESULTS

Normalized T1 (nT1) maps showed visibly reduced subject-to-subject variation in comparison to conventional absolute T1 maps for healthy volunteers. An ROI analysis showed that the variation in the nT1 values in all regions was ≤2% of the mean. The primary outcome, the mean (SD) of the normalized T1 values in the upper right lung regions, was significantly lower in the CF subjects [.914 (.037)] compared to the upper right lung regions of the healthy subjects [.983 (.003)] [difference of .069 (95% confidence interval .032-.105); p = .001). Similar results were seen in the upper left lung region.

CONCLUSION

Rapid normalized T1 MRI relaxometry obtained in 5 seconds/imaging slice may be used to detect regional early-stage lung disease in CF patients.

Magnetic resonance imaging of pediatric lung parenchyma, airways, vasculature, ventilation, and perfusion: state of the art

Magnetic resonance (MR) imaging is a noninvasive imaging modality, particularly attractive for pediatric patients given its lack of ionizing radiation. Despite many advantages, the physical properties of the lung (inherent low signal-to-noise ratio, magnetic susceptibility differences at lung-air interfaces, and respiratory and cardiac motion) have posed technical challenges that have limited the use of MR imaging in the evaluation of thoracic disease in the past. However, recent advances in MR imaging techniques have overcome many of these challenges. This article discusses these advances in MR imaging techniques and their potential role in the evaluation of thoracic disorders in pediatric patients.

Overview of positron emission tomography, hybrid positron emission tomography instrumentation, and positron emission tomography quantification

Positron emission tomography (PET) is a powerful quantitative molecular imaging technique that is complementary to structural imaging techniques for purposes of disease detection and characterization. This review article provides a brief overview of PET, hybrid PET instrumentation, and PET quantification.