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

Pulmonary MRI in Newborns and Children

Lung MRI is an important tool in the assessment and monitoring of pediatric and neonatal lung disorders. MRI can provide both similar and complementary image contrast to computed tomography for imaging the lung macrostructure, and beyond this, a number of techniques have been developed for imaging the key functions of the lungs, namely ventilation, perfusion, and gas exchange, through the use of free-breathing proton and hyperpolarized gas MRI. Here, we review the state-of-the-art in MRI methods that have found utility in pediatric and neonatal lung imaging, the structural and physiological information that can be gleaned from such images, and strategies that have been developed to deal with respiratory (and cardiac) motion, and other technological challenges. The application of lung MRI in neonatal and pediatric lung conditions, in particular bronchopulmonary dysplasia, cystic fibrosis, and asthma, is reviewed, highlighting our collective experiences in the clinical translation of these methods and technology, and the key current and future potential avenues for clinical utility of this methodology. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

MDCT and MRI in Bronchiectasis in Older Children and Young Adults - A Non-Inferiority Trial

OBJECTIVES

To compare and evaluate the usefulness of magnetic resonance imaging (MRI) with computed tomography (CT) in bronchiectasis; to compare MRI and CT scores with pulmonary function tests (PFT) and to evaluate the role of Diffusion-weighted imaging (DWI) in bronchiectasis.

METHODS

In this prospective study, 25 patients between 7-21 y of age with a clinical/radiological diagnosis of bronchiectasis underwent MDCT and MRI chest. MRI and CT scoring was performed using modified Bhalla-Helbich's score by two independent radiologists for all parameters. A final consensus score was recorded. The overall image quality of different MRI sequences to identify pathologies was also assessed. Appropriate statistical tests were used for inter-observer agreements, and correlation amongst CT and MRI; as well as CT, MRI and PFT.

RESULTS

Strong agreement (ICC 0.80-0.95) between CT and MRI was seen for extent and severity of bronchiectasis, number of bullae, sacculation/abscess, emphysema, collapse/ consolidation, mucus plugging, and mosaic perfusion. Overall CT and MRI scores had perfect concordance (ICC 0.978). Statistically significant (p-value <0.01) intra-observer and inter-observer agreement for all CT and MRI score parameters were seen. A strong negative correlation was seen between total CT and MRI severity scores and forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), forced expiratory flow (FEF) 25-75%. DWI MR, with an apparent diffusion coefficient (ADC) cut-off of 1.62 × 10-3 mm3/s had a sensitivity of 70% and specificity of 75% in detecting true mucus plugs.

CONCLUSIONS

MRI with DWI can be considered as a radiation-free alternative in the diagnostic algorithm for assessment of lung changes in bronchiectasis, especially in follow-up.

[Evaluation of the Latest Motion Correction Techniques in Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) Imaging across Different Vendors]

PURPOSE

To evaluate the robustness of the latest periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technology from each vendor against head movements and to investigate their characteristics for effective clinical use.

METHODS

Using a phantom simulating the T2-weighted image of the human brain, images were acquired with devices from CANON MEDICAL SYSTEMS (Tochigi, Japan; hereinafter "Canon"), GE HealthCare (Chicago, IL, USA; hereinafter "GE"), Philips (Amsterdam, Netherlands), and Siemens Healthineers (Forchheim, Germany; hereinafter "SIEMENS"). The head motion patterns were divided into rotation angle dependency (single rotation and multiple rotations) and rotation frequency dependency and evaluated using structural similarity (SSIM).

RESULTS

For rotation angle dependency, Canon was robust against small rotation angles and fine movements. Despite the rotation angle, GE was robust against movements, with deep learning reconstruction (DLR) improving correction functionality. Philips could be used with compressed sensitivity encoding (CS), and robustness varied with blade width. SIEMENS was robust against large movements. For rotation frequency dependency, results were similar across the 4 vendors.

CONCLUSION

The rotation angle and rotation frequency dependencies of the PROPELLER technology from the 4 vendors were quantitatively evaluated. Understanding the characteristics of PROPELLER allows for the possibility of providing diagnostic-quality images even for patients who move during head MRI exams by appropriately using PROPELLER.

Automated lung segmentation on chest MRI in children with cystic fibrosis

Introduction

Segmentation of lung structures in medical imaging is crucial for the application of automated post-processing steps on lung diseases like cystic fibrosis (CF). Recently, machine learning methods, particularly neural networks, have demonstrated remarkable improvements, often outperforming conventional segmentation methods. Nonetheless, challenges still remain when attempting to segment various imaging modalities and diseases, especially when the visual characteristics of pathologic findings significantly deviate from healthy tissue.

Methods

Our study focuses on imaging of pediatric CF patients [mean age, standard deviation (7.50 ± 4.6)], utilizing deep learning-based methods for automated lung segmentation from chest magnetic resonance imaging (MRI). A total of 165 standardized annual surveillance MRI scans from 84 patients with CF were segmented using the nnU-Net framework. Patient cases represented a range of disease severities and ages. The nnU-Net was trained and evaluated on three MRI sequences (BLADE, VIBE, and HASTE), which are highly relevant for the evaluation of CF induced lung changes. We utilized 40 cases for training per sequence, and tested with 15 cases per sequence, using the Sørensen-Dice-Score, Pearson's correlation coefficient (r), a segmentation questionnaire, and slice-based analysis.

Results

The results demonstrated a high level of segmentation performance across all sequences, with only minor differences observed in the mean Dice coefficient: BLADE (0.96 ± 0.05), VIBE (0.96 ± 0.04), and HASTE (0.95 ± 0.05). Additionally, the segmentation quality was consistent across different disease severities, patient ages, and sizes. Manual evaluation identified specific challenges, such as incomplete segmentations near the diaphragm and dorsal regions. Validation on a separate, external dataset of nine toddlers (2-24 months) demonstrated generalizability of the trained model achieving a Dice coefficient of 0.85 ± 0.03.

Discussion and conclusion

Overall, our study demonstrates the feasibility and effectiveness of using nnU-Net for automated segmentation of lung halves in pediatric CF patients, showing promising directions for advanced image analysis techniques to assist in clinical decision-making and monitoring of CF lung disease progression. Despite these achievements, further improvements are needed to address specific segmentation challenges and enhance generalizability.

Acute Respiratory Failure in Children: A Clinical Update on Diagnosis

Acute respiratory failure (ARF) is a sudden failure of the respiratory system to ensure adequate gas exchanges. Numerous clinical conditions may cause ARF, including pneumonia, obstructive lung diseases (e.g., asthma), restrictive diseases such as neuromuscular diseases (e.g., spinal muscular atrophy and muscular dystrophy), and albeit rarely, interstitial lung diseases. Children, especially infants, may be more vulnerable to ARF than adults due to anatomical and physiological features of the respiratory system. Assessing respiratory impairment in the pediatric population is particularly challenging as children frequently present difficulties in reporting symptoms and due to compliance and cooperation in diagnostic tests. The evaluation of clinical and anamnestic aspects represents the cornerstone of ARF diagnosis: first level exams (e.g., arterial blood gas analysis) confirm and evaluate the severity of the ARF and second level exams help to uncover the underlying cause. Prompt management is critical, with supplemental oxygen, mechanical ventilation, and the treatment of the underlying problem. The aim of this review is to provide a comprehensive summary of the current state of the art in diagnosing pediatric ARF, with a focus on pathophysiology, novel imaging applications, and new perspectives, such as biomarkers and artificial intelligence.

Magnetic Resonance Imaging of Pediatric Lungs and Airways: New Paradigm for Practical Daily Clinical Use

Disorders of the lungs and airways are among the most common indications for diagnostic imaging in infants and children. Traditionally, chest radiograph has been the first-line imaging test for detecting these disorders and when cross-sectional imaging is necessary, computed tomography (CT) has typically been the next step. However, due to concerns about the potentially harmful effects of ionizing radiation, pediatric imaging in general has begun to shift away from CT toward magnetic resonance imaging (MRI) as a preferred modality. Several unique technical challenges of chest MRI, including motion artifact from respiratory and cardiac motion as well as low signal-to-noise ratios secondary to relatively low proton density in the lung have slowed this shift in thoracic imaging. However, technical advances in MRI in recent years, including developments in non-Cartesian MRI data sampling methods such as radial, spiral, and PROPELLER imaging and the development of ultrashort TE and zero TE sequences that render CT-like high-quality imaging with minimal motion artifact have allowed for a shift to MRI for evaluation of lung and large airways in centers with specialized expertise. This article presents a practical approach for radiologists in current practice to begin to consider MRI for evaluation of the pediatric lung and large airways and begin to implement it in their practices. The current role for MRI in the evaluation of disorders of the pediatric lung and large airways is reviewed, and example cases are presented. Challenges for MRI of the lung and large airways in children are discussed, practical tips for patient preparation including sedation are described, and imaging techniques suitable for current clinical practice are presented.

Short-term structural and functional changes after airway clearance therapy in cystic fibrosis

BACKGROUND

Airway clearance therapy (ACT) with a high-frequency chest wall oscillation (HFCWO) vest is a common but time-consuming treatment. Its benefit to quality of life for cystic fibrosis (CF) patients is well established but has been questioned recently as new highly-effective modulator therapies begin to change the treatment landscape. 129Xe ventilation MRI has been shown to be very sensitive to lung obstruction in mild CF disease, making it an ideal tool to identify and quantify subtle, regional changes.

METHODS

20 CF patients (ages 20.7 ± 5.1 years) refrained from performing ACT before arriving for a single-day visit. Multiple-breath washout (MBW), spirometry, Xe MRI, and ultrashort echo-time (UTE) MRI were obtained twice-before and after patients performed ACT using their prescribed HFCWO vests (average 4.7 ± 0.5 h). UTE MRIs were scored for structural abnormalities, and standard functional metrics were obtained from MBW, spirometry, and Xe MRI-FEV1,pp, LCI2.5, and VDPN4, respectively.

RESULTS

Spirometry and Xe MRI detected significant improvements in lung function post-ACT. 15/20 patients showed improvements from a baseline median of 92% FEV1,pp. Similarly, 16/20 patients showed improvements in Xe MRI from a baseline median of 15.2% VDPN4. Average individual changes were +2.6% in FEV1,pp and -1.3% in VDPN4, but without spatial correlations to easily-identifiable causative structural defects (e.g. mucus plugs or bronchiectasis) on UTE MRI.

CONCLUSIONS

Lung function improved after a single instance of HFCWO-vest ACT and was detectable by spirometry and Xe MRI. The only common structural abnormalities were mucus plugs, which corresponded to ventilation defects, but ventilation defects were often present without visible abnormalities.

Strain Identification and Drug Resistance Analysis of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry in Nontuberculous Mycobacterial Lung Disease

Objective

To evaluate the clinical value of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in detecting Nontuberculous mycobacteria (NTM).

Methods

The clinical data of 172 patients with suspected NTM lung disease were collected from our hospital from January 1, 2018, to December 30, 2021. The results were compared with those of BACTEC MGIT 960 in liquid culture and gene chip. This study also utilised MALDI-TOF MS to detect macrolide (MA) and amikacin (Am) mutations.

Results

One hundred thirty-seven cases of NTM pulmonary disease were confirmed by identifying the NTM gene chip in bronchoalveolar lavage fluid and/or MALDI-TOF MS detection. The positive predictive value and negative predictive value were 100% (131/131) and 85.37% (35/41), respectively, and the consistency of the two methods was high (kappa=0.899). For the drug resistance detection of MAs, the consistency rate between MALDI-TOF MS detection and drug sensitivity detection was 97.71% (128/131), the sensitivity was 81.25% (13/16) and the specificity was 100% (115/115). The positive and negative predictive values were 100% (13/13) and 93.75% (115/118), respectively. There was no coincidental consistency between the two methods, and the consistency was high (P<0.001, kappa=0.884). For the drug resistance test of Am, the consistency rate between the MALDI-TOF MS test and the drug sensitivity test was 93.13% (122/131), the sensitivity was 93.52% (101/108), the specificity was 90.91% (21/23) and the positive predictive value and negative predictive value were 98.06% (101/103) and 75.00% (21/28), respectively. The two methods had high consistency, and the consistency was not coincidental (P<0.001, kappa=0.781).

Conclusion

Utilising MALDI-TOF MS has a good consistency with the drug resistance gene chip method and can be a rapid and effective method to identify strains and drug resistance of NTM. Therefore, it has certain clinical application value in patients with suspected NTM lung disease.

Comparison of deep learning-based reconstruction of PROPELLER Shoulder MRI with conventional reconstruction

OBJECTIVE

To compare the image quality and agreement among conventional and accelerated periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) MRI with both conventional reconstruction (CR) and deep learning-based reconstruction (DLR) methods for evaluation of shoulder.

MATERIALS AND METHODS

We included patients who underwent conventional (acquisition time, 8 min) and accelerated (acquisition time, 4 min and 24 s; 45% reduction) PROPELLER shoulder MRI using both CR and DLR methods between February 2021 and February 2022 on a 3 T MRI system. Quantitative evaluation was performed by calculating the signal-to-noise ratio (SNR). Two musculoskeletal radiologists compared the image quality using conventional sequence with CR as the reference standard. Interobserver agreement between image sets for evaluating shoulder was analyzed using weighted/unweighted kappa statistics.

RESULTS

Ninety-two patients with 100 shoulder MRI scans were included. Conventional sequence with DLR had the highest SNR (P < .001), followed by accelerated sequence with DLR, conventional sequence with CR, and accelerated sequence with CR. Comparison of image quality by both readers revealed that conventional sequence with DLR (P = .003 and P < .001) and accelerated sequence with DLR (P = .016 and P < .001) had better image quality than the conventional sequence with CR. Interobserver agreement was substantial to almost perfect for detecting shoulder abnormalities (κ = 0.600-0.884). Agreement between the image sets was substantial to almost perfect (κ = 0.691-1).

CONCLUSION

Accelerated PROPELLER with DLR showed even better image quality than conventional PROPELLER with CR and interobserver agreement for shoulder pathologies comparable to that of conventional PROPELLER with CR, despite the shorter scan time.

MR imaging of the airways

The need for airway imaging is defined by the limited sensitivity of common clinical tests like spirometry, lung diffusion (DLCO) and blood gas analysis to early changes of peripheral airways and to inhomogeneous regional distribution of lung function deficits. Therefore, X-ray and computed tomography (CT) are frequently used to complement the standard tests.As an alternative, magnetic resonance imaging (MRI) offers radiation-free lung imaging, but at lower spatial resolution. Non-contrast enhanced MRI shows healthy airways down to the first subsegmental level/4^th order (CT: eighth). Bronchiectasis can be identified by wall thickening and fluid accumulation. Smaller airways become visible, when altered by peribronchiolar inflammation or mucus retention (tree-in-bud sign).The strength of MRI is functional imaging. Dynamic, time-resolved MRI directly visualizes expiratory airway collapse down to the lobar level (CT: segmental level). Obstruction of even smaller airways becomes visible as air trapping on the expiratory scans. MRI with hyperpolarized noble gases (³He, ¹²⁹Xe) directly shows the large airways and peripheral lung ventilation. Dynamic contrast-enhanced MRI (DCE MRI) indirectly shows airway dysfunction as perfusion deficits resulting from hypoxic vasoconstriction of the dependent lung volumes. Further promising scientific approaches such as non-contrast enhanced, ventilation-/perfusion-weighted MRI from periodic signal changes of respiration and blood flow are in development.In summary, MRI of the lungs and airways excels with its unique combination of morphologic and functional imaging capacities for research (e.g., in chronic obstructive lung disease or asthma) as well as for clinical imaging (e.g., in cystic fibrosis).

Management of respiratory tract exacerbations in people with cystic fibrosis: Focus on imaging

Respiratory tract exacerbations play a crucial role in progressive lung damage of people with cystic fibrosis, representing a major determinant in the loss of functional lung tissue, quality of life and patient survival. Detection and monitoring of respiratory tract exacerbations are challenging for clinicians, since under- and over-treatment convey several risks for the patient. Although various diagnostic and monitoring tools are available, their implementation is hampered by the current definition of respiratory tract exacerbation, which lacks objective "cut-offs" for clinical and lung function parameters. In particular, the latter shows a large variability, making the current 10% change in spirometry outcomes an unreliable threshold to detect exacerbation. Moreover, spirometry cannot be reliably performed in preschool children and new emerging tools, such as the forced oscillation technique, are still complementary and need more validation. Therefore, lung imaging is a key in providing respiratory tract exacerbation-related structural and functional information. However, imaging encompasses several diagnostic options, each with different advantages and limitations; for instance, conventional chest radiography, the most used radiological technique, may lack sensitivity and specificity in respiratory tract exacerbations diagnosis. Other methods, including computed tomography, positron emission tomography and magnetic resonance imaging, are limited by either radiation safety issues or the need for anesthesia in uncooperative patients. Finally, lung ultrasound has been proposed as a safe bedside option but it is highly operator-dependent and there is no strong evidence of its possible use during respiratory tract exacerbation. This review summarizes the clinical challenges of respiratory tract exacerbations in patients with cystic fibrosis with a special focus on imaging. Firstly, the definition of respiratory tract exacerbation is examined, while diagnostic and monitoring tools are briefly described to set the scene. This is followed by advantages and disadvantages of each imaging technique, concluding with a diagnostic imaging algorithm for disease monitoring during respiratory tract exacerbation in the cystic fibrosis patient.

Application of deep learning-based image reconstruction in MR imaging of the shoulder joint to improve image quality and reduce scan time

OBJECTIVES

To compare the image quality and diagnostic performance of conventional motion-corrected periodically rotated overlapping parallel line with enhanced reconstruction (PROPELLER) MRI sequences with post-processed PROPELLER MRI sequences using deep learning-based (DL) reconstructions.

METHODS

In this prospective study of 30 patients, conventional (19 min 18 s) and accelerated MRI sequences (7 min 16 s) using the PROPELLER technique were acquired. Accelerated sequences were post-processed using DL. The image quality and diagnostic confidence were qualitatively assessed by 2 readers using a 5-point Likert scale. Analysis of the pathological findings of cartilage, rotator cuff tendons and muscles, glenoid labrum and subacromial bursa was performed. Inter-reader agreement was calculated using Cohen's kappa statistic. Quantitative evaluation of image quality was measured using the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).

RESULTS

Mean image quality and diagnostic confidence in evaluation of all shoulder structures were higher in DL sequences (p value = 0.01). Inter-reader agreement ranged between kappa values of 0.155 (assessment of the bursa) and 0.947 (assessment of the rotator cuff muscles). In 17 cases, thickening of the subacromial bursa of more than 2 mm was only visible in DL sequences. The pathologies of the other structures could be properly evaluated by conventional and DL sequences. Mean SNR (p value = 0.01) and CNR (p value = 0.02) were significantly higher for DL sequences.

CONCLUSIONS

The accelerated PROPELLER sequences with DL post-processing showed superior image quality and higher diagnostic confidence compared to the conventional PROPELLER sequences. Subacromial bursa can be thoroughly assessed in DL sequences, while the other structures of the shoulder joint can be assessed in conventional and DL sequences with a good agreement between sequences.

KEY POINTS

• MRI of the shoulder requires long scan times and can be hampered by motion artifacts. • Deep learning-based convolutional neural networks are used to reduce image noise and scan time while maintaining optimal image quality. The radial k-space acquisition technique (PROPELLER) can reduce the scan time and has potential to reduce motion artifacts. • DL sequences show a higher diagnostic confidence than conventional sequences and therefore are preferred for assessment of the subacromial bursa, while conventional and DL sequences show comparable performance in the evaluation of the shoulder joint.

Role of MRI in the Evaluation of Pulmonary Sequel Following COVID-19 Acute Respiratory Distress Syndrome (ARDS)

To evaluate the role of magnetic resonance imaging (MRI) chest as an alternative modality to CT chest for follow-up of patients recovered from severe COVID-19 acute respiratory distress syndrome (ARDS). A total of 25 subjects (16 [64%] men; mean age 54.84 years ± 12.35) who survived COVID-19 ARDS and fulfilled the inclusion criteria were enrolled prospectively. All the patients underwent CT and MRI chest (on the same day) at 6-weeks after discharge. MRI chest was acquired on 1.5T MRI using HASTE, BLADE, VIBE, STIR, and TRUFI sequences and evaluated for recognition of GGOs, consolidation, reticulations/septal thickening, parenchymal bands, and bronchial dilatation with CT chest as the gold standard. The differences were assessed by independent-sample t-test and Mann-Whitney U test. P-value of less than 0.05 was taken significant. There was a strong agreement (k = 0.8-1, P<0.01) between CT and MRI chest. On CT, the common manifestations were: GGOs (n=24, 96%), septal thickening/reticulations (n=24, 96%), bronchial dilatation (n=16, 64%), parenchymal bands (n=14, 56%), pleural thickening (n=8, 32%), consolidation (n=4, 16%) and crazy-paving (n=4, 16%). T2W HASTE, T2W BLADE, and T1 VIBE sequences showed 100% (95% CI, 40-100) sensitivity and 100% (95% CI, 3-100) specificity for detecting GGOs, septal thickening/reticulations, pleural thickening, consolidation, and crazy-paving. The overall sensitivity of MRI for detection of bronchial dilatation and parenchymal bands were 88.9% (95% CI, 77-100) and 92.9% (95% CI, 66-100), respectively; and specificity was 100% (95% CI, 29-100) for both findings. MRI chest, being radiation-free imaging modality can act as an alternative to CT chest in the evaluation of lung changes in patients recovered from COVID-19 pneumonia.

Lung and large airway imaging: magnetic resonance imaging versus computed tomography

Disorders of the respiratory system are common in children and imaging plays an important role for initial diagnosis and follow-up evaluation. Radiographs are typically the first-line imaging test for respiratory symptoms in children and, when advanced imaging is required, CT has been the most frequently used imaging modality. However, because of increasing concern about potentially harmful effects of ionizing radiation on children, there has been a shift toward MRI in pediatric imaging. Although MRI of chest in children presents many technical challenges, recent advances in MRI technology are overcoming many of these issues, and MRI is now being used for evaluating the lung and large airway in children at centers with expertise in pediatric chest MRI. In this article we review the state of pediatric lung and large airway imaging, with an emphasis on cross-sectional modalities and the roles of MRI versus CT.

State-of-the-art review of lung imaging in cystic fibrosis with recommendations for pulmonologists and radiologists from the "iMAging managEment of cySTic fibROsis" (MAESTRO) consortium

OBJECTIVE

Imaging represents an important noninvasive means to assess cystic fibrosis (CF) lung disease, which remains the main cause of morbidity and mortality in CF patients. While the development of new imaging techniques has revolutionised clinical practice, advances have posed diagnostic and monitoring challenges. The authors aim to summarise these challenges and make evidence-based recommendations regarding imaging assessment for both clinicians and radiologists.

STUDY DESIGN

A committee of 21 experts in CF from the 10 largest specialist centres in Italy was convened, including a radiologist and a pulmonologist from each centre, with the overall aim of developing clear and actionable recommendations for lung imaging in CF. An a priori threshold of at least 80% of the votes was required for acceptance of each statement of recommendation.

RESULTS

After a systematic review of the relevant literature, the committee convened to evaluate 167 articles. Following five RAND conferences, consensus statements were developed by an executive subcommittee. The entire consensus committee voted and approved 28 main statements.

CONCLUSIONS

There is a need for international guidelines regarding the appropriate timing and selection of imaging modality for patients with CF lung disease; timing and selection depends upon the clinical scenario, the patient's age, lung function and type of treatment. Despite its ubiquity, the use of the chest radiograph remains controversial. Both computed tomography and magnetic resonance imaging should be routinely used to monitor CF lung disease. Future studies should focus on imaging protocol harmonisation both for computed tomography and for magnetic resonance imaging. The introduction of artificial intelligence imaging analysis may further revolutionise clinical practice by providing fast and reliable quantitative outcomes to assess disease status. To date, there is no evidence supporting the use of lung ultrasound to monitor CF lung disease.

Cross-sectional analysis of follow-up chest MRI and chest CT scans in patients previously affected by COVID-19

Purpose

The aim of the study was to prospectively evaluate the agreement between chest magnetic resonance imaging (MRI) and computed tomography (CT) and to assess the diagnostic performance of chest MRI relative to that of CT during the follow-up of patients recovered from coronavirus disease 2019.

Materials and methods

Fifty-two patients underwent both follow-up chest CT and MRI scans, evaluated for ground-glass opacities (GGOs), consolidation, interlobular septal thickening, fibrosis, pleural indentation, vessel enlargement, bronchiolar ectasia, and changes compared to prior CT scans. DWI/ADC was evaluated for signal abnormalities suspicious for inflammation. Agreement between CT and MRI was assessed with Cohen’s k and weighted k. Measures of diagnostic accuracy of MRI were calculated.

Results

The agreement between CT and MRI was almost perfect for consolidation (k = 1.00) and change from prior CT (k = 0.857); substantial for predominant pattern (k = 0.764) and interlobular septal thickening (k = 0.734); and poor for GGOs (k = 0.339), fibrosis (k = 0.224), pleural indentation (k = 0.231), and vessel enlargement (k = 0.339). Meanwhile, the sensitivity of MRI was high for GGOs (1.00), interlobular septal thickening (1.00), and consolidation (1.00) but poor for fibrotic changes (0.18), pleural indentation (0.23), and vessel enlargement (0.50) and the specificity was overall high. DWI was positive in 46.0% of cases.

Conclusions

The agreement between MRI and CT was overall good. MRI was very sensitive for GGOs, consolidation and interlobular septal thickening and overall specific for most findings. DWI could be a reputable imaging biomarker of inflammatory activity.

Clinical application of ultrashort echo-time MRI for lung pathologies in children

Lung magnetic resonance imaging (MRI) is considered to be challenging, because the low proton density of the tissue, fast signal decay, and respiratory artefacts hamper adequate image quality. MRI of the lungs and thorax is increasingly used in the paediatric population, because it is a radiation-free alternative to chest CT. Recently, ultrashort echo-time (UTE) sequences have been introduced into clinical MRI protocols, in order to improve the contrast-to-noise ratio due to reduced susceptibility artefacts and to depict structural alterations comparable to CT. The purpose of this review is to provide an overview of various clinical conditions and pathologies in the paediatric chest depicted by an UTE sequence, the so-called three-dimensional (3D) Cones sequence, in comparison with conventional MRI sequences. Besides describing typical features of cystic fibrosis, we present UTE application in other more or less common paediatric lung pathologies, for instance, interstitial pneumopathies, pulmonary infections, and congenital pulmonary malformations.

Crowdsourcing airway annotations in chest computed tomography images

Measuring airways in chest computed tomography (CT) scans is important for characterizing diseases such as cystic fibrosis, yet very time-consuming to perform manually. Machine learning algorithms offer an alternative, but need large sets of annotated scans for good performance. We investigate whether crowdsourcing can be used to gather airway annotations. We generate image slices at known locations of airways in 24 subjects and request the crowd workers to outline the airway lumen and airway wall. After combining multiple crowd workers, we compare the measurements to those made by the experts in the original scans. Similar to our preliminary study, a large portion of the annotations were excluded, possibly due to workers misunderstanding the instructions. After excluding such annotations, moderate to strong correlations with the expert can be observed, although these correlations are slightly lower than inter-expert correlations. Furthermore, the results across subjects in this study are quite variable. Although the crowd has potential in annotating airways, further development is needed for it to be robust enough for gathering annotations in practice. For reproducibility, data and code are available online: http://github.com/adriapr/crowdairway.git.

A multimodal approach to detect and monitor early lung disease in cystic fibrosis

Introduction: In the early stages, lung involvement in cystic fibrosis (CF) can be silent, with disease progression occurring in the absence of clinical symptoms. Irreversible airway damage is present in the early stages of disease; however, reliable biomarkers of early damage due to inflammation and infection that are universally applicable in day-to-day patient management have yet to be identified.Areas covered: At present, the main methods of detecting and monitoring early lung disease in CF are the lung clearance index (LCI), computed tomography (CT), and magnetic resonance imaging (MRI). LCI can be used to detect patients who may require more intense monitoring, identify exacerbations, and monitor responses to new interventions. High-resolution CT detects structural alterations in the lungs of CF patients with the best resolution of current imaging techniques. MRI is a radiation-free imaging alternative that provides both morphological and functional information. The role of MRI for short-term follow-up and pulmonary exacerbations is currently being investigated.Expert opinion: The roles of LCI and MRI are expected to expand considerably over the next few years. Meanwhile, closer collaboration between pulmonology and radiology specialties is an important goal toward improving care and optimizing outcomes in young patients with CF.

Deep Anatomical Context Feature Learning for Cephalometric Landmark Detection

In the past decade, anatomical context features have been widely used for cephalometric landmark detection and significant progress is still being made. However, most existing methods rely on handcrafted graphical models rather than incorporating anatomical context during training, leading to suboptimal performance. In this study, we present a novel framework that allows a Convolutional Neural Network (CNN) to learn richer anatomical context features during training. Our key idea consists of the Local Feature Perturbator (LFP) and the Anatomical Context loss (AC loss). When training the CNN, the LFP perturbs a cephalometric image based on prior anatomical distribution, forcing the CNN to gaze relevant features more globally. Then AC loss helps the CNN to learn the anatomical context based on spatial relationships between the landmarks. The experimental results demonstrate that the proposed framework makes the CNN learn richer anatomical representation, leading to increased performance. In the performance comparisons, the proposed scheme outperforms state-of-the-art methods on the ISBI 2015 Cephalometric X-ray Image Analysis Challenge.

Three-dimensional magnetic resonance imaging ultrashort echo-time cones for assessing lung density in pediatric patients

BACKGROUND

MRI of lung parenchyma is challenging because of the rapid decay of signal by susceptibility effects of aerated lung on routine fast spin-echo sequences.

OBJECTIVE

To assess lung signal intensity in children on ultrashort echo-time sequences in comparison to a fast spin-echo technique.

MATERIALS AND METHODS

We conducted a retrospective study of lung MRI obtained in 30 patients (median age 5 years, range 2 months to 18 years) including 15 with normal lungs and 15 with cystic fibrosis. On a fast spin-echo sequence with radial readout and an ultrashort echo-time sequence, both lungs were segmented and signal intensities were extracted. We compared lung-to-background signal ratios and histogram analysis between the two patient cohorts using non-parametric tests and correlation analysis.

RESULTS

On ultrashort echo-time the lung-to-background ratio was age-dependent, ranging from 3.15 to 1.33 with high negative correlation (R_s = -0.86). Signal in posterior dependent portions of the lung was 18% and 11% higher than that of the anterior lung for age groups 0-2 and 2-18 years, respectively. The fast spin-echo sequence showed no variation of signal ratios by age or location, with a median of 0.99 (0.98-1.02). Histograms of ultrashort echo-time slices between controls and children with aggravated cystic fibrosis with mucus plugging and wall thickening exhibited significant discrepancies that differentiated between normal and pathological lungs.

CONCLUSION

Signal intensity of lung on ultrashort echo-time is higher than that on fast spin-echo sequences, is age-dependent and shows a gravity-dependent anterior to posterior gradient. This signal variation appears similar to lung density described on CT.

Quantification of Cystic Fibrosis Lung Disease with Radiomics-based CT Scores

Purpose

To develop radiomics-based CT scores for assessing lung disease severity and exacerbation risk in adult patients with cystic fibrosis (CF).

Materials and Methods

This two-center retrospective observational study was approved by an institutional ethics committee, and the need for patient consent was waived. A total of 215 outpatients with CF referred for unenhanced follow-up chest CT were evaluated in two different centers between January 2013 and December 2016. After lung segmentation, chest CT scans from center 1 (training cohort, 162 patients [median age, 29 years; interquartile range {IQR}, 24-36 years; 84 men]) were used to build CT scores from 38 extracted CT features, using five different machine learning techniques trained to predict a clinical prognostic score, the Nkam score. The correlations between the developed CT scores, two different clinical prognostic scores (Liou and CF-ABLE), forced expiratory volume in 1 second (FEV₁), and risk of respiratory exacerbations were evaluated in the test cohort (center 2, 53 patients [median age, 27 years; IQR, 22-35 years; 34 men]) using the Spearman rank coefficient.

Results

In the test cohort, all radiomics-based CT scores showed moderate to strong correlation with the Nkam score (R = 0.57 to 0.63, P < .001) and Liou scores (R = -0.55 to -0.65, P < .001), whereas the correlation with CF-ABLE score was weaker (R = 0.28 to 0.38, P = .005 to .048). The developed CT scores showed strong correlation with predicted FEV₁ (R = -0.62 to -0.66, P < .001) and weak to moderate correlation with the number of pulmonary exacerbations to occur in the 12 months after the CT examination (R = 0.38 to 0.55, P < .001 to P = .006).

Conclusion

Radiomics can be used to build automated CT scores that correlate to clinical severity and exacerbation risk in adult patients with CF.Supplemental material is available for this article.See also the commentary by Elicker and Sohn in this issue.© RSNA, 2020.

The Clinical Use of Lung MRI in Cystic Fibrosis: What, Now, How?

To assess airway and lung parenchymal damage noninvasively in cystic fibrosis (CF), chest MRI has been historically out of the scope of routine clinical imaging because of technical difficulties such as low proton density and respiratory and cardiac motion. However, technological breakthroughs have emerged that dramatically improve lung MRI quality (including signal-to-noise ratio, resolution, speed, and contrast). At the same time, novel treatments have changed the landscape of CF clinical care. In this contemporary context, there is now consensus that lung MRI can be used clinically to assess CF in a radiation-free manner and to enable quantification of lung disease severity. MRI can now achieve three-dimensional, high-resolution morphologic imaging, and beyond this morphologic information, MRI may offer the ability to sensitively differentiate active inflammation vs scarring tissue. MRI could also characterize various forms of inflammation for early guidance of treatment. Moreover, functional information from MRI can be used to assess regional, small-airway disease with sensitivity to detect small changes even in patients with mild CF. Finally, automated quantification methods have emerged to support conventional visual analyses for more objective and reproducible assessment of disease severity. This article aims to review the most recent developments of lung MRI, with a focus on practical application and clinical value in CF, and the perspectives on how these modern techniques may converge and impact patient care soon.

PET/MR in Head and Neck Cancer - An Update

In academic centers, PET/MR has taken the road to clinical nuclear medicine in the past 6 years since the last review on its applications in head and neck cancer patients in this journal. Meanwhile, older sequential PET + MR machines have largely vanished from clinical sites, being replaced by integrated simultaneous PET/MR scanners. Evidence from several studies suggests that PET/MR overall performs equally well as PET/CT in the staging and restaging of head and neck cancer and in radiation therapy planning. PET/MR appears to offer advantages in the characterization and prognostication of head and neck malignancies through multiparametric imaging, which demands an exact preparation and validation of imaging modalities, however. The majority of available clinical PET/MR studies today covers FDG imaging of squamous cell carcinoma arising from a broad spectrum of locations in the upper aerodigestive tract. In the future, specific PET/MR studies are desired that address specific histopathological tumor entities, nonepithelial malignancies, such as major salivary gland tumors, squamous cell carcinomas arising in specific locations, and malignancies imaged with non-FDG radiotracers. With the advent of digital PET/CT scanners, PET/MR is expected to partake in future technical developments, such as novel iterative reconstruction techniques and deviceless motion correction for respiration and gross movement in the head and neck region. Owing to the still comparably high costs of PET/MR scanners and facility requirements on the one hand, and the concentration of multidisciplinary head and neck cancer treatment mainly at academic centers on the other hand, a more widespread use of this imaging modality outside major hospitals is currently limited.

Fast chemical exchange saturation transfer imaging based on PROPELLER acquisition and deep neural network reconstruction

PURPOSE

To develop a method for fast chemical exchange saturation transfer (CEST) imaging.

METHODS

The periodically rotated overlapping parallel lines enhanced reconstruction (PROPELLER) sampling scheme was introduced to shorten the acquisition time. Deep neural network was employed to reconstruct CEST contrast images. Numerical simulation and experiments on a creatine phantom, hen egg, and in vivo tumor rat brain were performed to test the feasibility of this method.

RESULTS

The results from numerical simulation and experiments show that there is no significant difference between reference images and CEST-PROPELLER reconstructed images under an acceleration factor of 8.

CONCLUSION

Although the deep neural network is trained entirely on synthesized data, it works well on reconstructing experimental data. The proof of concept study demonstrates that the combination of the PROPELLER sampling scheme and the deep neural network enables considerable acceleration of saturated image acquisition and may find applications in CEST MRI.

Airway tapering: an objective image biomarker for bronchiectasis

Purpose

To estimate airway tapering in control subjects and to assess the usability of tapering as a bronchiectasis biomarker in paediatric populations.

Methods

Airway tapering values were semi-automatically quantified in 156 children with control CTs collected in the Normal Chest CT Study Group. Airway tapering as a biomarker for bronchiectasis was assessed on spirometer-guided inspiratory CTs from 12 patients with bronchiectasis and 12 age- and sex-matched controls. Semi-automatic image analysis software was used to quantify intra-branch tapering (reduction in airway diameter along the branch), inter-branch tapering (reduction in airway diameter before and after bifurcation) and airway-artery ratios on chest CTs. Biomarkers were further stratified in small, medium and large airways based on three equal groups of the accompanying vessel size.

Results

Control subjects showed intra-branch tapering of 1% and inter-branch tapering of 24–39%. Subjects with bronchiectasis showed significantly reduced intra-branch of 0.8% and inter-branch tapering of 19–32% and increased airway–artery ratios compared with controls (p < 0.01). Tapering measurements were significantly different between diseased and controls across all airway sizes. Difference in airway–artery ratio was only significant in small airways.

Conclusion

Paediatric normal values for airway tapering were established in control subjects. Tapering showed to be a promising biomarker for bronchiectasis as subjects with bronchiectasis show significantly less airway tapering across all airway sizes compared with controls. Detecting less tapering in larger airways could potentially lead to earlier diagnosis of bronchiectasis. Additionally, compared with the conventional airway–artery ratio, this novel biomarker has the advantage that it does not require pairing with pulmonary arteries.

Key Points

• Tapering is a promising objective image biomarker for bronchiectasis that can be extracted semi-automatically and has good correlation with validated visual scoring methods.

• Less airway tapering was observed in patients with bronchiectasis and can be observed sensitively throughout the bronchial tree, even in the more central airways.

• Tapering values seemed to be less influenced by variety in scanning protocols and lung volume making it a more robust biomarker for bronchiectasis detection.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06606-w) contains supplementary material, which is available to authorized users.

PET/MRI attenuation estimation in the lung: A review of past, present, and potential techniques

Positron emission tomography/magnetic resonance imaging (PET/MRI) potentially offers several advantages over positron emission tomography/computed tomography (PET/CT), for example, no CT radiation dose and soft tissue images from MR acquired at the same time as the PET. However, obtaining accurate linear attenuation correction (LAC) factors for the lung remains difficult in PET/MRI. LACs depend on electron density and in the lung, these vary significantly both within an individual and from person to person. Current commercial practice is to use a single‐valued population‐based lung LAC, and better estimation is needed to improve quantification. Given the under‐appreciation of lung attenuation estimation as an issue, the inaccuracy of PET quantification due to the use of single‐valued lung LACs, the unique challenges of lung estimation, and the emerging status of PET/MRI scanners in lung disease, a review is timely. This paper highlights past and present methods, categorizing them into segmentation, atlas/mapping, and emission‐based schemes. Potential strategies for future developments are also presented.

Lung visualisation on PET/MRI: implementing a protocol with a short echo-time and low flip-angle volumetric interpolated breath-hold examination sequence

AIM

To assess the diagnostic performance in detecting lung lesions of a short echo-time (TE) and low flip-angle (FA) volumetric interpolated breath-hold examination (VIBE) sequence included in the integrated positron-emission tomography (PET)/magnetic resonance imaging (MRI) protocol.

METHOD AND MATERIALS

Thirty-seven oncological patients who underwent computed tomography (CT) and PET/MRI, including both a dedicated short TE, low FA VIBE (modified VIBE) and a standard VIBE of the lung, were enrolled. Modified VIBE images were reviewed retrospectively and independently by three raters, to detect pulmonary nodules, parenchymal consolidation, and bands. Three other groups examined standard VIBE, PET, and CT images. MRI and PET findings were compared to CT using Krippendorff's alpha using patient-based and a lesion-based analysis. Krippendorff's alpha was calculated to assess the interobserver agreement among the three raters of the modified VIBE.

RESULTS

In the patient-based analysis (positivity ≥1 lesion), the comparison of modified VIBE with CT showed an alpha of 0.54 for nodules <6 mm (versus 0.41 for standard VIBE and 0.09 for PET) and an alpha of 0.88 for nodules ≥6 mm (versus 0.74 for standard VIBE and 0.42 for PET). On a lesion-based analysis (presence/absence of each lesion), modified VIBE compared to CT showed an alpha of0.58 for nodules <6 mm (versus 0.44 for standard VIBE and 0.09 for PET) and an alpha of 0.90 for nodules ≥6 mm (versus 0.79 for standard VIBE and 0.50 for PET). The alpha value for the interobserver agreement was 0.90 for nodules <6 mm, 0.91 for nodules ≥6 mm, 1.00 for consolidations, and 0.95 for bands in the patient-based analysis and 0.89, 0.93, 1.00, and 0.95 in the lesion-based analysis.

CONCLUSIONS

Modified VIBE proved to be reproducible, showed better accuracy than standard VIBE and PET, and very good concordance with CT in assessing lung nodules ≥6 mm, whereas the agreement was less satisfactory for smaller nodules.

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.

Non-contrast enhanced magnetic resonance imaging detects mosaic signal intensity in early cystic fibrosis lung disease

OBJECTIVES

To determine if morphological non-contrast enhanced magnetic resonance imaging (MRI) of the lung is sensitive to detect mosaic signal intensity in infants and preschool children with cystic fibrosis (CF).

MATERIALS AND METHODS

50 infant and preschool CF patients (mean age 3.5 ± 1.4y, range 0-6y) routinely underwent morphological (T2-weighted turbo-spin echo sequence with half-Fourier acquisition, HASTE) and contrast-enhanced 4D perfusion MRI (gradient echo sequence with parallel imaging and echo sharing, TWIST). MRI studies were independently scored by two readers blinded for patient age and clinical data (experienced Reader 1 = R1, inexperienced Reader 2 = R2). The extent of lung parenchyma signal abnormalities on HASTE was rated for each lobe from 0 (normal), 1 (<50% of lobe affected) to 2 (≥50% of lobe affected). Perfusion MRI was rated according to the previously established MRI score, and served as the standard of reference.

RESULTS

Inter-method agreement between MRI mosaic score and perfusion score was moderate with κ = 0.58 (confidence interval 0.45-0.71) for R1, and with κ = 0.59 (0.46-0.72) for R2. Bland-Altman analysis revealed a slight tendency of the mosaic score to underestimate perfusion abnormalities with a score bias of 0.48 for R1 and 0.46 for R2. Inter-reader agreement for mosaic score was substantial with κ = 0.71 (0.62-0.79), and a low bias of 0.02.

CONCLUSIONS

This study demonstrates that non-contrast enhanced MRI reliably detects mosaic signal intensity in infants and preschool children with CF, reflecting pulmonary blood volume distribution. It may thus be used as a surrogate for perfusion MRI if contrast material is contra-indicated or alternative techniques are not available.

Pulmonary quantitative CT imaging in focal and diffuse disease: current research and clinical applications

The frenetic development of imaging technology-both hardware and software-provides exceptional potential for investigation of the lung. In the last two decades, CT was exploited for detailed characterization of pulmonary structures and description of respiratory disease. The introduction of volumetric acquisition allowed increasingly sophisticated analysis of CT data by means of computerized algorithm, namely quantitative CT (QCT). Hundreds of thousands of CTs have been analysed for characterization of focal and diffuse disease of the lung. Several QCT metrics were developed and tested against clinical, functional and prognostic descriptors. Computer-aided detection of nodules, textural analysis of focal lesions, densitometric analysis and airway segmentation in obstructive pulmonary disease and textural analysis in interstitial lung disease are the major chapters of this discipline. The validation of QCT metrics for specific clinical and investigational needs prompted the translation of such metrics from research field to patient care. The present review summarizes the state of the art of QCT in both focal and diffuse lung disease, including a dedicated discussion about application of QCT metrics as parameters for clinical care and outcomes in clinical trials.

Ultrashort Echo-Time Magnetic Resonance Imaging Is a Sensitive Method for the Evaluation of Early Cystic Fibrosis Lung Disease

RATIONALE

Recent advancements that have been made in magnetic resonance imaging (MRI) improve our ability to assess pulmonary structure and function in patients with cystic fibrosis (CF). A nonionizing imaging modality that can be used as a serial monitoring tool throughout life can positively affect patient care and outcomes.

OBJECTIVES

To compare an ultrashort echo-time MRI method with computed tomography (CT) as a biomarker of lung structure abnormalities in young children with early CF lung disease.

METHODS

Eleven patients with CF (mean age, 31.8 ± 5.7 mo; median age, 33 mo; 7 male and 4 female) were imaged via CT and ultrashort echo-time MRI. Eleven healthy age-matched patients (mean age, 22.5 ± 10.2 mo; median age, 23 mo; 5 male and 6 female) were imaged via ultrashort echo-time MRI. CT scans of 13 additional patients obtained for clinical indications not affecting the heart or lungs and interpreted as normal provided a CT control group (mean age, 24.1 ± 11.7 mo; median age, 24 mo; 6 male and 7 female). Studies were scored by two experienced radiologists using a well-validated CF-specific scoring system for CF lung disease.

MEASUREMENTS AND MAIN RESULTS

Correlations between CT and ultrashort echo-time MRI scores of patients with CF were very strong, with P values ≤0.001 for bronchiectasis (r = 0.96) and overall score (r = 0.90), and moderately strong for bronchial wall thickening (r = 0.62, P = 0.043). MRI easily differentiated CF and control groups via a reader CF-specific scoring system.

CONCLUSIONS

Ultrashort echo-time MRI detected structural lung disease in very young patients with CF and provided imaging data that correlated well with CT. By quantifying early CF lung disease without using ionizing radiation, ultrashort echo-time MRI appears well suited for pediatric patients requiring longitudinal imaging for clinical care or research studies. Clinical Trial registered with www.clinicaltrials.gov (NCT01832519).

Quantitative assessment of airway dimensions in young children with cystic fibrosis lung disease using chest computed tomography

OBJECTIVE

To evaluate lung disease progression using airway and artery (AA) dimensions on chest CT over 2-year interval in young CF patients longitudinally and compare to disease controls cross-sectionally.

METHODS

Retrospective analysis of pressure controlled end-inspiratory CTs, 12 routine baseline (CT₁ ) and follow up (CT₂ ) from AREST CF cohort; 12 disease controls with normal CT. All visible AA-pairs were measured perpendicular to the airway axis. Inner and outer airway diameters and wall (outer-inner radius) thickness were divided by adjacent arteries to compute A_in A-, A_out A-, and A_WT A-ratios, respectively. Differences between CF and control data were assessed using mixed effects models predicting AA-ratios per segmental generation (SG). Power calculations were performed with 80% power and ɑ = 0.05.

RESULTS

CF, median age CT₁ 2 years; CT₂ 3.9 years, 5 males. Controls, median age 2.9 years, 10 males. Total of 4798 AA-pairs measured. Cross-sectionally: A_in A-ratio showed no difference between controls and CF CT₁ or CT₂ . A_out A-ratio was significantly higher in CF CT₁ (SG 2-4) and CT₂ (SG 2-5) compared to controls. A_WT A-ratio was increased for CF CT₁ (SG 1-5) and CT₂ (SG 2-6) compared to controls. CF longitudinally: A_in A-ratio was significantly higher at CT₂ compared to CT₁ . Increase in A_out A-ratio at CT₂ compared to CT₁ was visible in SG ≥4. Sample sizes of 21 and 58 would be necessary for 50% and 30% A_out A-ratio reductions, respectively, between CF CT₂ and controls.

CONCLUSION

AA-ratio differences were present in young CF patients relative to disease controls. A_out A-ratio as an objective parameter for bronchiectasis could reduce sample sizes for clinical trials.

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.

Imaging Bronchopulmonary Dysplasia-A Multimodality Update

Bronchopulmonary dysplasia is the most common form of infantile chronic lung disease and results in significant health-care expenditure. The roles of chest radiography and computed tomography (CT) are well documented but numerous recent advances in imaging technology have paved the way for newer imaging techniques including structural pulmonary assessment via lung magnetic resonance imaging (MRI), functional assessment via ventilation, and perfusion MRI and quantitative imaging techniques using both CT and MRI. New applications for ultrasound have also been suggested. With the increasing array of complex technologies available, it is becoming increasingly important to have a deeper knowledge of the technological advances of the past 5–10 years and particularly the limitations of some newer techniques currently undergoing intense research. This review article aims to cover the most salient advances relevant to BPD imaging, particularly advances within CT technology, postprocessing and quantitative CT; structural MRI assessment, ventilation and perfusion imaging using gas contrast agents and Fourier decomposition techniques and lung ultrasound.

Early Lung Disease in Infants and Preschool Children with Cystic Fibrosis. What Have We Learned and What Should We Do about It?

The past decade has seen significant advances in understanding of the pathogenesis and progression of lung disease in cystic fibrosis (CF). Pulmonary inflammation, infection, and structural lung damage manifest very early in life and are prevalent among preschool children and infants, often in the absence of symptoms or signs. Early childhood represents a pivotal period amenable to intervention strategies that could delay or prevent the onset of lung damage and alter the longer-term clinical trajectory for individuals with CF. This review summarizes what we have learned about early lung disease in children with CF and discusses the implications for future clinical practice and research.

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.

Chest imaging in cystic fibrosis studies: What counts, and can be counted?

BACKGROUND

The dawn of precision medicine and CFTR modulators require more detailed assessment of lung structure in cystic fibrosis (CF) clinical studies. Various imaging markers have emerged and are measurable, but clarity is needed to identify what markers should count for clinical studies. High-resolution chest computed tomography (CT) scoring has yielded sensitive markers for the study of CF disease progression. Once completed, CT scores from ongoing randomized controlled trials can be used to examine relationships between imaging endpoints and therapeutic effectiveness. Similarly, Magnetic Resonance Imaging (MRI) is in development to generate structural as well as functional markers.

RESULTS

The aim of this review is to characterize the role of currently available CT and MRI markers in clinical studies, and to discuss study design, data processing and statistical challenges unique to these endpoints in CF studies. Suggestions to overcome these challenges in CF studies are included.

CONCLUSIONS

To maximize the potential of CT and MRI markers in clinical studies and advance treatment of CF disease progression, efforts should be made to conduct longitudinal randomized controlled trials including these modalities, develop data repositories, promote standardization and conduct reproducible research.

[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.

Paediatric respiratory infections

Pulmonary infections remain a major cause of infant and child mortality worldwide and are responsible for a substantial burden of morbidity. During the 2015 European Respiratory Society International Congress in Amsterdam, some of the main findings from peer-reviewed articles addressing this topic that were published in the preceding 12 months were reviewed in a Paediatric Clinical Year in Review session. The following article highlights some of the insights provided by these articles into the complex interactions of the human host with the extensive and dynamic populations of microorganisms that call an individual "home".