Update on the application of chest computed tomography scanning to cystic fibrosis

Pilot study to determine whether reduced-dose photon-counting detector chest computed tomography can reliably display Brody II score imaging findings for children with cystic fibrosis at radiation doses that approximate radiographs

BACKGROUND

The Brody II score uses chest CT to guide therapeutic changes in children with cystic fibrosis; however, patients and providers are often reticent to undergo chest CT given concerns about radiation.

OBJECTIVE

We sought to determine the ability of a reduced-dose photon-counting detector (PCD) chest CT protocol to reproducibly display pulmonary disease severity using the Brody II score for children with cystic fibrosis (CF) scanned at radiation doses similar to those of a chest radiograph.

MATERIALS AND METHODS

Pediatric patients with CF underwent non-contrast reduced-dose chest PCD-CT. Volumetric inspiratory and expiratory scans were obtained without sedation or anesthesia. Three pediatric radiologists with Certificates of Added Qualification scored each scan on an ordinal scale and assigned a Brody II score to grade bronchiectasis, peribronchial thickening, parenchymal opacity, air trapping and mucus plugging. We report image-quality metrics using descriptive statistics. To calculate inter-rater agreement for Brody II scoring, we used the Krippendorff alpha and intraclass correlation coefficient (ICC).

RESULTS

Fifteen children with CF underwent reduced-dose PCD chest CT in both inspiration and expiration (mean age 8.9 years, range, 2.5-17.5 years; 4 girls). Mean volumetric CT dose index (CTDIvol) was 0.07 ± 0.03 mGy per scan. Mean effective dose was 0.12 ± 0.04 mSv for the total examination. All three readers graded spatial resolution and noise as interpretable on lung windows. The average Brody II score was 12.5 (range 4-19), with moderate inter-reader reliability (ICC of 0.61 [95% CI=0.27, 0.84]). Inter-rater reliability was moderate to substantial for bronchiectasis (0.52), peribronchial thickening (0.55), presence of opacity (0.62) and air trapping (0.70) and poor for mucus plugging (0.09).

CONCLUSION

Reduced-dose PCD-CT permits diagnostic image quality and reproducible identification of Brody II scoring imaging findings at radiation doses similar to those for chest radiography.

Assessment of early lung disease in young children with CF: A comparison between pressure-controlled and free-breathing chest computed tomography

BACKGROUND

Chest computed tomography (CT) in children with cystic fibrosis (CF) is sensitive in detecting early airways disease. The pressure-controlled CT-protocol combines a total lung capacity scan (TLC PC-CT) with a near functional residual capacity scan (FRC PC-CT) under general anesthesia, while another CT-protocol is acquired during free breathing (FB-CT) near functional residual capacity. The aim of this study was to evaluate the sensitivity in detecting airways disease of both protocols in two cohorts.

METHODS

Routine PC-CTs (Princess Margaret Children's Hospital) and FB-CTs (Erasmus MC-Sophia Children's Hospital) were retrospectively collected from CF children aged 2 to 6 years. Total airways disease (%disease), bronchiectasis (%Bx), and low attenuation regions (%LAR) were scored on CTs using the Perth-Rotterdam annotated grid morphometric analysis-CF method. The Wilcoxon signed-rank test was used for differences between TLC and FRC PC-CTs and the Wilcoxon rank-sum test for differences between FRC PC-CTs and FB-CTs.

RESULTS

Fifty patients with PC-CTs (21 male, aged 2.5-5.5 years) and 42 patients with FB-CTs (26 male, aged 2.3-6.8 years) were included. %Disease was higher on TLC PC-CTs compared with FRC PC-CTs (median 4.51 vs 2.49; P < .001). %Disease and %Bx were not significantly different between TLC PC-CTs and FB-CTs (median 4.51% vs 3.75%; P = .143 and 0.52% vs 0.57%; P = .849). %Disease, %Bx, and %LAR were not significantly different between FRC PC-CTs and FB-CTs (median 2.49% vs 3.75%; P = .055, 0.54% vs 0.57%; P = .797, and 2.49% vs 1.53%; P = .448).

CONCLUSIONS

Our data suggest that FRC PC-CTs are less sensitive than TLC PC-CTs and that FB-CTs have similar sensitivity to PC-CTs in detecting lung disease. FB-CTs seem to be a viable alternative for PC-CTs to track CF lung disease in young patients with CF.

Computed Tomography Findings of Bronchiectasis in Different Respiratory Phases Correlate with Pulmonary Function Test Data in Adults

OBJECTIVE

To investigate bronchiectasis variations in different computed tomography (CT) respiratory phases, and their correlation with pulmonary function test (PFT) data, in adults.

METHODS

Retrospective data analysis from 63 patients with bronchiectasis according to CT criteria selected from the institution database and for whom PFT data were also available. Bronchiectasis diameter was measured on inspiratory and expiratory phases. Its area and matched airway-vessel ratios in both phases were also calculated. Finally, PFT results were compared with radiological measurements.

RESULTS

Bronchiectatic airways were larger on inspiration than on expiration (mean cross-sectional area, 69.44 vs. 40.84 mm²; p < 0.05) as were airway-vessel ratios (2.1 vs. 1.4; p < 0.05). Cystic bronchiectasis cases showed the least variation in cross-sectional area (48%). Mean predicted values of forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were 81.5 and 77.2%, respectively, in the group in which bronchiectasis could not be identified on expiratory images, and 58.3 and 56.0%, respectively, in the other group (p < 0.05). Variation in bronchiectasis area was associated with poorer lung function (r = 0.32).

CONCLUSION

Bronchiectasis detection, diameter, and area varied significantly according to CT respiratory phase, with non-reducible bronchiectasis showing greater lung function impairment.

Validating chest MRI to detect and monitor cystic fibrosis lung disease in a pediatric cohort

BACKGROUND

Computed Tomography (CT) is the gold standard to assess bronchiectasis and trapped air in cystic fibrosis (CF) lung disease, but has the disadvantage of radiation exposure. Magnetic Resonance Imaging (MRI) is a radiation free alternative.

OBJECTIVE

To validate MRI as outcome measure by: correlating MRI scores for bronchiectasis and trapped air with clinical parameters, and by comparing those MRI scores with CT scores.

METHODS

In patients with CF (aged 5.6-17.4 years), MRI and CT were alternated annually during routine annual check-ups between July 2007 and January 2010. Twenty-three children had an MRI performed 1 year prior to CT, 34 children had a CT 1 year prior to MRI. Bronchiectasis and trapped air were scored using the CF-MRI and CF-CT scoring system. CF-MRI scores were correlated with clinical parameters: FEV1 , Pseudomonas aeruginosa, pulmonary exacerbations and patient-reported respiratory symptoms measured on the Cystic Fibrosis Questionnaire-Revised (CFQ-R), using Spearman's correlation coefficient. MRI and CT scores were compared using intra-class correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

Fifty-seven patients who had an MRI, CT and CFQ-R during the study period were included. CF-MRI bronchiectasis correlated with FEV1 , Pseudomonas aeruginosa, pulmonary exacerbations and patient-reported respiratory symptoms. CF-MRI trapped air only correlated with FEV1 and Pseudomonas aeruginosa. ICCs between MRI and CT bronchiectasis and trapped air were 0.41 and 0.35 respectively. MRI tended to overestimate bronchiectasis compared to CT.

CONCLUSION

The associations between CF-MRI scores and several important clinical parameters further contributes to the validation of MRI. MRI provides different information than CT.

Spanish consensus on the prevention and treatment of Pseudomonas aeruginosa bronchial infections in cystic fibrosis patients

Pseudomonas aeruginosa is the main pathogen in bronchopulmonary infections in cystic fibrosis (CF) patients. It can only be eradicated at early infection stages while reduction of its bacterial load is the therapeutic goal during chronic infection or exacerbations. Neonatal screening and pharmacokinetic/pharmacodynamic knowledge has modified the management of CF-patients. A culture based microbiological follow-up should be performed in patients with no infection with P.aeruginosa. At initial infection, inhaled colistin (0,5-2MU/tid), tobramycin (300mg/bid) or aztreonam (75mg/tid) with or without oral ciprofloxacin (15-20mg/kg/bid, 2-3weeks) are recommended. In chronic infections, treatment is based on continuous administration of colistin or with a 28-day on-off regimen with tobramycin or aztreonam. During mild-moderate exacerbations oral ciprofloxacin (2-3weeks) can be administered while serious exacerbations must be treated with intravenous combination therapy (beta-lactam with an aminoglycoside or a fluoroquinolone). Future studies will support antibiotic rotation and/or new combination therapies. Epidemiological measures are also recommended to avoid new P.aeruginosa infections and "patient-to-patient transmission" of this pathogen.

Tracking Lung Clearance Index and chest CT in mild cystic fibrosis lung disease over a period of three years

INTRODUCTION

Lung disease remains the main cause of morbidity and mortality in patients with Cystic Fibrosis (CF). To detect lung disease before clinical symptoms become apparent, sensitive tools are essential. Spirometry is used for monitoring, but the FEV1 remains frequently normal throughout childhood. The Lung Clearance Index (LCI) calculated from Multiple Breath Washout (MBW) was introduced at the CF centre Innsbruck in 2007 for assessing ventilation inhomogeneity in patients with mild lung disease. We hypothesized that LCIs in 2007 are of prognostic value for the presence or absence of structural lung changes in later years.

METHODS

Between 2007 and 2010 MBW, spirometry and ultra-low-dose HR-CT were prospectively tracked in 36 patients (6-53 years) with a mean FEV1 ≥ 80% predicted in 2007.

RESULTS

At study start the majority of patients had abnormal CT scores and LCI results. While CT and spirometry remained largely stable throughout the study, LCI results slightly improved but still correlated with CT scores in 2010. LCI results in 2007 correlated with CT scores in 2010 while FEV1 did not. In 86% the LCI value in 2007 was indicative for the presence or absence of structural lung changes in 2010.

CONCLUSION

The LCI is a sensitive tool for detecting and tracking pulmonary changes. Extended structural changes are unlikely if the LCI is normal. The LCI has the potential to be used for monitoring the progression of early CF lung disease and assessing the effect of treatment in both clinical care and research settings.

Sensitivity of Lung Clearance Index and chest computed tomography in early CF lung disease

It is widely accepted that CF lung disease starts before clinical symptoms become apparent or spirometry deteriorates. Computed chest tomography (CT) is the reference method for identifying structural changes in CF; however, radiation exposure limits its use as a monitoring tool. It has been suggested that the Lung Clearance Index (LCI) measured by Multiple Breath Washout (MBW) for assessing ventilation inhomogeneity is a more sensitive surrogate marker than spirometry allowing non-invasive monitoring of CF lung disease. The aim of this study was to prospectively investigate the diagnostic accuracy of the LCI in comparison to CT in CF patients with early lung disease and normal FEV(1) (>80% pred.). MBW and ultra-low-dose CT were performed in 34 patients (6-26 years). LCI was abnormal in 76.5% subjects. LCI and CT correlated significantly in 82.3%. LCI was related to presence and extent of structural lung changes observed on CT with a sensitivity of 88%. Diagnostic accuracy of the LCI for detecting CF lung disease in patients with normal FEV(1) was good when compared to CT. Results indicate that structural changes are unlikely if a normal LCI is measured. We speculate that serial measurements of the LCI for assessing ventilation inhomogeneity may help to identify early structural lung disease and help to reduce the individual cumulative radiation dose. The LCI may be a suitable surrogate marker for monitoring progression of CF lung disease and effect of treatment in both, clinical care and research settings.

Structural lung changes, lung function, and non-invasive inflammatory markers in cystic fibrosis

Cystic fibrosis (CF) lung disease is characterized by chronic airway inflammation and recurrent infections, resulting in (ir)reversible structural lung changes and a progressive decline in lung function. The objective of this study was to investigate the relationship between non-invasive inflammatory markers (IM) in exhaled breath condensate (EBC), lung function indices and structural lung changes, visualized by high resolution computed tomography (HRCT) scans in CF. In 34 CF patients, lung function indices (forced expiratory volume in 1 s, forced vital capacity [FVC], residual volume, and total lung capacity [TLC]) and non-invasive IM (exhaled nitric oxide, and condensate acidity, nitrate, nitrite, 8-isoprostane, hydrogen peroxide, interferon-gamma) were assessed. HRCT scans were scored in a standardized and validated way, a composite score and component scores were calculated. In general, the correlations between non-invasive IM and structural lung changes, and between IM and lung function were low (correlation coefficients <0.40). Patients with positive sputum Pseudomonas cultures had higher EBC nitrite levels and higher parenchymal HRCT subscores than patients with Pseudomonas-negative cultures (p < 0.05). Multiple linear regression models demonstrated that FVC was significantly predicted by hydrogen peroxide in EBC, and the scores of bronchiectasis and mosaic perfusion (Pearson correlation coefficient R = 0.78, p < 0.001). TLC was significantly predicted by 8-isoprostane, nitrate, hydrogen peroxide in EBC, and the mucous plugging subscore (R = 0.92, p < 0.01). Static and dynamic lung function indices in this CF group were predicted by the combination of non-invasive IM in EBC and structural lung changes on HRCT imaging. Future longitudinal studies should reveal whether non-invasive monitoring of airway inflammation in CF adds to better follow-up of patients.

Development and validation of automated 2D-3D bronchial airway matching to track changes in regional bronchial morphology using serial low-dose chest CT scans in children with chronic lung disease

To address potential concern for cumulative radiation exposure with serial spiral chest computed tomography (CT) scans in children with chronic lung disease, we developed an approach to match bronchial airways on low-dose spiral and low-dose high-resolution CT (HRCT) chest images to allow serial comparisons. An automated algorithm matches the position and orientation of bronchial airways obtained from HRCT slices with those in the spiral CT scan. To validate this algorithm, we compared manual matching vs automatic matching of bronchial airways in three pediatric patients. The mean absolute percentage difference between the manually matched spiral CT airway and the index HRCT airways were 9.4 ± 8.5% for the internal diameter measurements, 6.0 ± 4.1% for the outer diameter measurements, and 10.1 ± 9.3% for the wall thickness measurements. The mean absolute percentage difference between the automatically matched spiral CT airway measurements and index HRCT airway measurements were 9.2 ± 8.6% for the inner diameter, 5.8 ± 4.5% for the outer diameter, and 9.9 ± 9.5% for the wall thickness. The overall difference between manual and automated methods was 2.1 ± 1.2%, which was significantly less than the interuser variability of 5.1 ± 4.6% (p<0.05). Tests of equivalence had p<0.05, demonstrating no significant difference between the two methods. The time required for matching was significantly reduced in the automated method (p<0.01) and was as accurate as manual matching, allowing efficient comparison of airways obtained on low-dose spiral CT imaging with low-dose HRCT scans.

Cystic fibrosis: are volumetric ultra-low-dose expiratory CT scans sufficient for monitoring related lung disease?

PURPOSE

To assess whether chest computed tomography (CT) scores from ultra-low-dose end-expiratory scans alone could suffice for assessment of all cystic fibrosis (CF)-related structural lung abnormalities.

MATERIALS AND METHODS

In this institutional review board-approved study, 20 patients with CF aged 6-20 years (eight males, 12 females) underwent low-dose end-inspiratory CT and ultra-low-dose end-expiratory CT. Informed consent was obtained. Scans were randomized and scored by using the Brody-II CT scoring system to assess bronchiectasis, airway wall thickening, mucus plugging, and opacities. Scoring was performed by two observers who were blinded to patient identity and clinical information. Mean scores were used for all analyses. Statistical analysis included assessment of intra- and interobserver variability, calculation of intraclass correlation coefficients (ICCs), and Bland-Altman plots.

RESULTS

Median age was 12.6 years (range, 6.3-20.3 years), median forced expiratory volume in 1 second was 100% (range, 46%-127%) of the predicted value, and median forced vital capacity was 99% (range, 61%-123%) of the predicted value. Very good agreement was observed between end-inspiratory and end-expiratory CT scores for Brody-II total score (ICC = 0.96), bronchiectasis (ICC = 0.98), airway wall thickening (ICC = 0.94), mucus plugging (ICC = 0.96), and opacities (ICC = 0.90). Intra- and interobserver agreement were good to very good (ICC range, 0.70-0.98). Bland-Altman plots showed that differences in scores were independent of score magnitude.

CONCLUSION

In this pilot study, CT scores from end-expiratory and end-inspiratory CT match closely, suggesting that ultra-low-dose end-expiratory CT alone may be sufficient for monitoring CF-related lung disease. This would help reduce radiation dose for a single investigation by up to 75%.

Lung morphology assessment using MRI: a robust ultra-short TR/TE 2D steady state free precession sequence used in cystic fibrosis patients

To evaluate feasibility and diagnostic quality of ultra-short TR/TE two-dimensional (2D) steady state free precession (SSFP) MRI for cystic fibrosis (CF) patients. We performed lung MRI at 1.5 Tesla in 20 CF-patients (6-17 years, 12 males). Axial, coronal, and sagittal sections were acquired in inspiration and expiration with maximum breath-hold time 10 s. MR and CT images were scored using a modified Brody scoring system to assess bronchiectasis, mucous plugging, atelectasis/consolidations, and air trapping. All images were scored by two experienced observers. A complete MR investigation took maximally 15 min. Maximal breath-holds were only 10 s and well tolerated. MRI identified major bronchiectasis, mucous plugging and atelectasis. End-expiratory scans showed patches of parenchyma with reduced signal intensity that may corresponded to areas of trapped air on expiratory CT scans. This MRI protocol based on ultra-short TR/TE 2D SSFP is quick and well tolerated and provides highly relevant imaging features as seen on CT in CF patients. Most importantly, the SNR of the expiratory scans enables to visualize air trapping. The preliminary results of this study suggest MRI as a noteworthy additional imaging tool for routine monitoring of CF patients.

Early intervention in CF: how to monitor the effect

Early and aggressive therapy already at the stage when no apparent signs of significant lung disease are detectable, may delay the development and progression of cystic fibrosis (CF). Identification of markers for early pulmonary disease in CF is crucial to monitor adherence to preventive therapy and determine its success. Currently several surrogate markers are available that are used in both the decision making and evaluation of the timing and success of early intervention namely, pulmonary function tests (PFT), microbial cultures, imaging techniques, inflammatory markers, serological markers, and several general signs such as exacerbation rate and nutritional status. This review will present the current status and discuss the significance of their application as well as their limitations for patients with CF and no apparent pulmonary disease.

Imaging of the Chest in Cystic Fibrosis

In the last 2 decades significant strides have been made in the application of chest imaging modalities to assess cystic fibrosis (CF) lung disease. This article covers current chest imaging modalities. It discusses CT, the research modality most commonly used to assess lung disease in CF, new insights regarding CF lung disease, and future directions in research and clinical care.