Dose reduction for CT in children with cystic fibrosis: is it feasible to reduce the number of images per scan?

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.

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.

The impact of slice-reduced computed tomography on histogram-based densitometry assessment of lung fibrosis in patients with systemic sclerosis

Background

To evaluate usability of slice-reduced sequential computed tomography (CT) compared to standard high-resolution CT (HRCT) in patients with systemic sclerosis (SSc) for qualitative and quantitative assessment of interstitial lung disease (ILD) with respect to (I) detection of lung parenchymal abnormalities, (II) qualitative and semiquantitative visual assessment, (III) quantification of ILD by histograms and (IV) accuracy for the 20%-cut off discrimination.

Methods

From standard chest HRCT of 60 SSc patients sequential 9-slice-computed tomography (reduced HRCT) was retrospectively reconstructed. ILD was assessed by visual scoring and quantitative histogram parameters. Results from standard and reduced HRCT were compared using non-parametric tests and analysed by univariate linear regression analyses.

Results

With respect to the detection of parenchymal abnormalities, only the detection of intrapulmonary bronchiectasis was significantly lower in reduced HRCT compared to standard HRCT (P=0.039). No differences were found comparing visual scores for fibrosis severity and extension from standard and reduced HRCT (P=0.051-0.073). All scores correlated significantly (P<0.001) to histogram parameters derived from both, standard and reduced HRCT. Significant higher values of kurtosis and skewness for reduced HRCT were found (both P<0.001). In contrast to standard HRCT histogram parameters from reduced HRCT showed significant discrimination at cut-off 20% fibrosis (sensitivity 88% kurtosis and skewness; specificity 81% kurtosis and 86% skewness; cut-off kurtosis ≤26, cut-off skewness ≤4; both P<0.001).

Conclusions

Reduced HRCT is a robust method to assess lung fibrosis in SSc with minimal radiation dose with no difference in scoring assessment of lung fibrosis severity and extension in comparison to standard HRCT. In contrast to standard HRCT histogram parameters derived from the approach of reduced HRCT could discriminate at a threshold of 20% lung fibrosis with high sensitivity and specificity. Hence it might be used to detect early disease progression of lung fibrosis in context of monitoring and treatment of SSc patients.

Clinical indications and scanning protocols for chest CT in children with cystic fibrosis: a survey of UK tertiary centres

OBJECTIVES

Chest CT is increasingly used to monitor disease progression in children with cystic fibrosis (CF) but there is no national guideline regarding its use. Our objective was to assess the indications for undertaking chest CT and the protocols used to obtain scans.

DESIGN SETTING AND PARTICIPANTS

An electronic questionnaire was developed to assess clinicians views on chest CT in children with CF. It included general questions on perceived benefits and specific questions about its role in five clinical scenarios. It was sent to the clinical lead in 27 UK paediatric CF centres. A separate questionnaire was developed to collect the technical details of chest CT in children with CF. It was sent to the superintendent radiographer at each of the 27 centres.

RESULTS

Responses were obtained from 27 (100%) clinical leads and 22 (81%) superintendent radiographers. 93% clinicians reported chest CT useful in monitoring disease progression and 70% said it frequently altered management. Only 5 (19%) undertook routine scans. To aid diagnosis, 81% performed chest CT in non-tuberculous mycobacterial disease and 15% in allergic bronchopulmonary aspergillosis. There was wide variation in the perceived need for and/or timing of chest CT in children with reduced lung function with no benefit from intravenous antibiotics, new cystic changes on chest X-ray, and lobar collapse. The radiographers reported using a mixture of helical (volumetric) and axial scans depending on the clinical question, the age and the cooperation of the child. When indicated, 6 (27%) used sedation and 16 (73%) general anaesthetic. Only 1 (5%) used intravenous contrast routinely and 3 (14%) obtained expiratory images routinely.

CONCLUSIONS

There is marked variation in the use of chest CT in children with CF and in the scan protocols. The lack of a national guideline is likely to be contributing to this lack of standardisation.

Exercise responses are related to structural lung damage in CF pulmonary disease

INTRODUCTION

Early detection of lung disease is a primary objective in monitoring patients with Cystic Fibrosis (CF); High-Resolution-Computed-Tomography (HRCT) assesses structural damage. Spirometry and cardiopulmonary exercise testing are used for functional evaluation of CF lung disease.

AIM

To evaluate the deterioration of exercise testing parameters over a 2-year period compared to the change of spirometry and HRCT parameters among CF patients.

METHODS

Twenty-eight CF patients were evaluated with HRCT, spirometry, and exercise testing; 15 had two assessments with an interval of 2 years. Correlation analyses between Bhalla score parameters and functional measures were performed.

RESULTS

Twenty-eight patients with CF (mean age 14.9 years, mean forced expiratory volume in 1 sec [FEV1 ] 83.2%) were evaluated. FEV1 was not found to change significantly in the 2-year period (P = 0.612). Both mean Bhalla score and mean peak oxygen consumption (VO2 peak %) deteriorated significantly (P = 0.014 and P = 0.026, respectively). VO2 peak and respiratory equivalents for O2 and CO2 at peak exercise were found to be significant predictors of Bhalla score (r = -0.477, P = 0.010; r = 0.461, P = 0.018; r = 0.402; P = 0.042, respectively). Anaerobic threshold was associated with changes in Bhalla score over the following 2 years.

CONCLUSIONS

Exercise testing is more sensitive than spirometry to detect structural changes in CF lungs. Pediatr Pulmonol. 2016; 51:914-920. © 2016 Wiley Periodicals, Inc.

Multicentre chest computed tomography standardisation in children and adolescents with cystic fibrosis: the way forward

Progressive cystic fibrosis (CF) lung disease is the main cause of mortality in CF patients. CF lung disease starts in early childhood. With current standards of care, respiratory function remains largely normal in children and more sensitive outcome measures are needed to monitor early CF lung disease. Chest CT is currently the most sensitive imaging modality to monitor pulmonary structural changes in children and adolescents with CF. To quantify structural lung disease reliably among multiple centres, standardisation of chest CT protocols is needed. SCIFI CF (Standardised Chest Imaging Framework for Interventions and Personalised Medicine in CF) was founded to characterise chest CT image quality and radiation doses among 16 participating European CF centres in 10 different countries. We aimed to optimise CT protocols in children and adolescents among several CF centres. A large variety was found in CT protocols, image quality and radiation dose usage among the centres. However, the performance of all CT scanners was found to be very similar, when taking spatial resolution and radiation dose into account. We conclude that multicentre standardisation of chest CT in children and adolescents with CF can be achieved for future clinical trials.

What did we learn from two decades of chest computed tomography in cystic fibrosis?

Despite our current treatment, many cystic fibrosis (CF) patients still show progressive bronchiectasis and small airways disease. Adequate detection and monitoring of progression of these structural abnormalities is needed to personalize treatment to the severity of CF lung disease of the patient. Chest computed tomography (CT) is the gold standard to diagnose and monitor bronchiectasis. Many studies have been done to validate the role of chest CT in CF and to improve the protocols. From these studies it became clear that for correct interpretation of the severity of bronchiectasis and small airways disease standardization of lung volume for the inspiratory and expiratory CT scan acquisition is needed. The risk related to the radiation exposure of a chest CT scan every second year is considered low. Automated and quantitative image analysis systems are developed to improve the reliability and sensitivity of assessments of structural lung changes in CF, particularly in early life. In this paper an overview is given of the lessons learned from two decades of monitoring CF lung disease using chest CT.

Multi-modality monitoring of cystic fibrosis lung disease: the role of chest computed tomography

Cystic fibrosis [CF] lung disease is characterized by progressive bronchiectasis and small airways disease. To monitor CF lung disease traditionally spirometry has been the most important modality. In addition to spirometry chest radiography was used to monitor progression of structural lung abnormalities. However, the importance of chest radiography in disease management has been limited due to its poor sensitivity and specificity to detect disease progression. Over the last decade chest CT has become the gold standard for monitoring the severity and progression of bronchiectasis. Small airways disease can be monitored using spirometry, multiple breath washout techniques, and chest CT. In modern CF-care a multi-modality approach is needed to monitor CF lung disease and to personalize treatment for the needs of the patient. When state-of-the-art low dose bi-annual chest CT protocols are used radiation risk is considered to be low. In between chest CT imaging, physiologic measures are important to obtain for monitoring. Stratification of monitoring protocols based on the risk profile of the patient can help us in the future to better care for people with CF.

Is chest CT useful in newborn screened infants with cystic fibrosis at 1 year of age?

Rationale

Sensitive outcome measures applicable in different centres to quantify and track early pulmonary abnormalities in infants with cystic fibrosis (CF) are needed both for clinical care and interventional trials. Chest CT has been advocated as such a measure yet there is no validated scoring system in infants.

Objectives

The objectives of this study were to standardise CT data collection across multiple sites; ascertain the incidence of bronchial dilatation and air trapping in newborn screened (NBS) infants with CF at 1 year; and assess the reproducibility of Brody-II, the most widely used scoring system in children with CF, during infancy.

Methods

A multicentre observational study of early pulmonary lung disease in NBS infants with CF at age 1 year using volume-controlled chest CT performed under general anaesthetic.

Main results

65 infants with NBS-diagnosed CF had chest CT in three centres. Small insignificant variations in lung recruitment manoeuvres but significant centre differences in radiation exposures were found. Despite experienced scorers and prior training, with the exception of air trapping, inter- and intraobserver agreement on Brody-II score was poor to fair (eg, interobserver total score mean (95% CI) κ coefficient: 0.34 (0.20 to 0.49)). Only 7 (11%) infants had a total CT score ≥12 (ie, ≥5% maximum possible) by either scorer.

Conclusions

In NBS infants with CF, CT changes were very mild at 1 year, and assessment of air trapping was the only reproducible outcome. CT is thus of questionable value in infants of this age, unless an improved scoring system for use in mild CF disease can be developed.

Novel end points for clinical trials in young children with cystic fibrosis

Cystic fibrosis (CF) lung disease commences early in the disease progression and is the most common cause of mortality. While new CF disease-modifying agents are currently undergoing clinical trial evaluation, the implementation of such trials in young children is limited by the lack of age-appropriate clinical trial end points. Advances in infant and preschool lung function testing, imaging of the chest and the development of biochemical biomarkers have led to increased possibility of quantifying mild lung disease in young children with CF and objectively monitoring disease progression over the course of an intervention. Despite this, further standardization and development of these techniques is required to provide robust objective measures for clinical trials in this age group.

Image analysis for cystic fibrosis: computer-assisted airway wall and vessel measurements from low-dose, limited scan lung CT images

Cystic fibrosis (CF) is a life-limiting genetic disease that affects approximately 30,000 Americans. When compared to those of normal children, airways of infants and young children with CF have thicker walls and are more dilated in high-resolution computed tomographic (CT) imaging. In this study, we develop computer-assisted methods for assessment of airway and vessel dimensions from axial, limited scan CT lung images acquired at low pediatric radiation doses. Two methods (threshold- and model-based) were developed to automatically measure airway and vessel sizes for pairs identified by a user. These methods were evaluated on chest CT images from 16 pediatric patients (eight infants and eight children) with different stages of mild CF related lung disease. Results of threshold-based, corrected with regression analysis, and model-based approaches correlated well with both electronic caliper measurements made by experienced observers and spirometric measurements of lung function. While the model-based approach results correlated slightly better with the human measurements than those of the threshold method, a hybrid method, combining these two methods, resulted in the best results.

Screening for interstitial lung disease in systemic sclerosis: the diagnostic accuracy of HRCT image series with high increment and reduced number of slices

OBJECTIVES

The objective of this study is to assess diagnostic accuracy for the detection of interstitial lung disease (ILD) in image series with high increment and reduced number of slices in patients with systemic sclerosis (SSc).

METHODS

45 patients with SSc underwent high-resolution CT (HRCT). Three series of secondary captures were reconstructed as follows: series 1, series with 10 mm increment and 1 mm slices; series 2, seven axial images with baso-apical gradient; series 3, three axial images were obtained at the apical, at the level of the carina and basal. The presence and extent of ILD, and the degree of diagnostic confidence were recorded. The effective dose for each image series was estimated. Standard HRCT was the standard of reference.

RESULTS

The prevalence of ILD was 55% (25/45). Diagnostic sensitivity and accuracy of series 1, series 2 and series 3 were 100% and 94.4%, 94% and 97.8%, 92% and 97.8%, respectively. The extent of ILD was underestimated in series 3 (p<0.05) and was comparable to the standard HRCT in series 1 and 2 (p>0.05). Estimated dose reduction was more than 90% in all image series.

CONCLUSIONS

HRCT image series with low sampling rate allow an accurate detection of ILD with very-low-radiation dose, making this approach potentially valuable for screening in patients with SSc.

Paediatric multi-detector row chest CT: what you really need to know

Background

The emergence of multi-detector row CT (MDCT) has established and extended the role of CT especially in paediatric chest imaging. This has altered the way in which data is acquired and is perceived as the 'gold standard' in the detection of certain chest pathologies. The range of available post-processing tools provide alternative ways in which CT images can be manipulated for review and interpretation in order to enhance diagnostic accuracy.

Methodology

Paediatric imaging technique/protocol together with radiation dose reduction is discussed in detail. The use of different post-processing tools to best demonstrate the wide range of important congenital anomalies and thoracic pathologies is outlined and presented pictorially.

Conclusion

MDCT with its isotropic resolution and fast imaging acquisition times reduces the need for invasive diagnostic investigations. However, users must be vigilant in their imaging techniques to minimise radiation burden, whilst maintaining good image quality.

Main Messages

• CT examinations should be clinically justified by the referring clinician and radiologist.

• MDCT is invaluable for evaluating the central airway, mediastinal structures and lung parenchyma.

• MDCT is more sensitive than plain radiographs in detection of structural changes within the lungs.

Radiologic imaging in cystic fibrosis: cumulative effective dose and changing trends over 2 decades

OBJECTIVE

With the increasing life expectancy for patients with cystic fibrosis (CF), and a known predisposition to certain cancers, cumulative radiation exposure from radiologic imaging is of increasing significance. This study explores the estimated cumulative effective radiation dose over a 17-year period from radiologic procedures and changing trends of imaging modalities over this period.

METHODS

Estimated cumulative effective dose (CED) from all thoracic and extrathoracic imaging modalities and interventional radiology procedures for both adult and pediatric patients with CF, exclusively attending a nationally designated CF center between 1992-2009 for > 1 year, was determined. The study period was divided into three equal tertiles, and estimated CED attributable to all radiologic procedures was estimated for each tertile.

RESULTS

Two hundred thirty patients met inclusion criteria (2,240 person-years of follow-up; 5,596 radiologic procedures). CED was > 75 mSv for one patient (0.43%), 36 patients (15.6%) had a CED between 20 and 75 mSv, 56 patients (24.3%) had a CED between 5 and 20 mSv, and in 138 patients (60%) the CED was estimated to be between 0 and 5 mSv over the study period. The mean annual CED per patient increased consecutively from 0.39 mSv/y to 0.47 mSv/y to 1.67 mSv/y over the tertiles one to three of the study period, respectively (P < .001). Thoracic imaging accounted for 46.9% of the total CED and abdominopelvic imaging accounted for 42.9% of the CED, respectively. There was an associated 5.9-fold increase in the use of all CT scanning per patient (P < .001).

CONCLUSIONS

This study highlights the increasing exposure to ionizing radiation to patients with CF as a result of diagnostic imaging, primarily attributable to CT scanning. Increased awareness of CED and strategies to reduce this exposure are needed.

Using hyperpolarized 3He MRI to evaluate treatment efficacy in cystic fibrosis patients

PURPOSE

To use hyperpolarized (HP) (3)He MR imaging to assess functional lung ventilation in subjects with cystic fibrosis (CF) before and after treatment.

MATERIALS AND METHODS

We performed HP (3)He static ventilation MRI scans on three subjects, using a Philips 3.0 Tesla (T) Achieva MRI scanner, before and after 11 days of in-patient treatment with combined intravenous and inhaled therapies for pulmonary exacerbations of CF. We also collected spirometry data. We quantified pulmonary ventilation volume measured with HP (3)He MRI using an advanced semi-automated analysis technique.

RESULTS

Following 11 days of treatment with intravenous antibiotics, hypertonic saline, and rhDNase, HP (3)He MR images in one subject displayed a 25% increase in total ventilation volume. Total ventilation volume in the other two subjects slightly decreased. All three subjects showed increases in FEV(1) and FVC following treatment.

CONCLUSION

In all subjects, the HP (3)He MR images provided detailed information on precisely where in the lungs gas was reaching. These data provide additional support for the conclusion that HP noble gas MRI can be a powerful tool for evaluating lung ventilation in patients with cystic fibrosis, but also raise important questions about the correlation between spirometry and HP gas MRI measurements.

Air trapping on chest CT is associated with worse ventilation distribution in infants with cystic fibrosis diagnosed following newborn screening

BACKGROUND

In school-aged children with cystic fibrosis (CF) structural lung damage assessed using chest CT is associated with abnormal ventilation distribution. The primary objective of this analysis was to determine the relationships between ventilation distribution outcomes and the presence and extent of structural damage as assessed by chest CT in infants and young children with CF.

METHODS

Data of infants and young children with CF diagnosed following newborn screening consecutively reviewed between August 2005 and December 2009 were analysed. Ventilation distribution (lung clearance index and the first and second moment ratios [LCI, M(1)/M(0) and M(2)/M(0), respectively]), chest CT and airway pathology from bronchoalveolar lavage were determined at diagnosis and then annually. The chest CT scans were evaluated for the presence or absence of bronchiectasis and air trapping.

RESULTS

Matched lung function, chest CT and pathology outcomes were available in 49 infants (31 male) with bronchiectasis and air trapping present in 13 (27%) and 24 (49%) infants, respectively. The presence of bronchiectasis or air trapping was associated with increased M(2)/M(0) but not LCI or M(1)/M(0). There was a weak, but statistically significant association between the extent of air trapping and all ventilation distribution outcomes.

CONCLUSION

These findings suggest that in early CF lung disease there are weak associations between ventilation distribution and lung damage from chest CT. These finding are in contrast to those reported in older children. These findings suggest that assessments of LCI could not be used to replace a chest CT scan for the assessment of structural lung disease in the first two years of life. Further research in which both MBW and chest CT outcomes are obtained is required to assess the role of ventilation distribution in tracking the progression of lung damage in infants with CF.

Computed tomography and magnetic resonance imaging in cystic fibrosis lung disease

Computed tomography (CT) is the current "gold standard" for assessment of lung morphology and is so far the most reliable imaging modality for monitoring cystic fibrosis (CF) lung disease. CT has a much higher radiation exposure than chest x-ray. The cumulative radiation dose for life-long repeated CT scans has limited its use for CF patients as their life expectancy increases. Clearly, no dose would be preferable over low dose when the same or more relevant information can be obtained. Magnetic resonance imaging (MRI) is comparable to CT with regard to the detection of most morphological changes in the CF lung. It is thought to be less sensitive to detect small airway disease. At the same time, MRI is superior to CT when it comes to the assessment of functional changes such as altered pulmonary perfusion. The recommendation is to further reduce radiation dose related to the use of CT and to use MRI in the follow-up of morphological changes where possible.

The role of advanced imaging techniques in cystic fibrosis follow-up: is there a place for MRI?

Cystic fibrosis (CF) lung disease is caused by mutations in the CFTR-gene and remains one of the most frequent lethal inherited diseases in the Caucasian population. Given the progress in CF therapy and the consecutive improvement in prognosis, monitoring of disease progression and effectiveness of therapeutic interventions with repeated imaging of the CF lung plays an increasingly important role. So far, the chest radiograph has been the most widely used imaging modality to monitor morphological changes in the CF lung. CT is the gold standard for assessment of morphological changes of airways and lung parenchyma. Considering the necessity of life-long repeated imaging studies, the cumulative radiation doses reached with CT is problematic for CF patients. A sensitive, non-invasive and quantitative technique without radiation exposure is warranted for monitoring of disease activity. In previous studies, MRI proved to be comparable to CT regarding the detection of morphological changes in the CF lung without using ionising radiation. Furthermore, MRI was shown to be superior to CT regarding assessment of functional changes of the lung. This review presents the typical morphological and functional MR imaging findings with respect to MR-based follow-up of CF lung disease. MRI offers a variety of techniques for morphological and functional imaging of the CF lung. Using this radiation free technique short- and long-term follow-up studies are possible enabling an individualised guidance of the therapy.

The use of high resolution computerized tomography (HRCT) of the chest in evaluating the effect of tobramycin solution for inhalation in cystic fibrosis lung disease

OBJECTIVES

To compare the usefulness of HRCT of the chest versus spirometric measures (PFTs) in evaluating the effect of tobramycin solution for inhalation (TSI) in cystic fibrosis (CF).

METHODS

Thirty-two CF patients with mostly mild lung disease age > or = 6 years, were enrolled in a double-blind, placebo-controlled pilot study. Patients were chronically colonized with Pseudomonas aeruginosa for at least 6 months prior to and at enrollment. If patients were on TSI, they were taken off for at least 3 months prior to enrollment. Duration was 6 months; 31 subjects completed the study. HRCT and PFTs were evaluated at baseline, after 28 days of treatment and at the end of the study. Study medication was administered as 5 ml nebulized treatment twice a day for 28 days followed by 28 days off (one cycle). Study consisted of three cycles. Two radiologists scored all films using a validated system. A total HRCT score consists of the sum of subscores: linear opacities, hyperinflation, nodular opacities, peribronchial thickening, mucous plugging, and bronchiectasis; each subscore could range from 0 to 80, with potential total scores varying from 0 to 480. The percent of the maximum possible HRCT score was then calculated and used for all comparisons.

RESULTS

Using two tailed paired t-test, the percent maximum HRCT score decreased by 1.4 +/- 2.6% (mean +/- SD) (P = 0.049) and 0.3 +/- 2.8% (P = 0.63) for the TSI group and decreased by 0.1 +/- 1.5% (P = 0.74) and increased by 0.6 +/- 1.8% (P = 0.23) for the placebo group between visits 1 and 2, and visits 1 and 3, respectively. The data were then analyzed using a mixed model utilizing changes in scores over the durations of the study for each group. The change of HRCT score for the TSI group was -0.24/day (P = 0.02) and -0.03/day (P = 0.22), and for the control group the change was -0.01 (P = 0.93) and 0.02 (P = 0.29) between visits 1 and 2, and visits 1 and 3 respectively. FEF(25-75)% and FEV(1)% changes were not statistically significant using both analyses.

CONCLUSION

HRCT seems to be more sensitive in detecting treatment effect than PFT in CF patients with mild lung disease, especially following the first treatment period (visit 2). Total HRCT score showed some improvement at the end of the study, though not statistically significant. This is probably due to obtaining the HRCT an average of 30 days after completion of the TSI treatment, and selection of study population with mostly mild lung disease. This could indicate that the most significant improvement in the total HRCT score in this patient population occurs after the first treatment period with TSI.

A CT scan score for the assessment of lung disease in children with common variable immunodeficiency disorders

BACKGROUND

The prevalence and severity of structural lung disease in children with common variable immunodeficiency (CVID) disorders is not well known, and a dedicated CT scanning protocol and CT scan scoring system have not been described in this category.

METHODS

This was a cohort study of 54 children (34 CVID, 20 CVID-like disorder) in a stable condition who underwent volumetric inspiratory and end-expiratory CT scans. Scans were scored for airway abnormalities, interstitial and parenchymal lung disease, and lymphadenopathy using a newly developed CT scan scoring system. Scores were normalized to a 0% to 100% scale. Observer agreement was assessed using an intraclass correlation coefficient (Ri). Prevalence and severity of CT scan abnormalities were calculated.

RESULTS

Structural lung disease was common (85%-93%), but usually mild as reflected in the relatively low scores (bronchiectasis score 2.8% +/- 6.4%). Moderate-to-severe bronchiectasis was found in three (5%) patients. Expiratory air trapping was the most common finding, found in 71% to 80%, but often in a mild form; application of a cut off level of > 10% reduced its prevalence to 33% to 38%. In 9% to 15% of all patients, air trapping was the only abnormality. Multiple lung nodules were seen in 24% to 25% and could disappear after corticosteroid treatment. Observer agreement was moderate (Ri 0.6-0.79) to good (Ri > 0.8) for all items and the composite scores, except airway wall thickening.

CONCLUSION

In children with CVID disorders, mild structural lung disease is common. Expiratory CT scans show the most frequent abnormality, air trapping. The occurrence of (silent) lung disease progression and the clinical impact of CT scans require further investigations.

Imaging of Childhood Interstitial Lung Disease

The aphorism that children are not little adults certainly applies for the imaging of interstitial lung disease. Acquiring motion-free images of fine pulmonary structures at desired lung volumes is much more difficult in children than in adults. Several forms of interstitial lung disease are unique to children, and some forms of interstitial lung disease encountered in adults rarely, if ever, occur in children. Meticulous attention to imaging technique and specialized knowledge are required to properly perform and interpret chest imaging studies obtained for the evaluation of childhood interstitial lung disease (chILD). This review will address technique recommendations for imaging chILD, the salient imaging findings in various forms of chILD, and the efficacy of imaging in the diagnosis and management of chILD.

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%.

Dose reduction and compliance with pediatric CT protocols adapted to patient size, clinical indication, and number of prior studies

PURPOSE

To assess compliance and resultant radiation dose reduction with new pediatric chest and abdominal computed tomographic (CT) protocols based on patient weight, clinical indication, number of prior CT studies, and automatic exposure control.

MATERIALS AND METHODS

The study was institutional review board approved and HIPAA compliant. Informed consent was waived. The new pediatric CT protocols, which were organized into six color zones based on clinical indications and number of prior CT examinations in a given patient, were retrospectively assessed. Scanning parameters were adjusted on the basis of patient weight. For gradual dose reduction, pediatric CT (n = 692) examinations were performed in three phases of incremental stepwise dose reduction during a 17-month period. There were 245 male patients and 193 female patients (mean age, 12.6 years). Two radiologists independently reviewed CT images for image quality. Data were analyzed by using multivariate analysis of variance.

RESULTS

Compliance with the new protocols in the early stage of implementation (chest CT, 58.9%; abdominal CT, 65.2%) was lower than in the later stage (chest CT, 88%; abdominal CT, 82%) (P < .001). For chest CT, there was 52.6% (9.1 vs 19.2 mGy) to 85.4% (2.8 vs 19.2 mGy) dose reduction in the early stage of implementation and 73.5% (4.9 vs 18.5 mGy) to 83.2% (3.1 vs 18.5 mGy) dose reduction in the later stages compared with dose at noncompliant examinations (P < .001); there was no loss of clinically relevant image quality. For abdominal CT, there was 34.3% (9.0 vs 13.7 mGy) to 80.2% (2.7 vs 13.7 mGy) dose reduction in the early stage of implementation and 62.4% (6.5 vs 17.3) to 83.8% (2.8 vs 17.3 mGy) dose reduction in the later stage (P < .001).

CONCLUSION

Substantial dose reduction and high compliance can be obtained with pediatric CT protocols tailored to clinical indications, patient weight, and number of prior studies.

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.

Sampling density for the quantitative evaluation of air trapping

BACKGROUND

Concerns have been expressed recently about the radiation burden on patient populations, especially children, undergoing serial radiological testing. To reduce the dose one can change the CT acquisition settings or decrease the sampling density.

OBJECTIVE

In this study we determined the minimum desirable sampling density to ascertain the degree of air trapping in children with cystic fibrosis.

MATERIALS AND METHODS

Ten children with cystic fibrosis in stable condition underwent a volumetric spiral CT scan. The degree of air trapping was determined by an automated algorithm for all slices in the volume, and then for 1/2, 1/4, to 1/128 of all slices, or a sampling density ranging from 100% to 1% of the total volume. The variation around the true value derived from 100% sampling was determined for all other sampling densities.

RESULTS

The precision of the measurement remained stable down to a 10% sampling density, but decreased markedly below 3.4%.

CONCLUSION

For a disease marker with the regional variability of air trapping in cystic fibrosis, regardless of observer variability, a sampling density below 10% and even more so, below 3.4%, apparently decreases the precision of the evaluation.

Lung structure and function of infants with recurrent wheeze when asymptomatic

Infants with recurrent wheeze have repeated episodes of airways obstruction; however, relatively little is known about the structure and function of their lungs when not symptomatic. The current authors evaluated whether infants with recurrent wheeze have smaller airway lumens or thickened airway walls, as well as decreased airway function. High-resolution computed tomography images 1 mm thick were obtained at three anatomic locations at an elevated lung volume and at functional residual capacity. Forced expiratory flows were also measured in subjects with recurrent wheeze. Airway lumen, wall areas and lung tissue density were not significantly different for recurrent wheeze (n = 17) and control (n = 14) subjects; however, subjects with recurrent wheeze had lower forced expiratory flows than predicted. Similar findings were obtained when subjects were grouped by exposure to tobacco smoke. These findings indicate that infants with recurrent wheeze, as well as exposure to tobacco smoke, have lower airway function when not symptomatic. The lower forced expiratory flows may result from a degree of airway narrowing that could not be resolved with the methodology employed or from other mechanisms, such as more collapsible airways or decreased pulmonary elastic recoil.

Clinical trials in infants with cystic fibrosis detected following newborn screening

Despite the wide implementation of newborn screening for cystic fibrosis there have been few clinical trials aimed at reducing the burden of lung disease in screened infants. Emerging tools such as infant lung function and low-dose computed tomography (CT) provide early indicators of lung disease and could be effective outcome measures in randomized controlled trials (RCTs) of interventions that aim to delay or prevent the onset of bronchiectasis. The most recent data suggest that strategies to reduce neutrophilic inflammation and prevent infection are good candidates for RCTs. However, cooperation between centres is needed if they are to be large enough to detect differences due to the intervention that otherwise may be masked by subtle differences in management practices between centres, and to detect rare but significant adverse effects.

Role of high-resolution computed tomography in the detection of early cystic fibrosis lung disease

High-resolution computed tomography (HRCT) has been demonstrated to be sensitive at detecting early lung disease in cystic fibrosis (CF), often before it is apparent clinically. There is emerging evidence that structural changes in the lung occur earlier in life than previously appreciated. Despite this, the role of HRCT in young children with CF has yet to be defined, principally because the repeated exposure of children to X-ray doses several multiples that of a standard chest X-ray raises the concern of the long-term risks of ionizing radiation. With the challenges of acquiring HRCT images in young children in mind, we review scanning protocols and settings specific to young children, and review the best available evidence that describes early structural lung disease in young children with CF. The role of CT scoring and quantitative measures of CF lung disease are reviewed. The challenge for the future is to develop techniques that provide clinically useful information at the lowest possible radiation risk.

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.

Estimation of the radiation dose from thoracic CT scans in a cystic fibrosis population

OBJECTIVE

To determine the radiation exposure associated with CT scans in a population of patients with cystic fibrosis (CF).

METHODS

We reviewed the medical charts of patients with typical CF who received regular medical management in a reference center from birth to March 31, 2004.

RESULTS

Among 80 patients with a total follow-up time of 1,231 person-years, 79 patients received a total of 269 CT scans, including 249 thoracic CT scans. The full parameters of the examination were available for 185 thoracic CT scans, allowing the effective dose (ED) and organ doses to be calculated. The ED was determined by the number of slices and the type of CT scans. The ED per thoracic CT scan was asymmetrically distributed (mean ED, 6.5 mSv; range 1.5 to 29.3 mSv). The mean doses delivered to the four most strongly exposed organs (lungs, breasts, bone marrow, and thyroid gland) were 18.6, 16.9, 5.2, and 3.5 mGy, respectively. The mean lifetime number of CT scans per patient was 3.2 (range, 0 to 13 scans), and the average lifetime ED was 19.5 mSv per patient (range, 2.2 to 75.8 mSv). Age at the first CT scan fell over the years, from 20 years for patients born before 1980 to 1.9 years for patients born after 1997.

CONCLUSION

The mean ED per CT scan in CF patients is about 6.5 mSv. Age at the first CT scan is lower in the most recent generation of patients. The lifetime ED of radiation received by CF patients, especially in the most recent generation, warrants long-term follow-up.

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.

Computed tomography and cystic fibrosis: promises and problems

Computed tomography (CT) has two potential roles in the evaluation of patients with cystic fibrosis (CF) lung disease: as a diagnostic test primarily for the detection of supervening complications and as a monitoring tool in clinical research. Interest in the latter role has gained momentum in the last 5 years because of two factors: (1) therapeutic options for CF lung disease are developing rapidly, hence the need for an outcome measure that can be applied in clinical intervention trials; and (2) it has become clear that traditional outcome measures such as pulmonary function tests are relatively insensitive to the early structural damage that occurs in CF. Several recent studies have shown that CT can be used as a potential surrogate outcome measure, although its suitability for this specific role is controversial and still under investigation. This review summarises current concepts relating to the research applications of CT in CF, with particular emphasis on the evidence supporting the use of CT as a surrogate outcome measure in clinical trials.

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

PURPOSE OF REVIEW

To summarize the role of chest computed tomography as a tool to evaluate cystic fibrosis lung disease, and to describe what abnormalities can be detected using computed tomography and how computed tomography can be used in clinical practice.

RECENT FINDINGS

Pulmonary function tests are only an indirect measure of lung structure, and are insensitive to localized and early structural abnormalities. Computed tomography is able to detect small areas with localized severe damage. The differentiation between normal and abnormal on computed tomography is relatively easy. In half of cystic fibrosis patients, the information obtained from pulmonary function tests is discordant with the information obtained from computed tomography.

SUMMARY

Cystic fibrosis patients show lung inflammation and infection starting early in life. This leads to irreversible structural lung damage such as bronchiectasis and air trapping. Cystic fibrosis lung disease varies widely between patients. The primary aim of therapy is to prevent structural damage and to conserve lung function. Adequate monitoring of cystic fibrosis lung disease is paramount to tailor treatment to a patient's need. Computed tomography is currently the best tool to monitor lung structure, and pulmonary function tests are the best to monitor lung function.

Computed tomography dose and variability of airway dimension measurements: how low can we go?

BACKGROUND

Quantitative CT shows promise as an outcome measure for cystic fibrosis (CF) lung disease in infancy, but must be accomplished at a dose as low as reasonably achievable.

OBJECTIVE

To determine the feasibility of ultra-low-dose CT for quantitative measurements of airway dimensions.

MATERIALS AND METHODS

Two juvenile pigs were anesthetized and their lungs scanned at 25 cm H(2)O face-mask pressure in apnoea using beam currents of 5, 10, 20, 40 and 100 mAs. The lumen diameters and wall thicknesses of matched airways (n=22) at each dose were measured by two observers using validated software. Measurement variability at each dose was compared to that at 100 mAs (reference dose) for large and small airways (lumen diameter <2.5 mm).

RESULTS

Lowering CT dose (mAs) affected measurement variability for lumen diameter of small and large airways (P<0.001) and for wall thickness of small (P<0.001), but not large (P=0.63), airways. To obtain the same measurement variability at 5 mAs as at 100 mAs, four to six small airways or one to three large airways have to be measured and averaged.

CONCLUSION

Quantitative airway measurements are feasible on images obtained at as low as 5 mAs, but more airways need to be measured to compensate for greater measurement variability.