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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

Introduction Cardiovascular disease (CVD) is an important cause of death in breast cancer survivors. Some breast cancer treatments including anthracyclines, trastuzumab and radiotherapy can increase the risk of CVD, especially for patients with pre-existing CVD risk factors. Early identification of patients at increased CVD risk may allow switching to less cardiotoxic treatments, active surveillance or treatment of CVD risk factors. One of the strongest independent CVD risk factors is the presence and extent of coronary artery calcifications (CAC). In clinical practice, CAC are generally quantified on ECGtriggered cardiac CT scans. Patients with breast cancer treated with radiotherapy routinely undergo radiotherapy planning CT scans of the chest, and those scans could provide the opportunity to routinely assess CAC before a potentially cardiotoxic treatment. The Bragatston study aims to investigate the association between calcifications in the coronary arteries, aorta and heart valves (hereinafter called ‘cardiovascular calcifications’) measured automatically on planning CT scans of patients with breast cancer and CVD risk. Methods and analysis In a first step, we will optimise and validate a deep learning algorithm for automated quantification of cardiovascular calcifications on planning CT scans of patients with breast cancer. Then, in a multicentre cohort study (University Medical Center Utrecht, Utrecht, Erasmus MC Cancer Institute, Rotterdam and Radboudumc, Nijmegen, The Netherlands), the association between cardiovascular calcifications measured on planning CT scans of patients with breast cancer (n≈16 000) and incident (non-)fatal CVD events will be evaluated. To assess the added predictive value of these calcifications over traditional CVD risk factors and treatment characteristics, a case-cohort analysis will be performed among all cohort members diagnosed with a CVD event during follow-up (n≈200) and a random sample of the baseline cohort (n≈600). Ethics a

_Background and aims:_ Calcifications of the intracranial internal carotid artery (iICA) are an important risk factor for stroke. The calcifications can occur both in the intimal and medial layer of the vascular wall. The aim of this study is to assess whether medial calcification in the iICA is differently related to risk factors for cardiovascular disease, compared to intimal calcification. _Methods:_ Unenhanced thin slice computed tomography (CT) scans from 1132 patients from the Dutch acute stroke study cohort were assessed for dominant localization of calcification (medial or intimal) by one of three observers based on established methodology. Associations between known cardiovascular risk factors (age, gender, body mass index, pulse pressure, eGFR, smoking, hypertension, diabetes mellitus, hyperlipidemia, previous vascular disease, and family history) and the dominant localization of calcifications were assessed via logistic regression analysis. _Results:_ In the 1132 patients (57% males, mean age 67.4 years [SD 13.8]), dominant intimal calcification was present in 30.9% and dominant medial calcification in 46.9%. In 10.5%, no calcification was seen. Age, pulse pressure and family history were risk factors for both types of calcification. Multivariably adjusted risk factors for dominant intimal calcification only were smoking (OR 2.09 [CI 1.27–3.44]) and hypertension (OR 2.09 [CI 1.29–3.40]) and for dominant medial calcification diabetes mellitus (OR 2.39 [CI 1.11–5.14]) and previous vascular disease (OR 2.20 [CI 1.30–3.75]). _Conclusions:_ Risk factors are differently related to the dominant localizations of calcifications, a finding that supports the hypothesis that the intimal and medial calcification represents a distinct etiology.

Objectives Although exponential growth is assumed for lung cancer, this has never been quantified in vivo. Aim of this study was to evaluate and quantify growth patterns of lung cancers detected in the Dut

__Background:__ Complications might occur after great vessel stent implantation in children. Therefore follow- up using imaging is warranted. __Purpose:__ To determine the optimal imaging modality for the assessment of stents used to treat great vessel obstructions in children. __Material and methods:__ Five different large vessel stents were evaluated in an in-vitro setting. All stents were expanded to the maximal vendor recommended diameter (20mm; n = 4 or 10mm; n = 1), placed in an anthropomorphic chest phantom and imaged with a 256-slice CT-scanner. MRI images were acquired at 1.5T using a multi-slice T2-weighted turbo spin echo, an RFspoiled three-dimensional T1-weighted Fast Field Echo and a balanced turbo field echo 3D sequ

Background To study dose reduction using iterative reconstruction (IR) for pediatric great vessel stent computed tomography (CT). Methods Five different great vessel stents were separately placed in a gel-containing plastic holder within an anthropomorphic chest phantom. The stent lumen was filled with diluted contrast gel. CT acquisitions were performed at routine dose, 52% and 81% reduced dose and reconstructed with filtered back projection (FBP) and IR. Objective image quality in terms of noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) as well as subjective image quality were evaluated. Results Noise, SNR and CNR were improved with IR at routine and 52% reduced dose, compared to FBP at routine dose. The lowest dose level resulted in decreased objective image quality with both FBP and IR. Subjective image quality was excellent at all dose levels. Conclusion IR resulted in improved objective image quality at routine dose and 52% reduced dose, while objective image quality deteriorated at 81% reduced dose. Subjective image quality was not affected by dose reduction.

Osteoporosis is more common in patients with COPD and in smokers. The aim of this study was to assess whether measures of emphysema and airway disease on computed tomography (CT) were associated with lower bone density or vertebral fractures in smokers with and without COPD. For this purpose, we included participants from the NELSON lung cancer screening trial. Bone density was measured as Hounsfield Units in the first lumbar vertebra, and vertebral fractures were assessed semiquantitatively. The 15th percentile method (Perc15) was used to assess emphysema, and the airway lumen perimeter (Pi10) was used for airway wall thickness. Expiratory/inspiratory-ratiomean lung density (E/I-ratioMLD) was used as a measure for air trapping and tracheal index to assess tracheal deformity. Linear regression models and logistic regression models were used to assess associations between CT biomarkers, bone density, and presence of fractures. Exactly 1,093 male participants were eligible for analysis. Lower Perc15 and higher E/I-ratioMLD were significantly associated with lower bone density (b=-1.27, P=0.02 and b=-0.37, P=0.02, respectively). Pi10 and tracheal index were not associated with bone density changes. CT-derived biomarkers were not associated with fracture prevalence. Bone density is lower with increasing extent of emphysema and small airway disease but is not associated with large airway disease and tracheal deformity. This may indicate the necessity to measure bone density early in smokers with emphysema and air trapping to prevent vertebral fractures.

Objective: To determine inter-observer and inter-examination variability of manual attenuation measurements of the vertebrae in low-dose unenhanced chest computed tomography (CT). Methods: Three hundred and sixty-seven lung cancer screening trial participants who underwent baseline and repeat unenhanced low-dose CT after 3 months because of an indeterminate lung nodule were included. The CT attenuation value of the first lumbar vertebrae (L1) was measured in all CTs by one observer to obtain inter-examination reliability. Six observers performed measurements in 100 randomly selected CTs to determine agreement with limits of agreement and Bland-Altman plots and reliability with intraclass correlation coefficients (ICCs). Reclassification analyses were performed using a threshold of 110 HU to define osteoporosis. Results: Inter-examination reliability was excellent with an ICC of 0.92 (p < 0.001). Inter-examination limits of agreement ranged from -26 to 28 HU with a mean difference of 1 ± 14 HU. Inter-observer reliability ICCs ranged from 0.70 to 0.91. Inter-examination variability led to 11.2 % reclassification of participants and inter-observer variability led to 22.1 % reclassification. Conclusions: Vertebral attenuation values can be manually quantified with good to excellent inter-examination and inter-observer reliability on unenhanced low-dose chest CT. This information is valuable for early detection of osteoporosis on low-dose chest CT. Key Points: • Vertebral attenuation values can be manually quantified on low-dose unenhanced CT reliably.• Vertebral attenuation measurements may be helpful in detecting subclinical low bone density.• This could become of importance in the detection of osteoporosis.

Objectives Coronary artery calcium (CAC) is a strong and independent predictor of cardiovascular disease (CVD) risk. This study assesses reproducibility of automatic CAC scoring on radiotherapy planning computed tomography (CT) scans of breast cancer patients, and examines its association with traditional cardiovascular risk factors. Methods This study included 561 breast cancer patients undergoing radiotherapy between 2013 and 2015. CAC was automatically scored with an algorithm using supervised pattern recognition, expressed as Agatston scores and categorized into five categories (0, 1-10, 11-100, 101-400, >400). Reproducibility between automatic and manual expert scoring was assessed in 79 patients with automatically determined CAC above zero and 84 randomly selected patients without automatically determined CAC. Interscan reproducibility of automatic scoring was assessed in 294 patients having received two scans (82% on the same day). Association between CAC and CVD risk factors was assessed in 36 patients with CAC scores >100, 72 randomly selected patients with scores 1-100, and 72 randomly selected patients without CAC. Reliability was assessed with linearly weighted kappa and agreement with proportional agreement. Results 134 out of 561 (24%) patients had a CAC score above zero. Reliability of CVD risk categorization between automatic and manual scoring was 0.80 (95% Confidence Interval (CI): 0.74-0.87), and slightly higher for scans with breath-hold. Agreement was 0.79 (95% CI: 0.72-0.85). Interscan reliability was 0.61 (95% CI: 0.50-0.72) with an agreement of 0.84 (95% CI: 0.80-0.89). Ten out of 36 (27.8%) patients with CAC scores above 100 did not have other cardiovascular risk factors. Conclusions Automatic CAC scoring on radiotherapy planning CT scans is a reliable method to assess CVD risk based on Agatston scores. One in four breast cancer patients planned for radiotherapy have elevated CAC score. One in three patients with high CAC scores don't have o

To assess the prognostic value of aortic valve and mitral valve/annulus calcifications for cardiovascular events in heavily smoking men without a history of cardiovascular disease. Heavily smoking men without a cardiovascular disease history who underwent non-contrast-enhanced low-radiation-dose chest CT for lung cancer screening were included. Non-imaging predictors (age, smoking status and pack-years) were collected and imaging-predictors (calcium volume of the coronary arteries, aorta, aortic valve and mitral valve/annulus) were obtained. The outcome was the occurrence of cardiovascular events. Multivariable Cox proportional-hazards regression was used to calculate hazard-ratios (HRs) with 95 % confidence interval (CI). Subsequently, concordance-statistics were calculated. In total 3111 individuals were included, of whom 186 (6.0 %) developed a cardiovascular event during a follow-up of 2.9 (Q1–Q3, 2.7–3.3) years. If aortic (n = 657) or mitral (n = 85) annulus/valve calcifications were present, cardiovascular event incidence increased to 9.0 % (n = 59) or 12.9 % (n = 11), respectively. HRs of aortic and mitral valve/annulus calcium volume for cardiovascular events were 1.46 (95 % CI, 1.09–1.84) and 2.74 (95 % CI, 0.92–4.56) per 500 mm3. The c-statistic of a basic model including age, pack-years, current smoking status, coronary and aorta calcium volume was 0.68 (95 % CI, 0.63–0.72), which did not change after adding heart valve calcium volume. Aortic valve calcifications are predictors of future cardiovascular events. However, there was no added prognostic value beyond age, number of pack-years, current smoking status, coronary and aorta calcium volume for short term cardiovascular events.

Background: Beyond lung cancer, screening CT contains additional information on other smoking related diseases (e.g. chronic obstructive pulmonary disease, COPD). Since pulmonary function testing is not regularly incorporated in lung cancer screening, imaging biomarkers for COPD are likely to provide important surrogate measures for disease evaluation. Therefore, this study aims to determine the independent diagnostic value of CT emphysema, CT air trapping and CT bronchial wall thickness for COPD in low-dose screening CT scans.Methods: Prebronchodilator spirometry and volumetric inspiratory and expiratory chest CT were obtained on the same day in 1140 male lung cancer screening participants. Emphysema, air trapping and bronchial wall thickness were automatically quantified in the CT scans. Logistic regression analysis was performed to derivate a model to diagnose COPD. The model was internally validated using bootstrapping techniques.Results: Each of the three CT biomarkers independently contributed diagnostic value for COPD, additional to age, body mass index, smoking history and smoking status. The diagnostic model that included all three CT biomarkers had a sensitivity and specificity of 73.2% and 88.%, respectively. The positive and negative predictive value were 80.2% and 84.2%, respectively. Of all participants, 82.8% was assigned the correct status. The C-statistic was 0.87, and the Net Reclassification Index compared to a model without any

Background: Little is known about the factors associated with CT-quantified emphysema progression in heavy smokers. The objective of this study was to investigate the effect of length of smoking cessation and clinical / demographical factors on the rate of emphysema progression and FEV1-decline in male heavy smokers.Methods: 3,670 male smokers with mean (SD) 40.8 (17.9) packyears underwent chest CT scans and pulmonary function tests at baseline and after 1 and 3 years follow-up. Smoking status (quitted ≥5, ≥1-<5, <1 years or current smoker) was noted. Rate of progression of emphysema and FEV1-decline after follow-up were assessed by analysis of variance adjusting for age, height, baseline pulmonary function and emphysema severity, packyears, years in study and respiratory symptoms. The quitted ≥5 group was used as reference.Results: Median (Q1-Q3) emphysema severity,<-950 HU, was 8.8 (5.1 - 14.1) and mean (SD) FEV1 was 3.4 (0.73) L or 98.5 (18.5) % of predicted. The group quitted '>5 years' showed significantly lower rates of progression of emphysema compared to current smokers, 1.07% and 1.12% per year, respectively (p<0.001). Current smokers had a yearly FEV1-decline of 69 ml, while subjects quit smoking >5 years had a yearly decline of 57.5 ml (p<0.001).Conclusion: Quit smoking >5 years significantly slows the rate of emphysema progression and lung function decline.Trial registration: Registered at http://www.trialregister.nl with trial number ISRCTN63545820.

Background:Current smokers have an increased cardiovascular disease (CVD) risk compared to ex-smokers due to reversible as well as irreversible effects of smoking. We investigated if current smokers remain to have an increased CVD risk compared to ex-smokers in subjects with a long and intense smoking history. We in addition studied if the effect of smoking continuation on CVD risk is independent of or modified by the presence of cardiovascular calcifications.Methods:The cohort used

Rationale: Accurate measurement of subsolid pulmonary nodules (SSN) is becoming increasingly important in the management of these nodules. SSNs were previously quantified with time-consuming manual measurements. The aim of the present study is to test the feasibility of semi-automatic SSNs measurements and to compare the results to the manual measurements. Methods: In 33 lung cancer screening participants with 33 SSNs, the nodules were previously quantified by two observers manually. In the present study two observers quantified these nodules by using semi-automated nodule volumetry software. Nodules were quantified for effective diameter, volume and mass. The manual and semi-automatic measurements were compared using Bland-Altman plots and paired T tests. Observer agreement was calculated as an intraclass correlation coefficient. Data are presented as mean (SD). Results: Semi-automated measurements were feasible in all 33 nodules. Nodule diameter, volume and mass were 11.2 (3.3) mm, 935 (691) ml and 379 (311) milligrams for observer 1 and 11.1 (3.7) mm, 986 (797) ml and 399 (344) milligrams for observer 2, respectively. Agreement between observers and within observer 1 for the semi-automatic measurements was good with an intraclass correlation coefficient >0.89. For observer 1 and observer 2, measured diameter was 8.8% and 10.3% larger (p<0.001), measured volume was 24.3% and 26.5% larger (p<0.001) and measured mass was 10.6% and 12.0% larger (p<0.001) with the semi-automatic program compared to the manual measurements. Conclusion: Semi-automated measurement of the diameter, volume and mass of SSNs is feasible with good observer agreement. Semi-automated measurement makes quantification of mass and volume feasible in daily practice.

Background:There is increasing evidence that structural lung changes may be present before the occurrence of airflow limitation as assessed by spirometry. This study investigated the prevalence of computed tomography (CT) quantified emphysema, airway wall thickening and gas trapping according to classification of airflow limitation (FEV1/FVC <70% and/or < the lower limit of normal (LLN)) in (heavy) smokers.Methods:A total number of 1,140 male former and current smokers participating in a lung cancer screenings trial (NELSON) were included and underwent chest CT scanning and spirometry. Emphysema was quantified by the 15th percentile, air way wall thickening by the square root of wall area for a theoretical airway with 10mm lumen perimeter (Pi10) and gas trapping by the mean lung density expiratory/inspiratory (E/I)-ratio. Participants were classified by entry FEV1/FVC: group 1>70%; group 2<70% but >LLN; and group 370% but FEV1 <80% predicted, were excluded. Multivariate regression analysis correcting for covariates was used to asses the extent of emphysema, airway wall thickening and gas trapping according to three groups of airflow limitation.Results:Mean (standard deviation) age was 62.5 (5.2) years and packyears smoked was 41.0 (18.0). Group 2 subjects when compared to group 1 had a significantly lower 15th percentile, -920.6 HU versus -912.2 HU; a higher Pi10, 2.87 mm versus 2.57 mm; and a higher E/I-ratio, 88.6% versus 85.6% (all p<0.001).Conclusion:Subjects with an FEV1/FVC<70%, but above the LLN, have a significant greater degree of structural lung changes on CT compared to subjects without airflow limitation.

Purpose: To estimate the performance of digital chest radiography for detection of lung cancer. Materials and Methods: The study had ethics committee approval, and a nested case-control design was used and included 55 patients with lung cancer detected at computed tomography (CT) and confirmed with histologic examination and a sample of 72 of 4873 control subjects without nodules at CT. All patients underwent direct-detector digital chest radiography in two projections within 2 months of the screening CT. Four radiologists with varying experience identified and localized potential cancers on chest radiographs by using a confidence scale of level 1 (no lesion) to 5 (definite lesion). Localization receiver operating characteristic (ROC) analysis was performed. On the basis of the assumption that suspicious lesions seen at chest radiography would lead to further work-up with CT, the number of work-up CT examinations per detected cancer (CT examinations per cancer) was calculated at various confidence levels for the screening population (cancer rate in study population, 1.3%). Results: Tumor size ranged from 6.8 to 50.7 mm (median, 11.8 mm). Areas under the localization ROC curve ranged from 0.52 to 0.69. Detection rates substantially varied with the observers' experience and confidence level: At a confidence level of 5, detection rates ranged from 18% at one CT examination per cancer to 53% at 13 CT examinations per cancer. At a confidence level of 2 or higher, detection rates ranged from 94% at 62 CT examinations per cancer to 78% at 44 CT examinations per cancer. Conclusion: A detection rate of 94% for lung tumors with a diameter of 6.8-50.7 mm found at CT screening was achievable with chest radiography only at the expense of a high false-positive rate and an excessive number of work-up CT examinations. Detection performance is strongly observer dependent.

Background: High-resolution CT (HRCT) scan data on primary ciliary dyskinesia (PCD) related lung disease are scarce. Study objectives: We evaluated the lung disease in children and adults with PCD by a modified Brody composite HRCT scan score to assess the prevalence of the structural abnormalities; to evaluate the correlation among HRCT scan scores, spirometry findings, and clinical data; and to compare the PCD scores with those of age-matched and sex-matched cystic fibrosis (CF) patients. Patients and methods: Twenty PCD patients (age range, 4.6 to 27.5 years) underwent HRCT scanning, spirometry, and deep throat or sputum culture. A modified Brody score was used to assess bronchiectasis, mucous plugging, peribronchial thickening, parenchyma abnormalities, and mosaic perfusion. Results: The total HRCT scan score was 6% of the maximal score (range, 0.5 to 25.5). Subscores were as follows: bronchiectasis, 5.6%; mucous plugging, 5.6%; peribronchial thickening, 8.3%; parenchyma, 3%; and mosaic perfusion, 0%. The prevalence of lung changes were as follows: bronchiectasis, 80%; peribronchial thickening, 80%; mucous plugging, 75%; parenchyma, 65%; and mosaic perfusion, 45%. Sixteen of 19 PCD patients had positive culture findings, and the most common pathogen found was Haemophilus influenzae (84%). The total HRCT scan score was significantly related to age (p = 0.006), FEV1(p = 0.02), and FVC (p = 0.02). The bronchiectasis subscore was significantly related to FEV1(p = 0.04) and FVC (p = 0.03). In CF patients, the total HRCT scan score was significantly higher than that in PCD patients (p = 0.02). Conclusions: PCD patients show significantly lower pulmonary HRCT scan scores than CF patients. The PCD total and bronchiectasis scores correlate with spirometry findings. The PCD HRCT scan score might be used for longitudinal assessment and/or represent an outcome surrogate in future studies. Copyright

Background: A study was undertaken to compare the ability of computed tomographic (CT) scores and pulmonary function tests to detect changes in lung disease in children and adults with cystic fibrosis (CF). Methods: CT scans and pulmonary function tests were retrospectively studied in a cohort of patients with CF aged 5-52 years for whom two or three CT scans at 3 year intervals were available, together with pulmonary function test results. All CT scans were scored by two observers. Pulmonary function results were expressed as percentage predicted and Z scores. Results: Of 119 patients studied, two CT scans were available in 92 patients and three in 24. CT (composite and component) scores and lung function both deteriorated significantly (p<0.02). Peripheral bronchiectasis worsened by 1.7% per year in children (p<0.0001) and by 1.5% per year in adults (p<0.0001). Bronchiectasis worsened in 68 of 92 patients while forced expiratory volume in 1 second (FEV1) worsened in 54 of 92 patients; bronchiectasis also deteriorated in 27 patients with stable or improving FEV1. The CT score (and its components) and pulmonary function tests showed similar rates of deterioration in adults and children (p>0.09). Conclusion: The peripheral bronchiectasis CT score deteriorates faster and more frequently than lung function parameters in children and adults with CF, which indicates that pulmonary function tests and CT scans measure different aspects of CF lung disease. Our data support previous findings that the peripheral bronchiectasis CT score has an added value to pulmonary function tests in monitoring CF lung disease.

Rationale: Low-dose radiation from computed tomography (CT) may increase the risk of certain cancers, especially in children. Objective: We sought to estimate the excess all-cause and cancerspecific morta

For clinical management of cystic fibrosis (CF) lung disease to be effective, onset and worsening of lung abnormalities should be closely monitored. Pulmonary function tests (PFTs) are currently the gold standard to monitor CF lung disease. Lung structure can be more sensitively monitored using computed tomography (CT) rather than chest radiography. Firstly, we compared in two pediatric cohorts the sensitivities of CT and PFTs to detect onset and worsening of CF lung disease. We showed that five published CT scoring systems are comparable and have good intra- and interobserver agreement. Secondly, we showed that CT scoring systems and quantitative CT-measurements of airway wall thickening and bronchiectasis are more sensitive to detect the start and worsening of CF lung disease than are PFTs. Bronchiectasis-score worsened most in children and the worsening remained undetected by the PFTs and the quantitative measurements. Quantitative CT-measurements of air! way wall thickening worsened significantly, whereas PFTs and airway wall thickness measured by scoring remained unchanged. Thirdly, we developed a computational model to study radiation risks associated with CT scanning in CF. Risks from lifelong biennial CT scanning in CF were found to be acceptably low given the currently reduced life expectancy. Finally we provided normal CT-values of lung parenchyma and airway wall and lumen that can be used to study lung growth aberrations due to CF. Our data support routine CT scanning to monitor CF lung disease. In addition, bronchiectasis-score and quantitatively measured airway wall thickening may be useful surrogate endpoints for clinical trials in CF.

For effective clinical management of cystic fibrosis (CF) lung disease it is important to closely monitor the start and progression of lung damage. The aim of this study was to investigate the ability of high-resolution computed tomography (HRCT) scoring systems and pulmonary function tests (PFT) to detect changes in lung disease. CF children (n=48) had two HR

Anatomical studies suggest that normal lungs grow by rapid alveolar addition until about 2 yrs of age followed by a gradual increase in alveolar dimensions. The aim of this study was to examine the hypothesis that normal lung growth can be monitored by computed tomography (CT). Therefore, the gas volume per gram of lung tissue was estimated from measurements of lung density obtained from CT scans performed on children throughout the growth period. CT scans were performed on 17 males and 18 females, ranging in age from 15 days-17.6 yrs. CT-measured lung weight was correlated with predicted post mortem values and CT measured gas volume with predicted values of functional residual capacity. The median value for lung expansion was 1.86 mL x g(-1) at 15 days, decreased to 0.79 mL x g(-1) by 2 yrs and then increased steadily to 5.07 mL x g(-1) at 17 yrs. Computed tomography scans can be used to estimate lung weight, gas volume and expansion of normal lungs during the growth period. The increase in the lung expansion after the age of 2 yrs suggests progressive alveolar expansion with increasing lung volume.