Measurements Of Airway Dimensions Research Articles

Quantification of airway dimensions using a high-resolution CT scanner: A phantom study.

Small airways with inner diameters less than 2mm are sites of major airflow limitations in patients with chronic obstructive pulmonary disease (COPD) and asthma. The purpose of this study is to investigate the limitations for accurate assessment of small airway dimensions using both high-resolution CT (HRCT) and conventional normal-resolution CT at low dose levels. To model the normal human airways from the 3rd to 20th generations, a cylindrical polyurethane phantom with 14 airway tubes of inner diameters (ID) ranging from 0.3 to 3.4mm and wall thicknesses (WT) ranging from 0.15 to 1.6mm was placed within an Anthropomorphic QRM-Thorax phantom. The Aquilion Precision (Canon Medical Systems Corporation) HRCT scanner was used to acquire images at 80, 100, and 120kV using high resolution mode (HR, 0.25mm×160 detector configuration) and normal-resolution (NR) mode (0.5mm×80 detector configuration). The HR data were reconstructed using a 1024×1024matrix (0.22×0.22×0.25mm voxel size) and the NR data were reconstructed using a 512×512matrix (0.43×0.43×0.50mm). Two reconstruction algorithms (filtered back projection; FBP and an adaptive iterative dose reduction 3D algorithm; AIDR 3D) and three reconstruction kernels (FC30, FC52, and FC56) were investigated. The dose values ranged from 0.2 to 6.2mGy. A refined automated full-width half-maximum (FWHM) method was used for the measurement of airway dimensions, where the density profiles were computed by radial oversampling using a polar coordinate system. Both ID and WT were compared to the known dimensions using a regression model, and the root-mean-square error (RMSE) and average error were computed across all 14 airway tubes. The results indicate that the ID can be measured within a 15% error down to approximately 0.8 and 2.0mm using the HR and NR modes, respectively. The overall RMSE (and average error) of ID measurements for HR and NR were 0.10mm (-0.70%) and 0.31mm (-2.63%), respectively. The RMSE (and average error) of WT measurements using HR and NR were 0.10mm (23.27%) and 0.27mm (53.56%), respectively. The WT measurement using HR yielded a factor of two improvement in accuracy as compared to NR. High-resolution CT can provide more accurate measurements of airway dimensions as compared with NR CT, potentially improving quantitative assessment of pathologies such as COPD and asthma. The HR mode acquired and reconstructed with AIDR3D and the FC52kernel provides most accurate measurement of airway dimensions. Low-dose HR measurements at dose level above 0.9mGy can provide improved accuracy on both inner diameters and wall thicknesses compared to full dose NR airway phantom measurements.

Vocalization with semi-occluded airways is favorable for optimizing sound production.

Vocalization in mammals, birds, reptiles, and amphibians occurs with airways that have wide openings to free-space for efficient sound radiation, but sound is also produced with occluded or semi-occluded airways that have small openings to free-space. It is hypothesized that pressures produced inside the airway with semi-occluded vocalizations have an overall widening effect on the airway. This overall widening then provides more opportunity to produce wide-narrow contrasts along the airway for variation in sound quality and loudness. For human vocalization described here, special emphasis is placed on the epilaryngeal airway, which can be adjusted for optimal aerodynamic power transfer and for optimal acoustic source-airway interaction. The methodology is three-fold, (1) geometric measurement of airway dimensions from CT scans, (2) aerodynamic and acoustic impedance calculation of the airways, and (3) simulation of acoustic signals with a self-oscillating computational model of the sound source and wave propagation.

Emphysema quantified: mapping regional airway dimensions using 2D phase contrast X-ray imaging.

We have developed an analyser-based phase contrast X-ray imaging technique to measure the mean length scale of pores or particles that cannot be resolved directly by the system. By combining attenuation, phase and ultra-small angle X-ray scattering information, the technique was capable of measuring differences in airway dimension between lungs of healthy mice and those with mild and severe emphysema. Our measurements of airway dimensions from 2D images showed a 1:1 relationship to the actual airway dimensions measured using micro-CT. Using 80 images, the sensitivity and specificity were measured to be 0.80 and 0.89, respectively, with the area under the ROC curve close to ideal at 0.96. Reducing the number of images to 11 slightly decreased the sensitivity to 0.75 and the ROC curve area to 0.90, whilst the specificity remained high at 0.89.

Fritz Rohrer (1888-1926), a pioneer in pulmonary mechanics whose work was inexplicably ignored for about 30 years.

Fritz Rohrer (1888-1926) has a special place in the history of respiratory physiology for two reasons. The first is that he laid the foundations of modern pulmonary mechanics in the early 1900s. For example, his seminal paper on pulmonary dynamics, that is, the pressure-flow relationships in the airways, was published in 1915 in one of the top journals in the field. It included extensive measurements of airway dimensions in postmortem human lungs and a sophisticated analysis of the modes of airflow. This was closely followed by a very original analysis of lung statics, which included studies of airway pressures at normal, maximal, and minimal lung volumes in relaxed normal volunteers, and was published in 1916. Remarkably, both papers were essentially ignored at the time. Fortunately, in 1925 he was able to summarize his major findings in a chapter in an important handbook of physiology. However, he tragically died from pulmonary tuberculosis in the following year at the early age of 37. The second reason for his importance in the history of pulmonary mechanics is that inexplicably his very innovative research was essentially ignored for about 30 years. It was not until the 1940s that his work was rediscovered, although not in time to save investigators from duplicating his very original studies. Possible reasons why his work was ignored for so long are discussed. Even today it is not easy to recover some important features of his career, and some aspects of his very original research are still almost unknown.

Real-time robotic airway measurement: An additional benefit of a novel steady-hand robotic platform.

Describe the secondary capability of a robotic system to provide real-time measurements of airway dimensions with high fidelity. Seven unique phantoms of laryngotracheal stenosis (LTS) were modeled using a computer-aided design tool and were three dimensionally printed. These stenoses were of different dimensions and orientations, and some were purposefully oblique. The dimensions of the stenoses were then measured with the novel Robotic ENT (Ear, Nose, and Throat) Microsurgery System (REMS; Galen Robotics, Inc., Sunnyvale, CA) because it is capable of tool position memory in three dimensional (3D) space. Five participants (two laryngologists, two otolaryngology-head and neck surgery residents, one neurotology fellow) measured each axis of stenosis (anteroposterior, lateral, and craniocaudal) three times for each of the seven stenosis phantoms. These measurements were then compared to the known design dimensions. Mean magnitude of error (MOE) and interrater reliability (IRR) using an intraclass correlation coefficient (ICC) were then calculated. Mean MOE and standard deviation for all measurements was 0.306 ± 0.247 mm. Mean MOE was 0.374 ± 0.292 mm, 0.300 ± 0.237 mm, and 0.244 ± 0.185 mm for the anteroposterior, lateral, and craniocaudal dimensions of stenosis, respectively. Eighty-two percent of all measurements had MOE < 0.5 mm. ICC was 0.945 (95% confidence interval [CI]: 0.847-0.989), 0.995 (95% CI: 0.984-0.999), and 0.993 (95% CI: 0.987-0.999) for anteroposterior, lateral, and craniocaudal dimensions, respectively, indicating excellent agreement among participants. The REMS can be used to reliably and accurately measure airway dimensions in 3D regardless of the orientation of stenosis. This ability may be easily extrapolated to the measurement of any airway lesion during laryngotracheal surgery. 4 Laryngoscope, 129:324-329, 2019.

Quantitative measurement of airway dimensions using ultra-high resolution computed tomography.

Quantitative measurement of airway dimensions using computed tomography (CT) is performed in relatively larger airways due to the limited resolution of CT scans. Nevertheless, the small airway is an important pathological lesion in lung diseases such as chronic obstructive pulmonary disease (COPD) and asthma. Ultra-high resolution scanning may resolve the smaller airway, but its accuracy and limitations are unclear. Phantom tubes were imaged using conventional (512 × 512) and ultra-high resolution (1024 × 1024 and 2048 × 2048) scans. Reconstructions were performed using the forward-projected model-based iterative reconstruction solution (FIRST) algorithm in 512 × 512 and 1024 × 1024 matrix scans and the adaptive iterative dose reduction 3D (AIDR-3D) algorithm for all scans. In seven subjects with COPD, the airway dimensions were measured using the 1024 × 1024 and 512 × 512 matrix scans. Compared to the conventional 512 × 512 scan, variations in the CT values for air were increased in the ultra-high resolution scans, except in the 1024×1024 scan reconstructed through FIRST. The measurement error of the lumen area of the tube with 2-mm diameter and 0.5-mm wall thickness (WT) was minimal in the ultra-high resolution scans, but not in the conventional 512 × 512 scan. In contrast to the conventional scans, the ultra-high resolution scans resolved the phantom tube with ≥ 0.6-mm WT at an error rate of < 11%. In seven subjects with COPD, the WT showed a lower value with the 1024 × 1024 scans versus the 512 × 512 scans. The ultra-high resolution scan may allow more accurate measurement of the bronchioles with smaller dimensions compared with the conventional scan.

Imaging of Cystic Fibrosis Lung Disease and Clinical Interpretation.

Progressive lung disease in cystic fibrosis (CF) is the life-limiting factor of this autosomal recessive genetic disorder. Increasing implementation of CF newborn screening allows for a diagnosis even in pre-symptomatic stages. Improvements in therapy have led to a significant improvement in survival, the majority now being of adult age. Imaging provides detailed information on the regional distribution of CF lung disease, hence longitudinal imaging is recommended for disease monitoring in theclinical routine. Chest X-ray (CXR), computed tomography (CT) and magnetic resonance imaging (MRI) are now available as routine modalities, each with individual strengths and drawbacks, which need to be considered when choosing the optimal modality adapted to the clinical situation of the patient. CT stands out with the highest morphological detail and has often been a substitute for CXR for regular severity monitoring at specialized centers. Multidetector CT data can be post-processed with dedicated software for a detailed measurement of airway dimensions and bronchiectasis and potentially a more objective and precise grading of disease severity. However, changing to CT was inseparably accompanied by an increase in radiation exposure of CF patients, a young population with high sensitivity to ionizing radiation and lifetime accumulation of dose. MRI as a cross-sectional imaging modality free of ionizing radiation can depict morphological hallmarks of CF lung disease at lower spatial resolution but excels with comprehensive functional lung imaging, with time-resolved perfusion imaging currently being most valuable. • Hallmarks are bronchiectasis, mucus plugging, air trapping, perfusion abnormalities, and emphysema.• Imaging is more sensitive to disease progression than lung function testing.• CT provides the highest morphological detail but is associated with radiation exposure.• MRI shows comparable sensitivity for morphology but excels with additional functional information.• MRI sensitively depicts reversible abnormalities such as mucus plugging and perfusion abnormalities. Citation Format: • Wielpütz MO, Eichinger M, Biederer J et al. Imaging of Cystic Fibrosis Lung Disease and Clinical Interpretation. Fortschr Röntgenstr 2016; 188: 834 - 845.

Gender-related difference in the upper airway dimensions and hyoid bone position in Chinese Han children and adolescents aged 6–18 years using cone beam computed tomography

Objective. To investigate the gender-related differences in upper airway dimensions and hyoid bone position in Chinese Han children and adolescents (6–18 years) using cone-beam computed tomography (CBCT). Materials and methods. CBCT-scans of 119 boys and 135 girls were selected and divided into four groups (group 1: 6–9 years; group 2: 10–12 years; group 3: 13–15 years; group 4: 16–18 years). The airway dimensions including the cross-sectional area (CSA), anteroposterior (AP) and lateral (LAT) width, length (L), mean CSA and volume (VOL) of upper airway segmentations and hyoid bone position including 11 linear and three angular measurements were investigated using Materialism’s interactive medical image control system (MIMICS) 16.01 software. Gender-related differences were analyzed by two independent sample t-tests. Results. No gender-related difference was found in values of the facial morphology, airway dimensions and hyoid bone position for group 1 (p > 0.05). The children and adolescents in groups 2, 3 and 4 showed significant gender-related differences in the measurement results of facial morphology, airway dimensions and hyoid bone positions (p < 0.05). What’s more, the measurement values of boys were obviously larger than those of girls except some measurements in group 2. Conclusions. The measurements of airway dimensions and hyoid bone positions have gender-related differences in children and adolescents aged 10–18 years. These results could be taken into consideration during orthodontic diagnosis and treatment.

Pharyngeal airway dimensions: a cephalometric, growth-study-based analysis of physiological variations in children aged 6-17

The aim was to assess pharyngeal airway dimensions and physiological changes based on lateral cephalometric radiographs from healthy untreated children aged 6-17 years. The sample consisted of 880 lateral cephalograms (412 females and 468 males) of the Zurich Craniofacial Growth Study. Statistical analyses on cephalometric measurements of airway dimensions (distances 'p': shortest distance between soft palate and posterior pharyngeal wall and 't': shortest distance between tongue and posterior pharyngeal wall) and craniofacial parameters were performed. To disclose differences between different age groups, a Kruskal-Wallis test was applied. The influence of gender on 'p' and 't' was analysed by a Mann-Whitney U-test for each age group separately. The Spearman correlation was computed in order to investigate associations between craniofacial parameters. Variables associated with 'p' and 't' were chosen for multiple regression model investigation. The results demonstrated high interindividual variations. A slight influence of age on 'p' (P = 0.034) could be attested (+1.03 mm) but not on 't' (P = 0.208). With the exception of the 9-year age group, no significant differences between the genders were found. Correlation analysis revealed several statistically significant correlations between 't' or 'p' and antero-posterior cephalometric variables. All correlation coefficients were, however, very low and the adjusted coefficient of determination also revealed the regression model to be very weak. The high interindividual variations of 'p' and 't' render the use of reference values problematic. Contrary to other craniofacial structures, neither age-related changes nor sexual dimorphism were found for 'p' and 't'. Any associations to antero-posterior cephalometric characteristics seem low.

Low-dose CT measurements of airway dimensions and emphysema associated with airflow limitation in heavy smokers: a cross sectional study

BackgroundIncreased airway wall thickness (AWT) and parenchymal lung destruction both contribute to airflow limitation. Advances in computed tomography (CT) post-processing imaging allow to quantify these features. The aim of this Dutch population study is to assess the relationships between AWT, lung function, emphysema and respiratory symptoms.MethodsAWT and emphysema were assessed by low-dose CT in 500 male heavy smokers, randomly selected from a lung cancer screening population. AWT was measured in each lung lobe in cross-sectionally reformatted images with an automated imaging program at locations with an internal diameter of 3.5 mm, and validated in smaller cohorts of patients. The 15th percentile method (Perc15) was used to assess the severity of emphysema. Information about respiratory symptoms and smoking behavior was collected by questionnaires and lung function by spirometry.ResultsMedian AWT in airways with an internal diameter of 3.5 mm (AWT3.5) was 0.57 (0.44 - 0.74) mm. Median AWT in subjects without symptoms was 0.52 (0.41-0.66) and in those with dyspnea and/or wheezing 0.65 (0.52-0.81) mm (p<0.001). In the multivariate analysis only AWT3.5 and emphysema independently explained 31.1%and 9.5%of the variance in FEV1%predicted, respectively, after adjustment for smoking behavior.ConclusionsPost processing standardization of airway wall measurements provides a reliable and useful method to assess airway wall thickness. Increased airway wall thickness contributes more to airflow limitation than emphysema in a smoking male population even after adjustment for smoking behavior.

CT imaging of chronic obstructive pulmonary disease: role in phenotyping and interventions

Using CT to define phenotypic abnormalities in patients diagnosed as having chronic obstructive pulmonary disease (COPD) may serve to optimize treatment, guide the prognosis and assess response to potential therapeutic interventions. Although the different morphologic abnormalities seen on CT scans of COPD patients often overlap, two separate groups of patients can be identified, those with emphysema predominant disease and those with airway predominant disease due to chronic inflammation with resulting in airway remodelling and narrowing. The former category can be subdivided further based on the type of emphysema present and characterized further by anatomic distribution and severity using visual assessment and volumetric quantitative CT techniques. Patients in the airway predominant category can also be characterized by CT as showing bronchial wall thickening, small airway inflammation, mosaic perfusion and air trapping expressing small airway narrowing, and expiratory bronchial collapse due to cartilage deficiency. Recent advances in automated airway segmentation and quantitative analysis have made measurements of airway dimensions feasible. In longitudinal studies, standardization of procedures and quality control are needed, particularly if quantitative CT outcomes are used as end point in clinical trials and ultimately in the clinical management of individual patients.

Measuring airway dimensions during bronchoscopy using anatomical optical coherence tomography

Airway dimensions are difficult to quantify bronchoscopically because of optical distortion and a limited ability to gauge depth. Anatomical optical coherence tomography (aOCT), a novel imaging technique, may overcome these limitations. This study evaluated the accuracy of aOCT against existing techniques in phantom, excised pig and in vivo human airways. Three comparative studies were performed: 1) micrometer-derived area measurements in 10 plastic tubes were compared with aOCT-derived area; 2) aOCT-derived airway compliance curves from excised pig airways were compared with curves derived using an endoscopic technique; and 3) airway dimensions from the trachea to subsegmental bronchi were measured using aOCT in four anaesthetised patients during bronchoscopy and compared with computed tomography (CT) measurements. Measurements in plastic tubes revealed aOCT to be accurate and reliable. In pig airways, aOCT-derived compliance measurements compared closely with endoscopic data. In human airways, dimensions measured with aOCT and CT correlated closely. Bland-Altman plots showed that aOCT diameter and area measurements were higher than CT measurements by 7.6% and 15.1%, respectively. Airway measurements using aOCT are accurate, reliable and compare favourably with existing imaging techniques. Using aOCT with conventional bronchoscopy allows real-time measurement of airway dimensions and could be useful clinically in settings where knowledge of airway calibre is required.

Dosimetry Counts: Molecular Hypersensitivity May Not Drive Pulmonary Hyperresponsiveness

Airway hyperresponsiveness is one measure of allergic asthma. One such test, the methacholine challenge, uses an inhaled aerosol to induce changes in resistance to breathing. The test is also used to test hyperresponsiveness in rodent models of asthma. For two varieties of mice, the B6C3F1 and the Balb/c, exposure to aerosolized methacholine demonstrates that the Balb/c is 12x more responsive based on the concentration of methacholine in the solution used to produce the inhaled aerosol (the normally accepted dose-metric). Here we show that the 12x difference in exposure disappears when measurements of airway dimensions of generations 1-6 are used first to calculate deposited mass of methacholine; and second to account for the physiology of airway constriction and pressure drop. These observations in mice provide one explanation of how some hyperresponsive subjects can have no underlying molecular sensitivity; and how constriction in the upper airways can have greater impact on breathing than constriction of airway generations 6-16.

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

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

Airway dimensions measured from micro-computed tomography and high-resolution computed tomography

Volume averaging results in both over- and underestimation of airway dimensions when they are measured by high-resolution computed tomography (HRCT). The current authors calibrated computerised measurements of airway dimensions from HRCT against a novel three-dimensional micro-computed tomography (CT) standard, which has a 50-fold greater resolution, as well as against traditional morphometry. Inflation-fixed porcine lung cubes were scanned by HRCT and micro-CT. A total of 59 lumen area (Ai), 30 wall area (A(aw)) and 11 lumen volume (Vi) measurements were made. Ai was measured from the cut surface of 11 airways by morphometry. Airways in scanned images were matched using branching points. After calibration, the errors of Ai, A(aw) and Vi HRCT measurements were determined. The current authors found a systematic, size-dependent underestimation of Ai and overestimation of A(aw) from HRCT measurements. This was used to calibrate an HRCT measurement algorithm. The 95% limits of agreement of subsequent measurements were +/-3.2 mm2 for Ai, +/-4.3 mm2 for A(aw), and +/-11.2 mm3 for Vi with no systematic error. Morphometric measurements agreed with micro-CT (+/-2.5 mm2) without systematic error. In conclusion, micro-computed tomography image data from inflation-fixed airways can be used as calibration standards for three-dimensional lumen volume measurements from high-resolution computed tomography, while morphometry is acceptable for two-dimensional measurements. The image dataset could be used to validate other developmental three-dimensional segmentation algorithms.

Calculated Deposition in Growing Tracheobronchial Airways: Effect of Growth-Rate Assumptions

Most current deterministic computer dosimetry models use idealized dichotomous symmetrical infant, child, and adolescent tracheobronchial geometries for dosimetry predictions. These tracheobronchial geometries were derived from either the morphometric measurements of J. D. Mortensen and colleagues or those of R. F. Phalen and colleagues. The airway growth curves used to create these geometries are typically means from all airways within a single generation in the tracheobronchial tree. This idealized approach implies that the growth rate of all airways in the same generation is identical (symmetric growth, SG), which is unlikely. In this study, existing morphometric measurements of airway dimensions were used to determine growth equations for airway length, diameter, branch angle, and inclination to gravity as a function of body height for each airway in the first four tracheobronchial generations. Tracheobronchial geometries (asymmetrical growth, AG) were created from these growth curves for the first 4 tracheobronchial generations representing a 4- and 11-yr-old child and an adult. Particle deposition predictions for steady inspiratory flow using 0.1- to 20-μm diameter monodisperse particles in these AG geometries were compared with predictions using the SG geometries using the uniform growth rate approach. Each airway in the first four generations had a unique airway length and diameter growth rate. Airway branch angle and inclination to gravity did not change as a function of body height. The unique airway growth rates resulted in significant differences in predicted deposition efficiency between the AG and SG geometry. Use of AG geometry may provide improved estimates of regional particle deposition in infants, children, and adolescents.

Clinical Applications of Quantitative Computed Tomography in Chronic Lung Disease

Improved understanding of the pathophysiology of chronic lung disease at a molecular and cellular level has led to the concept of targeted pharmacotherapy for the modification of disease progression. The limitations of conventional physiological measures of disease have prompted the development of alternative methods for determining outcome in therapeutic trials. Technological improvements in computed tomography, coupled with the development of software for the automated calculation of densitometric parameters have resulted in more specific and sensitive measures of disease than traditional methods. Such techniques have been applied principally to the assessment of changes in lung parenchyma in patients with chronic obstructive pulmonary disease and, in particular, in patients with α1-antitrypsin deficiency where they have been used as an outcome measure in a therapeutic trial of α1-antitrypsin augmentation. Measurement of airway dimensions has proved more problematic and most studies have, until recently, been limited to anthropomorphic phantoms or ex-vivo specimens.

Quantitative Assessment of Airway Remodeling Using High-Resolution CT

Asthma and COPD are the most prevalent of lung diseases and contribute an enormous burden of morbidity in North America and globally. In both conditions, inflammation leads to airway remodeling, which contributes to airway narrowing. To date, airway remodeling has only been assessed using histological examination of airways. However, it may now be possible to assess and quantify the extent of airway remodeling in vivo using high-resolution CT (HRCT). The aim of this article is to review the use of HRCT in the investigation of airway remodeling. A number of investigators have reported techniques to make measurements of airway dimensions using CT and an increasing number of quantitative methods are being developed. Using these techniques, airway dimensions have been examined in patients with asthma and COPD. In patients with asthma, the airway wall area was increased without a decrease in luminal area, whereas in patients with COPD, the airway luminal area was decreased and airway wall area was increased. The different pattern of remodeling may reflect fundamental differences in the inflammatory processes in asthma and COPD and could influence the reversibility of the narrowing. It has also been shown that, by quantifying both the extent of emphysema and of airway remodeling, CT is useful in differentiating COPD patients who have primarily parenchymal disease from those who have primarily airway pathology. With additional advances in technology, it is likely that quantitative assessment of airway wall dimensions will ultimately provide a valuable tool for the study of airway disease.

Computed tomographic measurements of airway dimensions and emphysema in smokers. Correlation with lung function.

Chronic obstructive pulmonary disease (COPD) is characterized by the presence of airflow obstruction caused by emphysema or airway narrowing, or both. Low attenuation areas (LAA) on computed tomography (CT) have been shown to represent macroscopic or microscopic emphysema, or both. However CT has not been used to quantify the airway abnormalities in smokers with or without airflow obstruction. In this study, we used CT to evaluate both emphysema and airway wall thickening in 114 smokers. The CT measurements revealed that a decreased FEV(1) (%predicted) is associated with an increase of airway wall area and an increase of emphysema. Although both airway wall thickening and emphysema (LAA) correlated with measurements of lung function, stepwise multiple regression analysis showed that the combination of airway and emphysema measurements improved the estimate of pulmonary function test abnormalities. We conclude that both CT measurements of airway dimensions and emphysema are useful and complementary in the evaluation of the lung of smokers.

An Analysis Algorithm for Measuring Airway Lumen and Wall Areas from High-Resolution Computed Tomographic Data

High-resolution computed tomography (HRCT) has been used to examine airway narrowing. We developed an automated computed tomographic image analysis algorithm (computed tomographic airway morphometry; CTAM) to measure airway lumen area (Ai ), airway wall area (Awa), and airway angle of orientation. Tubes of varying size were embedded in Styrofoam and then scanned at angles between 0 degrees and 50 degrees to assess the accuracy of measurements made with CTAM. Two excised pig lungs were fixed in inflation, sectioned, and scanned. Ai and Awa were measured planimetrically from the cut surfaces to optimize CTAM measurement parameters. In CTAM, Ai was defined according to an airway-size-dependent threshold value, and total Awa was determined through a score-guided erosion method. Results were compared with measurements made through a previously validated method (manual method). CTAM provided accurate measurements of the tubes' Ai values at all angles; Awa was overestimated in direct relation to airway size. The manual method underestimated Ai and overestimated Awa in a manner directly related to airway size as well as to airway angle of orientation. In the excised lung, the mean errors of Ai and Awa measurements made with CTAM were 0.52 +/- 0.24 mm(2) and 0.17 +/- 0.32 mm(2) (mean +/- SEM), respectively. Ai errors with the manual method were similar, but Awa was overestimated to a greater degree (6.3 +/- 0.38 mm(2); p < 0.01) and the error was proportional to Awa (r = 0.64; p < 0.01). CTAM allows accurate measurements of airway dimensions and angle of orientation.