Quantitative CT Parameters Research Articles

Performance of quantitative CT parameters in assessment of disease severity in COPD: A prospective study.

Background:Both emphysematous destruction of lung parenchyma and airway remodeling is thought to contribute to airflow limitation in cases of chronic obstructive pulmonary disease (COPD).Objective:To evaluate the value of quantitative computed tomography (QCT) parameters of emphysema and airway disease with disease severity in patients with COPD.Materials and Methods:We prospectively studied 50 patients with COPD, which included nonsmokers and patients with different degrees of cumulative smoking exposure. Three QCT parameters namely LAA% (low attenuation area percentage), WA% (Wall area percentage), and pi10 were calculated as per the standard technique. Forced expiratory volume in 1 s (FEV1), BODE score, and MMRC dyspnea scale were used as measures of disease severity.Results:FEV1 was inversely and significantly associated with all three QCT parameters. Receiver operated characteristic curves in prediction of GOLD class 3 COPD yielded cut-off values of 12.2, 61.45, and 3.5 for LAA%, WA%, and pi10, respectively, with high sensitivities and specificities. In multiple linear regression model, however, only LAA% proved to be significantly associated with FEV1, BODE, and dyspnea.Conclusion:QCT indices of both emphysema and airway disease influence FEV1, dyspnea, and BODE score in patients with COPD. Emphysema, however, appears to be more closely related to disease severity.

Effect of smoking cessation on quantitative computed tomography in smokers at risk in a lung cancer screening population.

To longitudinally evaluate effects of smoking cessation on quantitative CT in a lung cancer screening cohort of heavy smokers over 4 years. After 4 years, low-dose chest CT was available for 314 long-term ex-smokers (ES), 404 continuous smokers (CS) and 39 recent quitters (RQ) who quitted smoking within 2 years after baseline CT. CT acquired at baseline and after 3 and 4 years was subjected to well-evaluated densitometry software, computing mean lung density (MLD) and 15th percentile of the lung density histogram (15TH). At baseline, active smokers showed significantly higher MLD and 15TH (-822±35 and -936±25 HU, respectively) compared to ES (-831±31 and -947±22 HU, p<0.01-0.001). After 3 years, CS again had significantly higher MLD and 15TH (-801±29 and -896±23 HU) than ES (-808±27 and -906±20 HU, p<0.01-0.001) but also RQ (-813±20 and -909±15 HU, p<0.05-0.001). Quantitative CT parameters did not change significantly after 4 years. Importantly, smoking status independently predicted MLD at baseline and year 3 (p<0.001) in multivariate analysis. On quantitative CT, lung density is higher in active smokers than ex-smokers, and sustainably decreases after smoking cessation, reflecting smoking-induced inflammation. Interpretations of quantitative CT data within clinical trials should consider smoking status. • Lung density is higher in active smokers than ex-smokers. • Lung density sustainably decreases after smoking cessation. • Impact of smoking cessation on lung density is independent of potentially confounding factors. • Smoke-induced pulmonary inflammation and particle deposition influence lung density on CT.

A new method for predicting uric acid composition in urinary stones using routine single-energy CT

Urinary stones composed of uric acid can be treated medically. Prediction of uric acid stone type is, therefore, desirable when a urinary stone is diagnosed with unenhanced CT. The purpose of the present study was to describe single-energy thin slice quantitative CT parameters of urinary stones correlated to chemical stone type and to develop a method to distinguish pure uric acid stones (UA) from other stones (non-UA/Mix). Unenhanced thin slice single-energy CT images of 126 urinary stones (117 patients) with known chemical stone type were retrospectively included in the study. Among the included stones, 22 were UA and 104 were non-UA/Mix. The included CT images and Laplacian filtered images of the stones were quantitatively analyzed using operator-independent methods. A post hoc classification method for pure UA stones was created using a combination of cutoff values for the peak attenuation and peak point Laplacian. The stone types differed in most quantitative image characteristics including mean attenuation (p < 0.001), peak attenuation (p < 0.001), and peak point Laplacian (p < 0.001). The sensitivity for the post hoc-developed peak attenuation—peak point Laplacian method for classifying pure UA stones was 95% [21/22, 95% CI (77–100%)] and the specificity was 99% [103/104, 95% CI (95–100%)]. In conclusion, quantitative image analysis of thin slice routine single-energy CT images is promising for predicting pure UA content in urinary stones, with results comparable to double energy methods.

Tumor invasiveness defined by IASLC/ATS/ERS classification of ground-glass nodules can be predicted by quantitative CT parameters.

To investigate the potential value of CT parameters to differentiate ground-glass nodules between noninvasive adenocarcinoma and invasive pulmonary adenocarcinoma (IPA) as defined by IASLC/ATS/ERS classification. We retrospectively reviewed 211 patients with pathologically proved stage 0-IA lung adenocarcinoma which appeared as subsolid nodules, from January 2012 to January 2013 including 137 pure ground glass nodules (pGGNs) and 74 part-solid nodules (PSNs). Pathological data was classified under the 2011 IASLC/ATS/ERS classification. Both quantitative and qualitative CT parameters were used to determine the tumor invasiveness between noninvasive adenocarcinomas and IPAs. There were 154 noninvasive adenocarcinomas and 57 IPAs. In pGGNs, CT size and area, one-dimensional mean CT value and bubble lucency were significantly different between noninvasive adenocarcinomas and IPAs on univariate analysis. Multivariate regression and ROC analysis revealed that CT size and one-dimensional mean CT value were predictive of noninvasive adenocarcinomas compared to IPAs. Optimal cutoff value was 13.60 mm (sensitivity, 75.0%; specificity, 99.6%), and -583.60 HU (sensitivity, 68.8%; specificity, 66.9%). In PSNs, there were significant differences in CT size and area, solid component area, solid proportion, one-dimensional mean and maximum CT value, three-dimensional (3D) mean CT value between noninvasive adenocarcinomas and IPAs on univariate analysis. Multivariate and ROC analysis showed that CT size and 3D mean CT value were significantly differentiators. Optimal cutoff value was 19.64 mm (sensitivity, 53.7%; specificity, 93.9%), -571.63 HU (sensitivity, 85.4%; specificity, 75.8%). For pGGNs, CT size and one-dimensional mean CT value are determinants for tumor invasiveness. For PSNs, tumor invasiveness can be predicted by CT size and 3D mean CT value.

Longitudinal shape irregularity of airway lumen assessed by CT in patients with bronchial asthma and COPD

BackgroundAirway remodelling in bronchial asthma (BA) and COPD has been quantitatively assessed by analysing the airway wall area and the luminal area on cross-sectional CT images. To date, there have...

Differentiating malignant vertebral tumours from non-malignancies with CT spectral imaging: a preliminary study.

To investigate the value of dual-energy spectral computed tomography (DESCT) for differentiating malignant vertebral tumours from non-malignancies during venous phase. This study was institutional review board-approved, and written informed consent was obtained from all patients. Thirty-seven patients were examined by DESCT during venous phase. Twenty patients had malignant vertebral tumours, 17 had non-malignant vertebral tumours. The iodine/water densities for the lesion, the lesion-to-muscle ratio, and lesion-to-artery ratio for iodine density measurements were calculated and compared between the two groups with the two-tailed Student t test. A p-value < 0.05 was considered statistically significant. Sensitivity and specificity were compared between the qualitative and quantitative studies. The iodine density, lesion-to-muscle ratio, and lesion-to-artery ratio of the iodine density measurement for malignant vertebral tumours were significantly different from the respective values for non-malignancies (all p < 0.05). Using 0.52 as the threshold value for the lesion-to-artery iodine density ratio, one could obtain sensitivity of 85% and specificity of 100% for differentiating malignant vertebral tumours from non-malignancies, significantly higher than the qualitative diagnosis. DESCT imaging enables analysis of a number of additional quantitative CT parameters to improve the accuracy for differentiating malignant vertebral tumours from non-malignancies during venous phase. • Dual-energy CT provides a new quantitative method. • CT spectral imaging improves the accuracy of differential diagnosis. • Lesion-to-artery iodine density ratio for malignant vertebral tumours was higher than for non-malignancies.

Relationships between diffusing capacity for carbon monoxide (DLCO), and quantitative computed tomography measurements and visual assessment for chronic obstructive pulmonary disease

PurposeTo evaluate the relationships between DLCO, and Quantitative CT (QCT) measurements and visual assessment of pulmonary emphysema and to test the relative roles of visual and quantitative assessment of emphysema. Materials and methodsThe subjects included 199 current and former cigarette smokers from the COPDGene cohort who underwent inspiratory and expiratory CT and also had diffusing capacity for carbon monoxide corrected for alveolar volume (DLCO/VA). Quantitative CT measurements included % low attenuation areas (%LAA−950ins=voxels ≤−950Hounsfield unit (HU), % LAA−910ins, and % LAA−856ins), mean CT attenuation and 15th percentile HU value on inspiratory CT, and %LAA−856exp (voxels ≤−856HU on expiratory CT). The extent of emphysema was visually assessed using a 5-point grading system. Univariate and multiple variable linear regression analyses were employed to evaluate the correlations between DLCO/VA and QCT parameters and visual extent of emphysema. ResultsThe DLCO/VA correlated most strongly with 15th percentile HU (R2=0.440, p<0.001) closely followed by % LAA−950ins (R2=0.417, p<0.001) and visual extent of emphysema (R2=0.411, p<0.001). Multiple variable analysis showed that visual extent of emphysema and 15th percentile HU were independent significant predictors of DLCO/VA at an R2 of 0.599. Conclusions15th percentile HU seems the best parameter to represent the respiratory condition of COPD. Visual and Quantitative CT assessment of emphysema provide complementary information to QCT analysis.

Combined Evaluation of FDG-PET/CT and CT Imaging Characteristics of Cervical Lymph Nodes to Increase the Interpretation Accuracy for Nodal Metastatic Involvement in Head and Neck Cancer

Rationale and objectives: Accurate staging of regional lymph nodes in patient with head and neck squamous cell carcinoma (HNSCC) has important therapeutic and prognostic implications. The objective of this study was to assess qualitative and quantitative imaging characteristics of cervical lymph nodes on FDG PET/CT and contrast enhanced CT (CECT), either alone or in cross-modality combinations, for more accurate diagnosis of nodal metastatic involvement in HNSCC patients who had hypermetabolic cervical lymph nodes on PET/CT imaging. Materials and methods: Lymph nodes were evaluated using quantitative PET/CT parameters (SUVmax, SUVmean, metabolic tumor volume, total lesion glycolysis) and qualitative and quantitative CT parameters (shape, margin, focal hypoattenuation, fatty hilum, short axis, long axis, volume, eccentricity factor). A subset analysis was performed on FDG-avid lymph nodes that lacked imaging findings suggestive of extracapsular spread or necrosis. Statistical outcomes included sensitivity, specificity, accuracy, positive likelihood ratio, and odds ratio. Results: In the full cohort (174 nodes), the most malignancy specific parameters were ill-defined margin and focal hypoattenuation, and the most accurate variables included SUVmax, SUVmean, ill-defined margin, short axis, and focal hypoattenuation. On multivariate analysis, ill-defined margin, short axis measurement, and SUVmax independently predicted nodal metastasis. In the subgroup of smaller lymph nodes without ill-defined margin or focal hypoattenuation (100 nodes), round shape was among the most accurate and specific criteria for malignancy. Cross-modality combination criteria with SUVmax and shape, eccentricity factor, or long to short axis ratio resulted in statistically significant improvements in specificity and accuracy for lymph node metastasis. Conclusion: A combined evaluation strategy using individual PET/CT and CECT characteristics in cross modality combinations, particularly SUVmax with round shape on axial imaging or with loss of eccentricity, can improve diagnostic accuracy of malignant nodal involvement in the evaluation of indeterminate cervical lymph nodes for malignancy.

Quantitative CT analysis of pulmonary ground-glass opacity nodules for the distinction of invasive adenocarcinoma from pre-invasive or minimally invasive adenocarcinoma.

ObjectivesWe aimed to analyze the CT findings of ground-glass opacity nodules diagnosed pathologically as adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma in order to investigate whether quantitative CT parameters enable distinction of invasive adenocarcinoma from pre-invasive or minimally invasive adenocarcinoma.MethodsWe reviewed CT images and pathologic specimens from 191 resected ground-glass opacity nodules with little or no solid component at CT. Nodule size, volume, density, mass, skewness/kurtosis, and CT attenuation values at the 2.5th–97.5th percentiles on histogram, and texture parameters (uniformity and entropy) were assessed from CT datasets.ResultsOf 191 tumors, 38 were AISs (20%), 61 were MIAs (32%), and 92 (48%) were invasive adenocarcinomas. Multivariate logistic regression analysis helped identify the 75th percentile CT attenuation value (P = 0.04) and entropy (P<0.01) as independent predictors for invasive adenocarcinoma, with an area under the receiver operating characteristic curve of 0.780.ConclusionQuantitative analysis of preoperative CT imaging metrics can help distinguish invasive adenocarcinoma from pre-invasive or minimally invasive adenocarcinoma.

Effect of Slice Thickness Reconstruction on Quantitative Vascular Parameters in Perfusion CT

Objective: The purpose of this study was to determine how the slice thickness reconstruction influences quantitative perfusion CT parameters. Materials and Methods: Eighteen patients with cancer (15 non-small-cell lung cancer, 2 rectal cancer and 1 renal cancer) were examined prospectively with multidetector row CT. A 90-second perfusion study was performed after intravenous bolus injection of contrast material. Blood flow, blood volume, mean transit time and permeability-surface area product were determined at three different slice thickness reconstruction (1.25, 2.5 and 5 mms) both in tumors and in paraspinal muscle. Mean values, limits of agreement between measurements and within-subject coefficient of correlation were obtained for these thicknesses. Results: Mean ± standard deviation BF, BV, MTT and PS in lesions were 118.7 ± 117.9 mL/min/100g tissue, 8.2 ± 8.2 mL/100g tissue, 7.5 ± 5.4 seconds and 10.3 ± 7.2 mL/min/100g tissue respectively at1.25 mmslice thickness; 116.1 ± 115.7 mL/min/100g tissue, 7.8 ± 8.7 mL/100g tissue, 7 ± 4.5 seconds and 10.4 ± 7.5 mL/min/100g tissue at 2.5 mms; and 119.6 ± 115.7 mL/min/100g tissue, 7.8 ± 8.8 mL/100g tissue, 5.4 ± 3.4 seconds and 9.6 ± 7.5 mL/min/100g tissue at 5 mms. Differences between means for different slice thickness where relatively small in all parameters (<15%) except in MTT where difference was up to 37%. 95% limits of agreement were worse when comparing more different slice thicknesses (e.g. 1.25 vs 5 mms) than when comparing more close slice thicknesses (1.25 vs 2.5 mms or 2.5 vs 5 mms). Conclusions: There is a significant variability in perfusion parameter measurements at different slice thickness reconstruction, particularly in MTT. The more close together the slice thicknesses were, the smaller was the variability.

AB0606 Effects of 12-month etanercept or certolizumab pegol therapy on disease activity, bone turnover markers and peripheral qct bone mineral density in patients with rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) has been associated with secondary bone loss in the majority of patients. Biologics may have effects on generalized bone loss, however, less information has become available on...

Racial Differences in CT Phenotypes in COPD

Background: Whether African Americans (AA) are more susceptible to COPD than non-Hispanic Whites (NHW) and whether racial differences in disease phenotype exist is controversial. The objective is to determine racial differences in the extent of emphysema and airway remodeling in COPD. Methods: First, 2,500 subjects enrolled in the COPDGene study were used to evaluate racial differences in quantitative CT (QCT) parameters of% emphysema, air trapping and airway wall thickness. Independent variables studied included race, age, gender, education, BMI, pack-years, smoking status, age at smoking initiation, asthma, previous work in dusty job, CT scanner and center of recruitment. Results: Of the 1,063 subjects with GOLD Stage II-IV COPD, 200 self-reported as AA. AAs had a lower mean% emphysema (13.1% vs. 16.1%, p = 0.005) than NHW and proportionately less emphysema in the lower lung zones. After adjustment for covariates, there was no statistical difference by race in air trapping or airway wall thickness. Measured QCT parameters were more predictive of poor functional status in NHWs compared to AAs. Conclusions: AAs have less emphysema than NHWs but the same degree of airway disease. Additional factors not easily assessed by current QCT techniques may account for the poor functional status in AAs.

Prediction of adverse clinical outcome in patients with acute pulmonary embolism: Evaluation of High-Sensitivity Troponin I and quantitative CT parameters

PurposeTo evaluate the accuracy of high-sensitivity-cardiac-troponin-I (hs-cTnI) and quantitative CT-parameters, alone and in combination, for predicting right-ventricular-dysfunction (RVD) and adverse clinical outcome in patients with acute pulmonary embolism (PE). Materials and methods65 patients with PE and hs-cTnI measurements within 24h of CT were retrospectively included. RVD was assessed on CT by calculating right ventricular/left ventricular (RV/LV) diameter ratios on transverse sections (RV/LVtrans), four-chamber-views (RV/LV4ch), and RV/LV volume ratio (RV/LVvol). Pulmonary CTA-obstruction-scores (OS) (Qanadli, Mastora) were calculated. Receiver operator characteristic (ROC) analysis was performed to compare Hs-cTnI, RV/LV ratios, and OS for predicting adverse clinical outcome (i.e. intensive care treatment, death). Results12 patients with PE had adverse clinical outcome and showed significantly higher RV/LV ratios and OS compared to those without. ROC analysis revealed a cutoff value of 0.042ng/mL for hs-cTnI resulting in a sensitivity and specificity of 84% and 92% for predicting adverse clinical outcome, respectively. Elevated hs-cTnI was significantly associated with adverse clinical outcome. In a ROC analysis the AUC for the prediction of adverse clinical outcome of RV/LV4Ch, RV/LVvol, and hs-cTnI were 0.77, 0.76, and 0.71. The combination of hs-cTnI and RV/LV ratios increased the AUC for the prediction of adverse clinical outcome. ConclusionsHs-cTnI is associated with adverse clinical outcome in patients with acute PE. A combination of hs-cTnI with quantitative CT-parameters improves the prediction of adverse clinical outcome.

Benefit of combining quantitative cardiac CT parameters with troponin I for predicting right ventricular dysfunction and adverse clinical events in patients with acute pulmonary embolism

ObjectiveTo prospectively evaluate the diagnostic accuracy of quantitative cardiac CT parameters alone and in combination with troponin I for the assessment of right ventricular dysfunction (RVD) and adverse clinical events in patients with acute pulmonary embolism (PE). Materials and resultsThis prospective study had institutional review board approval and was HIPAA compliant. In total 83 patients with confirmed PE underwent echocardiography and troponin I serum level measurements within 24h. Three established cardiac CT measurements for the assessment of RVD were obtained (RV/LVaxial, RV/LV4-CH, and RV/LVvolume). CT measurements and troponin I serum levels were correlated with RVD found on echocardiography and adverse clinical events according to Management Strategies and Prognosis in Pulmonary Embolism Trial-3 (MAPPET-3 criteria. 31 of 83 patients with PE had RVD on echocardiography and 39 of 83 patients had adverse clinical events. A RV/LVvolume ratio>1.43 showed the highest area under the curve (AUC) (0.65) for the prediction of adverse clinical events when compared to RV/LVaxial, RV/LV4Ch and troponin I. The AUC for the detection of RVD of RV/LVaxial, RV/LV4Ch, RV/LVvolume, and troponin I were 0.86, 0.86, 0.92, and 0.69, respectively. Combination of RV/LVaxial, RV/LV4Ch, RV/LVvolume with troponin I increased the AUC to 0.87, 0.87 and 0.93, respectively. ConclusionA combination of cardiac CT parameters and troponin I measurements improves the diagnostic accuracy for detecting RVD and predicting adverse clinical events if compared to either test alone.

Extrapolation in the analysis of lung aeration by computed tomography: a validation study

IntroductionComputed tomography (CT) is considered the gold standard for quantification of global or regional lung aeration and lung mass. Quantitative CT, however, involves the exposure to ionizing radiation and requires manual image processing. We recently evaluated an extrapolation method which calculates quantitative CT parameters characterizing the entire lung from only 10 reference CT-slices thereby reducing radiation exposure and analysis time. We hypothesized that this extrapolation method could be further validated using CT-data from pigs and sheep, which have a different thoracic anatomy.MethodsWe quantified volume and mass of the total lung and differently aerated lung compartments in 168 ovine and 55 porcine whole-lung CTs covering lung conditions from normal to gross deaeration. Extrapolated volume and mass parameters were compared to the respective values obtained by whole-lung analysis. We also tested the accuracy of extrapolation for all possible numbers of CT slices between 15 and 5. Bias and limits of agreement (LOA) were analyzed by the Bland-Altman method.ResultsFor extrapolation from 10 reference slices, bias (LOA) for the total lung volume and mass of sheep were 18.4 (-57.2 to 94.0) ml and 4.2 (-21.8 to 30.2) grams, respectively. The corresponding bias (LOA) values for pigs were 5.1 (-55.2 to 65.3) ml and 1.6 (-32.9 to 36.2) grams, respectively. All bias values for differently aerated lung compartments were below 1% of the total lung volume or mass and the LOA never exceeded ± 2.5%. Bias values diverged from zero and the LOA became considerably wider when less than 10 reference slices were used.ConclusionsThe extrapolation method appears robust against variations in thoracic anatomy, which further supports its accuracy and potential usefulness for clinical and experimental application of quantitative CT.

Diagnostic value of computed tomographic findings of nutcracker syndrome: Correlation with renal venography and renocaval pressure gradients

To evaluate the diagnostic values of CT findings of nutcracker syndrome (NCS). Twenty seven subjects that underwent CT and renal venography, were divided into three groups based on the venographic renocaval pressure gradient (PG) and collateral veins of the left renal vein (LRV): non-compensated NCS patients with PG≥3 mm Hg (group 1, n=12), partially compensated NCS patients with borderline PG (1<3 mm Hg) and collateral veins (group 2, n=6), and control group with low PG (0-1 mm Hg) without collateral veins (group 3, n=9). The CT findings were analyzed with regard to abrupt narrowing of the LRV with an acute angle (beak sign), aortomesenteric angle between the superior mesenteric artery and aorta on sagittal images, and LRV diameter ratio (hilar-aortomesenteric). Beak sign of the LRV was found in 91.7% (11/12) of group 1, 50% (3/6) of group 2, and in 11.1% (1/9) of group 3 with the significant difference between groups 1 and 3 (P<.05, χ2 test). Mean values of all quantitative CT parameters differed significantly only between groups 1 and 3 (P<.05, one-way ANOVA test). For differentiating the non-compensated NCS from the control group, the beak sign showed 91.7% sensitivity and 88.9% specificity. Of the various CT parameters, the beak sign and LRV diameter ratio of ≥4.9 showed the greatest diagnostic accuracy (AUC 0.903, ROC analysis). Beak sign of the LRV and CT findings can be useful in diagnosing the non-compensated NCS.

Quantitatively assessed CT imaging measures of pulmonary interstitial pneumonia: Effects of reconstruction algorithms on histogram parameters

This study aimed the influences of reconstruction algorithm for quantitative assessments in interstitial pneumonia patients. A total of 25 collagen vascular disease patients (nine male patients and 16 female patients; mean age, 57.2 years; age range 32–77 years) underwent thin-section MDCT examinations, and MDCT data were reconstructed with three kinds of reconstruction algorithm (two high-frequencies [ A and B] and one standard [ C]). In reconstruction algorithm B, the effect of low- and middle-frequency space was suppressed compared with reconstruction algorithm A. As quantitative CT parameters, kurtosis, skewness, and mean lung density (MLD) were acquired from a frequency histogram of the whole lung parenchyma in each reconstruction algorithm. To determine the difference of quantitative CT parameters affected by reconstruction algorithms, these parameters were compared statistically. To determine the relationships with the disease severity, these parameters were correlated with PFTs. In the results, all the histogram parameters values had significant differences each other ( p < 0.0001) and those of reconstruction algorithm C were the highest. All MLDs had fair or moderate correlation with all parameters of PFT (−0.64 < r < −0.45, p < 0.05). Though kurtosis and skewness in high-frequency reconstruction algorithm A had significant correlations with all parameters of PFT (−0.61 < r < −0.45, p < 0.05), there were significant correlations only with diffusing capacity of carbon monoxide (DLco) and total lung capacity (TLC) in reconstruction algorithm C and with forced expiratory volume in 1 s (FEV1), DLco and TLC in reconstruction algorithm B. In conclusion, reconstruction algorithm has influence to quantitative assessments on chest thin-section MDCT examination in interstitial pneumonia patients.

Longitudinal follow-up study of smoking-induced lung density changes by high-resolution computed tomography.

To evaluate the ability of high-resolution computed tomography (HRCT) to detect longitudinal changes in structural abnormalities caused by smoking, HRCT and pulmonary function tests were used to examine nonsmokers, current smokers, and past smokers annually for 5 yr. Inspiratory HRCT was taken for the upper, middle, and lower lung fields, while expiratory images were obtained for the upper and lower lung fields only. We estimated the three quantitative CT parameters including MLD (mean CT value), HIST (CT value with the most frequent appearance), and %LAA (relative area of low attenuation with CT values less than -912 HU). Most of the pulmonary function tests, excepting FEV(1), did not change annually, whereas many of the inspiratory HRCT parameters did. In nonsmokers, only %LAA in the middle or lower lung fields exhibited an annual increase. In current smokers, %LAA in the upper lung field was augmented, while inspiratory MLD or HIST in the middle or lower lung field became more positive. In past smokers, %LAA in any lung field examined increased. The annual change in %LAA in the upper lung field was larger for past smokers than nonsmokers, with little difference between past and current smokers. Expiratory CT parameters showed few annual changes in all groups. In conclusion, (1) aging increases airspace abnormalities, mainly in the lower lung field; (2) although continuous smoking worsens airspace abnormalities mainly in the upper portion of the lung, this trend does not seem to slow down even after smoking cessation; and (3) inspiratory HRCT images are superior to expiratory images for longitudinal estimation of structural abnormalities caused by aging and smoking.