Afarine Madani

Quantitative computed tomography assessment of lung structure and function in pulmonary emphysema

Accurate diagnosis and quantification of pulmonary emphysema during life is important to understand the natural history of the disease, to assess the extent of the disease, and to evaluate and follow-up therapeutic interventions. Since pulmonary emphysema is defined through pathological criteria, new methods of diagnosis and quantification should be validated by comparisons against histological references. Recent studies have addressed the capability of computed tomography (CT) to quantify pulmonary emphysema accurately. The studies reviewed in this article have been based on CT scans obtained after deep inspiration or expiration, on subjective visual grading and on objective measurements of attenuation values. Especially dedicated software was used for this purpose, which provided numerical data, on both two- and three-dimensional approaches, and compared CT data with pulmonary function tests. More recently, fractal and textural analyses were applied to computed tomography scans to assess the presence, the extent, and the types of emphysema. Quantitative computed tomography has already been used in patient selection for surgical treatment of pulmonary emphysema and in pharmacotherapeutical trials. However, despite numerous and extensive studies, this technique has not yet been standardized and important questions about how best to use computed tomography for the quantification of pulmonary emphysema are still unsolved.

Asbestosis, pleural plaques and diffuse pleural thickening: three distinct benign responses to asbestos exposure

The aim of this study was to investigate by computed tomography (CT) whether asbestosis, diffuse pleural thickening and/or pleural plaques are statistically associated. We also tried to find criteria to differentiate between diffuse and circumscribed pleural thickening. From 231 exposed workers, only those subjects whose radiograph showed neither bilateral calcified pleural plaques nor small pulmonary opacities higher than 1/1 grade according to the 1980 International Labour Office (ILO) Classification were considered. Scans were assessed for the presence of subpleural curvilinear lines, septal and intralobular lines, parenchymal bands, honeycombing, rounded atelectasis, pleural plaques and diffuse pleural thickening. CT scans revealed pleural and/or lung abnormalities in 99 workers. Pleural plaques were unilateral in one-third of cases with plaques. Diffuse pleural thickening, parenchymal bands and rounded atelectasis were unilateral in, respectively, 62 and 69 and 75% of cases with the abnormality. Septal and intralobular lines, and honeycombing were always bilateral. CT signs could be grouped into three patterns: 1) septal and intralobular lines, and honeycombing corresponding to pulmonary fibrosis; 2) pleural plaques corresponding to parietal pleural fibrosis; and 3) diffuse pleural thickening, rounded atelectasis and parenchymal bands corresponding to visceral pleural fibrosis. In these workers with a normal or near-normal radiograph, three groups of subjects with different responses were distinguished. Crows feet and rounded atelectasis help to differentiate plaques from diffuse thickening.

Pulmonary Emphysema: Size Distribution of Emphysematous Spaces on Multidetector CT Images—Comparison with Macroscopic and Microscopic Morphometry

PURPOSE To test the hypothesis that the frequency-size distribution of low-attenuation areas could be a parameter to quantify pulmonary emphysema. MATERIALS AND METHODS Ethics committee approval and written informed consent were obtained. Multidetector computed tomographic (CT) scans were performed with simultaneous acquisition of four 1-mm sections of the whole chest in 80 patients (57 men, 23 women; age range, 38-79 years) who were referred for surgical resection of lung cancer. From the raw data, 1.25-mm-thick sections were reconstructed at 10-mm intervals. The relative area of lung with attenuation coefficients lower than -960 HU (RA(960)) and the 1st percentile of the distribution of attenuation coefficients were calculated. The cumulative frequency-size distributions of the RA(960) and the 1st percentile, when represented on a log-log plot, followed linear relationships. The slopes of these lines (D(960) and D(p1)) were compared with areas found macroscopically to have emphysema and with two different microscopic measurements assessed on resected specimens. Spearman correlation coefficients of each CT index with macroscopic and microscopic measurements were calculated. RESULTS The RA(960) and the 1st percentile showed statistically significant correlations with macroscopic and microscopic indexes (P < .001), whereas D(960) and D(p1) did not (P > or = .165). CONCLUSION The RA(960) and the 1st percentile reflect the extent of emphysema as compared to macroscopic and microscopic measurements, while D(960) and D(p1) do not.

Pulmonary Emphysema: Effect of Lung Volume on Objective Quantification at Thin-Section CT

PURPOSE To prospectively investigate the effect of submaximal inspiration on computed tomographic (CT) indexes used to quantify emphysema and to discriminate between effects of lung tissue loss and increase in total lung capacity (TLC) on these indexes. MATERIALS AND METHODS In this ethical committee-approved study, 20 control subjects and 16 patients with chronic obstructive pulmonary disease (COPD) who provided written informed consent were included. Three 1-mm-thick sections were obtained from each participant at 100%, 90%, 80%, 70%, and 50% of vital capacity (VC). At each volume, eight percentiles of attenuation distribution, as well as relative area (RA) of lung occupied by attenuation coefficients lower than nine thresholds, were calculated. A linear regression line between TLC and each CT index was plotted for control subjects. Mean distance from data points measured in patients with COPD to the normal regression line was used to reflect the effect of lung tissue loss, regardless of TLC. RESULTS The RA of lung occupied by attenuation coefficients lower than -950 HU (RA(950)) at any percentage of VC lower than 100% decreased significantly from that at 100% VC (P ≤ .002) in control subjects and patients with COPD; however, between 100% VC and 90% VC, the average difference in RA(950) was only 3% and 2% in control subjects and patients with COPD, respectively. The 1st percentile at any percentage of VC lower than 100% increased from that at 100% VC (P < .001) in control subjects. This percentile did not significantly differ from 100% VC at 90% VC or 80% VC (P = .176 and P = 0.077, respectively), but it did significantly differ from 100% VC at 70% VC and 50% VC (P ≤ .002 for both) in patients with COPD. Slope and mean distance were different from zero for all RAs and percentiles except for mean distance for RAs between RA(900) and RA(920). CONCLUSION Submaximal inspiration induces underestimation of pulmonary emphysema. Both lung tissue loss and TLC influence CT indexes, suggesting the need to establish normal CT values.

CT quantification of pulmonary emphysema: assessment of lung structure and function.

Accurate diagnosis and quantification of pulmonary emphysema in vivo is important to understand the natural history of the disease, to assess the extent of the disease, and to evaluate and follow-up therapeutic interventions. Because pulmonary emphysema is defined by pathology, new diagnostic methods for quantification should be validated by reference to pathological and histological standards. Recent studies have addressed the capability of computed tomography (CT) to accurately quantify pulmonary emphysema. These studies that have been overviewed in this article have been based on CT scans obtained after deep inspiration or expiration, on subjective visual grading, and on objective measurements of attenuation values by using dedicated software providing numerical data on two-dimensional and on three-dimensional approaches, and compared CT data with pulmonary function tests. More recently, fractal and textural analyses were applied to CT scans to assess the presence, extent, and types of emphysema. Quantitative CT has already been used in patient selection for surgical treatment of pulmonary emphysema and in pharmacotherapeutical trials. However, despite numerous and extensive studies already available, this technique has not yet been standardized, and important questions about how to best use CT for the quantification of pulmonary emphysema remain to be addressed.