Pierre-Alain Gevenois

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.

Respiratory effects of the external and internal intercostal muscles in humans

1 The current conventional view of intercostal muscle actions is based on the theory of Hamberger (1749) and maintains that as a result of the orientation of the muscle fibres, the external intercostals have an inspiratory action on the lung and the internal interosseous intercostals have an expiratory action. Recent studies in dogs, however, have shown that this notion is only approximate. 2 In the present studies, the respiratory actions of the human external and internal intercostal muscles were evaluated by applying the Maxwell reciprocity theorem. Thus the orientation of the muscle fibres relative to the ribs and the masses of the muscles were first assessed in cadavers. Five healthy individuals were then placed in a computed tomographic scanner to determine the geometry of the ribs and their precise transformation during passive inflation to total lung capacity. The fractional changes in length of lines with the orientation of the muscle fibres were then computed to obtain the mechanical advantages of the muscles. These values were finally multiplied by muscle mass and maximum active stress (3.0 kg cm−2) to evaluate the potential effects of the muscles on the lung. 3 The external intercostal in the dorsal half of the second interspace was found to have a large inspiratory effect. However, this effect decreases rapidly in the caudal direction, in particular in the ventral portion of the ribcage. As a result, it is reversed into an expiratory effect in the ventral half of the sixth and eighth interspaces. 4 The internal intercostals in the ventral half of the sixth and eighth interspaces have a large expiratory effect, but this effect decreases dorsally and cranially. 5 The total pressure generated by all the external intercostals during a maximum contraction would be ‐15 cmH2O, and that generated by all the internal interosseous intercostals would be +40 cmH2O. These pressure changes are substantially greater than those induced by the parasternal intercostal and triangularis sterni muscles, respectively.

CT-Definable Subtypes of Chronic Obstructive Pulmonary Disease: A Statement of the Fleischner Society

The purpose of this statement is to describe and define the phenotypic abnormalities that can be identified on visual and quantitative evaluation of computed tomographic (CT) images in subjects with chronic obstructive pulmonary disease (COPD), with the goal of contributing to a personalized approach to the treatment of patients with COPD. Quantitative CT is useful for identifying and sequentially evaluating the extent of emphysematous lung destruction, changes in airway walls, and expiratory air trapping. However, visual assessment of CT scans remains important to describe patterns of altered lung structure in COPD. The classification system proposed and illustrated in this article provides a structured approach to visual and quantitative assessment of COPD. Emphysema is classified as centrilobular (subclassified as trace, mild, moderate, confluent, and advanced destructive emphysema), panlobular, and paraseptal (subclassified as mild or substantial). Additional important visual features include airway wall thickening, inflammatory small airways disease, tracheal abnormalities, interstitial lung abnormalities, pulmonary arterial enlargement, and bronchiectasis.

Acute and long term respiratory damage following inhalation of ammonia.

A lifelong non-smoker who was the victim of a massive accidental exposure to anhydrous ammonia gas was followed up for 10 years. In the acute phase the patient presented with severe tracheobronchitis and respiratory failure, caused by very severe burns of the respiratory mucosa. After some improvement he was left with severe and fixed airways obstruction. Isotope studies of mucociliary clearance, computed tomography, and bronchography showed mild bronchiectasis. It is concluded that acute exposure to high concentrations of ammonia may lead to acute respiratory injury but also to long term impairment of respiratory function.

Mechanical advantage of the human parasternal intercostal and triangularis sterni muscles

1 Previous studies in dogs have demonstrated that the maximum change in airway pressure (ΔPao) produced by a particular respiratory muscle is the product of three factors, namely the mass of the muscle, the maximal active muscle tension per unit cross‐sectional area (∼3.0 kg cm−2), and the fractional change in muscle length per unit volume increase of the relaxed chest wall (i.e. the muscles mechanical advantage). In the present studies, we have used this principle to infer the ΔPao values generated by the parasternal intercostal and triangularis sterni muscles in man. 2 The mass of the muscles and the direction of the muscle fibres relative to the sternum were first assessed in six cadavers. Seven healthy individuals were then placed in a computed tomographic scanner to determine the orientation of the costal cartilages relative to the sternum and their rotation during passive inflation to total lung capacity. The fractional changes in length of the muscles during inflation, their mechanical advantages, and their ΔPao values were then calculated. 3 Passive inflation induced shortening of the parasternal intercostals in all interspaces and lengthening of the triangularis sterni. The fractional shortening of the parasternal intercostals decreased gradually from 7.7% in the second interspace to 2.0% in the fifth, whereas the fractional lengthening of the triangularis sterni increased progressively from 5.9 to 13.8%. These rostrocaudal gradients were well accounted for by the more caudal orientation of the cartilages of the lower ribs. 4 Since these fractional changes in length corresponded to a maximal inflation, the inspiratory mechanical advantage of the parasternal intercostals was only 2.2–0.6% l−1, and the expiratory mechanical advantage of the triangularis sterni was only 1.6–3.8% l−1. In addition, whatever the interspace, parasternal and triangularis muscle mass was 3–5 and 1–3 g, respectively. As a result, the magnitude of the ΔPao values generated by a maximal contraction of the parasternal intercostals or triangularis sterni in all interspaces would be only 1–3 cmH2O. 5 These studies therefore confirm that the parasternal intercostals in man have an inspiratory action on the lung whereas the triangularis sterni has an expiratory action. However, these studies also establish the important fact that the pressure‐generating ability of both muscles is substantially smaller than in the dog.

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.

MDCT for suspected acute appendicitis in adults: Impact of oral and IV contrast media at standard-dose and simulated low-dose techniques

OBJECTIVE The objective of this study was to prospectively investigate the influence of oral, IV, and oral and IV contrast media on the information provided by MDCT at standard and simulated low radiation doses in adults suspected of having acute appendicitis. SUBJECTS AND METHODS One hundred thirty-one consecutive patients (80 women, 51 men; age range, 18-87 years; mean age, 37 years) suspected of having appendicitis were randomly assigned to either ingest or not ingest iodinated contrast material. Thereafter, all patients underwent IV unenhanced and enhanced abdominopelvic MDCT with a 4 x 2.5 mm collimation at 120 kVp and 100 mAs(eff). Dose reduction corresponding to 30 mAs(eff) was simulated. Two radiologists independently read scans during separate sessions, assessed appendix visualization, and proposed a diagnosis (i.e., appendicitis or an alternative diagnosis). The final diagnosis was based on either surgical findings or clinical follow-up. Data were analyzed by factorial analysis of multiple correspondences followed by an ascending hierarchic classification method. RESULTS Factorial analysis and ascending hierarchic classification revealed that, in terms of diagnostic correctness, reader influence predominated over the influence of IV and oral contrast media use and radiation dose but that correctness was also influenced by the patients sex (p = 0.048) and was lower in cases of alternative diseases (p < 0.001). Visualization of the appendix depended predominantly on the reader rather than on the use of IV, oral, or oral and IV contrast agents or on radiation dose. CONCLUSION Diagnostic correctness is much more influenced by the reader than by the use of contrast medium (oral, IV, or both) or of simulated low-radiation-dose technique.

Radiation dose from adult and pediatric multidetector computed tomography

Introduction: Clincical Expansion of CT and Radiation Dose Part I: Radiation Risks in Multidetector CT: Risks from Ionizing Radiations The Linear-No-Threshold Theory: Background and Limitations CT Parameters that Influence the Radiation Dose Collective Radiation Dose from MDCT: Critial Review and Survey Studies Methods for Reducing the Radiation Dose from MDCT Including Image Quality Automatic Exposure Control in Multidetector-Row CT Patient Centering and CT Radiation Dose Part II: Clinical Approaches of Dose Optimization, and Reduction: Dose Optimization and Reduction in CT of Head and Neck Including Brain Dose Optimization and Reduction in CT of the Chest Dose Optimization and Reduction in CT of the Abdomen Dose Optimization and Reduction in CT Angiography and Cardiac CT Dose Optimization and Reduction in CT of the Musculoskeletal System Including the Spine Dose Reduction in CT Fluoroscopy Dose Optimization and Reduction in CT of Children Radiation Risk Management in Low Dose MDCT Screening Programs Subject Index List of Contributors.

Micronodules and emphysema in coal mine dust or silica exposure: relation with lung function

The aim of this study was to investigate the respective effects of micronodules and pulmonary emphysema, detected by computed tomography (CT), on lung function in workers exposed to silica and coal mine dust. Eighty-three subjects exposed to silica (n=35) or to coal mine dust (n=48), without progressive massive fibrosis, were investigated by high-resolution and conventional CT scans to detect micronodules and to quantify pulmonary emphysema by measuring the relative area of the lung with attenuation values lower than -950 Hounsfield units. Sixty-six (54.5%) subjects had evidence of micronodules on CT scans. Smokers had micronodules more rarely than nonsmokers. Significant correlations were found between the forced expiratory volume in one second (FEV(1); % predicted) (r=-0.41, p<0.001), FEV1/vital capacity (VC) (r=-0.61, p<0.001), diffusing capacity of the lung for carbon monoxide (DL,CO) (r=-0.36, p<0.001) and the extent of emphysema. No difference was demonstrated in the linear relationships between the extent of emphysema and the pulmonary function according to the type of exposure or the presence of micronodules on CT scans. This study suggests that micronodules detected by computed tomography have no influence, by themselves, on pulmonary function and that they should only be considered as a marker of exposure.