Expiratory Computed Tomography for Assessment of Suspected Pulmonary Emphysema

Knudson, Ronald J.; Standen, James R.; Kaltenborn, Walter T.; Knudson, Dwyn E.; Rehm, Kelly; Habib, Michael P.; Newell, John D.

doi:10.1378/chest.99.6.1357

Cited by 153 publications

(93 citation statements)

References 34 publications

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“…The correlation coefficients for expiratoryflow ratesand the FEV1/vital capacity varied between â€"¿ .37 and â€"¿ .66 and were comparable to the difference between inspiration and expiration and reports in the literature (r = â€"¿ .51 to â€"¿ .72) [10]. Unlike re searchers who favortheuseof expiratorythin section CT for the detection of emphysema [7], we found that the calculation ofthe expira tory emphysemaindex over the whole lung based on helical CT did not improve correla tions with pulmonary function tests. The mean inspiratory volume of the central intrathoracic airwaysamounted to 50 ml with a broad range.…”

Section: Ssds Of the Inspiratory Emphysema Indexsupporting

confidence: 81%

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

Kauczor¹,

Heußel²,

Fischer³

et al. 1998

American Journal of Roentgenology

139

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This study was designed to determine lung volumes using inspiratory and expiratoryhelicalCT with two-dimensional (2D) andthree-dimensional (3D) postprocessing and to compare the accuracy of those measurementswith pulmonary function test results. SUBJECTS AND METHODS.Seventy-two patients with suspected pulmonary disease underwent unenhanced helical CT (slice thickness, 8 mm; pitch, 2; increment, 8 mm) at deep inspiration and expiration. Lung volumes were determined using either a 2D approach (semi automatic segmentation; thresholds, â€"¿ 1024 and â€"¿ 200 H) or a 3D technique (double-threshold seeded volumes of interest; thresholds, â€"¿ 1024 H [lower] and â€"¿ 900, â€"¿ 500, â€"¿ 400, â€"¿ 300, or â€"¿ 200 H [upper]). Pulmonary function tests were available for correlation in all cases.RESULTS. Using inspiratory helical CT, we underestimated total lung capacity by 12%, which had a goodcorrelation( r = .89) with staticlung volumes.Volumerevealedby expira tory helical CT was equivalent to intrathoracic gas volume, which also exhibited a good corre lation ( r = .88). However, using expiratory helical CT, we overestimated residual volume by ml with a rather good correlation ( r = .77). An emphysema index revealed moderate correlation with the relative forced expiratory volume in I sec (inspiration, r = â€"¿ .66; expiration, r = â€"¿ .54), whereas the expired volume showed a moderate correlation with the absolute forced expiratory volume in I sec ( r = .65). The 2D approach showed lower absolute volumes than the 3D technique (mean, 3.6%; r = .99). In the 3D technique, lower upper thresholds led to reduced volumes (170 ml/l00 H). CONCLUSION.Inspiratory and expiratory helical CT show high correlation with static lung volumes. The 3D technique (â€"1024 to â€"¿ 200 H) is recommendedfor absoluteestimation of lung volumes.L ung volumes are routinely as sessedusing pulmonary function tests.Thesetestsallow global mea surement of static inspiratoty volumes (total lung capacity); static expiratory volumes (in trathoracic gasvolumeafternormalexpiration and the residual volume after maximum expi ration); and dynamic volumes, like the abso lute and relative forced expiratory volume in 1 sec (FEV1). However, measurement of unilat eral or regional lung volumes is a major chal lenge in lung function testing.Helical CT is widely regarded as the im aging technique of choice for the radiologic assessment of the thorax [ I , 2]. A volume ac quisition of the lungs can be obtained in a single breath-hold of about 20 sec. Global, regional, and density-based (emphysema in dex) area and volume measurementscan be easily performed. The purpose of our study was to evaluate the accuracy with respect to pulmonary function tests of measurements of lung volumes and hyperinflation based on helical CT scans obtained at inspiration and expiration. Different postprocessing tech niques and different thresholds, including the emphysema index, were compared. Subjects and Methods PatientsSeventy-twopatients(58 men, 14women)with a median age of 59 years (ra...

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Section: Ssds Of the Inspiratory Emphysema Indexsupporting

confidence: 81%

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

Kauczor¹,

Heußel²,

Fischer³

et al. 1998

American Journal of Roentgenology

139

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“…A recent study concluded that spirometrically controlling lung volumes did not improve the repeatability of quantitative CT scanning in assessing the amount of emphysema [12]. There is controversy in the literature as to whether expiratory [27,28] or inspiratory [19] CT scanning correlates better with physiological measures of emphysema. Workshop members agreed that scanning as close to TLC as possible without spirometry is acceptable.…”

Section: Image Acquisitionmentioning

confidence: 99%

Report of a workshop: quantitative computed tomography scanning in longitudinal studies of emphysema

Newell

Hogg²,

Snider³

2004

Eur Respir J

156

138

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It has been reported that quantitative computed tomography (CT) scanning of the lungs showed decreased progression of emphysema in a randomised clinical trial in patients with severe a 1 -antitrypsin (a 1 -AT) deficiency receiving monthly intravenous augmentation therapy with human a 1 -AT. Comparable results were not obtained using rate of decline of forced expiratory volume in one second.Accordingly, the Alpha-1 Foundation convened a workshop to explore the feasibility of using quantitative CT data as a primary outcome variable in trials of drugs for treating a 1 -AT deficiency.This report reviews the following: the principles for the use of modern CT scanners for quantifying emphysema; the methods and data on validation by comparison with measurements of severity of emphysema in inflation-fixed specimens of lungs; and the possibility of decreasing radiation dosage from CT to make it safe and ethically possible to use CT in longitudinal studies.The workshop concluded that it is feasible, safe and ethically possible to use computed tomography in longitudinal studies of emphysema. It recommended that the primary end-point should be a significant shift in the 15th percentile of lung density. Eur Respir J 2004; 23: 769-775.

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“…The possible role of CT obtained after deep expiration in the assessment of emphysema was first suggested by KNUDSON et al [57] because correlations between CT measurements and lung function tests were stronger in expiration than in inspiration. In 64 patients, most of whom had airflow obstruction, these authors obtained 8-mm thick CT slices at two levels in upper lung zones at full inspiration and full expiration and measured the percentage area of lung occupied by attenuation valuesv-900 HU.…”

Section: Factors Influencing Computed Tomography Densitometrymentioning

confidence: 99%

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

2001

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Quantitative computed tomography assessment of lung structure and function in pulmonary emphysema. A. Madani, C. Keyzer, P.A. Gevenois. #ERS Journals Ltd 2001. ABSTRACT: 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. Computed tomography (CT) is an imaging method providing transverse anatomical images in which the value of each picture element (i.e. pixel) corresponds to the x-ray attenuation of a defined volume of tissue (i.e. voxel). The X-ray attenuation values for each set of projections (i.e. slice) are registered by the computer and organized in a matrix form. The number of calculated pixels determines the image matrix size, influences the image resolution, and should thus be as high as possible. In clinical practice, the matrix size is actually 5126512 pixels. The X-ray attenuation, also called tissue density, is numerically expressed in Hounsfield units (HU). The scale of attenuation values ranges from -1,000 HU, corresponding to the attenuation value of air, to 3,000 HU, with 0 HU corresponding to the attenuation value of water. The thousands of pixels included in one scan make CT the most precise morphological method able to assess the pulmonary structure in vivo [1].In pulmonary emphysema, the major advantage of CT is that in addition to providing data concerning overall lung destruction, it also identifies the specific locations in the lung where the alveolar surface has been destroyed. The ability to estimate the extent and severity of pulmonary emphysema during life is important for several reasons. 1) Accurate detection of lung destruction when it appears and careful mapping of its progression are required to understand the natural history of emphysema.2) The treatment of advanced disease by lung volume reduction surgery (LVRS) requires knowledge of the location of the lesions and objective methods of assessing the surgical

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Expiratory Computed Tomography for Assessment of Suspected Pulmonary Emphysema

Cited by 153 publications

References 34 publications

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

Assessment of lung volumes using helical CT at inspiration and expiration: comparison with pulmonary function tests.

Report of a workshop: quantitative computed tomography scanning in longitudinal studies of emphysema

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

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