Silicosis in 76 men: qualitative and quantitative CT evaluation--clinical-radiologic correlation study.
OBJECTIVE
To use qualitative and quantitative computed tomography (CT) to test the hypothesis that impaired lung function with silicosis is due to progressive massive fibrosis (PMF) and associated emphysema.


METHODS
Seventy-six men with silicosis underwent volumetric and thin-section CT of the thorax. Lung function, Borg scale dyspnea grade, silica exposure duration, and cigarette consumption were determined. Nodular profusion (NP) at chest radiography was graded according to the International Labor Organization radiographic classification system; NP and PMF at CT were visually graded by using five-point (ie, grades 0-4) and four-point (grades 0-3) scales, respectively. Emphysema and NP, which together are defined as the NP index, were quantified by using attenuation threshold values of less than -950 HU and greater than -100 HU, respectively. Mean lung attenuation was also determined. Relationships among the CT, chest radiographic, and clinical parameters were analyzed by using Spearman correlation.


RESULTS
NP at chest radiography correlated (r > 0.50) with all CT parameters of nodularity. CT PMF had the highest correlation with emphysema (r = 0.58, P <.001). NP at chest radiography and all CT parameters were inversely related to lung function. At multiple regression analysis, PMF and emphysema index (both at CT) were significant determinants of forced expiratory volume in 1 second (FEV1) (P =.006 and.03, respectively) and FEV1 to forced vital capacity (FVC) ratio (P =.007 and.02, respectively). Mean lung attenuation remained related to FVC (P =.03), diffusing capacity of lung for carbon monoxide (P =.04), and Borg scale grade (P =.01). Cigarette consumption and silica exposure duration had no independent effects on lung function.


CONCLUSIONS
Qualitative and quantitative CT parameters can be used as indirect measures of functional impairment in silicosis. PMF and emphysema are independently related to airflow obstruction, whereas mean lung attenuation is related to clinical dyspnea and reduced lung volume.
Ooi
Gaik C
GC
School of Professional and Continuing Education, Department of Radiology, University of Hong Kong, Queen Mary Hosp, F/4, Block K, Pokfulam, Hong Kong SAR, China. cgcooi@hkucc.hku.hk
Tsang
Kenneth W T
KW
Cheung
T Fai
TF
Khong
Pek L
PL
Ho
Iris W T
IW
Ip
Mary S M
MS
Tam
Chak M
CM
Ngan
Henry
H
Lam
Wah K
WK
Chan
Fu L
FL
Chan-Yeung
Moira
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000503:physiopathology; D011658:Pulmonary Fibrosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D013902:Radiography, Thoracic; D012829:Silicosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012907:Smoking; D014057:Tomography, X-Ray Computed; D014797:Vital Capacity