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Eur Radiol (2008) 18: 2739–2744
DOI 10.1007/s00330-008-1061-3 COMPUTER TOMOGRAPHY
Fatih Alper
Metin Akgun
Omer Onbas
Omer Araz
Received: 3 December 2007
Revised: 29 April 2008
Accepted: 2 May 2008
Published online: 26 June 2008
# European Society of Radiology 2008
F. Alper . O. Onbas
Department of Radiology, School of
Medicine, Atatürk University,
Erzurum, Turkey
M. Akgun . O. Araz
Department of Chest Diseases, School
of Medicine, Atatürk University,
Erzurum, Turkey
F. Alper (*)
Atatürk Üniversitesi,
Lojmanları 5. Blok No:2,
Erzurum, Turkey
e-mail: fatihrad@yahoo.com
Tel.: +90-442-3166333
Fax: +90-442-3166340
Introduction
Silicosis is an occupational lung disease caused by
inhalation of crystalline silica dust. Although silicosis is a
well-known disease with very familiar causes such as
tunneling, mining, and sandblasting, and is considered a
preventable condition, it still continues to be reported in
new, unusual, or even unexpected occupations [1–3].
Recently, denim (or jean) sandblasting has been reported as
a new and unusual source of silicosis in Turkey, with a
recent increase in case number, even with fatal outcomes
[4–6].
In denim sandblasting, workers are exposed to silica
because they project silica-containing sand, as an abrasive,
onto denim surfaces to produce a “worn-in” appearance.
This kind of exposure seems to be more hazardous than that
of many previously known sources because of intense
CT findings in silicosis due to denim
sandblasting
Abstract The purpose of this study
was to describe the findings of CT
performed on denim sandblasters with
silicosis. Fifty consecutive male patients
with silicosis were evaluated.
Their clinical data and pulmonary
function tests (PFT) were obtained.
The CT findings were recorded and
the correlations between CT nodular
profusion score and the other
parameters were assessed. The
diagnoses of the patients were classified
as accelerated silicosis (n=43)
and acute silicosis (n=7). The most
common CT finding was centrilobular
nodules. Twenty-three patients had
complicated silicosis based on pleural
involvement and presence of progressive
massive fibrosis (PMF). Lymphadenopathy
(LAP) was positive in
50% of the patients, with calcification
in 24%. The CT grade was highly
correlated with the clinical data such
as exposure duration and PFT. Our
findings suggest that the clinical
manifestation of silicosis in denim
sandblasters is severe. Although the
duration of exposure is shorter the rate
of complicated silicosis patients with
pleural involvement was unexpectedly
higher in the cases. Because the most
common radiological appearance was
nodules and the CT grading of the
nodules was highly correlated with the
clinical data, nodule grading may be
used in the management of such cases.
Keywords CT . Lung . Silicosis .
Occupational diseases .
Denim sandblasting
exposure during long hours of work under very poor
hygiene conditions, without any serious respiratory
protection [4–6].
Although chest radiography remains the most convenient
imaging technique to diagnose silicosis and to
monitor its progression, it has some limitations in
assessment of pneumoconiosis [3]. Thin-section computerized
tomography (CT) has been shown to detect some cases
that are undetectable by chest x-ray and to better
characterize lung involvement [7, 8]. Silicosis associated
with denim sandblasting is a unique issue and has many
different aspects compared with classic silicosis, e.g., it
may develop quickly and may cause immediate mortality,
especially in young people [4–6]. However, no previous
data exist on CT findings of silicosis associated with denim
sandblasting; thus, we aimed to determine the thin-section
CT imaging findings of the cases with silicosis associated

2740
with sandblasting and the correlation between CT findings
and clinical data.
Patients and methods
Patient recruitment and study procedures
This study included 50 consecutive male patients with
clinically proven silicosis who were admitted to a pulmonary
outpatient clinic between August 2004 and June 2007.
Those patients with a smoking history >10 pack-years,
previous tuberculosis history, and active tuberculosis
diseases were excluded from the study. The diagnosis
was based on mainly clinical history, occupational exposure
to silica dust, and chest x-ray findings after other
possible diagnoses were ruled out, except in the first cases
in whom open lung biopsy was required to confirm
diagnosis because no previous association had previously
been described [4].
Demographic and clinical characteristics including
age, exposure duration, smoking history, and spirometry
results, which are forced expiratory volume in one
second (FEV1), forced vital capacity (FVC), and FEV1/
FVC ratio, were recorded. During initial evaluation, all
the patients underwent chest radiography and then thinsection
CT examination. The patients were classified
into three clinical diagnosis categories: classic chronic
silicosis, accelerated silicosis, and acute silicosis/silicoproteinosis
[9].
Written informed consent was obtained from all the
patients, and the study protocol was approved by the
internal review board of the hospital.
Thin-section CT examination
Obtaining CT images
CT was performed with either a Spiral CT (X-Vision,
Tokyo, Japan) (n=47) or 16-detector-row CT system
(Aquillon, Toshiba Medical Systems, Tokyo, Japan) (n=
3). All the CT examinations were obtained at maximal
inspiration in the supine position with 1.5-mm collimation
at 20-mm intervals. The volume of the patient examined
extended from the lung apices to the basis.
The images were photographed with a window level of
−600 HU and a window width of 1,300 HU (i.e., lung
windows) and a window level of 10 HU and a window
width of 300 HU (i.e., mediastinal windows). Additionally,
thin-section CT images were reconstructed with a highspatial-frequency
(bone) algorithm and photographed with
relatively wide window settings to allow evaluation of both
pleura and parenchyma (window center −550 HU, window
width 1,500 HU).
CT evaluation
The CT hard copy images were reviewed independently by
two radiologists who were unaware of the clinical and
radiographic data. Final decision was made by consensus
of the two radiologists.
The reviewers evaluated the images with lung window
for the presence and distribution of nodules, interlobular
septal lines, intralobular septal lines, parenchymal bands,
ground-glass opacity, consolidation, air bronchogram,
progressive massive fibrosis (PMF) or masses, traction
bronchiectasis, honeycombing, lobular low-attenuation
areas, and emphysema. The images were evaluated with
relatively wide window for the presence and severity of
pleural thickening, calcification, and effusion and with
mediastinal window for the presence of lymphadenopathy
with or without calcification. In the presence of calcification,
the type of the calcification (central, eccentric, or eggshell)
was evaluated.
The nodules were characterized with respect to type,
location, and number [10]. Each lung was craniocaudally
divided into upper (apex to carina), middle (carina to
inferior pulmonary vein), and lower (inferior pulmonary
vein to lung base) zones. For qualitative analysis of the
nodules in the craniocaudal axis, the system for grading
nodular profusion on CT involved the use of a modification
of the scale described by Bergin and colleagues. Accordingly,
grade 0 meant no nodules; grade 1, a small number of
nodules without vascular obliteration; grade 2, a larger
number of nodules with mild vascular obliteration; grade 3,
a large number of nodules with moderate vascular
obliteration; and grade 4, a large number of nodules
with severe vascular obliteration, with or without
coalescence (

Fig. 1 CT (lung window)
shows many nodules with mild
vascular obliteration and grade 2
nodular profusion in axial (a)
and coronal (b) plans
PMF, another important finding of silicosis, was defined
as the presence of silicotic nodules larger than 2 cm in
diameter on CT images, according to the criteria used by
the College of American Pathologists [13]. As well as the
presence of PMF, the locations of the PMFs were evaluated
(Fig. 2).
The other parameters (ground-glass opacity, consolidation,
interlobular, intralobular septal thickening, parenchymal
band, traction bronchiectasis, honeycombing, and lobular
low-attenuation area) were defined according to Gotway et al.
[10].
The “crazy-paving” appearance was defined as scattered
or diffuse ground-glass attenuation with superimposed
interlobular septal thickening and intralobular lines. The
“head-cheese sign” was defined as complex CT appearance
of abnormal alveolar infiltrates combined with air trapping.
The presence of pleural thickening and its type (plaquelike
or nodular) were also determined (Fig. 2). In addition,
lymph node enlargement with the short axis exceeding
1 cm was recorded. Lymph node stations were determined
as hilar, subcarinal, pretracheal, and diffuse.
Silicosis was described as two types radiologically:
simple (presence of multiple small nodules 2–5 mmin
Fig. 2 CT (relatively wide window) shows PMF lesion forming
partial distortions more markedly in the apex of the right upper lobe.
Bilateral pleural thickening is also present
diameter) and complicated (also known as PMF, develops
through the expansion and confluence of individual
silicotic nodules) [14].
Finally, whether a correlation existed between the CT
grades and other parameters such as time of exposure,
latency period (time elapsed since beginning of exposure),
age on admission to the hospital, spirometry results,
presence of PMF, and pleural thickening was investigated.
Statistical analyses
The data were analyzed using the SPSS version 11
statistical software (SPSS Inc., Chicago, IL). Correlations
between CT grade and the other parameters were calculated
using Spearman’s rank order correlation coefficients.
Pearson chi-square test was used to compare categorical
values. Mann–Whitney U test was used to compare means
of some variables. P

2742
The most common abnormality found on thin-section
CT was nodules with predominance of centrilobular ones
(n=47, 94%). The radiological classification of the nodules
seen on the CT was as follows: only centrilobular in 30
patients (60%), centrilobular and tree in bud in two (4%),
centrilobular and perilymphatic in 15 (30%), and only
randomized in three (6%).
CT grades in the craniocaudal axis are provided in
Table 1. There was a slight overall increase of nodular
profusion of the upper and middle zones. In contrast to the
predominance of mild disease in the upper zones, there was
lower zone predominance of severe disease. There was
posterior predominance in the anteroposterior axis (Table 2)
and middle and cortical predominance in central-peripheral
axis (Table 3). Sixteen cases had PMF (eight of them were
conglomerate masses; one, calcified mass and one, necrosis).
Presence of PMF increased towards the upper zones in
the craniocaudal distribution (Table 4).
Lymph node enlargement was positive in half of the
cases.. Six cases with lymph node enlargement (12% of all
cases) also had calcification (four eccentric and two
central). No eggshell calcification was determined. In the
evaluation of lymph node stations, there was only hilar
involvement in eight cases, hilar and subcarinal involvement
in four cases, pretracheal in addition to hilar and
subcarinal involvement in one case, and diffuse involvement
in 12 cases. Pleural thickening was positive in 19
cases (38%) and the thickening was plaque-like in 11 cases
and nodular in eight cases. The degree of pleural thickening
was minimal in 12 cases, moderate in four cases, and
diffuse in three cases. Crazy-paving appearance and headcheese
sign were detected in five and three cases,
respectively.
The other findings including axial interstitium thickening,
interlobular septal thickening, intralobular septal
thickening, ground-glass opacification, consolidation, traction
bronchiectasis, pleural effusion, honeycomb, and
lobular low-attenuation areas are summarized Table 5.
Twenty-seven patients had simple silicosis progressing
with nodules only, while the remaining patients had
complicated silicosis (n=23) with PMF (n=16) and/or
pleural pathologies (n=19). No apical scar, bullae, and
paracicatricial emphysema were detected.
All cases were clinically classified as accelerated (n=43)
or acute silicosis/silicoproteinosis (n=7).
Table 2 Anteroposterior distribution of nodules
In the evaluation of an association between radiological
findings and clinical data, there was a positive correlation
between CT grade and exposure duration and age at
admission, and a negative correlation between CT grade
and pulmonary function test parameters (FEV 1 and FVC).
Although the correlation between CT grade and age was
not significant, the correlations between CT grade and
exposure duration (r=0.37, p

Table 3 Central to peripheral axis distribution of nodules
presence of PMF with progression of the disease, and less
lymph node involvement compared with classic silicosis.
Although there are three main clinical presentations of
silicosis, which are classic silicosis, accelerated silicosis,
and acute silicosis/silicoproteinosis, in our study, no classic
chronic silicosis case was detected. Classic chronic silicosis
is the most common presentation, in which patients
remain asymptomatic until after an interval of 10–20 years
of continuous silica exposure, by which time radiographic
evidence is present. In accelerated or acute silicosis, the
exposure time after which the disease becomes clinically
evident is much shorter and the rate of disease progression
noticeably faster. Clinical presentation as early as 1 year
after exposure and death within 5 years has been reported
[15]. The exposure duration and latency period were
shorter in our cases. One of our cases with accelerated
diseases and two with acute diseases died during the study
period. It is highly possible that high concentrations of dust
in a relatively confined space and younger age without
serious protection from severe diseases were responsible as
stated in previous studies [3, 16].
Nearly all patients (94%) had nodules with a predominance
of centrilobular type as seen in classic silicosis [3,
10, 11]. On CT grade evaluation, we detected mid to upper
zone predominance in milder cases (grade I + II) and
middle and lower zone predominance in severe cases
(grade III + IV), which is different from the literature
findings [3]. As opposed to the upper lobe predominance of
classic silicosis, we observed that predominance may be
different according to the severity of disease in these cases.
The evaluation on the axial plane revealed predominance in
the middle and cortical zones of the lungs. Similar to the
literature findings, posterior predominance of the nodules
was also observed [3, 17, 18]. CT grade was significantly
correlated with PMF and nodular pleural thickening.
Although presence of PMF is highly associated with
progressive classic silicosis, we found it in one third of the
cases (32%). In silicosis, PMF usually involves the upper
Table 4 Craniocaudal distribution of PMF
Table 5 Other CT findings
Finding Number Features
2743
Axial interstitium thickening 12 9 smooth
3 nodular
Interlobular septal thickening 7 6 smooth
1 nodular
Intralobular septal thickening 5
Ground glass 6 5 with consolidation
Consolidation 11 5 with air bronchogram
Lobular low-attenuation areas 9
Traction bronchiectasis 4
Honeycomb No
Pleural effusion No
lung zones, and various types of calcification of large
opacities are found, mostly punctate rather than linear or
massive. In our study, it was distributed in all the lung
zones, with a predominance of the upper zone followed by
mid and lower zone involvements, respectively. Although
our findings of PMF locations were compatible with the
literature, mass calcification (1/16) and necrosis (1/16),
which are frequently reported in the literature, were
relatively less common in our study [3, 17]. The relatively
lower incidence of PMF calcifications in our patients might
have been due to the shorter interval of symptom
presentation. Marchiori et al. reported a mean interval of
27.5 years for conglomerated mass development due to
sandblasting, while in our study both exposure duration
and latency period were very short [19]. In our study, a
statistically significant correlation was determined between
the exposure duration and CT grade and PMF presence.
This finding may be important to predetermine the cases
with higher CT grade but no PMF for development of PMF.
In addition, pleural thickening was unexpectedly high in
our study. Arakawa et al. determined a rate of 58% for
pleural thickening in complicated silicosis cases, while this
rate was 69% in our study [13]. Although LAP with
calcification, especially eggshell type, is commonly
encountered in classic cases, half of our cases had LAP
with a low rate of uniform-type calcification and no
eggshell [3]. Another finding of our study was the
statistically significant correlations between CT grade
and both exposure duration and PFT findings. These
findings suggest that radiological findings are highly
correlated with clinical data in such cases.
Although the findings associated with classic silicosis
such as LAP, LAP calcification, and PMF development
were not very prominent, the rate of complicated silicosis
patients with pleural involvement was unexpectedly higher
in the cases with silicosis due to denim sandblasting.
Because the most common radiological appearance was
nodules and the CT grading of the nodules was highly

2744
correlated with the clinical data, nodule grading may be
used in the management of such cases. This radiological
evaluation study also indicates that silicosis is an important
health care problem in the workers of denim sandblasting
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