10
Diagnosis
Table 3. Radiological Terms for Heterogenous Lung
Attenuation
Terminology Significance Description
Mosaic
attenuation
• Generic term referring to a
patchwork of regions of differing
attenuation on inspiratory CT
images
• Term only used for
description of inspiratory
CT images
• Can reflect the presence
of vascular disease, airway
abnormalities, or ground-glass
interstitial or airspace infiltration
• Combination of areas of
low and high attenuation
that can correspond to two
main situations:
a. Areas of GGO ("high")
and normal lung ("low")
or
b. Areas of normal lung
("high") and areas of
decreased attenuation
("low")
• Areas of GGO reflect an
infiltrative lung disease
Air trapping • Abnormal retention of air distal to
airway obstruction
• Term exclusively used for
description of expiratory CT
images
• Recognized as parenchymal areas
that lack the normal increase
in attenuation and the volume
reduction of normally ventilated
lung
• Air trapping appears as focal
zones of hypoattenuation
in the background of
hyperattenuating normal
lung on expiratory CT
images
• Mosaic attenuation and air
trapping are not synonymous and
cannot be used interchangeably
Mosaic
perfusion
• Regional differences in lung
attenuation secondary to regional
differences in lung perfusion
• Term used for description
of inspiratory CT images
• May be seen in vascular (exclusive
perfusion abnormalities) or airway
(perfusion abnormalities resulting
from abnormal regional lung
ventilation) diseases
• Presence of decreased
vascular sections within
areas of low attenuation in
comparison with areas of
normal lung
• Differential diagnosis facilitated by
expiratory scans:
a. In case of vascular disease: same
gradient of attenuation between
areas of low and high attenuation
b. In case of airways disease: the
attenuation differences are
accentuated due to the additional
depiction of air trapping
