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3.2 Imaging Modalities in Stem Cell Transplant
3.2.1 Computed Tomography
After HSCT, there are many known complications that physicians must keep in
mind. The timeline of each occurrence helps to narrow the focus on the pathogenic
mechanism responsible. While clinical presentation is the guiding principle by
which physicians must approach potential complications, the importance of radio-
logic procedures in the diagnosis and follow up cannot be overstated. Computed
Tomography (CT) plays a major role in assessing potential complications after
HSCT. In the post transplant setting, one can categorize complications based on
timeline, as well as, the affected organ systems.
More than 50% of pediatric HSCT patients experience pulmonary complications,
which can be infectious or non-infectious. Bacteria or Fungi cause some of the early
infectious complications. While plain radiographs have utility in identifying consoli-
dative changes, chest CT is much more useful for infections with atypical features. It
is very helpful for identifying fungal infections, such as with invasive aspergillosis,
in which chest radiographs may demonstrate normal appearance, but the chest CT
may show airspace opacification, pulmonary nodules, air crescent or “halo” sign, or
cavitary lesions (Fig. 3.1). Tracheobronchial aspergillosis is also well visualized on
Fig. 3.1 Aspergillus pneumonia after allogenic transplant. Classic but nonspecific ‘halo sign’,
with nodules surrounded by ground-glass opacity (arrow)
M. Atiq et al.