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Professor of Radiology
New York University Medical Center
Bellvue Hospital
New York, New York
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This is one of the numerous hospital admissions for this
34-year-old AIDS patient with known cutaneous Kaposi's
sarcoma (KS), who presented with a history of one episode
of hemoptysis, fever, and decreasing exercise tolerance.
On admission his CD 4 count measured 10 cells/mm3. His initial
chest radiograph showed non-specific bilateral interstitial and
air-space opacities in both mid and lower lung fields.
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The patient was scanned on a GE HiSpeed Advantage system using
a protocol specifically developed for airway evaluation,
particularly for patients presenting with hemoptysis - a protocol
that combines three-phase and helical/axial techniques.
For phase 1, we perform an initial helical acquisition using 7-mm
sections and a 1:1 pitch from C5 (the level of the cords) to the
carina. These data are reconstructed at 7 mms.
For phase 2, a second helical acquisition is performed, using 5-mm
sections from the carina to the level of the inferior pulmonary veins.
A pitch of 1:1 or greater is used as needed, depending on the individual
patient's size. These data are then reconstructed at 3 mms.
For phase 3, 1-mm HRCT images are obtained @ 10 mm from the level of
the inferior pulmonary veins through the lung bases, and are reconstructed
with an edge-enhancing (bone vs. lung) algorithm.
Contrast is optional, although it is preferred in patients with a
questionably abnormal mediastinal and/or hilar contour on routine
chest radiographs. When used, 60% contrast is administered at a rate
of 2 cc/second with a 30-second delay. Administration may begin at the
outset of the study or be withheld to the second phase, reflecting the
likely presence of either mediastinal and /or hilar pathology.
This approach allows optimal identification of both potential focal
central-airway pathology and peripheral bronchiectasis - the two most
likely causes of hemoptysis in patients with non-localizing chest
radiographs.
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The axial CT sections through the mid and lower trachea (Fig.1,2)
reveal subtle areas of focal asymmetry of the tracheal lumen, with
minimal irregularity and thickening of the tracheal wall. A 3-D
surface rendering of the trachea (Fig.3) clearly shows the presence
of two well-defined focal abnormalities involving both the
anterosuperior and right inferolateral tracheal walls. These findings
were also apparent with virtual bronchoscopy (a Works-in-Progress).
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Evaluation with fiberoptic bronchoscopy (Fig.4) confirmed the presence
of focal tracheal abnormalities corresponding precisely to the CT
findings; these subsequently proved to be due to invasive Aspergillus
fumigatus.
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The clinical advantage of accurate, non-invasive localization of
abnormalities within and/or adjacent to the tracheobronchial tree
is apparent. Although the case presented here involves an HIV (+)
patient, all patients with suspected focal abnormalities within the
tracheobronchial tree may be studied to advantage with CT.
To date, CT has proved of greatest clinical relevance in the work-up
of patients with known or suspected lung cancer. In this setting,
determining the true extent of disease both within and outside the
bronchial lumen is critical to appropriate clinical management. CT
is of particular value in identifying those patients for whom
pre-operative staging is indicated, with mediastinoscopy, transbronchial
needle aspiration and/or surgery - and in determining which of these
staging alternatives is most likely optimal.
In select cases, CT findings of extensive invasion of mediastinal
structures may obviate invasive staging altogether.
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For patients, the major benefit of CT is its ability to non-invasively
identify and characterize both bronchial and parenchymal abnormalities.
When findings are present, CT allows the appropriate selection of
patients for whom invasive procedures are needed.
Equally important, in select cases CT may obviate invasive procedures
altogether, either by disclosing no significant findings, or by
identifying otherwise unsuspected pathology to account for the patient's
symptomatology.
To date, these advantages have proved of greatest value in patients
presenting with hemoptysis and a non-localizing chest radiograph in
whom there is a low index of suspicion for cancer.
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