CTA has made remarkable progress over the last decade. With optimal vessel opacification and carefully timed image acquisition, the quality and range of images generated by multislice CT are truly impressive.
This publication was supported by an educational grant from
Amersham Health, Princeton, NJ. The opinions expressed in this
publication are those of the authors and not necessarily those of
is a Professor of Radiology and Oncology, and Director of
Diagnostic Radiology and Body CT at Johns Hopkins Medical
Institutions, Baltimore, MD.
Radiologists at leading institutions have been performing CT
angiography (CTA) for more than a decade. Even in 1989, when
single-slice CT was introduced, it was possible to produce
reasonable-quality CT angiographic images of certain vessels,
particularly the aorta. By the late 1990s, following the
introduction of 4-slice scanners, most CTA applications had become
both easier to do and more robust. Sixteen-slice technology,
introduced in 2002, promises to make CTA a standard procedure in
most radiology departments.
As shown in Table 1, CT has undergone an extraordinary evolution
during the last 20 years. Today it is characterized by subsecond
scan times, submillimeter scan thicknesses, and the acquisition of
approximately 1000 slices per examination. Sixteen-slice scanners
have been particularly important in advancing CTA, offering the
ability not only to optimize contrast enhancement but also to
acquire data in isotropic voxels. Having equal spatial resolution
in the X, Y, and Z directions greatly improves three-dimensional
CTA is not a study that is used occasionally for unique or
difficult cases. Instead, it has become part of standard practice.
Indeed, growth in CTA has exceeded expectations, in large part as a
result of technological innovation. In fiscal year 2000, we
performed 1160 body CTA examinations at Johns Hopkins. In 2001,
that number climbed to 2037 and in 2002, to 2818. Prior to
acquiring a 16-slice scanner, we projected a CT volume of 3150 for
fiscal year 2003. Instead, the final volume was 3800.
The clinical applications of CTA continue to increase in number
and range. Today, CTA is performed in the chest, abdomen, kidney,
liver, brain, and heart with increasing ease.
It is possible to examine the pulmonary vasculature (Figure 1),
the aorta, and the mediastinum, among other
thoracic structures. Routinely, CTA is used to examine the carotid
arteries for stenosis (Figure 2), an application that markedly
reduces patient risk and has substantially increased CT volume in
many radiology practices.
CTA of the coronary arteries, while not yet routine, can be
readily performed with the newest scanners. Whether in the
examination of patients for stenosis or in the evaluation of graft
patency, CTA of the coronary vasculature represents an application
of great promise.
In approximately 90% of diagnostic studies, CTA can replace
conventional angiography. The evaluation of pulmonary embolism is a
perfect example of a clinical application in which CTA has become
the diagnostic standard. Even more important, in the case of
cancer, CTA can not only diagnose disease but can also provide
accurate information on staging, all in a single examination
In hepatic imaging, CTA can be used for vascular mapping and to
look for such conditions as cavernous transformation of the portal
vein or collateral vessels in the abdominal wall of a patient with
cirrhosis (Figure 4). CTA is useful not only for detecting lesions,
but also for looking at the pattern of contrast enhancement; such
as in the case of hemangioma. Similarly, in the case of
a metastatic neuroendocrine tumor, arterial-phase imaging can
nicely reveal arteriovenous shunting.
CTA offers numerous opportunities to increase the capability of
CT, not by improving the definition of pathology but, as shown in
Figure 5, by detecting lesions that might otherwise be overlooked
because they are infiltrative rather than mass-like. Detection of
neovascularity in a patient with hepatoma is an example.
CTA is becoming the state of the art for examining a wide range
of problems, including those in which CT has always played an
important role. Preoperative evaluation of the mesenteric vessels
in a patient with a recurrent small bowel tumor, or examination for
ischemic bowel in a patient with abdominal pain represent classic
applications of CT that are strengthened by advances in scanning
With scan times of <10 seconds, and delays from scanning to
visualization of only 1 to 2 minutes, advanced CT technology is
markedly changing how we practice. As our experience increases, and
as scanners continue to improve, many questions remain to be
answered. The importance of good contrast enhancement is clear.
However advanced image processing techniques may be, whether
maximum-intensity projection or volume rendering, they rely on the
quality of the initial data sets. With adequate vessel
opacification and optimally timed image acquisition, the quality of
the images we are able to create is truly impressive.
(A and B) Maximum-intensity projections reveal pulmonary
(A and B) Occluded left internal carotid artery. CTA is routinely
used to examine carotid arteries for stenosis.
(A and B) In hypervascular right renal cell carcinoma, CT can not
only detect disease but also provide accurate information on
. Collateral vessels in the abdominal wall of a patient with
CTA detects neovascularity in a patient with hepatoma in a
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