Acute Aortic Disease.. - Index of

Imaging of Aneurysms and Dissections 63
Imaging technology advances at a rapid pace. Over the last few years, CT technology
has evolved from single slice to spiral to multislice technology, and the
number of detectors in multislice scanners has increased from 4 to 16 to 64. One
hundred and eight- and 256-slice scanners are in development and likely to be
in clinical practice soon. With the increasing number of detectors, one issue of
concern is that radiation exposure increases proportionately. With the 64 detectors,
the absorbed radiation dose for a cardiac study is ∼11 mSv, almost double
that of a 16-slice scanner (Reference 18, above). This may in fact become a
limiting factor in the widespread applicability of scanners with higher number
of radiation detectors.
A different approach to conventional CT imaging is represented in the
so-called flat-panel technology. This approach does not use rotating detectors but
rather a flat detecting surface that allows for volumetric high-resolution imaging.
Preliminary application of this technology has been reported for imaging of the
coronary arteries in an excised swine heart (1). At the present time, the computing
power needed for in vivo cardiovascular imaging is not practical, although in the
future computer technology may surpass this frontier.
Do you anticipate that in the future interventional vascular procedures can be
performed under “CT fluoro,” obviating the need for angiographic control of
these procedures?
Currently, interventional vascular procedures are performed under fluoroscopy. One
drawback of this approach is the considerable radiation exposure. CT fluoroscopy,
at least with current technology, could potentially facilitate the three-dimensional
appreciation of the inter-relationships of the anatomic structures visualized during
interventional procedures. CT guidance, however, would not eliminate the radiation
exposure, and in fact the radiation dose would likely be higher than the current
projection angiographic approach. On the other hand, real-time MR guidance
would be a significant advance, as this would eliminate ionizing radiation exposure.
Catheters equipped with receiver coils at tip have been developed and shown
to be adequately imaged at a rate of a few frames per second. MR advancement of
catheters in the aorta of experimental animals has been shown to be possible (2),
and even feasibility data in peripheral arterial interventions in humans have been
described (3). Because of the minimal biologic cost that this approach offers, it is
likely that this technology will become a clinical tool in the not too distant future.
Are there any totally new imaging modalities on the horizon, different from CT
or MR?
Technology advances at a rapid pace. Over the last decade we have witnessed a
shift from macro-anatomical imaging to micro-molecular and cellular imaging.
Developments have focused more on coronary atherosclerosis, as this is the major
cause of morbidity and mortality in humans. These developments, however, can
be applied to the entire vascular tree, where atherosclerosis can develop.
Newer technologies that attempt to assess the atherosclerotic plaque include
thermography, angioscopy, spectroscopy, elastography, and optical coherence