Biomedical Engineering Reference
In-Depth Information
specific organs and tissues within a set of CT images is therefore
ambiguous and must be supplemented with other information
2
.
Nevertheless, the spatial and density resolutions and the speed of CT
have evolved enormously so that the current ability to image tissues
in space and in time, through the use of gated and repeated studies, is
extraordinarily impressive.
Figure 3.4. Transverse CT scan through the abdomen: (a) one of the very first
whole body CT images made public, (b) a scan through a similar body sec-
tion taken on a modern CT scanner. Panel (b) courtesy of J. Smirniotopoulos,
Uniformed Services University, Bethesda, USA.
Figure 3.4a is one of the first whole body CT scans made public,
taken on the first EMI whole-body scanner. The field of investigators
was small in those days, so I knew the individual whose body was
imaged. When in the early 1970s I first saw this image, and several
other sections at different levels within the body, I begged copies of
them and carried them around in my briefcase for over a year;
so impressive to me was the information which they unleashed.
Figure 3.4b is a modern CT scan (on an entirely different person) at
about the same level of the body, showing how far the technology has
come since that first image.
Not only does CT distinguish tissues in space, it does so with very
good spatial accuracy. The spatial position of each voxel (volume
element) of a CT matrix of values is determined by purely mechanical
details of the scanner. As a result, the reconstructed CT values are
2
N ot infrequently, contrast medium is injected intravenously and sub-
stantially enhances the contrast between selected tissues.
