INTRODUCTION - Fundamentals of Three-Dimensional Digital Image Processing - page 15

(b) Amounts of data

As compared with 2D images, 3D images represent massive amounts of data. A
single X-ray CT image, for example, may be 512 512 bytes, while images

from tissue sample microscopy may be as large as 3000

× 512 ×

500 bytes.
This has huge effects on all aspects of the image processing system. Already,
data transfer between sensors and processors poses a significant problem in
CT devices.

× 2000 ×

(c) The importance of display technology

As described in (1) above, it is dicult for humans to have a direct compre-
hension of 3D images. The use of appropriate display rules (visibility rules)
is therefore extremely important, not only when displaying the results of pro-
cessing input image files, but also in researchers' evaluation of intermediate
results. Processing information contained within a 3D image for display onto
a 2D screen is in a sense the opposite of the problem posed by computer vi-
sion. This technology is currently within the realm of computer graphics or of
information visualization. Three-dimensional image processing is therefore a
new field, requiring an integration of image pattern recognition and computer
graphics. This also has a deep connection to virtual reality, and therefore has
an even greater significance in this age of multimedia processing.

(d) Properties of image geometry

Several properties arise in 3D images that did not exist in 2D images. Typi-
cal examples include the existence of knots, links, and holes. In general, the
topological characteristics of figures are extremely complex. As a result, the
design and evaluation of related algorithms, for example, axis (surface) thin-
ning, edge tracing, etc., becomes more dicult. A large portion of this topic
is devoted to analysis of such topics.

(e) Diversity of density values

The physical meaning of density values is not limited to image subjects and
their recordings, but will vary greatly according to the space they are con-
tained in and the measurement (imaging) technologies used, even when the
same subject is being treated. An example is given in Table 1.1. According to
these factors, the characteristics and content of detected edges, outlines, high
density areas, etc., will be very different.

1.3.4 Objectives in 3D image processing

When processing true 3D images, one must consider whether the 3D image will
be directly manipulated during processing. The following are some objectives
to keep in mind when making that decision: