Patient-Specific Vascular Modeling - Microsurgery: Advances, Simulations, and Applications - page 79

area from a set of cross-sectional images. As a result, doctors are
able to recognize three-dimensional shapes of a disease and to
provide an adequate diagnosis and treatment policy. Moreover,
three-dimensional data obtained by this re-composition can be used
for evaluations of dynamics of the living organ and blood stream and
for the development of VR (virtual reality) simulators.
Here, the following method is used to reconstruct the three-
dimensional shape of the object from these two-dimensional data:
First, extracting the area of interest by applying a speciic threshold
to each two-dimensional image. Then, the obtained images are
supplemented in a three-dimensional data set of the region of
interest. Moreover, the blood vessel accurate shape acquisition
relies on pursuing the continuousness of the CT value. We adopted
the method of composing the shape of the brain blood vessel by
designating a threshold on each individual luoroscopic image taken
by CT and MRI.

3.3.1 Medical Imaging Modalities

The following sections detail the methodology for reconstructing
the three-dimensional shape of targeted vasculature from CT/MRI
or other medical imaging modalities as a fundamental procedure
for the patient-speciic vascular reproduction. This section outlines
the major medical imaging modalities, which are applicable to the
proposed modeling.
Single-slice CT: X-ray CT was introduced by Hounsield in 1973
[2]. X-ray CT of the irst generation required a few minutes to take
one picture, and the reconstruction operation required more time.
As a result, it was applicable only for head, which is able to remain
stationary while taking a picture. In the second generation, the time
required was shortened to 10-20 seconds by adopting fan beam
instead of the pencil beam, and taking a picture with two or more
detectors, although it adopts translate/rotate modality as well
as the irst generation. In 1985, the introduction of the slipping
ring mechanism made it possible to rotate the X-ray emitter. Thus
the X-ray CT of the third and fourth generations were clinically
introduced. As a result, a high-speed, continuous imaging became
possible, and such improvement spread the CT system to various
clinical applications.