Biomedical Engineering Reference
In-Depth Information
6.6.4.2 Fifth generation systems II
(virtual reality)
However, such a paradigm may not be suitable for visu-
alizing objects of similar or smaller physical scale, as is
often the case in medicine. A more suitable virtual reality
paradigm proposed for such an interaction is the virtual
workbench or virtual work volume concept (
Figs. 6.6-15
and 6.6-16
). A mirror arrangement is placed at a suitable
angle to the stereo display, reflecting the 3D image to the
viewer, so that the viewer, looking at the mirror through
stereo goggles, perceives 3D objects behind the mirror.
The virtual object that appears within the ''reach-in''
distance of the hand can be manipulated exactly where it
appears in the virtual work volume. The 3D stylus or
mouse can be replaced by a suitable visual motif func-
tionally representing the tool in the image. Augmented
reality visualization encapsulates same principles, but
instead of presenting a fully synthetic virtual world, it is
optically superimposed on the real world, so that the
viewer perceives the virtual objects placed in a real
working space. This is useful during an intraoperative
procedure, combining, for instance, a 3DMRI image that
can show subtle differences in the brain tissues with
a real image of the brain during the surgery where the
naked eye would not be able to see the differences very
well. Real-time registration of the actual anatomy with
Virtual reality visualization represents the next milestone
in biomedical visualization. While stereoscopic visuali-
zation provided the 3D perception, such a presentation
also required intrinsically intuitive 3D interaction with
the display. The traditional interaction paradigm using
a tool or stylus such as a mouse or pointer that is away
from the display lacks the intuitive control of hand-eye
coordination. A more natural and intuitive interaction
can be obtained by manipulating the image where it is
perceived in 3D space. This can be achieved with a stylus
using 3D positional sensors. However, placing such
a stylus that the hand can manipulate directly on the
image would obstruct the view of the image.
Some virtual systems overcome this problem by using
helmet-mounted displays that present a virtual world
through stereo goggles mounted to the display. This is
generally called an ''immersive'' virtual reality paradigm.
It may be suitable for representing a virtual world where
the physical scale of the objects is larger than the viewers,
as in architectural visualization, where they can imagine
immersing
themselves
into such a virtual world.
Figure 6.6-16 Presurgical planning: separation of Siamese twins. 3D visualization and 3D interactions in the virtual workspace environment
using MRA and MR volumes to visualize vascular and brain morphology assisted surgeons in devising strategies in planning the extremely
complex and most delicate neurosurgical procedure of separating craniopagus Siamese twins (under the notably challenging circumstance
that the patient was in a distant location and could not be reached prior to surgery). Dec. 1997, Zambia. Pediatric neurosurgeon: Benjamin
Carson (JHU). Software (VIVIAN): Luis Serra, Ng Hern (KRDL, Singapore). Tushar Goradia, James Anderson (JHU).
