VIRTUAL DIAGNOSIS
by Carl Gawith

	Imagine for a moment that you have been 
reduced to the size of a red blood corpuscle. That 
would make you just the right height to go walking 
through one of your own unreduced capillaries. 
Suppose, also, that it's a few years from now, that 
you've been diagnosed as having an aneurysm on a 
blood vessel in your brain, that the doctor feels 
there is no alternative to surgery if you are to 
avoid the inevitable result of a rupture in that 
vessel, and that your chances of surviving the 
surgery are just about even.
	Imagination is great, isn't it?	
	Since we agree on how fine imagination is, 
maybe we can use it to help you decide whether the 
surgeon should start cutting. Since we also agree 
that the time is in the future, we can use a 
technological development that will become 
generally available any year now: real-time virtual 
imaging of a human body; yours, in this case. And 
that advance will let you take the walk I mentioned 
earlier. First, though, let's cover some background.
	Virtual imaging, or virtual reality (VR), 
is the use of a computer to see a simulated object 
or objects from a position that we do not occupy, 
while keeping the viewing options (and more) that 
we would have if we were really there. The "real-
time" aspect comes in when we use VR software to 
view something that exists, seeing things that are 
actually happening as we watch from our new 
position, with full freedom of movement.
	We can choose to turn to the left at any 
time, and the scene on our monitor will reflect the 
change in view that would accompany a turn like 
that in the real world; an object that was ahead 
will slide off the right side of the screen. We can 
decide to move forward, and a person or thing that 
is in front of us will appear to become larger.
	That kind of activity, by itself, would 
rapidly lose most of its entertainment value. 
Besides, logic tells us that it would be less 
expensive, not to mention easier, to just walk, 
drive or (possibly) even to fly in our desired 
direction of travel than to go through all that's 
required to simulate motion in the computer.
	I set up this scenario for the specific 
reason that it is not always easier to do those 
things in the real world; in fact, it's sometimes 
impossible.

Get the client involved
	The architect who creates a design for an 
office tower knows it is vital to involve the 
client in the concept. Usually that has been done 
by making a small-scale tabletop model that the 
customer can walk around, getting a feel for the 
look of the building and how it will blend or 
contrast with structures in the area. Often it's 
necessary to construct a part of the interior 
space of the new building in a warehouse, so that 
those who will be approving the project can "live" 
in their new office complex and get acquainted 
with its interior space relationships.
	How much money and time do you suppose 
could be saved by constructing a new building 
entirely within a computer's memory, then entering 
the front door of this digital building and 
visiting any office? All before the commitment to 
lay a single brick has been made?
	This approach is being used today in 
designs ranging from airliners to zoos.

Well, back to the cursor tablet	
	The world's largest manufacturer of 
commercial jet aircraft is currently flight-
testing an entirely new airliner. With engines 
roughly the diameter of many airliners' bodies, 
it was developed in engineering departments that 
had no drawing boards. That's a result of the use 
of computer-aided design (CAD), but a side benefit 
of this technology is that, for the first time, 
the manufacturer has developed an airliner without 
physical structural and systems mockups.
	For those who aren't familiar with the 
term, a mockup was an assembly that simulated part 
of the finished plane. Structural mockups showed 
how the load-bearing elements of the design would 
fit together while allowing for necessary 
complications such as electrical, hydraulic, and 
air conditioning systems. Specialized mockups were 
built to check the operation of doors and controls, 
or to be sure that it would be possible for a 
worker to reach a component for installation or 
maintenance. The mockup was built from wood, 
plastic and/or metal, and filled an area in the 
plant large enough to hold the same part of a real 
airplane.

	No more. Mockups now exist only in computer 
memory, but they're used in the same way as the 
dusty, space-hogging physical mockups of the past. 
It's fascinating to watch the monitor while a three-
dimensional human shape slides past ducts and 
structure toward an electronic component, possibly 
demonstrating where changes in access provisions 
need to be made.
	A computer graphics file in work is called 
a model. A VR model can be effective for studying 
traffic flow or the relationship of elements to 
their system.
	Of course, in basic VR the user's interface 
with the model is purely visual, and even that 
contact takes place through the limited field of 
view provided by a computer monitor. But what if it 
were possible to feel a wall with your hand, to 
kick a closed door with your toe, and to limit 
total visual input to the model? With an adequate 
interface, you could do almost anything in the 
model that could be done in the real world.
	That interface exists. A helmet replaces 
the monitor, and the user's hands and feet are in 
data gloves and boots, where they make inputs to, 
and receive stimuli from, the program. Since the 
helmet contains a separate image source for each 
eye and tracks head and eye movement, the 
application has the ability to create a perception 
of depth and to use an accurate viewing point and 
angle.
	Even arcade games are beginning to sprout 
VR features, and it won't be long before you can 
pay your money and take part in some famous 
historical battle.
	All of which, of course, has nothing to do 
with the walk through your capillary we discussed 
earlier, except that any who were unfamiliar with 
the concept may now have a better feel for virtual 
reality.

If it's Friday, this must be the left lobe
	The live tour of your brain's circulatory 
system will be possible when we can feed into a VR 
program the data generated (as it's being used) by 
a medical scanner, creating a three-dimensional 
model of a part of the human body. So just imagine: 
you're hiking along inside one of the capillaries 
of your own brain. The walls alongside are close 
enough that you can nearly touch them both at once; 
then you begin to notice that the corridor is 
becoming roomier. You can see that the tube ahead 
has a visible bulge; in fact, as you step out into 
this aneurysm, it's so wide and high that at your 
present apparent size it looks like that airliner 
we were just talking about could fly through there, 
and the wall 
thickness at its thinnest point resembles the film 
of a soap bubble.
	One look at how that vast balloon compares 
with your normal blood vessel may be all that's 
needed to help you decide in favor of surgery, as 
well as giving you a reason to appreciate the value 
of real-time virtual imaging.

		Copyright 1995 SeeJay Publications