Designing Web-Based Educational Virtual Reality Environments - Teaching through Multi-User Virtual Environments - page 161

Figure 1. a) The virtual laboratory, b) A virtual experiment. Specifically, the pH is presented on the screen
of the pH-meter. The process completes when the pH value remains almost constant at the equivalent point.

effective and reliable tools for the evaluation of
students' performance.
To this end, medical simulations are considered
nowadays as an integral part of the education
and training of medical students. Especially in
the training of new surgeons, a large number of
simulations are used as valuable educational tools.
The existing surgical simulations can be broadly
classified in three categories (Liu et al., 2003):
needle-based simulations, minimally invasive
surgery simulations and open surgery simulations.
The first category concerns the manipulation of
small medical instruments such as needles, guide-
wires and catheters e.g. the Immersion CathSim
Vascular Access Simulator (Ursino et al, 1999).
The second category, Minimally Invasive Surger-
ies (MIS), involves the insertion of instruments
into the human body from small incisions as in
cases of laparoscopic and endoscopic operations
e.g. the LASSO project (Szekely et al, 2000). Fi-
nally, the third category comprises of open surgery
simulations (O' Toole et al, 1999), in which large
incisions in the human body are required.

Nevertheless, the development of a medical
simulation is a challenging task involving realistic
modeling of human organs, interaction in real time
and modeling of the physical behaviour of medi-
cal models e.g. deformable modeling. Therefore,
the majority of medical simulations used for the
training of medical students require dedicated,
powerful and sometimesexpensive graphical
workstations. Thus, the knowledge extracted
by the use of medical simulations constitutes
a privilege of a limited number of universities,
research institutes and hospitals. This fact, how-
ever, raises questions about the dissemination of
this knowledge, especially to universities that are
not equipped with medical simulations, as well
as the possibility of an educational institution to
obtain an adequate number of simulators in order
to cover its educational needs.
The advent of the World Wide Web and its
broad use opens new possibilities to the training
of medical students providing a solution to the
aforementioned problems. Its combination with
virtual reality technology allows the development