tion manager, a graphics generator, and a physical model. The simulation manager ... Volumizer (Silicon Graphics, Inc., Mountain View, CA), we used OpenGL.
Efficacy
of a Virtual
Medical
Students
Hiroshi
Reality
Oyama,;
Takehiko Department
Simulator
Tomohiro
Nakamura,; of Medical
Kuroda,;
Takashi
Informatics,
for
Kenta
Evaluating
the Aptitude
of
Hori,;
Takahashi
Kyoto
University
Hospital,
Kyoto,
Japan.
OBJECTIVE: Our goal was to develop a system using virtual reality (VR) technology to test the haptic skills of medical students. Currently, surgical skills are learned on live patients in a clinical environment in which the student practices under the close supervision of an experienced surgeon. We are interested in using haptic feedback devices to enhance surgical skills, because simulated touch in a virtual world improves the performance of trainee surgeons. In this study, we evaluated the efficacy of a test that evaluates the surgical skill of medical students by using a VR simulator. METHODS: We used a microsurgical simulator with a force-feedback system. Its effectiveness in helping 36 medical students to acquire the tactile skills used in microscopic surgery was evaluated experimentally. Operating time and the number of sites of hemorrhage were measured to evaluate surgical aptitude. We also evaluated system performance with respect to reality, immersiveness, and operability as secondary measures. lyzed using descriptive methods.
Data were ana-
RESULTS: The operating time and number of hemorrhagic sites were positively correlated. Subject students were clustered into three groups: dexterous, awkward, or clumsy. The relation between the number of hemorrhages in the retina and immersion and operability differed between the group of would-be surgeons and those of would-be internists and pediatricians. All the students commented that the simulator was a useful tool for medical education. CONCLUSIONS: The VR simulator can be used not only to teach and evaluate subtle tactile and surgical skills relevant to the surgical profession, but also to test the aptitude of medical students. The training transfer from a haptic simulator to actual practice methodology should be quantifiable in the near future. This work has steered medical informatics research into a new type of medical education. KEY WORDS: aptitude, education, training, surgical skill, virtual reality Gen Med
EFORE
B
2001; 1: 17-23
graduation,
their brains surgery,
before
internal
many deciding medicine,
medical
students
on a specialty, and
so on.
rack such as How-
ever, not all medical students are suited to all specialties. Their choice of specialty not only affects their subsequent life as a doctor, but also has major implications for their patients. There are three sides to medical education: acquiring medical knowledge, mastering
clinical techniques,
and developing the attitude
necessary for the medical profession. If a clumsy surgeon operates on a patient, the risks associated with the operation increase. If possible, it would be ideal to determine the dexterity of medical students subjectively and objectively before graduation. This study examined whether it is possible to evaluate a medical student's dexterity using a microscope surgical simulator with virtual reality (VR) technology. Progress in VR technology in the past few years has led
Address correspondence to Dr. Hiroshi Oyama: Department of Medical Informatics, Kyoto University Hospital, 54 Kawahara-cho, Shogoin, Sakyo-ku Kyoto, 606-8507, Japan. Phone & Fax: 81-75-751-3647, E-mail: hoyama®kuhp.kyoto-u.ac.jp
18
General
Medicine,
Vol. 2, No.
1, 2001
to the development of inexpensive equipment that transmits elastic forces with high efficiency. This has been applied to the development of medical simulators. Hoffman et al. developed a medical educational system that uses VR space and reported on its usefulness in anatomy education [1,2]. They pointed out that VR technology improves the three-dimensional understanding of anatomy and facilitates self-learning. Rosen et al. developed a method of examining surgical skills using an endoscopic simulator and proposed a Markov model for this [3,4]. In this way, the latest computer technology has been applied to the evaluation of surgical skills, not just to knowledge processing in the context of evidence-based medicine. To the best of our knowledge, Tracey and Lathan are the only group of investigators who have evaluated space and movement functions using a VR simulator [5]. The use of a VR simulator to evaluate the dexterity of medical students has not been examined. In this study, we examined the dexterity of medical students by using a VR simulation of a microscope operation, and here report its usefulness.
MATERIAOLS
AND
Figure 1
Main The
main
(Pentium III
Visual 1
display
an
Intense
ic used
MHz,
WildCat
Computer
resolution
was
866
VA)
one-inch
CRT
x 480
4000 Systems,
was
Windows
NT
a PrecisionTM
1024 •~ as
the
graphic
512
AL).
(16,700,000
operating
by
Mbyte)
accelerator
Huntsville, 1024
made
and
The colors).
of
used
Dell
converter, range
of
tem,
1280 •~
Foot
switch
We
of a WinGuard
with
6 mm
(n-Vision
display 50-cm
which
was
a
focal
the
Inc., full-color
length
corresponded
from
DSC06j
which 640 •~
(Digital
can 400
1024
made
to
and
a
42-de-
pupil.
Arts,
change
to
was
Tokyo,
computer
1600 •~
output
by
It
adjusting
computer
monitor,
a
A pedal
control system
The system consisted
The
1200
Japan)
output
pixels.
over
In
transformed
to
our
640 •~
a sys-
480.
graph-
system.
Corp., Tokyo, Japan) with one AMD-K6, MMX CPU, and 64 Mb of main memory.
used.
view
footswitch.
Haptic feedback
simulation binoculars
Converter
with (Inter-
were
resolution,
field
inertia mass was 170 g or
for virtual
McLean,
2
2 CPUs,
equipment
VGA-output-type
640
presentation
system
Microscope
We computer
The maximum
power was 10 N. The operation less.
computer
Co.
graph
system
simulator.
of at least 60 degrees around each axis, from the
center of the operative field.
gree processing
of the microsurgery
Sensory display system Haptic feedback system The flexibility specifications allowed 75 mm of right and left movement, at least 50 mm up and down, and rotation
METHODS
Configuration of the VR simulation system The VR system was divided into three subsystems: information processing, sensory display, and real-time sensing systems. We used a surgical simulation system made by Mitsubishi Electric Co. and Mitsubishi Precision Co., Ltd. (Fig. 1). In this system, the virtual model consists of a surface model that allows the user to experience the tactile feel of a virtual elastic body in virtual space. Information
Photograph
the
has
Mitsubishi nine
focus,
Precision
controls,
suction,
was
including
lighting,
used
as
controls
and
field
of
the for
view.
(MTT
233-MHz
The
real-time
A position ure
sensing
real-time
the
of
system
sensing the
coordinates
system
microscope of
was in
surgical
the tools
used
to
system in
determine and
simulation
to
the measspace.
H. Oyama et al.
Software There were three main software
packages:
A VR Simulator
for Evaluating
the Aptitude
of Medical Students
19
a simula-
tion manager, a graphics generator, and a physical model. The simulation manager synchronized the 100-Hz psec required
for the drawing speed of 30 + fps required
space, and the tactile sense presentation tion. Since PrecisionTM is not compatible
in VR
in the simulawith Performer
(Silicon Graphics, Inc., Mountain View, CA) or Volumizer (Silicon Graphics, Inc., Mountain View, CA), we used OpenGL. Study design: Purpose This study
was designed
to use a VR system that
simulated the tactile feel and elasticity of the eyeball and
Figure 2
A medical
Figure
User
student using the microsurgery
simulator.
pre-retinal membrane in simulation space, to evaluate the dexterity of medical students performing virtual surgery.
Subject characteristics The subjects were fifth-year medical students at Kyoto University Medical School, who had no previous experience of using a VR simulation with elasticity. Thirty-six of the 100 fifth year medical students were selected for the study after introducing the class to the VR system, and these subjects were examined over a threemonth period. Endpoints The subjects were asked to look at the eyeball and retinal membrane in the virtual microscope, and to perform an operation to remove the pre-retinal membrane using the virtual instrument with the right hand. The associated pathology included retinal vascular diseases, retinal tears, and so on (Figs. 2, 3). In this study, performance was evaluated by determining the number of hemorrhage sites caused by the exfoliation instrument coming into contact with the retina during the operation, and by the time that the operation took from start to exfoliation of the pre-retinal membrane using the virtual tweezers through the virtual microscope. The reality of the system, i.e., the feeling of immersion and operability, was measured using a VAS (visual analogue scale), and analyzed statistically. Finally, the students were given a questionnaire and their comments and subjective impressions were elicited. The method of analysis The questionnaire was analyzed descriptively using SPSS ver. 10.0 (SPSS Inc., Chicago, IL).
3
interface
of
the virtual
microsurgery
simulator.
RESULTS Statistical analysis: The characteristics of the 36 subject students (33 men and 3 women) are listed in Table 1. Of these students, 8 were planning to specialize in surgery, 8 in internal medicine, and 2 in pediatrics; 18 were undecided. Table 2 shows the study results according to the specialty to which the subject students were aspiring. The statistical analysis of the number of hemorrhages due to contact with the retina and operation time is shown in Fig. 4. Although the time required to extract the pre-retinal membrane was positively correlated with the number of hemorrhages, the correlation was not statistically significant (r=0.313, p=0.065). Generally, the operation took longer for the students who caused many
20
General
Table 1
Medicine,
Characteristics
* The simulation
system
Vol.
2, No.
of the students
had
a function
1, 2001 examined.
by which
the program
stopped
hemorrhages. In the group of would-be surgeons, the operation time was relatively consistent, and was not related to the number of hemorrhages, while for the would-be internists, the operation time increased with the number of hemorrhages. Table 3 shows that there was a positive relationship between the clinical and educational value and the number of hemorrhages. There were fewer hemorrhages when the subjects perceived the simulation as real. There was no significant difference associated with the subject students' choice of specialty. In the group of would-be internists, the number of hemorrhages increased with the feeling of immersion, unlike in the surgery and undecided groups. Students who thought they performed well had fewer hemorrhages. For the would-be internists, there
automatically
was
when
a negative
number
tem
to
be
smaller
for
the
The
number
students
who
bleeding
reached
operability of
five .
and
the
hemorrhages
evaluated
the
sys-
highly.
evaluation
Comments think
from
it quite
simulators,
more
more
subjective to
of
think
that
ophthalmology surgical
mimic
an
(23-year-old
system
residents. subspecialties
skills
using
if the
simulators
operations,
simulation this
included: •gI
surgical
and
realistically•h
evaluation
teach
actual
realistic
undecided). •gThe
other
the
possible instead
become
to
of retinal
between
hemorrhages.
Subjective
I
of sites
correlation
of
tended
the number
actual
operation
male, experience
is
very
I hope and
specialty was
useful
pleasant.
for
that
it
put
into
such
can
teaching be
practical
applied use•h
H. Oyama et al. Table 2.
A VR Simulator for Evaluating the Aptitude of Medical Students
21
Study results according to the specialty that the subject students were aspiring to.
I: The group of students
who were aspiring
to become
internists
S: The group
of students
who were aspiring
to become
surgeons.
U: The group
of students
who were undecided
on their future
or pediatricians. specialty.
interesting•h Many
(23-year-old students
male,
also
system;
these
included
unclear
images,
and
pointed poor the
heaviness
aspiring out
internist). weaknesses
three-dimensional of
the
of
this
effects, apparatus.
DISCUSSION
Figure 4 Plot of the number of retinal hemorrhages versus operation time. The number above each point is the subject number.
(23-year-old would
woman, like
student. cause
I they
simulators•h was
to
difficult
envy will
aspiring
experience the have
(24-year-old to perceive
ophthalmologist). •gI
many next
more
generation
many
VR
systems
of
students,
opportunities male,
depth,
to
aspiring but
the
use
as
a be-
such
surgeon). •gIt
simulation
was
very
Teaching medical skills, such as how to give an injection or insert a catheter, is an important aspect of medical education. Medical students have to learn these skills experientially, on patients in an actual clinical environment. To learn to detect abnormal internal organs on palpation, for example, they need to have experienced the tactile feel of normal internal organs. Surgical residents can learn to dissect and suture during operations, but only on a limited number of actual patients. To overcome these problems, cadavers are occasionally used. However, the number of cadavers is also limited, restricting the number of doctors who have such training opportunities. This study identified three groups of medical students based on their aptitude: dexterous, awkward, or clumsy. Moreover, in the group of would-be internists, the
22
General
Table 3
**p