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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

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Inc., full-color

length

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from

DSC06j

which 640 •~

(Digital

can 400

1024

made

to

and

a

42-de-

pupil.

Arts,

change

to

was

Tokyo,

computer

1600 •~

output

by

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adjusting

computer

monitor,

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control system

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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