Virtual Neurosurgery- Training for the future

wafflejourneyAI and Robotics

Nov 14, 2013 (3 years and 9 months ago)

64 views


1

Virtual Neuros
urgery
-

Training for the future


Michael Vloeberghs
1
, Tony Glover
2
, Steve Benford
2
, Arthur Jones
3
, Peji Wang
3
,
Adib Becker
3
.


1

Academic Division of Child Health, School of Human Development

2

School of Computer Science and Information Techn
ology

3

School of Mechanical, Materials, Manufacturing Engineering and Management,




Correspondence address
:

Mr Michael Vloeberghs, MD, PhD

Clinical Associate Professor

Consultant Paediatric Neurosurgeon

Paediatric Neurosurgery

Nottingham University Hosp
ital

Clifton Blvd

Nottingham


NG72UH

United Kingdom

e
-
mail: michael.vloeberghs@nottingham.ac.uk


Key words:

Virtual reality, Neurosurgical training, Haptics, Boundary elements,
Working times directives.



2

Abstract:


V
irtual
R
eality (VR)

simulators

have bee
n created for various surgical

specialties
. T
he
common theme is extensive use of graphics, confined spaces, limited functionality
and limited tactile feedback. A development team at the University of Nottingham,
UK, consisting of: computer scientists, mech
anical engineers, graphic designers and a
Neu
rosurgeon, set out to develop a haptic
e.g. tactile
simulator
,

for Neurosurgery
making
use of
Boundary E
lement

(BE)

techniques
.

T
he
relative
homogeneity of the
brain,
allows
boundary elements

i.e.


surface only


rendering,

to simulate the brain
structure.
The surface
-
only modelling feature of the BE formulation reduces the
number of algebraic
equations

and
save
s

computing time,

by assuming the properties
of the surface equal the properties of the body.
A limited
audit was done by
Neurosurgical users confirming the potential of the simulator as a training tool.

This paper focuses on the application of the comput
ational method and

refers to the
underlying mathematical structure.
Full references are include
d

regardin
g the
mathematical methodology.


Introduction


The need for surgical simulation is driven by
the limitation in training hours set by
working time directives in Western countries and
increasing litigation in surgical
incidents. The net result is limited tra
ining oppo
rtunities and less chance for
junior
surgeon
s

to acquire the necessary experience

during regulated training
.


3

Hands
-
on s
imulation is well established in aerospace training
,

and audit of simulation
in medicine
has shown
a

decrease
in
the number of

adverse events in actual surgery

(3
0
)
.


Method


In order for surgery simulation to become established

as
training

tool
, VR simulators
need to provide a diverse range of capabilities
, close

to reality (Table 1).

This
simulator
was
focused on the haptic ca
pabilities and to a lesser extent on graphics.
The development team decided
that
graphics are a secondary issue and easily
implemented in comparison to the
real
-
time
BE
computations
.


Table 1: Surgical acts to be simulated in VR.



p業畬慴u⁴
桥⁰牯 e獳映
p畳桩湧⁡湤⁰畬n楮i



p業畬慴u 瑨攠 c畴u楮朠 潲 獥灡ra瑩潮o 潦o 瑩獳略s 楮捬畤楮i 浵m瑩灬p
J
c畴猠 a湤††
楮捩獩潮献



p業畬慴u⁧牡癩va瑩潮o氠摥景f浡瑩潮映瑨m⁣畴⁴楳i略



䅬汯眠A潲⁳o汦
J
c潮瑡o琠扥瑷te渠瑨攠n畴⁴楳i略s



p業畬慴u⁰潳
J
c畴u楮i慮楰畬慴楯



䅬A
潷⁦潲⁴oo
J
桡湤e搠
楮ie牡c瑩潮



䅬汯眠A潲⁣潮瑩湵潵猠n畴瑩湧⁡湤⁳npa牡瑩潮o⁴ s獵sⰠIKg⸠瑯⁲Kac栠h⁴畭潵r



p業畬慴u⁴桥⁣潭灬e瑥⁲e浯癡氠潦⁴ 獳略Ⱐs⹧⸠a⁳ 灡牡瑩潮o⁡⁴畭潵o



m牯癩摥⁡

牥a汩獴sc

灯獩瑩o渠n湤⁰潳n畲u⁦潲⁴ e⁳畲ge潮



啳r

㍄⁳瑥Pe
漠癩獩潮



fnc潲灯oa瑥

s
畲g楣i氠 瑯t汳l a湤n 業灬敭p湴猠 灨y獩捡汬y c潮湥c瑥搠 瑯t 景fce
J
晥e摢dc欠摥癩ves



p桯h

a
cc畲a瑥⁶楳畡氠㍄

浯摥汳⁷楴栠汩g桴⁰牯橥ht楯渠慮搠獨i摯睳



啴楬楳i

p
a瑩e湴⁳灥n楦楣⁶ 牴畡氠l潤o汳Ⱐ攮g⸠晲潭o䵒f⁤ 瑡


4


A Boundary Element virtua
l surgery environment

The BE
-
based
simulator was developed at the University of Nottingham, as a
collaborative research project between the Schools of Mechanical Materials and
Manufacturing Engineering, School of Computer Science and Information
Technology

and School of Human Development
, Division of Child Health (
3
4
, 35
).


Neurosurgery simulation is particularly challenging becau
se it involves interaction
with
the gelatinous structure of the brain and
lesions

of varying consistency.

T
h
is

simulator allows

the user to
operate on an

area of the brain surface, use diathermy

(cutting), retract the brain substance and remove a mass
from
inside the brain
substance.


The s
imulator is based
on
in
-
house created
real
-
time BE software combin
ed with
advanced computer
graphics and
commercially available
force
-
feedback haptic
devices.
(Table 2)

Table 2.
Hardware set
-
up



䄠mC ⡨楧栠獰sc楦楣a瑩潮Ⱐty灩捡汬y ㌠䝈z⤠晩瑴敤f睩瑨wa gra灨楣猠ca牤rcapa扬攠潦
牥湤n物rg″䐠業 来s




浯湩瑯爠c潭灡瑩扬e 睩瑨t瑨攠獴敲e漠癩獩潮osy
獴s洬ma湧汥搠獵s栠瑨慴t瑨攠業a来 楳
牥晬fc瑥搠楮⁡⁳ 浩
J
獩s癥re搠浩牲潲

a湤

a⁶楳畡氠牥f牥獨⁲s瑥映f琠tea獴′㔠䡺



㍄⁓Pe牥漠癩獩潮⁧o杧汥l⁡湤⁩湴e牦ace



呷漠桡灴pc 摥癩ve猠景爠p潳楴楯渠獥湳楮n a湤n景牣e 晥e摢dck a湤 a 桡灴pc 牥湤n物湧r
牡瑥t a牯畮r N
〰〠䡺 ⡣畲ue湴ny 瑨攠pe湳n扬攠 呥c桮潬hg楥猠m䡁乔o䴠佭湩
sy獴敭⁩猠畳敤s


T
F


5










Figure 1: The

surgery simulation hardware
. A custom built rig accommodates the
computer, the haptic devices, the monitor and the reflective semitransparent mi
rror
needed for

stereoscopic vision.


Real
-
time simulation of
Neurosurgery

In practice, neurosurgical operations are
limited to
a small part of the exposed brain,
which
is

identified from
pre
-
operative imaging

e.g. magnetic Resonance Imaging
(MRI). MRI ima
ges can be
imported
directly
into the original visualisation software.
O
nly th
is

part

of the brain

is
rendered

with a fine
3D
mesh
,
wh
ile the other parts
can
remain relatively coarse meshed

to save computing time
.



BE
algori
thms
were

developed
by the auth
ors
for s
imulating the pushing
, pullin
g,
cutting e.g. using a bipolar forceps, retracting and two handed operating generally
used in Neurosurgery.

When

the haptic device is moved by the user, a contact search
algorithm detects which
points

are

in contact.

If the haptic device penetrates the
virtual surface, the penetration displacement is used as a displacement in the BE
software.

The feedback forces are simultaneously computed as rea
ction forces and fed
Replace
with these

?


6

back to the user

via
th
e

haptic device
.
The graphics

are updated accordingly in real
time.


An especially challenging aspect of simulating surgery is the real
-
time simulation o
f
the surgical cutting

i.e.

in
cising the cortex with a bipolar forceps
.
T
h
e initial cut is
created as a gap between existing surfa
ce elements. New surface elements are created
in the direction of the cutting plane, without altering the original surface mesh.
(
Figures 2
-
6
)









(a) Pulling

action







(b) Pushing

action

Figure 2: Examples s
howing pulling and pushing

actions


Replace with this?


7











Figure 3: Example showing the application of two haptic devices









(a) Single retractor (b) Two retractors


Figure 4: Example showing the application of retractors to separate t
he cut surfaces


8







(a) Initiating a cut








(b) Extending a cut


Figure 5: Examples showing an initial cut being extended








Figure 6: Example showing a post
-
cutting manipulation


9


Simulation of removing a tumour

The simulator

allow
s

the surge
on to
cut deeper until a
tumour is reached. The cut can
then continue around the tumour surface until the tumour is totally separated and
subsequently removed. Although the tu
mour is located within the brain
, it can be
simulated as a BE surface in full con
tact with the surrounding
brain
, i.e. the surface
-
only feature of BE modelling is preserved.
Figure 7 shows a wire frame model
containing a tumour underneath the surface.




Figure 7: 3D wire frame of a tumor beneath the surface of the organ


Feedback fr
om surgeons

A

preliminary

evaluation o
f the simulator was performed
. Two initial sessions were
undertaken within the
Nottingham University Hospital (NUH)

where the system was
demonstrated to more than 24 neurosurgical
-
related staff (ranging from

10

neurosurge
ons to theatre nurses). A
more
refined version of the simulator was then
evaluated at a subsequent session in
October
2005 with 13 participants who were
either consult
ants or trainee neurosurgeons.
Participants tried the simulator for a short
period of tim
e (a few minutes each) before giving feedback through a short
questionnaire which gathered their opinions about its realism and potential
improvements

(Table 3)
. The evaluation only addressed prodding and

pinching and
making a few cuts. The working prototy
pe was used with
basic

graphics and only one
haptic device.


Preliminary feedback suggests that the current BE
-
based simulator and the hardware
can achieve a sufficient lev
el of realism to have a useful role
in surgical training.
Participants’ responses s
uggest

that the simulation of pushing felt realistic, but pull
ing
was less realistic since the current system allows an unlimited amount of tissue
stretching. The simulation of cutting, while functional, requires further improvements
in terms of feel and e
xtra features such as simulating bleedi
ng
e.g. augmented reality
would be a useful addition
.



11

Table 3. Results of the VR questionna
ire put to 13 Neurosurgeons, October
2005


(Scoring system: 1
-
5, 1=Very Good, 5=Very Bad)


Question

Mean

Standard
deviation

In general, how easy was the simulator to use?

1.31

0.48

How realistic did the brain look whilst pushing?

2.15

0.55

How realistic did pushing the brain feel?

2.46

0.5

How easy was pushing the brain?

2.08

0.76

How reali
stic did the brain look whilst pulling?

2.62

0.65

How realistic did pinching the brain tissue feel?

2.77

0.6

How easy was pulling the brain?

2.0

0.74

How realistic did the brain look whilst cutting?

3.0

0.82

How realistic did cutting the brain feel?

3.38

0.51

How easy was cutting the brain?

2.38

0.87

How realistic was the stereo viewing?

1.77

0.73

How comfortable was the physical setup?

1.5
4

0.66


Could the simulator help you understand basic surgical acts?






Do you think the simulator has a role in surgical training?







0
1
2
3
4
5
6
7
8
9
10
11
12
13
Yes
No

0
1
2
3
4
5
6
7
8
9
10
11
12
13
Yes
No

12

Discussion


VR in surgery simulation:

The application of VR to surgery simulation was first proposed
in the early
1990’s
(1,
9, 11, 24, 29
)
and
focussed on task simulation. With the increasing computer
processing power and the availability of sophisticated
input/output devices such as

force
-
feedback device
s (
2
6
), surgery simulation

gained

in sophistication and realism
.

T
he lack of sufficient opportunities for trainee surgeons to practice su
rgery and
clinical governance issues
gives

surgical simulators

a role in training
.
Guidelines
regarding surgical competence from the Royal college of Surgeons of England
emphasise th
e parallel between civil aviation training and surgical training and
highlight the role of simulation (
3
0
). Trainees also voice their concern about training
and the time spent exposed to surgery (
10,
19
, 2
3
). In the previous UK training
system, trainees w
ould spend and excess of 30000 hours training in their specialty. In
the Modernised Medical Career (MMC) system, the hours are reduced to 15000
i.e.

50%. In comparison a NASA astronaut trains 10000 hours and a long haul airline
pilot trains 5000 hrs (
10).

Building on previous VR work of the
first
author
, this
simulator uses “Patient specific” data from MRI (
32
, 3
3
). Simulation of an actual
patient is possible and extends the use of the device to the senior level where
simulators have a role in Co
ntinuous Me
dical Training and pre
-
operative

simulation
of complex cases.


VR surgery
is used in many specialties, such as endoscopy
(31
),

microsurgery (
12
),
neurosurgery (
2
8
), urology (
1
4
)
, orthop
a
edic
s
(7
)

and ophthalmology

(
1
7
)
, and is
gradually gaining acceptance
in th
e medical profession
(
13
,
20
)
.

Previous simulators

13

have concentrated on endoscopic surgery e.g. operating in a confined space with
limited freedom, limiting the simulator to confined spaces and “drag and drop”
surgical acts.

This simulator approaches
N
eurosurgery from an “outside in“
perspective

and uniquely allows the user to operate on the surface of the brain.


Real
-
time Boundary Element computations


The Boundary Element (BE) method is well established as an accurate stress analysis
technique in wh
ich only the surface (boundary) needs to be represented

(
see, e.g. 2, 3,
8, 25
)
; this is contrast with the finite element
(FE)
method, which requires
representation of the entire model

(
see, e.g.
4, 5, 6
)
.
The

interior of a BE domain is
not
rendered,

resul
ting in a better resolution of the surface. A recent review of
deformable models for sur
gery simulation by
Meier
et al (21
)

has identified the BE
technique as being one of the most promising routes to surgical simulation
.
.


Two early attempts
,

published by

Jame
s, and
Pai
(15, 16)
and Monserrat

et al

(
2
2
),

to
u
se

BE
to

simulate

deformable objects in V
R

support the

met
hod,
demonstrated the
basic feasibility of this approach, but did not cover the simulation of cutting, post
-
cutting deformation or two
-
handed o
perations. The BE work presented in this paper
has built on this baseline, fur
ther extending the use of BE in

surgical simulation

(
18,
34, 35
).


Conclusion

An overview of a
unique
BE
-
based VR
Neuro
surgery simulator is presented

w
hic
h
features
real
-
time vis
ual and haptic feedback

allowing the user to perform the basic

14

Neurosurgical acts on the brain
.
The research team has created the BE algorithms for
this complex simulation and have proven that
the
surface
-
only
modelling

capability of
the BE techniques
are

highly sui
table for VR surgery
.


Initial trials of the

system by
Neuro
surgeons have indicated that
a sufficient de
gree of
realism can be achieved

and that such simulators can play a useful role in surgical
training. There are

many
challenges to address, w
hich

include more realism by
use of
augmented reality to simulate bleeding, tearing of tissue etc
.



The author
s believe simulation techniques, especially

VR with haptic feed
back as
described in this paper
,

will in part address the concerns raised by train
ing and
governance bodies

regarding training hours and litigation
.



Acknowledgements


The authors wish to acknowledge the financial support of the UK
,

Engineering and
Physical Sciences Research Council (EPSRC) research grant GR/R84030.


R
eferences
:


1) B
athe K, “Finite element procedures in engineering analysis”, Prentice
-
Hall, New
Jersey, 1982.


2) Becker A, “The boundary element method in engineering”, McGraw
-
Hill, London,

15

1992.


3) Becker A and Mihsein M, “Boundary element analysis of gravitational loa
ding on
structures”, Developments in Computational Techniques for Structural
Engineering, edited by B.H.V. Topping, 197
-
204, Civil
-
Comp press, Edinburgh,
1995.


4) Belytschko T, Liu W, Moran B, “Nonlinear Finite Elements for Continua and
Structures”, J. Wi
ley & Sons, New York , 2000.


5) Berkley J, Turkiyyah G, Berg D, Ganter M, Weghorst S, “Real
-
time finite element
modelling for surgery simulation: an application to virtual suturing”, IEEE
Trans. Visualization and Computer Graphics 2004; 10: 314
-
325


6) B
ielser D, Glardon P, Teschner M, and Gross M, “A state machine for real
-
time
cutting of tetrahedral meshes”, Graphical Models 2004; 66: 398
-
417


7) Blyth P, Anderson I, Stott N, “Virtual reality simulators in orthopedic surgery:
What do surgeons think?” J.

Surgical research2006; 131, 133
-
139


8) Brebbia C, Telles J, Wrobel L, “Boundary element techniques”, Springer Verlag,


Berlin, 1983.


9) Cover S, Ezquerra N, O’Brian J, Rowe R, Gadacz T, Palm E, “Interactively
deformable models for surgery simul
ation”, IEE Comput. Graph. Appl. 1993; 68
-
75


16


10) Devey L, “Will Modernised Medical Careers Produce a Better Surgeon?”
British Medical Journal 2005; 331: 1346


11) Delingette H, Cotin S, Ayache N, “Efficient linear elastic models of soft tissues
for rea
l
-
time surgery simulation”, Studies in Health Technology and
Informatics1999; 62: 100
-
101


12) Erel E, Aiyenibe B, Butler P, “Microsurgery simulators in virtual reality:
Review”, J. Microsurgery 2003; 23: 147
-
152


13) Gallagher A, Cates C, “Virtual reality

training for the operating room and cardiac
catheterisation laboratory”, The Lancet 2004; 364: 1338
-
1540


14) Jacomides L, Ogan K, Cadeddu J, “Use of a virtual reality simulator for
ureteroscopy training”, J. Urol. 2004; 171: 320
-
323


15) James D, Pai D “
ArtDefo: Accurate real time deformable objects”, Proc
SIGGRAPH
-
99 1999; 65
-
72


16) James D, Pai D, “A Unified Treatment of Elastostatic and Rigid Contact
Simulation for Real Time Haptics”, Haptics
-
e, the Electronic Journal of Haptics
Research 2001; 2


17)

Khalifa Y, Bogorad D, Gibson V, Peifer, Nussbaum J, “Virtual reality in

17

opthalmology training”, Survey of Opthalmology 2006; 51: 259
-
273


18) Leahy J, Becker A, “A quadratic boundary element formulation for three
-
dimensional contact problems with friction
”, J. Strain Analysis 1999; 34: 235
-
251


19) Lieske B, “Dilemma of a Surgical Trainee” British Medical Journal 2005; 331:
1347


20) Meier A, Rawn C, Krummel T, “Virtual reality: surgical application
-

Challenges
for the new millennium”, J. American Coll. S
urgeons 2001; 192: 372
-
384


21) Meier U, Lopez C, Monserrat C, Juan, Alcaniz M, “Real
-
time deformable models
for surgery simulation: a survey”, Computer Methods and Programs in
Biomedicine2005; 77: 183
-
197


22) Monserrat C, Meier U, Alcaniz M, Chinesta F,
Juan M, “
A new approach for the
real
-
time simulation of tissue deformations in surgery simulation”, Computer
Methods and Programs in Biomedicine 2001; 64: 77
-
85


23) Moorty K, Vincent C, Darzi A, “Simulation Based Training” British Medical
Journal 2005;
330: 493
-
494


24) Picinbono G, Delingette H, Ayache N, “Non
-
linear anisotropic elasticity for real
-
time surgery simulation” Graphical Models 2003; 65: 305
-
321


18


25) Portela A, Aliabadi M, “The Dual boundary element method: effective
implementation for crac
k problems”, Int. J. Numerical Methods in Eng. 1992;
33: 1269
-
1287


26) Schijven M, Jakimowicz J, “Virtual reality surgical laparoscopic simulators”, J.
Surgical Endoscopy 2003; 17: 1943
-
1950


27) SensAble Technologies Limited (2005),
http://www.sensable.com
.


28) Spicer M, Apuzzo M, “Virtual reality surgery: Neurosurgery and the
contemporary landscape”, Neurosurgery 2003; 52: 489
-
497


29) Stava R, “Virtual reality surgical simulator
-

The first steps”, Surgical
Endos
copy1993; 7, 203
-
205


30) Surgical Competence, Challenges of Assessment in Training and Practice, Royal
College of Surgeons of England, The Smith & Nephew Foundation, 11/1999,
ISBN 0902166301


31) Tanoue K, Yasunaga T, Konishi K, Okazaki K, Ieiri S, Kawab
e Y, Matsumoto K,
Kakeji Y, Hashizume M, “Effectiveness of training for endoscopic surgery
using a simulator with virtual reality: Randomised study”, Int. Congress Series
2005; 1281: 515
-
520



19

32) Vloeberghs M, Hatfield F, Daemi F “A Virtual Reality Model
of the Human
Ventricular System”
Computer Integrated Surgery 1997; Suppl ISSN 1092
-
9088


33) Vloeberghs M
, Daemi F, Demeshki J, Hatfield F “A Virtual Reality Model of the
Human Ventricular System”
Minimally Invasive Neurosurgery 1998; 41: 126


34) Wang P,

Becker A, Glover A, Benford S, Greenhalgh C, Vloeberghs M, Jones I,
“Application of the Boundary Element Method to the simulation of surgery
including haptic feedback” Proc. Seventh Int. Conf. on Computational
Structures Technology, Lisbon, 7
-
9 September
2004, edited by B.H.V. Topping
and C.A. Mota Soares, Civil
-
Comp Press, Stirling, paper 100, 2004.


35) Wang, P., Becker, A. A., Jones, I. A. , Glover, A.T., Benford, S. D., Greenhalgh,
C. M.
and Vloeberghs, M., “A virtual reality surgery simulation of cut
ting and
retraction in neurosurgery with force
-
feedback”, J. Computer Methods &
Programs in Biomedicine, accepted July 2006 (in press)..