P oceedings
o
he
1996
IEEE
In e na ional Con e ence
on
Robo ics and Au oma ion
Minneapolis, Minneso a
-
Ap il 1996
Au oma ic Guidance
o
an Assis an Robo in1 Lapa oscopic Su ge y
A. Casals and
J.
Ama
Dep.
o
Au oma ic Con ol.
Uni e si a Poli 6cnica de Ca alunya
Pau Ga gallo,
5
08028 Ba celona (SPAIN)
phone: 34 3 4016974; ax:34 3 4017045
e-mail:[email p o ec ed]
Abs ac
A
obo ic a m au oma ically guided o handle he came a
in lapa oscopic su ge y is p esen ed. The goal
o
his
wo k is o gene a e he adequa e came a con ol
s a egies o ack he wo king scene du ing a su gical
p ocedu e. The sys em is based
on
he compu e ision
analysis
o
he lapa oscopic image ha
allows
o iden i&
ei he a scene's ele an poin , o he su gical
ins umen s.
1
In oduc ion
In he las yea s, signi ican esea ch e o s ha e been
done
in
he de elopmen
o
echnology o minimally
in asi e su ge y
[I],
and mo e speci ically in lapa oscopy
[2,
31.
The ex ended use o lapa oscopic echniques has
demons a ed ha he e a e s ill impo an limi a ions in
i s p ac ical applica ion.
Lapa oscopic su ge y equi es he in oduc ion in o
he pa ien abdomen o se e al ins umen s, he su gical
ools, as well as he TV came a mic oop ics, he
lapa oscope, o p o ide he su geon wi h he isualisa ion
o he in aabdominal wo king space.
A
good cen ing o
he came a ield
o
iew on o he in e es zone is essen ial
o ope a e e icien ly. The mo emen o he came a p obe
o adequa ely ack he in e es zone can be done by he
su geon himsel o by an assis an . In he la e case, a
ce ain expe ience and a su geon-assis an mu ual
unde s anding is necessa y, al hough usually di icul o
ob ain. In he o me case, he di icul y a ises om he
need o he su geon o mo e he came a suppo while
wo king. Consequen ly, some e o s ha e been done
E.
Lapo e
Cen e Qui u gic Ad ia
Vallmajd
34-36
0802
1 Ba celona (SPAIN)
phone: 34 3 20161 11; ax: 34
3
4146128
owa ds he au oma ion o hese mo emen s unde he
su geon supe ision.
Some obo ic manipula o s unde human con ol ha e
been de eloped and es ed. In
[4]
a six deg ees o eedom
manipula o con olled by he su geon by means o a oo
pedal is desc ibed. O he manipula o s ha e al eady been
designed and es ed using di e en in e aces o ecei e
he su geon o de s, ei he h ough o al commands o
by
means o head mo emen s
[2,
51
o eleope a ed
[6].
Addi ionally, a easibili y s udy in he use o image
p ocessing and o he human-machine ele obo ic
command in e aces ha e been published
[7].
This pape desc ibes an expe imen al obo ic sys em
designed o au oma ically guide, by means o compu e
ision, he lapa oscope du ing a su gical p ocedu e. In
his i s expe imen a ion phase a con en ional indus ial
obo , Sca a ype, has been used, bu
in
he nex u u e we
will de elop a speci ic obo
so
as o educe he sys em
cos as well as o minimise he occupied space wi hin he
ope a ing hea e. Fu he conside ing he obo space
educ ion and wi h he aim o elease some mo e ee
space o he su gical eam, he obo ha holds he
lapa oscope has been mo ed away om he pa ien , using
a link ha ansmi s he obo end e ec o mo emen s.
2
Sys em S uc u e
The expe imen al sys em consis s
o
a came a p obe
held by a obo ., he lapa oscope, he ision sys em o
scene analysis and he con ol sys em o gene a e he
obo ajec o ies. The sys em con igu a ion is shown in
igu e
1.
The ca ne a mo emen s a e con olled om he
0-7803-2988-4/96 $4.00
0
1996
IEEE
895
e o signals de ec ed by he image p ocessing sys em in
he cen ing o he scene, acco ding o he ope a ion mode
desi ed by he su geon.
The lapa oscope mo emen s a e es ic ed o ou
deg ees o eedom due o he cons ains imposed by he
ope a ion h ough he oca ,
T.
This beha iou
co esponds
o
ha o a passi e cylind ical join loca ed in
a ixed poin . Due o he elas ici y o he pa ien 's
abdominal walls, he abo e men ioned cylind ical join
has addi ionally
wo
passi e deg ees o eedom, hus
p o iding he equi ed ou d.0. . The esul ing ou
deg ees
o
eedom a e h ee o a ions
cp,
w
and
0
and he
p isma ic mo emen
p,
as shown in igu e 2.
Beha iou
pa ame e s
P-
Fig.
2
Lapa oscope deg ees
o
eedom
Al hough he lapa oscope o a ion
0
can be use ul o
a be e cen ing o he image, i p oduces a o a ion
o
he
isualised image on he sc een wi h espec o he su geon
e e ence wo king ame. This change demands a men al
e o
om
he
su geon
o
keep
his
o
he
ope a ing
abili y. Fo his eason many su geons, among hem hose
o he esea ch eam wo king in his p ojec , impose he
a oidance o his o a ion. This cons ain p oduces ce ain
di icul ies in he manual guidance o he lapa oscope, bu
on he o he way, simpli ies mechanically he link
be ween he obo and he lapa oscope in he au oma ic
mode. The obo hus equi es only h ee deg ees o
eedom.
3
The
Vision
Sys em
The ision sys em de eloped is ui o he wo ks
ca ied ou in he depa men in he las yea s on eal ime
image p ocessing and acking
[8].
In his applica ion he
basic image p ocessing equi emen s a e he iden i ica ion
and he
3D
acking o he su geon ools.
The isualisa ion echniques cu en ly u ilised a e
ei he he classical
2D
moni o ing sys ems, o he 3D ones
based on he use o lapa oscopes wi h se s o double
Hopkin lenses and pola ised eyeglasses. The au oma ic
guidance sys em de eloped can be applied no only o 3D
moni o ing sys ems, bu also
o
2D ones, p o ided ha
besides he iden i ica ion and acking o he su geon
ools, he 3D in o ma ion is in e ed om he appa en ool
size.
This ision sys em is based on he ex ac ion o a e y
elemen al se o ea u es ob ained om he isible
su gical ools, bu e ec i e enough o assu e he
minimum obus ness equi ed. This se o ea u es mus
be
in a ian wi h espec o he
ools
posi ion and
o ien a ion in he image, as well as o zooming. Wi h his
aim, he image cha ac e is ics selec ed ha e been he lines
conside ed as s aigh . The image con ou lines ha ing a
leng h g ea e han
8
pixels and aligned wi h a dispe sion
bounded o
+1
pixel a e de ec ed as s aigh lines.
To assu e he isualisa ion o a leas one s aigh line
co esponding o a ool, in condi ions o possible low
con as , he ools ha e been s amped wi h speci ic ma ks.
In a i s e sion, hese ma ks consis ed
o
some
ho izon al s ips
[9],
ha a e wa ds ha e been changed o
wo
s aigh lines along he ool axis. In his way, a leas
wo
edges can be de ec ed and om hem he ool loca ion
and o ien a ion can be de e mined wi h much mo e
p ecision o e he image plane. Addi ionally, a ing ma k,
loca ed a he ool od end ( ig.
3),
is
u ilised o he
calcula ion o he ool
3D
posi ion om he measu e
o
i s
diame e .
The p ocessing algo i hm de eloped o he compu e
ision sys em consis s
o :
Edges
ex ac ion.
Since he images o be p ocessed
can p esen low con as and he use o edge images
acili a es he isualisa ion and loca ion o he su gical
ools, he p ocessing algo i hm ope a es om edges
images. The implemen a ion
o
his ope a ion using
he same compu ing acili ies as he es o he
p ocessing, adds a new p ocessing ime ha inc eases
he sampling pe iod and consequen ly wo sens he
closed loop con ol esponse. Fo ha eason we use a
dedica ed p ocesso o implemen his ope a ion in
eal ime. In his p ocessing s ep, a il e using a
4
x
4
pixels ma ix
is
also implemen ed. This il e
896
elimina es an app eciable amoun
o
i ele an
in o ma ion, hus sho ening he pos e io s eps
p ocessing imes.
S aigh lines ex ac ion.
The nex p ocessing s ep,
s aigh lines de ec ion, allows o ex ac some image
ea u es o de ec he ool o ools appea ing on he
scene. The implemen a ion o his p ocessing has been
done using an indus ial
PC
o a good e iciencylcos
a io, as well as good eliabili y. The s aigh lines a e
de ec ed as alignemen s o pixels using window
ope a o s o up o
8
pixels size. The esul s a e qui e
sa is ac o y ha ing a p ocessing ime less han
100
ms.
Tool
de ec ion.
Once he non aligned con ou s ha e
been il e ed, hose ha e i y some de ined
condi ions a e conside ed as pe aining o ools. The
algo i hm o de ec ools sea ches pai s o s aigh
lines, candida es o being conside ed ools, ha
coming om he scene pe ime e con e ge, wi hin he
limi s o he pe spec i e dis o sion de i ed om he
u ilised op ics, owa ds he cen e o he image. In
o de o ensu e he sys em obus ness, only he
de ec ions ca ied on close o he p e ious de ec ion
ool posi ion a e conside ed. O he wise, he sys em
alida es he pai s
o
lines as ools, only a e he
e i ica ion o mo e se e e geome ic condi ions o a
gi en numbe o successi e de ec ions. This
e i ica ion mus be done a e a sudden ool
mo emen , when he i s p oximi y condi ion does
no apply.
Measu emen
o
he
ool
ip posi ion, i s
size
and i s
o ien a ion.
The ool ip posi ion, o ien a ion and size,
allows o de e mine he
3D
posi ion
o
he image
in e es cen e poin . The hi d dimension, when using
only one came a, is calcula ed om he measu e o he
ool diame e , which
is
measu ed om a cylind ical
ma k, in a ian
o
o a ion, a he lapa oscope ool
handle. The ob ained posi ion and o ien a ion is used
bo h, o guide he obo ajec o y and also o eedback
his da a o he de ec ion module, o inc ease
obus ness.
e
F om he ooll posi ion ob ained app oxima ely e e y
200
ms i is possible
o
ack he
ools
and o gene a e he
adequa e con ol o de s wi h a sampling ime sho
enough o gua an y he acking
o
he scene zone o
in e es wi h enough eliabili y.
4
Con ol
S a egy
One o he main p oblems o sol e, o adequa ely
guide he obo du ing an in e en ion, is o es ablish he
con ol s a egy ha dynamically de e mines he
lapa oscope posi ion which is eally e icien o he
su geon a e e y ins an . Essen ially, he e a e
wo
p oblems o sol e o adequa ely con ol he came a poin
o iew. Fi s , o de e mine he lapa oscope x, y posi ion
in he image and second i s dis ance (zoom).
4.1
Lapa oscope Posi ion Con ol C i e ia
A e he obse a ion o he mo emen s ha he
assis an uses o pe o m unde he su geon equi emen s
and o he di e en si ua ions appea ing in a di e se se
o su gical in e en ions, we ha e es ablished a se ies o
ules. The signi ican si ua ions conside ed a e:
a) exis ence o e he scene
o
wo mo ing su gical
ools
b) exis ence
o
a mo ing ool and ano he auxilia y
ool ela i ely s eady
c) exis ence o a unique
ool
In he abo e h ee cases he cen ing
o
he scene ha
esul s mo e e icien o he su geon has been shown o
obey he same common c i e ia. These c i e ia ha e been
used
o
de ine he sys em beha iou .
a) acking
o
a scene wi h wo ools
When he sui geon ope a es wi h wo ools o e he
wo king scene, he ision sys em de ec s and acks hem
by means o he de ec ion o he supe imposed ma ks. In
his case he scene cen e poin is conside ed o be he
cen al poin o !he segmen de ined by he wo ools end
poin .
A
il e ing algo i hm
is
equi ed
o
s abilise he
image, ins ead o acking ins an aneously he mo emen s
de i ed om he su geon wo k ha de e mine he scene
zone
o
in e es .
b) acking
o
a scene con aining a wo king
ool
and an
auxilia y s eady one
When he wo ma ked ools appea ing on he scene
do
no ha e he same mobili y, bu one o hem mo es
meaning ully mo e
han
he o he , he p e ious c i e ion
does no apply.
In
his case, he image cen e zone is also
Fig.
3
Su gical ma ked
ools
897
a poin loca ed in he segmen de ined by he
wo
ools
end poin , bu his poin is close o he
ool
ha mo es
as e . The dis ance conside ed o his ool
has
been
113
o
he de ined segmen .
c) T acking
o
a scene con aining only one wo king ool
When he obse a ion a ea con ains only one ma ked
ool he poin selec ed as image cen e is no exac ly he
ool ip, bu i is shi ed a s ep o wa d.
4.
2
C i e ion o he Selec ion
o
he Adequa e
Zoom
Fac o
Besides he cen ing o e he mos in e es ing zone,
an addi ional pa ame e ha de ines a good image o he
wo king scene is he op ical ape u e angle; he zoom.
The mos adequa e ape u e angle a ies widely
depending on he habi and p e e ences o he su geon.
Fo ha eason, he c i e ion aken o au oma e i s con ol
is
o
modi y he zoom,
so
as
o ensu e ha he ool does
no disappea om he came a ield bu espec ing he
su geon equi emen s. Thus, he inc easing o dec easing
o he zoom is done au oma ically om an ini ial zoom
posi ion gi en manually and aken as an o de pa ame e .
F om his pa ame e , he inal zoom alue is he a io
be ween he isible ool o ools and he size o he whole
scene. This a io is aken a he in e en ion ini ial ins an
o a any momen
in
which i can be manually ede ined.
Ei he he posi ion e o unc ion &,,( ) o he zoom
E,
( ) alues mus be il e ed o gene a e he obo a m o de s
o he lapa oscope guidance.
4.3 Fil e ing
o
he E o Func ion
The acking o he ool o ools end e ec o , allows o
calcula e he e o unc ions
E
( ) co esponding o he
di e ence be ween he
3D
measu ed posi ion o he
image cen e poin and he desi ed e e ence posi ion.
This
las posi ion is de ined om he c i e ia de ined
in
poin s
4.
1
and
4.2.
This e o unc ion could gene a e di ec ly he o de s
o he came a guidance obo , bu he ob ained
mo emen s a e con inuous and equen ly oo sudden.
This op ion would cause i edness o he su geon. He
p e e s some momen a y displacemen s
o
he a en ion
cen e poin
in
exchange o a g ea e s abili y and
so ness o mo emen s.
The implemen ed il e ing, ha has p o ided a good
comp omise e iciencylso ness accep able by he su geon
c i e ion, has been a nonlinea ype wi h dead zone and
hys e esis. The il e beha iou is as ollows. A e he
dead zone is su passed he sys em ends o cancel,
ollowing a p opo ional law, he mean e o measu ed,
only
in
case he ins an aneous alue does no o e comes
some de ined bounda ies. O he wise, he il e ing is
subs i u ed by a acking, in o de no o loss he acked
ool o ools. This beha iou p o ides a su icien
s abilisa ion when, du ing he ask execu ion he ool
mo es ela i ely sligh ly wi hin he scene. On he o he
hand, he il e p oduces a quick enough dynamic
esponse
,
and wi hou oo big a delay, when he
ool
suddenly changes he wo king poin . Figu e
4
shows a
sequence o he his e o
E
( ) e e ed o one axis, du ing
he execu ion
o
a ask. The e, we can obse e ha he
e o s
do
no e u n suddenly o
0,
bu hey luc ua e
a ound his alue bu wi h a mo emen so e ha ha o
he ool.
E
1
i
+
._ __._.
-
-
..
-~
-
-. . .
:,
sec
Fig.
4
E olu ion
o
he lapa oscope ip posi ion du ing an
in e en ion,
a)
measu ed,
h)
il e ed
-
..
1,:
5.
The Robo ic
Handling
Sys em
The lapa oscope mo emen s mus be pe o med
h ough he oca , esul ing in he
cp,
y
and
p,
mo emen s
and main aining in a ian he o a ion
8,
o e he
lapa oscope axis. These mo emen s mus p o ide he
equi ed and
wAZ
displacemen s o he op ics
( he lapa oscope ip), wi h espec o he scene co-
o dina es sys em (wo ld ame).
To achie e he adequa e gene a ion o hese
mo emen s i has been belie ed mo e app opia e o place
he obo no jus holding he lapa oscope handle, bu
o
emo e he a m om he wo king zone.
A
s i link, ha
p oduces only a ansla ion e ec
on
he obo end
e ec o e e ence ame, has been ins aled in he obo
w is . This obo con igu a ion le s mo e ee space o he
su geon and his eam, a eal need in he su gical hea e .
To simpli y he gene a ion o he obo con ol o de s,
he s a egy o ollow could be o p o ide he obo
con ol uni wi h he inc emen s
‘AX,
RAY
and
RAZ
ied o
he obo Ca esian ame. These mo emen s o he obo
end
-
e ec o a e ansmi ed o he lapa oscope h ough
he added link ha is igidly as en o he obo ip. The
junc ion be ween his link and he lapa oscope
is
a
uni e sal join
R.
The h ee deg ees o eedom o his
join allows he ee mo emen o he lapa oscope a his
898
poin o i he cons ains imposed by he abdominal en e
poin , he oca . Wi h his con igu a ion, he inc emen al
mo emen s ‘AX, ‘AY and ‘AZ p oduce a he lapa oscope
ip, he op ics poin o iew,
a
ans o med wo king space
AV,
Ay
and
Ap
( ig.
5).
Consequen ly, an added con ol di icul y due o his
kynema ic chain is his wo kspace ans o ma ion.
The e o e, when he ision sys em de ec s an e o
posi ion
in
one axis di ec ion, o ins ance “AX, he
ision con ol closed loop, using he abo e men ioned
ans o ma ion, would p oduce an inc emen al mo emen
o he obo w is , ‘AX. In his case, he lapa oscope ip,
due o he oca cons ains would mo e a ajec o y
de e mined by wo coupled mo emen s‘Acp and “Ap, hus
modi ying bb h i s posi ion o e he
2D
image and also
he zoom. Since he sys em ope a es
in
closed loop, his
e o would be co ec ed by he succesi e mo emen s, bu
p oducing an undesi able ansi o y. To a oid his
esul ing je king i is equi ed o pe o m a coo dina es
ame ans o m, in such a way ha a “AX posi ion e o
measu ed by he ision sys em, p oduces a mo emen
RAX,
“AY and
‘AZ
so
as o ob ain a displacemen o he
lapa oscope ip o only one deg ee o eedoinWAX. This
Ca esian lapa oscope mo emen ( ig. 6), co esponds o
he ajec o y o he lapa oscope end-e ec o , bu no o
i s o ien a ion, which is o ced due o he oca
cons ains. The con ol o his o ien a ion would equi e
he addi ion o
wo
addi ional deg ees o eedom in he
lapa oscope ip, as p oposed
in
[IO].
The calcula ion o
his ame ans o m, o con ol he obo wi h decoupled
mo emen s, is possible, bu one o he a iables, he
posi ion o he oca wi h espec o he obo ame, is
no ixed du ing an in e en ion. On he o he hand, he
obo ex ension link, due
o
i s lig hness is no comple ely
igid and p oduces a lexion ha esul s in a ansla ion
and a o a ion o he e e ence ame
R’
( ig.
7)
ha is also
di icul o measu e. Fo hose easons, he calcula ions o
he di e en ames, equi ed o minimize he e ec s o
he coupled mo emen s, and he change o he gain o he
di e en join mo emen s, in acco dance wi h he
lapa oscope ip posi ion wi hin he scene, a e based on
some pa ame e s which a e dinamically e alua ed om
he esul o he con ol ac ions measu ed by
sys em i sel .
6
Sa e y
In su ge y he pa ien sa e y is an essen ial
he ision
issue, and
di e en sa e y aspec s ha e o be conside ed.
In
a i s
g oup we ha e conside ed all he sa e y aspec s ela ed o
he equi ed elec ical p o ec ions. The lack o an e icien
connec ion o an ins umen o g ound could p oduce a
ROBOT
ARM
R
-I
Fig.
5
Gyec o a obo Ca esian mo emen
on
he lapa oscope ip posi ion
ROBOT
ARM
Fig.
6
Robo mo emen necessa y
o
p oduce a
Ca esian ansla ion
o
he lapa oscope ip
ROBOT
ARM
Fig.
7
T ansla ion and o a ion o he R‘
ame due o he link lexibili y
Fa aday e ec wi h espec o o he elec ical ins umen s
used. On he o he hand i is necessa y o e i y he
e icien p o ec ion o he equipmen agains
EMI,
specially when using elec ical ins umen s.
A
second aspec conside ed has been ha ela ed
o
he possible physical damages, p oduced by undesi able
mo emen s. To !sol e his sa e y p oblem wo di e en
kind o complemen a y p o ec ions ha e been aken: a
passi e mechanical p o ec ion and an ac i e one.
899

The passi e p o ec ion consis s on he use o wo
sc ews o hold he ball-and socke join which ha e been
p e iously con enien ly weakened o o ce hem o b eak
in case o a lapa oscope collision wi h a pa ien o gan
du ing he su gical p ocedu e. This sc ew weakening has
been a ained using nylon sc ews wi h hei h eads
in e naly d illed,
so
as o p oduce hei b eaking when
hey suppo a o ce highe han 350 g m. This e o
alue su passes he lapa oscope
-
oca ic ion o ces
wi hou p oducing damages o he pa ien .
On he o he hand, and wi h he aim o a oid his kind
o b eaking du ing an in e en ion, ha would cause an
in e up ion o he su gical p ocedu e in o de o eplace
he lapa oscope holding de ice, an addi ional ac i e
p o ec ion sys em is used. This p o ec ion is based on he
use o o que senso s, gauges, placed on he obo
-
lapa oscope junc ions link. The de ec ion o o e e o s
gene a es p o ec i e eac i e mo emen s ad essed o he
gua an y he pa ien in eg i y.
Fu he mo e, and ying o a oid undesi able eac i e
ealising mo emen s o he lapa oscope, i is necessa y o
assu e a clea disposi ion o he cables, ideo and ibe
op ics, lea ing he lapa oscope ha can p oduce
o e e o s due o ic ion o o ques ha could gene a e
undesi able con ol eac ions.
7
Resul s
The de elopmen o his p ojec has ollowed
wo
successi e phases. In a i s phase we ha e de eloped and
se up he ision sys em which iden i ies and acks wi h
high eliabili y he su geon ools. In his phase a speci ic
image p ocessing ha dwa e has been de eloped o ob ain
he edges and o each a sampling ime sho enough o
implemen a no syncopa ed con ol o he obo ic a m.
A e he de elopmen o he isual acking sys em
and closing he loop wi h he obo , he nex s ep has been
o
es ablish he con ol c i e ia acco ding o he su geons
needs and p e e ences. These p e e ences a e no always
exac ly he same o all he su geons, his ac has o ced
us
o design he sys em
so
as o be easily adap able o
e e y one o hem. This pe sonalisa ion consis s basically
on he a ailabili y o selec he desi ed scene size (zoom)
and he speed
-
s abilisa ion ac o in he acking o he
scene in e es poin .
To es ablish hese pa ame e s some expe imen a ion
has been done wo king wi h chickens un il he sys em
beha iou has been conside ed
as
e y sa is ac o y by he
su geons o ou wo king eam. F om his esul s we ha e
s a ed o wo k in he expe imen al ins alla ion o he
su gical hea e in he Cen e Qui u gic Ad ia o s a in
b ie wi h clinical ials.
Acknowledges
We would like o acknowledge o Xa ie Valls o his
con ibu ion in he implemen a ion and se up o he
sys em.
This wo k is unded by he CIRIT, he Ca alan
Resea ch Agency.
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