Article pp.92-95 du Vol.17 n°2 (1987)

(1)

La v i d 6 o - e n d o s c o p i e a u f u t u r

C. S E C R O U N

L E R L Universitd de Reims (France)

Future methods of endoscopy

D E L ' E N D O S C O P E A U V I D E O - E N D O S C O P E L ' 6 v o l u t i o n technique qui consiste ~t remplacer le classique endoscope ~ fibres optiques p a r le vid6o- endoscope ne semble gu~re f o n d a m e n t a l e , un cofit nettement plus 61ev6 p o u r deux avantages limit6s :

un plus grand c o n f o r t du m6decin ;

- - une possibilit6 int6ressante de stocker les images

(1).

P o u r t a n t , le vid6o-endoscope contient en germe une v6ritable r6volution : l'utilisation d ' u n e cam6ra C C D a p p o r t e un certain h o m b r e de caract6ristiques telles que :

un r e n d e m e n t ~lev6 ;

un spectre tr~s large allant des UV (300 nm) aux IR (1 000 nm) ;

une d y n a m i q u e excellente ;

- - une b o n n e lin6arit6 ;

et surtout, l ' o b t e n t i o n d ' u n e image 6chantillonn6e, donc susceptible d ' e t r e << informatis6e , .

L A V I S I O N ASSISTF.E P A R O R D I N A TEUR ( V . A . O . )

L ' i m a g e est un signal bidimensionnel vecteur d ' u n e grande quantit6 d ' i n f o r m a t i o n . Ce signal peut ~tre capt6 par l'oeil - - mais seulement dans la limite du spectre visible - - et trait6 et interpr6t6 par le cerveau h u m a i n ; ceci ~ des vitesses 6tonnantes c o m p t e tenu de la richesse de l ' i n f o r m a t i o n d ' u n e image et de la lenteur de la plupart des traitements humains. Nous avons l~t les deux sources de l'int6r~t de la vision par o r d i n a t e u r : l'existence d ' u n signal tr6s riche en information et la possibilit6 d ' u n traitement rapide dont le r6sultat peut 8tre facilement c o m m u n i q u 6 h l'op6ra- teur humain.

Le f o n c t i o n n e m e n t d ' u n syst6me de V . A . O . peut

&re illustr6 p a r la figure 1.

Dans sa f o r m e actuelle, le vid6o-endoscope r6alise les trois premi6res 6tapes : 6chantillonnage-codage- restauration, m~me si toutes les possibilit6s offertes

p a r la technique ne sont pas prises en c o m p t e ~t ce der-

nier niveau. Les deux 6tapes sup6rieures sont actuelle- ment r6alis6es p a r le m6decin.

Fig. 1

D U VIDFSO-ENDOSCOPE A L "<~ I N F O - E N D O S C O P E ,

Deux points de vue peuvent justifier l'intervention de l ' i n f o r m a t i q u e sur l'image endoscopique 9

- - un point de vue h u m a i n , afin d'assister le sp6cia-

liste dans sa t~che ;

- - u n point de vue technique, afin d ' e x t r a i r e de l'image un m a x i m u m d ' i n f o r m a t i o n s .

L "aide au diagnostic

l~tablir u n diagnostic sur la base d ' u n e i m a g e endoscopique est, en dehors des cas typiques, une op6ration p u r e m e n t subjective. L a reconnaissance d ' u n e anomalie n ' e s t possible que par r a p p o r t ~t un mod61e que le sp6cialiste s'est cr66 plus ou moins consciemment au cours de son exp6rience profession- nelle. Cette situation est bien illustr6e par la figure 2.

Le principal p r o b l 6 m e pos6 p a r cette subjectivit6 ^{e s t} 1i6 au fait que le mod61e est d6termin6 p a r l ' e x p 6 r i e n e e

du sp6cialiste. II est d o n c diff6rent d ' u n expert l'autre, et de plus 6volue dans le temps.

L ' a p p o r t de l ' i n f o r m a t i q u e dans cette o p t i q u e peut

&re f o n d a m e n t a l . P a r l'6tude syst6matique d ' u n certain n o m b r e de caract6ristiques choisies et quantifia- bles teUes que la couleur, le contraste, la f o r m e , la texture, etc., il devient possible de d6finir un mod61e

Tir6s h part: C. SECROUN, LER1, Universit6 de Reims (France).

92 V o l u m e 1 7 - N ~ 2 - 1 9 8 7 A c t a E n d o s c o p i c a

Cet article des Editions Lavoisier est disponible en acces libre et gratuit sur archives-acen.revuesonline.com

(2)

Fig. 3

Fig. 2

La plupart des observateurs ne voient clans cette image que des t~ches noires et blanches distribu6es au hasard. Si nous pr6cisons que cette vue repr6sente un Dalmatien, alors chacun d6couvre sans d i f f i c u l t 6 le chien au centre de I'image. Nous avons appliqu6 un mod61e ,~ id6al ,, celui du Dalmatien, ~ I'interpr6tation de I'image.

objectif, et p a r cons6quent, de reconna~tre a u t o m a t i - q u e m e n t une f o r m e p a t h o l o g i q u e .

R e m a r q u e 9 la r e c o n n a i s s a n c e a u t o m a t i q u e d ' u n e f o r m e p a t h o l o g i q u e ne p e u t en aucun cas constituer un diagnostic d6finitif. Le sp6cialiste reste le seul ~t p o u v o i r d6cider si l ' a s p e c t d6tect6 dolt faire l ' o b j e t d ' u n e a t t e n t i o n particuli6re. D a n s tous les cas, la m a c h i n e doit rester un outil d'aide au diagnostic, une assistance technique.

L " avenir technique

N o t r e o b j e c t i f est d ' 6 v o q u e r les possibilit6s offertes. N o u s d e v o n s d i s t i n g u e r d e u x t y p e s de trai- t e m e n t s :

- - ceux r6alisables en t e m p s r6el, sans a u g m e n t a - tion de la dur6e de l ' e x a m e n m6dical, celui-ci n ' 6 t a n t pas des plus agr6ables p o u r le patient ;

- - ceux r6alisables en t e m p s diff6r6, sur les images enregistr6es et stock6es au cours de l ' e x a m e n .

T e m p s r6el : la premi+re possibilit6, et la plus sim- ple, c o n s i s t e / l signaler au praticien la z o n e r e c o n n u e a u t o m a t i q u e m e n t c o m m e susceptible d ' e t r e p a t h o l o - gique. Cela p e u t consister, en pratique, ~t s u p e r p o s e r ~t l ' i m a g e r6elle un c o n t o u r de la zone d6tect6e, a c c o m - pagn6 ou n o n d ' u n signal sonore, afin d ' a l e r t e r le m6decin.

D a n s la v e r s i o n pr6sente, le v i d 6 o - e n d o s c o p e trans- m e t une i m a g e e n lumi+re visible. L ' e x t e n s i o n du

spectre en fr6quences peut faire appara~tre une n o u - velle i n f o r m a t i o n (nous a v o n s vu que les cellules C C D sont sensibles de 300 ~ 1 000 nm) (figure 3). Le p r o - blame n ' e s t d ' a i l l e u r s pas i n f o r m a t i q u e mais pure- m e n t p h y s i q u e : il suffit d'6clairer la sc6ne avec un faisceau l u m i n e u x ~t la b o n n e longueur d ' o n d e s . De m~me, o n p e u t envisager de travailler n o n p a s en r6flexion (6clairage externe) mais en 6mission, d a n s le d o m a i n e i n f r a r o u g e . L a t h e r m o g r a p h i e a l a r g e m e n t d 6 m o n t r 6 ses p o s s i b i l i t 6 s d a n s le d i a g n o s t i c du cancer (2).

T e m p s diff~r~ : c'est sans a u c u n d o u t e dans ce d o m a i n e que les perspectives sont les plus vastes : nous ne s o m m e s plus tributaires de la dur6e de l ' e x a - m e n , et les possibilit6s de t r a i t e m e n t sont larges.

Citons s i m p l e m e n t quelques-unes d ' e n t r e elles : - - m e s u r e de d i m e n s i o n s ;

- - 6tude du relief ;

-- t r a n s f o r m a t i o n s de l ' i m a g e ;

-- a g r a n d i s s e m e n t ;

- - c o m p a r a i s o n avec des images enregistr6es pr6c6- d e m m e n t : 6tude de l ' 6 v o l u t i o n d ' u n e t u m e u r d a n s le t e m p s ;

- - etc.

E T L " E N S E I G N E M E N T ?

L a possibilit6 d ' e n r e g i s t r e r d'excellentes i m a g e s c o n d u i t i n 6 v i t a b l e m e n t h penser ~ leur utilisation en f o r m a t i o n . Les capacit6s actuelles de s t o c k a g e (je pense en particulier au disque o p t i q u e num6rique) p e r m e t t e n t n o n seulement d ' e n v i s a g e r des b a n q u e s d ' i m a g e s tr~s vastes, g6r6es ~t l'aide d ' u n m i c r o - o r d i - n a t e u r , m a i s s u r t o u t la mise au point d ' u n syst~me a c t i f de s i m u l a t i o n d ' u n e x a m e n e n d o s c o p i q u e .

I1 s ' a g i t alors, en f o r m a t i o n , de r e m p l a c e r le p a t i e n t p a r un o r d i n a t e u r . L ' 6 t u d i a n t m a n i p u l e l ' e n d o s c o p e en r6el et l ' i m a g e sur l ' 6 c r a n simule la r6alit6. U n tel syst~me est r6alisable. C ' e s t un puissant outil de f o r - m a t i o n .

RI~FI~RENCES

1. R E Y J.-F. ~ P l a c e de la vid6o-endoscopie 61ectronique en e n d o s c o p i e d i g e s t i v e . A c t a E n d o s c o p i c a , 1986.

C R E G G / S M I E R / I m a g e et c o m m u n i c a t i o n .

2. F O R N A G E B. - - L a t h e r m o v i s i o n : m 6 t h o d e de d i a g n o s t i c et de surveillance chez des patientes atteintes de cancer d u sein. Th~se d e D o c t o r a t en m~decine, 1974, Reims.

A c t a E n d o s c o p i c a V o l u m e 17 N ~ 2 - 1987 93

(3)

F R O M T H E E N D O S C O P E T O T H E V I D E O E N D O S C O P E

Technological progress which seeks to replace con- ventional fiberoptic endoscopy by the video endos- cope does not appear to represent basic progress, because o f the markedly higher cost o f this device to obtain two limited advantages :

- - greater facility f o r the physician ;

- - the interesting possibility o f storing pictures [1].

Yet, the video endoscope contains the spark o f a truly revolutionary advance : use o f a CDC camera provides a certain number o f elements such as :

- - high yield ;

- - a very wide spectrum, f r o m U V (300 nm) to I R (1 000 nm) light ;

- - excellent dynamics ; - - good linear display ;

and especialy, a picture composed o f samples, and thus which may be computerized.

F R O M T H E V I D E O E N D O S C O P E T O T H E " C O M P U - E N D O S C O P E "

Two viewpo&ts may justify the appfication o f com- puterization to endoscopic imaging :

- - f r o m the human p o i n t o f view, to assist the medical specialist in his task ;

- - f r o m the technical p o i n t o f view, to extract the maximum amount o f information f r o m the image.

As an aid to diagnosis :

To establish a diagnosis on the basis o f a n endosco- pic image is, with the exception o f certain typical cases, a strictly subjective procedure. Recognition o f a given anomaly is only possible with reference to an ideal model which the endoscopist has created f o r himself consciously by his professional experience with endoscopy. This fact is well illustrated by fi- gure 2.

C O M P U T E R - A S S I S T E D I M A G I N G ( C A I )

A n image is a two-dimensional vector with a large amount o f information. This signal may be captured by the human eye but only within the spectrum o f visi- ble light and processed and interpreted by the brain, this whole process occurring at phenomenal speed considering the detailed information in a picture and the slowness o f most human processes. We have here both sources o f interest o f computer assisted ima- ging : presence o f a signal with detailed information and the capacity f o r rapid processing and whose result may be easily conveyed to the computer operator.

In its current f o r m the video endoscope produces the first three steps : sampling - coding - ifnage resto- ration, even i f all o f the technical possibilities availa- ble are not taken into account at the last level. The last t w o steps currently are p e r f o r m e d by the physician.

94

Figure 1

V o l u m e 1 7 - N ~ 2 - 1 9 8 7

Figure 2

In this picture, most observers see only black and white randomly distributed spots. If it is made known that this image represents a dalmatian, then everyone who looks will discover a dog in the center of the picture without difficulty. We have applied an "ideal" model,

that of the dalmatian, to interpretation of the picture.

The main problem posed by this subjective view is related to the fact that the model is determined by the endoscopist's experience. It thus differs f r o m one spe- cialist to another, and changes over time.

The contribution o f computerization in this field may thus be vital. By systematically examining a cer- tain number o f predetermined measurable characte- ristics such as color, contrast, f o r m , texture, etc. It becomes possible to define an objective model conse- quently to automatically recognize a pathological configuration.

N.B. The automatic recognition o f a pathological configuration cannot under any circumstances consti- tute a definitive diagnosis. The specialist alone has the capacity to decide whether the particular aspect detec- ted should receive particular attention. In all cases, the instrument must remain a tool to assist in diagno- sis, a technical aid.

A c t a E n d o s c o p i c a

(4)

F u t u r e technical d e v e l o p m e n t :

Our aim is to draw attention to the possibilities offered by this technique. We can distinguish two types o f processing :

- - those which m a y be accomplished in real time, without any increase in the length o f the medical exa- mination with the endoscope, which is never very pleasant f o r the p a t i e n t ;

-- those which m a y be p e r f o r m e d later, with ima- ges recorded a n d s t o r e d during the examination.

Real time : the f i r s t a n d simplest possibility consists in calling to the p h y s i c i a n ' s attention the site automa- tically recognized as possibly pathological. In prac- tice, this m a y consist in superimposing the outline o f the area detected on the real image, with or without an audio signal, to alert the physician.

In the present version o f this system, the video endoscope transmits an image with visible light.

Extension o f the spectrum with different frequencies m a y t:eveal n e w i n f o r m a t i o n (we saw that C.D.C. cells are sensitive f r o m 300 to 1 000 nm) (fig. 3). M o r e o - ver, the p r o b l e m is n o t with computerization but rather is strictly p h y s i c a l : it is sufficient to illuminate the f i e l d with a light source at the correct wave length.

In the same way, it is possible to operate not by reflec- ted light (external illumination) b u t with emitted light, in the infrared range. Thermography has extensively d e m o n s t r a t e d its p o t e n t i a l in the d i a g n o s i s o f cancer [2].

A t a later time : m o s t certainly, it is in this area that there are the greatest prospects : here we no longer need worry a b o u t the length o f the procedure, a n d possible types o f processing are extensive.

L e t us m e n t i o n a f e w o f them : - - measuring various dimensions ;

Figure 3

-- studying the contours o f the image ;

-- transforming the image ;

-- enlargement o f the image ;

- - comparison with previously recorded images to assess t u m o r growth over time ;

- - etc.

A N D M E D I C A L E D U C A T I O N ?

The ability to r e c o r d excellent p i c t u r e s leads directly to their use to train f u t u r e practitioners. Cur- rent storage techniques (for example the digital optic disc) m a k e it possible n o t only to forsee e n o r m o u s image banks, overseen by a microcomputer, but also d e v e l o p m e n t o f an interacting system to simulate an endoscopic examination.

Thus, it becomes a question o f replacing the patient by a c o m p u t e r to train f u t u r e endoscopists. The f u t u r e specialist maneuvers the endoscope in real time a n d the picture displayed on the video screen simula- tes reality. Such a system is possible. It w o u l d be a p o t e n t instrument to train endoscopists.

Acta Endoscopica Volume 17 N ~ 2 - 1987 95