Preliminary Design of Bilio-digestive Anastomosis by Magnetic

Compression

elanie Courtaudi

ere

, Nicolas Andreff

and St

ephane Koch

ISIFC, Universit

e de Franche-Comt

e, Besanc¸on, France

Femto ST Institute, UFC/CNRS/ENSMM/UTBM, Besanc¸on, France

CHU J. Minjoz, Besanc¸on, France

Keywords:

Magnetic Compression, Bile Duct, Duodenum, Ferroﬂuid, Obstruction, Jaundice.

Abstract:

Some experiments have been realized to determine the characteristics of magnets allowing for bilio-digestive

anastomosis by magnetic compression using a ferromagnetic gel and a magnet. The attraction distance be-

tween the ferromagnetic gel and the magnet was determined experimentally, under several conﬁgurations:

magnet shape, strength, number and arrangements. Two magnets with a strength of 14,000 Gauss and a di-

ameter of 12.7mm were necessary to attract 0.353mL of ferroﬂuid contained in a plastic sheath placed at 1cm

of the magnet. So the magnet is able to attract the ferroﬂuid. However, this procedure needs a large powerful

magnet which is not compatible for an immediate use in the human body. Nevertheless, this preliminary result

opens promising investigation paths.

1 INTRODUCTION

Currently two treatments are available to treat a bil-

iary obstruction (Figure 1). The ﬁrst one is a non-

invasive treatment: the ERCP (endoscopic retrograde

cholangio pancreatography) using a duodenoscope

and a guide wire through the obstruction allows to in-

sert a biliary stent and thus to treat the obstruction

However if the guide wire can’t be inserted through

the tumor, the biliary stent cannot be placed and a

cholangitis occurs and kills the patient. The second

method is the invasive surgery to skirt the obstruc-

tion. For instance, duct-to-duct anastomosis by in-

Figure 1: Anatomic diagram of the gallbladder and the duo-

denum.

vasive surgery are performed. As a promising al-

ternative to surgery, anastomosis by magnetic com-

pression is currently practiced for intestinal anasto-

mosis (Cope, 1995; Myers et al., 2010; Uygun et al.,

2012; Pichakron et al., 2011; Gonzales et al., 2012;

Mimuro et al., 2003; Itoi et al., 2010). However, the

reported magnetic duct-to-duct compressions seem to

require surgical insertion of the magnet placed up-

stream the obstruction (and may be also a surgical re-

moval) (Fan et al., 2011).

To avoid invasive surgery, the creation of an

anastomosis by magnetic compression between the

blocked bile duct and the duodenum could be the so-

lution. However, the question of inserting a magnet in

the bile duct upstream the obstruction without surgery

is left unanswered yet.

Our proposal is to investigate the injection of a

biocompatible ferromagnetic gel in the biliary duct

and then study its attraction by the magnet placed in

the duodenum.

2 METHOD

2.1 A Novel Clinical Procedure

More precisely, the novel clinical protocol we foresee

218

Courtaudière M., Andreff N. and Koch S..

Preliminary Design of Bilio-digestive Anastomosis by Magnetic Compression.

DOI: 10.5220/0004903902180223

In Proceedings of the International Conference on Biomedical Electronics and Devices (BIODEVICES-2014), pages 218-223

ISBN: 978-989-758-013-0

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

Figure 2: Anatomic diagram of the biliary duct and the duo-

denum + obstruction and considered treatment.

consists of the injection under EUS (endosonography)

of a biocompatible ferromagnetic gel by a FN with

a diameter of 0.9mm (19G) above the obstruction of

the bile duct. It thus will stay there until anastomo-

sis is done and will be removed or eliminated by the

new natural channel. Then a magnet would be placed

in the duodenum with a video endoscope. Removal

of the magnet and gel would occur by simple natural

elimination in the feces.

2.2 Anatomical Constraints

Before this protocol can be tested, the choice of ma-

terials must be tested in accordance to the anatomi-

cal constraints. Ideally, the magnet would be placed

through the operator channel, thus limiting the diam-

eter of the magnet to some 4.2 mm. Nevertheless, us-

ing a magnet with a somewhat larger diameter could

be enabled by holding over the scope with a nylon

wire.

The common bile duct has an internal diameter

included between 3mm and 8 mm in normal state

(>10mm after cholecystectomy or in case of obstruc-

tion). The volume of ferromagnetic gel that needs to

be considered must cope with the bile duct lumen.

The bile duct measures about 10cm (hepatic duct

and common duct) and the anastomosis can be located

only in front of the ﬁrst duodenum. So the distance

between the gel and the duodenum magnet will be less

than 1cm. Therefore, we need to determine the attrac-

tion strength of the magnets which are necessary to

the attraction of a ferromagnetic gel localized at 1cm.

This is coherent with all the published studies,

where the magnets were placed very close from one to

another, with a maximal attraction distance between

the magnets lower than 20mm. Moreover, the diame-

ter of the different magnets varied between 2mm and

5mm. However, this does not tell much on how this

would extend to bilio-digestive anastomosis. Indeed,

replacing one magnet by ferromagnetic gel in order to

avoid a surgical insertion in the bile duct completely

changes the magnetic characteristics of the set-up.

The use of two kinds of magnets is reported:

• magnets in Samarium-Cobalt;

• magnets in Neodymium-Iron-Bore.

Both kinds are rare-earth magnets, identical in

term of magnetic ﬂow density. Each of them is ap-

propriated for the anastomosis by magnetic compres-

sion but the obstructive strength of the magnets in

Samarium-Cobalt is higher and so better. The mag-

nets used in previous studies had a strength included

between 3000 Gauss (≈0.3 Tesla) and 3700 Gauss

(≈0.37 Tesla). Furthermore, to ensure their biocom-

patibility, many covering materials can be used, such

as chromium, titanium nitride or polycarbonate. Dif-

ferent magnets shapes were used: spherical, cylindri-

cal and ring-shaped. The spherical magnets show a

smooth and round surface, thus they can move and

roll up.

2.3 Experimental Set-up and Method

The experiments that were set-up consists of the

use of off-the-shelf ferroﬂuid and magnets in vari-

ous shapes, strengths and conﬁgurations. A ferroﬂuid

is a colloidal solution of ferromagnetic nanoparti-

cles, having a size of 10nm, put in solution in a

solvent or in water. The liquid becomes magnetic

when an external magnetic ﬁeld is applied. However,

it keeps its colloidal stability. The ferroﬂuids have

the strange property that, when the magnetic ﬁeld is

strong enough, the ferroﬂuid topology changes and

weakly rigid peaks appear on the surface. Ferroﬂu-

ids are, most frequently, composed of nanoparticles of

magnetite (Fe3O4) or of magnesite (γ-Fe2O3), which

are both iron oxide. Ferroﬂuids have an application in

many ﬁelds especially in medicine and biology (test-

ing of biological groups, contrast substance, cancerol-

ogy, to name a few).

The magnets used (Figure 3) were made in

neodymium iron bore and had the characteristics

given in Table 1, determined thanks to the state of art.

The magnets were placed in 3 different conﬁgu-

rations: horizontal (Figure 4), vertical (Figure 5) and

Sphere 1 Sphere 2 Cylinder 1

Figure 3: The different magnets used in the experiments.

PreliminaryDesignofBilio-digestiveAnastomosisbyMagneticCompression

219

Table 1: Characteristics of the different magnets used in the

experiments.

Magnet Diameter Afterglow Magnetization

(mm) (Gauss)

Sphere 1 12.7 14,000 N42

Sphere 2 8 12,400 N38

Cylinder 1 5 13,500 N45

Figure 4: The 3 magnets in horizontal conﬁguration.

“loop” when it was possible (Figure 6).

The magnets were used alone, by two or by three.

Their simultaneous utilization was always made with

magnets which had the same characteristics (there

was no mix between the different types of magnets).

To measure the necessary distance for the attrac-

tion between the ferroﬂuid and the magnet, the fol-

lowing assembly was realized thanks to a gauge (Fig-

ure 7). The gauge has a magnetic ﬁxation system so

the magnet(s) were simply ﬁxed by magnetization.

To represent the bile duct of the patient it was nec-

essary to use a material which had the same charac-

teristics as the human body. A plastic sheath (Fig-

ure 8) possessed the matching properties. The ferro-

magnetic liquid was inserted with a syringe B-D Plas-

tipak (capacity of 1mL) and a needle with a diameter

of 0.45mm. The plastic sheath had a diameter of 3mm

and a length of 5cm. The quantity of ferroﬂuid in-

serted was:

V = πr

h = π ∗ 0.15cm

∗ 5cm = 0.353mL (1)

The needle was made of stainless steel which was

not magnetic so there was not interaction with the fer-

roﬂuid.

Figure 5: The 3 magnets in vertical conﬁguration.

Figure 6: The 3 magnets in the “loop” conﬁguration.

The experimental protocol was to place the sheath

on the gauge base with the magnets far enough from

it. Then, the magnets were slowly descended until

the sheath was lifted up in the air by the magnetic

attraction.

The acquisition of the movement was made by a

camera Mikrotron EoSens 4 CXP with a 25mm Com-

putar objective. When the acquisition was ﬁnished,

the attraction distance could be calculated. It cor-

responded at the distance between the base and the

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220

Figure 7: Experimental set-up.

end of the plastic sheath, once it had been attracted

by the magnet. The distance was directly legible on

the screen thanks to the graduation of the gauge (Fig-

ure 9).

To increase the reliability of the measures, each

were realized 5 times, then the mean of the results

was calculated.

3 RESULTS

The results are assembled in Table 2.

For a single spherical magnet, the horizontal and

the vertical measure with one magnet is the same, so it

appears only once in the table. The measures with the

cylindrical magnets have been realized on the “short

side” (Figure 10). The difference of attraction be-

tween the horizontal and the vertical position for the

same number of magnets was very low.

With the “loop” conﬁguration the attraction dis-

tance decreased by 50%. This conﬁguration was not

efﬁcient, so it will be important to avoid this position-

ing for the magnets when they will be inserted in the

human body. For the same type of magnet, the attrac-

Figure 8: Plastic sheath of 3mm ﬁlled with ferroﬂuid.

Figure 9: Result of an acquisition.

Table 2: The results of the experiments with the 3 magnets.

Conﬁgurations Number of

magnets

Attraction

distance

(cm)

Spherical 1 (diameter 12,7mm)

Horizontal 1 magnet 0,98

2 magnets 0,98

3 magnets 1,08

Vertical 2 magnets 1,04

3 magnets 1

“loop” 3 magnets 0,56

Spherical 2 (diameter 8 mm)

Horizontal 1 magnet 0,64

2 magnets 0,44

3 magnets 0,6

Vertical 2 magnets 0,6

3 magnets 0,58

“loop” 3 magnets 0,28

Cylindrical 1 (diameter 5mm)

Horizontal 1 magnet 0,36

2 magnets 0,46

3 magnets 0,48

Vertical 2 magnets 0,44

3 magnets 0,46

tion distance ﬂuctuated in function of the number of

magnets, sometimes the attraction distance is higher

with 2 magnets than with 3. This ﬂuctuation was

caused by the positioning of the magnets one over the

other. Indeed the magnetization between them could

be in different directions, thus it inﬂuenced the total

properties of the magnet. These results showed the

variability of the attraction as a function of the posi-

tioning of the magnets. When they will be inserted

in the body it will be necessary to take care of their

orientation. The utilization of several magnets in-

creased the attraction distance. This increasing stays

low. Moreover for the patient, the utilization of many

magnets is not recommended for safety reasons (e.g.

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221

Figure 10: The two possible positions for the cylindrical

magnets.

Figure 11: The future conﬁguration.

undesired magnetic compression in the small bowel),

unless a speciﬁc device allows to keep them together.

4 DISCUSSION

The bile duct and the duodenum are separated by a

distance of 1cm, so an attraction distance higher or

equal is necessary. However, the weight of the sheath

was measured to 1g, which means that the attraction

force is only 10mN at 1cm distance. This might not be

enough for starting the compression. Moreover, only

the utilization of many spherical magnets with a di-

ameter of 12.7mm and an afterglow of 14,000 Gauss

(≈1.4 Tesla) allows to achieve this value. The diame-

ter of such a magnet is not perfectly adapted for being

used in the body because it is both heavy and yet still

small enough to pass into the small bowel. The mi-

gration of this magnet should be avoided.

The alternative we will study now it the use of a set

of weaker magnets (Figure 11), attached together onto

a muco-adhesive patch, in order to increase both the

biocompatibility and efﬁciency of the device. Indeed,

this patch would cover a larger surface and hence the

set of magnets is expected to yield a stronger attrac-

tion force than a single one. Moreover, such a patch

is expected to have a stronger adhesion to the mu-

cosa and to less encumber the duodenum than a single

spherical magnet.

The patch would be inserted in the duodenum

thanks to the operator channel of the endoscope, then

it would be placed on the duodenum wall thanks to a

self-expandable fully covered metallic stent. To avoid

the attraction of the magnets when the patch is in the

operator canal and to allow its extension, the magnets

should be oriented in the same direction of polarity

(all the north faces are on the same side). To permit

the adhesion of the patch on the duodenum wall, the

patch could be covered with a muco-adhesive ﬁlm.

Finally, the ferroﬂuid could be replaced by a

magneto-rheologic ﬂuid. Such ﬂuids are made of

lager ferromagnetic particles and thus have better

magnetic properties. They are considered to have

the drawback of sedimenting, contrary to ferroﬂuids

where nanoparticles stay apart. Nevertheless, this

might not necessarily be a concern in our case, if

properly handled, because it would improve the re-

moval of all magnetic material from the body at the

end of the treatment.

ACKNOWLEDGEMENTS

This work was partly supported by the French ANR

Labex ACTION (contract ”ANR-11-LABX-01-01”).

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