![](bg5.png)
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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