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What is a programmable shunt?

Posted Dec 15 2011 7:09am


After joining a new site on facebookI had some new friends ask if anyone had ever heard of a shunt that programmed with a magnet? My first response was... HUH?? Then I read some of the comments! This is a group for spina bifida and hydrocephalus Women.
Several had never heard of programmable shunts. One made a comment it sounded like Star Trek. I Now see that I need to get my act together and get back to my job at blogging.
This is information on codmen hikim which has been having a lot of complications with their shunts lately and I don't recomend for any one. It was the one I had to live with for 14 moths that was faulty. But This explains how they work pretty well.
I don't have a problem with Codmen I just want them to fix this constant problem with this shunt.
There are several other programmables also you can find on my blog one is the Medtrinic.



Magnetically programmable shunt valve: MRI at 3-Tesla
Frank G. Shellocka,b,4, Stephen F. Wilsonc, Chrospinal fluid. istophe P. Maugec
aKeck School of Medicine, University of Southern California, Los Angeles, CA, USA
bInstitute for Magnetic Resonance Safety, Education, and Research, Los Angeles, CA 90045, USA
cResearch and Development, Codman, a Johnson & Johnson Company, Raynham, MA 02767, USA
Received 25 September 2006; revised 6 December 2006; accepted 7 December 2006
Abstract

A magnetically programmable cerebrospinal fluid (CSF) shunt valve (Codman Hakim Programmable Valve, Codman, a Johnson &
Johnson Company, Raynham, MA) was assessed for magnetic field interactions, heating, artifacts and functional changes at 3-Tesla. The
programmable valve showed minor magnetic field interactions and heating (+0.48C). Artifacts were relatively large in relation to the size and
shape of this implant and, as such, may create a problem if the area of interest is in proximity to this implant. While multiple exposures and
various magnetic resonance imaging (MRI) conditions at 3-Tesla changed the settings of some valves (i.e., reprogramming was needed), the
function of the programmable valve was not permanently affected. Therefore, this magnetically programmable CSF shunt valve is acceptable
for a patient undergoing MRI at 3-Tesla or less when specific safety guidelines are followed, including resetting the valve, as needed.

D 2007 Elsevier Inc. All rights reserved.
Keywords: Magnetic resonance imaging; Safety; MRI; Implants; Specific absorption rate; Artifacts; Hydrocephalus; CSF; Programmable valve
1. Introduction
A hydrocephalus shunt valve is an implantable device
that provides constant intraventricular pressure and drainage
of the cerebrospinal fluid (CSF) for the management of
hydrocephalus and other conditions of impaired CSF flow
and absorption. Programmable shunt valves allow
surgeons to noninvasively optimize the opening pressure of
a shunt system before and after implantation, permitting the
implementation of specialized treatment regimes.
Programmable valves are typically adjusted using an
externally applied programmer tool to magnetically couple
to the adjustable components of these devices.
Accordingly, exposure to powerful magnetic fields can
cause inadvertent changes in valve settings or permanently
damage CSF shunt valves. With regard to magnetic
resonance imaging (MRI), various other issues exist for
programmable valves, including the possibility of movement
of the implant, extreme heating and the impact of
substantial artifacts.

The increasing clinical use of 3-T scanners necessitates the
evaluation of implanted devices at this higher field strength.
Therefore, the objective of this investigation
was to assess magnetic field interactions, heating, artifacts
and functional changes for a commonly used [1] programmable
valve (Codman Hakim Programmable Valve, Codman,
a Johnson & Johnson Company, Raynham, MA) in
relation to the use of a 3-T MR system.
2. Materials and methods
2.1. Programmable valve
The programmable valve (Codman Hakim Programmable
Valve, Codman, a Johnson & Johnson Company) is an
implantable device that provides constant intraventricular
pressure and drainage of CSF for the management of
hydrocephalus and other conditions in which CSF flow and
absorption are impaired. Intraventricular pressure
is controlled by a bball and coneQ valve that is under
the control of a calibrated flat spring and can be noninvasively
adjusted with the use of an external programmer
with a magnetic mechanism. Hard magnets fixed within the
base of a moveable cam react to the presence of the
magnetic field by rotating the cam to achieve equilibrium.
The adjustable valve accommodates 18 valve settings from
30 to 200 mm H2O in 10-mm H2O increments. Metallic
0730-725X/$ – see front matter D 2007 Elsevier Inc. All rights reserved.
doi:10.1016/j.mri.2006.12.004
4 Corresponding author. Institute for Magnetic Resonance Safety,
Education, and Research, Los Angeles, CA 90045, USA. Tel.: +1 310
670 7095; fax: +1 310 417 8639.
E-mail address: frank.shellock@gte.net (F.G. Shellock).
Magnetic Resonance Imaging 25 (2007) 1116– 1121
materials for the programmable CSF valve include 316L
stainless steel, Vacoperm (Ni–Fe), Vacomax (Sm–Co) and
unalloyed titanium.
2.2. MR system
A 3-T (Excite, Software G3.0-052B, General Electric
Medical Systems, Milwaukee, WI) active-shielded, horizontal
field scanner was utilized for all tests conducted on
the programmable valve.
2.3. Magnetic field interactions
Magnetic field interactions were determined for the
programmable valve in association with the 3-T MR system.
2.3.1. Translational attraction
Translational attraction was assessed for the programmable
valve using the deflection angle technique [12,17–19].
The programmable valve was attached to a test fixture to
measure the deflection angle. The test fixture has a
protractor mounted to the top of the structure and included
a bubble level to ensure proper orientation in the scanner.
Measurements were obtained at the position in the 3-T MR
system that produced the greatest magnetically induced
deflection angle. This point was determined
using gauss line plots, magnetic field measurements and
visual inspection to identify the location of the highest
spatial gradient. The highest spatial gradient for the 3-T MR
system occurs at a position that is 74 cm from the isocenter
of the scanner [12,19]. The magnetic spatial gradient at this
position is 720 G/cm. The deflection angle from the vertical
direction to the nearest 18 was measured three times, and an
average value was calculated.
. Torque
Magnetic-field-induced torque was assessed qualitatively
for the programmable valve using previously described
methodology. This procedure utilized a flat plastic
material with a millimeter grid. The programmable valve
was placed on this test platform in an orientation that was
458 relative to the direction of the static magnetic field of the
3-T MR system. The test apparatus with the programmable
valve was then positioned in the center of the scanner, where
the effect of torque is the greatest (based on the known
characteristics for the 3-T MR system), and observed for
alignment or rotation . The programmable valve was
then moved 458 relative to its previous position and again
observed for alignment or rotation. This procedure was
repeated to encompass a 3608 rotation of positions for the
programmable valve in the scanner. A qualitative scale was
applied to the results to characterize torque: 0, no
torque; +1, mild or low torque, the implant slightly changed
orientation but did not align to the magnetic field; +2,
moderate torque, the implant aligned gradually to the
magnetic field; +3, strong torque, the implant showed rapid
and forceful alignment to the magnetic field; +4, very strong
torque, the implant showed very rapid and very forceful
alignment to the magnetic field. Of note is that one of
the investigators (F.G.S.) has more than 20 years of
experience applying this qualitative scale to the characterization
of torque.
2.4. MRI-related heating
An in vitro experiment was performed at 3-Tesla/
128-MHz to determine MRI-related heating for the programmable
valve according to a previously described
protocol [12,17,19–21]. The programmable valve was
placed to approximate its intended in vivo use position in
a plastic head/torso phantom (head portion: width, 16.5 cm;
length, 29.2 cm; height, 16.5 cm; torso portion: width,
43.2 cm; length, 61.0 cm; height, 16.5 cm). The phantom
was filled with a gelling agent in an aqueous solution (i.e.,
0.8 g/L NaCl plus 5.85 g/L polyacrylic acid in distilled
water) [12,17,19–21].
Temperatures were recorded using a fluoroptic thermometry
system (Model 3100, Luxtron, Santa Clara, CA) with
fluoroptic thermometry probes (Model SFF, 0.5 mm in
diameter) positioned on the programmable valve to record
temperatures associated with the greatest heating during
MRI, as follows [12]: Probe 1, sensor portion of the probe
placed in direct contact with one end of the programmable
valve; Probe 2, sensor portion of the probe placed in direct
contact with the other end of the programmable valve; Probe
3, sensor portion of the probe placed in direct contact with
the middle portion of the programmable valve. The
positions of the fluoroptic thermometry probes were verified
immediately before and after the heating experiment. The
accuracy of the fluoroptic thermometry equipment used to
record temperatures in this study is F0.18C.
MRI was performed at 3-Tesla/128-MHz on the gelled,
saline-filled phantom with the programmable valve using a
transmit radio frequency (RF) body coil to produce a
relatively high level of RF energy, as follows: fast spin-echo
pulse sequence; axial plane; multislice; repetition time,
425 ms; echo time, 14 ms; echo train length, 4; flip angle,
908; bandwidth, 16 kHz; field of view, 40 cm; imaging
matrix, 256 256; section thickness, 10 mm; number of
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