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Objective: For cochlear implant recipients, undergoing magnetic resonance imaging (MRI) scans is associated with safety risks and potential side effects. Even following safety guidelines, potential complications (e.g., pain, magnet dislocation, image artifacts) are possible during 1.5 Tesla (T) MRI scans. The stronger static magnetic field of a 3.0 T scanner is associated with further risks of complication, including implant demagnetization. These complications led to the recent development of rotatable internal receiver magnets with a diametrical magnetization. The aim of this study was to evaluate the potential occurrence of pain during 3.0 T MRI scans for cochlear implant recipients with a rotatable, diametrically magnetized implant magnet. Patients: Five patients implanted with a cochlear implant diametrically magnetized magnet. Intervention: MRI scanning at 3 T. Main Outcome Measure: In the prospective patient study an MRI scan was performed on five implantees and the degree of pain was evaluated by a visual analog scale. Scans were performed initially with a magnet-supporting headband, and depending on the degree of discomfort/pain, repeated without the headband. Results: In all the patients, all the MRI scans were performed without any pain, even without the use of the supportive headband. Demagnetization was clinically not observed. Conclusion: 3.0 T MRI scanning can be performed on cochlear implant recipients with a rotatable diametrically magnetized internal magnet without risk of the most frequent cochlear-implant-related MRI complication: pain. This finding enables the expansion of MRI scanning indications up to 3.0 T without complication. Limitations in terms of MRI artifact still persist. Key Words: Cochlear implant— MRI—Pain.
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Pain Free 3 T MRI Scans in Cochlear Implantees
Ingo Todt, yAnja Tittel, Arne Ernst, yPhilipp Mittmann, and ySven Mutze
Department of Otolaryngology, Head and Neck Surgery; and
y
Department of Radiology, Unfallkrankenhaus Berlin, Berlin, Germany
Objective: For cochlear implant recipients, undergoing mag-
netic resonance imaging (MRI) scans is associated with
safety risks and potential side effects. Even following safety
guidelines, potential complications (e.g., pain, magnet dislo-
cation, image artifacts) are possible during 1.5 Tesla (T)
MRI scans. The stronger static magnetic field of a 3.0 T
scanner is associated with further risks of complication,
including implant demagnetization. These complications led
to the recent development of rotatable internal receiver
magnets with a diametrical magnetization.
The aim of this study was to evaluate the potential
occurrence of pain during 3.0 T MRI scans for cochlear
implant recipients with a rotatable, diametrically magnetized
implant magnet.
Patients: Five patients implanted with a cochlear implant
diametrically magnetized magnet.
Intervention: MRI scanning at 3 T.
Main Outcome Measure: In the prospective patient study
an MRI scan was performed on five implantees and the
degree of pain was evaluated by a visual analog scale. Scans
were performed initially with a magnet-supporting headband,
and depending on the degree of discomfort/pain, repeated
without the headband.
Results: In all the patients, all the MRI scans were
performed without any pain, even without the use of the
supportive headband. Demagnetization was clinically not
observed.
Conclusion: 3.0 T MRI scanning can be performed on
cochlear implant recipients with a rotatable diametrically
magnetized internal magnet without risk of the most frequent
cochlear-implant-related MRI complication: pain. This find-
ing enables the expansion of MRI scanning indications up to
3.0 T without complication. Limitations in terms of MRI
artifact still persist. Key Words: Cochlear implant
MRIPain.
Otol Neurotol 38:xxxxxx, 2017.
Cochlear implantation is the treatment of choice for
patients with severe to profound sensorineural hearing
loss and is an increasingly more common treatment
option for patients with moderate and single-sided deaf-
ness. So far, approximately 400,000 patients have
received a cochlear implant.
Similar to cardiac pacemakers, magnetic resonance
imaging (MRI) observations in cochlear implant recip-
ients present significant potential complications. In par-
ticular, the internal magnet used for fixation between the
implant and audio processor requires special consider-
ation. Previous trials with an alternative, magnet-free
implant system did not lead to significant acceptance (1).
MRI interactions with the internal cochlear implant
magnet can lead to a number of difficulties and adverse
events. The magnet can generate significant image arti-
facts, resulting in the inability to assess specific ipsilat-
eral structures (2). However, depending on the scan
sequence used and the position of the implant, image
visibility can be optimized to allow for an assessment of
the cochlea and the internal auditory canal (3,4). Dislo-
cation of a removable internal magnet can occur when
passing through the MRI static magnet field, causing pain
and acting as a source of infections (5). Use of specific
headbands or bandages designed to provide additional
support to maintain the internal magnet’s position is
common and the number of magnet dislocations is
described to be rare (6). The occurrence of pain and
discomfort during the scan is the most frequent compli-
cation with a rate between 45 and 70% (6,7). Often MRI
scans cannot be performed or completed due to pain-
related complications (7). Demagnetization is an addi-
tional risk specific to 3.0 T MRIs and is dependent on the
orientation of the internal magnet with respect to the MRI
magnetic field (2).
The use of an MRI with a cochlear implant recipient
therefore requires special consideration. The different
cochlear implant companies apply different strategies to
enable safe MRI scans of their implant recipients.
Cochlear (Cochlear Corp., Sydney, Australia) recom-
mends the use of headbands for 1.5 T scanning and
has safety approval for 3.0 T MRI scans for most of
their implants, provided the internal magnet is removed.
Address correspondence and reprint requests to Ingo Todt, Depart-
ment of Otolaryngology, Head and Neck Surgery, Unfallkrankenhaus
Berlin, Warenerstr.7, 12683 Berlin, Germany; E-mail: todt@gmx.net
This study was supported by Medel, Innsbruck, Austria.
The authors disclose no conflicts of interest.
DOI: 10.1097/MAO.0000000000001569
1
Otology & Neurotology
xx:xx– xx ß2017, Otology & Neurotology, Inc.
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Consequentially, surgery is required pre- and post-MRI
for magnet removal and reimplantation. Advanced Bion-
ics (Advanced Bionics, Sta¨fa, Switzerland) has safety
approval for 1.5 T scanning with the use of a specific
MRI antenna coil cover and a headband for most of their
implants. Oticon Medical (Oticon Medical, Valaudaris,
France) has approval for 1.5 T scans. In contrast to the
other implants presented, their current main device
(Neuro Zti) is screw fixated. MED-EL (MED-EL, Inns-
bruck, Austria) has approval for 1.5 T scanning with the
use of a headband and without magnet removal for their
range of implants. In addition, MED-EL’s SYN-
CHRONY implant contains a diametrically magnetized
and rotatable internal magnet designed to eliminate the
risk of demagnetization.
Cochlear implants usually have an axially magnetized
magnet in the implant (i.e., the magnet has one mag-
netic pole facing toward the skin flap). This allows the
coil and magnet of the externally worn audio processor
to be held magnetically over the implant. When placed
in an MRI scanner, a rotational force from the static
MRI magnet acts upon the implant. With MRI scanners
higher than 1.5 T, the implant magnet would become
weaker.
The SYNCHRONY implant has a magnet that is
rotatable and is diametrically magnetized (i.e., the axis
of magnetization is perpendicular to the axis of the
magnetic disc). This allows the magnet to turn freely
and self-align in response to an external magnetic field,
like the needle of a compass. In an MRI scanner, the
implant magnet can align parallel to the static magnetic
field of the MRI scanner. Therefore, the magnet cannot
weaken and practically no rotational force is acting upon
the implant.
Clinical experiences with the SYNCHRONY implant
during 3.0 T MRI are absent so far. The aim of this
prospective study was to evaluate the occurrence of pain
in cochlear implant recipients with implant systems
containing a rotatable, diametrically magnetized internal
magnet during MRI scans at 3.0 T.
METHODS
The study was approved by the institutional review board of
the Unfallkrankenhaus Berlin, Germany (IRB-ukb-HNO-2016/
10). This study was supported by a grant (MEDEL, Innsbruck,
Austria). Patients gave their written informed consent for the
use of their clinical records in this prospective study.
In this prospective case study five patients underwent a 3.0 T
MRI observation in a tertiary referral center. Between 2014 and
2017, all the patients were implanted with a MED-EL SYN-
CHRONY implant (MED-EL, Innsbruck, Austria) with a dia-
metrically magnetized internal magnet. The implant was
intraoperatively fixed within a drilled implant bed using
resorbable sutures.
All the examinations were performed in a 3.0 T MR imaging
unit (Achieva, Philips Medical Systems, Best, NL). First, the
patients were brought into the MRI scanner with a headband
fixated over the implant. After the evaluation of pain and
inspection of the implant area, the patients were placed inside
the MRI scanner again, this time without a headband.
Scanning parameters:
TSE T2 2 D: TR: 2,500 milliseconds, TE 120 milliseconds,
slice thickness 1.5 mm, reconstruction resolution of 0.18 0.18
1.5 mm, F0 V 130 130, 20 slices.
RESULTS
In all the patients, with and without a headband,an MRI
scan at 3.0 T could be performed with no magnet disloca-
tion or pain-associated complications. In all the cases, a
headband was not necessary to prevent pain or magnet
dislocation. With and without headband, the mean visual
analogue scale in terms of pain was 0 (i.e., no pain).
Figure 1 shows an exemplary MRI scan with the assess-
ment of the implanted cochlea with ipsilateral cochlear
implant at 3.0 T. None of thepatients reported a noticeable
change in the strength of the implant magnet (Fig. 2).
DISCUSSION
MRI scans are now a routine diagnostic tool in radiol-
ogy used on a daily basis worldwide in most modern
FIG. 1. A, MRI T2W at 3 Tsequence scanning of internal auditory canal with CI in place. Specific positioning of the implant receiver magnet
allows for the assessment of the cochlea. B, Lateral overview of the MRI artifact pattern. CI indicates cochlear implant; MRI, magnetic
resonance imaging.
2 I. TODT ET AL.
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ON-17-226
hospitals. Therefore, the probability that an MRI is
needed within a life time is very high (8). At 1.5 T,
MRI scans with cochlear implant recipients are associ-
ated with artifacts (9), magnet dislocations (5), and as
most frequently reported: pain (6). The stronger static
magnetic field of the 3.0 T MRI presents similar, often
magnified efficacy and safety risks, with the additional
concern of implant magnet demagnetization (2).
Although manufacturers recommend use of a head-
band during an MRI scan to prevent pain and magnet
dislocation, this approach has been shown to be ineffec-
tive (6,7) and can in itself be a barrier to scanning.
Clinically, the effectiveness of two implant modifications
(i.e., screw fixation, diametrical magnetization) to pre-
vent this complication at 1.5 T has been observed. It is
assumed that the screw fixation of a rigid integrated
internal magnet (Oticon ZTI implant) prevents any mag-
net field-related positional change of the receiver. This
holds the implant in place even if the magnetic field force
is laterally applied and tries to lift the implant magnet.
With the increasing number of 3.0 T scanners in
radiological departments, understanding the behavior
of implants in the vicinity of these machines is of
increasing importance.
Although Cochlear (Sydney, Australia) allows 3.0 T
scans if the internal magnet is temporarily explanted, the
MED-EL SYNCHRONY implant includes a diametri-
cally magnetized rotatable internal magnet which self-
aligns parallel with the external magnetic field of the
MRI scanner. This unique ability of the implant magnet
to align with the main magnetic field of the MRI scanner
was obviously helpful to prevent demagnetization at 3.0
T, but the effect on pain prevention is so far unclear. We
were able to show that the implant magnet configuration
prevents the occurrence of pain at 3.0 T. In the five
patients tested, magnet dislocation was not observed.
Subjectively, all the patients reported no change of the
magnetic attachment force of the antenna coil, indicating
an unchanged magnetic function of the internal magnet.
The prevention of pain and magnet dislocation is of
high importance, since these two factors are the most
frequently reported and relevant complications in
clinical practice.
The ability to perform an MRI scan without pain or the
risk of magnet dislocation provides the possibility of
performing 3.0 T MRI scans routinely with only some
limitations (e.g., artifact relevant limitations, Tesla
strength limitations [>3T]).
CONCLUSION
For cochlear implant recipients with a rotatable, dia-
metrically magnetized internal magnet, MRI scanning at
3.0 T can be performed pain free and without the use of
a headband.
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FIG. 2. A, Implant with regular magnet configuration. Implant with a rotational, diametrically internal magnet. B, Rotational, diametric
internal magnet without applied magnetically force. Change of the internal position of the rotational, diametric magnet related to an applied
external magnetic field (arrows show magnetic field direction).
COMPLICATION IN CI PATIENTS 3
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Background: Cochlear implants (CI) are the preferred method of treatment for patients with severe to profound bilateral sensorineural hearing loss and unilateral deafness. For many years, because of the magnetic field applied during magnetic resonance imaging (MRI) examinations, MRI examinations were contraindicated for CI patients or feasible only under specific circumstances. MRI examinations of CI recipients entail complications and therefore preventive measures have to be considered. The aim of this study was to evaluate the prevalence of MRI scans in CI recipients and the occurrence of complications and furthermore to investigate the preventive measures taken in radiological daily routine. Materials and methods: A retrospective questionnaire was sent to 482 patients that received CIs from 1999–2013. Details of the MRI examination and subjective and objective incidents during and after the MRI scan were evaluated. Results: A total of 204 CI recipients answered the retrospective questionnaire (42.3 %). Twenty patients (9.8 %) with 23 implants underwent a total of 33 MRI scans with their cochlear implant in place. In 16 cases the scanned region was the head (49 %). Preventive measures in the form of head bandages were taken in 20 cases (61 %). The most common complication was pain in 23 cases (70 %) and the most serious complication was the dislocation of the internal magnet in 3 cases (9 %). Conclusions: The number of CI recipients undergoing MRI scans is high. Possible complications and preventive measures attract too little attention in radiological daily routine.
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Background: Cochlear implants (CI) are the preferred method of treatment for patients with severe to profound bilateral sensorineural hearing loss and unilateral deafness. Because of the magnetic field applied during magnetic resonance imaging (MRI) examinations, for many years, MRI examinations were contraindicated for CI patients or feasible only under specific circumstances. MRI examinations of CI recipients entail complications and therefore preventive measures have to be considered. The aim of this study was to evaluate the prevalence of MRI scans in CI recipients and the occurrence of complications and furthermore to investigate the preventive measures taken in radiological daily routine. Materials and methods: A retrospective questionnaire was sent to 482 patients that received CIs in the years 1999–2013. Details of the MRI examination and subjective and objective incidents during and after the MRI scan were evaluated. Results: Two hundred and four CI recipients answered the retrospective questionnaire (42.3%). Twenty patients (9.8%) with 23 implants underwent a total of 33 MRI scans with their cochlear implant in place. In 16 cases, the scanned region was the head (49%). Preventive measures in the form of head bandages were taken in 20 cases (61%). The most common complication was pain in 23 cases (70%) and the most serious complication was the dislocation of the internal magnet in three cases (9%). Conclusions: The number of CI recipients undergoing MRI scans is high. Possible complications and preventive measures attract too little attention in radiological daily routine.
Article
Hypothesis: To evaluate the assessment of the internal auditory canal and the labyrinth in relation to different CI magnet positions and MRI sequences at 3 T. Background: The indication criteria for cochlear implantation have been changed over the years and the growing number of implantations in patients after acoustic neuroma resections underline the importance of a postoperative MR imaging to assess the internal auditory canal (IAC) and the labyrinth. The MRI artifact induced by the cochlear implant magnet is a known problem that should be further observed by this investigation. Methods: We compared the artifacts of Cochlear 512 magnets at different head positions in vivo at 3 T. The observed positions varied with a nasion-external ear canal angle of 90, 120, and 160 degrees and a variable distance of 5, 7, and 9 cm in relation to the external ear canal and different MRI sequences. Results: The complete assessment of the internal auditory canal and labyrinth was possible with a magnet positioned at 90 degrees and 9 cm and 160 degrees and 9 cm. Evaluation of the IAC alone was possible with magnet positions at 90 degrees and 7 cm and 9 cm, 120 degrees and 9 cm, and 160 degrees and 7 cm and 9 cm. A high-resolution 3D T2w Drive sequence decreased the visibility of the structures significantly. A high-resolution TSE 2D T2w sequence together with one of the above-described positions allowed sufficient visualization of the structures. Conclusion: The position of the implant and the MRI sequence used determine the assessment of the IAC and the labyrinth at 3 T MRI. A position of the implant magnet at a nasion-external auditory canal angle which is more horizontal and posterior than so far commonly used allows a better visualization of the IAC and the labyrinth at 3 T.
Article
Patients with cochlear implants (CIs) should be fully informed before undergoing magnetic resonance imaging (MRI) about the possibility of discomfort or pain. Prior to an MRI scan, patients need to fully understand not only the potential complications but also the potential discomfort that they may experience during the scan. To assess the adverse events during MRI in patients with CIs and to investigate the safety and diagnostic efficiency of MRI in patients with CIs with internal magnets. Retrospective review of the medical records of 18 patients with CIs undergoing MRI between September 2003 and February 2014 at a single tertiary referral center. Sixteen patients underwent MRI in a 1.5-T scanner, and 2 patients underwent MRI in a 3.0-T scanner. Twelve brain MRI scans were performed, and 18 MRI scans were performed in areas outside the brain. Discomfort or pain, adverse events, and auditory performance after MRI were evaluated using medical records or interviews. Thirteen of 18 patients completed their MRI scans (25 of 30 scans). Five patients with head bandages were unable to complete their MRI scans owing to pain; one of these patients experienced magnet displacement, and another underwent surgery for magnet removal and reinsertion. Finally, 1 patient experienced polarity reversal of the magnet. Artifacts induced by the CI internal magnet compromised the diagnosis of ipsilateral brain lesions under 1.5-T MRI. Auditory performance in the CI recipients who had major events was unaffected. Even with protective head bandages, 1.5-T MRI in patients with CIs led to a variety of adverse events, including discomfort or pain and displacement of the internal magnet. Therefore, sedation and careful head positioning may be appropriate for some patients with CIs who undergo MRI, and these patients should be carefully monitored to decrease the likelihood of such adverse effects.
Article
To assess the impact on image quality of MRI without magnet removal in cochlear implant (CI) and auditory brainstem implant (ABI) users with neurofibromatosis type 2 (NF2). Prospective cohort. Tertiary center for cochlear and auditory brainstem implantation. Thirteen patients (10 ABI, 3CI) with NF2 underwent a total of 76 MRI scans. MRI without magnet removal. Ability to visualize the ipsilateral and contralateral cerebellopontine angles (CPAs) and internal auditory meati (IAM) with head MRI. Of the 76 scans, 40 were of the head, 28 of the spine and 8 of other regions. Scanning was performed with a tight head bandage and plastic card. There were no cases of altered implant function or demagnetization of the device magnet.A grading system was used to assess the view of the ipsilateral IAM-CPA. In 85% of head scans, the view was unimpaired (Grade 0). In 13%, there was distortion (Grade 1). In 2% (1 case), the view was entirely obscured by artifact (Grade 2). Views of the contralateral CPA and IAM were unimpaired in all cases. The best 3 sequences for the depiction of the ipsilateral IAM-CPA (percent graded as 0) were as follows: axial 3D inversion recovery prepared fast spoiled gradient echo (100%), 2 mm coronal T1W of the IAM-CPA (88.9%), and 2 mm axial T1W of the IAM-CPA (76.9%). MRI scanning without magnet removal is safe and well tolerated in NF2 patients with auditory implants. With appropriate MRI sequences, the image quality is not significantly impaired.
Article
To analyze the cause and effect of magnet dislocation in cochlear implant (CI) recipients requiring magnet revision surgery for treatment. Retrospective study. Tertiary referral center. Case reports from 1,706 CI recipients consecutively implanted from January 2000 to December 2011 were reviewed. The number of cases requiring magnet revision surgery was assessed. Revision surgery involving magnet removal or replacement was indicated in 1.23% (21/1,706), of all CI recipients. Magnet dislocation occurring during magnetic resonance tomography (MRI), at 1.5 Tesla (T), with the magnet in place and with the application of compression bandaging around the head, was the main cause for revision surgery in 47.62% (10/21) of the affected cases.All 10 cases were implanted with Cochlear Nucleus cochlear implants. These events occurred, despite adherence to current recommendations of the manufacturer. The present study underlines that MRI examination is the main cause of magnet dislocation. The use of compressive bandaging when using 1.5-T MRI does not eliminate the risk of magnet dislocation. Additional cautionary measures are for required for conditional MRI. We recommend X-ray examination after MRI to determine magnet dislocation and avoid major complications in all cases reporting pain during or after MRI. Additional research regarding silicon magnet pocket design for added retention is needed. Effective communication of guidelines for precautionary measures during MRI examination in CI patients is mandatory for all clinicians involved. MRI in CI recipients should be indicated with caution.
Article
To assess the safety of 1.5 T magnetic resonance imaging (MRI) in patients with cochlear implants (CIs) with internal magnets. Retrospective review of CI patients who underwent an MRI at Johns Hopkins. Sixteen patients with a mean age of 43 ± 22 years with a CI underwent a total of 22 clinically indicated 1.5 T MRI. Devices from 3 major CI manufactures were represented. Binding of CI with mold material and gauze was performed before MRI. Some patients were also administered a sedative. Intravenous gadolinium contrast was used in all but 1 patient. Patients were assessed with regard to the ability to complete the MRI, the size of the artifact caused by the device, the ability to make a diagnosis from the studies, the post-MRI CI function, and the magnet's position. No CI malfunction, displacement, or magnet displacement was observed after MRI. One patient was unable to tolerate the procedure because of pressure at the site of the device. One patient required intravenous sedation to complete the study. The CI generally produced an artifact on brain MRI, with a mean maximal anterior-posterior dimension of 6.6 cm and a lateral dimension of 4.8 cm around the site of the device. The contralateral internal auditory canal was visualized in all patients, and the ipsilateral internal auditory canal was at least party visible in all but 1 patient. Patients can safely undergo 1.5 T MRI after CI if the device is tightly bound before scanning. Magnet displacement was not observed, and we think the risk to be minimal compared with the risk and inconvenience of removing the magnet before the study.
The aim of this study was to evaluate artifacts produced by cochlear implants (CI) during 3.0 Tesla (T) magnetic resonance imaging of the brain using different sequences on phantom and cadaveric specimens. A phantom and three cadaveric specimens with CIs were imaged using a 3.0 T clinical scanner. Artifacts were analyzed quantitatively and according to the sequence used. Different brain regions were evaluated for image distortion and limitation of diagnostic significance. In cadaver studies, all sequences generated signal-void areas around the implant. In T2-weighted sequences, additional periodic shadowing was discovered. Anatomical structures of the brain on the contralateral side of the CI were for the most part undistorted. At 3T, artifacts around CIs with non-removable magnets compromise image quality of the nearby brain regions and diagnosis of brain lesions is limited. In the contralateral hemisphere, diagnostic accuracy is only marginally limited.
Article
To ensure good transmission of electromagnetic signals from the speech processor to the internal cochlear stimulator (ICS) in cochlear implants, exact alignment of the external transmitter coil over the receiver coil of the ICS is necessary. Usually this is achieved by two magnets: one implanted within the ICS, the other one integrated into the transmitter coil of the external headset. Although this principle works, there are some serious problems with the implanted magnet. The most serious of these is that it renders MRI studies potentially hazardous or impossible, or at least compromises image quality. We developed a method to eliminate the magnet. The method requires varying the implantation technique and using a special headset. The technique is easy to perform, and the headset is suitable for series production. Experience with our first patients revealed the coil alignment to be remarkably stable, even more than in patients with a cochlear implant equipped with a magnet. Results of the first ten patients are presented. Aside from eliminating the magnet, we attempted to optimize the acoustic properties of the headset. This resulted in design changes such as repositioning the microphone. Further improvements such as integration of telephone coils and special sockets to connect peripheral appliances can easily be implemented in our special headset.
Article
Dramatic increases in both magnetic resonance imaging (MRI) usage and cardiac device-based therapy have resulted in an estimated 50-75% probability of a patient being indicated for an MRI over the lifetime of their device. Some recent studies have demonstrated "safe procedures" and "no adverse events" in the limited populations, clinical situations, and specific devices and lead orientations tested. While these investigations are useful to help ascertain the hazards for patients with cardiac devices, they do not demonstrate clear freedom from risk. All components of active implantable systems must be engineered during the design stage to provide safety in current and evolving MR environments. Device manufacturers need to secure regulatory approval to confirm their products' safety under multiple clinical and technical variables.