Download E2621 - Imaging Cyborgs the safe MR imaging of patients with

Imaging Cyborgs : the safe MR imaging of
patients with cardiovascular implantable
electronic devices
Dr Pei Ghim Poh1
Dr Charlene J Liew2
Dr Angeline Poh2
*
1
2
Diagnostic Radiology, Singhealth Residency, Singapore
Department of Diagnostic Radiology, Changi General Hospital, Singapore
* photograph of minifigurine © the authors 2014. In compliance with fair use copyright laws.
Disclosure statement
 The authors declare that there are no
conflicts of interest
Goals and Objectives
 Overview of MRI-induced hazards with non-compatible CIEDS
 Introduction to how CIEDs have been re-engineered to make
them MR conditional
 Limitations of MRI conditional CIEDS
 Pictorial review of the radiographic features of MR conditional
devices
 Outline steps enabling the safe scanning of MR conditional
CIEDs
Target audience
Radiologists, radiologic technologists, physicists, hospital administrators,
cardiologists, cardiovascular device technologists
Background
 Magnetic resonance imaging (MRI) has
steadily increased in usage worldwide.
Parallel to its growth is the number of
patients with cardiovascular implantable
electronic devices (CIEDs)
 2 million Americans have CIEDs; an
estimated 75% of these individuals will have
an indication for MRI during the lifetime of
their device (Chow et al 2014)
Chow GV, Nazarian S. MRI for patients with cardiac implantable electrical devices. Cardiol Clin. 2014 May;32(2):299–304.
Overview of MRI-induced hazards
with non-compatible CIEDs
Torque effect
 Certain components within the CIED are
ferromagnetic
 Subject to potential magnetic field induced
torque which might result in movement of the
internal components or system dislodgement
Gotte, et al. Magnetic resonance imaging, pacemakers and implantable cardioverter defibrillators: current situation and clinical perspective.
Neth Heart J. Jan 2010; 18(1): 31-37
 Reed switch activation
 consists of two metal strips in a glass capsule
 switch can be activated or inactivated by external
magnetic field
 activation or deactivation depends on the orientation
of the switch in relation to the static magnetic field
 may malfunction by staying in open/closed positions
 may be life-threatening in patients with recent
myocardial infarction, hypoxemia or major
electrolyte imbalance
 activation of the reed switch  preset pacing at 80100 bpm  may induce VF
1. Gotte, et al. Magnetic resonance imaging, pacemakers and implantable cardioverter defibrillators: current situation and clinical
perspective. Neth Heart J. Jan 2010; 18(1): 31-37
2. Jacob, et al. Clinical applications of magnets on cardiac rhythm management devices. Europace. 2011;13(9):1222-1230.
3. Loewy, et al. Reconsideration of pacemakers and MR imaging. Radiographics, 2004;24:1257-1268
Reed Switch activation
Open Reed switch
Contact plate
Reed blade
Closed Reed switch
Fig 1: Reed switch activation by magnetic field
 Induced electrical currents
 gradient magnetic fields during MRI scanning
may induce currents in the leads
 may result in oversensing or undersensing
leading to inappropriate high rate pacing or
inhibition of pacing
 RF pulse may also induce high rate pacing
caused by oversensing
 Induced electrical currents (continued)
 In ICDs, gradient magnetic fields can mimic
intrinsic cardiac activity which may be
interpreted as ventricular tachycardia
(oversensing)
 resulting in inappropriate therapy (shock)
Gotte, et al. Magnetic resonance imaging, pacemakers and implantable cardioverter defibrillators: current situation and clinical perspective.
Neth Heart J. Jan 2010; 18(1): 31-37
 Antenna effect
 RF pulse generated during MRI may induce current
in the lead system which functions as an antenna
 tissue near the tip of the lead has limited
conductivity, therefore energy will be converted to
heat at the lead tip
 may cause thermal damage including formation or
edema or scar tissue
 may result in increasing stimulation threshold and
ultimately loss of capture
Van der Graaf, et al. MRI and cardiac implantable electronic devices; current status and required safety conditions. Neth Heart J. Jun 2014;
22(6): 269–276.
Re-engineering MR conditional cardiac devices
Vendor specific identifier
Magnetic protection
 Optimal thickness insulation
to minimize local SAR 1
 Reduction in nonferromagnetic components2
MRI Mode:
 Bipolar stimulation2
 Reduce time needed
to remain in MRI mode
 External activators
 Care program pathway
Safety Mechanisms3
• Hall-effect sensor
• Reactivation mechanism
Reduction in heat generation
 Resistive, coiled, RF trap and billabong
elements in leads1
 Decrease pitch of the inner coil
 Reduce number of filars – this geometry
reduces the number of radiofrequencies
that can conduct through the lead
filaments7
Fig 2: engineering of MR conditional CIEDS
---------------------------------------------
Reduce tissue inflammation4
• Steroid elution at lead-tissue
interface
Torque and Heat Dissipation5,6
•
•
•
•
Filters
Cooling mechanism
Increase surface area
Reduce Torque effects
1. Bottomley, et al. Designing passive MRI-safe implantable conducting leads with electrodes. Med Phys. 2010 Jul;37(7):3828-43
2. Van der Graaf, et al. MRI and cardiac implantable electronic devices; current status and required safety conditions. Neth Heart J. Jun 2014; 22(6): 269–276.
3. Jacob, et al. Clinical applications of magnets on cardiac rhythm management devices. Europace. 2011;13(9):1222-1230.
4. Medtronic For Healthcare Professionals: Pacing Leads http://www.medtronic.com/for-healthcare-professionals/products-therapies/cardiac-rhythm/pacemakers/pacing-leads
5. Kodali, et al. Safety of MRIs in Patients with pacemakers and defibrillators. Cardiovasc J. 2013 Jul-Sep; 9(3): 137–141.
6. Gotte, et al. Magnetic resonance imaging, pacemakers and implantable cardioverter defibrillators: current situation and clinical perspective. Neth Heart J. Jan 2010; 18(1): 31-37
7. Shinbane, et al. Magnetic resonance imaging in patients with cardiac pacemakers: era of "MR Conditional" designs. JCMR 2011; 13:63
Lead Modification
 vendor-specific identifier
 magnetic protection
 insulation to minimize local specific absorption
rate (SAR)
 reduction in heat generation and torque
 resistive, coiled, RF trap and billabong




elements in leads
decrease pitch of the inner coil
reduce number of filars – this geometry
reduces the number of radiofrequencies that
can conduct through the lead filaments
reduction in non-ferromagnetic components
filters to reduce electromagnetic interference
(EMI)
Fig 3: Medtronic’s CapSure Fix
MRITM lead (right) shows
change in inner coil geometry to
reduce induction energy transfer
compared to older model (left)
1. Bottomley, et al. Designing passive MRI-safe implantable conducting leads with electrodes. Med Phys. 2010 Jul;37(7):3828-43
2. Van der Graaf, et al. MRI and cardiac implantable electronic devices; current status and required safety conditions. Neth Heart J. Jun
2014; 22(6): 269–276.
3. Shinbane, et al. Magnetic resonance imaging in patients with cardiac pacemakers: era of "MR Conditional" designs. JCMR 2011; 13:63
Lead-tissue interface
 steroid elution
• reduces inflammation
• provides optimal threshold behavior
 Titanium Nitride (TiN) coated electrodes
• provide low tip-to-tissue polarization
 optimize surface area
• reduces torque and helps dissipate heat
• takes into account blood-flow for heat
dissipation
1. Biotronik: Solia: Safely reinvented: Product information
2. Medtronic For Healthcare Professionals: Pacing Leads http://www.medtronic.com/for-healthcare-professionals/products-therapies/cardiacrhythm/pacemakers/pacing-leads
3. Kodali, et al. Safety of MRIs in Patients with pacemakers and defibrillators. Cardiovasc J. 2013 Jul-Sep; 9(3): 137–141.
4. Gotte, et al. Magnetic resonance imaging, pacemakers and implantable cardioverter defibrillators: current situation and clinical
perspective. Neth Heart J. Jan 2010; 18(1): 31-37
Pulse generator box modifications
 vendor-specific identifier
 safety mechanisms
• magnet-activated switch to preset settings
• reactivation mechanism
 MRI Mode (covered in next slide)
1. Jacob, et al. Clinical applications of magnets on cardiac rhythm management devices. Europace. 2011;13(9):1222-1230
2. Van der Graaf, et al. MRI and cardiac implantable electronic devices; current status and required safety conditions. Neth Heart J. Jun
2014; 22(6): 269–276.
MRI modes
Is device MRI Safe?
Device implanted ≥6
weeks ago?
No
Perform alternate examination
Sensing only mode

Yes

Is patient
pacemaker
dependent?
No
Interrogate device and
program to 'sensing only'
mode
Asynchronous mode


Yes

Interrogate device and
program to 'asynchronous
pacing' mode
pacemaker programmed to off/sub
threshold outputs
lead polarity to bipolar

pacing occurs at a fixed rate
well tolerated for short periods of time
risk of developing VF during
asynchronous pacing is extremely low
however, to optimise safety, prolonged
asynchronous pacing should be avoided.
ICD temporary deactivation
Yes
ICD?
Deactivate ventricular
sensing, anti-tachycardia
therapy
No


Limit MRI Settings:
SAR ≤2.0 W/kg
Magnetic field strength ≤1.5 T


Fig 4: Commonly used
pacemaker MRI Mode
pathway
ICD devices may falsely detect VT and
subsequently deliver pacing,
cardioversion or defibrillation therapies
which may lead to actual arrhythmias
switches (Reed and Hall-sensor) prevent
therapies from being delivered but are
unpredictable. Deactivation is a safer
option
1. Duru, et al. Pacing in Magnetic Resonance Imaging Environment. Eur Heart J. 2001; 22(2): 113–124
2. Kodali, et al. Safety of MRIs in Patients with pacemakers and defibrillators. Cardiovasc J. 2013 Jul-Sep; 9(3): 137–141.
3. St Judes Medical Inc. Everything and MRI. http://professional-intl.sjm.com/products/crm/pacemakers/dual-and-single-chamber/accent-mri
Reduce time in MRI Mode
 change in workflow
• reprogram device closer to time of MRI scan
 external hand-held activators simplify access to MRI
settings
• easy to use
Patient
needs MRI
Scan
Goes to
Cardiology
Centre/ MRI
Clinic
Old Workflow
Device
Programmed
Patient
needs
MRI Scan
MRI Mode
Goes to
Cardiology
Centre/ MRI
Clinic
Patient has
MRI Scan
New Workflow
Patient
has MRI
Scan
Reprogram
back to
permanent
settings
Patient
goes home
Patient
goes
home
Default Mode
Fig 5: hand-held external activator
by St Jude Medical and change in
workflow
Prevention of electromagnetic interference:
Hall-effect sensor
 Hall-effect sensor
 based on the generation of voltage across an electrical




conductor, when the magnetic field is perpendicular to
the direction of the conductor current flow
varies output voltage in response to a magnetic field,
thus has a more predictable behavior
functions as a transducer to trigger an electronic
switch to 'ON' or 'OFF' when activated by a magnetic
field
can be programmed to lock out when undergoing MRI
scan
gradually replacing Reed switches
Shinbane, et al. Magnetic resonance imaging in patients with cardiac pacemakers: era of "MR Conditional" designs. JCMR 2011; 13:63
Hall effect Sensor
Fig 6: Hall Sensor activation by magnetic field
Perpendicular
magnetic field
+
Output
Constant
current flow
-
Limitations of MR conditional CIEDs
 patients must wait 6 weeks after implant prior to MRI
 pre-existing devices
• old leads and pulse generator must be removed for replacement
 certain devices cannot be scanned with isocenter over
thorax (above C1 and below T12 vertebrae)
• newer models have no zone restriction
 generally not recommended to scan in a magnet with a
field strength above 1.5T
 some devices still require special personnel and
monitoring
 increased cost may be prohibitive
•
cost-benefit ratio: more favorable for younger patients or those who are
expected to require many MR studies
Radiographic features of MR
conditional CIEDs: pictorial review
 plain radiographs may be used to identify the
pacemaker as a MR conditional device
 markers are unique to each manufacturer
 Conditions prior to scanning differ from model to model
 Most commonly located at the :
• 1) pulse generator
1
and/or
• 2) lead
2
MRI
Towards lead tip
Fig 7 : Diagram to show common placement of CIED identifiers
Chest radiograph example
Fig 8 : Diagram to demonstrate
relative size of identifier
Pitfalls:

it can be quite difficult to
identify the model just by
using the identifier

the identifier may be
covered by soft tissue or
components such as
circuitry or capacitors

view affected by rotation
MR conditional pacemakers
radiograph features: St Jude Medical
Fig 9: Identifier on an MR conditional pacemaker (Accent™ MRI) consists
of:
1. St Jude M.
manufacturer
identifier
2. MRI symbol
on pulse
generator
Fig10: Identifier on an MR conditional
lead: (Tendril ™)
Fig 11: Identifier on a non-MRI
conditional pacemaker (Accent™)
St Jude M.
brand
identifier is
seen without
MRI symbol
MR conditional pacemakers
radiograph features: Medtronic
Fig 12 A and B : two different MR conditional pacemakers
A) Revo Surescan™
B) Ensura/Advisa MRI™
Fig ? :
Fig 13 : identifier on MR conditional lead
CapSureFix SureScan™ 5086
pitfall: There are no radiopaque
markers on the MRI conditional
SureScan 5076 lead. Patient
records must be checked.
the symbol circled in
green functions as the
marker; located above
the model identifier
and manufacturer
logo
Fig 14: Identifier on a
non-MRI conditional
pacemaker (Adapta™)
MR conditional pacemakers
radiograph features: Biotronik
 consists of the Evia™ and Entovis™ Pacing systems
 both do not have specific markers to indicate MRI-
conditional status on the pulse generator or leads
 but device model is radio-opaque and visible on x-ray
• hence there is a need to:
• identify the device model / family
• review patient documentation as
to whether leads are MR safe
Biotronik
manufacturer
marker
Specific device
marker
Fig 15: Appearance of the radiopaque marker for Evia
device
MR conditional pacemakers
radiograph features: Boston Scientific
 pulse generator shows a radio-opaque identifier at the
head of the device
• first 3 letters BSC/BOS represents manufacturer
• numbers are present to identify the model number
• preceding filled triangle indicates MR conditional status
Fig 16: Label for ADVANTIO
MRI, INGENIO MRI, VITALIO
MRI, FORMIO MRI
Fig 17: actual label from the same
device family which is not MR
conditional
 two radiopaque platinum bands are visible at the terminal
region of the MRI lead
Fig 18: Reliance-4-Front MRI –conditional lead
Summary chart for all vendors
 identify manufacturer and model number
 look for MR conditional markers
 not visible all the time (may need to rely on
other features)
Table 1 : Manufacturers and their respective radiopaque markers
St Jude
Medical
Medtronic
Biotronik
Boston
Scientific
Manufacturer
identifier
MR conditional
marker on pulse
generator
MR conditional
lead markers
(identify
model no.)
Yes
Yes
No
Yes
Indirect ways to identify model
 occasionally it may be impossible to obtain documentation
e.g. travel, emergency setting, etc.
 S Jacob, et al. described a method to identify the type of
device used using the CaRDIA-X algorithm
 a summary diagram is shown below
Fig 19: Summary diagram of CaRDIA-X Algorithm
Obtain device information from DOI+ID if possible
CXR: look at identifier
Not an ICD
Identifier not visible
Shape of battery
Device is an ICD
(high voltage coils)
Semilunar
Use 5Cs:
Can, Cell (battery), Capacitor, Circuitry, Connectors
Circular/
rectangular
battery
ILR
Once identified
Call the Manufacturer
Jacob, S., Shahzad, M. A., Maheshwari, R., Panaich, S. S., & Aravindhakshan, R. (2011). Cardiac rhythm device identification algorithm using
X-Rays: CaRDIA-X. Heart Rhythm: The Official Journal of the Heart Rhythm Society, 8(6), 915–922.
MR conditional implantable cardioverterdefibrillator (ICD)
 radiographically similar
to pacemakers apart
from high-voltage
defibrillation coils
• appear as thick bands at
the SVC and RV apex
 a limited number of
ICDs are MR
conditional
• Medtronic Evera™ MRI
ICD
• BioTronik ProMRI® ICD
Fig 20 : AICD with characteristic defibrillation
coils
Subcutaneous ICDs (S-ICD)

no transvenous leads, no contact
with the heart

pulse generator: along the left
lateral chest wall

subcutaneous electrode: in the left
parasternal position

MR conditional:
•
no evidence of device malfunction,
depletion of batteries, interaction
with programmed parameters or
tissue injury by potential
overheating in a study of 19
examinations (15 patients) *
(Petr Neuzil, European Congress of Radiology (ECR) 2014:
Abstract B-0297)

currently only one manufacturer:
•
Cameroon Health/ Boston Scientific
* NB: two patients were re-scanned
due complaints of heating over the
can during lumbar scans.
Changing MR settings reduced
heating sensation.
Fig 21: Subcutaneous ICD on CXR
Implantable loop recorders (ILR)
 no lead wires or large loops
 MR Conditional: device memory/ECG recording will be
inaccurate in the presence of a strong magnetic field
 may need to warn patient about tugging sensation
 radiographic appearance: cricket bat/ rectangular/ “USB
stick ”
Fig 22: ILR on CXR. this model shows a “USB stick”
appearance
Permanent leadless pacemakers
 permanent leadless pacemakers are NOT
MR compatible
 no lead is required
 not detectable on physical examination
 Pearl: may not be detectable with metal detector
 it is recommended that patients with leadless
pacemakers avoid MRI
Fig 23 : Medtronic Leadless Micra™ Pacemaker
Abandoned leads
 an abandoned lead is a lead left
behind due to fracture,
insulation breaks, dislodgement
and other failures
 it is disconnected from the pulse
generator
 Langman DA, et al 2011
showed that abandoned leads
exhibited greater lead tip
heating compared with
pacemaker-attached leads.
 pearl: abandoned intracardiac
pacing leads may pose
increased risk for patients
undergoing MRI, even if the
lead itself is MR compatible
Fig 24 : This patient had old leads in the (L)
hemithorax which were abandoned at the
end of the lead lifespan. A new pulse
generator and leads were subsequently
implanted.
Langman DA, et al. Pacemaker lead tip heating in abandoned and pacemaker-attached leads at 15 Tesla MRI. J Magn Reson Imaging.
2011;33:426-431
Steps enabling the safe scanning of MR
conditional CIEDs
 an algorithm has been developed in our
institution to ensure that patients with CIEDs
can be MR scanned safely
 the first two steps of this algorithm include a
mechanism in-built into the hospital
computerized physician order entry (CPOE)
system
 the requesting clinicians also are required to
complete a set of checklists in the course of the
patient’s care pathway
FIG 25: ALGORITHM FOR THE MR SCANNING OF PATIENTS WITH CIEDS
CPOE question: Does the patient have a CIED?
CIED: Cardiovascular Implantable Electronic Device
NB: If the patient has retained leads or external pacing wires, the
scan cannot proceed
Yes
CPOE question: Is this device
MRI conditional?
Unsure
No
STOP : Consider other
imaging modality or postpone
Contact: Clinical Measurements
Unit (CMU) to verify.
On Public Holiday or after office
hours, call device vendor directly
Yes
NB: If a Cardiac radiologist
is on leave, or unavailable
for vetting, please contact
Cardiology registrar-on-call.
Pre scan: The request must be approved by a Cardiac
Radiologist. CMU to reprogram and check device before
scan. On weekend/PH please contact vendor directly.
How to ensure: *Checklist part A1
Yes
Conditions
not met
Conditions not
met
Pre scan: ACLS certified Doctor must be present
to monitor patient.
How to ensure: *Checklist part A2
Yes
During scan: MRI technician must:
Ensure patient is monitored (Checklist B1) AND
radiological conditions for scanning are met
(*Checklist B2)
Yes
After scan: Device must be reprogrammed and
checked by trained health professional
How to ensure: *Checklist part C
*NB: the checklist is not
included in this presentation
Preventing inadvertent scanning
 another algorithm was developed in our
institution to prevent inadvertent scanning
of patients with CIEDs (including MR
conditional devices)
 it includes three fundamental actions that
occur before a patient is scanned:
 checking the clinical history
 checking for a prior chest radiograph (CXR)
 sweeping the patient with a metal detector
FIG 26: ALGORITHM FOR THE PREVENTION OF INADVERTENT SCANNING
OF PATIENTS WITH CIEDS (both MR conditional and non MR compatible)
Patient arrives for scan. MRI
radiographer: 1) Checks request
form for history of pacemaker
2) Verbally asks that patient has
no pacemaker
Pacemaker
found
No history of
Pacemaker
Check for prior CXR on PACs
AND sweep patient with
Ferromagnetic metal detector
Pacemaker
found
Sweep positive
No CXR available
STOP 
MR cancelled
(reschedule after model
identified, MR
compatibility determined)
Obtain CXR
Pacemaker
found
No pacemaker
Sweep negative,
CXR negative, or
No CXR available
GO 
Patient enters MR
scan room
Steps if inadvertent scanning occurs
 a contingency plan exists in our institution
should an inadvertent MR scan of a
patient with a non-MR compatible CIED
occur
FIG 27: ALGORITHM FOR INADVERTENT SCAN OF PATIENTS WITH CIED
Inadvertent scan has occurred
During office hours (0800-1730 hrs)
MRI radiographer will first ensure
the patient’s parameters are
stable:
NIBP, Pulse Ox, ECG monitor
After office hours (1730-0800 hrs)
Accompanying nursing staff will
first ensure the patient’s
parameters are stable: NIBP,
Pulse Ox, ECG monitor
Immediately Call
Immediately Call
Staff-radiologist on duty to
review the patient to make sure
the patient is stable
On-call radiology trainee will
review the patient to ensure the
patient is stable.
Call
Immediately Call
Ward Dr in Charge will be called to
review patient. CMU to review the
patient and CIED settings.
URGENT REFERRAL to be made
to Cardiology.
MRI radiographer
to complete
Ward doctor in charge to review
the patient and place the patient
on telemetry, pulse oximetry,
NIBP monitoring until such time
that a trained health professional
can review the CIED device.
URGENT REFERRAL made to
Cardiology doctor on call
MRI radiographer
to complete
In BOTH EVENTS a clinical incident form should be
raised within 12 hours so that the event may be
reviewed.
Acknowledgements
 Medtronic, St Jude Medical, Boston Scientific, Biotronik for
the use of their images and figures. Permissions have been
obtained for use
 CIED guideline development taskforce (GDT) 2014, Changi
General Hospital:
Dr Andrew Tan, Chair, Dr Angeline Poh, Vice chair, Dr LeRoy Chong,
MRI safety chair, Dr Charlene Liew, Secretary, Dr Colin Yeo,
Department of Cardiology, Dr Kelvin Wong, Department of Cardiology,
Ms Charmaine Chen, Ms Lee Lee Lian, Ms Lee Leng Leng, Head,
Clinical Measurements Unit
 Dr Colin Yeo, Department of cardiology, for figures 21 and 24
Author Contact Information
 Poh Pei Ghim
 [email protected]
 +65 91376083
 Address:
Dept of Diagnostic Radiology,
Level B1, Changi General Hospital,
2 Simei St 3,
Singapore 529889