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MRI Safety
Contraindications
 
 
 
  • Contraindications
 
Radiology Safety Open this link in a new window
'Safety' in MRI News (65) and in MRI Resources (43) 
Contraindications 

The principal contraindications of the MRI procedure are mostly related to the presence of metallic implants in a patient. The risks of MRI scans increase with the used field strength. In general, implants are becoming increasingly MR safe and an individual evaluation is carried out for each case.


MRI Safety Guidance
Some patients should not be examined in MRI machines, or come closer than the 5 Gauss line to the system.
Absolute Contraindications for the MRI scan:
electronically, magnetically, and mechanically activated implants
ferromagnetic or electronically operated active devices like automatic cardioverter defibrillators
cardiac pacemakers
metallic splinters in the eye
ferromagnetic haemostatic clips in the central nervous system (CNS)
Patients with absolute contraindications should not be examined or only with special MRI safety precautions. Patients with an implanted cardiac pacemaker have been scanned on rare occasions, but pacemakers are generally considered an absolute contraindication. Relative contraindications may pose a relative hazard, and the type and location of an implant should be assessed prior to the MRI examination.
Relative Contraindications for the MRI scan:
cochlear implants
other pacemakers, e.g. for the carotid sinus
insulin pumps and nerve stimulators
lead wires or similar wires (MRI Safety risk)
prosthetic heart valves (in high fields, if dehiscence is suspected)
haemostatic clips (body)
non-ferromagnetic stapedial implants
Osteosynthesis material is usually anchored so well in the patients that no untoward effect will result. Another effect on metal parts in the patient's body is the heating of these parts through induction. In addition, image quality may be severely degraded. The presence of other metallic implants such as surgical clips etc. should be made known to the MRI operators. Most of these materials are non-magnetic, but if magnetic, they can pose a hazard.
See also MRI safety, Pregnancy, Claustrophobia and Tattoos.


• View the DATABASE results for 'Contraindications' (11).Open this link in a new window

 
Further Reading:
  Basics:
MRI in Patients with Implanted Devices: Current Controversies
Monday, 1 August 2016   by www.acc.org    
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
Physics of MRI Safety
   by www.aapm.org    
FDA Releases New Guidance On Establishing Safety, Compatibility Of Passive Implants In MR Environments
Tuesday, 16 December 2014   by www.meddeviceonline.com    
  News & More:
Making Pacemakers and ICDs MRI-Safe
Wednesday, 8 March 2017   by www.mddionline.com    
Implantable Infusion Pumps in the Magnetic Resonance (MR) Environment: FDA Safety Communication - Important Safety Precautions
Wednesday, 11 January 2017   by www.fda.gov    
Women with permanent make-up tattoos suffer horrific facial burns after going in for MRI scans - which create an electric current in the ink
Monday, 4 July 2016   by www.dailymail.co.uk    
Positive diagnosis for neural therapeutic implants
Tuesday, 19 April 2016   by medicalxpress.com    
Codman Neuro develops new MRI-resistant programmable valve for treatment of hydrocephalus
Tuesday, 22 September 2015   by www.news-medical.net    
Cardiac Pacemaker 

A pacemaker is a device for internal or external battery-operated cardiac pacing to overcome cardiac arrhythmias or heart block. All implanted electronic devices are susceptible to the electromagnetic fields used in magnetic resonance imaging. Therefore, the main magnetic field, the gradient field, and the radio frequency (RF) field are potential hazards for cardiac pacemaker patients.
The pacemaker's susceptibility to static field and its critical role in life support have warranted special consideration. The static magnetic field applies force to magnetic materials. This force and torque effects rise linearly with the field strength of the MRI machines. Both, RF fields and pulsed gradients can induce voltages in circuits or on the pacing lead, which will heat up the tissue around e.g. the lead tip, with a potential risk of thermal injury.
Regulations for pacemakers provide that they have to switch to the magnet mode in static magnetic fields above 1.0 mT. In MR imaging, the gradient and RF fields may mimic signals from the heart with inhibition or fast pacing of the heart. In the magnet mode, most of the current pacemakers will pace with a fix pulse rate because they do not accept the heartsignals. However, the state of an implanted pacemaker will be unpredictable inside a strong magnetic field. Transcutaneous controller adjustment of pacing rate is a feature of many units. Some achieve this control using switches activated by the external application of a magnet to open/close the switch. Others use rotation of an external magnet to turn internal controls. The fringe field around the MRI magnet can activate such switches or controls. Such activations are a safety risk.
Areas with fields higher than 0.5 mT (5 Gauss Limit) commonly have restricted access and/or are posted as a safety risk to persons with pacemakers.


MRI Safety Guidance
A Cardiac pacemaker is because the risks, under normal circumstances an absolute contraindication for MRI procedures.
Nevertheless, with special precaution the risks can be lowered. Reprogramming the pacemaker to an asynchronous mode with fix pacing rate or turning off will reduce the risk of fast pacing or inhibition. Reducing the SAR value reduces the potential MRI risks of heating. For MRI scans of the head and the lower extremities, tissue heating also seems to be a smaller problem. If a transmit receive coil is used to scan the head or the feet, the cardiac pacemaker is outside the sending coil and possible heating is very limited.


• View the DATABASE results for 'Cardiac Pacemaker' (6).Open this link in a new window

 
Further Reading:
  Basics:
MRI in Patients with Implanted Devices: Current Controversies
Monday, 1 August 2016   by www.acc.org    
Magnetic resonance imaging in patients with cardiac pacemakers: era of MR Conditional designs
Thursday, 27 October 2011   by 7thspace.com    
  News & More:
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
Making Pacemakers and ICDs MRI-Safe
Wednesday, 8 March 2017   by www.mddionline.com    
Patients with standard pacemakers, ICDs may safely undergo MRIs
Friday, 24 February 2017   by www.cardiovascularbusiness.com    
Biotronik's new Ilivia ICDs and CRT-Ds with MRI AutoDetect receives CE approval
Wednesday, 3 February 2016   by www.pharmabiz.com    
ITOCHU Named the Exclusive Distributor for ViewRay's MRI-Guided Radiation Therapy System in Japan
Thursday, 22 January 2015   by www.prnewswire.com    
Medtronic Gets Japanese Approval, Launches Evera MRI
Monday, 10 November 2014   by www.pcbdesign007.com    
Modern Implantable Heart Devices Safe For Use In MRI Scans
Wednesday, 16 March 2005   by www.sciencedaily.com    
Active Device 

The term 'active' refers to any medical device that can only serve its intended use with the supply of power by any means including, but not limited to line, battery, or gas power. Examples of active devices include ventilators, pacemakers, and patient monitoring devices.

• View the DATABASE results for 'Active Device' (4).Open this link in a new window

 
Further Reading:
  News & More:
Modern Implantable Heart Devices Safe For Use In MRI Scans
Wednesday, 16 March 2005   by www.sciencedaily.com    
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
Implants 

Implants that involve magnets such as magnetic sphincters, stoma plugs, dental implants, etc., can be demagnetized by the MRI device. They should be removed prior to the examination.


MRI Safety Guidance
A particular danger is presented by small metallic surgical implants. Haemostatic or other clips in the CNS can move in their position. Dislocation by magnetic attraction or torque presents a risk in MRI examinations. There is a minimal risk in other parts of the body, because after the healing phase of six to eight weeks, fibrosis and encasement of the clip help to keep it in a stable position.
The label stainless steel is not a guarantee for non-ferromagnetic steel.
See also Cardiac Pacemaker and MRI Safety.

• View the NEWS results for 'Implants' (2).Open this link in a new window.

• View the DATABASE results for 'Implants' (13).Open this link in a new window

 
Further Reading:
  Basics:
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
FDA Releases New Guidance On Establishing Safety, Compatibility Of Passive Implants In MR Environments
Tuesday, 16 December 2014   by www.meddeviceonline.com    
Pain, magnet displacement in MRI in patients with cochlear implants
Thursday, 20 November 2014   by medicalxpress.com    
  News & More:
On the estimation of the worst-case implant-induced RF-heating in multi-channel MRI.
Thursday, 2 March 2017   by www.ncbi.nlm.nih.gov    
Positive diagnosis for neural therapeutic implants
Tuesday, 19 April 2016   by medicalxpress.com    
ITOCHU Named the Exclusive Distributor for ViewRay's MRI-Guided Radiation Therapy System in Japan
Thursday, 22 January 2015   by www.prnewswire.com    
BIOTRONIK Concludes Enrollment in Phase C of its ProMRI ICD Study
Wednesday, 21 January 2015   by www.biotronik.com    
FDA grants PMA-Supplement approval for Flowonix Medical's Prometra II system
Tuesday, 20 January 2015   by www.medicaldevice-network.com    
FDA Approves MED-EL's SYNCHRONY Cochlear Implant
Friday, 23 January 2015   by www.businesswire.com    
Foreign Bodies 


MRI Safety Guidance
Occult incorporated ferromagnetic foreign bodies are dangerous, in particular those close to the eyes. The patient's history may help because many patients do not remember such accidents. In case of doubt, X-rays should be taken prior to MR imaging.

• View the DATABASE results for 'Foreign Bodies' (3).Open this link in a new window

Nephrogenic Systemic Fibrosis 

(NSF) Nephrogenic systemic fibrosis is a rare and highly debilitating disorder that involves extensive thickening and hardening of the skin with fibrotic nodules and plaques.
MRI contrast media have very low side effects, but accumulating data indicate that gadolinium-based contrast agents increase the risk for the development of NSF among patients with severe renal insufficiency or renal dysfunction due to the hepato-renal syndrome or in the perioperative liver transplantation period.
Due to this reason, gadolinium contrast agents are now considered contraindicated in patients with an estimated glomerular filtration rate fewer than 30 mL/min/1.73m2. In these patients, avoid use of gadolinium-based contrast agents unless the diagnostic information is essential and not available with non-contrast enhanced magnetic resonance imaging (MRI).

Recognized or possibly associated factors for NSF:
Severe renal failure;
high dose of gadolinium chelate;
high dose of erythropoietin;
high serum phosphate levels;
high serum calcium levels;
major surgery, infection, vascular event;
history of hypothyroidism;
metabolic acidosis.
When administering a gadolinium-based contrast agent, do not exceed the recommended dose and allow a sufficient period of time for elimination of the contrast medium from the body prior to any readminstration. Screen all patients for renal dysfunction by obtaining a history and/or laboratory tests.
See also Contrast Medium, Adverse Reaction, MRI Risks, MRI Safety, Ionic Intravenous Contrast Agents, Nonionic Intravenous Contrast Agents, and Contraindications.

• View the NEWS results for 'Nephrogenic Systemic Fibrosis' (8).Open this link in a new window.

• View the DATABASE results for 'Nephrogenic Systemic Fibrosis' (13).Open this link in a new window

 
Further Reading:
  Basics:
Important Drug Warning for Gadolinium-Based Contrast Agents
Wednesday, 12 September 2007   by www.ismrm.org    
European Medicines Agency makes recommendations to minimise risk of nephrogenic systemic fibrosis with gadolinium-containing contrast agents
Friday, 20 November 2009   by www.ema.europa.eu    
Gadolinium-based MR Contrast Agents and Nephrogenic Systemic Fibrosis
Thursday, 1 March 2007   by radiology.rsna.org    
NSF-Active and NSF-Inert Species of Gadolinium: Mechanistic and Clinical Implications
Friday, 27 June 2008   by www.ajronline.org    
  News & More:
Questions and Answers on Gadolinium-Based Contrast Agents
Friday, 9 January 2009   by www.fda.gov    
  Safety Guidance top
Radiology Safety Open this link in a new window
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- Oscar Wilde
 
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