Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5‐T MR system

Shellock, Frank G.; Morisoli, Stacy M.

doi:10.1002/jmri.1880040521

Cited by 53 publications

(35 citation statements)

References 17 publications

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“…[3][4][5][6][7][8][9][10][11] However, burn accidents caused by MR procedures have been reported. [12][13][14] The mechanism of RF irradiation-induced heating of human body implants is complicated and in‰uenced by quality of material and shape of the implant, body weight and height, electrical properties of various internal organs, thermoregulatory reaction, blood ‰ow, and other parameters.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of RF Heating due to Various Implants during MR Procedures

et al. 2011

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We evaluated radiofrequency (RF) heating of various implants embedded in a gel phantom during magnetic resonance (MR) procedures. We examined the dependence of RF heating on variation in speciˆc absorption rate (SAR) and angle between the implant and the static magneticˆeld (B 0 ) and on the displacement of the phantom in the irradiation coil using a 1.5-tesla MR system, and we compared the in‰uence of RF heating on the same implant using a 3.0T MR system.Our results support the occurrence of RF heating of implants made of non-magnetizing metal. We observed greater RF heating when the implant was set parallel to B 0 , embedded at a shallower depth, and placed at the center of the RF irradiation coil. We also conˆrmed that the rise in temperature was proportionate to the increase in SAR. We considered the diŠerence in temperature elevation on depth of embedding to re‰ect the skin-depth eŠect of RF intensity for both the 1.5-and 3.0-T MR systems.

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Section: Introductionmentioning

confidence: 99%

Evaluation of RF Heating due to Various Implants during MR Procedures

et al. 2011

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“…Nevertheless, the reported force of implants in [27] provides a good reference. This study found that forces above 1 gF can be considered as high in terms of safety because the end effector of the actuated robot may come in contact with critical tissues during surgery.…”

Section: Discussionmentioning

confidence: 99%

Quantification of Force and Torque Applied by a High-Field Magnetic Resonance Imaging System on an Ultrasonic Motor for MRI-Guided Robot-Assisted Interventions

2017

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Abstract:The risk of accidental dislodgement of robot-operated surgical mechanisms can lead to morbidity or mortality. The force and torque applied by a 3.0-tesla scanner on an ultrasonic motor are not fully known. The force and torque may displace the motor, which is not fully magnetic resonance imaging (MRI)-compatible but can be safely used in MR environments. A suspension apparatus was designed to measure the angles of deflection and rotation applied to the motor by MR magnetic fields. Three orientations and two power states of the motor were assessed inside the MR bore. The displacement force and torque were measured at eight locations with respect to the bore. The displacement force on the motor from 10 cm outside the magnet bore to 20 cm inside the bore ranged from 3 to 7 gF. The experimental measurements are in agreement with the theoretical values. Running the motor altered the force by 1 gF. The force does not significantly change when the MRI scanner is on. Considerable displacement force is applied to the motor, and no deflection torque is observed. Quantified values can be used to solve dynamic equations for robotic mechanisms intended for MRI-guided operations.

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“…Many heart valve prostheses and annuloplasty rings have been evaluated to determine whether they are acceptable for patients undergoing MR examinations with scanners operating at 1.5 T or less. 3,43,48,49,51 Of these, several displayed measurable yet relatively minor magnetic field interactions in relation to the static magnetic fields of the MR systems used for testing. The forces exerted on these valves and rings are less than the forces exerted by gravity and considerably less than those exerted by the beating heart and resultant pulsatile blood flow (Ϸ7.2 N).…”

Section: Prosthetic Heart Valves Annuloplasty Rings and Sternal Sutmentioning

confidence: 99%

“…These studies indicated that temperature increases are relatively minor, with studies reporting heating ranging from 0°C to 0.8°C. 48,49,51,54,55 As with vascular stents, any heating is likely to be somewhat dissipated by flowing blood. Although there is a theoretical possibility of an electromagnetic interaction with a heart valve that contains metal in the disk or leaflet that could inhibit opening and closing of the mechanical heart valve prosthesis (referred to as the Lenz effect), this has never been demonstrated experimentally or reported clinically.…”

Section: Prosthetic Heart Valves Annuloplasty Rings and Sternal Sutmentioning

confidence: 99%

Safety of Magnetic Resonance Imaging in Patients With Cardiovascular Devices

Levine¹,

Gomes

Arai³

et al. 2007

Circulation

440

119

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Abstract-Advances in magnetic resonance (MR) imaging over the past 2 decades have led to MR becoming an increasingly attractive imaging modality. With the growing number of patients treated with permanent implanted or temporary cardiovascular devices, it is becoming ever more important to clarify safety issues in regard to the performance of MR examinations in patients with these devices. Extensive, although not complete, ex vivo, animal, and clinical data are available from which to generate recommendations regarding the safe performance of MR examination in patients with cardiovascular devices, as well as to ascertain caveats and contraindications regarding MR examination for such patients. Safe MR imaging involves a careful initial patient screening, accurate determination of the permanent implanted or temporary cardiovascular device and its properties, a thoughtful analysis of the risks and benefits of performing the examination at that time, and, when indicated, appropriate physician management and supervision. This scientific statement is intended to summarize and clarify issues regarding the safety of MR imaging in patients with cardiovascular devices.

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Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5‐T MR system

Cited by 53 publications

References 17 publications

Evaluation of RF Heating due to Various Implants during MR Procedures

Evaluation of RF Heating due to Various Implants during MR Procedures

Quantification of Force and Torque Applied by a High-Field Magnetic Resonance Imaging System on an Ultrasonic Motor for MRI-Guided Robot-Assisted Interventions

Safety of Magnetic Resonance Imaging in Patients With Cardiovascular Devices

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