Frank G. Shellock, PhD #{149}Julie Swengros Curtis, MD

MR Imaging and Biomedical Implants,Materials, and Devices: An Updated Review’

541

Magnetic Resonance Imaging

Certain ferromagnetic metallic im-plants, materials, and devices are re-garded as contraindications for mag-netic resonance imaging, primarilybecause of the risks associated with

their movement or dislodgment.More than 40 publications have re-ported the ferromagnetic qualities of261 different metallic objects (aneu-rysm and hemostatic clips, 32; carotidartery vascular clamps, five; dentaldevices or materials, 16; heart valveprostheses, 29; intravascular coils,filters, and stents, 14; ocular im-plants, 12; orthopedic implants, mate-rials, and devices, 15; otologic im-plants, 56; pellets and bullets, 23;penile implants, nine; vascular accessports, 33; and miscellaneous, 17) onthe basis of measurements of defiec-lion forces or attraction during expo-sure to static magnetic fields atstrengths of 0.147-4.7 T. The resultsof these studies are listed with re-spect to the specific object tested, thematerial used to construct the object(if known), whether or not the objectwas deflected or moved during expo-sure to the static magnetic field, and

the highest static magnetic fieldstrength used for testing the object.

Index term: Magnetic resonance (MR), safety

Radiology 1991; 180:541-550

I From the Tower Musculoskeletal ImagingCenter, Department of Diagnostic Radiology,Cedars-Sinai Medical Center, 8700 Beverly Blvd.Los Angeles, CA 90048 (F.G.S.,J.S.C.); and De-partment of Diagnostic Radiology, University ofCalifornia, Los Angeles, School of Medicine, LosAngeles u.S.C.). Received February 21, 1991; re-vision requested March 25; revision receivedApril 5; accepted April 8. Supported in part by

PHS grant 1 RO1 CA44014-03 from the NationalCancer Institute, National Institutes of Health.Address reprint requests to F.G.S.

©RSNA,1991

M AGNETIC resonance (MR) imag-ing may be contrarndicated in

a patient with a ferromagnetic metal-lic implant, material, or device prima-rily because of the risk associated withmovement and/or dislodgment of theobject as well as other possible haz-ards, including the induction of elec-trical current, excessive heating, andmisinterpretation of an artifact, pro-duced by the presence of the object,as an abnormality (1-58). The poten-tial for MR imaging to injure patientsby inducing electric currents in con-ductive metallic materials or devicessuch as gating leads, unused surfacecoils, halo vests, or improperly usedphysiologic monitors has been previ-ously discussed (15,49,54), and recom-mendations to protect the patientduring MR imaging have been pre-sented (49). Temperature elevationsassociated with MR imaging of metal-lic implants, materials, and devices(with the exception of monitoringequipment, surface coils, or other ex-ternally applied equipment) havebeen studied, and there appears to beno significant hazard related to thetemperature changes that have beenmeasured (7,16,17). The type and ex-tent of various artifacts caused by me-taffic implants, materials, and deviceshave also been described and are typi-cally well recognized on MR images(9,10,13,18-21,38,40,46,52).

Numerous studies have assessedthe ferromagnetic qualities of variousmetallic implants, materials, or de-vices by measuring deflection forcesor movements associated with thestatic magnetic fields used for MR im-aging (1-14,17,21-30,33,35-43,47,51,53,55; Becker RD. written communica-tion, 1989). In general, these investi-gations have demonstrated that MRimaging may be performed safely inpatients with metaffic implants, mate-nals, or devices if the object is nonfer-romagnetic or is only minimally at-tracted by the static magnetic field inrelation to its in vivo application (ie,

the associated deflection force or at-traction is insufficient to move or dis-lodge the implant or material in situ).

Since prior knowledge of the rela-tive degree of ferromagnetism that aspecific type of metallic implant, ma-terial, or device possesses is essential

for proper screening of patients be-fore MR imaging (15,44,45,54), thearticles pertaining to this topic havebeen reviewed and summarized. TheTable lists data on 261 different im-

plants, materials, and devices thathave been tested for ferromagnetism,whether or not the objects were de-flected or attracted by static magneticfields, and the highest static magneticfield strength (range, 0.147-4.7 T) atwhich the objects were evaluated.

Unless otherwise stated, this article

specifically pertains to the safety as-pects of performing MR imaging in apatient with respect to the ferromag-netic qualities of a metallic implant,material, or device (ie, its attraction to

a magnetic field). Other issues relatedto electrical conductivity, artifact pro-duction, and the like are not dis-cussed in this article.

DISCUSSION

Various factors influence the risk of

performing MR imaging in a patientwith a ferromagnetic implant, mate-rial, or device, including the strengthof the static and gradient magneticfields, the relative degree of ferromag-netism of the object, the mass of theobject, the configuration of the object,the location and orientation of theobject in situ, and the length of timethe object has been in place (9,11,15,33,44,45,49,54). These factors shouldbe carefully considered before sub-jecting a patient with a ferromagneticobject to MR imaging, particularly ifthe object is in a potentially danger-ous area of the body such as near avital neural, vascular, or soft-tissuestructure where movement or dis-

Metallic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposureto Static Magnetic Fields

Metallic Implant, Moveznent/ Highest Field Metallic Implant, Movement/ Highest Field

MateriaL or Device Deflection Strength (F) Reference Material, or Device Deflection Strength (T) Reference

An.iuysm and hen�static clips Carotid artery vascular dampsDowns multiposi- Crutchfield (55); Cod-

tional(17-7PH); man Yes* 1.5 22Sims Surgical, Kindt (55); V. Mueller Yes* 1.5 22Keene, NH Yes 1.44 9 Poppen-Blaylock (SS);

Drake (DM4, DR24); Codman Yes 1.5 22Edward Weck, Tn- Salibi (55); Codman Yes* 1.5 22angLe Park, NJ Yes 1.44 9,29 Selverstone (55); Cod-

Drake (DR16); Edward man Yes* 1.5 22Weck Yes 0.147 9

Drake (301 SS); Ed- Dental devices and materialsward Weck Yes 1.5 11,29 Brace band (55);

Gastrointestinal anas- American Dental,tomosis clip, Auto MissoWa, Mont No 1.5 11Suture SCIA (SS); Brace wire (chromeUnited States Surgi- alloy); Ormco, Sancal, Norwalk, Corns No 1.5 11 Marcos, Calif Yes* 1.5 11

Heifetz (17-7PH); Ed- Castable alloy; Goldenward Weck Yes 1.89 4,42 Dental Products,

Heifetz (Elgiloy); Ed- Golden, Cob Yes* 1.5 55ward Weck No 1.89 4,29,42 Cement-in keeper;

Hemodip no. 10 (316L Solid State Innova-SS); Edward Weck No 1.5 11 tions, Mt Airy, NC Yes* 1.5 55

Hemoclip (Tantalum); Dental amalgam No 1.44 9Edward Weck No 1.5 11 GDP Direct Keeper,

Housepian implant Yes 0.147 9 preformed post;I(app (405 SS); Golden Dental Prod-

V. Mueller Yes 1.89 4,29 ucts Yes� 13 55Kapp curved (404 SS); Keeper, preformed

V. Mueller Yes 1.44 9 post; Parkell Prod-Kapp straight (404 55); ucts, Farmingdale,

V. Mueller Yes 1.44 9 NY Yes� 1.5 9,55Ligadlip, no. 6 (316L Magna-Dent, large

SS); Ethicon, Born- indirect keeper;merville, NJ No 1.5 11 Dental Ventures of

Ligaclip (tantalum); America, YorbaEthicon No 1.5 11 Linda, Calif Yes* 1.5 55

Mayfleld (301 SS); Palladium clad mag-Codman, Randolph, net; Parkell Products Yes 1.5 37Mass Yes 1.5 11 Palladium/palladium

Mayfield (304 SS); keeper; ParkellCodman Yes 1.89 4 Products Yes� 1.5 37

McFadden (301 SS); PalladiunVplatinumCodman Yes 1.5 11,29 casting alloy; Parkell

Olivecrona No 1.44 9 Products Yest 1.5 37Pivot (17-7PH); Permanent crown

V. Mueller Yes 1.89 4 (amalgam); Ormco No 1.5 11Scoville (EN58J); 55 clad magnet; Par-

Downs SurgicaL Dc- kell Products Yes 1.5 37cater, Ga Yes 1.89 4,29 55 keeper; Parkell

Stevens (50-4190, sil- Products Yes* 1.5 37ver alloy) No 0.15 2 Silver point; Union

Sugita (Elgiloy); Broach, New York No 1.5 11Downs Surgical No 1.89 4,29 Titanium clad magnet;

Sundt-Kees (301 SS); Parkell Products Yes 1.5 37Downs Surgical Yes 1.5 11,29

Sundt-Kees Multi-An- Heart valve prosthesesgle (17-7PH); Downs Beall; Coratomic, Indi-

Surgical Yes 1.89 4,29 ana, Penn Yes� 2.35 12Surgidlip, Auto Suture Bjork-Shiley (convexo/

M-93 (SS); United concave); Shiley,States Surgical No 15 11 Irvine, Calif No 1.5 11

Van-angle (17-7PH); Bjork-Shiley (univer-

Codman Yes 1.89 4 saVspherical); Shiley Yes� 1.5 11Van-angle McFadden Bjork-Shiley, model

(MP35N); Codman No 1.89 4,29 MBC; Shiley Yes* 2.35 5Van-angle Micro (17- Bjork-Shiley, model 25

7PM SS); Codman Yes 0.15 2,29 MBRC 11030; Shiley Yes* 2.35 5Van-angle Spring (17- Carpentier-Edwards,

7PM SS); Codman Yes 0.15 2,29 model 2650; Amen-

Yasargil (316 SS); Aes- can Edwards Labo-culap, Burlingame, ratones, Santa Ma,Calif No 1.89 4 Calif Yes* 2.35 5

Yasargil (Phynox);Aesculap No 1.89 4,29 Continued

542 #{149}Radiology August 1991

Metaffic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposureto Static Magnetic Fields (Continued)

Metaffic Implant, Movement/ Highest Field Metallic Implant, Movement/ Highest FieldMaterial, or Device Deflection Strength (F) Refere�we .+� Material, or Device Deflection Strength (‘F) Reference

Carpentier-Edwards Gianturco Bird’s Nest(porcine); American NC ifiter; Cook Yes*$ 1.5 13,24Edwards Laborato- Gianturco emboliza-ties Yes* 2.35 5 tion coil; Cook Yes*S 1.5 13

Hall-Kaster, model Gianturco zig-zag

A7700; Medtronic, stent; Cook Yes*S 1.5 13Minneapolis Yes* 1.5 11 Greenfleld vena cava

Hancock I(porcine); ifiter (55); Medi-Johnson and tech/Boston Scien-Johnson, Anaheim, tific, Watertown,Calif Yes* 1.5 11 Mass Yes*$ 1.5 13,40

Hancock H (porcine); Greenfleld vena cava

Johnson and ifiter (titanium al-Johnson Yes* 1.5 11 by); Medi-tech/Bos-

Hancock extracorpo- ton Scientific No 13 13real, model 242R; Gunther NC ifiter;Johnson and William Cook, Eu-Johnson Yes* 2.35 5 rope Yes*t 1.5 13

Hancock extracorpo- Maas helical endovas-real model M 4365- cular stent; Medin-33; Johnson and vent No 4.7 13Johnson Yes* 2.35 5 Maas helical NC ifiter;

Hancock Vascor, Medinvent, Lau-model 505; Johnson sanne, Switzerland No 4.7 13and Johnson No 2.35 5 Mobin-Uddin P/C/

lonescu-Shiley; Urn- umbrella ifiter;versallSM Yes* 2.35 5 American Edwards No 4.7 13

Lillehi-Kaster, model Palmaz endovascular3005; Medical, Inver stent; Ethicon Yes*f 1.5 13

Grove Heights, Retrievable NC ifiter;

Minn Yes* 2.35 12 Thomas JeffersonLifiehi-Kaster, model University, Philadel-

5009; Medical Yes* 2.35 5 phia Yes*S 1.5 13Medtronic Hall; Strecker stent (tanta-

Medtronic Yes* 2.35 5 lum); Medi-teclt/

Medtronic Hall, model Boston Scientific No 1.5 25,34A7700-D-16;Medtronic Yes* 2.35 5 Ocular implants

Omnicarbon, model Fatio eyelid spring/3523T029; Medical Yes* 2.35 5 wire Yes 1.5 23

Omniscience, model iztraocularlens im-6522; Medical Yes* 2.35 5 plant; Binkhorst,

Smeloff-Cutter; Cutter iridocapsular lens;Laboratories, Berke- platinum-fridiumley, Calif Yes* 2.35 11 loop No 1.5 3

Starr-Edwards, model Intraocular lens ins-1260; American Ed- plant; Binkhorst,wards Laboratories Yes* 2.35 12 iridocapsular lens;

Starr-Edwards, model platinum loop No 1.0 32320; American Ed- Intraocularlens ins-wards Laboratories Yes* 2.35 12 plant; Binkhorst,

Starr-Edwards, model iridocapsular lens;2400; American Ed- titanium loop No 1.0 3wards Laboratories No 1.5 11 Intraocularlens im-

Starr-Edwards, model plant; Worst, plati-Pre 6000; American num clip lens No 1.0 3Edwards Laborato- Retinal tack (303 55);ties Yes 2.35 12 Bascom Palmer Eye

Starr-Edwards, model Institute No 1.5 276520; American Ed- Retinal tack (titaniumwards Laboratories Yes* 2.35 5 alloy); Coopervision,

St. Jude; St. Jude Med- Irvine, Calif No 1.5 27,41ical, St. Paul No 1.5 11 Retinal tack(303 SS);

St.Jude, modelA 101; Duke University No 1.5 27St. Jude Medical Yes* 2.35 5 Retinal tack (cobalt/

St.Jude, modelM 101; nickel); Grieshaber,St.Jude Medical Yes* 2.35 5 Fallsington, Penn No 1.5 41

Retinal tack, Norton

Infravascular coils, filters, staple (platinum/and stents rhodium); Norton No 1.5 27

Amplatz NC ifiter; Retinal tack (alumi-Cook, Bloomington, num textraoxide);md No 4.7 13 Ruby No 1.5 27

Cragg nitinol spiralifiter No 4.7 13 Continued

Volume 180 #{149}Number 2 Radiology #{149}543

Metallic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposure

to Static Magnetic Fields (Continued)

Metallic Implant, Movement! Highest Field Metallic Implant, Movement/ Highest FieldMateriaL or Device Deflection Strength (1’) Reference Material, or Device Deflection Strength (‘1’) Reference

Retinal tack (SS-mar- House-type wire loop

tensitic); Western stapes prosthesisEuropean Yes 1.5 27 (316L SS); Richards

Medical No 1.5 26,53Orthopedic implants, House-type SS piston

materials, and and wire (ASTM-devices 318-76 grade 2SS);

AML femoral compo- Xomed-Treace (Bris-nent bipolar hip tol-Myers, Squibb) No 1.5 26prosthesis; Zimmer, House wire (tanta-Warsaw, md No 1.5 11 lum); Otomed No 0.5 36

Cervical wire, 20 House wire (SS);gauge (316L SS) No 0.3 35 Otomed No 0.5 36

Cotrel rods with McGee piston stapeshooks (316L 55) No 0.3 35 prosthesis (316L SS);

Druninsond wire Richards Medical No 1.5 26,53(316L SS) No 0.3 35 McGee piston stapes

Drr, device for trans- prosthesis (plati-verse traction (316L num/316L 55); Rich-SS) No 0.3 35 ards Medical No 1.5 26,53

Harrington compres- McGee piston stapession rod with hooks prosthesis (plati-

and nuts (316L SS) No 0.3 35 num/Cr1�Ni4 55);Harrington distraction Richards Medical

rod with hooks (recalled by manu-(316L SS) No 0.3 35 facturer) Yes 1.5 53

Harris hip prosthesis; McGee shepherd’sZimmer No 1.5 11 crook stapes pros-

Jewett nail; Zimmer No 1.5 11 thesis (316L 55);Kirschner intermedul- Richards Medical No 1.5 26

lar)r rod; Kirschner Plasti-pore pistonMedical, Timonium, (316L SS/plasti-poreMd No 1.5 11 material); Richards

ss mesh; Zinsmer No 1.5 11 Medical No 1.5 26,53SS plate; Zimmer No 1.5 11 Platinum ribbon loopSS screw; Zimmer No 1.5 11 stapes prosthesisSS wire; Zinsmer No 1.5 11 (platinum); RichardsZielke rod with screw, Medical No 1.5 26

washer, and nut Reuter bObbin ventila-(316L SS) No 0.3 35 tion tube (316L 55);

Richards Medical No 1.5 26

Otologic Implants Richards bucket han-Austin Tytan piston die stapes prosthesis

(titanium); Treace (316L SS); RichardsMedical, Nashville No 1.5 26 Medical No 1.5 26,53

Berger “V” bobbin Richards platinumventilation tube (ti- Teflon piston, 0.6tanium); Richards mm (Teflon, plati-Medical, Memphis No 1.5 26 num); Richards

Cochlear implant; 3M/ Medical No 1.5 53House Yes 0.6 8 Richards platinum

Cochlear implant; 3M/ Teflon piston, 0.8Vienna Yes 0.6 8 mm (Teflon, plati-

Cochlear implant, Nu- num); Richardscleus Mini 22-chan- Medical No 1.5 53nel Cochlear, En- Richards piston stapesgelwood, Cob Yes 1.5 53 prosthesis (plati-

Cody tack No 0.6 8 nuni/fluoroplastic);Ehmke hook stapes Richards Medical No 1.5 26

prosthesis (plati- Richards shepherd’snum); Richards crook (platinum);

Medical No 1.5 26 Richards Medical No 0.5 36Fisch piston (Teflon, Richards Teflon piston

55); Richards Medi- (Teflon); Richardscal No 1.5 53 Medical No 1.5 53

House single loop Robinson-Moon-Lippy(ASTM-318-76 grade offset stapes pros-2 SS); Storz, St. Louis No 1.5 26 thesis (ASTM-318-76

House single loop grade 2 SS); Storz No 1.5 26(tantalum); Storz No 1.5 26 Robinson-Moon offset

House double loop stapes prosthesis(tantalum); Storz No 1.5 26 (ASTM-318-76 grade

House double loop 2 55); Storz No 1.5 26(ASTM-318-76 grade2 SS); Storz No 1.5 26 Continued

544 #{149}Radiology August 1991

Metallic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposure

to Static Magnetic Fields (Continued)

Metallic Implant, Movement! Highest Field Metallic Implant, Movement/ Highest FieldMaterial, or Device Deflection Strength (1) Referen� #{149} Material, or Device Deflection Strength (‘F) Reference

Robinson incus re- Tantalum wire loopplacement prosthe- stapes prosthesis515 (ASTM-318.76 (tantalum); Richardsgrade 2 55); Storz No 1.5 26 MediCal No 1.5 26,53

Robinson stapes pros- Id-platinum piston

thesis (ASTM-318-76 (platinum); Xomed-grade 2 SS); Storz No 1.5 26 Treace No 1.5 26

Ronis piston stapes Total ossicular replace-prosthesis (316L SS/ ment prosthesisfluoroplastic); Rich- (TORY) (316L SS);ards Medical No 13 26 Richards Medical No 1.5 53

Schea cup piston Trapeze ribbon loopstapes prosthesis stapes prosthesis(platinunVfluoro- (platinum); Richardsplastic); Richards Medical No 1.5 26Medical No 1.5 26,53 Williams microclip

Schea malleus attach- (316L SS); Richardsment piston (Tef- Medical No 1.5 26Ion); Richards Medi- Xomed stapes (ASTM-cal No 1.5 53 318-76 grade 2 SS;

Schea SS and Teflon Xomed-Treace No 1.5 26wire prosthesis (Tel-ion, 316 L 55); Rich- Pellets and bulletsards Medical No 1.5 53 BB’s; Daisy Yes 15 15

Scheer piston stapes BB’s; Crosman Yes 1.5 15prosthesis (316L 55/ Bullet, 0.380 inch (cop-fluoroplastic); Rich- �, plastic, lead);ards Medical No 1.5 26 Glaser No 1.5 33

Scheer piston (Teflon, BUllet, 0.44 Inch (ref.316L 55); RichardS ion, bronze); NorthMedical No 1.5 53 � ordnance No 13 33

Schuknecht Gelfoam BUllet, 7.62 x 39mmand wire prosthesis, (copper, steel);Armstrong style Norinco Yes 1.5 33(316L SS); Richards Bullet, 0.357 inch (cop-Medical No 1.5 6 � lead); Cascade No 1.5 33

Schuknecht piston Bullet, 0.357 inchstapes prosthesis (lead); Remington No 1.5 33(316L SS/fluoroplas- BUllet, 0.357 inch (alu-tic); Richards Medi- � lead); Win-cal No 1.5 26 chester No 1.5 33

Schuknecht Tel-wire Bullet, 9 nun (copper,incus attachment lead); Remington No 1.5 33(ASTM-318-76 grade BUllet, 0.380 inch (cop-2 SS); Storz No 15 26,53 � � lead);

Schuknecht Tef-wire Geco Yes 1.5 33malleus attachment Bullet, 0.357 inch(ASTM-318-76 grade � copper,2 SS); Storz No 1.5 26,53 lead); Winchester No 1.5 33

Schuknecht Teflon . BUllet, 0.357 inch (ny.wire piston, 0.6 mm lon,lead); Smith and(Teflon, 316L SS); Wesson No 15 33Richards Medical No 1.5 53 BUllet, � i� (steel,

Schuknecht Teflon lead); Evansvillewire piston, 0.8 mm Ordnance Yes 1.5 33(Teflon, 316L SS); BUllet, 0.357 inch (cop.Richards Medical No 1.5 53

per,lead); Fiocchi No 1.5 33Sheehy incus replace- Bullet, 0.357 inch (cop-

ment (ASTM-318-76 per,lead); Hornady No 1.5 33grade 2 SS); Storz No 1.5 26 BUllet, 9 mm (copper,

Sheehy incus strut lead); Norma Yes 1.5 33(316L SS); Richards Bullet, 0.357 inchMedical No 1.5 53

(bronze, plastic);Sheehy.type incus Patton-Morgan No 15 33

replacement strut BUI1et� 0.357 inch (cop.(Teflon, 316L SS);Richards Medical No 1.5 26 per,lead); Patton-

Silverstein malleus Morgan No 13 33BUllet, 0.45 inch (cop.

clip ventilation tube

(Teflon, 316L SS); Pert lead); Samson No 15 33Richards Medical No 1.5 53 Shot, 12-gauge, size:

00 (copper, lead);Spoon bObbin ventila- Federal No 13 33

lion tube (316L SS);Richards Medical No 15 26 Continued

Volume 180 #{149}Number 2 Radiology #{149}545

Metallic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposureto Static Magnetic Fields (Continued)

Metaffic Implant, Movement,1 Highest Field Metallic Implant, Movement/ Highest FieldMaterial, or Device Deflection Strength (F) Reference Material, or Device Deflection Strength (1) Reference

Shot, 71,4 (lead) No 1.5 33 MRI (Delrin plastic,Shot, 4 (lead) No 1.5 33 silicone); Davol/Sub-Shot, 00 buckshot sidiary of C R Bard No 15 21

(lead) No 1.5 33 Norport-AC (tita-mum); Norfolk Mcd-

Penile implants ical, Skokie, Ill No 1.5 21AMS Malleable 600; Norport-DL (316L SS);

American Medical Norfolk Medical No 1.5 21Systems, Mm- Norport-LS (titanium);netonka, Minn No 1.5 10 Norfolk Medical No 1.5 21

AMS 700 CX Inflat- Norport-LS (316L SS);able; American Mcd- Norfolk Medical No 1.5 21ical Systems No 1.5 10 Norport-LS (polysul-

Flexi-Flate Surgitek; fone); Norfolk Mcdi-

Medical Engineer- cal No 15 21ing, Racine, Wis No 1.5 10 Norport-PT (tita-

Flexi-Rod (standard) mum); Norfolk Mcd-Surgitek; Medical ical No 1.5 21Engineering No 1.5 10 Norport-SP (polysul.

Flexi-Rod II (firm) fone, silicone rubber,

Surgitelc Medical Dacron); NorfolkEngineering No 1.5 10 Medical No 1.5 21

Jonas; Dacomed, Mm- PeriPort (polysulfone,neapolis No 1.5 10 titanium); Infusaid No 1.5 21

Mentor Flexible; Men- Port-a-cath, P.A.S. porttor, Minneapolis No 1.5 10 (titanium); Pharma-

Mentor Inflatable; cia Deltec, St Paul No 1.5 21Mentor No 1.5 10 Port-a-cath, titanium

Omniphase; Dacomed Yes 1.5 10 dual lumen (tita-mum); Pharmacia

Vascular access ports Deltec No 1.5 21Button (polysulfone Port-a-cath, titanium

polymer, silicone); peritoneal(tita-Infusaid, Norwood, nium); PharmaciaMass No 1.5 21 Deltec No 13 21

Dome (titanium); Port-a.cath, titaniumDavol/Subsidiary of venous low-profileC R Bard, Cranston, (titanium); Pharma-RI No 13 21 ciaDeltec No 1.5 21

Dual Microport Port-a-cath, titanium(polysulfone poly- venous (titanium);mer, silicone); Infu- Pharmada Deltec No 1.5 21said No 1.5 21 Port-a-cath, venous

Dual Macroport (316L SS); Pharmada(polysulfone poly- Deltec No 1.5 21mer, silicone); Infu- Q-port (316L 55);said No 1.5 21 Quinton Instrument,

Hickman (316L 55); Seattle Yes* 1.5 21Davol/Subsidiary of S.E.A. (titanium); Har-C R Bard Yes* 1.5 21 bor MediCal Devices,

Hickman, pediatric Boston No 1.5 21(titanium); DavoV Snap-lock (titanium,Subsidiary of C R polysulfone poly-Bard No 1.5 21 mer, silicone); Infu-

Implantofix II said No 1.5 21(polysulfone); Bur- Synchromed, modelron Medical, Bethle- 8500-1 (titanium,hem, Penn No 1.5 21 thermoplastic, sifi-

Infusaid, model 400 cone); Medtronic No 1.5 21(titanium); Infusaid No 1.5 21 Vasport (titanium/flu-

Infusaid, model 600 oropolymer); Gish(titanium); Infusaid No 1.5 21 Biomedical, Santa

Lifeport, model 6013 Ana, Calif No 1.5 21(Deirin plastic);Strato Medical, Bev- Miscellaneouserly, Mass No 1.5 21 Artificial urinary

Lifeport, model 1013 sphincter, AMS 800;(titanium); Strato American MedicalMedical No 1.5 21 Systems No 1.5 11

Macroport (polysul- Cerebral ventricularfone polymer, sill- shunt tube connec-cone); Infusaid No 1.5 21 tor, Accu-flow,

Microport (polysul- straight; Codman No 1.5 11fone polymer, sill-cone); Infusaid No 1.5 21 Continued

546 #{149}Radiology August 1991

to Static Magnetic Fields (Continued)

Movement! Highest FieldDeflection Strength (‘F) Reference

No 1.5 11

No 1.5 11

Yes 0.147 10

1.5 11

1.5 11

Yes*

Yes*

Yes*No

No

No

Yes*

No

No�

No

Yes

Yes*

13 7

1.5 38

1.5 38

1.5 591.44 9

15 30

Becker,

1.5 1989

1.5

1.44

1.44

11

10

10

Metaffic Implants, Materials, and Devices Tested for Movement/Deflection Forces during Exposure

Volume 180 #{149}Number 2 Radiology #{149}547

Metallic Implant,Material, or Device

Cerebral ventricularshunt tube connec-tor, Accu-flow rightangle; Codman

Cerebral ventricularshunt tube connec-tor, Accu-flow,T-connector; Cod-man

Cerebral ventricularshunt tube connec-tor (type unknown)

Contraceptive dia-phragm, All Flex;Ortho Pharmaceuti-cal, Raritan, NJ

Contraceptive dia-phragm, flat springOrtho Pharmaceuti-cal

Contraceptive dia-phragm, Koroflex;Young Drug Prod-ucts, Piscataway, NJ

Forceps (titanium)Hakim valve and

pump

Metallic Implant,Material, or Device

Intrauterine contra-ceptive device, Cop-per 1; Searle Phar-maceuticals, Chicago

Shunt valve, Hotter-type; Holter, Bridge-port, Penn

Shunt valve, Holter-Hausner type;Holter-Hausner,Bridgeport, Penn

Swan-Ganz thermodi-lution catheter;American-EdwardsLaboratories, Irvine,

Tantalum powderTissue expander with

magnetic port;McGhan Medical,Santa Barbara, Calif

Vascular marker,

0-ring washer (302SS); PlC Design,Middlebury, Conn

Movement/ Highest FieldDeflection Strength fl Reference

Note.-”Highest field strength” refers to the highest intensity of static magnetic field in teds that was used for the evaluation of movement or deflectionforces of the various implants, materials, and devices tested. NC = inferior vena cava, SS = stainless steeL Material or materials used to construct the object areindicated, if known. Manufacturer information is provided, if known.

* These metallic implants, materials, or devices were considered to be safe for MR imaging despite being moved/deflected by the static magnetic fields. Forexample, certain heart-valve prostheses were moved/deflected by the static magnetic fields but the forces were considered to be less than that exerted on thevalves by the beating heart.

t Ferromagnetic coils, filters, and stents typically become firmly incorporated into the vessel wall several weeks following placement, and therefore, it ishighly unlikely that they will be moved or dislodged by magnetic forces.

t While there is no magnetic deflection associated with the triple-lumen thermodilution Swan-Ganz catheter, there has been a report of a catheter “melting”in a patient. Therefore, this catheter would be considered a relative contraindication for MR imaging.

lodgment could injure the patient

(9,11,15,33,44,45,49,54).

All biomedical implants, materials,and devices, particularly those madefrom unknown materials, should beevaluated with ex vivo techniquesbefore MR imaging is performed inpatients with them (11). This proce-dure allows for the determination ofthe presence and amount of ferro-magnetism so that a competent deci-sion can be made concerning the po-tential associated risks.

Aneurysm and Hemostatic Clips

Nineteen of the 26 aneurysm clipstested displayed ferromagnetic quali-ties and, therefore, contraindicate MRimaging (4,9,11,29,32,38,42). Labora-tory studies have demonstrated thatsubjecting ferromagnetic aneurysmclips to static magnetic fields is haz-ardous insofar as these clips may bedisplaced and result in serious conse-quences (4,38,42). Because of this haz-ard, we recommend that patients beexamined with MR imaging only if

the type of aneurysm clip is emphati-cally known to be nonferromagnetic.Four patients with nonferromagneticor weakly ferromagnetic aneurysmclips have undergone MR imagingwithout incident (29).

None of the six hemostatic vascularclips evaluated were attracted bystatic magnetic fields used for MR im-aging up to field strengths of 1.5 T(11). These hemostatic clips are madefrom nonferromagnetic materials and,therefore, do not present a risk to pa-tients during MR imaging. Patientswith each of the hemostatic vascularclips listed have undergone imagingsafely with a 1.5-T MR imager at ourinstitution.

Carotid Artery Vascular Clamps

Each of the five carotid artery vas-cular clamps tested displayed mag-netic deflection in the presence of a1.5-T static magnetic field (22). How-ever, only the Poppen-Blaylock ca-rotid artery vascular clamp was be-lieved to be contraindicated in

patients undergoing MR imaging be-cause of the tremendous ferromag-netism of this device (22). The otherswere believed to be safe because ofthe existence of only mild ferromag-netism (22). Patients with metallic ca-rotid artery vascular clamps have un-dergone imaging with MR systemswith static magnetic fields of 0.35-0.60T without experiencing any discom-fort or neurologic sequelae (22).

Dental Devices and Materials

Of the 16 different dental devicesand materials tested, 12 had measur-able deflection forces but only threeof these represent a potential problemfor patients during MR imaging be-cause they are magnetically activateddevices (see subsequent section, Mag-netically Activated Implants and De-vices) (9,11,37,55).

Heart Valve Prostheses

Twenty-nine different heart valveprostheses have been evaluated for

548 #{149}Radiology August 1991

magnetic deflection related to expo-sure to a 1.5- or 2.35-T static magneticfield (5,11,12). Of these, four werenonferromagnetic and 25 had mea-surable deflection forces. However,because the magnetic deflection ofthese heart valves is minimal com-pared with the force exerted by thebeating heart, MR imaging is not con-

sidered to be hazardous for patientswith these prostheses (5,11,12) (withthe possible exception of performingMR imaging with an MR systemgreater than 0.35 T in a patient that

has a Starr-Edwards Pre 6000 valvewhen there is concern regarding theintegrity of the anulus or presence ofvalvular dehiscence [12J).

Intravascular Coils, Filters,and Stents

Fourteen different intravascularcoils, filters, and stents have been as-sessed for ferromagnetic qualities(13,25,28,31,40). Five of these are fer-romagnetic. However, these devicestypically become firmly incorporatedinto the vessel wall after severalweeks, and therefore, it is unlikely

that any of them would become dis-lodged by magnetic forces (13,58). Pa-tients with most of the intravascularcoils, filters, and stents listed in theTable have undergone imaging with1.5-T MR imagers without incident(13,24,25,31,40,58). Therefore, it is con-

sidered to be safe to perform MR im-aging in patients with any of the in-travascular coils, filters, and stentslisted after a suitable period haselapsed to ensure stable positioningof the device. MR imaging should notbe performed if there is any possibil-ity that an intravascular coil, ifiter, orstent is not held firmly in place.

Ocular Implants

Of the 12 ocular implants tested,the Fatio eyelid spring (23) and theretinal tack made from martensiticstainless steel (27) were deflected by a1.5-T static magnetic field. These maybe uncomfortable (ie, the Fatio eyelidspring) or injure (ie, the martensitic

retinal tack) the patient during MRimaging. The case of a ferromagneticobject damaging the eye of a patientundergoing MR imaging has beenpreviously described (50), which un-derscores the need for special diii-gence when subjecting a patient withany type of ferromagnetic materiallocated near the eye to this imagingprocedure (49).

Orthopedic Implants, Materials,and Devices

Each of the 15 different orthopedicmaterials and devices tested are madefrom nonferromagnetic materials andare safe for MR imaging (11,35). Anadditional concern of subjecting thesetypically large metallic implants to

MR imaging is the potential heatingthat may develop as a result of expo-sure to the gradient and/or radio-fre-quency electromagnetic fields. How-

ever, studies have demonstrated thatheating of these implants is relativelyinsignificant (17). Patients with eachof these orthopedic materials and de-vices have undergone imaging safelywith a 1.5-T MR imager at our institu-tion.

Otologic Implants

The three cochlear implants testedcontraindicate MR imaging because,in addition to being attracted by staticmagnetic fields, they are also electron-ically and/or magnetically activated(8,53). Of the remaining otologic im-plants, only one of them displayedmagnetic deflection during testingwith a 1.5-T static magnetic field(6,8,26,53). This implant, the McGeestapedectomy piston prosthesis, madefrom platinum and Cr17Ni4 stainlesssteel (manufactured during mid-1987), has been recalled by the manu-facturer (53). In addition, patientswho received this implant have beenidentified and issued cards warningthem not to undergo MR imaging(53).

Pellets and Bullets

Most of the pellets and bulletstested are composed of nonferromag-netic materials (15,33). Ammunitionthat proved to be ferromagnetictended to be manufactured in foreigncountries and/or was of a military va-nety (33). Shrapnel typically containssteel and, therefore, presents a poten-tial hazard for MR imaging (33). Be-cause pellets, bullets, and schrapnelmay be contaminated with ferromag-netic materials, the risk versus bene-

fits of performing MR imaging shouldbe carefully considered whether ornot the pellet, bullet, or schrapnel islocated near a vital structure (33,34).Of further note is that, in an effort toreduce lead poisoning in puddle-typeducks, the federal government re-quires, in much of the eastern UnitedStates, the use of steel shotgun pelletsinstead of lead, which would presenta potential hazard to patients under-

going MR imaging and cause severeartifacts (34).

Penile Implants

Only one of the nine penile im-plants, the Dacomed Omniphase, hada significant deflection force mea-sured when exposed to a 1.5-T staticmagnetic field (10). While it is un-likely that this implant would Se-verely injure a patient undergoingMR imaging because of the manner inwhich it is utilized, it would undoubt-edly be uncomfortable for the patient,and therefore, imaging in a patientwith this implant is inadvisable. Pa-tients with each of the nonferromag-netic penile implants have undergoneimaging safely with a 1.5-T MR im-ager at our institution.

Vascular Access Ports

Two of the 33 impiantable vascularaccess ports tested had measurabledeflection forces, but the forces werebelieved to be unimportant relative tothe in vivo application of these im-plants (21). Therefore, it is safe to per-form MR imaging in a patient thatmay have one of these implants.

Miscellaneous

Of the miscellaneous metallic im-plants, materials, and devices tested,the cerebral ventricular shunt tubeconnector (type unknown) (10) andtissue expander with magnetic port(30) had strong deflection forces thatmay be hazardous to patients under-going MR imaging. Another ferro-magnetic implant, the 0-ring washervascular marker, displayed only slightferromagnetic qualities and, there-fore, does not represent a risk to pa-tients examined with MR imaging(Becker RD, personal communication,1989).

Contraceptive diaphragms wereattracted strongly by the 1.5-T staticmagnetic field, but we have per-formed imaging in patients with these

devices who did not complain of anysensation related to movement ofthese objects. Accordingly, the pres-ence of a diaphragm is not believed topose a hazard to a patient during MRimaging. There is, however, a remotepossibility that the contraceptiveproperties of the diaphragm may behindered if it is inadvertantly movedduring an MR imaging examination.

Although the triple-lumen ther-

modilution Swan-Ganz catheter isconstructed of nonferromagnetic ma-

terials, the presence of this device

Volume 180 #{149}Number 2 Radiology #{149}549

may be injurious to the patient duringMR imaging. A report indicated that aportion of a thermodilution Swan-Ganz catheter that was outside thepatient melted as a result of MR imag-ing (59). It was postulated that thehigh-frequency electromagnetic fieldsgenerated by the MR imaging systemcaused eddy current heating of eitherthe wires within the thermodilutioncatheter or the radiopaque materialinside the catheter. This incident sug-gests that MR imaging has the poten-tial to injure patients with triple-lu-men, thermodilution Swan-Ganzcatheters or other similar devices.

Magnetically Activated Implantsand Devices

Certain ferromagnetic implants anddevices such as cochlear implants,tissue expanders, ocular prostheses,and dental implants are magneticallyactivated (8,30,37,55,56,60). Most ofthese are considered to be potentiallyhazardous to patients undergoing MRimaging (49,54). Besides dislodgingthese particular types of implants anddevices, MR imaging may also alter ordamage the operation of the magneticcomponents (49,54), possibly necessi-tating surgery for replacement. Fur-thermore, if the portion of the pros-thesis that the magnet attracts isimplanted in soft tissue (eg, with cer-tam ocular prostheses, the magnet iscontained in the prosthesis and a fer-romagnetic “keeper” is placed in thesoft tissue), it is inadvisable to per-form MR imaging in a patient withthis type of device because of poten-tial adverse effects associated withdisplacement of the keeper (60). MRimaging may be performed safely inpatients with dental magnet appli-ances that are properly attached tosupporting structures after the mag-

net-containing portion of the device isremoved (55). U

Acknowledgment We acknowledge the edi-tonal contributions of Wally Kappehnann, Mil-waukee.

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