Magnetic susceptibility and electrical conductivity of metallic dental materials and their impact on MR imaging artifacts.
OBJECTIVE
The aim of this study was to test the hypothesis that dental materials vary significantly in MR-relevant material parameters-magnetic susceptibility and electrical conductivity, and that knowledge of these parameters may be used to estimate the quality of MR imaging in the presence of devices made of such materials.


METHODS
Magnetic susceptibility, electrical conductivity and artifacts were evaluated for 45 standardized cylindrical samples of dental alloys and amalgams. Magnetic susceptibility was determined by fitting the phase of gradient-echo MR images to numerically modeled data. Electrical conductivity was determined by standard electrotechnical measurements. Artifact sizes were measured in spin-echo (SE) and gradient-echo (GE) images at 1.5T according to the standards of the American Society for Testing and Materials.


RESULTS
It has been confirmed that dental materials differ considerably in their magnetic susceptibility, electrical conductivity and artifacts. For typical dental devices, magnetic susceptibility differences were found of little clinical importance for diagnostic SE/GE imaging of the neck and brain, but significant for orofacial imaging. Short-TE GE imaging has been found possible even in very close distances from dental devices made of amalgams, precious alloys and titanium alloys. Nickel-chromium and cobalt-chromium artifacts were found still acceptable, but large restorations of aluminum bronzes may preclude imaging of the orofacial region. The influence of electrical conductivity on the artifact size was found negligible.


CONCLUSIONS
MR imaging is possible even close to dental devices if they are made of dental materials with low magnetic susceptibility. Not all materials in current use meet this requirement.
Starcuková
Jana
J
Institute of Scientific Instruments of the ASCR, v.v.i., Academy of Sciences of the Czech Republic, Královopolská 147, 612 64 Brno, Czech Republic. jana@isibrno.cz
Starcuk
Zenon
Z
Hubálková
Hana
H
Linetskiy
Igor
I
D017607:Aluminum Compounds / Q000737:chemistry; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology; D002858:Chromium Alloys / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry*; D003723:Dental Amalgam / Q000737:chemistry*; D004553:Electric Conductivity; D005145:Face / Q000033:anatomy & histology; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D008280:Magnetics; D008422:Materials Testing; D009055:Mouth / Q000033:anatomy & histology; D009333:Neck / Q000033:anatomy & histology; D009532:Nickel / Q000737:chemistry; D019047:Phantoms, Imaging; D014025:Titanium / Q000737:chemistry; D051598:Whole Body Imaging / Q000295:instrumentation
D017607:Aluminum Compounds; D002858:Chromium Alloys; D003722:Dental Alloys; D006047:Gold Alloys; C062136:nickel copper alloy; D003300:Copper; D009532:Nickel; D003723:Dental Amalgam; D014025:Titanium