RF artifacts caused by metallic implants or instruments which get more prominent at 3 T: an in vitro study
✍ Scribed by Hansjörg Graf; Ulrike A. Lauer; Alexander Berger; Fritz Schick
- Book ID
- 104060215
- Publisher
- Elsevier Science
- Year
- 2005
- Tongue
- English
- Weight
- 390 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0730-725X
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✦ Synopsis
Metallic devices with high electrical conductivity inside or adjacent to the body might lead to marked alterations of the RF amplitude B 1 in the tissue under investigation, especially at increased RF frequency, and if specific conditions for electromagnetic resonance are fulfilled. RF-metal interaction effects were investigated systematically at B 0 = 0.2, 1.5 and 3 T analyzing correlated image artifacts for copper wires (d = 1 mm, L = 53 and 27 cm), and for following instruments and implants made of titanium or nitinol: biopsy needles, hip prostheses, vascular stents and aneurysm clips. The samples were examined in Gd-DTPA-doped 140 mM NaCl solution using spin-echo (SE) sequences with high readout bandwidth. Automatic transmitter adjustment V T,auto and manually reduced transmitter voltage V T were applied in order to detect B 1 enhancement. At 0.2 T, beyond the shielding of the luminal region of the stents, no RF effects were observed. At 1.5 T, the copper wires caused distinct RF artifacts. At 3 T, RF artifacts also appeared for the hip prostheses and the biopsy needles. Stents with pronounced luminal shielding at lower field strength revealed marked B 1 enhancement close to their outer surface.