title: RF-related heating assessment of extracranial neurosurgical implants at 7T.
abstract: OBJECTIVE
  The purpose was to evaluate radiofrequency (RF)-related heating of commonly used extracranial neurosurgical implants in 7-T magnetic resonance imaging (MRI).
  
  
  METHODS
  Experiments were performed using a 7-T MR system equipped with a transmit/receive RF head coil. Four commonly used titanium neurosurgical implants were studied using a test procedure adapted from the American Society for Testing and Materials Standard F2182-11a. Implants (n=4) were tested with an MRI turbo spin echo pulse sequence designed to achieve maximum RF exposure [specific absorption rate (SAR) level=9.9W/kg], which was further validated by performing calorimetry. Maximum temperature increases near each implant's surface were measured using fiberoptic temperature probes in a gelled-saline-filled phantom that mimicked the conductive properties of soft tissue. Measurement results were compared to literature data for patient safety.
  
  
  RESULTS
  The highest achievable phantom averaged SAR was determined by calorimetry to be 2.0±0.1W/kg due to the highly conservative SAR estimation model used by this 7-T MR system. The maximum temperature increase at this SAR level was below 1.0°C for all extracranial neurosurgical implants that underwent testing.
  
  
  CONCLUSIONS
  The findings indicated that RF-related heating under the conditions used in this investigation is not a significant safety concern for patients with the particular extracranial neurosurgical implants evaluated in this study.
authors: The Ohio State University, Columbus, OH, USA.
authors: Christina L
authors: CL
authors: Sammet
authors: Xiangyu
authors: X
authors: Yang
authors: Peter A
authors: PA
authors: Wassenaar
authors: Eric C
authors: EC
authors: Bourekas
authors: Brian A
authors: BA
authors: Yuh
authors: Frank
authors: F
authors: Shellock
authors: Steffen
authors: S
authors: Sammet
authors: Michael V
authors: MV
authors: Knopp
mesh_terms: D032701:Biomimetics / Q000295:instrumentation; D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D001921:Brain / Q000502:physiology* / Q000528:radiation effects*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D019635:Neurosurgical Procedures / Q000295:instrumentation*; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D011829:Radiation Dosage; D011846:Radio Waves