MRI Safety, Test Methods and Construction of a Database

Abstract: Magnetic Resonance Imaging, MRI, is a diagnostic tool in progress which has been available at major hospitals since the mid eighties. Today almost all hospitals world wide may depict the human body with their own MRI scanner. MRI is dependent on a uniform magnetic field inside the scanner tunnel and Radio frequent (RF) waves used for excitation of the magnetic dipole moments in the body. These properties along with the magnetic field surrounding the scanner are associated with dangerous effects - when interacting with medical implants made of metals. These dangerous effects are twisting forces or torques, heating and translational forces respectively. A database containing information about known implants behaviour regarding these effects among with earlier documentation and information concerning MRI patient safety at Karolinska hospital, Huddinge was constructed. Also a phantom used for heating effect measurements was constructed and heating effect measurements were performed at a SPC4129 locking titanium Peritoneal Dialysis (PD) catheter adapter and a Deep Brain Stimulator (DBS) in order to test the phantom and confirm the theory about RF induced heating on medical implants. Evidence for heating effects caused by the implants was found. A torque measurement apparatus was constructed and measurements were performed. All measurements where performed in order to investigate the functionality of the apparatus and also the theory behind dangerous magnetically induced torques (twisting movements). Substantial torque were measured on the ferromagnetic device used for the test. The heating phantom and torque measurement apparatus is slightly modified models of those proposed by ASTM (American Society for Testing and Materials).