Safety and compatibility of magnetic-controlled growing rods and magnetic resonance imaging.
OBJECTIVE
Magnetically controlled growth rods (MCGRs) are a new technology for the management of early-onset pediatric deformity enabling guided spinal growth by controlling the curvature. These rods contain a rare earth magnet and are contraindicated for MRI. We have investigated the behavior MCGRs to determine whether MRI adversely affects rod properties and to determine the extent of image distortion.


METHODS
This is an in vitro experiment using two magnetic growth rods secured in a 1.5 T MRI. A gradient echo sequence MRI was performed to evaluate whether the rods elongated, contracted or rotated during scanning and a phantom model was used to evaluate the amount of artifact induced.


RESULTS
The rod was not activated or subsequently impaired by the process of MRI. Image distortion of 28.9 cm along the long axis of the magnet and 20.1 cm perpendicular to this was seen with extension 10.6 cm cranial to the magnet housing. No negative effect was demonstrated on the magnetic rod elongation mechanism.


CONCLUSIONS
This study has demonstrated that there are no detrimental effects of MRI on the MCGR and imaging of the head and neck phantom can still be interpreted. Further in vivo study is warranted.
Exeter Spine Unit, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, UK. henry.budd@hotmail.com.
Henry R
HR
Budd
Exeter Spine Unit, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, UK.
Oliver M
OM
Stokes
Physics, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK.
Judith
J
Meakin
Exeter NIHR Clinical Research Facility, University of Exeter Medical School, University of Exeter, Exeter, UK.
Jonathan
J
Fulford
Exeter Spine Unit, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter NHS Foundation Trust, Barrack Road, Exeter, UK.
Michael
M
Hutton
D016477:Artifacts; D006801:Humans; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging; D059346:Magnets; D009983:Orthopedic Equipment; D012449:Safety; D012600:Scoliosis / Q000601:surgery*
GROWTH; Imaging; MRI; Rods; Scoliosis