The present invention provides an external fixation device and method thereof. The device includes at least an insert for inserting into a patient's tissue such as a bone. The insert is fastened to a fastening assembly which comprises at least a RF heat source member during MRI scanning of the patient. At least a part of the RF heat source member's surface is covered with an absorption material to reduce the direct or indirect transfer of RF induced heat from the member to the insert. The absorption material has an electric conductivity greater than 10−4 S/m.