The Nottingham radiation protocol for O-arm navigation in paediatric deformity patients: a feasibility study

Abstract

O-arm assisted pedicle screw placement has been proven to be more accurate than free-hand technique. Radiation exposure remains the primary drawback. We determined thefeasibility and safety of a reduced radiation protocol in paediatric patients undergoing scoliosis correction. A reduced radiation protocol for a medtronic O-arm navigational system was devised. 3D CT reconstructions of an anthropomorphic pelvic phantom indicated adequate image quality after reduction to 14% of current manufacturer default factors. A feasibility study to test the image quality was undertaken on four patients, one with syndromic and three with idiopathic scoliosis each receiving progressively reducing radiation exposure of 60%, 50%, 40% and 14% of what would have been delivered using the manufacturer default protocol. This represented 32% of the mayo clinic protocol. It was achieved by reducing the x-ray tube current to 10mA while keeping the tube potential at 90kVp. A low dose O-arm protocol was able to generate adequate image quality while delivering as little as 14% (for lumbar region reconstructions) of the recommended protocol radiation dose. The total radiation dose delivered with this protocol was approximately 0.8 milliSieverts for a single spin. This effective dose represents < 1/3 of average UK and < 1/6 average US annual radiation exposure. There were no neurological or implant-related complications. Our low dose O-arm radiation protocol significantly reduces the radiation exposure compared to the manufacturer recommended Mayo clinic protocol providing operational image quality to allow accurate screw placement in spinal deformity.