Scatter reduction from an O-arm imaging system

Abstract

Scanner detectors and gantry hardware in a typical fixed CT attenuate the primary beam. Typical isodose curves at 2 metres for a fixed CT installation show scatter air kerma distributions to be reduced by a factor of almost 100 at the 0° angle compared to the front 90° angle. However, unlike a fixed CT gantry, O-arm covering contains little beam attenuating material. Scatter measurements behind the control panel of the O-arm (the 0° angle) are low but only extend to the height of the control panel and therefore not the full height of a person. Overall, our scatter measurements for our O-arm imaging system indicated that personnel should not remain in the theatre operating room while imaging is taking place. This is a particular issue for anaesthetists during complex spinal surgery. During this type of surgery, the patient is required to do a breath hold during the cone beam CT imaging rotation and the anaesthetist is required to leave the theatre for up to two minutes. Ideally the anaesthetist could remain in the theatre to closely observe the patient. This study investigates the effect and feasibility of attaching lead drapes to the O-arm cover in the sterile theatre environment in order to determine whether scatter can be reduced to a level that will allow an anaesthetist to remain in the operating theatre during the complex O-arm procedures.