Fluoroscopic radiation exposure of the kyphoplasty patient

Abstract

Kyphoplasty (KP) is a minimally invasive technique for the percutaneous stabilisation of vertebral fractures. As such, this technique is highly dependent upon intraoperative fluoroscopic visualisation. In order to assess the range of radiation doses that patients are typically subjected to, 60 consecutive procedures using simultaneous bilateral fluoroscopy were analysed with respect to exposure time (ET). In a subset of 16 of these patients, a theoretical entrance skin dose (ESD) and effective dose was additionally calculated from intraoperatively measured dose area product. Average fluoroscopy time for single level cases reached 2.2 min (range 0.6-4.3) in the lateral plane and 1.6 min (range 0.5-3.0) in the anterior-posterior plane. For multiple level cases the corresponding ET per level was 1.7 min (range 0.6-2.9) per level in the lateral and 1.1 min (range 0.5-2.0) in the anterior-posterior plane. ESD was estimated as an average 0.32 Gy (range 0.05-0.86) in the anterior-posterior and 0.68 Gy (range 0.10-1.43) in the lateral plane. Effective dose (cumulative from both planes) averaged 4.28 mSv (range 0.47-10.14). Safety margins for the development of early transient erythema are respected within the presented fluoroscopy times. Longer ET in the lateral plane may however breach the 2 Gy threshold. Use of large c-arms and judiciously operating the exposure is recommended. With regard to effective dose, a single fluoroscopy guided KP performed for osteoporotic or traumatic vertebral fractures is a safe procedure.

Fig. 1

Drawing of the typical operative set-up for percutaneous KP under biplanar fluoroscopic guidance in a lateral view (A) and birds eye view (B). The surgeon and assistant are positioned at the sides of the patient, while the scrub nurse is at the foot end and the anaesthesiologist is at the head of the table

Fig. 2

Schematic representation of the fluoroscopy setting used to experimentally determine the entrance field sizes in both planes of view. A typical operative set-up was simulated and X-ray films were exposed at the usual distance of the patient from the focus (46 cm focus to skin distance ap and 36 cm focus to skin distance lat). Field sizes of 37.4 cm² in the ap plane and 30.8 cm² in the lat plane were determined. ap anterior–posterior fluoroscopy unit with 100 cm focus to image intensifier distance, lat lateral fluoroscopy unit with 90 cm focus to image intensifier distance, BV image intensifier

Fig. 3

Dependence of DAP on fluoroscopic ET for cases 45 to 60