Intraoperative radiotherapy: a CT-guided navigation system

Introduction: The fact that conventional intraoperative radiotherapy (IORT) does not give the opportunity for exact documentation of the applied radia tion volume and dose distribution has been criticised. We would like to int roduce a system for surgical navigation and documentation of the flab posit ioning for intraoperative brachytherapy in afterloading flab technique. Met hods: Our system consists of an electromagnetic 3D digitizer and a PC works tation. Preoperatively taken spiral CT scans of the tumour region are used for navigation and documentation of the flab positioning, analogous to the procedure in neuronavigation. Registration is done via an external referenc e system attached to the iliac bone of the patient. Results: The mean accur acy of digitalization of the 100 spheres in a pelvis model is about 2.6 +/- 0.5-3.7 +/- 0.9 mm. Mean navigation accuracy is 2.4 +/- 0.8-3.3 +/- 0.8 mm . These figures correspond to the clinical experience of our surgeons. Conc lusions: The optimization of the Rab positioning by CT-guided navigation an d the more accurate documentation of the dose volume and distribution in th e patient is an important step towards improving the quality of individual radiotherapy. We are of the opinion that surgical navigation in the pelvic region should be subject to additional investigation in order to optimize t he procedure.