Reconstruction and navigation system for intraoperative brachytherapy using the flab technique for colorectal tumor bed irradiation.

PURPOSE: To present the development of a new navigation and reconstruction system based on an electromagnetic free-hand tracker and on CT imaging for treatment planning of intraoperative high-dose-rate brachytherapy (IORT-HDRB) in the sacral region. Our aim is to improve accuracy and to enable individualized treatment planning and dose documentation to be performed for IORT-HDRB using a flab technique. METHODS AND MATERIALS: The material consists of an electromagnetic 3D tracker system, a PC workstation with Microsoft Windows NT 4.0 operating system, and a recognition program for continuous speech. In addition, we designed an external reference system constructed of titanium and Perspex, which is positioned in the pelvis, and a special digitizer pen for reconstruction of the flab geometry. The flab design incorporates a series of silicon 10-mm-diameter spherical pellets. Measurements were made with a pelvic phantom in order to study the accuracy of the system. The reconstruction results are stored and can be exported via network or floppy to our different treatment planning systems. RESULTS: Our results for the reconstruction of a flab with six catheters and a total of 100 spherical pellets give mean errors in the range (2.5 +/- 0.6) mm to (3.5 +/- 0.8) mm depending on the positions of the pelvic phantom and transmitter relative to the operation table. These errors are calculated by comparing the reconstruction results of our system with those using a CT-based reconstruction of the flab geometry. For the accuracy of the navigation system for the pelvic phantom, we obtained mean errors in the range (2.2 +/- 0.7) mm to (3. 1 +/- 1.0) mm. CONCLUSIONS: The new system we have developed enables navigation and reconstruction within the surgical environment with a clinically acceptable level of accuracy. It offers the possibility of individualized treatment planning and effective documentation of the 3D dose distribution in IORT-HDRB using a flab technique.

[Intraoperative radiotherapy--progress with a CT-assisted navigation system]. / Intraoperative Strahlentherapie--Fortschritt durch ein CT-gestütztes Navigationssystem.

INTRODUCTION: The fact that conventional intraoperative radiotherapy (IORT) does not give the opportunity for exact documentation of the applied radiation volume and dose distribution has been criticised. We would like to introduce a system for surgical navigation and documentation of the flab positioning for intraoperative brachytherapy in afterloading flab technique. METHODS: Our system consists of an electromagnetic 3D digitizer and a PC workstation. 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 reference system attached to the iliac bone of the patient. RESULTS: The mean accuracy 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. CONCLUSIONS: The optimization of the flab positioning by CT-guided navigation and the more accurate documentation of the dose volume and distribution in the 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 the procedure.

CT-based navigation systems for intraoperative radiotherapy using the afterloading-flab technique.

INTRODUCTION: The fact that conventional intraoperative radiotherapy does not give the opportunity to exactly document the radiation volume applied and the dose distribution has been criticized in many ways. We would like to introduce a system for surgical navigation and documentation of flap positioning in intraoperative brachytherapy using the afterloading flap technique. METHODS: Our system consists of an electromagnetic 3D-digitizer and a PC workstation. Spiral CT scans of the tumor region taken preoperatively are used for navigation and documentation of flap positioning, analogous to the procedure in neuronavigation. Registration is done via an external reference system which is attached to the iliac bone of the patient. RESULTS: The mean accuracy of digitalization of the 100 spheres in a pelvis model is about 2.6 +/- 0.5 to 3.7 +/- 9.9 mm. The mean navigation accuracy is 2.4 +/- 0.8 to 3.3 +/- 0.8 mm. These figures correspond to the clinical experience of our surgeons. DISCUSSION: The optimization of flab positioning by CT-guided navigation and the more accurate documentation of the dose volume and distribution in the patient is an important step on the way to improving the quality of individual radiation therapy. We are of the opinion that surgical navigation in the pelvic region should be subject to additional investigation in order to optimize the procedure.