R. Verbeeck, H. Demeulemeester[1], B. Nuttin[1], D. Vandermeulen, G. Marchal, P. Suetens
Short-pulsed laser beams can carefully and precisely ablate tissue. The aim of this BIOMED-2 project is to bring a laser probe under minimally invasive conditions (using stereotactic guidance) to a brain tumour. The laser probe couples the laser beam directly into the tumour via flexible mirrors. The inner guide of the laser probe rotates and moves up and down, ablating concentric cylinders in the lesion. Laser ablation requires an extensive pre-operative planning on a dedicated workstation, and a precise implementation, monitoring and (if necessary) adjustement of the treatment plan.
Currently, a 1.5 W laser system exists and the mechanical influence of the laser probe on brain tissue has been examined in animal experiments under semi-stereotactic conditions. Insertion of the laser probe causes edema all along the trajectory. Small bleedings occur even at relatively large distances from the trajectory, even without rotation of the probe or aspiration. This can cause interpretation problems for the images of the confocal laser microscope. Due to a lack of data, this damage cannot be compared to that of more established clinical procedures.
The animal experimens have also already revealed some flaws in the design of the laser probe. Improvements have been made on the optical layout of the confocal microscope and on the pressure regulation system for the rinsing fluid.
At the moment, it is not yet clear whether the confocal microscope can deliver sufficiently detailed images of blood vessels fast enough to avoid heamorrhage induced by the ablating laser. The next experiments will test whether continuous coagulation prior to ablation can prevent bleedings.
The first experience with intra-operative ultrasound (US) showed that the images cannot be used to control the operation safely because of artefacts and because it is difficult to distinguish and interpret structures in the images. The value of intra-operative US can possibly be augmented if the US probe can be tracked in stereotactic space and intra-operative US images can be compared directly to reslices of pre-operative MR data.
The planning software will be able to register pre-operative images in stereotactic space using a specially developed stereotactic frame for dogs (Radionics Inc, Burlington, MA) and/or an optical tracking system and bone implanted reference markers.
In a later stage of the project, an MR compatible laser probe will be developed such that treatment can proceed under precise, intra-operative MR control.
| Wow, i enjoyed that, and would like to see what other wacky stories lie in store for me |
| Boy, this entire news about laser and dogs thing is way lame... I wonder if there could possibly be anything lamer on this page? |