Navigation in Prostate Surgery

For the navigated surgery the informatics of the German Cancer Research Center overlay the endoscopic video precisely with a 3D model of the patients’ anatomy. | © dkfz.de

Today, prostate cancer is the most common malignant cancer disease among men in Germany. As long as the disease remains limited to this organ, surgical removal of the prostate represents one of the safest methods of treatment. Conventional laparoscopy, as well as robot-assisted prostate surgery is of increasing importance. During surgeries in anatomical areas with limited spatial possibilities, as it is found in the small pelvis area, these procedures offer a gentle alternative. Nevertheless the surgeon is challenged by a limited field of view along with a decreased tactile feedback.

At the German Cancer Research Center, in collaboration with the University Clinic of Heidelberg, and the SLK Clincs Heilbronn, a computer - based assistance system has been developed in recent years. It provides the surgeon during tissue preparation with beneficial information about relevant anatomical structures nearby the surgical site. Hidden structures as the urethra, the rectum, the neurovascular bundles, or tissue which is potentially infiltrated by cancer cells, can be superimposed to enhance the endoscopic video frame (see Picture “Augemented Reality”).

This additional information about the patients’ anatomy shall support the surgeon to overcome the limitations of minimally invasive surgery, and to increase surgical precision and safety. Therefore, the system shall contribute to spare the healthy tissue as far as possible and to ensure the total resection of all cancerous cells. Different innovative imaging modalities may be used to set up a pre-operative plan of the intervention which includes an individual 3D model of the patient’s anatomy of the small pelvis. During prostatectomy, a transrectal 3D ultrasound probe is used to register the virtual patient model with the present anatomy of the patient. Due to its soft tissue characteristic the prostate tends to change the position during surgery. Compensation of organ shift was a technological challenge which had to be solved. For this purpose, the collaboration with a well-known manufacturer of surgical instruments led to the creation of novel, needle shaped navigation aids, which are traceable in both, ultrasound images and endoscopic video.

Due to the real-time evaluation of the endoscopic video frames the system is able to detect the prostate shift instantly to correct the displayed information for the new anatomic situation. Furthermore, an integrated safety mechanism enables a redundant validity check of the displayed information. Any imprecise or faulty visualization of anatomical structures can be reliably detected, and therefore prevented. As of September 2008, few patients with local prostate cancer are treated by the navigated prostatectomy as part of a MPG-Study at the SLK Clinics Heilbronn. Furthermore, scientists work on a technological extension of this approach towards further urological and visceral interventions, as for example the laparoscopic resection of kidney cancer (partial nephrectomy, see Picture “Nephew Intervention”).

In the future the existing system will be adapted for real-time processing of high definition endoscopy data. The system will be combined with optical tracking which promises to enhance the accuracy and robustness of the visualization.

Project team