Clinical Background

RF Ablation of Liver tumors

Hyperthermia ablation is used for treatment of benign and malignant tumors. The tissue response to heating is related to the absolute temperature induced in the tissue and exposure time. Irreversible tissue destruction occurs when tissue is exposed to temperatures in excess of 50-55C. Hyperthermia ablation has been widely used for treating malignant liver tumors not amenable to conventional surgical resection. Heating modalities in clinical use include laser, microwave, radiofrequency, and focused ultrasound. The exact size and shape of the resulting ablation is difficult to predict because of heterogeneous distribution of the thermal energy due to local disparity in tissue composition, tissue anatomy, and vascularization. In clinical series, local tumor progression after ablation therapy has been reported to be as high as 3060%, indicating the presence of viable malignant cells at the treated site. Improved intraprocedural monitoring may reduce the local tumor progression rates associated with thermal ablation and prove beneficial in regard to long-term patient survival.

Multiplanar imaging capabilities and excellent soft tissue contrast make magnetic resonance imaging (MRI) ideally suited for intra-operative visualization, positioning of energy applicators, and monitoring of thermal ablation procedures. Additionally, noninvasive, three-dimensional mapping of relative temperature changes is feasible with MRI, based on the longitudinal relaxation time (T1), the diffusion coefficient (D), or proton resonance frequency (PRF) of tissue water.

Laparoscopic Liver Resection

Laparoscopic liver resection was first reported in 1991. Since then, more than 500 journal articles have been published describing the full spectrum of resections of benign and malignant liver and pancreatic disease. Leaders in the field believe that there will be a significant role for minimally invasive approaches to hepatic surgery in the future.

One of the key issues identified by ARIS*ER experts related to this clinical application was reduction of bleedings. This issue is also raised by Optiz where it is concluded that bleeding remains a major complication during laparoscopic surgery, other reports support the same conclusion.

Another key issue identified by ARIS*ER experts relates to visualisation which should support navigation and orientation. Such visualization can be accomplished by fusion of MRI, CT or ultrasound images with video-images. Bao has reported on a system for ultrasound-to-computer-tomography registration for image-guided laparoscopic liver surgery. The results were acquired using a phantom, assuming a rigid body situation. It provides an interesting background for the planned work in ARIS*ER. Other reports describe specific issues related to navigation accuracy and projection accuracy (for Augmented Reality) in the domain of laparoscopic liver resection.

Endoscopic mitral valve repair/replacement

The introduction of minimally invasive cardiac surgery has lead to reduced hospital stay and shorter recovery. Endoscopic mitral valve surgery can now be routinely performed through a 4cm working port, usually in the 4th intercostal space. A detailed description of this predure can be found by following this link.The procedure has also been performed by several groups using the daVinci robot system.