Liver Vessel Parameter Estimation from Tactile Imaging Information. In: Cotin S, Metaxas D, editors. Medical Simulation. Berlin: Springer Berlin Heidelberg; 2004. pp. 59-66. [DOI: 10.1007/978-3-540-25968-8_7]

Mathematical study of the effects of different intrahepatic cooling on thermal ablation zones

Thermal ablation of a tumour in the liver with Radio Frequency energy can be accomplished by using a probe inserted into the tissue under the guidance of medical imaging. The extent of ablation can be significantly affected by heat loss due to the high blood perfusion in the liver, especially when the tumour is located close to large vessels. A mathematical model is thus presented here to investigate the heat sinking effects of large vessels, combining a 3D two-equation coupled bio-heat model and a 1D model of convective heat transport across the blood vessel surface. The model simulation is able to recover the experimentally observed different intrahepatic cooling on thermal ablation zones: hepatic veins showed a focal indentation whereas portal veins showed broad flattening of the ablation zones. Moreover, this study also illustrates that this shape derivation can largely be attributed to the temperature variations between the microvascular branches of portal vein as compared with hepatic vein. In contrast, different amount of surface heat convection on the vessel wall between these two types of veins, however, has a minor effect.

A medical tactile sensing instrument for detecting embedded objects, with specific application for breast examination

BACKGROUND

In this paper, having considered the tactile sensing and palpation of a physician in order to detect abnormal masses in the breast, we simplified and then modelled the tissue containing a mass and used contact elements to analyse the tactile sensor function.

METHODS

By using the finite element method, the effects of the mass existence appeared on the surface of the tissue. This was due to exerting mechanical load on the modelled tissue surface. Following this, a tactile sensing instrument called the 'tactile tumour detector' (TTD) was designed and constructed. This device is able to detect abnormal objects in the simulated models by making contact with model surfaces. In order to perform a series of precise experiments, a robot that could hold the tactile probe was used. The velocity of the linear movement of the probe is low enough to ensure that the tissue behaves in the linear elastic range, so that dynamic effects can be neglected.

RESULTS AND DISCUSSION

The maximum value of stresses was chosen as the comparison criterion. The variation of this criterion vs. the mass parameter changes was investigated and good agreements between numerical and experimental results were obtained. Moreover, the sensitivity and specificity of TTD and clinical breast examination (CBE) in the detection of breast masses, in comparison to sonography as the 'gold standard', were calculated by performing clinical trials on 55 cases.

Graphical Rendering of Localized Lumps for MIS Applications

Minimally invasive sugery (MIS) has increasingly been used in different surgical routines despite having significant shortcomings such as a lack of tactile feedback. Restoring this missing tactile information, particularly the information gained through tissue palpation, would be a significant enhancement to MIS capabilities. Tissue palpation is particularly important and commonly used in locating embedded lumps. The present study is inspired by this major limitation of the MIS procedure and is aimed at developing a system to reconstruct the lost palpation capability of surgeons in an effective way. By collecting necessary information on the size and location of hidden features using MIS graspers equipped with tactile sensors, the information can be processed and graphically rendered to the surgeon. Therefore, using the proposed system, surgeons can identify the presence or absence, location, and approximate size of hidden lumps simply by grasping the target organ with a smart endoscopic grasper. The results of the conducted experiments on the prototyped MIS graspers represented by graphical images are compared with those of the finite element models.