Biomedical subjects

Mehrdad Moallem

Publications and source records attributed to Mehrdad Moallem.

3 recordsLinked to original sources

PubMed2006

Needle insertion into soft tissue: a survey.

Needle insertion in soft tissue has attracted considerable attention in recent years due to its application in minimally invasive percutaneous procedures such as biopsies and brachytherapy. This paper presents a survey of the current state of research on needle insertion in soft tissue. It examines the topic from several aspects, e.g. modeling needle insertion forces, modeling tissue deformation and needle deflection during insertion, robot-assisted needle insertion, and the effect of different trajectories on tissue deformation. All studies show that the axial force of a needle during insertion in soft tissue is the summation of different forces distributed along the needle shaft such as stiffness force, frictional force and cutting force. Some studies have modeled these forces. The force data in some procedures is used for identifying tissue layers as the needle is inserted or for path planning. Needle deflection and tissue deformation are major problems for accurate needle insertion and attempts have been made to model them. Using current models several insertion techniques have been developed which are briefly reviewed in this paper.

Adipose Tissue↗

PubMed2006

Control of soft tissue deformation during robotic needle insertion.

Accurate needle insertion into soft, inhomogeneous tissue is of practical interest because of its importance in percutaneous therapies. In procedures that involve multiple needle insertions such as transrectal ultrasound-guided prostate brachytherapy, it is important to reduce tissue deformation before puncture and during needle insertion. In order to reduce this deformation, we have studied the effect of different trajectories for a 2-DOF (degrees of freedom) robot performing needle insertion in soft tissue. To obtain an optimum trajectory, we have compared tissue indentation and frictional forces for different trajectories. According to the results of our experiments, infinitesimal force per tissue displacement is a useful parameter for online trajectory update. In addition, the results show that axial rotation can reduce tissue indentation before puncture and frictional forces after puncture. Our proposed position/force controller is shown to provide considerable improvement in performance with regard to minimizing tissue deformation before puncture.

Animals↗

PubMed2005

A layered goal-oriented fuzzy motion planning strategy for mobile robot navigation.

Most conventional motion planning algorithms that are based on the model of the environment cannot perform well when dealing with the navigation problem for real-world mobile robots where the environment is unknown and can change dynamically. In this paper, a layered goal-oriented motion planning strategy using fuzzy logic is developed for a mobile robot navigating in an unknown environment. The information about the global goal and the long-range sensory data are used by the first layer of the planner to produce an intermediate goal, referred to as the way-point, that gives a favorable direction in terms of seeking the goal within the detected area. The second layer of the planner takes this way-point as a subgoal and, using short-range sensory data, guides the robot to reach the subgoal while avoiding collisions. The resulting path, connecting an initial point to a goal position, is similar to the path produced by the visibility graph motion planning method, but in this approach there is no assumption about the environment. Due to its simplicity and capability for real-time implementation, fuzzy logic has been used for the proposed motion planning strategy. The resulting navigation system is implemented on a real mobile robot, Koala, and tested in various environments. Experimental results are presented which demonstrate the effectiveness of the proposed fuzzy navigation system.

Algorithms↗