Design of a control strategy for a robotically assisted ultrasound guided biopsy

Finished: 2019-12-17

MSc assignment

Breast cancer is one of the most common forms of cancer today that is negatively affecting the lives of many people. One very important step in diagnosing it, is performing a biopsy procedure. During a biopsy, the radiologist inserts a needle inside the breast tissue and using an ultrasound probe, the radiologist guides it toward the target lesion to extract a sample. The extracted cells are then further examined for a diagnosis to be reached. However, the biopsy can be time-consuming and uncomfortable for patients. Additionally, the accuracy of the result is heavily dependent on the experience of the practitioner who is performing the process. These same practitioners also tend to suffer from fatigue and work related musculoskeletal pain.

This is where the MURAB project comes in. It attempts to improve the patients experience, reduce the time of entire diagnosis process, have a better accuracy rate, and benefit radiologists' working conditions. An end-effector for performing a biopsy has already been designed. It consists of an ultrasound probe holder and a needle guiding mechanism. This end-effector is mounted on a KUKA LBR Med articulated robotic arm.

The goal of this thesis is to design a controller that will utilize this end-effector and properly guide the needle to the desired target. There are a number of milestones that need to be reached for this goal to be achieved. First, a reliable method that will estimate the motion of the tissue is needed as to accurately know where the target tissue is located at all times. This is needed because when inserting the needle, human tissue will move around and the target will change location. Secondly, a controller that will properly aim the needle is required. It should be noted that the robotic system will not insert the needle into the patient, as that would be dangerous. The needle will be manually moved inwards by the radiologist. The third and final milestone will be the design of an impedance controller, based on the previous work. This would allow the radiologist to adjust the directions of the needle, in case part of the guiding system presents some kind of error.