Force sensing in Sunram 7

MSc assignment

In breast cancer screening, lesions may be found which need to be biopsied to check for malignancy. Some lesions are only visible on MRI, requiring an MRI-guided biopsy procedure. Current manual systems are inaccurate and there is demand for an MR safe surgical robot that performs the task semi-automatically. At RaM, the Sunram7 biopsy robot has been developed for this purpose.

One limitation of the Sunram7 is the inability to measure forces. The biopsy needle interacts with the skin, fatty/fibrous/glandular tissues and the lesion. Certain tissue types are stiffer than others and in a manual biopsy the radiologist can often "feel" the lesion with the needle.

The MR safe requirement means that no electronic sensors can be used inside the Sunram7. One alternative is the use of fiber optics. By manipulating the light path of a pair of fibers, a measure of displacement inside the Sunram 7 could be retrieved in the controller. This displacement can be correlated to the force acting on the needle, and voilà, we have haptic feedback! Of course you can also explore other ways of MR safe force sensing such as measuring pneumatic impedance.

This assignment is particularly suitable for technical students with strong interest in mechanical design and signal processing. However, a different MSc assignment which focuses more on the control side is also possible.

Check the video of the robot to have an idea how it moves around.

Interested? Contact Vincent Groenhuis:, or just come to CR-3.613.