Freehand tremors in surgeons pose a grave risk when performing fine-scale microsurgery. To address this issue, researchers have developed a fiber-optic-sensor-based microsurgical tool that can stabilize and minimize the effect of hand tremors.
The CAD model and prototype of the fiber-optic-sensor-based microsurgical tool, SMART. Courtesy Cheol Song, Johns Hopkins University
The Smart Micromanipulation Aided Robotic-surgical Tool (SMART) was developed by researchers from the Johns Hopkins School of Medicine and the Johns Hopkins University Whiting School of Engineering. They utilized a special type of optical fiber sensor, Optical Coherence Tomography (OCT) imaging technique and piezoelectric motors controlled through computers, for stabilizing the surgical tooltip.
Fine motor control is required for microsurgery. However, even when absolutely steady, the human hand trembles approximately 50-100 µ, several times within a second. The techniques developed so far have not been able to accurately measure the relative motions of a surgical instrument with respect to its target and compensate for the difference.
OCT has a higher resolution of around 10 µ and utilizes near infrared light for imaging tissues. It is considered safe for the eyes. The researchers integrated a highly precise OCT-based rapid distance sensor into a handheld surgical device that had the capability of holding different types of surgical instruments. Common path optical coherence tomography enabled this facility.
The sensor’s optical signals transmit and receive near-IR light through a single fiber-optic cable, which is very small and flexible. The cable can be integrated into the front of the surgery tool. The high-speed fiber-optic sensor sends and receives near infrared laser beams continuously to measure the probe’s motion. This data is sent to a computer that signals the piezoelectric motors in the surgical device to control the tool tip’s position. This compensates the hand tremors experienced by the surgeon.
Tremor frequency is normally around 0-15 Hz, while the piezoelectric motors and optical sensors and can function precisely at 500 Hz. Tests were performed on a dry "phantom" material and a chicken embryo.
The study has been published in Optics Express, the Optical Society's journal.