The Path to Creating a More Person-Friendly Medical World
Nearly 20 years have passed since endoscopic surgery was introduced. During that period, endoscopic surgery has evolved as a surgical technique. Equipment has gone through many stages of R&D, yet few improvements have been made. Now, endoscopic surgery is entering new phases, including natural orifice transluminal endoscopic surgery, single-hole laparoscopic surgery, and surgery using robotic arms. However, one thing all operative procedures have in common is that they are technologically advanced and less invasive to patients. Patients are also seeking relief from pain, early recovery after surgery, and early rehabilitation. This indicates that there is a need and desire for health care that is focused on quality of life, and it should be considered as a basic guideline in the development of medical technology. Therefore, the need for less-invasive medical devices will continue.
The Need for a Smaller-Diameter UAS
In recent years, because of improvements in the size of the trocar and other devices that are inserted into a patient, the sizes of incisions have become smaller. Now, single-hole laparoscopic surgery is readily carried out, but there is a need for further minimizing the diameter of the insertion tool. Johnson & Johnson developed, and successfully commercialized, a 3 mm bipolar forceps (electric scalpel), which was once considered impossible.
Further Sophistication of Surgical Tools Is a Key to Cutting-Edge Health Care
Currently, as medical procedures advance, highly advanced medical technology is expected to be implemented. Some of the areas demanding better surgical equipment include fetal surgery (prenatal treatment) and regenerative medical techniques. Because of this, the physiological and biological engineering laboratory at Nihon University decided to develop a “needle-type ultrasonic scalpel” in collaboration with NITI-ON Co., Ltd., a company that has a track record of developing small-diameter endoscopic tools, and Peritec Co., Ltd. This project was adopted and supported by the “Supporting Project for Sophistication of Strategic Infrastructure Technology” (a.k.a., Supporting Industry) conducted by the Ministry of Economy, Trade, and Industry (H23-25).
The goal for this project was to improve the safety and the operability of the tool (a diameter smaller than 3 mm) by adding a function to switch on or off the current based on the signals from a contact sensor, and a function to sense the minimum required output value to simultaneously dissect through tissues and seal blood vessels. Because such a development was the first of its kind, a similarly unprecedented development system was required.
We needed to address three major challenges when developing a new, ultrasmall-diameter, sophisticated UAS. First, we needed a flexible measurement and control system that could be used more for R&D. The conventional methods for developing the UAS and the associated ultrasonic machining involved techniques—such as impedance measurements similar to LCR circuit elements, measuring the amplitude of the front-end oscillation, and measuring the drive power of the supply circuit in line with the power consumption—that have not changed since the 1970s. Additionally, there was not a precedent for a measurement and feedback control system that takes into consideration mass load and stiffness load on the ultrasonic resonator and nonlinear phenomena present in high-power drive. Therefore, we needed a flexible system in order to build a development approach through trial and error and reduce development time.
Second, we also needed to measure and control all signals with a wide dynamic range, varying from low voltage to driving voltage (up to 200 Vpp). Lastly, while meeting the first two requirements, we also needed to gather data following a standard for quality and security that is required for filing for the approval from PMDA in Japan, which is key in developing medical devices.
We developed three different systems. The first lower-level, stand-alone system was developed to file for approval from the PMDA. This system was controlled by GPIB and measures the quality of the piezoelectric drive system. This system controls an existing impedance measurement system.
The midlevel system was our first PXI-based system that we developed to tackle the first challenge described in the previous section. We built the midlevel measurement and control system using the same PXI platform by combining an NI PXI-5412 arbitrary waveform generator and an NI PXIe-5122 high-speed digitizer in parallel with the lower-level GPIB measurement system. Using the same measurement system assured compatibility for research and development. The third system we developed was the upper-level, FPGA-based system. The FPGA-based system integrated the low-level (stand-alone) system and the midlevel PXI-based systems mentioned above, and also performs upper-level real-time measurement and control using the NI PXI-7854R R Series multifunction reconfigurable I/O device.
Ultrasonic vibration velocity was measured using a laser Doppler vibration meter and the optical measurement stage, which was developed solely for this project. Speed signal and video images were acquired through a microscope using the same PXI platform through an NI PXIe-5122 high-speed digitizer and a USB input, respectively. Furthermore, with regard to the second challenge mentioned above, we achieved our solution by incorporating a high-speed bipolar power supply (HSA4011 from NF Corporation) in the measurement system.
To ensure system quality, we made the system conversions from stand-alone to PXI-based to FPGA-based easy with the NI PXI platform and LabVIEW system design software; there was no other option for us.
First, we deployed a system configuration consisting of low-level (stand-alone), midlevel (PXI-based), and upper-level (FPGA-based) systems. From ensuring quality in developing medical devices and research and development to production, we used the same platform to tackle all of our challenges. All of the systems were programmed using LabVIEW, which made it extremely easy to convert to each new development system.
Lastly, we built the entire system (from stand-alone to FPGA-based) in about a week—an estimated 80 percent reduction in development time, which helped us accelerate our research and development. In fact, within a week after completion of the system, we completed the first phase of research and data acquisition and gave a presentation at an international conference . Additionally, the space required for research and development was reduced to one-third of what it was, and the system is now portable, if the need arises.
 Yoshinobu Murayama, Kenta Yoshida, Kenta Hattori, and Hiroshi Honda, “Minimum But Sufficient Ultrasound Power Sensing For Safe And Intuitive Ultrasonic Surgery,” SMIT2012 (24th International Conference of the Society for Medical Innovation and Technology), Barcelona, Spain, September 21, 2012.
Yoshinobu Murayama PhD
Department of Electrical and Electronic Engineering, College of Engineering, Nihon University