Designing for Value

A core part of the value proposition of the TULSA-PRO is delivering precise prostate ablation under real-time MRI guidance. To accomplish this, the Profound Medical team needed to integrate their software with that of major magnetic resonance imager manufacturers. They also needed to develop a detailed and robust controls scheme to enable the user to precisely deliver exactly the dosage of energy necessary for the treatment.

Buying the motor assembly from MICROMO let the Profound Medical design team focus their efforts on these important integration and controls activities. “It’s a modular unit that we just basically use as is,” says Yeung. “Again, because it’s pre-packaged, it takes up very little space. All we need to do is worry about designing the mechanical and electrical interfaces. Then we just let the motor do its job.”

Inside the Solution

To safely and accurately position the ultrasonic probe in an MRI environment, the Profound Medical team turned to piezoelectric motors.

  • For the angular positioning: the LR50 rotary nonmagnetic operates over an angular range of up to 360° at a top speed of 100°/s, and with a resolution of better than 0.1 μrad. It provides a torque of 50 mNm (higher torques can be achieved with appropriate preloads) and a holding torque of 55 mNm. Built with nickel-copper alloy housings, these 23-mm-diameter, 27.7-mm-long motors weigh just 60 g.
  • For linear positioning: the LT20 linear nonmagnetic motor. This motor operates over a linear range of up to 100 mm. These 10.8-mm-diameter, 22-mm-long motors weigh 34g.
  • To drive the motors: the PMCM31 is an analog motor driver that provides a 12 VDC 0.3 A supply voltage and ± 9.6 V DC control voltage.

The motor module also helped them achieve another goal, which was to build a reliable, user-friendly device that is economical enough for state-of-the-art teaching hospitals and local clinics alike. “From a price point of view, we would like to reduce the cost as much as possible while maintaining the quality and the functionality of the device,” he says. “So that goes back to finding components that are prepackaged, modular, and ready to be included. We also need them to be reliable so that we’re not fixing the system over and over.”

The MRI magnet room components of TULSA-PRO consist of an ultrasound applicator that delivers the therapeutic dose to the patient, the robotic positioning system of the applicator, and the interface box that includes power and drive electronics for the positioner. (Credit: MICROMO)

Buying a modular subassembly from MICROMO that already includes the modifications doesn’t just simplify the engineering process, it positions Profound Medical for volume production. “[Using other piezoelectric motors] definitely involves a lot of engineering effort to integrate the technology into the existing design, and also manufacturing, as well,” Yeung says. “If the design and manufacturing [teams] only need to worry about very modular, really simple interfacing, that saves a lot in terms of effort and also time, as well, when we push this technology to market.”

TULSA-PRO is currently CE Marked but is not yet FDA approved for use in the United States. In the Phase I clinical trial, TULSA-PRO demonstrated accurate and precise ablation of targeted prostate tissue. It also demonstrated a favorable safety profile with minor impact on urinary, erectile, and bowel function at 12 months. Profound Medical is now beginning a broader trial involving more than 100 patients. In the meantime, Yeung and his team are already considering next-generation designs, and they expect MICROMO to be a part of that effort.

This article was written by Mike LeBlanc, Application Engineering Team, MICROMO, Clearwater, FL. For more information, Click Here .