With adjustable valves, the possibility is offered of adjusting the operating pressure non-invasively, to match an individual patient’s changing clinical needs. Developed with the Sophy® valve, the Sophysa adjustment principle is based on the pressure variation exerted on a ruby ball by a flat, semi-circular spring at different points on its curvature. The spring is attached to a magnetic rotor which is able to pivot inside the valve body. The operating pressure of the valve is determined by the angular position of its rotor. This angular position can be changed thanks to an adjustment kit. However, the rotor position can sometimes be altered under the action of a magnetic field for instance. A standard adjustable valve could then experience unexpected pressure dysadjustments. Sophysa developed a magnetic lock of the rotor to prevent these dysadjustments. This magnetic lock allows Polaris® to be the first MRI-stable adjustable valve in the World.