An LED polarimeter is described which is suitable for measuring the stress in photoelastic materials. The rotor is magnetically driven to produce rotary motion of the impeller for pumping blood. The device can be removed by gripping a portion of the device with a retractor device, which is used to draw the device proximally. The antennas can be low-profile planar antennas, either linearly or circularly polarized, which can be advantageously mounted to a housing while limiting undesirable contact with the environment and therefore to limiting the potential for damage. The actuator module is mounted to the mirror support. The invention also relates to the therapeutic use thereof.