Active implantable stimulating device for use with an mri-device

A system for visualizing by a magnetic resonance imaging (MRI) technique including a functional magnetic resonance imaging (fMRI) technique, regions of a central nervous system of a patient (51) having an implanted active implantable medical device (AIMD) (1), the system comprising:

• a kit-of-parts according to any one of the preceding claims, wherein the AIMD is implanted in the patient with the implanted source of communication light (20Li) and the implanted communication photodetector (20Pi), facing towards an area of skin of the patient,
• a magnetic resonance (MR) device (200) located in a Faraday cage (220), for generating magnetic resonance images (MRI) or spectra (MRS), including functional magnetic resonance images (fMRI) or spectra (fMRS) of a central nervous system of the patient, a control room (210) located outside of the Faraday cage, and enclosing,
• the external processing unit (100),
• the external communication unit (102), in wireless communication or in wire or optical communication with the external processing unit (100),
• an MR controller (201) for controlling the functions of the MR-device,
• a cage feedthrough (103) configured for providing a continuous optical communication through each of the one or more optical fibres (104f) of the optical communication lead (104) between,
• a proximal end coupled to the external communication unit (102) and located in the control room, and
• a distal end located in the Faraday cage, and coupled to the area of skin of the patient, in good alignment with the implanted source of communication light (20Li) and/or the implanted communication photodetector (20Pi) of the encapsulation unit (5),
• whereby the external processing unit (100) is in two-way communication with the electronic circuit (5e) of the encapsulation unit (5) for transferring parameters and commands to the electronic circuit, and for displaying information sent from the implanted source of communication light (20Li).

An active implantable medical device (AIMD) (1) for implantation in a body of a patient (51), comprising the following units:

• an encapsulation unit (5) defining an inner space (Vi) sealingly separated from an outer environment by walls defined by an inner surface defining the boundaries of the inner space, wherein the walls of the encapsulation are made of a ceramic material, wherein the inner space contains:
• an implanted source of communication light (20Li) and an implanted communication photodetector (20Pi) facing a portion of wall having a transmittance to wavelength of 500 to 1200 nm for optical communication with an exterior of the body,
• a main source of light emission (10L) of a given wavelength range comprised between 380 and 2200 nm and/or an implanted sensing photodetector (10P) facing a window having transmittance to the wavelength range, wherein the main source of light emission (10L) is configured for sending pulses of light energy according to defined parameters, and wherein the implanted sensing photodetector (10P) is configured for receiving optical signals,
• an electronic circuit (5e) for controlling the implanted source of communication light (20Li), the implanted communication photodetector (20Pi), the main source of light emission (10L), and the implanted sensing photodetector (10P),
• a tissue interaction unit (6) separate from the encapsulation unit, and configured for interacting with a tissue,
• an energy transfer lead (4) comprising an optical fibre having a proximal end coupled to the encapsulation unit (5) and facing the window of the encapsulation unit in alignment with the main source of light emission (10L) and/or with the implanted sensing photodetector (10P), and a distal end coupled to the tissue interaction unit, the energy transfer lead comprising no electric conductive wire,
• Characterized in that, the AIMD fully immersed in a phantom (452) yields a specific absorption rate (SAR) normalized to a background level of the phantom of not more than 4.0 dB, preferably nor more than 3.5 dB, more preferably not more than 3.2 dB, upon exposure to the following conditions,
• the phantom is maintained at a constant temperature and is composed of a tissue simulating medium having an electrical conductivity of 0.47 S/m and a relative permittivity of 78,
• the phantom is placed inside a birdcage resonator compatible with ISO/TS 10974:2018 configured for exposing the implant fully immersed in the phantom at a depth of 65 mm to a magnetic field (B) oscillating at a frequency of f=64 MHz and inducing a constant tangential field (E) of 36.31 V_rms/m, and wherein
• the SAR is measured with sensors (4s-6s) positioned at 2 mm of the AIMD for measuring the SAR of the encapsulation unit, of the energy transfer lead, and of the tissue interaction unit, and wherein the specific absorption rate (SAR) is the highest of the values measured at the three main components.