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Regulatory Challenges for the New Frontier of Medical Imaging: Terahertz Spectrum

Emerging medical imaging technologies being developed for the terahertz spectrum may face regulatory hurdles from an unexpected Federal agency: the Federal Communications Commission (FCC). While the Food and Drug Administration (FDA) has jurisdiction over medical devices with respect to safety and effectiveness – including premarket approval, inspection of manufacturing facilities, and monitoring of post-market adverse events – the FCC has jurisdiction over certain technical and spectrum use requirements for medical devices that operate on radiofrequency (RF) spectrum. Medical device developers need to be aware of the current state of play at the FCC in these areas.

Terahertz Imaging

Medical imaging technologies can operate on a variety of frequency bands. In the terahertz frequency range, the waves are extremely short, smaller than the size of a cell. When these radio waves are sent through tissue, the signal passes through the tissue and creates “scattering.” (Atoms are “shaken,” but not broken or destroyed.) Imaging in the terahertz frequencies can reveal what is occurring at the cellular level, providing the ability to distinguish between cells that have cancer or not, for example, or between different types of cells such as fatty tissue or liver tissue. Obviously, these are promising diagnostic methods that could enhance the detection and treatment of pathological conditions, such as skin cancer.

The Basics of FCC Regulation of Medical Devices

The FCC regulates several aspects of wireless medical devices. These include: 1) issuing test licenses to designers and manufacturers to test devices prior to approval; 2) issuing grants of equipment authorizations, or otherwise providing mechanisms for allowing device use; 3) setting out rules for the use of frequencies designated for medical devices; 4) establishing new frequencies for use by wireless medical devices; and 5) imposing requirements for ascertaining and complying with limits on human exposure to RF energy.

The spectrum managed by the FCC is commonly used for communications, such as cellphones, Wi-Fi and radio, with FCC currently regulating the frequency range from 3 kHz to 3000 GHz. (Frequency refers to the wavelength of the radio waves passing through the air. Radio waves can range in size from 100 meters at the lower frequencies to decimillimeters at the highest frequencies. The size of the radio wave determines the use of a frequency range.) Terahertz spectrum falls at the top end of the regulated frequency range, just below light waves on the electromagnetic spectrum – specifically, 300-3000 GHz.

The FCC Provides for Only Limited Operations on Terahertz Spectrum

The FCC does not have service rules in place to allow for operations in the terahertz bands. In fact, FCC presently only has service rules (i.e., rules for use) up to 95 GHz, and only has spectrum allocated (i.e., planned out for use) up to 275 GHz. Because spectrum is a finite resource, the FCC must plan its use to ensure that multiple users can co-exist.

The FCC currently has an open rulemaking proceeding that proposes to establish new rules for operations beyond the 95 GHz range, but only up to 275 GHz (just below the terahertz range). The only proposal that the FCC has made thus far with regard to use of the terahertz range is to provide for testing licenses in that range, with the possibility of allowing very limited sales of new technologies.

Absent service rules, medical imaging devices operating in the terahertz frequencies may only be marketed if they can be categorized as “Industrial Scientific and Medical (ISM)” equipment. And even then, the FCC employs a “case-by-case” evaluation of each device, which means that designers and manufacturers cannot design to specific technical rules, but instead must wait until the FCC evaluates their product before knowing whether they will receive FCC authority to market the device. This process obviously creates a good deal of regulatory uncertainty. Moreover, it does not apply to devices that have a communications function, such as Bluetooth or Wi-Fi used to send data collected by the device to a smartphone or router.

Europe and Japan are both ahead of the U.S. in terms of planning for the use of terahertz frequencies. Until FCC modifies its rules, and proposes new rules for the terahertz range, the effect will be to discourage capital formation for developers of medical imaging technologies that could operate in those frequencies. Advocacy is needed to press the FCC to clarify and establish rules to allow for medical imaging devices that operate in the terahertz ranges. Providing feedback on the current FCC proposal should be the start of this effort, but certainly not the end of it.

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