FDA creates a device class for focused-ultrasound tissue ablation

The Food and Drug Administration has written a brand-new category into its device rules for machines that destroy soft tissue with focused sound waves rather than heat. A final order published in the Federal Register on 6 October 2026 classifies the "focused ultrasound system for non-thermal, mechanical tissue ablation" into Class II, with special controls, and codifies it at 21 CFR 878.4405 [s1]. The order is effective 6 October 2026, though the underlying classification was applicable from 6 October 2023 [s1].

The technology at issue is often called histotripsy: instead of cooking tissue, the device uses pulses of focused ultrasound to mechanically break it apart. The FDA's own definition of the new generic device type is a device that "uses focused ultrasound to mechanically ablate soft tissue," adding pointedly that "the device is not intended to thermally ablate tissue" [s1][s2]. That distinction is the whole reason a new category was needed — existing thermal-ablation categories did not describe it.

How the category came to exist

The order is the end of a process that began with a single company. On 2 December 2022, the FDA received a De Novo classification request from HistoSonics, Inc. for its Edison System [s1]. The De Novo route exists for genuinely novel devices that have no legally marketed predicate to compare against. Any device that was not in commercial distribution before 28 May 1976 is, by operation of law, dropped into Class III — the agency's most tightly regulated tier, normally requiring premarket approval — regardless of how risky it actually is [s1]. De Novo lets a sponsor ask the FDA to assign a lower class when general and special controls can reasonably assure safety and effectiveness [s1].

That is what happened here. On 6 October 2023 the FDA granted the request and classified the Edison System into Class II [s1]. The order published this week is the formal step of adding the device type to the Code of Federal Regulations, under product code QGM [s2]. The agency says it reviewed the request and determined that special controls, combined with the general controls that apply to all devices, provide a reasonable assurance of safety and effectiveness [s1].

What the special controls require

The order sets out the hazards the FDA sees and the testing it will demand to mitigate them. The identified risks to health include impaired tissue or organ function, abscess or pain downstream of ablation; injury to non-targeted tissue along the acoustic path; tissue injury from device malfunction or misuse; adverse tissue reaction; and electrical shock or electromagnetic interference [s1]. Against those, the special controls require clinical performance testing, animal and non-clinical performance testing, software verification and validation with hazard analysis, biocompatibility evaluation, electrical safety and electromagnetic compatibility testing, labelling and human-factors testing [s1].

Crucially, Class II status does not exempt the device type from premarket review. The FDA states it has not determined that these systems should be exempt from premarket notification, so a maker bringing one to market must still clear a 510(k) [s1].

Why a single classification matters beyond one company

The quietly significant part of the order is what it does for everyone else. Once the FDA classifies a device into Class I or II through De Novo, that device can serve as a predicate for future devices of the same type [s1]. In practice that means a competitor no longer has to run its own De Novo request or a full premarket-approval application; it can use the less burdensome 510(k) pathway to show its device is substantially equivalent to the now-classified type [s1]. The agency says explicitly that it expects the classification to "enhance patients' access to beneficial innovation" by lowering the regulatory barrier for follow-on products [s1].

That is the mechanism by which one company's novel clearance becomes an industry-wide on-ramp. Having established the category on the back of the Edison System, the FDA has turned a one-off approval into a reusable regulatory template — the point at which a new modality stops being a single product and becomes a field. The order also notes the agency's support for the "3Rs" of replacing, reducing and refining animal testing, and encourages sponsors to propose validated non-animal methods where feasible [s1].

This article describes a device-regulatory action, not medical advice. Whether focused-ultrasound ablation is appropriate for a given condition is a clinical decision for patients and their treating specialists.

Sources

• Medical Devices; General and Plastic Surgery Devices; Classification of the Focused Ultrasound System for Non-Thermal, Mechanical Tissue Ablation — U.S. Food and Drug Administration, published 6 October 2026
• Device Classification: Focused Ultrasound System For Non-Thermal, Mechanical Tissue Ablation (product code QGM, 21 CFR 878.4405) — U.S. Food and Drug Administration (openFDA device/classification API)