Medical Imaging Regulations & Classifications

Medical imaging devices are regulated differently depending on their technology, intended use, and country of use. In the United States, the FDA generally classifies medical devices as Class I, II, or III according to risk. Class I devices are subject primarily to general controls, Class II devices to general and special controls, and Class III devices to the most stringent controls, including Premarket Approval (PMA) when applicable.

MRI — Magnetic Resonance Imaging

United States: MRI systems are regulated by the FDA as medical devices and are generally subject to Class II requirements and premarket controls. MRI does not use ionizing radiation, but regulations and standards address magnetic fields, radiofrequency energy, heating, labeling, and safety. The FDA also recognizes standards addressing MRI image quality and RF-coil heating.

International: In the European Union, MRI equipment is regulated under the Medical Device Regulation (MDR). In the United Kingdom, medical devices are regulated by the MHRA, while Australia's TGA regulates medical devices using risk-based classification rules. Canada regulates MRI equipment through Health Canada. International standards such as IEC standards are commonly used to address MRI safety and performance.

CT — Computed Tomography

United States: CT scanners are regulated by the FDA as medical devices and are generally subject to Class II controls. Because CT uses ionizing X-rays, it is also subject to radiation-emitting equipment requirements, including performance, safety, labeling, and quality-control considerations.

International: The EU MDR regulates CT equipment as medical devices, while national radiation-protection requirements may also apply. The UK's MHRA oversees medical-device requirements, with additional radiation regulations applying to X-ray equipment. Australia's TGA regulates CT systems using risk-based medical-device rules. Canada combines Health Canada medical-device requirements with applicable radiation-safety regulations.

Ultrasound

United States: Diagnostic ultrasound equipment is regulated by the FDA as medical devices. Regulation focuses on device performance, electrical and acoustic safety, labeling, and intended clinical use. Unlike CT and PET, diagnostic ultrasound does not use ionizing radiation, but acoustic output and thermal and mechanical effects are important safety considerations.

International: Ultrasound devices are regulated under the EU MDR, UK medical-device regulations administered by the MHRA, Canada's Health Canada framework, and Australia's TGA system. International IEC standards are commonly used for ultrasound safety and performance. Additional professional and national guidance may apply depending on the clinical application.

PET — Positron Emission Tomography

United States: PET systems are regulated by the FDA as medical devices, while the radioactive materials used for PET are subject to additional regulation. PET therefore involves both medical-device regulation and radiation/nuclear-material regulation. Radiopharmaceuticals are regulated separately from the imaging scanner, with federal and state requirements potentially applying to their production, handling, and use.

International: PET is similarly subject to multiple regulatory systems because it combines medical imaging equipment with radioactive materials. The EU regulates the device under the MDR while radiation protection and radioactive substances are addressed through additional European and national requirements. The UK, Canada, and Australia also regulate PET equipment and radioactive materials through separate but complementary frameworks.

fNIRS — Functional Near-Infrared Spectroscopy

United States: fNIRS does not use ionizing radiation and generally falls under the FDA's medical-device framework when marketed for a medical purpose. Its classification depends heavily on its intended use and specific claims. Research-use systems may be treated differently from devices intended to diagnose, monitor, or treat a medical condition.

International: fNIRS devices are regulated according to their intended medical purpose under frameworks such as the EU MDR, UK MHRA system, Canada's Health Canada framework, and Australia's TGA system. Because fNIRS technology is relatively specialized and can be used for both research and clinical applications, its regulatory classification may vary considerably depending on the device's claims and clinical purpose.