Circle Cardiovascular Imaging

AI modules inside an established reading platform. cvi42 is Circle's cardiovascular imaging software, spanning cardiac MR, cardiac and vascular CT, interventional planning and electrophysiology, with StrokeSENS for acute stroke. Machine learning drives specific modules, including the cvi42 Coronary Plaque Software Application, whose semi-automated algorithms segment coronary vessels and lumen for plaque quantification (K251027). The platform's value as a multi-vendor reading and reporting workstation stands without any one algorithm. AI central to features of a broader product that carries value without it.

An interactive tool the physician drives and edits; no published limits or error path beyond the indication. The cvi42 Coronary Plaque 510(k) summary (K251027) describes semi-automated machine learning for adults, for cardiac CT only, used by qualified professionals experienced in cardiovascular CT as part of a comprehensive diagnostic decision. Clinicians review, adjust and approve the generated contours, and cvi42 version 6.5 (August 2026) added editable plaque segmentation.

Analysis runs locally, so the clinician works the case directly rather than receiving a finished report. Nothing is published on which patients or scans the algorithms should not be used on, or on what happens when an output is wrong.

The models, their locking and their validation design are described; training data composition is not. Circle says its models are convolutional neural networks classifying cardiac structures at pixel and voxel level, trained by supervised learning on expert annotated data in its own research environment, then locked and encrypted at integration, so they do not learn from data at the customer site.

The cvi42 Coronary Plaque 510(k) summary (K251027) states that the machine learning segments coronary vessel and lumen walls, that the algorithms were trained and tested on images from the major CT makers, and that validation data came from multiple US sites and was not used in development; outputs that are not machine learning were verified separately. Versions are released and documented (cvi42 6.5, August 2026). Training data size and composition are not given; the company describes the data only as diverse and representative.

A short chain: the vendor's own locked models running on the customer's hardware. Circle trains its models in its own research environment and locks them at integration, so no outside model provider sits in the path, and on-premise deployment means the hospital hosts the software and the data. The 510(k) summary for cvi42 Coronary Plaque (K251027) reports software composition analysis of the third party components in the build. There is no software bill of materials, and nothing says whether any cloud or portal service handles images or who can reach an installation for remote support.

The plaque module's measurements are validated for clearance; the risk and care claims it is sold on rest on the literature for plaque analysis in general. The cvi42 Coronary Plaque 510(k) summary (K251027) reports segmentation and plaque volume agreement with three expert annotators on held-out US data. The product page's headline, quantified risk and personalized care, cites category studies such as SCOT-HEART, CONFIRM, PARADIGM and SCCT consensus rather than any study of cvi42 Plaque. The wider cvi42 platform has a long research record in cardiac MR, which does not validate the plaque module. Evidence that does not reach the product's own claims.

The architecture answers the stewardship questions: patient data stays with the hospital and the models do not learn from it. Circle states that image data and derived results are managed locally on a hospital workstation or customer managed server, that coronary analysis runs without sending patient data to an external reading service, and that its models are locked at integration and do not learn from customer data or from users' edits, treating each analysis in isolation.

Its quality system follows ISO 14971 risk management and IEC 62304, and the plaque module's clearance included threat modeling, vulnerability and penetration testing, and a post-market cybersecurity plan (K251027). The site does not say how remote support reaches an installation, or whether any web viewer or portal component moves images outside the hospital.

The product is scoped so the vendor does not receive patient data, which the company states; HIPAA and business associate status are not addressed by name. Circle says image data and derived results stay on a hospital workstation or customer managed server, with no patient data stored or sent outside the institution by the software, so for on-premise use the relationship a business associate agreement governs may not arise.

The statement appears in company articles rather than a contract or privacy instrument, and it does not cover remote support access to an installation or browser-based viewer components. The scope of the service keeps protected health information with the customer, stated by the vendor.

Product security testing is described in the regulatory filing; no organizational certification or trust portal is published. The cvi42 Coronary Plaque 510(k) summary (K251027) says the module was built to FDA cybersecurity guidance using threat modeling, software composition analysis, static analysis, vulnerability testing and penetration testing, with a post-market cybersecurity risk management plan.

The company describes TLS for client-server connections, directory-based user management over encrypted LDAP or Active Directory, and encrypted models. No SOC 2, ISO 27001 or HITRUST certification, named penetration tester or trust portal is published. Because the software runs inside the hospital, the customer's controls govern data at rest, which lowers vendor-side exposure but does not replace assurance over installed software. The one outside check is FDA's premarket review of the module's cybersecurity, which covers the product rather than the company.

Clearances are published by number, and the plaque module's own clearance is identifiable. Circle's regulatory page lists FDA 510(k) clearances for cvi42 (K251027 and K242781, with earlier K241038, K232661, K213998, K141480, K111373 and K082628) and for StrokeSENS (K250221, K212261), along with registrations in Canada, the EU under MDR, Australia, Japan, South Korea, Taiwan, Singapore, Malaysia, India, China, Brazil, Mexico, Colombia, Argentina, El Salvador, Saudi Arabia, the UAE, Thailand, Indonesia, South Africa and Israel.

K251027 is the cvi42 Coronary Plaque Software Application (21 CFR 892.2050, product code QIH, cleared October 2025), with semi-automated machine learning indicated for adults' cardiac CT. The page does not map every clearance to a module, and the company notes that not all modules are available in every region.

Specific statements on how the models behave in the field, and groups named without counts or figures. Circle states that its models are locked and encrypted at integration, do not learn from data processed at a customer site or from whether users edit outputs, and treat each analysis in isolation, so behavior is fixed between releases; clinicians review, adjust and approve contours.

The cvi42 Coronary Plaque 510(k) summary (K251027) says performance was consistent across scanner vendor, tube current, resolution, slice thickness, patient age, sex, vessel location and plaque volume, without giving the number of cases in any group or the results by group, and all validation data came from US sites. Training data is described only as diverse and representative. No bias policy or external AI governance credential is published. The commitments on field behavior are specific; the bias disclosure is far thinner.

Agreement figures and a review path are published, but without the number of cases, and nothing stands behind the output. Circle's 510(k) summary for the cvi42 Coronary Plaque Software Application (K251027) compares its machine learning segmentation with a reference from three expert annotators on held-out data from multiple US sites: lumen Dice 0.76, wall Dice 0.80, and plaque volume correlation of 0.97 (total), 0.99 (calcified), 0.93 (noncalcified) and 0.74 (low attenuation).

It does not state how many patients or studies were tested, so a buyer has no denominator. Clinicians review, adjust and approve contours, plaque segmentation is editable from version 6.5, and the models are locked between releases so results are reproducible for the same input. The company also calls its results accurate and reproducible without a scan-rescan or cross-site figure. No warranty, indemnity or remediation commitment is published. Mechanisms and figures with nothing behind them.

Vendor-neutral imaging software on DICOM, with named deployments; record system integration is not described. cvi42 reads DICOM from all major CT and MR makers and is stated to fit into existing CT workflows, which matters in cardiac imaging where many analysis packages are tied to one scanner maker; customers include Johns Hopkins. Circle lists partner integrations on its site.

No electronic health record integration, results interface (HL7 or FHIR) or named PACS vendor is described in what the plaque materials publish. Scanner compatibility is a different question from how results reach the chart. Standards support with named deployments.

On-premise, with the processing path and location stated. cvi42 Plaque runs inside the institution, on a hospital workstation or customer managed server, and the company states coronary analysis happens without sending patient data to an external service; image data and derived results are managed locally. That settles where data is processed and stored and keeps it isolated from other customers by design, and there is no queue behind the analysis. It is not stated whether any cloud, web viewer or portal component forms part of a deployment, or how remote support connects.

No price or pricing basis is published; the payer side is documented. Circle publishes a coding and reimbursement guide and a reimbursement calculator, and describes Medicare payment for AI plaque analysis of CCTA (US$950 under Category III code 0625T, moving to a permanent Category I code from January 2026) and higher base payments for the CCTA exam.

Those describe what a provider can bill, not what Circle charges: no license, seat, site or enterprise price is published, and the route in is a conversation. An on-premise license with local hardware would make cost fixed rather than per study, but that is not stated. No price, with how the product is paid for discoverable.

Broad cardiovascular coverage, named module by module, with validation shown for part of it. cvi42 covers cardiac MR (function, flow, tissue, strain, 4D flow, perfusion), cardiac CT (coronaries, plaque, pericoronary fat, calcium, function, strain), vascular CT, structural heart planning, electrophysiology planning and, through StrokeSENS, acute stroke, serving cardiology, radiology and imaging centers including specialized programs such as adult congenital heart disease.

The plaque module's clearance limits it to adults' cardiac CT and its validation used US data only, and the company says not all modules are available in every region. Validation by setting for the other modules is not set out on the product pages. Named coverage with validation behind part of it.