Medical Integrations and Standards — HL7, FHIR, DICOM, PACS

HL7 (Health Level Seven) is an international family of standards for exchanging medical information between systems. Its most common version, HL7 v2, defines a message structure for events such as patient admission, test orders or lab results, so different systems can communicate in an agreed language without depending on a single vendor.

At CareOS: lab results are received via HL7 v2, with out-of-range values flagged.

FHIR (Fast Healthcare Interoperability Resources) is a newer standard within the HL7 family, built on web interfaces (REST) and structured resources such as Patient or Observation. While HL7 v2 relies on text messages, FHIR uses JSON or XML and suits modern apps and mobile. Both belong to HL7; FHIR is more recent and web-oriented.

DICOM (Digital Imaging and Communications in Medicine) is the international standard for storing and transmitting medical images — X-rays, ultrasound, CT and more. A DICOM file holds both the image and metadata about the patient and study, so any standard viewer displays it consistently regardless of the device manufacturer.

At CareOS: DICOM items appear in a unified media tab per patient, in a federation model — the source stays in place and viewing is centralized.

PACS (Picture Archiving and Communication System) is a system for storing, managing and distributing medical images. It typically keeps DICOM files centrally and provides access and a dedicated viewer, replacing physical film. PACS is a general industry concept and is not necessarily required by every clinic.

Not necessarily. The need depends mainly on imaging volume and type. Common options:

• a clinic with little imaging often does not need a full PACS;
• cloud storage or an external imaging service;
• a federation model where images stay at their source and viewing is centralized.

At CareOS: viewing of DICOM items is centralized in the media tab using a federation model, so display can be consolidated without moving the source.

In general, the imaging device produces DICOM files that include patient and study identifiers. The files are sent to storage and a viewer and linked to the patient record by those identifiers. The Modality Worklist standard lets the device pull patient details in advance, reducing manual entry and matching errors.

At CareOS: DICOM items are shown together in the media tab per patient, and every open is recorded in the audit log.

Mismatches are prevented mainly through layers of identification and control:

• verifying patient identifiers at check-in and at capture;
• using a Worklist instead of free typing;
• checking the DICOM file metadata against the record;
• an access log recording who viewed and when.

At CareOS: every media open is recorded in an audit log with an integrity signature on each line.

A lab connection is usually made through HL7 v2 messages: the test order is sent from the system, and results return as a structured message received automatically into the patient record. This avoids double entry and reduces errors. The exact link depends on the interface the laboratory provides.

At CareOS: tests are ordered from the visit, and results are received via HL7 v2 with out-of-range values flagged.

When an interface is temporarily unavailable, continuity mechanisms are typically used so no information is lost:

• a message queue and re-sending once the link is restored;
• continuing work with manual entry as a fallback;
• alerting staff and holding results until fully received.

Good to know: these are general industry principles; the exact behavior depends on each system and interface implementation.

An open format lets data move between systems without vendor lock-in. In healthcare, HL7 and FHIR are common for clinical data, DICOM for imaging, alongside general formats such as CSV or PDF for documents. Actual capability depends on what each system offers.

Good to know: specific export capabilities — scope, formats and terms — should be checked with the vendor.