What Is PACS?
PACS stands for Picture Archiving and Communication System. It is the software and infrastructure that hospitals, imaging centers, and teleradiology networks use to store, retrieve, and distribute medical images — X-rays, CT scans, MRIs, ultrasounds, and more — in the DICOM format. Before PACS, radiology departments printed images on film and physically moved them between departments. A PACS replaces that workflow with a digital archive that any authorized clinician can query from a workstation or a browser, anywhere on the network.
How a PACS Works, Step by Step
The flow behind every PACS is the same five steps, regardless of vendor. 1. Acquisition — a modality (CT, MR, X-ray, ultrasound) generates a study and sends it to the PACS using the DICOM C-STORE protocol. 2. Ingest and indexing — the PACS receives the study, validates it, and indexes it against patient and order metadata (often synchronized from a RIS or HIS via HL7). 3. Storage — the study is written to the archive, typically with redundant storage and a defined retention policy. 4. Query/Retrieve — a radiologist's workstation or a web viewer queries the PACS (DICOM C-FIND/C-MOVE, or DICOMweb over HTTPS) to pull the study back for reading. 5. Distribution — the finalized report and, where needed, the images themselves are shared with referring physicians, other facilities, or the patient.
Cloud PACS vs. On-Premise PACS
The core DICOM workflow above is identical whether the archive runs in a hospital's own server room or in the cloud — the difference is where the data lives and who manages the infrastructure. An on-premise PACS keeps images on local servers inside the hospital network. It gives full control over data residency and works well for a single site with existing IT staff, but scaling storage or adding a second site means buying and maintaining more hardware. A cloud PACS centralizes storage and lets any authorized site or device reach the archive over HTTPS, without VPN tunnels between buildings. Capacity scales on demand, uptime is backed by an SLA instead of local hardware, and rolling out a new clinic is a configuration change rather than a hardware purchase. Many networks run both: a cloud PACS for cross-site sharing and disaster recovery, with an on-premise archive at high-volume sites for local performance.
What a Good PACS Delivers
Independent of deployment model, a PACS worth using should deliver: - Fast retrieval — sub-second study opens for recent exams, with prefetching for scheduled reads. - Reliable uptime — a documented SLA (99.9%+) rather than best-effort availability. - Role-based access — radiologists, referring physicians, and administrators see only what their role permits. - Interoperability — DICOM Query/Retrieve, DICOMweb, and HL7/FHIR connections to the RIS, EHR, and reporting system, so the PACS isn't an isolated silo. - Auditability — a full access log for every study, required for HIPAA/KVKK compliance and for tracing who viewed or exported an image.
What to Check Before Choosing a PACS
A handful of questions separate a PACS that scales with a growing imaging network from one that becomes a bottleneck: - Does it support multi-site deployment with centralized administration, or does every site need its own instance? - Can referring physicians and patients open a study through a secure link without installing anything? - What's the actual retrieval time for a large study (e.g., a multi-series CT) under load, not just an idle demo? - Does the vendor publish an uptime SLA, and what's the remedy if it's missed? - How does the archive handle long-term retention and storage tiering as volume grows year over year?
PACS at PING DICOM
PING DICOM's Cloud PACS and On-Prem PACS share the same DICOM/HL7 core described above, so a hospital network can run either — or both — without changing how radiologists work. Multi-site deployment, role-based access, automatic retrieval, and a 99.95% uptime SLA are built in rather than bolted on. See how it fits your network on the Cloud PACS and On-Prem PACS pages, or talk to us about a specific deployment.