As hospitals use increasing numbers of CT, MRI, digital X-ray, ultrasound, and other imaging systems, the challenge no longer ends with generating diagnostic images. Healthcare facilities must also manage the data chain behind those images: where they are sent, how they are associated with the correct patient, how physicians access them, how long they are retained, how storage expands as data volumes grow, and what happens if the system or network fails.
This is the role of PACS – Picture Archiving and Communication System.
At a high level, PACS is a system used to receive, store, manage, retrieve, display, and distribute digital medical images and related data.
A typical workflow can be visualized as follows:
HIS/EMR → RIS → Modality Worklist → CT/MRI/X-ray… → PACS → workstation/viewer → report → HIS/EMR
An important distinction should be made from the beginning: PACS is not diagnostic imaging equipment. CT, MRI, X-ray, and other modalities generate imaging data; PACS manages that data and integrates it into the hospital's digital workflow.
What Is PACS?
A PACS may include:
- Application server.
- Database.
- Image archive.
- Storage.
- DICOM services.
- Diagnostic workstation.
- Clinical/web viewer.
- RIS/HIS/EMR integration components.
- Gateway or middleware where required.
- Backup and redundant systems.
- Administration tools and audit logs.
Not every product described as a “PACS” has the same scope.
One supplier may provide:
PACS + viewer + storage
while another solution may include:
RIS + PACS + reporting + archive + viewer + disaster recovery
Therefore, if a hospital compares only price without first standardizing the scope, it may actually be comparing two entirely different systems.
How Are PACS, RIS, HIS/EMR, and VNA Different?
| System | Primary Role at a High Level |
|---|---|
| HIS | Supports a wide range of overall hospital management workflows |
| EMR/EHR | Manages electronic medical records or health records within the scope of the system |
| RIS | Manages diagnostic imaging workflows such as orders, scheduling, status, and reporting |
| PACS | Manages, stores, retrieves, displays, and distributes images |
| Modality | Generates imaging data |
| VNA | An image/data storage layer that may be separated from a specific PACS depending on the architecture |
In practice, the boundaries are not always absolute.
A platform may integrate:
- RIS.
- PACS.
- Reporting.
- Worklist.
- Enterprise viewer.
while another hospital may use systems from several different vendors.
The important question is therefore not simply:
“Does the hospital have RIS or PACS?”
but rather:
“Which function resides in which system, and which system is the authoritative source for each type of information?”
How Does a Typical PACS Workflow Operate?
1. The Patient Is Registered
Patient information is created or confirmed in the HIS/EMR or another source system.
If the Patient ID or identifying information is incorrect at this stage, the error may propagate throughout the entire imaging workflow.
2. A Diagnostic Imaging Order Is Created
The order is sent to the RIS or imaging workflow management system for:
- Scheduling.
- Modality assignment.
- Examination preparation.
- Status management.
3. The Modality Receives the Worklist
CT, MRI, or other equipment may use DICOM Modality Worklist – MWL to receive prepared data from the system.
This helps reduce the need for technologists to manually re-enter:
- Patient ID.
- Patient name.
- Accession number.
- Examination information.
thereby reducing one potential source of data discrepancies.
4. The Modality Generates Images
The device generates DICOM objects containing images and related metadata.
5. PACS Receives and Stores the Images
PACS may:
- Receive studies.
- Create indexes.
- Update the database.
- Store images.
- Support query/retrieve.
- Provide data to viewers.
6. The Physician Accesses the Images and Creates the Report
Images may be opened through:
- Diagnostic workstation.
- PACS viewer.
- Enterprise viewer.
- Web viewer.
The report may reside in the RIS, an integrated RIS/PACS platform, or a separate reporting system.
7. Results Are Returned to the Hospital System
Clinicians may be able to access reports and images from the HIS/EMR when integration is appropriately designed.
What Is DICOM and Why Is It Important for PACS?
DICOM – Digital Imaging and Communications in Medicine is a standard for communicating and managing medical imaging information and related data.
DICOM covers areas such as:
- Storage.
- Query/Retrieve.
- Modality Worklist.
- MPPS.
- Storage Commitment.
- Structured Reports.
- DICOMweb.
- Metadata.
- DICOM object types.
- Transfer syntaxes.
A DICOM object is not simply an image file.
It may contain:
image/pixel data + metadata
such as:
- Patient ID.
- Study UID.
- Series UID.
- Modality.
- Study date/time.
- Other relevant attributes.
PACS therefore should not be understood as:
“A folder containing images.”
The system needs to preserve the relationship between:
Patient → Study → Series → Instance
“DICOM Compatible” Is Not Enough to Guarantee Integration
Two products may both state:
“DICOM supported”
but may still differ in:
- SOP Classes.
- Service roles.
- Object types.
- Worklist.
- Query/Retrieve.
- Storage Commitment.
- DICOMweb.
- Transfer syntaxes.
Hospitals should therefore request the DICOM Conformance Statement for both the PACS and the modality.
This document helps biomedical engineers, IT/PACS administrators, or integration teams compare:
What does the device need to send or receive?
with:
To what extent does the other system support that function?
The Conformance Statement is a starting point for interoperability assessment, but it does not replace real-world integration testing.
Identity Management and Data Consistency
One of the major PACS risks is not necessarily losing an image, but having the image remain intact while being associated with the wrong patient or the wrong examination.
It is important to distinguish:
Patient ID
→ identifies the patient within the relevant identity domain.
Accession Number
→ is generally associated with a specific order or examination.
One patient may have multiple studies and multiple accession numbers over time.
Testing therefore should not simply confirm:
“The image reached PACS.”
It should verify:
correct patient → correct order → correct study → correct report.
Patient Reconciliation
The hospital needs a clear workflow for situations such as:
- Emergency patients whose identities have not yet been confirmed.
- Incorrect Patient IDs.
- Multiple IDs for the same patient.
- Record merges.
- Changes to demographic information.
- Studies associated with the wrong patient or examination.
The facility should determine:
- Which system is the authoritative source?
- Who is authorized to make corrections?
- How do RIS/PACS synchronize changes?
- Is there an audit trail?
- How are already reported studies handled?
Users should not be allowed to modify metadata arbitrarily without appropriate governance.
Where Does PACS Store Data?
The architecture may use:
- Local storage.
- SAN/NAS.
- Object storage.
- Data center.
- Private cloud.
- Public cloud.
- Hybrid storage.
There is no single model suitable for every healthcare facility.
Factors to consider include:
- Number of modalities.
- Number of studies.
- Data size.
- Multi-site or single-site architecture.
- Network.
- Retrieval performance.
- Retention period.
- Redundancy requirements.
- Cost.
- Scalability.
How Should PACS Storage Capacity Be Calculated?
A simple planning model may begin with:
Number of studies × average size per study × retention period × growth rate
and then account for:
- Replication.
- Backup.
- Database.
- Derived images.
- Migration.
- Reserved capacity.
- New modalities.
- New specialties.
The same average study size should not be applied to every modality.
CT, MRI, X-ray, mammography, or video may generate very different data volumes.
Archive, Backup, HA, and DR Are Not the Same Concept
PACS Archive
The location where data are stored for routine operational use.
Backup
A copy used to restore data or systems when they are affected.
High Availability – HA
Reduces downtime when one component or node fails.
Disaster Recovery – DR
Restores service following a major incident.
A PACS with two servers running in HA within the same data center may still lack DR if the entire data center becomes unavailable.
RAID should also not be considered a backup because it does not provide adequate protection against:
- Accidental deletion.
- Corruption.
- Ransomware.
- Application failure.
- Misconfiguration.
- Data center incidents.
RPO, RTO, and Downtime Workflow
Two commonly used metrics in DR planning are:
RPO – Recovery Point Objective
→ the maximum amount of data loss, measured in time, that the facility can accept.
RTO – Recovery Time Objective
→ the target time for restoring service.
There is no single value applicable to every hospital.
The important questions are:
How long can PACS remain unavailable?
and:
What is the maximum acceptable amount of data loss?
In addition to technical DR, the diagnostic imaging department also needs a downtime workflow.
When PACS is unavailable, the facility should know:
- How long can modalities store images locally?
- Is a backup destination available?
- Is a backup viewer available?
- How will reporting be performed?
- How will the backlog be retransmitted after recovery?
- How will duplicate data be minimized?
DR is an IT challenge; downtime is also a hospital operations challenge.
How Does PACS Integrate with HIS/EMR?
A well-designed integration may allow a user who is already viewing a patient record in the EMR to select:
“View Images”
and have the viewer automatically open in the correct patient context.
This can reduce the need to:
1. Open PACS separately.
2. Log in again.
3. Enter the Patient ID.
4. Search for the study.
However, contextual launch should also be tested in scenarios such as:
- Patient merge.
- Multiple IDs.
- Previous sessions.
- Rapid switching between two patients.
- Newly created studies.
The ultimate goal of integration is to reduce repetitive steps and minimize the risk of opening the wrong patient record.
On-Premises, Cloud, or Hybrid?
On-Premises
The hospital directly manages many components such as:
- Servers.
- Storage.
- Network.
- Data center.
Cloud
Cloud deployment may support storage scalability and reduce some local infrastructure requirements, but the facility should assess:
- Bandwidth.
- Latency.
- Data location.
- Subscription costs.
- Internet downtime.
- Cybersecurity.
- Data export.
- Exit strategy.
Hybrid
A hybrid model may combine:
- Cache/local services.
- On-premises integration.
- Cloud archive.
There is no single best model for every hospital.
For cloud or hybrid PACS, facilities should ask at minimum:
- What happens to the workflow if Internet connectivity is lost?
- Are prior studies cached?
- How much bandwidth is required?
- Are data egress fees charged?
- Who is responsible for backup and DR?
- If the contract ends, how can the hospital retrieve all of its data?
Migration and Exit Strategy
When replacing a PACS, the hospital may need to handle:
- Many years of studies.
- Millions of DICOM objects.
- Reports.
- Metadata.
- Presentation states.
- Key images.
- Proprietary data.
Migration should control:
- Patient identity.
- Study count.
- Object count.
- Failed objects.
- Duplicates.
- Mapping.
- Data integrity.
Therefore, the exit strategy should be discussed when purchasing the system, not only when the hospital is preparing to replace PACS.
The hospital should clarify:
- Can all data be exported?
- Is export performed in DICOM or another format?
- Are migration fees charged?
- What is the export speed?
- How is proprietary data handled?
- Can the old system remain available in read-only mode?
The ability to leave a PACS platform is also part of long-term PACS management.
PACS Cybersecurity
PACS connects with many components:
modality ⇔ PACS ⇔ RIS ⇔ EMR ⇔ workstation ⇔ storage ⇔ remote access
The facility should therefore assess:
- Authentication.
- Role-based access.
- Network segmentation.
- Encryption.
- Patching.
- Audit.
- Remote support.
- Privileged accounts.
- Backup.
- Vulnerability management.
Access Control
Not every user needs permission to:
- Merge patients.
- Modify demographics.
- Delete studies.
- Export data.
- Manage accounts.
- Change DICOM configurations.
Roles may include:
- Radiologist.
- Technologist.
- Clinician.
- PACS administrator.
- IT administrator.
- Vendor service personnel.
Audit Log
The facility should review:
- Which events are recorded?
- How long are logs retained?
- Who can access them?
- Can they be searched or exported?
- Are timestamps synchronized?
Remote Support
The vendor may require access for troubleshooting or updates, but the hospital should determine:
- How is remote access performed?
- Does each session require approval?
- Is MFA used?
- Are activities logged?
- What permissions does the vendor have?
- Can vendor personnel access patient data?
Fast remote service should not mean unmanaged remote access.
10 Criteria for Selecting a PACS
1. Modality Compatibility
Review:
- DICOM Conformance Statement.
- Storage.
- Query/Retrieve.
- MWL.
- Storage Commitment.
- Specialized object types.
- DICOMweb where required.
2. RIS/PACS Workflow
Clarify:
- Orders.
- Scheduling.
- Reporting.
- Patient reconciliation.
- Emergency workflows.
3. Viewer and Performance
Assess:
- Diagnostic viewer.
- Clinical viewer.
- Prior-study comparison.
- Performance.
- Remote access.
4. Storage and Scalability
Review:
- Usable capacity.
- Growth.
- Tiering.
- Replication.
- Expansion.
- Archive.
5. Integration
Review:
- HIS.
- EMR.
- RIS.
- Identity.
- Reporting.
- API.
- DICOM/DICOMweb.
6. Cybersecurity
Clarify:
- Authentication.
- Role-based access.
- Audit.
- Patching.
- Remote access.
- Encryption.
- Vulnerability management.
7. Business Continuity
Assess:
- HA.
- Backup.
- DR.
- RPO/RTO.
- Downtime workflow.
8. Data Ownership and Migration
Determine:
- Export capability.
- Formats.
- Migration.
- Exit fees.
- Proprietary objects.
- Exit strategy.
9. Technical Support
Review:
- SLA.
- Support hours.
- Remote support.
- Upgrades.
- Database/storage support.
- Escalation.
10. Total Lifecycle Cost
Do not calculate only the PACS license.
Also consider:
- Servers.
- Storage.
- Viewers.
- Database.
- Backup.
- DR.
- Interfaces.
- Cloud services.
- Support.
- Upgrades.
- Migration.
- Data growth.
Common Mistakes When Implementing PACS
- Treating PACS only as an image archive and overlooking workflow.
- Assuming “DICOM compatible” is sufficient.
- Failing to use or appropriately test Worklist workflows.
- Having no patient reconciliation process.
- Calculating storage only from the current number of terabytes.
- Treating RAID as backup.
- Having backups without testing restoration.
- Failing to develop a downtime workflow.
- Failing to assess remote access.
- Failing to prepare migration and exit strategies.
Short Checklist Before PACS Implementation
Workflow
- HIS/RIS/PACS workflow has been defined.
- Patient/order source is clear.
- Reporting workflow is clear.
- A reconciliation process is available.
Modalities and Integration
- Complete modality list is available.
- DICOM Conformance Statements have been collected.
- MWL and storage workflows are defined.
- HIS/EMR/RIS interfaces have been identified.
- An integration testing plan is available.
Storage and Continuity
- Current data volumes have been measured.
- Growth rate has been calculated.
- Expansion planning is available.
- Backup and restore testing has been defined.
- RPO/RTO and DR are clearly defined.
- A downtime procedure is available.
Cybersecurity
- Authentication and role-based access.
- Patch process.
- Audit.
- Network architecture.
- Remote-support governance.
- Privileged accounts.
Data and Operations
- Patient correction/merge.
- Export.
- Migration.
- Exit strategy.
- PACS administrator.
- Vendor SLA.
- Upgrade plan.
Frequently Asked Questions About PACS
What Is PACS?
PACS is a system used to receive, manage, store, retrieve, display, and distribute digital medical images and related data.
Is PACS a Diagnostic Imaging Device?
No. CT, MRI, X-ray, and other modalities generate images; PACS manages and distributes the resulting imaging data.
Are RIS and PACS the Same?
Not entirely. RIS typically focuses on diagnostic imaging department workflows, while PACS focuses on image management and archiving. However, many platforms integrate both.
If Two Systems Support DICOM, Are They Guaranteed to Connect?
No. Their DICOM Conformance Statements should be compared, and integration testing should be performed using real workflows.
Is a PACS Archive the Same as a Backup?
No. The archive supports routine operation, while backup supports data recovery. HA and disaster recovery are also separate layers.
Is Cloud PACS Better Than On-Premises PACS?
There is no universal answer. Hospitals should assess bandwidth, latency, cybersecurity, data ownership, downtime, subscription costs, and exit strategy.
Does a Hospital Need a VNA?
Not every hospital needs one. A VNA may be useful in environments with multiple PACS platforms, multiple facilities, or enterprise imaging requirements, but it also adds cost and another integration layer that needs to be managed.
This article is provided for informational purposes regarding PACS architecture and operations. Storage configuration, retention periods, integration, cybersecurity, backup, and disaster recovery should be determined according to the actual system, facility policies, and applicable standards or regulations.
Explore Imaging Management and Digital Health Solutions at PHARMEDI & HEALTHCARE VIETNAM 2026
When building or upgrading PACS, a hospital is not simply choosing software for storing images. The decision also involves RIS, modalities, DICOM, storage, viewers, networks, electronic medical records, redundancy, and the way data will be managed over many years.
Exploring solutions is therefore more effective when PACS is considered within the hospital's broader digital health infrastructure rather than as a standalone system within the diagnostic imaging department.
At PHARMEDI & HEALTHCARE VIETNAM 2026, the Product Showcase Area includes categories such as Digital Health and Smart Healthcare, alongside diagnostic and laboratory technologies and medical devices and supplies.
For hospitals considering PACS, RIS, or imaging-management infrastructure, discussions at PHARMEDI VIETNAM 2026 can focus on:
- How does the PACS integrate with modalities, RIS, HIS, or EMR?
- Does the supplier provide a DICOM Conformance Statement?
- How are Modality Worklist and patient reconciliation managed?
- Does the storage architecture use an on-premises, cloud, or hybrid model?
- How does the system scale as the number of CT/MRI systems or facilities increases?
- How do viewers for radiologists differ from viewers for other clinicians?
- How are backup, HA, and disaster recovery designed?
- What is the contingency workflow during PACS downtime?
- How are remote access, accounts, and audit logs governed?
- If PACS is replaced, how are data exported and migrated?
- How are storage expansion, licenses, viewers, support, and integration costs calculated?
These questions help hospitals evaluate PACS based on its ability to operate across the entire imaging-data ecosystem, rather than comparing only storage capacity, user counts, or software interfaces.
From System Investment to the Role of PACS in the Hospital of the Future
PACS can also be considered within a broader context through the International Conference Series on Investment and Innovation in Healthcare, taking place on September 22–23, 2026.
On Day 1 – September 22, the program addresses industry growth and hospital procurement and investment decisions. For a PACS project, this provides a relevant perspective for considering not only the initial license cost but also storage, network infrastructure, integration, backup, disaster recovery, expansion costs, and future migration capability.
On Day 2 – September 23, the program focuses on Hospital Management & Operations, including the session “The Hospital of the Future: Smart, Sustainable, and Patient-Centered.” For PACS, this represents a natural progression from technology infrastructure to real-world operations: images need to be available to the right user at the right time and interoperable with other systems to support care workflows, rather than being stored only in a separate data archive.
From this perspective, PACS can be evaluated across a more complete chain:
Imaging device generates data → PACS receives and manages the data → data are integrated → physicians access the information → the system is protected and made resilient → data remain usable over the long term.
When a More In-Depth Discussion of Integration Architecture Is Needed
For hospitals that already have an existing architecture or are preparing to replace PACS, B2B Matchmaking at PHARMEDI provides additional opportunities for one-to-one discussions with companies based on needs and potential fit.
A discussion can focus directly on areas that are difficult to assess through brochures alone, such as DICOM Conformance, RIS/HIS/EMR integration, migration of legacy data, storage architecture, RPO/RTO, downtime workflows, data export rights, expansion costs, and the responsibilities of each party when implementing interfaces.
In particular, if a hospital is replacing a PACS that has been operating for many years, both migration and exit strategy should be included in discussions from the beginning rather than focusing only on how data will be imported into the new platform.
Through the Digital Health and Smart Healthcare solution categories, the conference series, and professional networking activities, PHARMEDI & HEALTHCARE VIETNAM 2026 provides additional context for healthcare facilities to consider PACS as part of a broader digitalization strategy: from diagnostic imaging to data governance, system integration, business continuity, and long-term scalability.
Dates: September 22–24, 2026
Venue: Saigon Exhibition and Convention Center (SECC), Ho Chi Minh City
Exhibitor Registration:https://pharmed.vn/exhibitor/application-form
Visitor Registration:https://ers-vn.informa-info.com/pha2026?cid=FB
Contact
Booth Booking: [email protected] (Thanh Thuý)
Media Support: [email protected] (Anita Pham)
Visitor Support: [email protected] (Ciel Le)