MedScan
Why Your DICOM Viewer Should Work 100% Offline
Updated April 2026 · 5 min read
Many modern DICOM viewers require uploading medical images to cloud servers for viewing. While convenient, this approach raises serious privacy, compliance, and practical concerns. Here's why offline-first DICOM viewing should be the default.
The HIPAA Problem with Cloud Viewers
HIPAA (Health Insurance Portability and Accountability Act) regulates how Protected Health Information (PHI) is stored and transmitted. DICOM files are rich with PHI — patient name, date of birth, medical record number, referring physician, and the images themselves.
When you upload a DICOM file to a cloud viewer, you're transmitting PHI to a third-party server. This requires:
- A Business Associate Agreement (BAA) with the cloud provider
- Encryption in transit and at rest
- Access controls and audit logging
- Data retention and deletion policies
- Breach notification procedures
Many free cloud DICOM viewers don't offer BAAs or meet these requirements. Using them with real patient data is a compliance risk.
The Practical Problem
Beyond compliance, cloud viewers have practical issues:
The MedScan Approach: Offline-First
MedScan was designed from the ground up for offline operation:
Cloud vs Offline: Quick Comparison
| Aspect | Cloud Viewers | MedScan (Offline) |
|---|---|---|
| PHI transmitted | Yes — to cloud | No — stays on device |
| Works without internet | No | Yes |
| Upload required | Yes (minutes) | No (instant open) |
| BAA required | Yes | Not applicable |
| Speed | Network-dependent | 33ms cached reopen |
| Account required | Usually yes | No |
When Online is Acceptable
Offline-first doesn't mean never-online. The optional PACS/DICOMweb import needs a network connection to reach your own server — but that traffic goes directly between your device and your PACS. MedScan itself never uploads studies to any third-party cloud.
This hybrid approach — complete offline capability for viewing, with optional AI assistance — is the right balance for clinical workflows.