Modern Medical Imaging: RIS, PACS, and the Challenges of Nuclear Medicine

Medical imaging has undergone a digital revolution over the past decades. Between conventional radiology and nuclear medicine, healthcare professionals now rely on sophisticated information systems to manage, archive, and analyze the millions of images produced each year. At the heart of this transformation are two essential technological pillars: the RIS (Radiology Information System) and the PACS (Picture Archiving and Communication System).

What is a RIS?

The RIS (Radiology Information System) is the information system used in radiology and nuclear medicine to manage all administrative and clinical patient data. Think of it as the organizational brain of an imaging center.

Key Functions of a RIS

The RIS intervenes throughout the patient journey, from appointment scheduling to results transmission:

Administrative Management: The RIS organizes time slots based on equipment and medical team availability. It can interface with online appointment platforms, allowing patients to book their slots directly.

Exam Preparation: Before the appointment, the system allows patients to complete medical questionnaires online and receive SMS reminders with preparation instructions. This automation significantly improves the patient experience and reduces no-shows.

Dose Calculation (specific to nuclear medicine): In nuclear medicine, where radiopharmaceutical products are used, the RIS handles the calculation of necessary doses based on patient characteristics (weight, height, pathology).

Teletransmission: The RIS manages the teletransmission of administrative information to ensure that all necessary data is available before the exam, including reimbursements via Social Security.

Access to Results: After the exam, the RIS provides an online portal where patients can view their results. A portal is also accessible to referring physicians, allowing them to view reports and associated images.

Specific Constraints in Nuclear Medicine

Choosing a RIS in nuclear medicine is particularly complex. The number of vendors adapted to this specialty is very limited, as these systems must integrate unique functionalities:

• Radiopharmacy Management: ordering, receiving, and traceability of radioactive products
• Integration with DACS Systems (Dosimetry Archiving and Communication System) that centralize and archive dosimetric data
• Ségur Compliance: mandatory certification in France to guarantee interoperability with national platforms (MSSanté, DMP, ENS)
• HDS Hosting (Health Data Hosting): legal obligation to secure sensitive data

What is a PACS?

The PACS (Picture Archiving and Communication System) is the system that enables the archiving, management, and transmission of digital medical images. While the RIS manages administrative data and workflow, the PACS manages the images themselves.

The Role of PACS in the Patient Journey

Advanced Image Visualization: The PACS offers an interface allowing physicians to visualize images obtained during exams. Thanks to its advanced tools, it facilitates imaging data analysis by offering functions such as:

• Zoom and contrast manipulation
• 3D reconstruction
• Measurement and annotation tools
• Multi-modality image fusion (PET/CT, SPECT/CT)

These functionalities are essential for detecting and evaluating metabolic or functional abnormalities captured by nuclear medicine techniques.

Centralized and Secure Archiving: The PACS allows medical images to be stored centrally. Physicians can review a patient's previous exams to compare changes, which is essential for monitoring chronic diseases or evaluating treatment response.

Communication Between Specialists: Thanks to the PACS, nuclear medicine physicians can easily share images and associated data with other specialists such as oncologists, cardiologists, or surgeons. This capability for rapid communication without loss of image quality promotes a collaborative approach to diagnosis and treatment planning.

The Image Lifecycle in Nuclear Medicine

To understand the importance of RIS and PACS, one must visualize the complex journey of a medical image:

1. Image Acquisition

Radiologic technologists use modalities (gamma cameras, PET-CT, SPECT) to capture patient images. These raw images are transmitted via the DICOM (Digital Imaging and Communication in Medicine) protocol, the international standard for medical image exchange.

2. Image Enhancement

The physician uses a post-processing console (such as Siemens' Syngo VIA) to construct an "augmented image." They perform 3D reconstructions, image fusions, and quantitative analyses. This step is crucial in nuclear medicine where the raw image must be transformed into actionable diagnostic information.

3. Storage

Once enhanced, images are sent to the PACS for long-term archiving. A cache system keeps recent images (typically 3 months) on a local server for quick access. Older images remain accessible via the cloud PACS but may require download time.

4. Interpretation

The physician can interpret images in several ways:

• Directly from the post-processing console
• From their PC on the local network
• Via remote connection (tele-interpretation)

This flexibility is essential to enable remote expertise and organize physicians' work.

5. Consultation and Sharing

Images are available to referring physicians and patients via a web viewer. The physician can also share images with colleagues via a Dreambox (tele-imaging solution compliant with Ségur).

Technical Challenges of Modern Imaging

Bandwidth: The Nerve of War

Nuclear medicine images are voluminous. An exam can generate hundreds of "slices" (cross-sections) in high resolution. The very high-speed link between modalities and the server is essential. In case of micro-outages, images can be lost.

To give an order of magnitude:

• A video conference requires approximately 3 Mb/s
• Standard remote work usage requires approximately 10 Mb/s
• Medical image interpretation may require much higher connections, depending on the number of slices and reconstruction complexity

RIS-PACS Integration

One of the major challenges is ensuring smooth communication between RIS and PACS. Automatic connection allows, for example, automatically retrieving a patient's old images from the PACS when a new appointment is scheduled in the RIS.

This interoperability relies on standards such as:

• HL7: for exchanging administrative and clinical data
• DICOM: for images and associated metadata
• FHIR: new standard to facilitate interoperability with modern systems

Regulatory Compliance

In France, the Ségur framework imposes strict constraints:

• HDS Hosting located in France with redundancy on a second remote site
• Interoperability with national platforms
• Security: GDPR compliance, cybersecurity, single-user authentication
• Traceability: particularly for dosimetric data via DACS systems

The Tele-interpretation Challenge

The ability for a physician to interpret images remotely has become a strategic issue. It enables:

• Pooling of expertise across multiple sites
• Service continuity (on-call, emergency coverage)
• Attractiveness for recruiting physicians

But this imposes strong technical constraints:

• High-capacity servers to handle multiple simultaneous interpretations
• Redundant connections (dual fiber) to guarantee availability
• Secure remote access solutions compliant with health standards

The Technological Ecosystem of Nuclear Medicine

Beyond RIS and PACS, nuclear medicine centers rely on a complex ecosystem:

DACS: The dosimetry system archives and analyzes all dose data administered to patients, with alerts in case of regulatory threshold exceedance.

Post-processing Consoles: Powerful workstations equipped with specialized software (Syngo VIA, Osirix, etc.) for advanced image analysis.

Local Servers: To ensure optimal performance, each site typically requires a local server directly connected to modalities. Sizing depends on the number of exams and physicians working simultaneously.

Web Viewer: Browser-accessible interface to allow referring physicians and patients to view images, with secure access (HTTPS, strong authentication, ProSanté Connect).

Dreambox: Ségur-compliant tele-imaging solution for secure image sharing with correspondents.

Strategic Challenges for Imaging Centers

Limited Supply

The market for RIS adapted to nuclear medicine is highly concentrated. Only a few vendors offer complete solutions integrating radiopharmacy management and interface with DACS systems. This situation limits negotiation and often imposes complex pricing models (licenses + maintenance rather than SaaS).

Portfolio Strategy

For multi-site groups, a coherent approach is essential:

• RIS Standardization: using a common vendor facilitates data collection, expertise sharing, and negotiation of group rates
• PACS Strategy: referencing a few compatible solutions avoids systematically paying new interfacing fees
• Inter-site Collaboration: a single PACS allows group physicians to collaborate on complex patient cases

Managed Services

The growing complexity of systems requires specialized IT expertise. Centers must choose between:

• Local Managed Services: capitalize on field knowledge, but with fewer economies of scale
• Centralized Managed Services: standardization and cost optimization, but risk of losing proximity
• Hybrid Model: local managed service providers coordinated by a group CIO

Toward Artificial Intelligence in Imaging

The future of medical imaging inevitably involves artificial intelligence. RIS and PACS systems must integrate AI tools for:

• Automatic anomaly detection
• Automated quantification (tumor volumetry, SUV max, etc.)
• Diagnostic decision support
• Prioritization of urgent exams
• Prediction of treatment response

But this evolution requires rethinking system architecture to enable:

• Data export to data lakes for algorithm training
• Seamless integration of AI tools into clinical workflow
• Traceability of AI-assisted decisions for medico-legal reasons

Conclusion

RIS and PACS are not mere IT tools: they are the central nervous system of modern imaging centers. Their selection and configuration determine the quality of patient care, operational efficiency, and the innovation capacity of facilities.

In nuclear medicine, complexity is further increased by specialty-specific requirements (radiopharmacy, dosimetry) and strict regulatory constraints. Professionals must navigate a complex technical ecosystem where each component (RIS, PACS, servers, network, security) must articulate perfectly.

The challenge for the coming years will be to maintain this high-performance technical infrastructure while enriching it with new capabilities offered by artificial intelligence. An exciting challenge in service of better medicine for all.

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This article was written for medical imaging professionals and healthcare sector decision-makers. It reflects the current state of the art of information systems in radiology and nuclear medicine.