Build A Complete PACS Server: DICOM Archive Guide

This article guides you through building a complete Picture Archiving and Communication System (PACS) server, integrating all necessary modules for a functional DICOM archive. This comprehensive guide is designed to serve as both a demonstration of full PACS functionality within a single application and as a reference implementation for those looking to build their own PACS solutions. Furthermore, it provides a working mini-PACS environment ideal for testing and development purposes. Let's dive into the world of PACS and explore how to create your own.

Overview of a Full PACS Server

Our goal is to create a comprehensive PACS server that integrates all the essential modules, providing a robust solution for medical image storage and retrieval. This project demonstrates the full functionality of a PACS system within a single application, making it an invaluable resource for developers and healthcare professionals alike. Think of it as a blueprint for building your own PACS, a reference implementation that showcases best practices and design principles. Beyond its educational value, this server functions as a working mini-PACS, perfect for testing new features, protocols, or integrations in a controlled environment. This allows you to experiment and validate your ideas without impacting a live production system. One of the key benefits is the hands-on experience you gain by building and configuring a PACS server from the ground up. You'll develop a deep understanding of the inner workings of a PACS, including DICOM communication, storage management, and query/retrieval processes. This knowledge is invaluable for anyone working with medical imaging technology. This guide provides a solid foundation for anyone looking to delve deeper into the world of PACS, whether you're a software developer, a healthcare IT professional, or simply curious about medical imaging systems.

Purpose and Benefits

The primary purpose of this project is to demonstrate the full capabilities of a PACS system within a single, cohesive application. It serves as a valuable reference implementation, showcasing how different modules and services can be integrated to create a functional archive. For developers, this offers a clear and concise example of how to build a PACS from scratch, providing a practical guide to the underlying technologies and protocols. Furthermore, this project yields a working mini-PACS, a scaled-down version of a full-fledged PACS suitable for testing, development, and educational purposes. This mini-PACS provides a safe and controlled environment for experimenting with new features, configurations, and integrations without the risk of disrupting a live production system. Imagine being able to test a new DICOM service or explore different storage configurations without affecting your clinical workflow. This project empowers you to do just that. The practical benefits extend beyond testing and development. This mini-PACS can also serve as a valuable training tool for medical professionals and IT staff, allowing them to familiarize themselves with PACS workflows and functionalities in a hands-on setting. By deploying this server, you gain a deeper understanding of PACS architecture, DICOM communication, and storage management principles. This knowledge is essential for anyone working with medical imaging data, whether you're a radiologist, a PACS administrator, or a software engineer.

Usage Instructions

To get started with the PACS server, you'll need to understand the basic commands and configuration options. The simplest way to launch the server is using the pacs_server command without any arguments. This will start the server with a default configuration, suitable for basic testing and exploration. For more advanced setups, you can use a configuration file to customize various parameters, such as the port number, AE title, and storage directory. To specify a configuration file, use the --config option followed by the path to your YAML file (e.g., pacs_server --config pacs_server.yaml). Command-line options offer the most flexibility, allowing you to override specific settings without modifying the configuration file. For instance, you can change the port number using --port, the AE title using --ae-title, and the storage directory using --storage-dir (e.g., pacs_server --port 11112 --ae-title MY_PACS --storage-dir ./archive). This allows you to quickly adapt the server to different environments and testing scenarios. Understanding these basic commands is crucial for effectively using the PACS server. Whether you're running it for a quick test or deploying it in a more complex setup, these options give you the control you need to tailor the server to your specific needs. Remember to consult the documentation for a full list of available options and their descriptions.

# Start with default configuration
pacs_server

# Start with config file
pacs_server --config pacs_server.yaml

# Start with command line options
pacs_server --port 11112 --ae-title MY_PACS --storage-dir ./archive

Supported DICOM Services

Our complete PACS server supports a range of essential DICOM services, ensuring compatibility with various medical imaging modalities and applications. These services are the backbone of any PACS system, enabling communication, storage, retrieval, and management of medical images. The C-ECHO service, also known as the Verification service, is used to test connectivity between the PACS server and other DICOM nodes. It's a simple yet crucial service for ensuring that communication channels are open and functioning correctly. The C-STORE service is the workhorse of image reception, responsible for storing medical images sent to the PACS server. This service handles the transfer of image data from modalities like CT scanners, MRI machines, and X-ray systems, ensuring that images are safely and reliably stored in the archive. For querying the PACS, we support the C-FIND service. This powerful service allows users to search for patients, studies, series, and instances based on various criteria, making it easy to locate specific images within the archive. Image retrieval is handled by the C-MOVE and C-GET services. C-MOVE enables the PACS server to move images to a specified destination, while C-GET allows direct retrieval of images. These services provide flexibility in how images are accessed and distributed. Finally, we support Modality Worklist (MWL) and Modality Performed Procedure Step (MPPS) services. MWL provides a list of scheduled procedures to imaging modalities, streamlining the workflow. MPPS tracks the progress of a procedure step, providing valuable information for workflow management and billing purposes. This comprehensive suite of supported services ensures that our PACS server can seamlessly integrate with a wide range of DICOM-compliant devices and systems.

Configuration Details

The PACS server's behavior can be extensively customized through a configuration file, allowing you to tailor it to your specific needs and environment. This configuration file, typically in YAML format, provides a centralized way to manage various settings, from network parameters to storage policies. The server section of the configuration file allows you to define core server settings, including the AE title (a unique identifier for your PACS), the port number on which the server listens for connections, the maximum number of simultaneous associations, and the idle timeout. These parameters control the server's network behavior and resource usage. Storage settings are configured in the storage section. Here, you can specify the directory where images are stored, the naming convention used for files and directories (e.g., hierarchical), and the policy for handling duplicate images. These settings are critical for managing the PACS archive and ensuring data integrity. The database section allows you to configure the database used for indexing the PACS archive. You can specify the path to the database file and enable Write-Ahead Logging (WAL) mode for improved performance and data safety. Security is a paramount concern, and the tls section allows you to enable Transport Layer Security (TLS) for secure communication. You can specify the paths to the server's certificate and private key. Logging settings are configured in the logging section, allowing you to control the logging level and the file where logs are written. Proper logging is essential for monitoring the PACS server and troubleshooting issues. The monitoring section enables real-time statistics and performance metrics, which can be invaluable for capacity planning and performance optimization. You can specify the port for exposing metrics in Prometheus format. Finally, the access_control section allows you to define which AE titles are allowed to connect to the PACS server. This provides a basic level of security by whitelisting trusted DICOM nodes. By carefully configuring these settings, you can fine-tune the PACS server to meet your specific requirements and ensure optimal performance and security.

# pacs_server.yaml
server:
 ae_title: MY_PACS
 port: 11112
 max_associations: 50
 idle_timeout: 60

storage:
 directory: ./archive
 naming: hierarchical
 duplicate_policy: reject

database:
 path: ./pacs.db
 wal_mode: true

tls:
 enabled: false
 cert_path: ./certs/server.crt
 key_path: ./certs/server.key

logging:
 level: info
 file: ./logs/pacs.log

monitoring:
 enabled: true
 metrics_port: 9090

access_control:
 allowed_ae_titles:
 - "*" # Accept all, or list specific AEs

Key Features Implemented

This complete PACS server boasts a range of features designed to ensure efficient storage, retrieval, and management of medical images. Multi-Service Support is a cornerstone of the design, with all essential SCP (Service Class Provider) services registered and ready to handle DICOM communication. The server automatically dispatches incoming requests to the appropriate service based on the SOP Class, streamlining the handling of various DICOM operations. Storage Management is handled with a hierarchical file organization, making it easy to navigate and manage the archive. An SQLite database provides robust indexing capabilities, allowing for fast and efficient searching and retrieval of images. Duplicate detection mechanisms prevent redundant storage of the same image, optimizing storage utilization. Monitoring & Logging are crucial for maintaining a healthy PACS environment. Real-time statistics provide insights into server performance and activity, while connection logging tracks DICOM associations for auditing and troubleshooting. Performance metrics, exposed in Prometheus-compatible format, allow for integration with monitoring systems for proactive alerting and capacity planning. Security is a top priority. TLS support (optional) encrypts communication channels, protecting sensitive patient data. AE title whitelisting restricts access to trusted DICOM nodes, preventing unauthorized connections. Rate limiting mechanisms mitigate the risk of denial-of-service attacks. Administration features ensure smooth operation and maintenance. Graceful shutdown (triggered by SIGTERM/SIGINT signals) allows the server to shut down cleanly, preventing data corruption. Configuration reload (triggered by SIGHUP signal) allows for dynamic updates to the server's configuration without requiring a restart. A status endpoint provides a quick way to check the server's health and operational status. These features combine to create a robust and feature-rich PACS server, capable of handling the demands of a modern medical imaging environment.

Architectural Overview

The architecture of our PACS server is designed for modularity, scalability, and maintainability. At the heart of the system lies the DICOM Server, responsible for handling all DICOM communication. This server acts as the central point of entry for incoming DICOM requests, dispatching them to the appropriate service based on the SOP Class. The various SCP services, such as Echo, Store, and Query, are implemented as separate modules, each responsible for handling a specific set of DICOM operations. This modular design allows for easy extension and customization of the server's functionality. The Storage Layer manages the physical storage of medical images. It provides a hierarchical file organization for efficient storage and retrieval, and it interacts with the Database Layer to index the archive. The Database Layer, built on SQLite, provides a robust and efficient way to store metadata about the images in the archive. This allows for fast and flexible querying of the PACS. The interaction between these layers is crucial for the overall performance and reliability of the PACS server. The DICOM Server receives requests, the SCP services process them, the Storage Layer manages the image files, and the Database Layer provides indexing and querying capabilities. This layered architecture promotes separation of concerns, making the system easier to understand, maintain, and extend. The diagram provided visually represents this architecture, highlighting the key components and their interactions. This clear and well-defined architecture is a key factor in the server's robustness and scalability.

┌─────────────────────────────────────────────┐
│ PACS Server │
├─────────────────────────────────────────────┤
│ ┌─────────┐ ┌─────────┐ ┌─────────┐ │
│ │ Echo │ │ Store │ │ Query │ ... │
│ │ SCP │ │ SCP │ │ SCP │ │
│ └────┬────┘ └────┬────┘ └────┬────┘ │
│ └───────────┼───────────┘ │
│ ┌────┴────┐ │
│ │ DICOM │ │
│ │ Server │ │
│ └────┬────┘ │
│ │ │
│ ┌────────────────┼────────────────┐ │
│ │ ┌───────────┼───────────┐ │ │
│ │ │ Storage │ Database │ │ │
│ │ │ Layer │ Layer │ │ │
│ │ └───────────┴───────────┘ │ │
│ └─────────────────────────────────┘ │
└─────────────────────────────────────────────┘

Dependencies Required

Building this complete PACS server requires a set of well-defined dependencies. The core pacs_* modules form the foundation of the server, providing the essential building blocks for DICOM communication, storage management, and service implementation. These modules encapsulate the core PACS functionalities, ensuring a cohesive and well-structured system. The pacs_integration module serves as a crucial bridge, integrating all the ecosystem adapters required for seamless interaction with various DICOM devices and applications. This module simplifies the process of connecting the PACS server to external systems, ensuring compatibility and interoperability. By leveraging these dependencies, we can create a robust and feature-rich PACS server without reinventing the wheel. These modules provide pre-built functionalities that have been thoroughly tested and optimized, saving development time and effort. Understanding these dependencies is essential for anyone looking to build, extend, or maintain the PACS server. They represent the key components that work together to provide a complete and functional PACS solution.

Acceptance Criteria for Deployment

Before deploying our complete PACS server, we need to establish clear acceptance criteria to ensure that it meets our requirements and functions as expected. All DICOM services must be functional, including C-ECHO, C-STORE, C-FIND, C-MOVE, C-GET, MWL, and MPPS. This ensures that the server can communicate with various DICOM devices and applications, handle image storage and retrieval, and manage workflow information. Configuration file support is essential for flexible deployment and customization. The server must be able to load its configuration from a YAML file, allowing administrators to easily adjust settings without modifying the code. Graceful startup and shutdown are crucial for maintaining data integrity. The server must start up without errors and shut down cleanly, releasing resources and preventing data corruption. Database persistence across restarts ensures that the PACS archive is preserved. The server must be able to store metadata in a database and retrieve it correctly after a restart. Logging and monitoring must be operational, providing insights into server performance and activity. Logs should be written to a file, and monitoring metrics should be available for analysis. Finally, the server must be compatible with standard DICOM tools, ensuring interoperability with existing DICOM viewers, workstations, and other applications. Meeting these acceptance criteria guarantees that the PACS server is ready for deployment and can reliably handle medical imaging data.

Files to be Created

To bring this complete PACS server to life, we need to create a specific set of files, each serving a distinct purpose within the project. The main.cpp file located in the examples/pacs_server/ directory will serve as the entry point for the application. This file will contain the main function, responsible for initializing the server and starting its execution. The config.hpp file will define the configuration parameters and structures used throughout the server application. This header file will ensure consistency and maintainability of configuration settings. The server_app.hpp file will declare the ServerApp class, which encapsulates the core PACS server logic. This class will manage the DICOM server, the storage layer, and the various SCP services. The server_app.cpp file will provide the implementation for the ServerApp class, defining the behavior of the server and its interactions with other modules. The pacs_server.yaml.example file will serve as a template for the configuration file. This file will provide examples of how to configure various server settings, such as the AE title, port number, and storage directory. Finally, the CMakeLists.txt file will define the build process for the server application. This file will instruct CMake on how to compile the source code, link the dependencies, and create the executable. By creating these files, we lay the foundation for a well-structured and maintainable PACS server application. Each file plays a crucial role in the overall functionality of the system.

- `examples/pacs_server/main.cpp`
- `examples/pacs_server/config.hpp`
- `examples/pacs_server/server_app.hpp`
- `examples/pacs_server/server_app.cpp`
- `examples/pacs_server/pacs_server.yaml.example`
- `examples/pacs_server/CMakeLists.txt`

In conclusion, building a complete PACS server is a challenging but rewarding endeavor. This guide has provided a comprehensive overview of the process, from understanding the purpose and benefits to configuring the server and defining acceptance criteria. By following these steps and leveraging the provided information, you can create your own PACS solution, tailored to your specific needs and requirements. For more in-depth information on DICOM standards and PACS implementation, consider exploring resources like the DICOM Standard website.