DICOM Standard: A Complete Guide to Understanding Digital Medical Imaging

If you work in the healthcare sector — whether as a radiologist, clinic administrator, or hospital IT manager — you've very likely heard the term DICOM. But what does it really mean, and why is it so important for modern medical imaging? In this complete guide, we explain everything you need to know.

What Is DICOM?

DICOM stands for Digital Imaging and Communications in Medicine. It is an international standard that defines how digital medical images are created, stored, transmitted, and displayed.

In practical terms, DICOM is the "common language" that allows equipment from different manufacturers — CT scanners, MRI machines, ultrasound devices, mammography systems, X-ray units — to communicate with each other and with hospital information systems. Without DICOM, each manufacturer would have its own proprietary format, and sharing images between devices would be virtually impossible.

A Brief History: Why Was DICOM Created?

Before the 1980s, medical images were analog: radiographic films stored physically and transported from office to office. With the advent of computed tomography and magnetic resonance imaging, hospitals began generating digital images, but each manufacturer used a different and incompatible format.

In 1983, the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) launched a joint effort to solve this problem. The result was the ACR-NEMA standard, which evolved into DICOM 3.0 in 1993, the version that laid the foundation for the standard we use today. Since then, DICOM has been continuously updated to incorporate new imaging modalities, compression formats, and network services.

How Does DICOM Work?

The DICOM standard encompasses three fundamental dimensions:

1. File Format

A DICOM file (.dcm) is not simply an image. It contains the medical image along with all its associated clinical information. This sets it radically apart from conventional formats like JPEG or PNG.

2. Metadata and Tags

Each DICOM file includes an extensive set of metadata tags that describe:

• Patient data: name, identification, date of birth, sex.
• Study information: date, time, referring physician, study description.
• Series data: modality (CT, MR, US, CR), series number, patient position.
• Technical image parameters: resolution, bits per pixel, window and level, slice thickness.
• Unique identifiers (UIDs): each study, series, and image has a universal identifier that ensures traceability.

These tags follow a standardized structure based on group-element pairs (for example, tag (0010,0010) always corresponds to the patient's name), ensuring that any compatible system can interpret the information correctly.

3. Communication Protocol

DICOM also defines a network protocol that allows medical devices to communicate with each other. It operates over TCP/IP and establishes "associations" between two DICOM entities (called Application Entities or AE), negotiating what type of data they can exchange before initiating the transfer.

Key DICOM Services

The standard defines several services that cover the most common operations in a radiology workflow:

• C-STORE (storage): allows sending images from an acquisition device (such as a CT scanner) to a storage server or PACS. It is the most widely used service in daily practice.
• C-FIND / C-MOVE (query and retrieval): allows searching for studies on a DICOM server by filtering by patient, date, modality, or other criteria, and then retrieving images to a workstation.
• Modality Worklist: connects the information system (HIS/RIS) with imaging modalities so that patient data is automatically loaded onto the equipment, eliminating manual data entry errors.
• DICOM Print: enables printing of medical images on specialized printers (dry laser) while maintaining diagnostic quality.
• Storage Commitment: confirms that images were correctly stored on the server, allowing the originating device to safely free up space.

DICOM vs. Other Image Formats

It is common to wonder why not simply use JPEG or PNG for medical images. The answer lies in the fundamental differences:

| Feature | DICOM | JPEG / PNG | |---|---|---| | Bit depth | Up to 16 bits (65,536 gray levels) | 8 bits (256 gray levels) | | Clinical metadata | Embedded in the file | Not included | | Patient identification | Built-in and standardized | Non-existent | | Compression | Lossless or controlled lossy | Generally lossy (JPEG) | | Volumetric series | Native support for multiple slices | One file per image | | Network protocol | Included in the standard | Not applicable |

In summary, JPEG and PNG are formats designed for photography and graphics; DICOM is a format designed specifically for clinical practice, where every detail — from a subtle change in tissue density to the unambiguous identification of the patient — is critical for diagnosis.

How Does DICOM Relate to PACS?

PACS (Picture Archiving and Communication System) is the system that stores, organizes, and distributes medical images within a healthcare institution. DICOM is the standard upon which a PACS operates.

The relationship works as follows:

1. The imaging equipment generates DICOM files when a study is performed (X-ray, CT, MRI, etc.).
2. The files are sent to the PACS using DICOM's C-STORE service.
3. The PACS stores the images and their metadata in its database, enabling fast searches.
4. Radiologists consult and interpret studies from DICOM viewers connected to the PACS, using query and retrieval services.
5. Treating physicians access the results through web portals or integrations with the electronic health record.

Without DICOM, a PACS simply could not function. It is the foundation that guarantees interoperability between equipment from different brands and the integrity of clinical information throughout the entire workflow.

Conclusion

The DICOM standard is much more than a file format: it is the fundamental pillar of digital medical imaging. It ensures that images are generated with diagnostic quality, transmitted securely, stored with all their clinical information, and can be shared between institutions without data loss.

At Davix, our PACS system is designed with full DICOM support, ensuring total compatibility with equipment from any manufacturer, secure cloud storage, and immediate access to studies from any device. If your institution is looking to modernize medical image management with a reliable and easy-to-deploy platform, Davix is the solution.