StudyInstanceUID

StudyInstanceUID is a globally unique identifier used in the DICOM medical imaging standard to identify a single imaging study. In DICOM metadata, the Study Instance UID (tag 0020,000D) serves as the primary key that links all objects belonging to the same study, including its series and individual image instances. The identifier is intended to remain stable for the life of the study and should be unique across institutions and systems.

Generation and format: UIDs are numeric strings composed of components separated by periods. They are created by the issuing Application Entity using a root UID allocated to the institution, with additional locally unique components appended to ensure global uniqueness. The resulting string adheres to DICOM length limits and is designed to be persistent and non-repeating across studies.

Usage and implications: The StudyInstanceUID enables reliable organization, querying, and retrieval of all data associated with a study. It is used in workflows such as query/retrieve, record linkage, and provenance tracking. Because it uniquely identifies the study across sessions and systems, it supports interoperability and data sharing. In anonymized datasets, the StudyInstanceUID may be replaced with a new anonymized UID to protect patient identity, while preserving the structural relationships between series and images.

Relation to other identifiers: Within a study, each series has its own SeriesInstanceUID and each image has a SOPInstanceUID, while the patient is identified separately by a PatientID or equivalent. Together, these UIDs form a hierarchical, globally unique addressing scheme that underpins data integrity and cross-system compatibility in DICOM workflows.