DICOM PS3.3 2022d - Information Object Definitions

P Stored File Access Through Non-DICOM Protocols (Normative)

The Section A.88 Inventory IOD, and specifically the Section C.38.1 Inventory Module, includes optional Attributes providing a URI for SOP Instances stored in the DICOM File Format and accessible through a non-DICOM file access protocol. Additionally, Inventory SOP Instances themselves may be stored in the DICOM File Format and be accessible through a non-DICOM file access protocol as specified in a URI in the Inventory Creation Response (see Section C.30, and the Section C.38.3 Inventory Creation Module). This Annex specifies constraints on those URIs and their target resources (files).

Note

See also Section YYYY.6 “Security Considerations” in PS3.17.

P.1 Files and Sets of Files

P.1.1 DICOM File Format

Each stored SOP Instance that is a target of an Inventory URI shall be encoded in accordance with the DICOM File Format (see Section 7 “DICOM File Format” in PS3.10).

Note

Depending on the storage mechanism, this target resource may be denoted a "file" or an "object". The term "file" is used in this specification.

P.1.2 Container File Formats

SOP Instances in the DICOM File Format may be aggregated into container files in accordance with the mechanisms specified in this Section.

Note

Directly or indirectly executable files within container files are a security risk. A producer of a container file should avoid including such executable files. A reader should take actions to mitigate against such executable files when reading a container file. See Section YYYY.6.2 “File Format” in PS3.17.

P.1.2.1 ZIP

Multiple SOP Instance files may be included in a ZIP container file in accordance with [ISO 21320-1].

Note

[ISO 21320-1] is a constraint on the [ZIP] specification, and in particular supports only uncompressed or [RFC1951] DEFLATE compressed files, and does not permit encryption.

P.1.2.2 TAR

Multiple SOP Instance files may be included in a TAR container file (i.e., a file in accordance with the ustar Interchange Format) in accordance with [POSIX].

Note

"ustar" is the formal name, derived from "Unix Standard Tape ARchive", although TAR is the common term and is used in this specification. The specification for ustar Interchange Format is in the [POSIX] section "pax - portable archive interchange".

P.1.2.3 GZIP

A single SOP Instance file may be included in a GZIP container file in accordance with [RFC1952].

Note

The GZIP format supports compression of the contained file using [RFC1951] DEFLATE compression.

P.1.2.4 TARGZIP

Multiple SOP Instance files may be included in a TAR container file in accordance with [POSIX], which is then contained within a GZIP container file in accordance with [RFC1952].

Note

The TARGZIP format supports compression of the multiple SOP Instances in the TAR.

P.1.2.5 BLOB

Multiple SOP Instance files may be included in a container file without standardized file delimitation, typically denoted a binary large object (BLOB) or an octet-stream. For use in DICOM, files contained in the BLOB are required to be delimited by externally managed byte offsets and file lengths.

P.1.3 Folders for Sets of Files

The file storage mechanism may support data structures that manage references to sets of files in a folder.

Note

Depending on the storage mechanism,these structures may alternately be denoted "directories". The term "folder" is used in this specification due to potential ambiguities with the term "directory".

The storage of multiple SOP Instance files may be managed such that all SOP Instances in a Study or in a Series are contained within a single folder. Within that folder, some or all of the files may be included in a ZIP, TAR, GZIP, TARGZIP, or BLOB container file.

DICOM PS3.3 2022d - Information Object Definitions