F.2 Media Formats
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## F.2 Media Formats

### F.2.1 Physical Format

The physical format of DICOM CD-R discs shall comply with the applicable definitions within ISO/IEC 10149, Part II: CD-WO in Orange Book and CD-ROM-XA (extended Architecture) (if Mode 1 sectors are not used), with the additional modifications described in Section F.2.1.1 and Section F.2.1.2.

#### F.2.1.1 Sector Format

All DICOM files and all data that comprise the ISO 9660 file system of the DICOM CD-R disc shall be stored either:

- within Mode 1 sectors, or

- within Mode 2, Form 1 sectors with CD-ROM-XA File Number = 0, Channel Number = 0 and Coding Information Byte = 0.

### Note

1. The physical storage capacity of a CD-R disc can be 74 minutes (630 MB) or 80 minutes (700 MB) when using the Mode 1 or Mode 2 Form 1 format. The capacity is fixed by the pre-grooved spiral track present on a blank CD-R. Some older CD players will not be able to read the 80 min capacity CD-R discs.

2. The DICOM standard prohibits the use of Mode 2 Form 2 sectors. This format is used to record data on CD-Rs that exceed 74 minute capacity and can also be used for smaller capacity CD-Rs. CD-ROM-XA Mode 2 Form 2 sectors do not have sector level error correction. This significantly decreases the reliability of the media and significantly increases the likelihood of data corruption.

#### F.2.1.2 Multi-session Format

An area on the disc consisting of a Lead-In area, a Program area, and a Lead-Out area, is called a "Session." If a disc contains or is able to contain more than one session then this disc is called a "Multi-session" disk. If the Lead-In area contains a pointer to the next session, then the disc is appendable. The Lead-In and Lead-Out areas are written at the conclusion of writing the program Area. The process of writing the Lead-In and Lead-Out areas is commonly referred to as "Finalizing the Session." The last recorded session contains all the information needed to access the entire disc.

DICOM CD-R disc may contain multiple sessions. Data are added to a disc by opening and writing a new session. A disc is non-appendable if the last recorded session is designated as the "Final Session," as defined in Part II: CD-WO version 2.0, Section 5.5.2.

CD-ROM readers shall support Multi-session CDs.

CD-R writers may choose to support Multi-session writing.

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