Материал: part05

•​Implementation level: ISO 2022 Level 1 - Elementary 7-bit code (code-level identifier 1)​

•​Initial designation: ISO-IR 6 (ASCII) as G0.​

•​Code Extension shall not be used.​

b.​Attribute Specific Character Set (0008,0005) single value other than "ISO_IR 192", "GB18030" or "GBK":​

•​8-bit code​

•​Implementation level: ISO 2022 Level 1 - Elementary 8-bit code (code-level identifier 11)​

•​Initial designation: One of the ISO 8859-defined character sets, or the 8-bit code table of JIS X 0201 specified by value 1 of​ the Attribute Specific Character Set (0008,0005), as G0 and G1.​

•​Code Extension shall not be used.​

c.​Attribute Specific Character Set (0008,0005) multi-valued:​

•​8-bit code​

•​Implementation level: ISO 2022 Level 4 - Redesignation of Graphic Character Sets within a Code (code-level identifier 14)​

•​Initial designation: One of the ISO 8859-defined character sets, or the 8-bit code table of JIS X 0201 specified by value 1 of​ the Attribute Specific Character Set (0008,0005), as G0 and G1. If value 1 of the Attribute Specific Character Set (0008,0005)​ is empty, ISO-IR 6 (ASCII) is assumed as G0, and G1 is undefined.​

•​All character sets specified in the various values of Attribute Specific Character Set (0008,0005), including value 1, may parti-​ cipate in Code Extension.​

d.​Attribute Specific Character Set (0008,0005) single value "ISO_IR 192", "GB18030" or "GBK":​

•​variable length code​

•​Implementation level: not specified (not compatible with ISO 2022)​

•​Initial designation: as specified by value 1 of the Attribute Specific Character Set (0008,0005)​

•​Code Extension shall not be used.​

6.1.3 Control Characters​

Textual data that is interchanged may require some formatting information. Control Characters are used to indicate formatting, but​ their use in DICOM is kept to a minimum since some machines may handle them inappropriately. ISO 646:1990 and ISO 6429:1990​ define Control Characters. As shown in Table 6.1-1 below, only a subset of five Control Characters from the C0 set shall be used in​ DICOM for the encoding of Control Characters in text strings.​

Table 6.1-1. DICOM Control Characters and Their Encoding​

The ESC character shall be used only for ISO 2022 character set control sequences, in accordance with Section 6.1.2.5.​

In text strings (value representation ST, LT, or UT) a new line shall be represented as CR LF.​

- Standard -​

Note​

1.​Some machines (such as UNIX based machines) may interpret LF (00/10) as a new line. In such cases, it is expected​ that the DICOM format is converted to the correct internal representation for that machine.​

2.​In previous editions of the Standard (see PS3.5 2015a), the TAB character was not listed as a Control Character.​

6.2 Value Representation (VR)​

The Value Representation of a Data Element describes the data type and format of that Data Element's Value(s). PS3.6 lists the VR​ of each Data Element by Data Element Tag.​

Values with VRs constructed of character strings, except in the case of the VR UI, shall be padded with SPACE characters (20H, in​ the Default Character Repertoire) when necessary to achieve even length. Values with a VR of UI shall be padded with a single​ trailing NULL (00H) character when necessary to achieve even length. Values with a VR of OB shall be padded with a single trailing​ NULL byte value (00H) when necessary to achieve even length.​

AllnewVRsdefinedinfutureversionsofDICOMshallbeofthesameDataElementStructureasdefinedinSection7.1.2withreserved​ bytes after the VR and a 32-bit unsigned integer VL (i.e., following the format for VRs such as OB or UT), and may or may not permit​ undefined length.​

Note​

1.​Since all new VRs will be defined as specified in Section 7.1.2, an implementation may choose to ignore VRs not recog-​ nized by applying the rules stated in Section 7.1.2.​

2.​When converting a Data Set from an Explicit VR Transfer Syntax to a different Transfer Syntax, an implementation may​ copy Data Elements with unrecognized VRs in the following manner:​

•​If the endianness of the Transfer Syntaxes is the same, the Value of the Data Element may be copied unchanged​ and if the target Transfer Syntax is Explicit VR, the VR bytes copied unchanged. In practice this only applies to Little​ Endian Transfer Syntaxes, since there was only one Big Endian Transfer Syntax defined.​

•​If the source Transfer Syntax is Little Endian and the target Transfer Syntax is the (retired) Big Endian Explicit VR​ Transfer Syntax, then the Value of the Data Element may be copied unchanged and the VR changed to UN, since​ being unrecognized, whether or not byte swapping is required is unknown. If the VR were copied unchanged, the​ byte order of the value might or might not be incorrect.​

•​If the source Transfer Syntax is the (retired) Big Endian Explicit VR Transfer Syntax, then the Data Element cannot​ be copied, because whether or not byte swapping is required is unknown, and there is no equivalent of the UN VR​ to use when the value is big endian rather than little endian.​

The issues of whether or not the element may be copied, and what VR to use if copying, do not arise when converting​ a Data Set from Implicit VR Little Endian Transfer Syntax, since the VR would not be present to be unrecognized, and​ if the data element VR is not known from a data dictionary, then UN would be used.​

An individual Value, including padding, shall not exceed the Length of Value, except in the case of the last Value of a multi-valued​ field as specified in Section 6.4.​

Note​

ThelengthsofValueRepresentationsforwhichtheCharacterRepertoirecanbeextendedorreplacedareexpresslyspecified​ in characters rather than bytes in Table 6.2-1. This is because the mapping from a character to the number of bytes used​ for that character's encoding may be dependent on the character set used.​

Escape Sequences used for Code Extension shall not be included in the count of characters.​

- Standard -​

a floating point number. A fixed point number shall contain only​the SPACE character of​

DecimalString​

thecharacters0-9withanoptionalleading"+"or"-"andanoptional​Default Character Repertoire​ "." to mark the decimal point. A floating point number shall be​

conveyed as defined in ANSI X3.9, with an "E" or "e" to indicate​ the start of the exponent. Decimal Strings may be padded with​ leading or trailing spaces. Embedded spaces are not allowed.​

Note​

Data Elements with multiple values using this VR may​ not be properly encoded if Explicit-VR Transfer Syntax​ isusedandtheVLofthisattributeexceeds65534bytes.​

- Standard -​

matching (see​ PS3.4), the length​ is 54 bytes​ maximum.​

- Standard -​