DICOM 基础篇

DICOM（Digital Imaging and Communications in Medicine）即医学数字成像和通信，是医学图像和相关信息的国际标准（ISO 12052）

学习DICOM知识，建议参考DICOM3.0文档，重点关于DICOM数据篇、DICOM协议篇。

1、DICOM3.0文档说明：

自1993年DICOM3.0首次发布后，DICOM标准不断的发展，每年都会进行多次扩充和修改。目前，DICOM标准共有22个章节，但是随着网络技术的发展，第9章和第13章节关于点对点连接传输的部分已被淘汰删除。

Part 1: 引言与概述（Introduction and Overview）:

定义了文档中使用的属于并且对标准其他章节的概述。

Part 2: 兼容性（Conformance）：

定义了要求制造商精确描述其产品兼容性声明。

Part 3: 信息对象定义（Information Object Definitions）：

定义了若干个信息对象类，包括普通型和复杂型，作为医疗现实中实体的抽象定义。

Part 4: 服务类规范（Service Class Specifications）：

定义多个服务类，所有DICOM功能都通过服务类的使用来实现。

Part 5: 数据结构及编码（Data Structures and Encoding）：

定义了构造DICOM消息中传递的数据集的编码规则。

Part 6: 数据字典（Data Dictionary）：

列出了DICOM标准中所有的数据元 素定义。

Part 7: 信息交换（Message Exchange）：

定义了用于应用实体交换消息的服务和协议。

Part 8: 消息交换的网络通讯支持（Network Communication Support for Message Exchange）：

说明了DICOM实体之间在网络环境中通信服务和必要的上层协议的支持。这些服务和协议保证了应用实体之间有效地和正确地通过网络进行通信。DICOM中的网络环境包括OSI和TCP／IP两种参考模型，DICOM只是使用而不 是实现这两类协议，因而具有通用性。

Part 10: 用于介质交换的介质存储和文件格式（Media Storage and File Format for Media Interchange ）：

详细说明了在可移除介质上存储医学成像信息的通用模型。

Part 11: 介质存储应用概要（Media Storage Application Profiles）：

规定了介质存储中应用选择机制和策略。

Part 12: 用于介质交换的物理介质和介质格式（Media Formats and Physical Media for Media Interchange）：

介绍存储过程中数据和目录的格式以及管理规范要求。其中较为关键的是DICOMDIR文件，它在图像的目录分类中起着重要作用。

Part 14: 灰度图像的标准显示功能（Grayscale Standard Display Function）：

详细规范了胶片打印及各种图像显示器材的显示参数。

Part 15: 安全和系统管理概要（Security and System Management Profiles）：

DICOM标准医疗图像中包含了病人非常详细的个人资料，因此为了保障在存储传输过程中数据的安全性，有必要对信 息实施加密传输。

Part 16: 内容映射资源（Content Mapping Resource）：

定义了DICOM信息对象的结构化文档模板和信息对象中使用的代码术语集。

Part 17: 解释信息（Explanatory Information）：

此部分包含解释信息的附录。

Part 18: Web服务（Web Services）：

此部分定义了通过使用HTTP URL／URI请求来访问DICOM对象的方式以及返回结果的格式。

Part 19: 应用托管（Application Hosting）：

定义了通过插件化程序的API访问格式。

Part 20: 使用HL7l临床文档架构的成像报告（Imaging Reports using HL7 Clinical Document Architecture）：

指定使用HL7的第二版CDA生成成像报告模板。

Part 21: DICOM与其他格式之间的转换（Transformations between DICOM and other Representations）：

说明了图像标注格式与NCI注释的转换。

Part 22: 实时通讯（Real-Time Communication）：

定义了视频流或音频流关联的DICOM元数据的实时传输服务

2、DICOM标准之数据篇

后续会另外介绍数据篇，参考文档详见DICOM3.0的第3部分和第5部分。

Part 3: 信息对象定义（Information Object Definitions）：

定义了若干个信息对象类，包括普通型和复杂型，作为医疗现实中实体的抽象定义。

Part 5: 数据结构及编码（Data Structures and Encoding）：

定义了构造DICOM消息中传递的数据集的编码规则。

3、DICOM标准之协议篇

后续会另外介绍数据篇，参考文档详见DICOM3.0的第4部分、第7部分和第8部分。

Part 4: 服务类规范（Service Class Specifications）：

定义多个服务类，所有DICOM功能都通过服务类的使用来实现。

Part 7: 信息交换（Message Exchange）：

定义了用于应用实体交换消息的服务和协议。

Part 8: 消息交换的网络通讯支持（Network Communication Support for Message Exchange）：

说明了DICOM实体之间在网络环境中通信服务和必要的上层协议的支持。这些服务和协议保证了应用实体之间有效地和正确地通过网络进行通信。DICOM中的网络环境包括OSI和TCP／IP两种参考模型，DICOM只是使用而不 是实现这两类协议，因而具有通用性。

4、DICOM常见缩写和名词解释

4.1、DICOM规范声明中常见缩写

ACSE       Association Control Service Element

AE             Application Entity
AET          Application Entity Title

DICOM     Digital Imaging and Communications in Medicine

DIMSE     DICOM Messsage Service Element

MWL         Modality Worklist

OID           Object Identifier

PDU          Protocol Data Unit

PDV          Protocol Data Value

SCP         Service Class Provider
SCU         Service Class Use

4.2、DICOM规范声明中常见名词解释

名词	解释
Abstract Syntax	The information agreed to be exchanged between applications, generally equivalent to a Service/Object Pair (SOP) Class. Examples: Verification SOP Class, Modality Worklist Information Model Find SOP Class, Computed Radiography Image Storage SOP Class
Application Entity (AE)	A representation of the external behavior of an application process in terms of DICOM Network Services, Web Services and/or media exchange capabilities implemented in one or more roles. A single device may have multiple Application Entities.
Application Entity Title (AET)	The externally known name of an Application Entity, used to identify a DICOM application to other DICOM applications on the network.
Application Context	The specification of the type of communication used between Application Entities. Example: DICOM network protocol.
Association	A network communication channel set up between Application Entities.
Attribute	A unit of information in an Information Object Definition; a Data Element identified by a tag. The information may be a complex data structure (Sequence), itself composed of lower-level data elements. Examples: Patient ID (0010,0020), Accession Number (0008,0050), Photometric Interpretation (0028,0004), Procedure Code Sequence (0008,1032).
Data Element	A unit of information as defined by a single entry in the data dictionary. An encoded Information Object Definition (IOD) Attribute that is composed of, at a minimum, three fields: a Data Element Tag, a Value Length, and a Value Field. For some specific Transfer Syntaxes, a Data Element also contains a VR Field where the Value Representation of that Data Element is specified explicitly
Information Object Definition (IOD)	The specified set of Attributes that comprise a type of data object; does not represent a specific instance of the data object, but rather a class of similar data objects that have the same properties. Examples: MR Image IOD, CT Image IOD, Print Job IOD. The Attributes within an IOD may be specified as Mandatory (Type 1), Required but possibly unknown (Type 2), or Optional (Type 3), and there may be conditions associated with the use of an Attribute (Types 1C and 2C).
Module	A set of Attributes within an Information Object Definition that are logically related to each other. Example: Patient Module includes Patient's Name, Patient ID, Patient' Birth Date, and Patient's Sex.
Negotiation	First phase of Association establishment that allows Application Entities to agree on the types of data to be exchanged and how that data will be encoded.
Presentation Context	The set of DICOM Network Services used over an Association, as negotiated between Application Entities; includes Abstract Syntaxes and Transfer Syntaxes.
Private SOP Class	A SOP Class that is not defined in the DICOM Standard but is published in an implementation's Conformance Statement.
Protocol Data Unit (PDU)	A packet (piece) of a DICOM message sent across the network. Devices must specify the maximum size packet they can receive for DICOM messages.
Service Class Provider (SCP)	Role of an Application Entity that provides a DICOM network service; typically, a server that performs operations requested by another Application Entity (Service Class User). Examples: Picture Archiving and Communication System (image storage SCP, and image query/retrieve SCP), Radiology Information System (modality worklist SCP).
Service Class User (SCU)	Role of an Application Entity that uses a DICOM Network Service; typically, a client. Examples: imaging modality (image storage SCU, and modality worklist SCU), imaging workstation (image query/retrieve SCU).
Standard SOP Class	A SOP Class defined in the Standard, and that is implemented and used without any modifications.
Tag	A 32-bit identifier for a Data Element, represented as a pair of four-digit hexadecimal numbers, the "group" and the "element". If the "group" number is odd, the tag is for a private (manufacturer-specific) data element. Examples: (0010,0020) [Patient ID], (07FE,0010) [Pixel Data], (0019,0210) [private data element].
Transfer Syntax	The encoding used for exchange of DICOM information objects and messages. Examples: JPEG compressed (images), Little Endian Explicit Value Representation.
Unique Identifier (UID)	A globally unique "dotted decimal" string that identifies a specific object or a class of objects; an ISO-8824 Object Identifier. Examples: Study Instance UID, SOP Class UID, SOP Instance UID.
Value Representation (VR)	The format type of an individual DICOM data element, such as text, an integer, a person's name, or a code. DICOM information objects can be transmitted with either explicit identification of the type of each data element (Explicit VR), or without explicit identification (Implicit VR) ; with Implicit VR, the receiving application must use a DICOM data dictionary to look up the format of each data element.