什么是 DICOM IOD（信息对象定义）？

Question

我正在尝试更好地理解 DICOM 以准备有关 SOP 的演示文稿。

我还没有真正理解 IOD（信息对象定义）实际上是什么。

例如，如果我有一个内部包含封装文档的数据集，那么 IOD 到底是什么？是整个数据集，里面的PDF，单个标签还是标签组？

Answer 1

If I for example had a dataset with an encapsulated document inside, what exactly would be considered an IOD? Is it the whole dataset, the PDF inside, single tags or tag groups?

其中

None 将被视为 IOD，因为您在这里谈论的是 IOD 的 instance。 IOD 应改为 class。

请参考下图。 SOP Class 被定义为 DICOM 服务元素（命令）和对象的组合。该对象由信息对象定义 (IOD) 定义。因此，您的数据集是 IOD 的 实例 ；它本身不是 IOD。为简单起见，您可以将 IOD 视为模板；您从此模板创建实际实例（数据集）。 IOD 进一步分为 Composite IOD 和 Normalized IOD。

如果您从编程语言的角度来看这一点，您可以将 IOD 视为您的编程语言中的 class。它是 class 定义的；尚未实例化。然后在某处，您创建了此 class 的 实例 并设置了 attributes/properties。这是您的数据集。单个 tag/element 类似于 属性。数据集中的PDF文档只是一个属性的值。模块的概念类似于面向对象编程的组合概念。

6.1 Information Object Definition
An Information Object Definition (IOD) is an object-oriented abstract data model used to specify information about Real-World Objects. An IOD provides communicating Application Entities with a common view of the information to be exchanged.

_{Major Structures of DICOM Information Model}

An IOD does not represent a specific instance of a Real-World Object, but rather a class of Real-World Objects that share the same properties. An IOD used to represent a single class of Real-World Objects is called a Normalized Information Object. An IOD that includes information about related Real-World Objects is called a Composite Information Object.

_{Source - Specifications (DICOM PS3.4 2020a)}

此外，Roni on DicomIsEasy 更好地解释了这一点：

The classes of the DICOM static data model are called SOP Classes and are defined by IOD’s – Information Object Definition. IOD’s are specified in Appendix A of chapter 3 of the standard. An IOD is a collection of Modules and a Module is a collection of elements from one information entity that together represent something. The modules are also defined in chapter 3 of the DICOM standard in appendix C. Two object oriented concepts, composition and reuse, that are used by DICOM is the Modules that are parts shared between different IOD’s.

other很好的资源，深入浅出。