Templates are a critical part of a structured report (SR); they create order for the infinite number of possible structures that one can create using the SR building blocks. Either a template is communicated as part of the generic SR SOP Class, or a separate SOP Class is defined, which is constrained for using only specific template(s).
There are three different SOP Classes of the generic SR type. These are the comprehensive, enhanced and basic text. These SOP Classes are constrained with respect to the information contained and the relationships used. The basic text SR is the most constrained, followed by the enhanced and comprehensive SRs.
If an application can be clearly identified, such as a standard routine measurement as part of an Ultrasound exam, there are special SOP Classes defined requiring the use of a special defined template with the specific SR. This template can be viewed as a standard "form", which makes it easy for a producer to fill in and a reader to interpret. It is also possible to exchange a template as part of the three generic SR SOP Classes.
The body of a template is highly constrained. It can only contain certain content nodes and relationships in a very particular order. A good example of a template is the one that is specified by IHE - the simple report template, containing text, an image reference and a measurement. The text itself can have a relationship with another image and measurement using the inferred from relationship.