An essential element of the introduction to a technical document is a statement of purpose or aim. This statement tells your reader why you are writing the document. Your purpose will be shaped by the problem you have defined. It may also be shaped by previous work on the topic (see Background).
The aim of this study was to describe the pathways taken by lymph as it flows from tissues of the head to the medial retropharyngeal lymph node, and through the node to the tracheal trunk.
--Gabrielle Belz and Trevor J. Heath, "Lymph Pathways of the Medial Retropharyngeal Lymph Node in Dogs," Journal of Anatomy