Picture Archive and Communication System. It is commonly accepted that PACS provides its services using the DICOM Network Protocol.

PACS is an information technology system that provides services for archiving and restoring medical imaging documents using the DICOM network protocol standard.

A common PACS provides the following services:

Storage – Allows imaging modalities to store the images they produce by sending C-STORE commands with DICOM Instances.
Search – Allows searching for Patients, Studies, Series and Images by their attributes such for example Patient Name and ID, Study Date, and other DICOM Data Elements. The search is part of the DICOM Query/Retrieve Service and performed by sending the C-FIND command.
Retrieve – Gets a copy of documents that are stored in the PACS in the form of DICOM Instances by sending a C-MOVE DICOM Command with the keys that identify the documents. The Retrieve is part of the DICOM Query/Retrieve Service and is performed by sending the C-MOVE command.

PACS in IHE – Image Archive/Image Manager

IHE defines the Image Archive/Image Manager actor. This role is usually played by the PACS. IHE technical framework details all the transactions that the PACS should support. These transactions include in addition to storage and query/retrieve, the Storage Commitment service (SCM) that is intended for transferring ownership of previously stored instances.