The Modality Performed Procedure Step Service, commonly known as MPPS, provides a mechanism for modalities to pass information about the imaging they are performing back to the RIS and/or PACS. There are 2 different types of message, and normally, one of each is sent, in order:
The MPPS complete message also includes a list of all the image instances created during the procedure step, allowing a PACS to be able to tell whether it has received them all. Under the IHE model, the modality is only required to send its MPPS messages to one destination, which can be either the RIS or the PACS, but that initial entity is then required to send them on to the other.
MPPS is fully supported by DicomObjects and examples are available for SCU & SCP use.