ACR-NEMA is the original name of what is today called the DICOM standard. The ACR-NEMA standard was developed jointly by ACR (the American College of Radiology) and NEMA (the National Electrical Manufacturers Association).
The ACR-NEMA standard was originally published in 1985, and an updated version, ACR-NEMA 2.0, was published in 1988. The goal of the standard was provide a vendor-independent set of rules for exchanging digital medical images. One limitation of ACR-NEMA was that it was defined for point-to-point connections only, rather than from use in a network environment.
The third version of the standard, released in 1993, was renamed to DICOM (Digital Imaging and Communications in Medicine). DICOM 3.0 added network support, expanded object definitions (both image and non-image), and introduced conformance statements. The “3.0” was retained to reflect its heritage from ACR-NEMA.