There’s probably multiple reasons why DICOM does not support PNG. Most compression formats in DICOM are those published as official standards in the JPEG family

There’s probably multiple reasons why DICOM does not support PNG. Most compression formats in DICOM are those published as official standards in the JPEG family from ISO. The original JPEG from ‘92 already included a Lossless mode which supports 16/12/8 bit color and monochrome and is very fast to encode and decode. All of those were important features. Adding PNG later would not benefit anyone: it can not handle all of these usecases, it is usually slower and it came later.