Available in LEADTOOLS Medical Imaging toolkits.
Dicom Annotations: Converting Between LEADTOOLS Annotations and DICOM Annotations
LDicomDS::ConvertDicomAnnObjToLEADAnnObj
LDicomDS::ConvertLEADAnnObjToDicomAnnObjs
LDicomDS::OnConvertLEADAnnObjToDicomAnnObj