Information on meta-data from Dicom files (EI, REX)

[HendrikBE]

Dear reader,

Using Python (Pydicom) I scraped metadata from the Dicom files (kVp, mAs, EI etc.). I was wondering if you have any additional information on both the REX and EI values. I'm hoping to use them as an (indirect) metric for detector exposure but am having doubt related to the usability of these units.

In my experience both REX and EI differ between manufacturers in Europe, is this the case in the USA?

With kind regards,
Hendrik Erenstein (Hanze UAS, the Netherlands)

(Not so much an issue but regarding previous 'issues' this seems like the channel to ask this question:))