RegEx remove duplicate need help

Hi, not good at RegEx and trying to remove some duplicate values.
data is in CSV, part of it looks like this:

"/content/7/66345/images/590009.jpg , "/content/7/66345/images/590009.jpg , "/attachments/fe519c1e91c5e4983a70a2512fd5788b.jpg , "/content/7/66345/images/590009.jpg , "/content/7/66345/images/590009.jpg , "/attachments/4956e4fe56b59135c086605c9gyye.png
"/content/1/3968663/images/856609.jpg , "/attachments/086605c7c6e4fe56b59135c11b.jpg , "/content/1/3968663/images/856609.jpg , "/attachments/086605c7c6e4fe56b59135c11b.jpg
"/content/1/1458767/images/856657.jpg
"/content/1/1448511/images/856373.jpg

I am trying the following using Notepad++:
\w+\.+jpg|\w+\.+png(?:^|\G)(\b\w+\b),?(?=.*\1)

it does select one image by one image when clicking find, but I am not sure how to delete duplicates,
when I replace it with empty, it removes all, I want to let the first image remain and delete the duplicates, Anyone can help me with the code, please?
I don't want to remove the line, because it could mess with the CSV file, removing the extension of the duplicate image is OK,
Thanks for your help.