Podtrac measurement can be used when hosting your podcast on Castos. You can read the their help article here:
Here are the steps to follow:
Log in to your Castos account
Click Settings
Select Feed Details
Select Advanced
Enter the Podtrac prefix in the Tracking Prefix field. The Podtrac prefix is: https://dts.podtrac.com/redirect.mp3/
Click Save Podcast Details