Using image_tag in Action Mailer?

I’m trying to send a HTML formatted email with Action Mailer and
everything works fine except for when I try to use a Rails image_tag in
my email template. Does anyone have experience doing this? I keep
getting this error

|undefined method `request’ for #SamplesDirectMailer:0x231d4d8|

Extracted source (around line #7):

|7:

<%= image_tag “/images/ldc.jpg” %>
|

I’ve also tried “…/…/images/ldc.jpg” and a few other paths
If I remove the image_tag I receive the email just fine… and yes the
image is in the /images dir

Thanks in advance for the help,
Chris