Vintage mammography phantom

Just about every medical physicist has a collection of old test gear, phantoms, test objects ,meters and the like.

A few years ago, while rummaging through the equipment cabinet in our store room/library/lab, I came across a variant of a mammography phantom that I hadn’t seen before. Instead of the normal pink wax insert, this one had 16 wax squares of different colours.

Old RMI mammography phantom SN 152-1015
Old RMI mammography phantom SN 152-1015

Aside from the curved bit of plastic at one end of the phantom (a test object, not a ghostly apparition), it’s the same size as the conventional ACR accreditation phantom. Reminds me of one of those sliding number/picture puzzles where you have to slide the squares around to reconstruct the image.

Old RMI mammography phantom SN 152-1015
Old RMI mammography phantom SN 152-1015 side view

I let it sit on my book shelf along with some of the other pieces in the collection. A few months ago, I decided it was time to have a look and see what the inside of the wax blocks looked like.

Old RMI mammography phantom SN 152-1015
Old RMI mammography phantom SN 152-1015

Looks like at some point in its history, the pieces got a little scrambled and reinserted a bit randomly. I was expecting that each colour block would represent a different density. Instead there are the usual fiber, speck, and mass groups, but not nearly as uniformly placed as in the accreditation phantom.

I don’t know how old this phantom is or what time frame it might have been used at work. The only mammography phantom I was familiar with before this one was the pink one, so possibly before 1996 at least. Definitely pre-1999.

If anybody out there happens to know anything about this style of mammography phantom, let me know.