The idea actually is from a German customer who wants to use his RT-smartIMRT cylindrical phantom for the entire QA chain, from CT way through to delivery verification. So the phantom should fit inside the RT-smartIMRT box.
The Euromechanics medical phantom 'Easy Cube' is available with inhomogeneity inserts for lung, adipose, muscle, bone and artificial limb, which come as rods of 17mm diameter.
Take a RW3 block which fits inside the smartIMRT in different orientations, drill the holes for the above inserts, add some geometrical structures for dimension and distortion checks and add test tubes for reference liquids and tissue.

And combine with another smart tool:  RT-smartCUBE, the universal miniature phantom which now contains resolution/contrast tests for medical imager and 'Virtual Tumors'.

This is Revolutionary New: turn your RT QA phantoms  within minutes to a 'Virtual Patient' for the entire Process QA, from Imaging to Treatment.

RT-smartCTQA is a RW3 block with 30 x 30 cm footprint at 7 cm height. It fits inside the RT-smartIMRT in 2 orientations. 10 bore holes in the block accommodate the Inhomogeneity rods or test tubes, or ion chamber adapters as for the Farmer chamber.

The hole #5 is in the middle of the phantom, and the chamber reference point in ISO center. 

As all the faces of the RW3 block have to be machined on CNC tools it is easy and inexpensive to add some simple structures. On 4 faces there are identical 'step funnel holes', with diameters and depth with step sizes from 1 to 5 cm.

On the upper and lower faces are plastic pins inserted, perpendicular and with length of 200 mm each.

There is space in the rear part which the customer can use to insert gold markers for example.