Hi,

We're looking to make a stability/QA phantom, probably following the BIRN recipe, and we of course want to do it on the cheap (we can buy one for about $1K, but we'd like to spend substantially less. The hitch is finding the appropriate plastic sphere to make the phantom in. Where do these come from? Do the manufacturers all make their own? I'm thinking of something like the GE Braino phantom or one of the acrylic spheres that come with the Trio. I've looked for these things over the years, but always come up short...

Any help would be appreciated,
Blaise

Hi Blaise,

I've looked over the years for sources of plastic spheres with not much success. In years past I was after small sizes for calibration samples, but found that companies make spheres by gluing two almost-spherical halves together which results in something that is not really a sphere but more like a slightly elongated sphere. To get a perfect sphere, I think you really have to use a single block of material and mill it out - which is why they are so expensive.

regards,

Karl Helmer

Hi Blaise,
I have the same problem. Found several companies on the web who produce plastic or acrylic spheres with various diameters but the problem is that they only ship large orders. I can give you some links if you contact me at bmaedler@physics.ubc.ca.
recently I found acrylic hemispheres in a art supply store (something like Michael's). the largest diameter is 12cm and you would need to glue the hemispheres together and of course also fill them.
The latter seems to be the biggest challange. To release all air one has to fill the sphere completely. That makes sealing the remaining hole a problem. Also due to temperature contraction and expansion these spheres tend to leak over time.
To order some type of spherical phantom that might work for you, have a look at:
http://www.phantomlab.com/magphan.html

Good luck and let me know if you find something else.
Burkhard