One of the new Siemens Symbia gamma cameras developed problems serious enough to require the entire head to be replaced. Naturally I took the opportunity to get in and take some pictures of the innards.
This is the head assembly with the photomultiplier tubes (PMTs) wrapped in sleeves of mu-metal. The mu-metal shields the PMTs from stray magnetic fields.
Looking down at a couple of the PMTs. To fill in the empty space at the edges, smaller PMTs are usually used.
Clear optical coupling gel helps ensure maximum light transmission between the crystal and the PMTs.
Everything is enclosed inside a lead box so that the only radiation detected comes from the front, where the patient is.
All of the signals from the PMTs are carried via these ribbon cables to the boards that process them and send them off to the acquisition computer.