Performance changes of an Anger camera in magnetic fields up to 10 G.

Magnetic fields much larger than the earth's magnetic field can exist many feet away from NMR units. Gamma camera manufacturers already shield photomultiplier tubes from the earth's magnetic field (approximately 0.5 G). The effects of larger magnetic fields on an Anger camera, were made in fields up to 10 G. Sensitivity and positional stability were studied as a function of gantry angle in a magnetic field. Scans of uniform and hot rod sections of and ECT phantom were also performed. No visible artifacts were found in reconstructions of the phantom measured in a 5-G magnetic field, although some small sensitivity and linearity effects did exist. In 10-G fields, planar and reconstructed images were grossly distorted. Magnetic shielding placed across the collimator reduced the influence of the magnetic field but at a cost in sensitivity that varies with photon energy.