TABLE 1.

Physical Properties and Cost-Effectiveness of Commercial SPECT Transmission Sources

Isotope201Tl153Gd99mTc
Half-life73 h240 d6.02 h
Energy (keV)69–81 (+167)97 + 101140
Physical formulationSolutionSolidSolution
Mode 99mTc emissionSimultaneousSimultaneousSimultaneous T1E2*
Mode 123I emissionSequentialSimultaneousSequential/simultaneous†
Typical total source strength150–300 MBq1–2.5 GBq370–740 MBq
Replacements/month100.0640
Total cost/y ($) for average source strength±4000±6000±700

  • ↵* T1E2 = simultaneous transmission and emission.

  • ↵† Simultaneous can give cross-scatter problems.