Improved SPECT using simultaneous emission and transmission tomography.

A method is proposed to simultaneously record single photon emission and transmission tomographic (SPECT) studies to produce a map of attenuation coefficients (mu) for the body. A dual radionuclide SPECT acquisition is performed with a transmission source attached to a rotating gamma camera of lower energy than the emission radionuclide. Scatter from the emission source into the transmission window is removed by subtracting the predicted scatter distribution. The transmission image is then reconstructed to yield the map of attenuation coefficients for anatomic display or attenuation correction purposes. Experimental work has shown that the method can accurately derive mu values to +/- 2.5% in both phantom and patient studies, without increasing acquisition time. Preliminary attenuation correction experiments have demonstrated an accuracy of better than 5% for estimated activity.