Iterative Reconstruction with Attenuation Compensation from Cone-Beam Projections Acquired via Nonpl - Nuclear Science, IEEE Transactions on

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy’s cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy’s condition was derived for an attenuation-free situation, we hypothesize that an artifact-free reconstruction can be obtained even if the cone-beam data are attenuated, provided the imaging orbit satisfies Tuy’s condition and the exact attenuation map is known. In our studies, emission data are acquired using nonplanar circle-and-line orbits to acquire cone-beam data for tomographic reconstructions. An extended iterative ML-EM (maximum likelihood–expectation maximization) reconstruction algorithm is derived and used to reconstruct projection data with either a pre-acquired or assumed attenuation map. Quantitative accuracy of the attenuation corrected emission reconstruction is significantly improved.