Recently, however, there has been renewed interest in transmission measurements due to several complimentary developments: New joint emission-attenuation reconstruction algorithms permit extraction of a great deal of attenuation information from emission-only [14, 15] or simultaneous emission-transmission [16] data.
Alternative approaches such as PET/MRI [11] or reconstruction methods that jointly estimate emission and attenuation [12] may eliminate altogether the need for additional radiation exposure to estimate photon attenuation.
Monte Carlo simulations have been performed to model the gamma ray emission and attenuation properties of common rocks.
A preliminary study on one patient indicates that the MLAA+ algorithm results in better reconstructed emission and attenuation images as compared to the MLAA algorithm.
A total of 288 image data sets were reconstructed with varying acquisition durations for emission and attenuation data with and without scatter and prompt gamma correction, and further analysed regarding image quality and diagnostic performance.
The major difference between emission-based attenuation map completion, as suggested in reference [40], and emission-based hardware attenuation estimation, as proposed in this work, is that in the former case, the missing anatomy has non-zero tracer uptake ("warm objects") while in the latter case, the hardware components contain zero activity ("cold objects").
This is in contrast to the emission-based attenuation estimation of warm objects, as in reference [40], where all LORs crossing the object do contain emission data and thus attenuation information.
Figure 5 Representative view of CBF, OEF, and CMRO2 for Group-2 by transmission- and emission-based attenuation correction.
For further shortening, one option is to eliminate the transmission scan by applying an emission-based attenuation correction.
The validity of the present method was tested by comparing parametric values with emission-based attenuation correction to those with transmission-based correction.
In the present study, we generated CBF, OEF, and CMRO2 images applying an emission-based attenuation map rather than transmission scan data.
