Experimental verification of 3D detector response compensation using the OSEM reconstruction method

Detector blurring is a major factor in SPECT image degradation and several methods to include detector response compensation (DRC) into iterative reconstruction algorithms have been proposed. Here, we present a study to validate and quantify the performance of such correction using an approach that we have developed and which combines 3D DRC with a non uniform attenuation correction. The objective of this study was to estimate what is the best spatial resolution that could be experimentally achieved in an image reconstructed with both attenuation and resolution recovery corrections. For this purpose we have performed several tests involving physical phantoms and computer simulations. In experiments with capillary tubes in air the resolution came close to the pixel size and was equal to 3.6 mm. DRC convergence was slower when background activity was present but still resulted in an excellent, close to the pixel size, resolution in the image. Similar results were obtained for extended sources scanned in air and with background activity. In this last case, however, the speed of convergence of the reconstruction algorithm was substantially decreased. Additionally, we present the results of a study involving a simulated wrist model which showed that hot and cold defects of the size equal to ≈6 mm can be detected when DRC was used. In summary, our experiments and simulations have demonstrated that including 3D DRC in the iterative reconstruction algorithm resulted in great improvement of image resolution and noise reduction that increased visibility of small details