Three-dimensional reconstruction in nuclear medicine emission imaging

Methods of three-dimensional isotope distribution reconstruction from multiple two-dimensional views are similar to those employed in astrophysics, electron microscopy, and radiology; however, photon attenuation must be taken into account. Successful quantitation of the three-dimensional distribution of isotopes has been achieved using the iterative least-squares technique, but not the Fourier technique. The iterative least-squares technique is superior to other techniques because it handles noise and has been successfully modified to incorporate attenuation. The method has been implemented on the CDC-6600/7600 and on the small computer HP-2100A in FORTRAN. In our first implementation, approximately 20 min of processing per section are required by the small machine. Most algebraic reconstruction techniques do not account for noise, but can reconstruct a section in approximately 1 min. without attenuation correction. Fourier transform techniques are approximately 80 times faster than the least-squares method, but do not handle noise or attenuation.