A TRIPLE-HEAD SPECT SYSTEM WITH PARALLEL-HOLE COLLIMATORS OF DIFFERENT ACCEPTANCE ANGLES

We proposed to use three different parallel-hole collimators for a tri ple-head SPECT system. One of the collimators had a small collimator a cceptance angle to provide ultra-high spatial resolution and the other two had larger collimator acceptance angles to achieve high counts. A new 2D reconstruction algorithm that combined the data acquired from different collimators was derived to take advantages of both high reso lution and high sensitivity. The algorithm was evaluated using a compu ter-simulated matrix of spherical sources. For noise-free data, the ac curacy (mainly determined by spatial resolution) obtained from combina tion of the collimator acceptance angles of 1.35, 4.05 and 6.75 degree s (or 1.35, 5.40 and 9.45 degrees) was slightly inferior to that obtai ned from three same LEHR collimators (with a 2.70 degrees collimator a cceptance angle). This is because the modulation transfer function (MT F) resulting from three different collimators decreases more quickly a t low frequencies but becomes comparable at high frequencies as compar ed with the MTF of the 2.70 degrees collimator. With noisy data, howev er, the image quality obtained with three different collimators was be tter than that resulting from any combinations of three same collimato rs. The improvement was only achieved by using the derived algorithm, while the conventional FBP algorithm did not improve image quality eve n with the same collimator configuration. (C) 1997 Elsevier Science Ir eland Ltd.