Three Dimensional Reconstruction of 99mTc Distribution by Using Coded Aperture ECT

Tadashi Ito 1, Hidenori Otake 2, Tomio Inoue 3 and Keigo Endo 3 1 Faculty of Engineering, Gunma University,

1 Tenjin-chou, Kiryu, Gunma 376-8515, Japan, tad@rs.el.gunma-u.ac.jp

2 Gunma University Hospital

3 Faculty of Medicine, Gunma University

ABSTRACT

Coded aperture ECT is an emission computed tomography (ECT) technique. It uses a gamma camera equipped with a coded aperture in place of an ordinary parallel collimator, and reconstructs the three dimensional (3D) distribution of a radioactive isotope from projected data collected from one direction.

Since data sufficient to reconstruct 3D distribution is provided without having to rotate the camera, the data acquisition apparatus is simplified compared to SPECT, thus this type of ECT has attracted much attention in the field of medical diagnosis since the 1970's. However, reports on reconstruction of actual 3D distribution were very few. Due to the rapid increase in computer performance and the development of new algorithms such as the OS-EM method, successful results of 3D reconstruction have been obtained recently.

In this paper, we report some experimental results in 3D reconstruction of 99mTC (the most widely used radioactive drug in medical diagnosis) distribution. A cardiac (heart) phantom was used as a 3D- radiation source. We observed projections of the phantom by using a gamma camera (Shimadzu Corporation PRISM 3000) equipped with a coded aperture made of a perforated lead sheet of 2mm thickness. The pinholes on the sheet were arranged in a pattern corresponding to an M-array. We applied the OS-EM method to reconstruct 3D distribution from the projection.

Keywords Nuclear medicine, SPECT, M-array, OS-EM