Development of a flexible end-shield using tungsten curtains for 3D PET

In the three-dimensional (3D) acquisition of positron emission tomograph (PET) without septa, random and scatter due to the events from the outside the field of view (FOV) become a serious problem. They decrease the signal to noise ratio and quantitation of the image. They also limit the count rate capability of the PET system. To reduce these effects, we developed an end-shield using tungsten curtains. The end-shield consists of a mobile stand, a cylindrical support, and flexible tungsten curtains. The tungsten curtains are made of 4 layers of 30 mm square, 1 mm thick tungsten plates contained in pockets of cloth. Because the tungsten curtains are flexible, it could be used quite safely even in the body studies. Reduction of random and scatter were observed by using the end-shield in both phantom and human studies. Results indicate that the new end-shield using tungsten curtains is promising to improve the image quality of the PET studies.