<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'> Hi all,   I need to speed up SPECT simulation because it costs two days or more to get the results even when I set low activity.   One of the methods I think is to stop recording its information after knowing one photon already been scattered. I don't know how to realize it in GATE.   Does anyone know how to do it? Or are there any other ways to speed up the simulations?   Thanks,   Dan    <hr />Get news, entertainment and everything you care about at Live.com. <a href='http://www.live.com/getstarted.aspx ' target='_new'>Check it out!</a></body> </html>