<html> <head> <style> .hmmessage P { margin:0px; padding:0px } body.hmmessage { FONT-SIZE: 10pt; FONT-FAMILY:Tahoma } </style> </head> <body class='hmmessage'> I am planning to model an x-ray imaging system that includes an x-ray tube, a detector and a phantom. I guess I should use the 'scanner' system type, right? But I am not sure how to divide my model into those five 'levels'. From the user guide, there is not strict definition of this 'levels'. The concept of system is quite confusing to me. And anybody can recommend more info about the concept of 'system'? And is there any existing model of x-ray tube with GATE?<br><br>Thanks~<br><br>Weixing Cai<br><br /><hr />Your PC, mobile phone, and online services work together like never before. <a href='http://clk.atdmt.com/MRT/go/108587394/direct/01/' target='_new'>See how Windows® fits your life</a></body> </html>