Hi, Guocheng, Have you checked your septa definition? It's only 3 long and thin strips along Y-axis near the center. It does not look like a normal septa definition. And what's your source and detector definition? When you say "there is no difference" you mean "exactly the same" or "statistically". If they are statistically the same that might because the septa thickness is too small (0.5mm) and the number of septa is small (only 3) too. Yuxuan <table width=100%> <tr valign=top> <td> <td>吴国城--东软派斯通 <wuguocheng@neusoft.com> Sent by: gate-users-bounces@lists.healthgrid.org 11/27/2007 12:57 AM <td>                To:        gate-users@lists.healthgrid.org         cc:                 Subject:        [Gate-users] septa setting</table> <img src=cid:_2_093400003F48005C7EBC862573A0> Hi gate-users I tried to set septa in my simulation system with following scripts: #       SEPTA /gate/head/daughters/name septa /gate/head/daughters/insert box /gate/septa/placement/setTranslation -1.5 0.0 0.0 cm /gate/septa/geometry/setXLength 5.0 cm /gate/septa/geometry/setYLength 32.0 cm /gate/septa/geometry/setZLength .5 mm /gate/septa/setMaterial Tungsten /gate/septa/repeaters/insert cubicArray /gate/septa/cubicArray/setRepeatNumberX 1 /gate/septa/cubicArray/setRepeatNumberY 1 /gate/septa/cubicArray/setRepeatNumberZ 3 /gate/septa/cubicArray/setRepeatVector 0.0 0.0 10.0 cm /gate/septa/vis/setColor blue /gate/septa/attachPhantomSD Or # /gate/septa/attachCrystalSD.   I tried to analysis the total counts with benchmark.C. But I find that there is no difference within or without setting septa. Any suggestion will be appreciated.   Guocheng Wu Software Department Neusoft Positron Medical Systems Co.,Ltd.   No.2 Xin Xiu Street, Hun Nan New District, Shenyang 110179, PRC   Tel: +86 24 836 61980 Fax: +86 24 836 61796 Mobile: +86 13604039065 Email: wuguocheng@neusoft.com Website: <a href=http://medical.neusoft.com/>http://medical.neusoft.com</a>   <hr>Confidentiality Notice: The information contained in this e-mail and any accompanying attachment(s) is intended only for the use of the intended recipient and may be confidential and/or privileged of Neusoft Group Ltd., its subsidiaries and/or its affiliates. If any reader of this communication is not the intended recipient, unauthorized use, forwarding, printing, storing, disclosure or copying is strictly prohibited, and may be unlawful. If you have received this communication in error, please immediately notify the sender by return e-mail, and delete the original message and all copies from your system. Thank you. <hr><tt>_______________________________________________ Gate-users mailing list Gate-users@lists.healthgrid.org http://lists.healthgrid.org/mailman/listinfo/gate-users </tt>