<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue-Light, Helvetica Neue Light, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:13px"><div id="yui_3_16_0_ym19_1_1461211897848_2977"><span id="yui_3_16_0_ym19_1_1461211897848_3976">Hi <b>Lorena</b>,</span></div><div id="yui_3_16_0_ym19_1_1461211897848_2977"><span><br></span></div><div id="yui_3_16_0_ym19_1_1461211897848_2977" dir="ltr"><span id="yui_3_16_0_ym19_1_1461211897848_3066">Yes, it is possible. You just need to store energy and position of the detected photons, and using them you can derive the Compton scattering angle. <br><br>Regarding the problem happened after removing the collimator: As far as I experience, you can easily remove the collimator in the SPECThead system without any problem. The problem you faced may come from the geometry, still attaching the PhantomSD to a deleted volume (here, the collimator), and so on. <br><br>The SPECThead system well suites what you need, I think.<br><br>Good luck,</span></div><div></div><div id="yui_3_16_0_ym19_1_1461211897848_2978"> </div><div class="signature" id="yui_3_16_0_ym19_1_1461211897848_3005"><div id="yui_3_16_0_ym19_1_1461211897848_3030"><span style="font-size:small;font-weight:bold;" id="yui_3_16_0_ym19_1_1461211897848_3029">Hojjat </span></div><div id="yui_3_16_0_ym19_1_1461211897848_3004"><div id="yui_3_16_0_ym19_1_1461211897848_3003"><br></div><u style="color:rgb(34, 34, 34);font-family:arial, helvetica, sans-serif;font-size:small;background-color:rgb(255, 255, 255);"></u></div></div></div></body></html>