<html><head></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div dir="ltr" data-setdir="false"> <div><div dir="ltr" data-setdir="false"><span>Dear community,</span></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">I'm working on the dosimetry using SPECT/CT images. For MC simulations, SPECT images in units of Bq/voxel are voxelized and inserted as the voxelized source. I know the format/file structure of the activity_range.dat file but have some confusion about activity values that we need to set! The data I have is the patient scan, and it has few lesions in the liver, a few on the abdomens, etc. And I want to simulate the dose for all lesions as well as organs-at-risk.</div><div><br></div><div dir="ltr" data-setdir="false">I want to define the voxel range and activity for lesions and organs such as the liver, kidneys, spleen, etc. So, to determine the voxel range for, let us say (lesion in the liver), one needs to segment the lesion and calculate its voxel min and a max of segmented volume, right? And subsequently, the volume segmentations are required for all other lesions and organs? From this, we can get information of voxel min and max; hence voxel range and the summation of all voxel values give the total activity value in that segmented volume. And we need to use the average activity per voxel to define the activity column in the activty_range.dat file? Is this the method one needs to implement to generate the activity_range.dat file? Is this the right direction?</div><div><br></div><div>I would be grateful if you share your experiences regarding this activity range file and hugely appreciate any thoughts or suggestions.</div></div></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Thank you.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Regards,</div><div dir="ltr" data-setdir="false">Ashok</div></div></body></html>