Forgotten zeros in histogram data format

General Discussions
1

Hello fellow CASToR users,

Do you know what happens if, for Gate simulation output data that I converted myself into CASToR data in histogram format, I forgot to put 0 (zero) in the histogram bins (LORs) that had no coincidences? In fact, these bins were just never created in my conversion code. Does CASToR automatically put a zero in them when it sees they are not initialized or am I then reconstructing wrongly, with weird stuff possibly happening? The images I reconstruct in this (possibly bad) manner do not exhibit visible artifacts, but I still wanted to know if this method is fundamentally wrong.

Thanks for your insights,

Étienne

2

Hi,

Generally in CASToR we avoid doing hidden implied actions, such as filling in missing data. If your histogram datafile does not contain some LOR bins, the reconstruction will be performed as if your scanner were not able to detect coincidences at these LOR bins. This might not show in the reconstructed image if you have few or irrelevant missing bins. However, it might easily become an issue in other cases. I would recommend always putting empty bins in the datafile.

Best,

Marina Filipovic