Imaging in presence of strong perturbations outside the FOV

When the camera is used in high radiation environments, the major gamma emission may be outside the FOV of the camera. In this case it is important that:

1. The operator is aware of the approximate location of the main emission;
2. The image inside the FOV is not affected by this external perturbation.

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Compton cameras are superior to collimator-based systems in such situations because they can detect imaging radiation on 4π. On the Compton cameras, our camera is specially suited for those situations because:

1. It is asymmetric and thus less sensitive to perturbations;
2. It has a good signal/noise ratio. Thus, it is possible to correctly image a source of intensity 1 inside the FOV with a source of intensity >10 outside the FOV.

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Below are tests illustrating our claims:

1st experiment – no source at 0° + 0.7MBq 22Na source at 180° – We observe the 22Na source behind the camera and some noise in front of the camera.

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The noise in front of the camera

The 0.7MBq ²²Na source behind the camera

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This experiment proves the exceptional sensitivity of the Temporal camera.

2nd experiment – a weak 0.03MBq 137Cs source at 0° + 0.7MBq 22Na source at 180° – We obtain a perfect image despite the strong perturbation.

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The 0,03 MBq ¹³⁷Cs source in front of the camera

The 0.7MBq ²²Na source behind the camera

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3rd experiment – a weak 0.1MBq 22Na source at 0° + 0.7MBq 22Na source at 180° – We obtain the image with some noise, but the source is correctly reconstructed.

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The 0,1MBq ²²Na source in front of the camera

The 0.7MBq ²²Na source behind the camera

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This experiment proves the capability of Temporal camera to observe weak sources (>1:10 contrast) in the 0° sector even with strong perturbations behind.