Prepare noisy data

[ckolbPTB]

For two example datasets

• Provide code to add Poisson noise by @KrisThielemans
• Calculate coefficient of variation (CoV) in background ROI of OSEM reconstruction
• Add Poisson noise using numpy (see https://github.com/SyneRBI/SIRF-Exercises/blob/master/notebooks/PET/Solution_Snippets/image_creation_and_simulation_01_noisy_data.py) with different strength
• Estimate relationship between Poisson noise strength and CoV
• Once SIRF can be build again we can use Poisson noise generation script for PETRIC2 SIRF#1321 instead of numpy to generate Poisson noise

For all datasets

• Chose desirable CoV, probably lower than original Vision600_zrNEMA data
• Add Poisson noise to sinograms to achieve comparable CoV in all datasets