s, corrections, etc.) before proceeding. For |options.precompute_lor 
% = true| you also need to perform the precomputation phase if it hasn't been 
% performed before. Note that if you want the measurement data to be precorrected, 
% you need to do that manually. Corrections during reconstruction are applied 
% automatically, though in some cases (such as randoms correction) you need to 
% select the correction data when it is prompted.
% 
% For the reconstruction, implementations 1, 3 and 4 are supported 