The approximate trajectories of the gamma photons are reconstructed using information from the various detectors and collimators in the case of gamma cameras. Despite the inaccuracies of the individual paths, the large number of gamma photons allows for a highly accurate final image. Even in the smallest samples of radioactive substances, millions of gamma rays are emitted every second (remember that atoms are such tiny particles that there are millions of millions of millions of them in the least gram of matter). With such high numbers of particles, the calculations involved are so complex that they would be impossible without the help of modern computers.