( ( Like SPECT ) ( , ( ( PET images ) ( ( are ( created ( by ( detecting ( ( gamma rays ) ( produced ( by ( ( man-made ( radioactive atoms ) ) ( injected ( into ( the patient ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Like) (NP (NNP SPECT))) (, ,) (NP (NNP PET) (NNS images)) (VP (VBP are) (VP (VBN created) (PP (IN by) (S (VP (VBG detecting) (NP (NP (NN gamma) (NNS rays)) (VP (VBN produced) (PP (IN by) (NP (NP (JJ man-made) (NN radioactive) (NNS atoms)) (VP (VBN injected) (PP (IN into) (NP (DT the) (NN patient))))))))))))) (. .)))
Like SPECT, PET images are created by detecting gamma rays produced by man-made radioactive atoms injected into the patient.
(ROOT (S (NP (NP (JJ Radioactive) (NNS atoms)) (, ,) (NP (JJ nuclear) (NNS explosions)) (, ,) (CC and) (NP (NNS stars))) (VP (VBP produce) (NP (NN gamma) (NNS rays)))))
Radioactive atoms, nuclear explosions, and stars produce gamma rays