( ( ( ( ( ( ( The ( radioactive substance ) ) ( attached ( to ( the tracer ) ) ) ) ( then ( ( emits ( gamma rays ) ) ( -LRB- ( ( like X-rays ) -RRB- ) ) ) ) ) , ) and ) ( ( these ( gamma rays ) ) ( can ( be ( detected ( using ( a ( gamma camera ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (JJ radioactive) (NN substance)) (VP (VBN attached) (PP (TO to) (NP (DT the) (NN tracer))))) (ADVP (RB then)) (VP (VBZ emits) (NP (NN gamma) (NNS rays)) (PRN (-LRB- -LRB-) (PP (IN like) (NP (NNS X-rays))) (-RRB- -RRB-)))) (, ,) (CC and) (S (NP (DT these) (NN gamma) (NNS rays)) (VP (MD can) (VP (VB be) (VP (VBN detected) (S (VP (VBG using) (NP (DT a) (NN gamma) (NN camera)))))))) (. .)))
The radioactive substance attached to the tracer then emits gamma rays (like X-rays), and these gamma rays can be detected using a gamma camera.
(ROOT (S (NP (DT A) (NN tracer)) (VP (VBZ is) (NP (NP (DT the) (NN name)) (PP (IN for) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB be) (VP (VBN used) (S (VP (TO to) (VP (VB follow) (NP (NP (DT the) (NN pathway)) (PP (IN of) (NP (DT that) (NN substance)))) (PP (IN through) (NP (DT some) (NN structure))))))))))))))) (. .)))