Myocardial uptake of N-13 following L-(N-13)-glutamate administration and its relation to Tl-201 scintigraphy

In most instances N-13-ammonia (t1/2=9.96 min) was produced by a 16O (p,α) 13N-reaction during the irradiation of H2O with a beam current of 10/uA. Subsequently it was enzymatically converted to L-(N-13)-glutamate. 4-10 mCi of the radiopharmaceutical were administered in 48 patients. In 32 patients quantitative whole-body imaging was performed using a non-tomographic positron scanner which allows for absorption and half-life correction. Regional myocardial N-13 distribution was assessed and compared with Tl-201 sequential scintigraphy in 16 patients by using a gamma camera. 6 min.p.i. the myocardial N-13 uptake averaged 5.3 +- 0.8% of the amount incorporated. Coronary patients (N=19) tended to have higher percentage values and a higher N-13 release within a 10 min interval than control individuals (N=13). Patients showing diminished initial Tl-201 accumulation in a myocardial segment in which redistribution was observed on delayed images, has increased N-13 activity in the segment involved (N=8). Patients with persisting Tl-201 defects showed reduced N-13 uptake (N=8). The results suggest that the use of L-(N-13)-glutamate may facilitate the differentiation between different degrees of myocardial disorders caused by coronary heart disease