POSTEROLATERAL DEFECT OF THE NORMAL HUMAN HEART INVESTIGATED WITH NITROGEN-13-AMMONIA AND DYNAMIC PET

The posterolateral defect is a common artifact seen when static N-13-a mmonia imaging with PET is used to assess myocardial perfusion. The ai m of this study was to compare dynamic and static N-13-ammonia PET and to obtain more insight into the cause of the posterolateral defect. M ethods: Dynamic N-13-ammonia PET was performed in 19 healthy nonsmokin g volunteers at rest. Perfusion was assessed in the early phase of the study using a curve fit method over the first 90 sec. Nitrogen-13 acc umulation (static PET) was assessed 4 to 8 min after injection. Each s tudy was normalized to a mean of 100. The average distribution of norm alized perfusion and activity was calculated in 24 segments. Heterogen eity of both activity and perfusion distribution were assessed and the activity distribution was compared with perfusion distribution. Resul ts: Perfusion distribution was homogeneous, with the exception of the inferior and apical regions. Activity distribution was inhomogeneous, with a lower activity in the posterolateral and apical regions. In the whole left ventricle, significant differences in distribution were fo und between static and dynamic imaging. Conclusion: Perfusion distribu tion was significantly different on dynamic images compared to static images. The posterolateral defect was not found on dynamic images. The posterolateral defect and other inhomogeneities in activity distribut ion are caused by tracer-dependent features, probably a redistribution of metabolites of N-13-ammonia.