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Increased myocardial ammonia washout may cause false positive PET/CT findings

¹ Nuclear Medicine, Zurich University, Zurich, Switzerland

1098

Objectives: Heterogeneous uptake has been reported in normal human heart investigated with 13N-ammonia and PET. Recently, hybrid PET/CT scanners (PET/CT) have become available for quantitative assessment of myocardial blodd flow (MBF) using a CT attenuation as the distribution of 13N activity has not been fully explored in PET/CT. The aim of this study was to describe the characteristics of 13N activity uptake and its interaction to other parameters such as MBF and washout (K2). Methods: In 17 healthy subjects, dynamic and static 13N-ammonia data were acquired for analyzing MBF, k2 from a dynamic image, and percent uptake from a static image. About 800MBq of 13N-ammonia was injected intravenously at rest and during adenosine infused hyperemia (Ado) and image acquisition was started simultaneously. A 17-segment model was used as recommended by the American Heart Association. Percent (%) uptake, MBF, k2, and the ratio of uptake over k2 were assessed using a two compartment model. The 17 segments were grouped into the basal (1-6), mid (7-12), apical (13-16) and apex (17). Results: The lowest % uptake was found in the apical segments at rest and Ado. This was found predominantly due to increased K2, which was significantly inversely correlated to % uptake at rest (r=-0.818, p<0.001) and Ado (r=-547 p=0.016). The ratio of uptake over k2 was significantly different in apical regions to mid and basal regions on both rest and Ado (Figure). Conclusions: False positive apical defect are possible in static cardiac PET imaging with 13N-ammonia. Our data indicate that often these defects are due to increased washout rather than decreased flow as evidenced by normal MBF value, suggesting that a careful interpretation of 13N-ammonia PET/CT myocardial perfusion scan needs to take into account the parameters obtained from quantitative analysis.

Result in this study

Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Adachi, I. Articles by Kaufmann, P. PubMed Articles by Adachi, I. Articles by Kaufmann, P.