Measurement of the extraction efficiency and distribution volume for Gd‐DTPA in normal and diseased canine myocardium

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Abstract
We have previously shown that the myocardial Gd‐DTPA concentration ([Gd‐DTPA]t(t)) after a bolus injection of Gd‐DTPA can be predicted by the Modified Kety Equation (MKE). If [Gd‐DTPA]t(t) can be determined by MRI and the data fit to the MICE, then the distribution volume (λ) of Gd‐DTPA and the myocardial flow (F) times the extraction efficiency (E), i.e., the FE product, can be determined. Therefore F can only be quantified if E is known. We measured the global Ein vivo in normal canine myocardium, and measured E and λ, in vitro, locally in normal, acute ischemic (n = 5; coronary artery occlusion < 4 h), infarcted (n = 4; coronary artery occlusion, 6 days) and reperfused (n = 4; coronary artery occlusion 2 h, and reperfusion 2 h and 6 days) myocardium. Results indicate that E differs with F and with individuals and consequently, F cannot be quantified using the MKE unless the local E is also determined in vivo.