Evaluation of background correction methods.

After intravenous injection of radioiodinated heptadecanoic acid a high background activity disturbs direct determination of myocardial elimination rates. Several correction procedures for background activity are used. After intracoronary administration a much lower background activity is found. To validate the background subtraction procedures we compared in this study the results of the correction procedures with the results after intracoronary injection of the fatty acid, in which no background subtraction was performed. In ten patients myocardial elimination rates after intracoronary and after intravenous injection were determined. A modified bi-exponential curve fitting procedure, assuming a constant background activity, showed the best results compared with the intracoronary study.