Pharmacokinetic model of myocardial (99m)Tc-sestamibi washout

Technetium-99m sestamibi ((99m)Tc-MIBI) scintigraphy has been reported to be a functional imaging tool for in vivo detection of mitochondrial dysfunction in myocardium and multidrug resistance-associated protein expression in tumors. The purpose of this study was to propose a clinically applicable pharmacokinetic model with metabolic equilibrium of (99m)Tc-MIBI and to evaluate the accuracy of the model.

For this study, eight healthy men received (99m)Tc-MIBI scintigraphy. The planar images were obtained at 0.25, 0.5, 1, 2, 3, 4, 5, and 6 h after (99m)Tc-MIBI injection. The measured time series (99m)Tc-MIBI counts were fitted to our model by nonlinear regression analysis. The predictive performance of the model was determined by comparing the residuals between measured and predicted values.

We obtained a good regression by fitting data from 0.25 to 6 h after (99m)Tc-MIBI injection, with excellent correlation between measured and predicted (99m)Tc-MIBI counts (R(2) = 0.9792) and a slope near unity. The 95% confidence interval of the mean prediction error included 0, which means that the prediction was not significantly biased. The precision of the prediction was also excellent.

Our model shows good predictive capacity, with favorable bias and accuracy. By comparing the predictive values of this model with measured values, mitochondrial (99m)Tc-MIBI washout can be quantified. (99m)Tc-MIBI washout rates are reported to be a promising method for evaluating cardiac function in patients with cardiac diseases and P-glycoprotein expression in tumor cells. Therefore, this quantification could be useful for mitochondrial functional imaging, especially in patients with cardiac diseases or tumors.