Utility of 99mTc-sestamibi Heart/Liver uptake ratio in Screening for Non-alcoholic Fatty Liver Disease during Myocardial Perfusion Imaging

Introduction: Non-alcoholic fatty liver disease (NAFLD) is the most common chronic hepatic disease worldwide with functional impairment of the mitochondria occurring from early stages. Technetium-99m methoxy-isobutyl-isonitrile(99mTc-MIBI) is a lipophilic agent trapped in the mitochondria. This study aims to evaluate the utility of 99mTc-MIBI heart/liver uptake ratio in screening for NAFLD during myocardial perfusion imaging (MPI).

Methods: 70 eligible patients underwent a two-day rest/stress 99mTc-MIBI scan with a 2-minute planar image acquired in rest phase, at 30, 60 and 120 minutes post radiotracer administration. Heart/liver uptake ratio was calculated by placing identical regions of interest on the heart and liver dome. All patients underwent liver ultrasound and were allocated into groups A, having NAFLD, and B, healthy individuals without NAFLD.

The Pearson test was used for the evaluation of any correlation between parameters. P-value < 0.05 was considered significant. Random forest classifier with 10-fold cross validation was used to develop a model based on clinical and scintigraphy findings to predict NAFLD patients. Three strategies were implemented. All available paraclinical, demographic (age, sex, BMI) and scintigraphy (0.5, 1, and 2hr) data were included in the first strategy. The second strategy compromised routine lipid profile (TG, Cholesterol), demographic (age, sex, BMI) and scintigraphy (0.5, 1, and 2hr) data. The third strategy only accounted for demographic (age, sex, BMI) and scintigraphy (0.5, 1, and 2hr) data to predict NAFLD. Also, we repeated the third strategy by using only one time point scintigraphy findings. i.e. age, sex, BMI and 1hr measurement. Area under the receiver operating characteristic (ROC) Curve was selected as the assessment criterion.

Results: Mean count per pixel heart/liver ratios gradually increased over time in either groups; nonetheless the values were significantly higher in group A, regardless of acquisition timing; with the P-value equal to 0.007, 0.014 and 0.010 at 30, 60 and 120 minutes, respectively. the classifier results for the three strategies.

Random forest classifier results indicated that the area under the ROC curve (AUROC) for the first, second, and third strategies were 0.97, 0.94, and 0.84 respectively. Repeating the third strategy by including single time point scintigraphy data at 1 hr. resulted in AUROC of 0.85, comparable to the accuracy of multiple time point measurement.

Conclusions: With regard to the independent risk NAFLD poses for CAD as well as the significant correlation both have with metabolic syndrome; NAFLD may be more prevalent in candidates for MPI scan. 99mTc-sestamibi Heart/Liver uptake ratio during rest phase MPI scan may be implemented as a feasible screening tool for NAFLD with an acceptable accuracy, comparable to several other non-invasive US or laboratory-based screening methods. As a secondary finding of MPI scan, it has the prominent advantage of having no additional cost, radiation burden or adverse effect.