Myocardial Uptake of Technetium-99m-Furifosmin (Q12) Versus Technetiiim-99m-Sestamibi (MIBI)

Myocardial uptake characteristics of three 99mTc-labeled tracers for myocardial perfusion imaging one hour after rest injection

OBJECTIVE

99mTc-tetrofosmin and 99mTc-sestamibi are approved tracers for myocardial perfusion studies. Recently, a 99mTc-MIBI preparation from a different manufacturer (99mTc-cardiospect-MIBI) has been introduced to the market. Therefore, the aim of this study was the evaluation of 99mTc-tetrofosmin as well as of two different 99mTc-labeled MIBI tracers with regard to differences in imaging quality under resting conditions.

METHODS

Sixty patients (mean age 63.8 years +/- 1.25) with known or suspected coronary artery disease but without evidence of rest-ischemia were included. Twenty patients in each group were examined by a two-day-rest-stress protocol using the three 99mTc-labeled tracers. Visual analysis of all images was performed by two experienced physicians blinded with regard to the applied tracer. Regions of interest (ROI) were defined over the heart, lung and whole body only in the rest imaging in order to calculate heart-to-lung, lung-to-whole body-, and heart-to-whole body-ratios.

RESULTS

The heart-to-lung ratio was statistically significant higher for 99mTc-cardiospect-MIBI as compared to 99mTc-sestamibi as well as to 99mTc-tetrofosmin. Furthermore, a significantly higher heart-to-lung ratio was found for 99mTc-sestamibi as compared to 99mTc-tetrofosmin. The heart-to-whole body-ratio and the lung-to-whole body-ratio were equivalent between all tracers. Visual analysis revealed only slight differences regarding image quality between all tracers.

CONCLUSIONS

ROI analysis surprisingly revealed a significant higher myocardial uptake and consequently a higher heart-to-lung ratio for 99mTc-cardiospect-MIBI. Whether this leads to a better visual image quality has to be evaluated in future studies with larger study populations as well as semiquantitative segmental analysis of the myocardial perfusion images.

Dobutamine Tc-99m furifosmin SPECT in detection of coronary artery disease: evaluation of same day, rest-stress protocol

The purpose of this study was to evaluate the feasibility and diagnostic accuracy of same day rest-stress myocardial perfusion SPECT (MP SPECT) protocol by using technetium-99m (Tc-99m) furifosmin in conjunction with dobutamine stress test in subjects in whom coronary artery disease (CAD) had been proven or excluded at coronary angiography (CA). The study group consisted of 25 patients (8 female and 17 male with a mean age of 53.04 +/- 8.56 yrs) unable to perform treadmill exercise or unsuitable for pharmacologic vasodilator stress testing. Ten mCi (370 MBq) of Tc-99m furifosmin was injected intravenously at rest. Sixty min after injection, planar and SPECT images were acquired. One hour later all patients underwent dobutamine stress test. At the peak stress, 20 mCi (740 MBq) of Tc-99m furifosmin was injected. Sixty min after stress dose injection, planar and SPECT images were acquired. Rest-stress planar and SPECT data were evaluated by using visual and quantitative analysis. Heart to adjacent organ (Heart/Lung; H/Lu and Heart/Liver; H/Li) activity ratios were calculated from anterior planar images by using regions of interest (ROI). SPECT data were interpreted by using 20 segment-5 point scoring system from short axis and vertical long axis slices. The results of rest-dobutamine stress Tc-99m furifosmin MP SPECT were compared with CA results. There were statistically significant differences between H/Lu and H/Li ratios at rest and stress conditions. Heart/adjacent organ activity ratios were similar and significant statistical difference could not be found between CA positive and CA normal patients. Sensitivity, specificity and accuracy for Tc-99m furifosmin SPECT study were calculated as 90%, 80% and 84% for left anterior descending (LAD), 87%, 94% and 92% for left circumflex (LCx) and 67%, 86% and 80% for right coronary artery (RCA), respectively. Overall sensitivity, specificity and accuracy were calculated as 83%, 87% and 85%, respectively. According to the results obtained in this study, it may be concluded that same day rest-dobutamine stress Tc-99m furifosmin SPECT protocol is a feasible and accurate technique in the evaluation of CAD, especially in patients unable to perform treadmill exercise or unsuitable for pharmacologic vasodilator stress testing.

201Tl, 99mTc-MIBI, 99mTc-tetrofosmin and 99mTc-furifosmin: relative retention and clearance kinetics in retrogradely perfused guinea pig hearts

Myocellular kinetics of 201Tl, 99mTc-MIBI, 99mTc-tetrofosmin and 99mTc-furifosmin were investigated using retrogradely-perfused guinea-pig hearts. Relative retention decreased in the order 99mTc-MIBI ==> 99mTc-tetrofosmin ==> 99mTc-furifosmin. 201Tl and 99mTc-MIBI exhibited bi- (t1,t2), 99mTc-tetrofosmin and 99mTc-furifosmin triexponential (t1,t2,t3) time-activity-curves. Latest-phase elimination-half-life increased from 201Tl (t2) ==> 99mTc-MIBI (t2) ==> 99mTc-tetrofosmin (t3) ==> 99mTc-furifosmin (t3), showing a significant increase in deteriorating myocardium for all tracers but 99mTc-furifosmin. Delayed elimination in deteriorating myocardium explains at least partly the redistribution phenomenon of 201Tl, and suggests a similar phenomenon for 99mTc-MIBI and 99mTc-tetrofosmin.