The myocardial perfusion agent, 99mTc-sestamibi (MIBI), offers the potential to combine renal and myocardial imaging because of high initial renal extraction and significant renal clearance.
Methods: Dynamic renal imaging was performed during rest MIBI injections in 3 normal subjects (NS) and 91 patients referred for cardiac assessment. Ten served as normal controls, and 81 were hypertensive. Renal activity of MIBI during the first transit, uptake and excretory phases of the study was quantified. These data were compared with the normal kinetics of 99mTc-diethylenetriaminepentaacetic acid (DTPA) in concurrent studies.
Results: With MIBI, clear definition of the kidneys was possible on all phases in most studies; occasionally, overlap with liver or spleen provided a minor problem. Renal MIBI activity reached levels 70% greater than DTPA during first transit and remained higher throughout the study; renal/background activity ratios were also higher on the MIBI study (p < 0.001). During the excretory phase with MIBI, hepatic and splenic activity did not decline, and gut activity increased. In NS, 40% of the total activity was excreted in the urine in 1 hr; urinary MIBI clearances approximated creatinine clearance. Asymmetry in initial renal uptake was seen in 14 of 81 hypertensive patients (17%); renal cysts and aortic dilatation could also be identified.
Conclusion: These data suggest that ancillary renography during rest injection of MIBI could be a useful addition to the cardiovascular assessment of selected patients.