Background: Scintimammography is an imaging tool for the diagnosis and management of primary breast tumors. There remains a significant knowledge gap regarding the physiological fluctuations in the basal level of 99mTc-sestamibi uptake in normal mammary tissues with respect to the female reproductive cycle.
Purpose: To systematically characterize 99mTc-sestamibi uptake in normal mammary tissues in female Sprague Dawley (SD) rats in different estrous phases.
Material and Methods: The exact phase of the reproductive cycle was determined in 18 female SD rats. Each rat was sacrificed at 20 min after 99mTc-sestamibi injection (14.8 MBq/kg). The mammary glands were dissected, and the radioactivity uptake was measured by gamma counting.
Results: Tc-99m-sestamibi uptake oscillates by about twofold and reaches a maximum at the proestrous phase of the rat reproductive cycle.
Conclusion: Tc-99m-sestamibi uptake fluctuates significantly in normal mammary tissues in synchrony with the female reproductive cycle, and peaks in the proestrous phase in rats, which is equivalent to the early to mid-follicular phase in the human menstrual cycle. This finding will likely benefit the detection of breast lesions that may otherwise be obscured by fluctuating background signals in surrounding normal breast tissues.
