The uterus can demonstrate increased activity, particularly the endometrium. It can appear quite focal and intense during active menstruation. Whether this activity is simply circulating tracer that 'bleeds' into the uterine cavity or is increased uptake within the endometrium is not clearly understood. Activity has been reported within vaginal tampons of actively menstruating women suggesting that the tracer is within the menstrual blood. PET/CT should localize activity to the uterine cavity.

Possible limitations:
Misinterpretation of focal uterine activity as uterine or presacral malignancy, or pelvic lymph nodes involvement.

Preventive measures:

• Avoid scanning during menstruation
• Repeat scan 14 days later to confirm menstrual activity