1. Physiology of the tracer
1. ¹⁸F is labeled to estradiol which is an estrogen receptor and only goes to breast cancer that has estrogen sites
2. Uptake will also occur in heterogeneous site of breast cancer as long as it includes ER positive sites
2. Role of FES
   1. Adjunct to biopsy (FDA approved)
   2. Assess there ER-positive burden
   3. Clarify FDG findings
   4. Determine ER heterogeneity
   5. FDG - recurrent and/or metastatic breast cancer
   
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   6. Comparison of the molecule structures
3. Acquisition
   1. Prep
      1. Do not take ER blocking drugs - Taxoxifen or Fulvestrant
      2. Establish baseline before patient is placed on ER therapy
      3. Patient should be well hydrated
   2. Dosing
      1. Administer a 3 to 6 mCi dose over a 1 to 2 minute period followed by a 10 mL flush
      2. Imaging should start between 20 to 80 minutes post dose
   3. Acquisition
      1. Place arms above the head
      2. Image mid-thigh to the top of the skull
      3. Acquisition time per bed 3 to 4 minutes pending the type of crystal
4. Concerns
   1. Heterogeneous tumors may reduce FES uptake since this tracer only looks for ER sites on tumor surface
   2. There are other types of ER positive tumors - uterus and ovaries

5. Normal vs abnormal uptake

18F-Fluoroestradiol Whole-Body Imaging by Grabher, B. JNMT (2023)