There are multiple definitions:

1. prolactin-releasing factor(English)

2. pulse repetition frequency(English)

   • see laser
   • ARF
   • Laser technique

3. pulmonary regurgitant fraction(English)

   • TOF
   • Congenital disorders
   • https://doi.org…JAHA.120.016308

4. platelet-rich fibrin(English)

   • autologous platelet concentrate used as supplement for bone substitute
   • AH, APL, BCP, DBBM, PL
   • Dentistry
   • https://doi.org…155/2014/367265

5. pelvic ring fracture(English)

   • CUD, LUTI, PUI
   • Injury, Skeleton and bone (formation)
   • https://doi.org…amc-2013-000025