Avascular necrosis of femoral head （AVN） was induced unilaterally in 10 dogs byfrozen. Dynamic bone Anaging was performed before

and 1

3

5

7

12

19 and 33 daysafter operation. The perfusion index of femoral head （FPI） was calculated by thegraphical approach of time-activity curves and quantitation of data. Based onhistological examination

pathological lesions on 10 dogs could be classified into fourstages: edema

hemorrhage

liquidation

and granulation formation with focal fibrosis

etc. Decreased FPI index was found in all lesions of 10 dogs by dynamic boneimaging. Until 19 days after operation

the uptake was reduced compared to thenormal side

whereas after 33 days

its uptake was increased. Perfusion index wasconsidered to reveal the blood flow condition in femoral head. It can be used todetect the early stage of AVN and to understand the effects of various modes oftherapy.