US characteristics of frozen prostate.

Cryosurgery has previously been used successfully to treat prostatic carcinoma. Inability to monitor the freezing led to local complications that limited the use of this modality. In this animal study, monitoring of the freezing process was accomplished with real-time ultrasound. The margin of the frozen tissue appeared as a hyperechoic rim with posterior acoustic shadowing. The thawed cryolesions showed markedly decreased echogenicity compared with normal unfrozen prostate. These characteristic changes should allow safer and more efficacious application of prostatic cryosurgery.