Typing of prostate tissue by ultrasonic spectrum analysis

Prostate cancer is the highest-incidence cancer and second-leading cancer killer of men in the U.S. Diagnosis now relies virtually exclusively on core-needle biopsy, guided by transrectal ultrasound (TRUS). Because of the limitations of TRUS in detecting suspicious regions, biopsy often fails to sample cancer that is present or to determine that extracapsular cancer exists, which results in false-negative biopsies or inappropriate prostatectomies. Therefore, the authors conducted this study to investigate the use of spectrum analysis of radio frequency (RF) echo signals as a possible means of reducing the number of false-negative biopsies and inappropriate prostatectomies. This method utilizes databases of parameters derived from normalized power spectra of RF echo signals and histologically proven tissue types to determine ranges of parameter values associated with tissue types of interest. Typing an unknown tissue is performed by comparing the parameter values of the unknown to the value ranges of specific tissue types in the database. The authors' results provide encouraging preliminary discriminant-function distributions that suggest an excellent potential for differentiating cancerous from noncancerous prostate tissue far superior in terms of sensitivity and specificity than means now used to determine whether biopsy is required. In addition, the authors developed images using color to indicate the most likely tissue type throughout the tissue cross section as determined by comparisons with database parameter values. These images showed excellent correlation with histology.