Advanced two-dimensional and three-dimensional ultrasonic imaging of the prostate for detecting, evaluating, and monitoring cancer

Transrectal biopsies of the prostate are guided using B-mode ultrasound. Ab out 30% of initial biopsies in men suspected of having prostate cancer are positive. A slightly lower incidence of positive biopsies occurs in repeat examinations of men having negative initial biopsies. These rates of detect ion imply that the sensitivity of conventional ultrasound-guided procedures is between 40% and 50%. With about 330,000 new cases of prostate cancer de tected annually in the US, these figures suggest that more than 600,000 act ually positive glands are biopsied at least once, and that even with repeat biopsies, almost 300,000 cancers go undetected; i.e., produce false-negati ve results. The figures also suggest that well over 1,000,000 biopsy examin ations are performed annually, which indicates that the biopsies of about 4 00,000 men produce true-negative results and hence, in hindsight, were unne cessary. We have acquired ultrasonic and biopsy data from more than 250 pat ients. We have compared the classification efficacy of spectrum analysis of the radiofrequency (RF) echo signals (present, but not utilized, in conven tional ultrasound instruments) with B-mode imaging currently used for biops y guidance. Our latest comparison of spectrum-analysis results with B-mode image-interpretation data from 96 patients and 448 biopsies produced relati ve operating characteristic (ROC) curve areas of 0.75 for spectrum analysis and 0.58 for B-mode biopsy guidance; the gold standard for these compariso ns was the histology findings of the 448 biopsies. Our results indicate tha t biopsy guidance based on spectrum analysis can improve sensitivity and ca ncer detection by approximately 50%; i.e., increasing the number of cancers detected annually in the US to more than 450,000. Similarly, spectrum anal ysis potentially can aid in evaluating and monitoring detected cancers by h elping to assess the number, location, and volume of lesions and by providi ng a quantitative means of determining the nature and rate of change in les ion properties. Obvious applications are guiding therapy (brachytherapy, cr yotherapy, etc.), determining whether surgery is warranted, assisting in wa tchful waiting, titrating treatment, and assessing responses to neoadjuvant therapy. Spectral methods can be incorporated into clinically useful image s. Such images are digitally generated from RF signals by computing spectra at each pixel location. Pixel values in the resulting image may depict spe ctral parameters, tissue properties (such as scatterer sizes or concentrati ons), or on the basis of comparisons with database values, either most like ly tissue type or level of suspicion (LOS). Either two- or three-dimensiona l presentations can be generated; 3D renderings can be formed from sets of component 2D images. In 2D, any of these formats, but particularly the LOS format, could be used for more effective biopsy guidance; in two- or three- dimensions, they could be used for lesion assessment.