Detection of Clinically Significant Prostate Cancer Using Subharmonic Imaging

Abstract

This study assessed the prostate cancer (PCa) detection rates of contrast-enhanced, transrectal subharmonic ultrasound imaging (SHI). This IRB-approved study enrolled 55 subjects. The initial 5 subjects were studied for SHI optimization, while the remaining 50 were evaluated with conventional grayscale, continuous color and power Doppler as well as contrast-enhanced continuous SHI, color and power Doppler and SHI combined with maximum flash replenishment. A maximum of 6 directed biopsy cores were obtained from sites of greatest asymmetrical enhancement, followed by 12 spatially distributed systematic cores. SHI time-intensity parameters, including time to peak intensity, peak intensity and estimated perfusion were also evaluated for each biopsy core. Receiver operating characteristic (ROC) curve analysis and conditional logistic regression were employed to assess the benefit of each modality and the quantitative SHI parameters. Cancer was detected in 22 of 50 subjects. Among subjects with clinically significant PCa (n=11), targeted cores were more likely to be positive (odds ratio 1.39, p=0.02). The majority of patients detected by SHI demonstrated significant PCa (5/8) and SHI remained an independent marker of malignancy in a multivariate logistic regression model (p=0.027). ROC analysis of imaging findings compared to biopsy results yielded diagnostic accuracies ranging from 0.59 to 0.80 for all imaging modalities with the highest being for quantitative subharmonic perfusion estimates. In conclusion, this first-in-humans study provides a preliminary estimate of the diagnostic accuracy of SHI for detection of clinically significant PCa (up to 80%).