RESUMEN

OBJECTIVE: To assess the prostate cancer (CaP) detection rates of contrast-enhanced, transrectal subharmonic ultrasound imaging (SHI). MATERIALS AND METHODS: This IRB-approved study enrolled 55 subjects. The initial 5 subjects were studied for SHI optimization, while the remaining 50 were evaluated with contrast-enhanced sonography using continuous SHI, color, and power Doppler as well as conventional grayscale, continuous 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 spatially distributed cores in a double sextant distribution. Subharmonic time-intensity parameters, including time to peak intensity, peak intensity, and estimated perfusion were also evaluated for each directed biopsy core. Receiver operating characteristic curve analysis and conditional logistic regression were employed to assess the benefit of each modality and the quantitative SHI parameters. RESULTS: Cancer was detected in 22 of 50 subjects. Among subjects with clinically significant CaP (n = 11), targeted cores were more likely to be positive (odds ratio 1.39, P = .02). The majority of patients detected by SHI demonstrated significant CaP (5/8); SHI remained an independent marker of malignancy in a multivariate logistic regression model (P = .027). Receiver operating characteristic curve 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. CONCLUSION: This first-in-humans study provides a preliminary estimate of the diagnostic accuracy of SHI for detection of clinically significant CaP (up to 80%).

Asunto(s)

Próstata/diagnóstico por imagen , Neoplasias de la Próstata/diagnóstico , Ultrasonografía Doppler/métodos , Anciano , Biopsia con Aguja Gruesa/estadística & datos numéricos , Medios de Contraste/administración & dosificación , Humanos , Masculino , Microburbujas , Persona de Mediana Edad , Estudios Prospectivos , Próstata/patología , Neoplasias de la Próstata/epidemiología , Neoplasias de la Próstata/patología , Curva ROC , Ultrasonografía Doppler/estadística & datos numéricos

RESUMEN

Deals with a method of detecting and estimating the scatterer spacing between the regularly spaced resolvable coherent scatterers in tissue. Scatterer spacing has been successfully used in classifying tissue structure, in differentiating between normal and cirrhotic liver, and in detecting diffuse liver disease. This paper presents a WOLD decomposition of the radio frequency (RF) field into its diffused and coherent components from which maximum likelihood estimates (MLE) or minimum mean square error (MMSE) estimates of the scattering spacing are easily computed. The MLE are efficient and for relatively long record are unbiased. They result in accurate estimates in low signal-to-noise (SNR) ratios. Unfortunately, they require nonlinear minimization and knowledge of the probability density associated with the RF backscatter echo. The MMSE estimates, on the other hand, are computationally simple, yield unique closed form solutions, do not require a-priori knowledge of the probability distribution function of the backscatter echo, and result in accurate estimates in low SNR ratios. This paper also presents an unbiased decision rule to detect whether or not an RF echo exhibits any specular scattering relative to the wavelength of the interrogating ultrasonic pulse. The approach has been tried on simulations as well as on in-vivo scans of liver data, and appears to perform well.