RESUMEN
OBJECTIVE: Estimates of ultrasonic attenuation (the loss of energy as an ultrasonic wave propagates through tissue) have been used to evaluate the structure and function of tissues in health and disease. The purpose of this research was to develop a method to estimate ultrasonic cervical attenuation during human pregnancy using a clinical ultrasound system. METHODS: Forty women underwent a cervical scan once during pregnancy with the Zonare z.one clinical ultrasound system using a 4-9-MHz endovaginal transducer. This ultrasound system provides access to radiofrequency (RF) image data for processing and analysis. In addition, a scan of a tissue-mimicking phantom with a known attenuation coefficient was acquired and used as a reference. The same settings and transducer used in the clinical scan were used in the reference scan. Digital data of the beam-formed image were saved in Digital Imaging and Communications in Medicine (DICOM) format on a flash drive and converted to RF data on a personal computer using a Matlab program supplied by Zonare. Attenuation estimates were obtained using an algorithm that was independently validated using tissue-mimicking ultrasonic phantoms. RESULTS: RF data were acquired and analyzed to estimate attenuation of the human pregnant cervix. Regression analysis revealed that attenuation was: a predictor of the interval from ultrasound examination to delivery (beta = 0.43, P = 0.01); not a predictor of gestational age at time of examination (beta = - 0.23, P = 0.15); and not a predictor of cervical length (beta = 0.077, P = 0.65). CONCLUSIONS: Ultrasonic attenuation estimates have the potential to be an early and objective non-invasive method to detect interval between examination and delivery. We hypothesize that a larger sample size and a longitudinal study design will be needed to detect gestational age-associated changes in cervical attenuation.
Asunto(s)
Maduración Cervical , Cuello del Útero/diagnóstico por imagen , Inicio del Trabajo de Parto , Trabajo de Parto Prematuro/diagnóstico por imagen , Adulto , Femenino , Humanos , Interpretación de Imagen Asistida por Computador , Persona de Mediana Edad , Embarazo , Ultrasonografía , Adulto JovenRESUMEN
The use of acoustics to determine the pore properties of soils, such as porosity, permeability, and tortuosity, is well established. A theoretical surface impedance and complex bulk wavenumber was developed by K. Attenborough for porous media that incorporated the soil pore properties as parameters [J. Acoust. Soc. Am. 73, 785-799 (1983)]. Acoustic level difference measurements were used as a noninvasive means of finding the soil pore properties. Acoustic reflection measurements showed that the sound field over porous rough surfaces is modified by the surface impedance and by surface roughness. It is not possible to separate the signal modification due to impedance and the signal modification from roughness scattering in a forward scattering measurement. In order to accurately determine the soil pore properties, the roughness effects must be known independently from the surface impedance. A means of measuring roughness apart from impedance would allow the effects of roughness to be taken out of the level difference measurements. The underwater acoustics community has used acoustic backscatter for many years to examine surface roughness. The feasibility of adapting these acoustic backscatter techniques to outdoor porous soil surfaces is examined.