Biomedical subjects

P D Freiburger

Publications and source records attributed to P D Freiburger.

4 recordsLinked to original sources

PubMed1992

Two dimensional ultrasonic beam distortion in the breast: in vivo measurements and effects.

Two dimensional arrival time data was obtained for the propagation of ultrasound across the breasts of 7 female volunteers. These profiles were extracted through the use of cross-correlation measurements and a simulated annealing process that maintained phase closure while aligning the data. The phase aberration measured in two dimensions had a larger magnitude than previously reported phase aberration measured in one dimension in the breast. A point spread function generation computer program was used to demonstrate the system response degrading effects of the measured phase aberration and the usefulness of current one dimensional phase aberration correction techniques. The results indicate that two dimensional correction algorithms are necessary to restore the system performance losses due to phase aberration.

Female↗

PubMed1991

The impact of acoustic velocity variations on target detectability in ultrasonic images of the breast.

Experimentally obtained ultrasonic phase aberration profiles in the breast were used to investigate the impact of acoustic velocity variations on images of simulated breast lesions. The imaging properties of several phased-array transducers with varying frequencies and geometries were studied as phase error profiles of increasing magnitude were introduced. The targets studied were anechoic lesions of various sizes. The results indicate that phase aberrations significantly degrade the contrast of ultrasonic breast images, especially for high-resolution scanning systems.

Acoustics↗

PubMed1991

In vivo measurements of ultrasonic beam distortion in the breast.

The phase aberrations encountered by ultrasonic pulses propagating through breast tissue in twenty-two female volunteers were measured. The experiments were designed to assess the impact of these aberrations on clinical ultrasonic image quality for a variety of transducer and imaging geometries. The phase aberration profiles of a given patient were correlated with the amount of parenchymal tissue determined from that patient's mammogram. These data are useful in assessing the image quality achievable with conventional ultrasonic imaging systems, and the potential application of adaptive ultrasonic imaging systems. The results indicate that phase aberrations significantly degrade breast image quality for typical transducer frequencies and sizes.

Breast Neoplasms↗

PubMed1990

A real-time adaptive ultrasonic imaging system.

The performance of an experimental, adaptive, phased array imaging system in improving the quality of abdominal organ images in healthy volunteers was assessed. Trials were conducted under usual clinical imaging conditions and when phase aberrators of known shape and magnitude were introduced into the imaging system. The system, which uses local target brightness as a quality factor, was able to improve clinical image quality when aberrators introduced externally were present and had a negligible effect on image quality when they were not. On several of the volunteers, the phase aberrations were measured directly across the abdomen. The implications of these results for the future clinical application of adaptive imaging systems and the future system modifications are reported.

Adult↗