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Biomedical subjects

F J Fry

Publications and source records attributed to F J Fry.

At least 37 records · Page 2Linked to original sources
PubMed1981

Transkull focal lesions in cat brain produced by ultrasound.

Focused ultrasound has been used for focal modifications of brain tissue and in preliminary studies of the application of ultrasonic techniques for tissue modification in human stereotaxic neurosurgery; however, the technique has been seriously compromised by the necessity of removal of intervening skull. Such removal was necessary to avoid distortion and extremely large attenuation of the ultrasonic beam which resulted from passage through bone. Recent studies have shown that under proper conditions focal beams of ultrasound can be transmitted with tolerable and attenuation through skull, suggesting the possibility of transkull lesion production in brain. This report describes the acoustical parameters and histological features of focal brain lesions produced in 10 craniectomized cats with intense focal ultrasonic beams which first had passed through a formalin-fixed human skull overlay. The histological appearance of these lesions produced to date is similar to that produced previously without intervening skull.

Animals↗
PubMed1978

Acoustical properties of the human skull.

The acoustical properties insertion loss, reflection loss, and sound speed were measured on a series of fresh and subsequently formalin immersed human skulls. Measurements were made in the frequency range from 0.25 to 6 MHz. Most studies were restricted to an upper frequency limit of 2.2 MHz. An axisymmetric focused beam configuration was used as the sound source for the measurements and the receivers were small disk-type (3-mm-diam) piezoelectric ceramics. The geometric and temporal character of the focused beam was studied as a consequence of passage through the skull sections. Some skulls were sectioned so that their individual layer components could be studied. A simple three-layer analytical model seems to explain the major aspects of insertion and reflection loss. The dominant feature in determining human adult skull losses is the middle layer (diploe) of cancellous bone. This study corroborates previous work on insertion loss as a function of frequency for composite skull. The study provides new quantitative information on the acoustic scattering properties of diploe, sound velocity, and dispersion in composite skull and its components, attenuation coefficients in skull components and sound-beam distortion and shifts after transmission through composite skull. We conclude that with selection of appropriate frequencies (0.5-1.0 MHz) and beam configuration it will be possible to perform clinically significant transkull diagnostic imaging and interrogation in the adult human brain.

Acoustics↗