A Phase Compensation Technique for B-Mode Echoencephalography
Whereas A-mode echoencephalography has been found diagnostically useful, B-mode displays for similar object volumes have not yet provided the additional information that might be expected from a two-dimensional presentation. Poor image quality results from a number of causes stemming from the presence of skull bone (White, 1967; 1968). Large differences in specific acoustic impedance between skull bone and soft tissue combined with irregularities of skull bone surfaces result in unfavorable reflections and reverberations of acoustic energy. Severe attenuation of ultrasound at diagnostically useful frequencies further reduces system sensitivity and target acquisition. Additionally, significant differences between acoustic velocities in bone and tissue result in beam degradation and registration errors in the B-mode image. With one possible exception (Somer, 1969), the nature and extent of these aberrations have thus far limited practical utilization of B-mode scanners in clinical examinations of head structure.
KeywordsAttenuation Propa Refraction Azimuth
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