High frequency ultrasonic imaging of skin: experimental results.
Experimental results are presented demonstrating the application of pulse echo ultrasound to imaging the skin. A laboratory prototype B-mode mechanical scanner was employed to obtain images of human skin, both in vitro and in vivo, using broadband pulsed ultrasound at 25 MHz. Images were formed by processing digitized A-mode waveforms and displaying the resulting two-dimensional cross sections using a digital imaging system. Images obtained by rectifying the A-modes are compared to those derived using a software-based cross-correlation technique. Scans of test targets demonstrate that an axial resolution of 100 m can be achieved at 25 MHz when the digital correlation method is employed. Lateral resolution is limited by the 0.25 mm half-power focal beamwidth of the transducer. Seventeen in vitro ultrasonic scans of human skin were compared to frozen section histology. Average skin depth was well correlated between the two techniques ( = 0.99, p less than 0.001). Application of cross-correlated processing to 25 MHz in vivo images produced good delineation of epidermis, papillary, and reticular dermis. Conversion to a 50 MHz transducer did not delineate skin layers as well as the 25 MHz transducer due to inherent difficulties with transducer reverberations.
D000005:Abdomen; D000328:Adult; D000368:Aged; D002280:Basal Cell Carcinoma / Q000175:diagnosis; D005143:Eyelids; D005260:Female; D005542:Forearm; D006801:Humans; D066298:In Vitro Techniques; D007223:Infant; D008297:Male; D008875:Middle Aged; D012594:Scleroderma, Localized / Q000175:diagnosis; D012867:Skin / Q000033:anatomy & histology*; D012878:Skin Neoplasms / Q000175:diagnosis; D012885:Skinfold Thickness; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*