A main drawback of 20-25 MHz ultrasound units for skin imaging is their limited resolution. We used a transducer with a center frequency of 95 MHz and a resolution of 8.5 microm axially and 27 microm laterally - an almost 10-fold increase compared with 20 MHz. By means of a new scanning technology we reached a depth of field of 3.2 mm. We examined normal palmar skin, normal glabrous skin on the abdomen, the upper back, the calf and the dorsal forearm, and 35 lesions of psoriasis vulgaris. From 11 psoriatic plaques biopsies were taken for correlation with the sonograms. In normal palmar skin, the horny layer is represented as an echopoor band below the skin entry echo, traversed by echorich coils, which correspond to eccrine sweat gland ducts. The thickness of this band significantly increases after occlusive application of petrolatum. Its lower border is defined by an echorich line, representing the stratum corneum/stratum Malpighii-interface. Underneath, a second echopoor band is visible, which corresponds to the viable epidermis plus the papillary dermis, bordered by the scattered echo reflexes of the reticular dermis. This band is also visible in glabrous skin; however, the stratum corneum cannot be detected. In psoriatic lesions, the thickened horny layer appears echorich; after application of petrolatum, its echodensity decreases. Below, the acanthotic epidermis plus the dermis with the inflammatory infiltrate are represented as an echopoor band. There is an excellent correlation between the sonometric thickness of this band and the histometric thickness of the acanthosis plus the infiltrated dermis. Our results show that 100 MHz sonography is a valuable tool for in vivo examination of the upper skin layers.

The density of follicles on various regions of the human face has received scant attention. We used cyanoacrylate follicular biopsies to determine the number of follicles on the forehead, cheek, chin and nose of 12 healthy adult white women. Sebum output was assessed on the same regions by means of Sebutape. The density of follicles and sebum output followed a centrolateral decreasing gradient. There was no correlation between these two parameters. These regional patterns are important for studies of the pathogenesis of common disorders of the face and their response to treatment.

In order to assess the value of 20-MHz sonography in the pre-operative diagnosis of malignant melanomas, 54 melanomas were examined. The pre-operative ultrasound scans were compared with corresponding histological sections from the excised tumours. A computer-aided measurement of the tumour thickness (sonometry) and the internal echo density (densitometry) was performed in the ultrasound scans. The melanomas appeared as largely echolucent zones. There was a significant correlation between the tumour thickness measured in the ultrasound scan and those measured in the histological sections (r = 0.938, p < 0.001). As a rule the tumour thickness determined by sonometry were greater than the histometrically determined values. Subtumoral inflammatory infiltrate and other hypo-echoic structures in the region of the tumour are possible causes of the discrepancies. Some of those hypo-echoic structures can be identified and disregarded in B scan measurement. Even if a definite differential diagnosis is not possible on the basis of the ultrasound scan alone, 20-MHz sonography provides additional information which can be of use in surgical planning.