Effective depth of spermatogonia in man I. Measurement of scrotal thickness

Dosimetry for sperm cells irradiated by high-energy betas requires precise knowledge of the effective depth of the spermatogonia, and hence the thickness of overlying tissues (scrotum plus tunics), because beta dose rate changes very rapidly with depth. Measurements were made on 25 volunteers and surgical patients by mechanical caliper during surgery (2), by ultrasound (14), or by both (9), all at 20 degrees C air temperature. The tunica albuginea (TA) measured 0.1 mm. The surgical results (TA excluded) were 2.0 mm, sigma = 0.3 mm (n = 11). The ultrasound results (TA included) were 2.2 mm, sigma = 0.6 mm (n = 23). There was no correlation of scrotal thickness with age (24-83 years) and only a very weak correlation (r = 0.3) with body mass. There was no decrease in scrotal thickness (at 20 degrees C) with further warming but there was an increase (to 3.3 mm from 2.3 mm) with chilling before measurement. Ultrasound is shown to be valid for such measurements.