Background and Purpose: To assess the influence of the skull on blood flow signals detected by transcranial Doppler, we measured bone density in the skull using dual energy X-ray absorptimetry. Methods: Bone mineral density (BMD) was studied in 219 normal volunteers (mean age±SD 53.5±17.9 years, 80 men, 139 women) . In 37 of the subjects (mean age ±SD 56.4±15.8 years, 17 men, 20 women), blood flow signals were also measured using a 2-MHz range-gated pulsed-wave Doppler. Results: BMD in women was lower than that in men over 60 years of age (p<0.05) . The rate of unsuccessfully recorded flow signals increased with age, especially in women (14 of 17 women aged 60 years or over) . BMD in the unsuccessful recording group (1.482 ± 0.123 g/cm2, mean ± SD) was significantly lower than that in the successful recording group (1.835±0.058 g/cm2) (p<0.05) . Conclusion: The rate of unsuccessfully recorded blood flow signals increased with advancing age, especially in women, and with lower BMD in the skull.
