Q: Dr. Bernstein, I was reading about a densitometer on your website. What is it and what is it actually used for? — Z.A., Westchester, NY

A: The hair densitometer was introduced to hair restoration surgeons by Dr. Rassman in 1993. It is a small, portable, instrument that has a magnifying lens and an opening of 10mm2.

To use it, the doctor clips the hair short (~ 1-mm) and the instrument is then placed on the scalp. The doctor counts the total number of hairs in the field, looks at the number of hairs per follicular unit and assesses the diameter of the hair, looking in particular for abnormal levels of miniaturization (decreased hair shaft diameter caused by the effects of DHT).

The densitometer can increase the accuracy of the diagnosis of genetic hair loss by picking up early miniaturization.

It can also better assess a person’s donor hair supply, thus helping to determine which patients are candidates for a hair transplant.

Densitometry has helped us define the conditions of diffuse patterned and unpatterned hair loss (DPA and DUPA) and help to refine the diagnosis of hair loss in women.