Ultrasound method and apparatus for evaluating, in vivo, bone conditions

Abstract

A system for analyzing bone conditions, particularly (but not solely) for diagnosing osteoporosis and periodontal bone disease in humans. An ultrasonic signal (generally a pulse) having at least two components of distinguishable waveshape or frequency content in a range from about 100 kHz to about 3 MHz is launched transdermally into the patient, through a bony member such as the patella, and received at the other side. The transmission through the bony member and surrounding soft tissue varies in both amplitude and phase as a function of frequency, and the velocity of transmission varies between the bony member and the soft tissue. A variety of techniques are employed for analyzing the transmission of the ultrasonic signal to assess bone condition. These include at least: comparing the transit times through the bony member of energy in a first frequency range and energy in a second frequency; evaluating the transfer function through the bony member (i.e., gain and/or phase) of the portion of the signal travelling through the bony member; evaluating a gain function of the power spectrum of the portion of the signal transmitted through the bone, including the evaluation of the area under such gain function and/or the magnitude and location of its peak amplitude. The velocity of ultrasound energy through the bony member also may be deduced by determining the duration of travel of the ultrasound signal through the bony member and soft tissue and adjusting such composite velocity by a soft tissue normalization factor. Such information is then compared to a data base of prior measurements for the same patient and/or for the population at large, to determine a probability that the patient's bone condition is abnormal.