Quantitative Ultrasonography (QUS)

QUS, unlike diagnostic ultrasonography, uses a transmitting and receiving transducer. Frequencies are higher than used for diagnostic ultrasonography. The measurement reflects structure and mineral content by determining ultrasound attenuation and speed of sound. The measurement is reported as a T-score.

The most common site of measuring bone is the calcaneus followed by the distal radius. Many other bones have been assessed without benefit of reference databases. This technology can be used to assess fracture risk but cannot be used to observe patients for density changes or treatment efficacy.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging is used clinically to identify occult fractures that are not visualized on plain radiographs. MRI demonstrates bone marrow edema and the fracture line whether it may be partial or complete. MRI uses different sequences that result in identifiable signal characteristics dependent on radiofrequency and length of time the radiofrequency is on and off. Magnetic gradients allow the computer to reconstruct anatomy based on small differences in precession frequency of protons in the gradients. The energy that changes the position and frequency of the proton precession in the gradients applied is released by the protons returning to their normal alignment in the main magnetic field. The energy is detected by a receiving antenna, and the signal is reconstructed into an image.

Clinically, MRI is used to differentiate between osteoporotic and pathologic vertebral fractures and identify occult osteoporotic fractures of other bones, most commonly nondisplaced fractures of the hip.

MRI research, using signal intensity and spatial density, can be used to determine trabecular volume, density, and connectivity. Structural models can be reconstructed for three-dimensional rendering of trabeculae. Unfortunately, the calculation of these volumes and densities with structural models have yet to be useful for fracture prediction in individuals even though they relate to bone strength.