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Figure 5. Normal DEXA scans of the spine (top) and hip (bottom). Results are plotted in the right panels in relation to the normal age- and gender-matched reference curves.

negligible risk. Radiation doses from scans of the hip, forearm and total body are even lower.

Peripheral X-Ray Absorptiometry

Conventional DEXA (also known as central DEXA) is able to measure all skeletal structures, including those in the thicker body regions such as lumbar spine and hip. Unfortunately, conventional DEXA equipment is expensive and heavy. Therefore, a variety of compact, portable devices have been developed for measuring bone density in the extremities such as the forearm and calcaneus. Single photon absorptiometry (SPA) used a radionuclide source (iodine-125) but required periodic source replacements and immersion of the body part in water. Peripheral DEXA (pDEXA)

Figure 6. Broadbeam ultrasound attenuation (BUA) is defined as the slope of the relationship between sound frequency and loss in bone signal. Over the usual range of frequencies (0.2 to 0.6 MHz) higher frequencies are associated with greater signal loss (dB attenuation).

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