CPT® Code 77079

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Computed tomography, bone mineral density study, 1 or more sites; appendicular skeleton (peripheral) (eg, radius, wrist, heel)

The CPT® Code 77079 refers to a computed tomography (CT) procedure specifically designed for conducting a bone mineral density study at one or more sites within the appendicular skeleton, which includes peripheral areas such as the radius, wrist, and heel. This procedure is also known as quantitative computed tomography (QCT) densitometry. The primary purpose of measuring bone mass or bone mineral density (BMD) is to assist in diagnosing bone diseases, evaluating the progression of these diseases, and monitoring treatment outcomes, particularly in patients with osteoporosis. Osteoporosis is a condition that significantly increases the risk of fractures due to decreased bone density. The CT technology utilized in this procedure employs multiple narrow x-ray beams that rotate around a single axis, capturing a series of two-dimensional images from various angles. These images are then digitally reconstructed by a computer to create a three-dimensional representation of the bone structure, allowing for the production of thin, cross-sectional images or slices. QCT is recognized for its enhanced accuracy, being 2-3 times more precise than traditional bone dual-energy X-ray absorptiometry (DXA) scanning. This increased accuracy is attributed to the three-dimensional nature of QCT, which enables a more accurate calculation of bone density by measuring mass relative to volume. In contrast, DXA measures BMD based on the attenuation of x-rays by the bone divided by the area of the scanned site, lacking a depth component in its calculations. For studies involving the axial skeleton, such as the pelvis, hips, or spine, the appropriate code to use is 77078, while 77079 is specifically designated for the appendicular or peripheral skeleton.