What are the two main techniques used in modern DXA measurements?

• A. Transmission and emission
• B. Fan and pinhole collimation
• C. Dual-energy and single-energy
• D. Continuous and pulsated

Answer: (C)

The correct choice highlights the fundamental principles behind how dual-energy X-ray absorptiometry (DXA) works for measuring bone density. DXA uses two different energy levels of X-rays to differentiate between bone and soft tissue, allowing for a precise assessment of bone mineral density.

With dual-energy, the system emits X-rays at two energy levels, which helps in enhancing the measurement accuracy by compensating for variables such as the presence of soft tissue, variations in body composition, and individual patient characteristics. This technique is essential for obtaining reliable data on bone health, aiding in the diagnosis of conditions like osteoporosis.

In contrast, other techniques listed, such as single-energy, do not provide the same level of differentiation between soft tissue and bone, which can lead to less accurate results. Each of the other choices references different methods or technologies that are not standard in the practice of DXA measurements specifically for bone density assessment. The dual-energy approach is thus essential to modern practice in bone densitometry, making it the correct answer.