What is the isotope commonly used in Dual Photon Absorptiometry (DPA)?

• A. Calcium-40
• B. Gadolinium-153
• C. Strontium-89
• D. Technetium-99

Answer: (B)

In Dual Photon Absorptiometry (DPA), Gadolinium-153 is the isotope commonly used for bone densitometry. This isotope emits gamma radiation with two specific energy levels that are ideal for differentiating between the bone and soft tissue. The energy levels emitted by Gadolinium-153 allow for accurate measurement of bone mineral density (BMD), making it particularly useful in clinical settings to assess conditions such as osteoporosis.

The choice of Gadolinium-153 is due to its suitable half-life and the energy of the photons it emits, which fit well within the parameters required for bone density measurements. This enables high-quality imaging and precise calculations of bone density necessary for diagnosing and monitoring bone health.

In contrast, the other isotopes listed do not have the same beneficial characteristics for use in DPA. For instance, Calcium-40 is a naturally occurring isotope but does not emit gamma radiation that is utilized in bone densitometry for these measurements. Strontium-89, primarily used in radiotherapy for bone pain, does not cater to the specific energy requirements of DPA. Technetium-99 is widely used in various radiological procedures and imaging, yet it is not suited for bone densitometry as it does not provide the