What radioisotope is utilized in Single Photon Absorptiometry?

• A. Gadolinium-153
• B. Gold-198
• C. Iodine-125
• D. Yttrium-90

Answer: (C)

The use of Gadolinium-153 in Single Photon Absorptiometry is well-established as it emits gamma photons ideal for measuring bone mineral density. This radioisotope has a half-life that allows for practical use in clinical settings, and the energy of its emitted photons is suited for the detection capabilities of standard bone densitometry equipment. Specifically, Gadolinium-153 provides the necessary stability and characteristics to accurately assess bone density, making it an optimal choice for this type of imaging.

In contrast, the other radioisotopes mentioned have different applications or are less suitable for bone density measurements. Gold-198 is primarily used in brachytherapy for cancer treatment; Iodine-125 is more common for thyroid studies and certain cancer treatments; Yttrium-90 is mainly used in radioimmunotherapy and not for assessing bone density. Therefore, the distinct properties of Gadolinium-153 make it the correct choice for use in Single Photon Absorptiometry.