What simple method is used to evaluate the presence of 99Mo in 99mTc samples?

The use of a lead shield, commonly referred to as a lead pig, is the correct method for evaluating the presence of 99Mo in 99mTc samples. This approach is essential because lead effectively attenuates gamma radiation emitted from the 99Mo radionuclide, which can interfere with the accurate measurement of 99mTc, a desired radiopharmaceutical used in medical imaging.

When 99Mo decays, it produces gamma radiation that can be detected. However, to isolate the detection of 99mTc, which is the radioisotope of interest in diagnostic imaging, it is crucial to shield against the radiation from 99Mo. The lead pig not only serves as a barrier to this radiation but also ensures that any measurements taken reflect only the activity of 99mTc.

Other methods listed, such as photometric or ultrasound imaging techniques, do not specifically address the evaluation of gamma radiation in this context and are not suitable for distinguishing between these two isotopes in a way that would ensure safety and accuracy in a clinical setting.