Which of the following is true regarding the administration of 99mTc-labeled compounds?

The statement that written directives are necessary for mostly all radiopharmaceuticals is correct because regulations and guidelines established by bodies such as the Nuclear Regulatory Commission (NRC) require that written directives be in place for the administration of radiopharmaceuticals. This is particularly essential for ensuring the appropriate use, dosimetry, and safety of the radiopharmaceuticals administered to patients.

Written directives help ensure that the correct radiopharmaceutical is administered at the right dose, which is critical for achieving the desired diagnostic or therapeutic effect while minimizing risks to the patient. Specifically for 99mTc-labeled compounds and other radiopharmaceuticals, adherence to these procedures maintains compliance with safety protocols and promotes optimal patient outcomes.

While there are exceptions to this requirement in certain instances, the broader rule supports the necessity of written directives as a standardized practice in the administration of radiopharmaceuticals to ensure patient safety and adherence to regulatory standards.