Question

a. Technetium-99m emits only gamma radiation. Why would this type of radiation be used in diagnostic imaging rather than an isotope that also emits beta or alpha radiation?

b. A person with polycythemia vera (excess production of red blood cells) receives radioactive phosphorus-$32$. Why would this treatment reduce the production of red blood cells in the bone marrow of the patient?

Short answer

(part a) Because gamma radiations penetrate deeper in tissues in comparison to alpha and beta radiations.

(part b) It checks the division of cells in the bone marrow of a patient.

Step-by-step solution

Given information (part a)

In comparison to alpha and beta radiations, gamma radiation penetrates deeper into tissues.

Explanation (part a)

(part a) Technetium - $99m$only emits gamma rays. Because gamma radiation penetrates deeper into tissues than alpha or beta radiation, it is employed exclusively in diagnostic imaging rather than an isotope that also emits beta or alpha radiations.

The gamma rays released by the organ's radioactive isotope can be utilized to expose a photographic plate, resulting in an organ scan. Increased or decreased radiation can suggest the presence of sick conditions such as a tumor, blood clot, or edema.

Given information (part b) 

It examines the division of cells in a patient's bone marrow.

Explanation (part b)

(part b) A patient with polycythemia is given radioactive phosphorus - $32$, which inhibits the generation of red blood cells in the patient's bone marrow by preventing cell division.