Lecture 1 and 10: Basics and basic radioactivity

Question 1

What is a radiopharmacutical? (2 marks)

Answer 1

It has two components:

• A radionuclide which is a radioactive element which is bound to a pharmacetical, e.g. Tc-99m
• The pharmaceutical which goes to the region of interest in the body, such as FDG which is metabolised by cells

Question 2

How can radionuclides be produced? Give two methods and two RN for each method. (4 marks)

Answer 2

Nuclear fission: generally larger RN like Mo-99 (Tc-99m) or I-131

Cyclotron: bombardment with charged particles (protons), like C-11 or O-15

Question 3

Why is Tc-99m an ideal RN? (3 marks)

Answer 3

• Only emits gamma
• Binds easily to many pharmaceuticals
• Reasonable HL for imaging, 6 hrs, decays fast enough to be disposed of quickly and reduce dose and yet long enough to be usable for imaging

Question 4

What is the shape of the stability curve? And how do unstable isotopes decay? (4 marks)

Answer 4

Neutrons on the y-axis, protons (Z) on the x-axis.

Gradual x^2 type relationship.

If too many neutrons (above the line) then decay via B- (n -> p + B-)

If too many protons (below the line) then decay via B+ (p -> n + B+)

Question 5

Give an example decay for the four types of decay. (8 marks)

Answer 5

ur sex 2n -> MTB- (42) -> FOB -> Crv

236U -> 90Sr + 144Xe + 2n
99Mo42 -> 99Tcm43 + B-
18F9 -> 18O8 + B+
51Cr24 + e -> 51V23 (used in RBC)