Answers to questions on Nuclear medicine

1. (a)

(b) λt_½ = 0.693 so λ = 0.693 ÷ 6.01 = 0.115 h
λt = ln (N_o/N) so 0.115 x 4.50 = ln (10.0/N) where N = mass remaining after 4.50 hours
ln (10.0/N) = 0.5175 so N = 10 ÷ 1.678 = 5.96 mg

(c) Any three from: short radioactive half-live (6h), short biological half-life (1 day), forms salts
and complexes (so easy to administer), produces gamma radiation, radiation can be
detected by X-ray equipment, decay product (Tc-90) is a beta-emitter with a long half-life
so does little damage to the body.

(d)

2. (a)

(b) The patient is injected with non-radioactive boron-10, which targets cancerous cells. The
target area is then irradiated with neutrons. On their own neutrons cause no damage to
the body, when they hit the boron a nuclear reaction take place to release alpha particles
which act directly on the tumour.

(c) Alpha particles are high energy ionizing radiation so damage the targeted cancer cells but
they are readily absorbed over a very short range so do little damage to surrounding
healthy cells.

3. (a) Any three from: hair loss, nausea, fatigue, sterility, tissue damage, increased risk of
developing new tumours.

(b) MRI involves radio waves which are of very low energy/frequency so do no harm to the
body (although they do involve strong magnets so are not suitable for people fitted with a
pacemaker).

4. (a)       

(b) ) λt_½ = 0.693 so λ = 0.693 ÷ 10.64 = 0.0651 h
λt = ln (100/N) so 0.0651 x 48.0 = ln (100/N) where N = % mass remaining after 48 h
ln (100/N) = 3.125 so N = 100 ÷ 22.76 = 4.39%

Answers to Nuclear medicine questions