Dose and Nuclear Medicine

Question 1

2 forms of radiation

Answer 1

indirect/direct action

Question 2

indirect action

Answer 2

electron interacts with a water molecule to produce a radical which damages the DNA

Question 3

direct action

Answer 3

electron interacts directly with DNA

Question 4

Radiation dose definition

Answer 4

energy deposited in matter by ionizing radiation per unit mass

Question 5

Energy fluence

Answer 5

fluence (change in the number of particles with respect to change in unit area) x energy of the particle in a monoenergetic beam

Question 6

mass energy transfer coefficient

Answer 6

product of the mass attenuation coefficient and the fraction of energy transferred to the patient as a result of the type of interaction

Question 7

locally transferred meaning

Answer 7

absorbed by a local region

Question 8

Difference between KERMA and Dose

Answer 8

KERMA : Total energy transferred to a local region vs Total energy absobred by a local region

Question 9

Weighting by tissue

Answer 9

S_v (sievert / dose absorbed by tissue) = Dose x Weighting by tissue

Question 10

imaging particles

Answer 10

gamma rays

Question 11

therapeutic particles

Answer 11

electrons

Question 12

Decay processes involved in gamma imaging

Answer 12

Beta decay
Beta+ decay
Electron capture

Question 13

Transition processes

Answer 13

unstable nuclei with gamma emissions
isomeric transition

Question 14

Beta- decay

Answer 14

neutron rich isotope
beta- is emitted
charge must be conserved
proton is therefore emitted

Question 15

beta- decay where is the excedent energy transferred to

Answer 15

gamma rays

Question 16

beta+ decay

Answer 16

proton-rich isotope to stabilise the n/p ratio (increase)
neutron is emitted
positron is emitted in the form of gamma rays

Question 17

what happens to beta+ particle

Answer 17

loses energy to surrounding tissue
annihiates with an electron
opposite charge
produces 2 photons (pair production)

Question 18

Electron capture

Answer 18

orbital electron is captured by the nucleus and combines with a proton to become a neutron

Question 19

Change in number of electrons due to electron capture

Answer 19

-1 electron
vacancy in the atomic shell filled by another electron
photoelectric effect
energy released when electron falls by energy levels in the form of x-ray

Question 20

Isomeric transition

Answer 20

decay into an unstable state for a while
which then decays to another state where a gamma ray is emitted

Question 21

why does beta produce dose

Answer 21

low energy lose it quickly and stop in the body

Question 22

properties of a useful isotope

Answer 22

emit gamma or x rays only as those are what appear on the image
medium energy emissions
appropriate half life (few minutes - hours )
easily produced