Radiopharmacy (Cheng)

Question 1

What are radiopharmaceutcials?

Answer 1

a dosage form consisting of radioactive compounds used for wither the diagnosis or therapeutic treatment of human diseases

Question 2

What gives an unstable nucleus?

Answer 2

change in the number of neutrons (N)

Question 3

What does Z stand for?

Answer 3

atomic number

Question 4

Z > 83

Answer 4

radioactive

Question 5

What happens when radionuclides decay?

Answer 5

they emit particles/energy in the form of stable nuclide

- alpha, beta, positron, neutrons, gamma

Question 6

Where is alpha decay seen?

Answer 6

heavy metals (uranium)

Question 7

What is alpha emission? (alpha, 4He nucleus)

Answer 7

2+ charge of high energy and limitied penetration range

-> nucleus has too many protons

Question 8

What is beta decay? (beta-)

Answer 8

various energy
random motion
negative charge
-> nucleus is neutron rich

Question 9

What are gamma rays/gamma decay? (y)

Answer 9

when nucleus energy is too high
no mass loss
photon energy
high penetration range
isomeric transition - exicted nucleus emits gamma rays
-> if isomeric state is long lasting then it’s meta stable (m)

Question 10

What is positron decay? (beta+)

Answer 10

positive charge (loss is a proton)
various energy
random motion
proton rich

Question 11

What is neutron emission? (n)

Answer 11

during fusion of heavy metals
no charge loss
loss of mass

Question 12

What is the disintegrating rate?

Answer 12

average number of nuclei that disintegrate during a period of time

Question 13

What is physical half life?

Answer 13

time required to reduce the initial disintegrating rate or activity to one half (outside the body)
tp

Question 14

What is biological half life?

Answer 14

time needed for half of the radiopharmaceutical or radionuclide to disappear from the biological system (inside body)
tb

Question 15

effective half life (te) formula

Answer 15

1/te = 1/tb + 1/tp

Question 16

dps

Answer 16

disintegrations per second

Question 17

units for radioactivity

Answer 17

curies (Ci)

Bacquerel (Bq) - SI unit

Question 18

How to convert Curies to Bacquerel

Answer 18

1 Bq = 2.7 x 10^-11 Ci

Question 19

How to produce radionuclides?

Answer 19

nuclear reactor (neutrons)
OR
cyclotron (charged particles)

Question 20

What does a nuclear reactor do?

Answer 20

produces neutron rich radionuclides

-> fission/reaction of 235U or 239Pu

Question 21

What does a cyclotron do?

Answer 21

produces proton rich radionuclides

Question 22

properties of reactor/cyclotron

Answer 22

expensive

produce radionuclides have long half life

Question 23

What is used for radiopharmacy in hospitals?

Answer 23

generator system

• portable and reusable system
• lead shiels
• radionuclides have short half life
• cheaper

Question 24

What is the most widely used imaging radionuclide?

Answer 24

99Mo to produce 99mTc

-> molybdenum and technetium

Question 25

How is 99Mo produced?

Answer 25

from 235U fission | uranium

Question 26

solid and solvent phase in 99Mo 99mTc generator

Answer 26

solid - alumina column | solvent - 0.9% saline

Question 27

properties of 99Mo 99mTc generator

Answer 27

sterile and pyrogen free | physiological pH and isotonic

Question 28

What element is Tc?

Answer 28

technetium

Question 29

dosage forms of radiopharmaceuticals

Answer 29

``` solution suspension capsule gas -> in a lead container ```

Question 30

forms of radiopharmaceuticals

Answer 30

ions molecules complexes

Question 31

What is idrect labeling?

Answer 31

- tagging radioisotope with biological molecules | - non-specific binding to antibodies, RBC etc

Question 32

How to label 99mTc with chelate?

Answer 32

- the oxidation state of Tc needs to be lower (1+ - 5+) - use reducing agents like stannous chloride (SnCl2) in acid - > lowers Tc oxidation state - use a chelating agent - > donates a lp of e- to Tc to form a stable complex by formation of a covalent bond

Question 33

How to lower the oxidation state of 99mTc?

Answer 33

use a reducing agent in acid | -> SnCl2 (stannous chloride)

Question 34

How to stabilise the bonds in 99mTc?

Answer 34

using a chelating agent - it donates a lp of electrons to Tc - coordinates a covalent bond to stabilise 99mTc

Question 35

2 structures of 99mTc labelled complexes

Answer 35

Tc-HMPAO Tc-sestamibi

Question 36

What do commercial 99mTc labelling kits contain?

Answer 36

NO RADIOISOTOPE - reducing agent (SnCl2) - chelating agent - antimicrobial - antioxidant - buffers (acid/base) - solution or lyophilised powder - vials for reconstitution/reaction

Question 37

What does the antimicrobial do in a labelling kit and an example?

Answer 37

benzyl alcohol | maintains sterility of the kit

Question 38

What do antioxidants do and example of one in labelling kit?

Answer 38

sodium bisulfite | avoid re-oxidation of reduced Tc if Sn delpetes

Question 39

What do buffers do in labelling kit?

Answer 39

maintain pH of the kit

Question 40

2 types of quality control tests for radiopharmaceuticals

Answer 40

1. physiochemical tests | 2. biological tests

Question 41

What do physiochemical tests do in quality control of radiopharmaceuticals?

Answer 41

- radioactivity and specific radioactivity - radionuclidic species and radionuclidic purity - chemical purity for radiopharmaceuticals and radiochemical purity - particle size - pH

Question 42

What do biological tests do in quality control?

Answer 42

sterility and pyrogen tests

Question 43

What is radionuclidic purity?

Answer 43

fraction of total radioactivity in form of the desired radionuclide present in a radiopharmaceutical

Question 44

Where can impurities come from?

Answer 44

extraneous nuclear reaction | isotope impurities in target materials

Question 45

impurity in 99mTc

Answer 45

99Mo

Question 46

What detects impurities in radionuclidic?

Answer 46

gamma spectrometry

Question 47

What is radiochemical purity?

Answer 47

fraction of total radioactivity in desired chemical form in a radiopharmaceutical

Question 48

What can cause radiochemical impurity?

Answer 48

decomopsition action of solvent, heat, light and radiolysis

Question 49

What detects radiochemical impurities?

Answer 49

chromatographic techniques

Question 50

examples of radiochemical impurities

Answer 50

free 99mTcO4- OR hydrolysed 99mTcO2 in 99mTc labelled albumin

Question 51

What does specific activity mean?

Answer 51

total amount of radioactivity per unit mass of a radionuclide or labelled compounds

Question 52

What does specific activity account for?

Answer 52

radioactive concentrations and chemical substance concentrations

Question 53

What does specific activity change with?

Answer 53

date and time

Question 54

What is radiolysis?

Answer 54

decomposition of radiopharmaceutical by radiation | -> 2 types - auto-radiolysis and indirect radiolysis

Question 55

What is auto-radiolysis?

Answer 55

absorption of radiation leads to free radical formation

Question 56

What is indirect radiolysis?

Answer 56

production of peroxide or radical from decomposition of water

Question 57

What does stability of radiolaballed product depend on?

Answer 57

specific activity energy of emitted radiation half life

Question 58

Why can positrons be given at a higher dose and higher radiation dosing?

Answer 58

they have a very short half life

Question 59

How to image the thyroid gland?

Answer 59

- radioactive iodine given as sodium iodide 131I or 123I capsule given orally - uptake is monitored, gamma detector used - absorbed into thyroid gland - 10-35% after 24hrs - hot spot = hyperthyroidism - cold spot = carcinoma

Question 60

What is used for thyroid imaging?

Answer 60

sodium iodine-123 or I-131

Question 61

alternative for sodium iodine for thyroid imaging

Answer 61

99mTc pertechnetate preparation

Question 62

What radiopharmaceutcials are used as therapeutic agents?

Answer 62

- particle emitters - alpha and beta ionisation energy - direct/indirect free radical induction - permanent damage to DNA - induces cellular apoptosis

Question 63

How do alpha/beta particles cause permanent damage to DNA?

Answer 63

via strand clevage and base pair mutations

Question 64

How to treat bone matastasis with radiopharmaceuticals?

Answer 64

- 32 P-sodium orthophosphate IV (radioactive sodium phosphate injection) - deposits in the bone

Question 65

What radiopharmaceutical is used to treat hyperthyroidism?

Answer 65

NaI (131 I) - sodium iodine 131 emits beta- and gamma rays/particles larger gland = larger dose