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PHA 332 > radiopharmacy > Flashcards

radiopharmacy Flashcards

1
Q

what is a radiopharmaceutical?

A

A dosage form consisting of radioactive
compound used for either the diagnosis or
therapeutic treatment of human diseases

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2
Q

how are the atomic number and the number of neutrons properties of radionuclides?

A

• Unstable nuclides
– N/Z ratio away from stable isotopes
– Z ≥83

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3
Q

how do radionuclides decay?

A

emits particles and/ or energy- this gives a more stable nuclide

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4
Q

what are the forms in which it can emit particles?

A 
– Alpha (or 4He)
– Beta (- or e-)
– Positron (+)
– Neutrons (n)
– Gamma ()
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5
Q

what are the properties of an alpha decay emission?(a or 4He nucleus)

A

– 2 + charge, high energy and limited penetration range (~10-6 cm)

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6
Q

what are the properties of a beta decay emission?

A

– Various energy, random motion, negative charge
– “neutron rich”
e.g. 13153 I > 13154Xe + B- + u

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7
Q

what are the properties of a gamma ray decay?

A

– No mass, photon energy, high penetration range

– Isomeric transition

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8
Q

what are the properties of a positron decay emission?

A

– Positive charge; various energy, random motion
– Proton rich
– Annihilation (2 x 511 keV ~180°)

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9
Q

what are the properties of neutrons decay emission?

A

no charge, loss of mass

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10
Q

what kind of phenomenon is a radioactive decay?

A

Radioactive decay is a statistical phenomenon

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11
Q

what is the equation for the radioactive decay?

A

-dn/dt = a N
where dn/dt = disintegrating rate
a= decay constant; N = no. of radionuclides

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12
Q

why would we integrate the formula for radioactive decay?

A

Nt = Noe^-at
• where No= no. of radionuclide at time = 0;
Nt = no. of radionuclide at time = t

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13
Q

what is the equation for activity (A)?

A

Radioactivity of nuclide where At = Aoe^-at

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14
Q

what is the equation for exponential decay?

A

ln At = In Ao - at

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15
Q

what is the physical half life?

A

tp= Time required to reduce the initial disintegrating rate

or activity to one-half•

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16
Q

what is the equation for the physical half life?=outside the body

A

tp= ln2/ap , where 2- 0.693

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17
Q

what is the biological half life?

A

Time needed for half of the radiopharmaceutical or

radionuclide to disappear from the biological system

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18
Q

what is the equation for the biological half life?

A

tb=ln2/ab

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19
Q

what is the equation for the effective half life?

A

1/te=t/tb+1/tp

20
Q

what are the units of radioactivity?- KNOW HOW TO CONVERT

A

Curies (Ci)
1 Ci = 3.7 x 1010 dps (disintegrations per sec)
1 mCi = 3.7 x 107 dps
1 uCi = 3.7 x 104 dps

• Bacquerel (Bq) – SI Unit
1 Bq =    1  dps =  2.7 x 10-11 Ci
1 kBq = 103 dps
1 MBq = 106 dps
1 GBq = 109 dps
21
Q

what is a nuclear reactor?

A

neurons
– Fission or (n, f) reaction of 235U or 239Pu
– Produce neutron rich radionuclides

22
Q

what is a cyclotron?

A

charged particles
– (p,n), (d,n) reactions most common
– Produce proton rich radionuclides
• Expensive production facility → Site produced
• Monoisotropic or enriched source as target form
• Radionuclides with long half life

23
Q

what is a generator system?

A 
• Radiopharmacy unit in hospital 
• Portable & reusable system 
• Lead shield 
• Radionuclides with short half life
• Reasonable half life of parent & 
daughter*
24
Q

how is 99MO made?

A

from 235 fission

25
Q

what method is mostly used for 99,o-99mtc?

A

generator

use imaging radionucllide

26
Q

what are the benefits of using the generator

A

Simple elution method & reliable separation

27
Q

what is the solid, solvent phase of the generator method?

A

Solid phase: alumina column

• Solvent phase: 0.9% saline

28
Q

is the generator method sterile and pyrogen free?

A

yes

29
Q

what forms do the radiopharmaceutical dosage forms come in?

A

solution, suspension, capsule and gas

30
Q

what type of container do radiopharmaceutical dosage forms have?

A

lead

31
Q

what is an appropriate form for a radiopharmaceutical?

A

– Ensure radionuclides distribute to target site– Remain stable in vitro & in vivo

32
Q

what is direct labelling?

A

e.g. 125I-albumin Injection– Tagging radioisotope with biological molecules– Non-specific binding to antibodies, RBC, etc.

33
Q

how to you label 99mTC with chelate?

A

• Oxidation state of Tc
– Tc 7+ to lower values (1+, 3+, 4+, 5+)
– Reducing agents, SnCl2 (stannous chloride) in acid
• Chelating agent
– Coordination donor atoms, e.g. N, O, S, P etc
– Donate lone pair electrons
– Coordinate covalent bond stabilises 99mTc

34
Q

what makes up the strructure of 99m tc complex?

A

• Property of complex
– Chelating agent
– Ring size, charge and geometry
– Determine distribution in the body

35
Q

what is included in a labelling kit?

A 
• No radioisotope
• Reducing agent, e.g. SnCl2
• Chelating agent
• Antimicrobial, e.g. benzyl alcohol 
• Antioxidant, e.g. Sodium bisulfite
– Avoid re-oxidation of reduced Tc upon Sndepletion 
 • Buffers, acid or base 
• Solution or lyophilised powder 
• Separate vials for reconstitution or reaction
36
Q

how do you assure the quality of a radiopharmaceutical?

A

• Quality assurance scheme
• Precursor & kit additives and their quality
• Physicochemical tests
-biological tests

37
Q

what physiochemical tests are availible for quality tests?

A

– Radioactivity & specific radioactivity
– Radionuclidic species & radionuclidic purity
– Chemical purity for radiopharmaceuticals &
radiochemical purity
– Particle size
– pH

38
Q

define radionulidic purity

A

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

39
Q

what do impurities arise from?

A

– Extraneous nuclear reaction

– Isotope impurities in target materials

40
Q

what is the specific activity?

A

Radioactivity per unit mass of a radionuclide or

labelled compounds

41
Q

what do you account for with specific activity?

A

Accounted for radioactive and chemical substance
concentrations
– Radioactivity from radionuclide (radionuclidic
purity)*
– Chemical species (radiochemical purity)*

42
Q

how does specific activity change?

A

changes with date and time

43
Q

how do you determine the stability of a radiolabeled product?

A

• Radiolysis
– Decomposition of radiopharmaceutical by radiation
– Auto-radiolysis & indirect radiolysis
– Absorption of radiation lead to free radical
formation
– e.g. water is irradiated to form H2O2 or HO2. radical
– Depends on specific activity, energy of emitted
radiation & half life
– e.g. Particle emission is more damaging than ray

44
Q

how does imaging of the thyroid gland work?

A 
Sodium Iodide (131I) or 
(123I) capsule
•Oral route
•Monitored uptake 
•10-35% after 24hr
• Hot spot 
(hyperthyroidism) 
•Cold spot (carcinoma)
• Trapping iodine 
source in thyroid
• Alternative 99mTc  
Pertechnetate
preparation
45
Q

how does thyroid imaging work?

A 
• Trapping iodine 
source in thyroid
• Alternative 99mTc  
Pertechnetate
preparation
46
Q

how are radiopharmaceuticals used ar rgerapeutic agents?

A 
• Particle emitters, e.g.  , 
• Ionization  energy
– Direct and indirect by free radical induction 
(e.g. R., OH., HOO.)
• Permanent damage to DNA via strand cleavage & 
base pair mutation
• Induce cellular apoptosis 
• Distance from site of action
47
Q

give examples of radiopharmaceutics for therapeutic use

A 
• Non-Hodgkin’s Lymphoma
– 90Y-ibritumomab Tiuxetan(Zevalin®)
– Active targeting 
• Bone metastasis
– 32P-Sodium 
orthophosphate  IV
– Deposit in the bone 
• Hyperthyroidism
– Excess thyroid hormone 
activity
– NaI( 131I) emit - (90%) & 
– Active uptake

PHA 332 (42 decks)

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