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PHAR 262 > Iodine Labelling Radiopharm > Flashcards

Iodine Labelling Radiopharm Flashcards

1
Q

which iodine isotope was commonly used for in vitro procedures?

A

I-125

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2
Q

NaI (sodium iodide) is (un/labelled).

A

unlabelled

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3
Q

half life for I-123

A

13.2 hrs

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4
Q

half life for I-131

A

8.05 days

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5
Q

decay method/product of I-123

A

electron capture
123Te

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6
Q

decay method/product of I-131

A

negatron decay (B- emission)
131-Xe

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7
Q

photon energy for I-123

A

159 keV (83%), 27 keV x-rays (71%)

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8
Q

photon energy for I-131

A

364 keV (82%), 637 keV (7%)

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9
Q

between I-131 and I-123, what can be used for imaging? for therapy?

A

imaging - I-123 (I-131 can also but not ideal)

therapy - I-131

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10
Q

mode of production for I-123

A

cyclotron

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11
Q

mode of production for I-131

A

fission (or neutron activation)

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12
Q

what is I-123 used for?

A
  • thyroid uptake and scan
  • WB scan for thyroid mets
  • labelled to MIBG for adrenal medulla imaging
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13
Q

what is I-131 used for?

A
  • therapy for thyroid ca and hyperthyroidism
  • labelled to MIBG for imaging or to treat specific malignancies
  • thyroid uptake and scan
  • WB scans
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14
Q

what are the three oxidation states iodine can exist in?

A

1-, 0, 1+

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15
Q

what causes oxidation of iodine?

A

acidity, free radicals and free radical byproducts
heat and light accelerates oxidation runs
high conc of radioactivity
Cl- ions

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16
Q

oxidation is more of an issue with ___. why?

A

I-131
beta emission causes more radiolysis and more free radicals
has longer half-life and higher energy

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17
Q

what is done to limit oxidation?

A
  • using buffer to keep pH 7-8.5
  • addition of reducing agents and antioxidants
  • low amts of activity
  • diluting with dH2O to limit presence of Cl-
  • adding EDTA (chelating agents)
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18
Q

what does EDTA do?

A

binds with extraneous metals to prevent them from causing oxidation

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19
Q

radioiodination

A

labelling with radioiodine

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20
Q

two methods for radioiodination

A
  1. isotope exchange
  2. introduction of foreign label
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21
Q

isotope exchange

A

swapping stable nuclide
(I-127 exchanged for radio iodine)

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22
Q

which radioiodination method requires iodide to be oxidized first?

A

intro to a foreign label

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23
Q

iodine is most commonly labelled to ___.

A

proteins
ring structures in amino acids or other organic molecules

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24
Q

3 forms of I-131

A

solution, capsule, fillable capsule

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25
what form is dose activity adjusted?
solution and fillable capsule
26
what form is dose activity not able to be adjusted?
capsule
27
what do I-131 capsules contain?
- dibasic sodium phosphate (absorbing buffer) - sucrose filler
28
when I-131 is administered orally, it clears the gastrointestinal tract by __ hrs and goes where?
1-2 hrs, and gets reabsorbed into the bloodstream
29
faster reabsorption into bloodstream in (hypo/hyper)thyroidism pts
hyper
30
I-131 is used by the body to produce which hormones?
T3 and T4
31
organification
use of I-131 by the thyroid to produce thyroid hormones "body using it for its natural purpose"
32
where does I-131 localize?
stomach
33
how is I-131 secreted?
by the gastric mucosa
34
when do we typically see liver uptake in thyroid scans? why?
we usually see liver uptake in post-therapy images this is because we will be using higher doses. the body (thyroid) will use the radioiodine to produce T4, which localizes in the liver.
35
where are additional uptake of I-131?
salivary glands, breast milk and crosses placental barrier
36
what is method of excretion for I-131?
kidneys/bladder
37
uses for I-131?
- thyroid uptake procedures - WB imaging for thyroid Ca - ablation of thyroid Ca - hyperthyroidism - thyroid gland scanning
38
dose of I-131 for thyroid uptake?
0.15-0.37 MBq
39
dose of I-131 for WB imaging?
37 - 185 MBq
40
dose of I-131 for thyroid imaging?
3.7 MBq *low dose so image quality will be poor therefore, Tc-99m preferred for thyroid imaging
41
what is the range of I-131 used for thyroid ca therapy?
1110-7400 MBq
42
what range of I-131 is used for remaining thyroid tissue?
30-100 mCi
43
what is the difference between regional mets vs. distant mets?
regional mets = mets in chest area (not far from region of origin) distant mets = met is elsewhere in the body
44
what is the range of I-131 used for regional mets?
150 mCi
45
what is the range of I-131 used for distant mets?
200 mCi
46
thyroid ca therapy is patient dependent, what's used to determine the appropriate dose?
specific absorbed dose to residual tissue and where the mets is seen
47
hyperthyroidism therapy is patient dependent, what's used to determine the appropriate dose?
pt's thyroid uptake, U/S results and type of pathology
48
what is the dose used for hyperthyroidism therapy?
370-1110 MBq
49
what are the three methods to determine the dose used for hyperthyroidism?
1. fixed dose 2. dose per mass 3. radiation absorbed mass* *most patient specific
50
fixed dose
patients with similar pathology get the same dose
51
dose per mass
biological uptake and gland weight are considered 2-7 MBq/g
52
radiation absorbed dose
biological uptake, gland weight and effective half-life are considered
53
QC for I-131
- visual check - expiry check (14 days to 5 weeks) - proper storage - pH 7.5-9.0
54
dose of I-123 for thyroid uptake
1.85 - 3.7 MBq
55
dose of I-123 for WB imaging
up to 37-74 MBq
56
Dose of I-123 for thyroid imaging
7.4-22.2 MBq
57
what is the shelf-life for I-123?
30 hrs
58
Azedra
I-131 MIBG
59
AndreView
I-123 MIBG
60
I-123 MIBG vials contains
370 MBq of activity
61
I-131 MIBG diagnostic vials contain
1110 MBq
62
I-131 MIBG therapeutic vials contain
12,500 MBq
63
which vial is frozen?
I-131 MIBG
64
how does labelling radioiodine and MIBG occur?
isotope exchange (radioiodine replaces stable iodine)
65
MIBG is an analogue of ____.
norepinephrine
66
localization of MIBG
adrenal medulla
67
what is the main use of MIBG?
localization of neuroendocrine tumours
68
where do you see uptake of MIBG?
- tissues with extensive sympathetic innervation (salivary glands, nasopharynx, heart) - liver/spleen - adrenal medullas
69
MIBG route of excretion
kidneys/bladder
70
critical organ for MIBG
I-123: bladder wall, liver I-131: salivary glands

PHAR 262 (12 decks)

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