28: Radiation Toxicity Flashcards by Linda Chen

what is alpha decay

parent isotope losing 4 mass and 2 atomic number
2p+2n with double positive charge

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alpha particle decay occurs only for radionuclides with Z

> 83

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the alpha particle has a kinetic energy between ______ and is _____ for a particular radionuclide decay

between 4-8MeV
monoenergetic for a particular radionuclide decay

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the biological hazard from alpha particles is due to their ________ kinetic energy and ___ positive charge

high
double

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alpha particles are (select below)
1. large
2. small
3. penetrating
4. not very penetrating
5. easily absorbed
6. not very easily absorbed

1, 4, 5

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what drug undergoes alpha decay (2)

XOFIGO (radium Ra 223 dichloride)
Bi-DOTATOC

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what is the indication for XOFIGO

castration resistant prostate cancer

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ZOFIGO MOA

alpha emitter, Ra mimics Ca, taken up into bone to target bone metastesis

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XOFIGO’s _____, ____, and ________ minimizes toxicity

specificity, elimination, short half life

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Bi-DOTATOC indication

neuroendocrine tumor liver metastases

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_______ emitter drugs prevent normal cells getting caught in crossfire

alpha

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beta particle decay is characteristic for ________ with ____________

unstable nuclides with excess of neutrons (neutron rich species)

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in the beta particle decay process, the ______ spontaneously converts to a ______________ and _________. the _________ remains in the nucleus while the _______ is ejected

neutron
proton and beta particle
proton remains
beta particle ejected

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the emitted particle in beta particle decay is identical to an

electron

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how does A, Z, and N change in beta decay

A same
Z + 1
N-1

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what drug undergoes beta decay (3)

iodine-131
lobenguane
lutetium-177

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iodine-131 is used for

dx and tx of thyroid cancer, hyperthyroidism, thyroid carcinoma

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lobenguane is used for

adrenal gland tumors

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lutetium-177 targets

somatostatin receptors expressed on gastroenteropancreatic neuroendocrine tumors

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positron decay emits a particle identical to ______ but _______

identical to electron but + charge

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positron decay is characteristic for unstable radionuclides with ________

excess of protons in the nucleus (proton rich or neutron poor)

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in positron decay, a _______ converts to a _____ and a _______ is ejected

proton converted to a neutron and a positron (+ beta particle) is ejected

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how do A, Z, N change in positron decay

A same
Z-1
N+1

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what is the primary decay mechanism of technetium radiopharmaceuticals

isomeric transition

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the excited state of radionuclides is called __________ and is indicated by a _______

metastable superscripted m

when metastable states go to ground state, they release of energy in the form of a _____

gamma ray

what is the decay process where metastable states release energy in the form of gamma rays to go down to ground state

isomeric transition

the metastable species _____ is an important medical imaging radionuclide which decays by isomeric transition

99-mTc

T or F: 99-mTc can be built into many molecules to allow for imaging different organs

alpha particles cause _____ of targets and produces ________

ionization ion pair

which of the following is true about beta particles 1. they have the same energy as gamma rays] 2. they do not travel in a straight line 3. they travel further than alpha particles 4. they cause an antimatter + matter reaction 5. all of the above are true 6. 2, 3, 4 are true

6 Antimatter/mater rxn explanation: B+ particle --> rxn takes placein pET imaging. B+ interacts with e-, annihilate each other and release E which produces GAMMA RAYS (why PET imaging can be used, cuz you're looking at gamma rays).

positrons from internally targeted radioactive drugs are detected via ________ by specialized cameras to give 3D pet images

their gamma rays

_______ are very penetrating = main reason that lead and other dense shielding is used where radiopharmaceuticals are prepared or used

photons - gamma rays

_____ emission can occur during decay modes

photon

photons are _____energetic

mono

_______ and _________ have the same character as light, UV, and IR radiation but have higher energies

gamma rays and x rays

gamma rays are ___ path length, ____ specific ionization

long low

radiocontrast media + xrays = - What is radiocontrast media?

positive contrast media attenuate X rays more than body tissues iodinated copounds - radiocontrast media: is when you get molecuels of the target tisseu to absorb the radiation so can image.

the higher a relative osmolality of iodinated contrast media =

higher the toxicity

what osmolality of iodinated contrast media is best for lowest toxicity

iso

nonionic dimers are _____ but _________

less toxic but more expensive

ADRs of iodinated contrast agents

non-IgE allergic rxns (but behaves like AN ANAPHYLACTIC RxN - biggest risk is previous exposure and rxn like an IgE mediated allergic rxn) occur more with higher osmolality iodine containing compounds rate is much lower with lower osmolality

biggest risk of an ADR from iodinated contrast agents is

previous exposure and reaction

radiation safety can be assessed by determining factors such as

exposure and dose

the newer unit of an absorbed dose is

the gray (Gy)

1Gy = __ joule/ kilogram = ___ rad

1 joule/ kilo = 100 rad

T or F; the # of Gy reflects the actual damage caused by radiation

F- the different types of radiation have different capacity to cause damage even thought he energy absorbed is the same

relative hazard of radiation is related to ________ and ________

specific ionization (ion pairs produced per unit path length) and linear energy transfer (LET)

- What is the unit we use to measure the damaging effects of a radioactive molecule on humans? 1 Sv =? - what is the Weighting Ratio of gamma rays and beta particles? - what abouyt for alpha partilces?

- use the Sievert (Sv). Sievert unit= IMP MORE IN pop/public/Occupational health. 1 Sv= 1Gy x WR - 1, 20. MOST times, the WR is just 1.

the relative damaging potential of radioactive emissions is defined by ____ or _____

quality factor (Q) or weighing factor (WR)

the radiation equivalent dose is measured by

sieverts

list 3 cells that are highly radiosensitive

mature lymphocytes erythroblasts some spermatogonia (rapidly dividng cells)

list 3 cells that are highly radioresistant

fibrocytes, chondrocytes, muscle cells, nerve cells (slowly dividing cells)

the brain spinal chord could be considered _______radiosensitive

low

high doses of radiation acuses

acute radiation sickness

AEs from lower doses of radiation =

cancer (leukemia), shortened life span

1Gy = 1 ________

joule absorbed energy/ Kg

2-7Gy sees

hematopoietic sx, damage of bone marrow, infections as main issue

7-15 Gy sees

Gi sx, death after 5-10 days , GI mucosa destroyed

50 Gy sees

CNS sx, death in minutes to 48h, due to neurologic and CV degeneration

survivors rare rare at doses over ___Gy

5` all survivors increased risk of leukemia cancer latent period usually <15yrs

what is considered the LD50 of radiation in humans?

5Gy

list 3 sx of radiation sickness sx

N/V/D, HA, fever, dizziness and disorientation, weakness and fatigue, hair loss, bloody vomit and stools from internal bleeding, infections, low BP

list the 4 tx for radiation sickness

G-CSF (filgrastim)- bone marrow blood transfusion KI- outcompete radioactive I metal chelators (prussian blue, DTPA)