Ch. 4-5 Test Nuc Med I

No

Can we predict the exact moment an unstable nucleus will decay?

probabilities; average decay rates

Radioactive decay is described in terms of _____ and _______

change in activity divided by change of time equals negative gamma times sample size

decay rate (explained in words)

decay constant

in the decay rate equation, gamma is the _______

(time)^-1

the units of λ are

1% of the atoms undergo radioactive decay per second

if λ - 0.01sec^-1 , that means:

no, only an estimate

is the decay rate an exact measurement?

that the amount of radioactive atoms decreases over time

What does the negative sign in front of the λ (gamma) mean?

F18

What is an example of a radionuclide that can undergo more than one type of radioactive decay?

Branching ratio (B.R.)

the specific fraction of nuclei decaying by a single decay mode

activity

The quantity demonstrating the average decay rate gives us the of ________ any given radioactive sample

decay rate

(∆N/∆t)

disintegrations per second (dps) or disintegrations per minute (dpm)

what is the designation (units) of the decay rate

radioactive

dps and dpm is the measure of how ______ the sample is

Becquerel (Bq)

SI units for activity is

1 sec^-1 (1dps)

1 Bq has a decay average of

Curie (Ci)

Traditional (first) unit for activity is the

the activity of 1g of 226-Ra

how was a Curie originally defined?

3.7 × 10¹⁰ dps

what is the updated and accepted value for a Curie

1 Ci = 3.7×10¹⁰ Bq

conversion from Curie to Becquerel

disintegration events ; decreases

Overtime, due to _________, the total amount of radioactive atoms in a source ________.

fixed

the rate of decay is ______ by the decay factor

N_f=N_i * e^-kt

rate of decay equation

decay factor

𝞴 in the rate of decay equation represents:

the half life

T (time) needs to be in the same units as ___

fraction of radioactive atoms remaining after the set time has passed

what does the factor e^-kt represent?

half-life

The time any given radionuclide requires to have its initial activity decay by 50%

The time any given radionuclide requires to have its initial activity decay by 50%

explain half-life

T_1/2 = Ln2/k

half-life and decay constant is related through this formula

0.693

Ln2 is roughly equal to

T = T_1/2 /ln2

Formula for average lifetime

1.44

The average lifetime for the atoms of a radionuclide is longer than its half-life by a factor of ____

with carrier

A radioactive sample may also contain stable isotopes of the element that are different from the desired radionuclide. This smaple is referred to as ____

the amount of stable isotopes found in the radioactive sample

explain what a carrier is

carrier free

a sample that does not contain stable isotopes of the element a called

carrier-free

what type of sample do we want as pharmaceuticals?

specific activity

the ratio of radioisotope activity to total mass of the element present is called the _______ of the sample

Bq/g

Units for specific activity

Carrier-Free Specific Activity (CFSA)

the highest possible activity of a radionuclide is its

100% pure concentration

CSFA means about the concentration

due to a large amount of radiation only needing a very small amount of liquid for an injection

why is high specific activity desirable for Nuclear Medicine?

Arsenic

What toxic element did nuclear medicine used to use in low enough doses

No

Can 99m Tc be separated from its daughter product 99 Tc?

increased ionization

In rare occasions, the carrier portion can help encourage the compounding of certain druges due to the _______ of the fluid

137 Cs and 137m Ba

What radionuclides are used for QC everyday

long

Naturally occurring radionuclides have an extremely ___ half-life

no because of their extremely long half-life

Can we use naturally occurring radionuclides? Why or why not?

artificially synthesized through various means of proton/neutron bombardment

How are radionuclides made today?

fission material, specifically 235 U and 238 U

What does the core of a nuclear reactor contain?

7×10⁸ years

Half life of U 235

this reaction caused 2 lighter nuclear fragments to be emitted with 2-3 fission neutrons as well

explain the nuclear reactor reaction of 235 U (think about notes)

235 U + n —> 236 U*

what is the desired goal for nuclear fission

it is extremely unstable and immediately undergoes nuclear fission

Why do we want 236 U*

a self-sustaining nuclear chain reaction takes place

What happens when the reaction in a nuclear reactor reaches equilibrium

200-300 MeV

about how much energy does each nuclear fission event reach per fission fragment

revolves around the neutron flux ; inserting and removing elements to selectively transmute them into the desired radioisotope

secondary method of producing radionuclides

fission material (Uranium)

in a nuclear reactor: fuel cells are ___

to slow down the energetic fission neutrons

What is the purpose of the moderator material

heavy water (D₂O) and graphite

in a nuclear reactor: Moderator material is ___

heavy water, where all hydrogen atoms are replaced with deuterium, a heavy isotope of hydrogen

What is D₂O

efficient initiators of additional fission events

in a nuclear reactor: the slow neutrons (thermal neutrons) emitted are more ____________

position to either expose or shield the fuel cells from one another

in a nuclear reactor, what are the control rods used for

materials that are strong neutron absorbers (Cadmium or Boron)

What do the control rods contain

nuclear meltdown

What happened if the control rods are improperly positioned or removed completely

235/9U —> 236*/9U —> 144/56Ba + 89/36Kr + 3n

fission process gives nuclear medicine most of the medically important radionuclides

100 nuclides representing 20 different elements

how many nuclides can be produced as a fission by product?

85-105; 130-150

one fission fragment usually has a mass number in the range of ______ while the other is around ____

neutrons; B- emission

Because fission products always have an excess of _____ they undergo radioactive decay by _______ until stability is reached

99 Mo

what is the parent material in the 99m Tc generator?

extract it and separate it from the other fission fragments.

When an intermediate isotope has a long half-life we can …

99 Mo

an example of an intermediate isotope with a long half-life is

because of Uranium’s high neutron count

Why do fission products always have an excess of neutrons?

specific activity (Bq/g)

fission products can be carrier free thereby producing radionuclides with very high _____

other contaminates of Iodine 123, 125, 131

in the case of 131 I, why is specific activity low?

specificity

fission production lacks _____ for a single fission process

produces a relatively low yield of the large amount of radionuclides it produces

fission production overall:

captured

when neutrons strike a target, some of the neutrons are _____ by the nuclei of the target atoms

radioactive product nucleus

the target nucleus in neutron activation may be converted into a ________ as a result of capturing neutrons

a target nucleus captures a neutron and in converted into a product nucleus which is formed in an excited state

(n, y) reaction

A+1/Z X*

symbol for product nucleus in an (n,y) reaction

the exited nucleus immediately undergoes de-excitation to its ground state by immediate gamma ray emission

(n,y) reaction second step

gamma ray

what is emitted during a (n,y) reaction

different isotopes of the same chemical element

target and product nuclei of the (n,y) reaction represent:

a target nucleus captured a neutron and promptly ejects a proton

(n,p) reaction

a proton

what is emitted from a (n,p) reaction

do not represent the same element

the target and production nuclei in a (n,p) reaction:

the intensity of neutron flux and neutron energies

production yield of an (n,p) reaction depends on:

above it

where do products of neutron activation lie on the line of stability?

activating a short-lived intermediate product

the most common production mode is by (n,y) reaction, it is dont by:

130 Te —(n,y)—>131 Te —B- —> 131 I

the most common (n,y) reaction example

low ; unactivated stable carrier

(n,y) products have a very ____ specific activity due to the overwhelming presence of ______ ____ _____ leftover from the reaction

50 Cr —> 51 Cr

What may be produced using complicated techniques through EC?

Electron Capture

50 Cr —>51 CR may be produced through what

18 F

Positron radionuclides of interest that can be produced through nuclear fission is

positron nuclear fission

18 F is produced through _____

Lithium carbonate (Li₂CO₃)

What is the target material to produce 18-F

tritium (3/1 H) ; particle accelerators

what is formed with the extraction of 18-F? what do we use instead for production of 18-F?

protons, deuterons (2/1 H), and alpha particles (4/2 He)

charged-particle accelerators are used o accelerate electrically charged particle such as ________ to very high emergies

nuclear reactions ; radionuclides ; netrin activation

during charged-particle accelerators are directed onto a target material these particles trigger ______ that result in the formation of _____ in a manner similar to ______ in a reactor

they have very high energied, typically 10-20 MeV to penetrate the repulsive coulombic forces surrounding the nucleus

What is the difference with accelerator-produced particles?