Part V Flashcards
fissionable material usually in the core of NR:
Natural Uranium 235; U-238
NF of U235
spontaneous NF (7x10^8), splitting into two0 lighter nuclear fragments and emit 2 or 3 neutrons in the process
3 components of NR
fuel cells
moderator
control rods
contain fissionable material are surrounded by a moderator material
Fuel Cells
purpose is to slow down rather energetic fission neutrons
moderator
more efficient initiators of additional fission events
slow neutrons (aka thermal neutrons)
commonly used moderator
“heavy water”, (containing deuterium) and Graphite
positioned to either expose or shield the fuel cells from one another - ABSORB EXCESS NEUTRONS
control rods
composition of control rods and reason
Cadmium or Boron - strong neutron absorbers but do not undergo nuclear fission themselves
“Runaway” Reaction & possible meltdown of reactor core
if control rods were removed, each fission event would stimulate more that one additional nuclear fission
NR produced RN charac:
-neutrons are + = beta emission
-(n, g) reaction - not carrier free
-small target of nuclei activated = v. low specific a.
used to accelerate electrically charged subnuclear particles such as PROTONS, DEUTRONS, TRITONS and ALPHA p. to v. high energies
charged particle accelerators
Some NR RNs:
N14 (n,p) C14
Na23 (n,g) Na24
P31 (n,g) P32
Cyclotron Process
- has semi-circular Dees
- Ion source - middle (p) accelerated to v. high energy
- electric shield on ends of middle to contain ef
- circular motion bc of mf
- p gain energy every time it cross the gap
6.accelerated p hits target creating neutron and desired daughter RN
Cylotron produced RN charac:
- charge added to nucleus = EC & beta + emission
- added + charge change Z = carrier free products
- smaller quantities
-expensive
consists of p-d rn contained in an apparatus that permits separation or extraction of d from p
RN Generator
most important generator
Mo-99 -Tc 99m
y rad emitted by Tc 99 favorable by anger camera
140 keV
Mo 99 column, eluant
alumina column, 5-25 ml normal saline
available Tc99m extracted in a single elution
75-85%
causes radioactivity
imbalance no. of N and Z - Natural RN
excitation due to bombardment of particles - Artificial RN
R. material experience an exponential decay
-DR is the no. of disintegrations occurring each sec
Activity
typical Act values in NM
0.1-30 mCi = dx
up to 300 mCI = therapy
total no. or nuclear transformations in an organ or tissue
-values are often diff. for healthy and pts with disease
cumulative activity
cumulative activity of Tc99m
5.2 x 10 ^6 Ci/g
time taken for no. of radioactive atoms to decay by half
half life
most important h
effective half life
EFH depends on the:
RP
Organ Involved
Patient Variations
Health State of Organ
Preferred rn gamma energy released
50-300 keV
reason for 50-300 keV
high enuf to exit the pt but low enuf to be collimated and measured
reason for mono-energetic y rays
range of PHA is based on energy emitted by RN
produce y rad via EC
it will happen if nucleus is still unstable even if it has already captured e
cyclotron rns are [..] and thus, decay by [..] or [..]
neutron poor
b+
EC
neutrons bombard unstable target nuclei
NF
neutrons bombard stable target nuclei
NA
production of Tc99m
- NF - 235 U -> Mo
- Mo in compound (ammonium molybdenate) loaded to column = inorganic alumina resin
- Adsorption -Mo attaches to alumina molec
;Mo bond with alumina, Tc does not - Elution - 99 Mo decays to 99m Tc; eluant -isotonic saline (flush generator - separate d)
- Mo 99 not soluble to saline, Tc99m soluble-extracted
- Eluted once daily for 1 wk then replaced; Mo -66 hrs
technique mainly used for separation of p-d rn
chemical technique - Column Chromatography
types of generators
dry types
wet type
other name for dry type
manufacturer’s method/type
separate container of saline solution that is changed every time a new elution will be made. manual inject saline solution
dry type
it has a built-in container with enough volume of saline solution for all elutions
wet type
activity of d at elution depends on the:
- act of parent
- rate of formation of d = to rate of decay of p
- time since last elution
- elution efficiency (80 to 90%)
Ibritumomab tiuxetan (zevalin) / (bexxar) therapy
non-hodgkin’s lymphoma
