D8 Nuclear medicine Flashcards
define nucleons
number and type of nucleons present
protons and neutrons
stable vs unstable nuclei
balanced forces among nucleons // unbalanced forces
not reactive // radioactive (spontaneously decay - forms more stable nuclei)
what are unstable nuclei called
radionuclides
describe natural radionuclides
- occur in enviro
- include 235U, 3H, 14C
- all elements Z=84 and above = naturally radioactive, no stable naturally occuring isotope
describe induced/artificial radionuclides
- unstable thru procedures, usually bombardment reactions w neutrons/helium nuclei at great speed
- many radionuclides used in nuclear med prod thru this
how are most radionuclides in nuclear med produced
induced/artificial radionuclides
- made unstable usually thru bombardment reactions with neutrons/helium nuclei at great speed
define radioactivity
involves the emission of energy and particles
from the nucleus as
an atom decays
into a more stable form
who discovered radioactivity (initial)
henri becquerel
- photographic plates became fogged close to uranium salts – bc emission
who furthered radioactivity studies
pierre and marie curie
2 types of atomic nuclei
- quarks – makes up neutrons and protons
- antiparticles – equivalent mass but opp charge eg positron
how are quarks arranged
sets of 3
what is a positron
antiparticle of an electron w same pass and positive charge
- when antiparticles and particles collide = mutual destruction
5 possible events during the decay of a radionucleotide into a more stable form
- ejection of a neutron
- ejection of a proton
- conversion of. aneutron to a proton + ejection of beta particle
- conversion of proton to neutron + ejection of positron
- release of gamma rays
what is ejected when a neutron is converted to a proton
beta particle
what is ejected when a proton is converted to a neutron
a positron
results of radionuclide decay 3
- diff types of radiation
- formation of new nuclide
- change in proton number
what is alpha radiation
the ejection of particles from the nucleus that carry a charge of 2+ and have a mass of 4 atomic mss units
alpha radiation is equivalent to a nucleus of ______, can be denoted as ^4 v2 __ or ^4 v2 a
helium
He
emission of an alpha particle causes the mass number of a radionuclide to ____ by __ units and atomic number to ____ by __ units
decrease
4
decrease
2 `
example of alpha decay – uranium to ?
thorium
238 –> 234
92 –> 90
what is beta radiation
conversion of a neutron to a proton with ejection of an electron (beta particle)
OR
converstion of a proton to a neutron with ejection of an positron
beta radiation example tritium –> ?
helium
- emission of a beta particle and a neutrino
what is gamma radiation (γ)
emission of energy as electromagnetic waves (photons)
what is the wavelength of photons
very short!
0.0005-0.1nm
frequencies of gamma radiation
above 10^19 Hz
does gamma radiation involve altered atomic or mass number
NO. it results from energy changes in the nucleus
what does gamma radiation result from
results from energy changes in the nucleus
gamma radiation often accompanies ____________ as the energy of the _________ is ________ during radioactive decay
alpha or beta raditaion
radionuclide
lowered
what usually accompanies alpha or beta radiation
gamma radiation
define nuclear medicine
use of radiation in healthcare practice
define radiotherapy
treatment: destruction of targeted cells (esp for cancer)
define nuclear imaging
diagnosis: providing detailed info about internal organs
advantages of nuclear imaging over x ray 2
can be applied to soft tissues as well as bones
allows internal organ function to be observed from outside the body
diagnostic techniques in nuclear imaging – the process? 2
- attachment of radionuclide (tracer) to biologically active molecule
– called radiopharmaceutical - progress can be traced via gamma rays – using gamma camera
what are radiopharmacueticals
designed to target a part of the body where there may be abnormality/disease
example of radiopharmaceuticals iodine and glucose
iodine is taken up by thyroid gland, glucose taken up by brain
= tracer is attached to these molecules
what do radiopharmacueticals allow for
allows for examination of organs for abnormality
- ‘cold spots’ where isotopes are partially taken up, ‘hot spots’ in excess
2 requriements for tracers
must emit gamma rays w enough energy to escape from the body
must have half-life long enough for the scan to be complete before decaying
3 benefits of technetium-99m as a radiopharmacuetical
- half-life 6hours – active long enough for examination, decays quickly = minimise exposure
- decay = release of gamma rays, low-energy electrons = low radiation dose + can be detected
- artificial element generated in nuclear reactors (molydenum-99 decays)
what is the most commonly used radiopharmaceutical
technetium-99m (80% of all procedures)
define radioactivity
involves the emission of energy and particles from the nucleus as an atom decays into a more stable form
explain ionising effect of radiation
ionising radiation has enough energy to interact with an atom and cause the removal of electrons
forms highly unstable radicals
what is ionisation density
average energy released along a unit length of their track
- alpha,beta,gamma differ in ionisation density
ionisation density of alpha vs gamma
alpha has +2, relatively high mass = HIGH ionisation density
gamma - lower
= same dose, prod radicals more sparsely
why is radioactivity is dangerous to living cells
exposure to emissions = ionisation of biological molecules in cells/water = forms radicals
impact of radioactivity on DNA
double helix structure = can break when ionised = cell death / mutation
what is MRI (magnetic resonance imaging)
application of NMR spec
presence of magnet
radio waves used to generate electronic signal
- decoded by computer = 2/3 D images
does not involve nuclear stuff
what is MRI used for
diagnosing living tissue - hydrogen atoms present in water molcules which make up 70% of body mass
process of positron emission tomography (PET)
radionuclide w positron emitting tracer inserted into body – accumulates in target tissue
positrons combine w electrons = energy released as gamma rays
gamma rays detected by camera
common tracer for PET scanners? what is it bonded to and why does it help with diagnosing cancer
fluorine-18
- bonded to glucose
- uptake of glucose diff in cancer cells than normal cells
what is radionuclide therapy
treatments involving irradiating the area containing the growth, with aims of controlling / eliminating the cancer
why are cancer cells especially succeptible to damage from radiation
cancer cells = normal cells that lose regulatory mechanisms for control of growth and division
rapidly dividing = more sensitive to damage BC ionising effect primarily affects DNA that CONTROLS CELL DIV
side effects of radiotherapy due to?
effects of radiation on surrounding tissue
- causes changes in the DNA of healthy as well as cancerous cells (esp those that divide rapidly like hair follicles)
name some side effects of radiotherapy
- hair loss (usually temporary)
- sterility (more likely near ovaries/testes)
- skin reaction
- fatigue (req rest and hydration)
- nausea (mroe likely near digestive system)
process of EXTERNAL radiotherapy
external source of radiation is directed at site of cancer from radioactive source
- emits gamma rad = penetrates and damages cancer cells
what is usually used in external radiotherapy
cobalt-60
undergoes beta decay into stable product nickel-60
benefits of recent developments in external radiotherapy
greater precision in targeting of ionising radiation
minimum damage to surrounding tissue
(esp useful for brain cancer)
name the 2 recent developments in external radiotherapy
linear accelerator and gamma knife radiosurgery
process of linear accelerator? (recent development in external radiotherapy)
type of particle accelerator – microwave tech used to accelerate electrons
aimed at heavy metal target
prod high energy x rays
precisely directed at tumour
process of gamma knife radiosurgery (recent devt in external radiotherapy)
tiny beams of gamma rad focused on tumour from approx 200 cobalt-60 sources
strong dose at site where beams converge
