Radiation Biology

Final

What does ALARA Stand for?

As Low As Reasonably Achievable

A value of +2 on the risk benefit continuum means what?

beneficial to patient

(-numbers would be of no or little benefit)

What is the largest source of natural environmental radiation?

Radon gas

Natural Background radiation results in an annual dose to the general public of ____.

3 mSv

What is the largest source of man-made radiation?

Diagnostic imaging: 3.2 mSv

Medical imaging accounts for approx. what annual dose to the public each year?

3.2 mSv

atomic number represents

number of protons

atomic mass number represents

Number of protons & neutrons

BERT

Background Equivalent Radiation Time

what procedure has longest BERT?

PET

isotoPe

Element that has same # of protons but different # of neutrons

isotoNe

same # of neutrons but different # of protons

isobAr

same A# but different Z#'s

iSomers

same A# & Z#

Diagnostic Efficacy

degree to which dx study accurately reveals presence/absence of disease in pt

DE achieved by

-Imaging procedure/practice justified by referring physician

-Minimal radiation exposure

-Optimum XRs produced

-Presence/absence of disease revealed

As Z# increases, PE absorption __

increases

2 types of particulate ionizing radiation

1. alpha

2. beta

2 types of ionizing electromagnetic radiation

1. XR

2. gamma

particulate radiation is made up of 2 protons & 2 neutrons that cannot penetrate a piece of paper

alpha

Alpha, gamma and beta radiation are produced through what process?

nuclear disintegration

If Radium Ra 226/88 emits an alpha particle, it will decay to:

radon 222/86

(loss of 2 p & 2 n)

What happens to the atomic # during beta emission with a negatron emission?

increased by 1 (neutron converted to proton)

What happens to the atomic # during beta emission with a positron emission?

decreased by 1 (proton converted to neutron)

What happens to the atomic # & atomic mass # during alpha emission?

atomic # = decreased by 2 (loss of 2 protons)

atomic mass # = decreased by 4 (loss of 2 protons & 2 neutrons)

A Beta particle with a charge of +1 (one unit of positive charge) is called __

positron

If Iodine I 131/53 emits a beta particle what will it decay into?

Xe 131/54

(neutron coverted to proton, increasing Z by 1)

Positrons are also produced during beta decay. What area of radiology are positrons useful?

PET

SI for exposure in air

Gya

SI for absorbed dose

Gyt

SI for effective/occupational dose

Sv

units for radioactivity

Becquerels (Bq) & Curie (Ci)

measuring output of XR rooms is measured in

Gya

compton interactions affect image by

decreasing contrast

KERMA stands for

kinetic energy released in matter

If the half life of Technetium is 6 hrs and we start with 100 mCi how much will be left after 12 hrs?

25 mCi

150 mGy is equal to Gy

.15 Gy

75 mSv is equal to _ uSv

75,000 uSv

35 Gy is equal to mGy

35,000 mGy

5 XR interactions with matter

1) Photoelectric effect

2) Compton's scatter

3) Coherent scatter (Thompson's, Classical, etc.)

4) Pair Production

5) Photodisintegration

In which of the x-ray matter interactions does the photon interact with an inner shell electron and become totally absorbed?

PE

In which of the x-ray matter interactions does the photon interact with an outer shell electron and eject the electron. The photon continues but with less energy and in a different direction?

comptons

From which of the x-ray matter interactions does the radiographer get most of their occupational exposures?

compton

In which of the x-ray matter interactions does the photon interact with the target atom and become excited? The photon continues with the same energy and wavelength as the incident photon but in a different direction.

Coherent, classic, Thompson

In which of the x-ray matter interactions does the photon interact with nucleus? The energy of x-ray photon is converted into 2 electrons, 1 w/ a + charge (positron) & 1 with - charge. When the positron interacts with a free electron, they annihilate each other & release 2 photons with an energy of .51 MeV (511 keV).

pair production

In which of the x-ray matter interactions does the photon become totally absorbed by the nucleus causing the nucleus to become radioactive (emits neutrons, protons, alpha particles, etc.?

photodisintegration

probability of a Compton interaction is largely dependent on

mass density

The incoming photon must have an energy of MeV for photodisintegration to occur

10 Mev

In order for pair production to occur, the incoming photon must have an energy of at least.

1.02 MeV

Classical scattering is most likely to occur with photons that have what energy?

< 10 keV

A 75 keV photon interacts with an oxygen atom. What is energy of photoelectron produced if a photoelectric interaction occurs? The Binding energy of the k shell electron in an oxygen atom is .5 keV.

Ei = EKE + EB

75 = E + .5

E = 74.5 keV

2 major factors affecting probability of PE

1) 1/E^3 (incident photon energy; inversely proportional)

2) Z^3 (proportional to Z#)

2 major factors affecting probability of Compton

1) mass density

2) 1/E (inversely proportional to incident photon energy)

why is compton's independent of Z#?

incident photon interacts w/ outer shell electrons, which have loose binding energy regardless of atomic #

what is the process of emitting energy/particles in attempt to reach stability?

radioactive decay/disintegration

a curie is how many disintegrations per sec?

3.7 x 10^10

what type of XR is produced after most PE & some Compton's events? They are generally low energy & are a form of scatter

secondary characteristic XR

probability of PE is highest when

incident photon energy (Ei) is equal to/slightly higher than electron binding energy

-probability decreases as difference btwn Ei energy & binding energies gets bigger

sources of natural background radiation

1) cosmic

2) terrestrial

3) internally deposited radionuclides

4) radon gas

Sources of man made radiation

1) medical imaging

2) other: watch dials, exit signs, etc.

approx. total dose to population

3.0 (natural) + 3.3 (man-made) = 6.3 mSv

radiation sensitive target molecule

DNA

which endoplasmic reticulum does protein synthesis occur?

rough ER

loss of hair

Epilation

which principal molecule makes up ~1% of cell & provide most of cell's energy for metabolism & short term energy for body?

carbs

principal molecule considered basic building block of cell & made up of amino acids. they function as hormones, enzymes, & antibodies

proteins

2 main types of nucleic acids

DNA & RNA

organelle that collects & repackages moleucles & distributes them to different parts of cell

golgi apparatus

who discovered Ca Tungstate was good intensifying screen & developed fluoroscope?

thomas edison

powerhouse of the cell

mitochondria

basic unit of heredity

gene

smallest unit capable of independent existence

cell

2 major sections of cell

1. nucleus

2. cytoplasm

What regulates flow of substances in/out of cell?

cell membrane

water plays a major role in assisting the body in maintaining:

body temperature

___ is located in nucleus & contains large amount of RNA

nucleolus

2 types of RNA

1) tRNA