Skylar's Intro Exam 2

Two Types of Ionizing Energy

1. human-made
-medical/dental
-x-ray
2.background
-radium/uranium
-sun
-cosmic

risk must weigh _______ than __________

less
benefit

what kind of effect can radiation cause

biologic

conditions necessary for x-ray production

1. a source of electrons
2. a means to rapidly accelerate the electrons
3. something to rapidly stop this movement

all of this is done by the tube

x-ray tube is a __________ tube

diode
-glass envelope maintains vacuum

is the beam heterogenous and homogenous

heterogenous

how is the energy of the beam expressed?

KeV

source of electrons

mA

high speed motions

potential difference (KvP)

does muscle or fat need a higher KvP

muscle

does bone or muscle need higher KvP

bone

deceleration

target
-anode

anode

positive end

cathode

negative end

thermonic emission

the release of electrons from the tungsten filament when the electrical current passes through it and heats the filament

when is the x-ray produced?

when it strikes the anode

what is the x-ray

the primary beam

what are the 3 paths of the x-ray beam

1. can be absorbed
2. transfer energy and scatter
3. pass through unaffected

Classic Coherent Scattering

no energy transfer

Photoelectric Interaction

greatest hazard to patient
complete energy absorbed

Compton Interaction

greatest hazard to worker
scatters in random direction until energy is gone

Pair Production Interaction

radiation therapy
high energy photon

Photodisintegration

nuclear energy

Roentgen

Coulomb per Kg
Air

Radiation Absorbed Dose

Gray
RAD energy absorbed

Radiation Equivalent Man

Sievert
REM
different types of biologic effects

Curie

Becquerel
activity of radioactive
-nuclear med and radiation therapy

Standards

FDA
ALARA

The annual dose limit for occupationally exposed individuals is valid for

50 mSv (5 REM)

annual dose for public

5 mSv (0.5 REM)

monthly dose for embryo-fetus

0.5 mSv (0.05 REM)

dose for lens of eye

15 msV
-can get cataracts

2 class of radiation

1. nonionizing
2.ionizing

examples of nonionizing

-radio waves
-micro
-infrared
-visible

examples of ionizing

-moving electrons
-ultraviolet
-x-ray/gamma
-alpha particles
-beta particles
-protons
-neutrons

lead apron requirement

0.5mm

thyroid shield requirment

0.5mm

lead gloves

.25-0.5mm

lead eye glasses

.35-.5mm

does the dosimeter protect you from radiation?

no

Radiation Syndromes

bone marrow
GI
Central Nervous

True or False: Any extraneous information on an image that does not reflect the patient's true medical condition detracts from diagnostic efficacy

True

diagnostic efficacy

The degree to which the diagnostic study accurately reveals the presence or absence of disease in the patient

should you mask an image

no

PBL

positive beam limitation
automatically reduces collimation to IR levels

Tabletop is highly radiolucent

little absorption
can penetrate

radiolucent high or low absorption?

low

radiopaque high or low absorption?

high

IR Technology

receives remnant radiation from patient and captures x-ray energy for processing

Classes of Diagnostic Imaging

1. Film-screen radiography
2.Flouroscopic imaging
3.Digital/computerized imaging

penetrating ability and quality

KvP

the only radiation that has any clinical value is...

- the radiation that is absorbed in the detector
- able to be converted to a radiographic
image for interpretation

latent image

invisible image created after exposure but before processing

cord attached to IR

tether

static radiographic image

SPOT film

X-ray production requirements

vacuum tube
source of electrons
high voltage
target

vacuum

removes all of the air so gas will not interfere with the production of x-ray

what is a primary factor of density?

mAs

Label the x ray tube

increase kVp

lowers contrast

images few grey tones

short scale (high contrast)
seeing black and white

images many grey tones

long scale (low scale contrast)

Direct Square Law

increase distance
increase technique

Inverse Square Law

decrease distance by 1/2
increase intensity by 4x
OR
increase distance by 2x
decrease distance by 1/4

Classes of Radiation

Primary radiation
Scatter radiation
Absorbed radiation
Remnant radiation

attenuation

absorption of radiation in the body
loss of radiation energy as result of passing through an absorbing material

high attenuation

radiopaque

low attenuation

radiolucent

scatter control

occupational worker receives their dose from
retracts from image quality
can create fog

fog

exposed IR

how to control scatter

lead blocker on side of patient

IR

detect remnant radiation from patient and convert it into chemical or electrical charges

digital receptor systems (DR)

computerized radiography
cassette
exposed plate and ran through reader with latent image

Computed Radiography (CR)

exposure to plate

Exposure Index

a numeric representation of total x-ray exposure to the receptor
differs among manufacturers

geometric qualities of image

affects resolution, size, and shape of image

what controls size of image

SID and OID

What can affect the detail

motion
unsharpness
focal spot size
SID
OID
distortion

what is the most common cause of image unsharpness

motion
voluntary or involuntary

unsharpness

loss of resolution

OID

patient and image receptor

distortion

any misrepresentation of patient's true size and shape

size distortion

image always slightly larger than objects actual size
can use longer SID or minimize OID

shape distortions

Central Ray (angling)
Patients' anatomy (rotation)
IR

deliberate distoration

angling tube on purpose

density

mAs

contrast

kVp