Diagnostic Imaging (Radiology) Exam 1 (MSU VMT)

1895

When were x-rays discovered?

Wilhem Conrad Roentgen

-discovered x-rays in 1895

-successfully took radiograph of wife's hand using x-ray tube

-received the first Nobel Prize in physics for his discovery in 1901

x-ray

-energy

-considered form of electromagnetic radiation

-travel in straight lines but may change direction

-composed of energy (quanta) bundles called photons carried along by wave

electromagnetic radiation

-method of transporting energy through space

-distinguished by wavelength, frequency, and energy

-how energy passes through space and matter

wavelength

-distance between two consecutive points

-measured in nanometers

Frequency

-number of wave cycles that pass a single stationary point per second

-measured in Hz

high frequency

shorter wavelength=

shorter wavelength

greater energy=

greater energy

more penetrating power=

xrays result

fast moving particles bump into matter

cathode

-negative electrode

-source for x-ray

-contains wire filament made of tungsten thats heated by a low-energy circuit

-heat excited electrons within atoms of the tungsten filament

anode

-postive electrode

-electrons pulled towards bc of their negative charge

-large amount of energy produced when electrons interact with it

-target within the anode that the electrons hit

-draws heat away from target

wire filament is heated

electrons released when

1%

how much energy produced forms electrons?

99%

how much energy is released as heat?

number of electrons produced

-depends on amount of heat applied to the filament

-under control of mAs and time which controls amount of heat applied to filament

Acceleration

controlled by kVp

kilovoltage

the amount of electrical energy being applied to the anode and cathode to accelerate the electrons from the cathode to the anode

kVp

-determines the penetrating power of the x-ray beams

focal spot

-area on the anode that the electrons hit

-size is related to sharpness of image

-the smaller the sharper the image

production of controlled x-ray beam

What is the purpose of the x-ray tube?

SID (source to image distance)

-distance from the x-ray source (anode target) to the film

-generally 36 to 40 inches

Object-Film Distance

-the distance between object being imaged and the film

radiographic density

-the degree of blackness on a radiograph

-refers to the number of x-rays that the film had been exposed to in a given areas

-the blacker the film the more x-rays that touched it

radiographic contrast

-the difference in radiographic density between tow adjacent areas on the radiograph

-bone vs. soft tissue

tube stand

-supports x-ray tube

-models can vary from tabletop stands to large stands mounted on the celing

collimotor

-most versatile type contains lead shutters

-light source helps the radiograph tech view the x ray field size type

-light also helps to accurately position the patient

-use smallest field size necessary to obtain diagnostic image

grid

-purpose is to absorb scatter radiation to improve the quality of the image (prevents fuzziness)

-lives under table top

-essentially a series of lead strips that absorb radiation and spaces to allow x rays to pass through

grid ratio

-height of the lead strips compared to the width of the space between

-height is usually larger and listed first

"bucky"

-place holder for image receptor

-located under the x ray table or vertically in the wall mounted unit

-not recommended for portable units

-provides mobility for different size patients

-contains a built in grid to absorb scatter

-no grid lines on film

As Low As Reasonably Achievable

What does ALARA stand for?

6 ways to achieve ALARA

-dosimetry badges

-PPE and protective equipment

-patient positioning aids

-technique parts

-quality control measures

-emergency procedures

Primary x-ray beam

a body part is placed in the primary beam due to technical error

scatter

-x-rays which strike the object of interest and are bounced in another direction

-cannot be prevented so personnel must use leaded PPE

upper body and head

Which parts of the body are at greatest risk for exposure?

leaking radiation

-produced by older, poorly maintained machines when quality control and assurance programs are not routinely practiced

-damaged portable

3 rules of radiology safety

-shortest time

-greatest distance

-maximum shielding

secondary and scatter

Which radiation is leaded PPE designed to protect against?

25%

How much of the primary beam is absorbed by leaded PPE?

visual inspection

check for visible tears and cracks

every 3 months

How often should manual inspection of PPE be performed?

manual inspection

-external and internal surfaces

-if a defect occurs in main body of leaded PPE the item must be replaced or repaired before further use

-if defect occurs at the edge, the item should be marked and monitored for changes

-take radiographs to evaluate internal surfaces

Cleaning PPE

-never use products containing bleach

-never machine wash or dry clean leaded PPE

apron

-never fold for storage as it results in cracks over time

-hang vertically over a round surface not less than 3 cm in diameter or lay flat for storage

gloves

-store in a way that air can circulate inside them; this eliminates moisture which can build up inside them

-store vertically on holder

dosimeter purpose

measures the amount of radiation exposure (dose) an individual receives over time

dosimeter donts

-NEVER wear your badge outside of designated area

-NEVER expose badges to the path of the direct beam

-NEVER share badges

dosimeters dos

-store badges outside of the radiology room in areas where they are not likely to be exposed to sunlight, heat, or additional radiation sources

-use a separate badge for each site where radiation occurs

pinpoint spikes/defects

Why should you use separate badges for each site where radiation occurs?

personnel safety rules

-minimize number of people in the room when imaging

-rotate personnel regularly

-use leaded shielding if you must be in the room but are not manually restraining the patient

-pregnant workers should not restrain patients for imaging, especially in the first trimester

-fetal dosimeter required if pregnant worker chooses to restrain

-people 18 and under should not be allowed in radiology room during imaging except for medical purpses

collimation

-controls size of the x-ray field

-reduces scatter

-improves the clarity of the image

when restraining

-never look directly into the primary beam with or without goggles

-avoid sitting or leaning on the table when restraining

-always stand at the ends of the table

positioning aides

-minimize the number of people required to provide manual restraint

-sandbags

-v troughts

-foam wedges

-limb ties

technique charts

-predetermined technique settings for an area of interest based on tissue thickness

-uses the minimum amount of radiation to take a diagnostic radiograph

-reduces amount of scatter

patient restraint

-minimizes patient motion

-proper sedation of anesthesia should be provided

-positioning aides

-manual restraint

breeding and pregnant animals

-gonadal shields

-breast shields

-for pregnant animas: x-rays for emergency only

ultrasound

what should be used in place of an x-ray in pregnant animals?

care of x ray tube

-warm up machine and tube prior to use

-take care when operating portable units to prevent damage

-the tungsten filament can be damaged when dropped if you drop the unit

-monitor for oil leaks

oil leaks

-oil absorbs heat from x-ray tube so leaking leads to overheating and imminent destruction

-cracks can result in leakage of radiation in the form of scatter

40 in

what is the preferred SID?

intensity

When distance is changed _________________ is also changed

less intensity

greater distance=

quality control and assurance

-does not guarantee complete radiation safety for patients and staff

-errors in image quality and clarity can still occur even if the machine is functioning properly

-SID

-bucky-grid centering

-light field/xray field alignment

quality assurance

checks personnel for error

quality control

checks machine for error

nine penny test

the 9th penny is placed in the lower left hand corner to provide orientation of the film to check for collimation

anode heel effect

-variation in number of x-rays: intensity of the xrays of the primary x-ray field as they diverge from point of origin

-cannot be prevented

-decrease of intensity occurs as as you move from cathode to anode which causes a decrease in radiographic density causing a poor image quality

poor images

What happens as a result of a greater anode heel effect?

put the thickest part of the patient towards cathode side

how should you position the patient to decrease the anode heel effect?

more intensity

the cathode has more or less intensity than the anode side?

SID effect (on anode heel)

-decreased SID=increased anode heel

-shorter distances cause a greater variation in x-ray intensity

-the higher the SID the less anode heel effect

x-ray field size

the greater the size, the greater the anode heel effect will be

anode angle

-the smaller it is the greater the anode heel effect will be

-smaller focal spot, greater amount of x-rays to pass through anode

magnification

-occurs when the anatomy is not positioned as close to the image receptor as possible

-the anatomy that is further away from the image receptor appears larger than it really is

-alters appearance and causes misdiagnosis or hides pathology

geometric distortion

-position of anatomy in regards to image receptor

-changes radiographic density and contrast

-magnification

-foreshortening

-elongation

foreshortening

-occurs when the anatomy is not positioned as close to the image receptor as possible, and is also not parallel with the image receptor

-can get magnification and thickness changes

technical errors

-patient motion is most common

-results in retake

-use the shortest exposure time possible with sedation or anesthesia when available and appropriate to prevent patient motion

-human anatomy present

-collars, leashes, tags on the patient

-double exposures

-film flogging

-static electricity on the film

-thumbnail crescents

-fingerprints

intentional artifacts

-external fixators, splints, casts are visible on the film

-buckshot

-can't be prevented

-either want it there or unaware it is there

manubrium

What is used as the cranial border when collimating a thoracic x-ray?

xiphoid

What is used as the caudal border when collomating a thoracic x-ray?

sternum

What is used to center a VD x-ray of the thorax?

spine of scapula

What is used to center a thoracic x-ray?

scapula border

What is used as the cranial border in a lateral x-ray of the thorax?

standard thoracic views

-right lateral

-ventrodorsal

standard cardiac views

-ventrodorsal

-dorsoventral

-lateral

standard lung views

-right lateral

-left lateral

-ventrodorsal

DV

Which view is best for the heart?

VD

Which view is best for the lungs?