topic 5

Question 1

what are the two types of adverse effects of radiation exposure

Answer 1

deterministic, stochastic

Question 2

what is deterministic effect

Answer 2

-below a threshold, there is no effect
above treshold, the severity of effect is dose-related.
eg. radiation-induced cataracts

fyi eg of trshold: number of cells to be damagd before effect occurs
(must exceed this treshold the see the effect)

Question 3

what is stochastic effects

Answer 3

no treshold, severity og effect is independednt of dose (doesnt not affect)
eg. radation induced cancer.

(can occur at any radiation dose)

Question 4

what is mpd

Answer 4

maximum permissible dose: maximum amount of absorbed radiation that can be delivered to an individual and still be considered safe (effect of low dose is not certain)

Question 5

practical conseration to reduce exposure to radiation

Answer 5

TPDS

time: related to the number of retake views needed, can me minimised by using sedation for patients, making sure personnel are familiar with equipment operation

proper use and care for radiation equiptment/sheilding : sheilds/ppe: lead-impregenated gowns, gloves, thyroid glove
consideration: Lead gowns and aprons protect
against scattered radiation,
should never be placed in the
primary beam (can still penetrate into and reach hand)
proper care: no folding/creasing-> cause cracking/seperation of protective layering

distance: doubling the distance reduced exposure by factor of 4, use of sandbags, chemical restrain to reduce the need to stay in the room

skilled in positioning and machine operation: minimise the need for repeat studies

Question 6

PPE

Answer 6

-lead gown
-thyroid guard
-lead-filled gloves
-radiation exposure monitoring (dosimeter)

Question 7

other safety consideration when setting up/ during radiogrpah

Answer 7

-be careful when positioning: pain/unconfortable (where they are injured) -> result in injuries to patient or handler, may need sedation, but not always possible

have a game plan so that everything can be done swiftly
-restrain tools: rope, v troph, sand bags
-which views, which part of body
-anesthetic machine (if needed)

Question 8

compare between digital and analog receiver

Answer 8

digital: electronic measurement of pattern of x ray transmision-> converted into computer files and viewed on computer

analog: using film that needs to be developed-> can be time consuming and has potential for artifects

Question 9

how is an x ray formed/generated

Answer 9

-generated using an x ray tube, a vaccum sealed cylinder consisting of anode (+ charged) and cathode. (- charged). x rays are produed when the high speed electrons from the filament hits the target

patient lies between the x ray tube and the recorder
beam shaping collimator configers the shape and size of the x ray beam needed for the part being radiographed

degree of film blackness is affected by number (mAs) and energy of x rays (kVp) stricking the film

when film is exposed to x rays, silver halide crystals precipitate during the developement of the film

exposed areas of the film appear black (not absorbed by the patient, just passes through)

unexposed areas appear white (absorbed by the patient-> few/less x rays strike the receiver)

in between, many shades of gray

Question 10

opacities of the different structures/tissues in the body

Answer 10

-has opacity (least opaque on film) (appears black)
-fat
-soft tissue
-bone
-metal (appears white)

Question 11

what are the different exposure factors

Answer 11

kVp: strength/power of photons. controls the penetration ability of x ray photons
(increase kvp-> x ray photons can penetrate deeper into the body-> will produce blacker images with low contrast (difficult to see varioation in colour)
used for tissues that are thick (fatter animal)

mAs:number of x ray photons produced by x ray tube
measure of radiation produced over a set amount of time (s)
increase MAs-> increase number of photons produced

time
measured in s
usually combines with mVp
controls the amount of time the x rays are produced for

Film focal distance
disance between source of x rays and the image receptor, also affect the intensity of the image produced

Question 12

what happens when kVp is increased

Answer 12

increase kVp, higher voltage difference between the filament and the target bc electrons travels faster form filament to target-> greater the enrgy of x rays produced

x ray energy increase-> increase penetration of x rays into patient

increase kVp can also increase the number of x rays slightly, but not the main effect

Question 13

what are the different restrain and their harms and benefits

Answer 13

chemical restrian: sedation:
reasons: reduce anxiety, pain
so that patient remains still during radiographic exposures-> fewer retakes of the same area of interest-> lower radiation doses (exposure)
reduces the risk of inhuries (to patient and handler)
consideration: monitor closely

manual restrain: reason:not clinically stable for chemical restrain
will require more people to retrain patient: to prevent patient from jumping off table
tp prevent injuries (patient and personnel)
up to 3 people for fracious/ big animals
consideration: anyone in the room during exposure will need to wear full ppe
can use mechanical restrain such as v troph, sandbags, rope to restain patient

Question 14

importance of collimating

Answer 14

Beam collimator = device in the x-ray
tube housing that narrows a beam of
particles/waves
 Reduce size of x-ray beam and patient
dose of x-rays (only chose part will receive tej primary beams)
 Reduces scatter radiation that may cause
fogging of the image and reduces
exposure of personnel to radiation

Question 15

why need to take more than 1 view for x ray study

Answer 15

body is being studies is 3D, i view can cause details to be missed

Question 16

positioning for chest x rays

Answer 16

-from last rib to neck, thoracic inlet area
-pull the frond limbs forward

Question 17

when is a thoracic x ray done (indication)

Answer 17

-when patient is coughing
-cardovascular disease
-following trauma

Question 18

what views are taken for a complete chest x ray

Answer 18

-right lateral view
-left lateral view
-ventraldorsal view

Question 19

how to position patient in lateral view

Answer 19

-patient lying on L/R (lateral recumbency)
-thoracic limbs should be extended evenly and cranially, preventing elbows and triceps from superimposing (overlaping)
-neck in natural position to prevent misinterpretation of trachea
-may need to use foam wedges under sternum to ensure sternum and vertebrae are levelled with each other ( for clear, accurate image)
- use side label

Question 20

how to postion patient in DV

Answer 20

-patient is in dorsal recumbency
-use v troph to keep patients spine and sternum are alligned
-thoracic limbs are pulled evenly, cranially and secured (sand bag, rope)

Question 21

how to position patient in DV

Answer 21

reason: patient in respiratory distress
so that ribcage can expand fully (compared to DV)
-position elbow away from thorax
-extend the neck allowing for undisturbed airflow through trachea

Question 22

indication for abdominal x ray

Answer 22

-urinary/ gastrointestinal issues
-abdominal pain
-enlargement of abdominal organs
-vomitting, dairrhoea

Question 23

postioning for abdominal x ray

Answer 23

2cm infront of the end of the sternum to hip joint
-pull back legs back

Question 24

what views are needed for abdominal x ray

Answer 24

L/R lateral view
ventral dorsal view

Question 25

postioning for lateral view

Answer 25

-patient in lateral recumbency -place L/R label

Question 26

postioning for VD view

Answer 26

-patient is in dorsall recumbency -use v troph to ensure sternum and spine is allignmed and superimposal -extend the back legs

Question 27

safety considerations when taking x rays

Answer 27

-PPE wear the correct way -wear dosimeter -rotate personnel -turn on the red warm=ning lgiht (prevent people from coming in exposing everyone to radiation) -turn of lights before taking - if no need to be in room, be out -collimate

Question 28

purpose and example of contrast radiography

Answer 28

-to obtain clearer view of certain structures, can be masked, radiotranslucent (appear black on radiograph/ x ray image example: positve contrast: barium, can be mixed with water/ food, for GI tract study/monitoring/spot for foreign body consideration: caculate and give the correct dose note time of administration (record in radiograph what time it was taken) spill on coat whipe off administer away from radiograph to prevent contrast medium from spilling onto table (can affect future x rays) use disposable gloves/apron when administering-> orevent the contrast to be transferred to radiograph equiptment

Question 29

fluoroscopy

Answer 29

motion x ray: Motion x-ray”  Produces ‘live’ video format images by compiling a series of radiographic images  Used to visualize dynamic processes in real time  Gastrointestinal motility  Blood and urine flow  Collapsing trachea  Swallowing  Standard x-ray tube  real-time image  Inverted radiograph – radioopaque and radiolucent areas are flipped  Contrast agents may be used to enhance area of interest -  High exposure to radiation Icontinuois release to produce series of image)

Question 30

differnce between fluroscopy and CT

Answer 30

Animal does not need to be immobilised in fluoroscopy, but needs to be immobilised in CT (sedation or general anaesthesia)

Question 31

endoscopy

Answer 31

Visual access to inside of the body and provide high quality magnified images of tissues and organ systems adv  Foreign bodies can be removed  Tissue samples and biopies taken  Procedures are carried out through tiny incision resulting in less tissue trama Type of Endoscopy  Rigid Endoscopy  Flexible Endoscopy

Question 32

parameters of sound waves

Answer 32

* Frequency – number of times a wave is repeated per second (hertz, Hz) * Wavelength – distance traveled by a sound wave in one cycle * Velocity – rate at which the sound travels through a medium (body) The higher the frequency, the shorter the wavelength (think, the faster they

Question 33

what is acoustic impedance of tissue

Answer 33

Acoustic impedance of tissue * Product of the tissue’s physical density and sound velocity within the tissue (distance sound can travel in one cycle) (resistance of tissue to sound) * Change in acoustic impedance from one tissue to another determine how much of the sound wave is reflected and how much is transmitted into the second tissue (change is acoustic impedence, think how only some of the soundwaves are able to pass through the rest cannot so it reflected) large difference in acoustic impedance between two tissues, almost all the sound is reflected in echo

Question 34

importance of acoustic coupling gel

Answer 34

without it, the gas trapped between the skin and transducer prevents imaging because of reflection of all the sound (difference in acoustic impedance between the the air and skin-> soundwaves will be immediately reflected back in echo) important to shave the area, will interfere

Question 35

what is attenuation

Answer 35

ultrasound beam is attenuated ( loses its strength) as it travels through the medium determined by distance travelled and frequency of soundwaves

Question 36

four components of attenuation (three ways that ultrasound beam loses its strength

Answer 36

absorbtion (soundwaves absorbed into tissues) reflection ( sound wave encounters tissue interfaces of different acoustic inpendance-> reflection is generated) -> returin to transducer-> image formation scattering: soundwaves encounter small irregular surface, dont go back to transducer ) refraction: (difference between incident angle and refelcted angle -> not transmitted to transducers)

Question 37

what is transducer

Answer 37

device that convert electrical currents to sound waves forming the image: convert sound waves into electrical currents selection of ultrasound tranducer depend on physical properties and characteristics (determined by vet)

Question 38

what are the two basic shapes of ultrasonic imagins

Answer 38

Sector/pie (curved array transducer)  Rectangular (linear transducer)

Question 39

rls between resolution and soundwave frequency

Answer 39

soundwave frequency: number of times a wave is repeated per s frequency increase, resolution increase, but unable to penetrate deeper strucutres frequency decrease, resolutuion decrease, poorer resolution think: sound wave frequency: how fast it take to repeat cycyle, higer frequency, cycle repeated faster and in order to do that distance of cycle must be shorter and nearer )

Question 40

how ultrasonicimage is porduced

Answer 40

A small burst of sound waves is sent into the body by a transducer, and the transducer becomes an echo receiver  The transducer receives returning echoes and generate electric currents  form the image can be used to calculate the distance between reflector and transducer

Question 41

image interpretation

Answer 41

Echogenicity  Relative brightness of a structure  Anechoic structures have no echoes  appear black  Darker structures are hypoechoic (great fifference between acoustic impedance of tissue)  Brighter structures are hyperechoic  Important to know normal relative echogenicity of organs (for identification and looking at health)

Question 42

sonopgrapher to know what about before doing ultrasound

Answer 42

type and size of transducers how to use the available ultrasound controls

Question 43

examples of panel control

Answer 43

power control: intensity of sound output by the transducer gain control: affects aplification of returing echos in the receiver - changes the brightness of all teh echos on the monitor# Time-gain compensation control  Adjusts the amplification of returning echoes at various depths  Echoes returning from deeper tissues are weaker than echoes returning from tissues closer to the transducer  Amplification of echoes from deeper tissues make the image more uniform in brightness  Depth: controls the depth of the image display  Place the structure of interest in the middle of the monitor to optimize its visualization

Question 44

our job in ultrasound study

Answer 44

Aids for positioning of the animal  Clippers + cleaning site with alcohol + coupling gel  Air is a barrier to the propagation of sound waves  Need good contact with skin  +/- sedation (agression)

Question 45

use of ultrasound

Answer 45

Not helpful for gas-filled or bony tissues  Sound beam is totally reflected at the soft tissue/gas interface and absorbed at the soft tissue/bone interface  Gas and bone also “shadow” organs beyond them  Bowel gas can inhibit imaging of adjacent abdominal organs  Useful to evaluate  Most soft tissues – muscles, abdominal organs  Heart (echocardiography)