Radiography

Question 1

Properties of xrays (7)

Answer 1

no mass
invisible
speed of light
travel in straight line
penetrate all matter
cause fluorescence
ionise atoms

Question 2

Safety measures

Answer 2

Time - minimum time exposure, minimum number of images
Distance - maximum distance from source, chemical restraint
Shielding - PPE

+ Equipment maintenance

Question 3

Radiation Protection Advisor

Answer 3

External to practice

Question 4

Radiation Protection Supervisor

Answer 4

Internal to practice

Question 5

Ionising Radiation

Answer 5

has enough energy to ionise atoms and damage biological tissue

Question 6

Non-ionising Radiation

Answer 6

less energetic - doesn’t cause ionisation

Question 7

Absorbed Dose

Answer 7

Radiation absorbed by an object (Gray, Gy)

Question 8

Equivalent Dose

Answer 8

Absorbed dose x radiation weighing factor

How harmful the radiation is to biological tissues (Sievert, Sv)

Question 9

Effective Dose

Answer 9

Equivalent dose x tissue weighing factor

Radiosensitivity of different organs and risk of stochastic effects (Sievert, SV)

Question 10

Stochastic Effects

Answer 10

Effects which occur with no threshold dose - random probability

Question 11

Deterministic Effects

Answer 11

Occur at a specific dose threshold, with dose dependant severity

Question 12

Direct Damage

Answer 12

Breaks molecular bonds within cells

Question 13

Indirect Damage

Answer 13

Interaction with water leading to creation of free radicals which break cell bonds

Question 14

Photoelectric Absorption

Answer 14

Ejection of inner cell election from a photon which ionises other atoms

important for exposure at low energy

Question 15

Compton Absorption

Answer 15

Ejection of an outer shell election which ionised other atom

Photon diverts in a different direction with less energy - scatter

Question 16

Characteristic Radiation

Answer 16

Radiation produced by photoelectric absorption

Question 17

Bresstahlung Radiation

Answer 17

Braking radiation - scattered radiation

Question 18

Border Obliteration

Answer 18

Difficulty telling apart adjacent tissues with same radiopacity

Question 19

Mass Effect

Answer 19

Displacement of structures due to adjacent space occupying lesions

Question 20

Reduction of Scatter (5)

Answer 20

Collimation - reduced volume of tissue exposed
Compress patient - as above
Film grids - absorb scatter - use at thickness >10cm
Alternative filtration devices
Lead backing to film cassettes - prevents back scatter

Question 21

Grids

Answer 21

> 10cm thickness

parallel lead strips
grid ratio - higher = more absorbed scatter
grid factor = how much exposure factors must be raised to compensate for grid
Contrast improvement ratio = measure of improvement in contrast due to grid

Question 22

Kilovoltage (kV)

Answer 22

Intensity of beam

Question 23

Miliampere-seconds (mAs)

Answer 23

Rate of xray production in tube

Question 24

Quality

Answer 24

Penetrating power of beam - affected by kV

Question 25

Intensity

Answer 25

Amount of radiation in the beam - affected by kV and mAs

Question 26

PCCELA - Pink Camels Collect Extra Large Apples

Answer 26

Positioning Centring Collimation Exposure Labelling artefacts

Question 27

Right lateral

Answer 27

y shaped diaphragm crura more consistent cardiac silhouette lees of lung field obstructed by diaphragm

Question 28

Left lateral

Answer 28

parallel lung crura

Question 29

Dorsoventral

Answer 29

Single smooth hump diaphragm Heart more cranial and left

Question 30

Ventrodorsal

Answer 30

3 diaphragm humps

Question 31

Clock face to locate part of heart affected

Answer 31

Aortic arch - 12 o'clock Main pulmonary trunk - 1 Left auricle - 2 Left ventricle - 4 Right ventricle - 7 Right atrium - 10

Question 32

Normal Heart Size

Answer 32

Lateral - height - 2/3 thorax - width - 2.5-3.5 intercostal spaces DV - max 2/3 width of thorax

Question 33

Vertebral Heart Score

Answer 33

VHS = length + width (in intervertebral spaces) Dog - 8.5-10.5 Cat - 7.5

Question 34

Causes of enlarged heart (5)

Answer 34

pericardial effusion - gross enlargement, globoid shape mitral valve disease - left side atrial enlargement, straightening of caudal margin, trachea displacement right atrial enlargement - cranial enlargement right ventricular enlargement - increased sternal contact in lateral view enlarged vessels - bulge at point of entry

Question 35

Difficulties in interpretation (5)

Answer 35

atelectasis - effect of crushing dependant lung in lateral breed differences age - thymus nodules - easily mixed up with end on blood vessels skin folds - can look like pneumothorax