An intro to Medical Imaging

Question 1

transverse plane

Answer 1

magician cut i half legs separated from top

Question 2

coronal plane

Answer 2

crown cut separate bac of head from face

Question 3

sagittal plane

Answer 3

90 degrees to coronal

Question 4

How do x-rays give an image?

Answer 4

Focus the beam of high energy electronsthey pass through the body onto the receiver some are absorbed or scattered (attenuation)depends upon density and atomic number (metals)

Question 5

Attenuation

Answer 5

how much you attenuate the x ray depends on the density and atomic number more dense/ higher atomic number = more attenuation= lighter appearance

Question 6

Advantages of x ray

Answer 6

quick simplecheap portable

Question 7

disadv of x ray

Answer 7

radiation but low one plane so 2Dwould not see all pathology cant visualise all areas poor soft tissue imaging

Question 8

uses of x ray

Answer 8

chest- infection, pneumothroax, trauma, effusion, oedema bowel- dilatation, perforation orthopaedic- fracturepost procedure- nasogastric tube pacemaker PICCdentist

Question 9

What contrast is used in fluoroscopy?

Answer 9

barium, iodine or gadolinium (MRI) - Strongly absorb x-rays - dense white -any space it can be swallow, inserted or injected

Question 10

uses of fluroscopy

Answer 10

angiography contrast GI studies therapeutic joint injections
arthrograms screening in theatre

Question 11

adv of fluroscopy

Answer 11

dynamic studies cheap interventional procedures

Question 12

disadv of fluroscopy

Answer 12

clinical exposure must be minimised radiation

Question 13

CT

Answer 13

computerised tomography

Question 14

How does CT work?

Answer 14

rotating gantry-x-ray on one side -detectors on the other images put together by computer attentuation- higher atomic number- more attentuation-lighter image

Question 15

Hounsfield units

Answer 15

less dense= negative
fat air black more dense= positive
bone metal water = 0

Question 16

Looking at CT scans

Answer 16

looking from feet upleft side of image= right side of body

spine is posterior

Question 17

What is on the right side of the body?

Answer 17

liver kidney appendix gallbladder

Question 18

What is on the left side?

Answer 18

spleen kidney

Question 19

Adv of CT

Answer 19

QUICK good spatial resolution can scan most spaces

Question 20

disadv of CT

Answer 20

radtiation lower contrast resolution- harder to distinguish between different densities affected by artefactsrequires breath holding overuse fishing for diagnosis incidental findings

Question 21

How does an MRI work?

Answer 21

strong magnetic field aligns hydrogen atoms some point towards head some towards feet not all unmatched ions remain radio frequency pulse applied unmatched ions absorb energy and spin in opposite direction pulse is turned off and atoms spin returns which emits energy computer processing to generate image

Question 22

adv of MRI

Answer 22

no radiationgood contrast resolution - can distinguish between densities easily

Question 23

disadv of MRI

Answer 23

expensive 
time consuming
availibility
claustrophobic 
some patients wont fit 
loud
need to stay still metalwork

Question 24

scintigraphy

Answer 24

injections of radiopharmaceuticals emmit gamma rays highly sensitive functional and anatomical info

Question 25

how does Position emmision tomography work?

Answer 25

pet scan radio nucleotides that decay by position emmision bound to glucose pet scan camera detects annihilation (high energy gamma rays) -more annihilations the bigger the signal-tend to be combined with CT/MRI'hot spots'- areas that highly metabolic reactive- glucose- these show up very bright usually used in oncology as cancer cells are very metabolically active

Question 26

Ultrasound

Answer 26

high frequency sound waves from transducer probethis sound wave is reflected by tissues where density (impedance) differs probe detects sound waves this creates an electrical signal-determines the distance- time taken to come back-determines impedance- proportion of reflected waves

Question 27

What is acoustic impedance?

Answer 27

an area where the density of tissues changes is where a lot of waves are reflected back

Question 28

What is acoustic shadowing?

Answer 28

great difference in tissue density means sound is completely reflected therefore cant see behind bone, air and stone

Question 29

what is hyperechoic

Answer 29

More reflectivewhite

Question 30

what is hypoechoic

Answer 30

less reflective dark grey

Question 31

anechoic

Answer 31

not reflective black- pure fluid

Question 32

adv of ultrasound

Answer 32

lack of ionising radiationlow cost portablecan be inserted into body cavaties babies dynamic (blood flow)

Question 33

disadv of Ultrasound

Answer 33

operant dependant no bone or gas penetration body habitus

Question 34

What are the ideal conditions for contrast media?

Answer 34

low osmolality and viscosity high water solubility biologically inert safeheat and chemically stablecost effective 95% glomerular filtrationtubular excretion and protein binding negligible half life: 30-60 minsyour kidneys need to be functional to allow the drug to be excreted

Question 35

What is an idiosyncratic reaction?

Answer 35

not predictable and rare