Medical Imaging Flashcards
what is X-ray useful for visualisng?
what does the picture show?
what are they?
visualise: skeletal system and some diseases in soft tissue
what are?: a picture of the parts of the patients that absorb or block the x-rays
picture: based on density and composition of the structure a proportion of the x-rays will be absorbed (more dense: more absorb - looks whiter, less dense: black- e.g. fat / air)
advantages v disadvantae of plan radiographs / x-rays?
advantage:
- cheap
- readily avail.
disadvantage:
- ionising radiation (damaging e.g. for foetus / genetilia: DNA damage)
- limited range of densities: shades of grey
- 2D representation of 3D object: some tissues obscure view
- soft tissue doesnt show up well
- Not very sensisitve
* chest x-rays *
know this !
how can you take chest x-rays? - which one is standard and why?
antierior -> posterior (AP) view
posterior -> anterior (PA) view. standard x-ray
in AP view: x-rays get distorted and shadowed when going through = get heart shadows
which chest x-ray is this?
how do u know?
PA
- clavicle is in lung field
- ribs are more slanted / curved
- posterior ribs more in show
- smaller heart shadow
which chest x-ray is this?
how can u tell?
AP
- clavicle at top of lung view
- scapula is in lung field
- ribs more horizontal - can see anterior ones more
- heart shadow larger
what is difference between left hemidiaphragm compared to right?
- left hemi-diaphragm is lower slightly c.f. the right (right side is pushed up by liver)
which view for X-ray is used for appendicular skeleton?
AP and lateral views
how are images displayed?
presented as if you in front of the indivudual (face on): left side = right side
what does this show?
situs inversus totalis :s a condition in which the arrangement of the internal organs is a mirror image of normal anatomy.
what does this show?
normal:
carpals havent occified yet in baby’s hand. currently cartilage (just cant see bc not as dense)
what can you see with this/?
line: shows that left side is more dense (whiter)
- heart is further to the left
what are DEXA scans?
used for?
-
two different, low energy x-ray sources; more precise and accurate calculation of density
a) the denser the bone the fewer the x-rays get to detector
b) used for diagnosis of osteoperosis (health condition that weakens bones)
c) can measure BMI and fat (more precise soft tissue measurements)
what are the different types of x-ray contrast media how work?
contrast media
- use air to reduce density of hollow organ soft tissue (esp. GI system): creates negative contrast
- e.g. can see large intestine more
OR
- can make tissue denser: liquid contrast media used are barium and iodine. non-toxic substances that contain elements of high atomic number - increased atomic number
what is method and what does barium sulphate and iodine highlight when used as contrast media?
1. barium sulphate:
- highlight: GI system
- method: swallow barium meal / enema
2. iodine - angiography
highlights: blood vessels
method: injection of iodine
what is a CT scan?
= computerised tomography
- multiple x-ray at different angle to build up cross section of bodies tissues and organs
advan and disadvan of CT scans?
Advantages:
- cross sectional images and other planes can be reconstructed afterwards
- readily available
- well tolerated (not claustrophobic / noisy)
- high contrast bone detail
Disadvantages:
- ionisng radiation higher than x-ray
- metallic artefacts cause loss of detail
- soft tissue surrounded closely by bone difficult to image
- resp. movement artefact
when you see an axial view of CT scan - what is this angle of?
standing at foot of bed and looking up into head
label where you find the diferent chambers of heart from CT scan?
whats wrong with this CT?
sinusitis: full of snot lol in a synouse
whats wrong with this?
no right common iliac artery
describe MRI imaging
- non-ionising radiation
- v high soft tissue contrast
- images acquired in transverse plane (patients lies through)
- structural and functional information
- does not image bone directly - but good for showing inside bone
- get two views: T1: normal anatomical structure and T2: good for pathology - can see water in bone (oedema)
- noisy and claustrophobic
- people can be in room bc isnt ionising
- no metal objects in room -> esp. ferrous.
what is MRI brill for?
soft tissue imaging
explain difference between T1 and T2 MRI scans
occur at same time or different?
what does white scan show in each?
- occur at same time
- T1: normal anatomy
a) in brain: good gray/white matter contrast (fat: white = myelin, yellow = bone marrow etc)
b) white is fat
- T2: pathology.
a) white is fluid (water)
which imaging method can be used for embryos?
MRI
what is the contrast medium for MRI?
which scan does it give more detail in?
gadolinium contrast
- changes relaxation time of H ion spin
- gives more detail in T2
- gadolinium highlights breakdowns of blood brain barrier (normally cant go through them)
describe ultrasound
- uses soundwaves (1-18 megahertz)
- safe during fetal development
- cheap
- readily available: real time imaging
- becoming more common for both diagnostic and therapetutic imagine
- difficult to interpret what is going on, cant say what things are without knowing where are
main use of ultrasound?
diagnostic and therapeutic injections, nerve blocks: can visualise at same time as injection
what is doppler ultrsound?
shows blood flow direction:
- red = towards transducer
- blue = away from transducer
can measure blood flow
