Flashcards
Non-invasive imaging techniques - 14+20
Cards in this deck (30)
- 1how does an x-ray work?high-energy x-rays pass unimpeded through the soft tissues
can see the CONTRAST between soft and more dense tissue (bone = black) - 2computed tomography (CT scan)?can rotate the x-ray source and the detector
taking images at different points around the body
then reconstruct a slice through the body based on these different points around the body --> projection reconstruction - 3PET?image function
also uses a detector around structure of interest
administer a radioactive isotope into the brain and where that isotope accumulates in the body, radiation will be given off from there
radiolabel sugars (fludeoxyglucose) --> use that to measure where you have high uptake of glucose/activity
the system detects emitted gamma particles when you have antimatter-matter collisons
increased water/blood flow --> increases in emission radiation that can be localised - 4problems with PET?radioactive exposure --> limited to 2 a year
we need endogenous markers - 5why is water targeted in MRI?hydrogen has 1 proton, 1 electron and 0 neutrons
atoms with uneven number of protons and neutrons exhibit nuclear spin --> humans are 70% water - 6what is the lamor frequency?give it a nudge into the system so that you upset and change protons aligned preferentially with the field to be aligned anti-parallel
- 7—water at different gradients resonate at different frequencies --> if energy comes back at a certain frequency we know which side of the body it is from
- 8what do we mean by signal contrast (T1)?RELAXATION
immediately after RF pulse, spins start re-emitting the energy they absorbed to get back to equilibrium
T1 is the measure of the rate of return to equilibrium, some tissues this is fast (fat), others its a slow process (CSF) - 9what is T2?immediately after RF pulse, spins start to notice the presence of their neighbours
the local (microscopic) magnetic fields they experience alters the frequency of the protons--> they are said to DEPHASE
fat = lose energy faster than CSF - 10what does fMRI measureassess regional activity within the brain
relies on blood flow changes which are coupled to neuronal activity --> indirect surrogate measure - 11Blood Oxygenation Level Dependent (BOLD) how does it work?haemoglobin acts as an endogenous intravascular contrast agent
as the level of oxygenation changes, so too does the contrast in the images - 12difference between deoxyhaemoglobin and oxyhaemoglobin?deoxyhaemoglobin - paramagnetic --> magnetic properties are likely to be different to surrounding tissue and distort the magnetic field
oxyhaemoglobin - DIAMAGNETIC --> same magnetic properties as the surrounding tissues --> less distortions - 13increased neuronal firing leads to what?increase in oxyhameoglobin --> less distortion of magnetic fields
SIGNAL INCREASES - 14what is voxel based morphometry measuring?study of the size and shape of the brain and its structures
co-register them to a 'template' or 'standard' brain --> clinical investigation of mild cognitive impairment vs depression
use prior knowledge to determine the amount of grey matter, white matter and CSF (segmentation) in each voxel
COMPARE THE AMOUNTS BETWEEN SUBJECTS/PATIENTS/GROUPS - 15how does diffusion-weighted MRI work?use diffusion of water molecules to generate contrast in MRI images
it allows the mapping of the diffusion process of molecules, mainly water, in biological tissues in vivo and non-invasively
molecular diffusion in tissues is not free, but reflects interactions with many obstacles, such as macromolecules, fibres and membranes
WATER MOLECULE DIFFUSION PATTERNS CAN THEREFORE REVEAL MICROSCOPIC DETAILS ABOUT TISSUE ARCHITECTURE EITHER NORMAL OR IN A DISEASED STATE - 16what is the insula?island of grey matter that sits beneath the parietal operculum --> portion of cerebral cortex
if people lose their somatosensory cortex (the homunculus), they are still able to perceive pain
must mean there are parallel redundant systems available - 17if epileptic patients had seizures that were painful, where would be the affected focus of the seziure?the insula
- 18what happens when you stimulate the insula medially?sensation is referred to the lower limb on the contralateral side
stimulate laterally, referred to the upper limb - 192 converging lines of evidence from the insula stimulation studies?1) saw core insulation somatotopy with face, foot and hand
2) stimulate these regions, the referred sensations patients reported were on the contralateral body side in the area you would expect
must be some connection between the referred sensation and a specific area of the posterior insula that we were stimulating - 20when you apply capsaicin to the leg and measure how painful over a 4h period, what is the activity in the posterior insula like?tracks nicely onto the 'waxing and waning' of pain
measure blood flow over the whole brain and ask which areas track the increase in perceived pain - 21what part of the insula does all of the tracking?dorsal posterior insula contralateral to the side of stimulation
- 22what are the conclusions about the insula?1) area that is somatotopically organised
2) stimulate there --> referred sensations contralateral side
3) tracks pain perception - 23when you inject a viral anterograde transporter into the spino-thalamic tract, what happens?project mainly to the insula
relatively little staining at the primary somatosensory cortex
evidence to suggest something is going on in the insula - 24what cortical reorganisation was apparent in patients with chronic back pain?pain evoked potentials are linearly related to the chronicity of patient's back pain
cortical reorganisation was referred to different areas of the brain - 25what morphological changes occur in chronic lower back pain?structural MRI showed grey matter cerebrum volume reduction by 5.4% compared to controls
having CLBP is analogous to an extra 10-20 years of age related change - 26what happens to brain volume and grey matter over the course of a lifetime?not a linear relationship but at 50 things begin to decline
- 27is there a correlation of duration of back pain and amount of grey matter loss?YES
increases in brain stem and reductions in the thalamus - 28what happens before and after hip replacements in patients with hip osteoarthritis?run out 'singing and dancing'
pain source has been removed
MRI before showed grey matter loss in insula, cingulate and S2 compared to healthy controls
compare with post-op scans--> subsequent increase in GREY MATTER (recovery and shows it is reversible) - 29what could this GM be due to however?increase could be due to increased mental stimulation now that they are able to go outside and interact with friends
- 30conclusion from distraction analgesia?thermal stimulation on left forearm at low and high temp --> concurrent distraction task (rapid serial visual representation (hard or easy= high distraction/low distraction)
1) irrespective of thermal input, during the high distraction condition (hard task), PAG and RVM activity is INCREASED
2) this increase is mirrored by an ipsilateral DECREASE of spinal activity within the corresponding pain neurons i.e. less pain gets through when you're DISTRACTED
3) mediated by projections from RVM that either directly inhibit projection neurons, inhibit transmitter release from primary afferents, excite inhibitory interneurons or inhibit excitatory interneurons --> WE DONT KNOW
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- Neuroscience of Pain Flashcards on Non-invasive imaging techniques - 14+20, created by William Chapman on 11/05/2017.
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