Visualisation of human brain structure and activity

  • Created by: molg
  • Created on: 19-05-18 11:03
X-rays
low level radiation to produce an image of the body on film
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Radiographic material densities
Air-fat-soft tissue +fluid-bone +mineral-metal
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contrast radiography
contrast agents= Barium + Iodines- improves visualisation and tissue separation
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Comuputerised tomography (CT)
uses a computer that merges many x-rays from several angles into a single picture- computer can enhance resolution of image
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Angiogram
An X-ray image of blood vessels made after the injection of a radiopaque (contrast) substance
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Angiography risks
1. Internal bleeding and hemorrhage 2. stroke or heart attack 3. Allergic reaction
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Angiography contrast substances
Past= ionic iodinated contrast, today= Nonionic iodinated contrast
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Positives
1. useful for vessels that cannot be seen due to bony structures overlapping 2. arterial, capillary, venous phase subtraction films 3. small lesions, virtually undetectable on routine films are often clearly visible
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Digital subtraction angiography (DSA)
type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in bony or dense soft tissue environments
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Arteriography
used to view arteries in the heart, brain, kidney and others
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Venography (phlebography)
taken after dye is injected into the bone marrow or veins
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Angiocardiography
valves and vessels examined
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Lymphography
visualize structures of the lymphatic system- lymph nodes, ducts, tissue, capillaries and vessels
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Positron Emission Ttomography (PET)
measures metabolic activity of cells- positron-emitting radionuclide injected into the body on a biologically active molecule
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Fluorodeoxyglucose- FDG (18-F)
most common radiotracer- radioactive drug- often tagged to glucose
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Electron-positron annihilation
when collide- leads to annihilation of both- producing a gamma ray photon
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Positron decay (positive beta decay)
radioactive tracer emits a positron
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localisation of the positron emission event
annihilation produces 2 gamma photons at almost 180 degrees from each other- can localize along a straight line of coincidence
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PET uses
which areas involved in reading, listening and speak- receptor activity
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Combined PET and MRI
allows you to study different aspects of a biological system aligned in both space and time - used to pinpoint and access cancers
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Magnetic resonance imaging (MRI)
high-resolution images of soft tissue- using strong magnetic fields and radio waves
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gradient coils
make MF vary at different points in the brain- allows determination of where the signal is coming from
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precession
protons spin (wobble) in line with applied magnetic field
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spin frequency (Lamor frequency)
Wo= wavelength X B0 (applied magnetic field)
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Resonance
transfer/exchange of energy between 2 systems at a specific frequency- Protons emit RF waves in same frequency
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Excitation
Protons jump to higher energy level- net magnetization vector spirals down to transverse plane
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Flip angle
= function of strength and duration of RF pulse
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longitudinal relaxation (T1)
duration magnetisation vector reverts to natural longitudinal direction (ms)- quicker in fats
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Transverse relaxation (T2)
relaxation from the transverse angle- spins interact with each other (aka spin-spin relaxation)- faster in fats
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T1 + T2- fats
shorter T1 (100-150ms) and shorter T2 (10-100ms)
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T1+T2- water
T1= 1.5-2s / T2= 40-200ms)
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T1 weighted images
show fat brigher- TR and TE= shorter
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T2 weighted images
waver brighter- TR and TE have to be longer
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Functional magnetic resonance imaging (fMRI)
using MRI technology that measures brain activity by detecting changes associated with blood flow
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BOLD
Blood Oxygenation Level Dependent activity
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How it works?
oxygenated and deoxygenated hemoglobin respond differently to magnet field and RF pulses- detect ratio
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Other cards in this set

Card 2

Front

Air-fat-soft tissue +fluid-bone +mineral-metal

Back

Radiographic material densities

Card 3

Front

contrast agents= Barium + Iodines- improves visualisation and tissue separation

Back

Preview of the back of card 3

Card 4

Front

uses a computer that merges many x-rays from several angles into a single picture- computer can enhance resolution of image

Back

Preview of the back of card 4

Card 5

Front

An X-ray image of blood vessels made after the injection of a radiopaque (contrast) substance

Back

Preview of the back of card 5
View more cards

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