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PET
Radionuclei which emit positrons ino the body. Gamma rays prod. when the positrons encounter with el.
Concentional linar/ axial tomography
- Conventional: x-ray tube + film linked together
- Axial: image of a slice of the body
Doppler effect
Change in frequency of a wave, observed when the source of waves is moving with respect to the detector.
In-vitro/in-vivo use of radioisotopes
In-vitro: determine amount of hormones. Manily RIA.
In-vivo: diagnostic of thyroid gland - iodine uptake measurement.
Stochastic/deterministic effects
Stochastic: frequency of damage, but not severity, depends on the dose without threshold. Heritable and carcinogenic.
Deterministic: result from collective injury of many cells. E.g.lens cataract.
Radiation units
- Source activity: nr. of decays in unit time - becquerel
- Exposure: amount of radiation reaching the material-röntgen
- Absorbed dose: energy absorbed by unit mass of material from ionizing radiations-gray
- Dose equivalent: effect on bio.system-sievert
Alpha, beta and gamma radiations
- Aplha: +charge - helium nucleus He2+
- Beta: an electron, mostly neg.charge - can be positron
- Gamma: EM radiation (light, x-rays, etc)
Oscilloscope
El.gun with accelerating anode. Electron test instrument that observes signal voltages.
ECG-signal
- 0.25s,small increase-depolarization
- 0.5s, high peak-ventricle depolarisation and contraction
- Just after peak, small increase-ventricle repolarization
- Repeat
Measurement of membr.pot.
Diff.conc. of ions on either side of membr.
- Electrophysiological - w.electrodes
- Electric potential sensitive staining, or charged
Action potential
-50mV is the critical threshold value. After stimuli, pot.increases-becomes pos. and reaches +50mV. Then return to resting value.
Electromchemical pot.
Depends on gas constant, faraday constant, absolute temp and electrical pot.
Excitability
Electric pot.diff. in each living cell measured between the cytoplasm and extracellular regions.
Resistance/capitance
Cause impedance/resistance in a circuit. Capasitor: pair of conducting sheet sep. by an insulating layer.
Photoeffect/compton scattering/pair production
Photoeffect: x-ray gives E to an el. of an inner shell
Compton scattering_ x-ray hits an outer el. and splits into 2 rays with smaller E
Pair production: photon becomes an el. and positron
LASER
Light amplification by stimulated emission of radiation.
Monochromatic, coherent, directed and well focusable.
Scattering: Rayleigh, Raman and compton
Light of any frequency can produce scattering.
- Coherent: emission of photon with same frequency as incoming.
- Raman: emission of photon with higher/lower frequency
- Compton: photon collides with free el. and changes it´s E
Photoelectric effect
Release of el. from a metal surface when illuminated by a light of certain wavelength.
EM
Shorter wavelength of el. to reach a higher resolving power to create an image. El.gun shoots el. through a sample.
Rayleigh´s criteria
A point where resolution is obtained is where the central max. of an airy disk fall into the first min. of another airy disk.
Huygen-Fresnel principle
Any point of a wave front can be considered a source of sec.spherical wavelets. Obs. light intensity at a given point is determined by the interference of these wavelets.
EM spectrum
Differ in wavelenghts only.
- X-rays, Gamma, UV: 700 nm
- Human eye most sensitive to ca. 550 nm
Simple and compound magnifier
Simple: enlarges visual angle of object, by placing the object inside focal point of the converging lens.
Compound: an objective and ocular lens that magnified the image more and focuses the retina of the eye.
Accomodation width
Ability to shift from a short focus to infinity. A=Pn-Pf=4D
Abberations
Limits the sharpness of image.
- Spherical: diff. focus in centre and outer parts
- Chromatic: if the light has diff. wavelengths, the index of refraction will split the rays, which have diff. focuses
- Astigmation: lens don´t focus light to a point, prod. 2 images at diff. distances.
Ray-tracing method
3 rays from an object which are easily predictable.
- 1 parallel with the axis - passing through the focal point
- 1 through the focal point - emerges from lens parallel to the axis
- 1 undeflected through center of lens
Image formation
Diverging rays from an object crosses after reflection/refraction. This crossing-point is the image of the object.
Geometric optics
Describes light propagation in terms of rays.
