Aller aller viktigst

Question 1

PET

Answer 1

Radionuclei which emit positrons ino the body. Gamma rays prod. when the positrons encounter with el.

Question 2

Concentional linar/ axial tomography

Answer 2

• Conventional: x-ray tube + film linked together

- Axial: image of a slice of the body

Question 3

Doppler effect

Answer 3

Change in frequency of a wave, observed when the source of waves is moving with respect to the detector.

Question 4

In-vitro/in-vivo use of radioisotopes

Answer 4

In-vitro: determine amount of hormones. Manily RIA.

In-vivo: diagnostic of thyroid gland - iodine uptake measurement.

Question 5

Stochastic/deterministic effects

Answer 5

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.

Question 6

Radiation units

Answer 6

• 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

Question 7

Alpha, beta and gamma radiations

Answer 7

• Aplha: +charge - helium nucleus He2+
• Beta: an electron, mostly neg.charge - can be positron
• Gamma: EM radiation (light, x-rays, etc)

Question 8

Oscilloscope

Answer 8

El.gun with accelerating anode. Electron test instrument that observes signal voltages.

Question 9

ECG-signal

Answer 9

1. 0.25s,small increase-depolarization
2. 0.5s, high peak-ventricle depolarisation and contraction
3. Just after peak, small increase-ventricle repolarization
4. Repeat

Question 10

Measurement of membr.pot.

Answer 10

Diff.conc. of ions on either side of membr.

1. Electrophysiological - w.electrodes
2. Electric potential sensitive staining, or charged

Question 11

Action potential

Answer 11

-50mV is the critical threshold value. After stimuli, pot.increases-becomes pos. and reaches +50mV. Then return to resting value.

Question 12

Electromchemical pot.

Answer 12

Depends on gas constant, faraday constant, absolute temp and electrical pot.

Question 13

Excitability

Answer 13

Electric pot.diff. in each living cell measured between the cytoplasm and extracellular regions.

Question 14

Resistance/capitance

Answer 14

Cause impedance/resistance in a circuit. Capasitor: pair of conducting sheet sep. by an insulating layer.

Question 15

Photoeffect/compton scattering/pair production

Answer 15

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

Question 16

LASER

Answer 16

Light amplification by stimulated emission of radiation.

Monochromatic, coherent, directed and well focusable.

Question 17

Scattering: Rayleigh, Raman and compton

Answer 17

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

Question 18

Photoelectric effect

Answer 18

Release of el. from a metal surface when illuminated by a light of certain wavelength.

Question 19

EM

Answer 19

Shorter wavelength of el. to reach a higher resolving power to create an image. El.gun shoots el. through a sample.

Question 20

Rayleigh´s criteria

Answer 20

A point where resolution is obtained is where the central max. of an airy disk fall into the first min. of another airy disk.

Question 21

Huygen-Fresnel principle

Answer 21

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.

Question 22

EM spectrum

Answer 22

Differ in wavelenghts only.

• X-rays, Gamma, UV: 700 nm
• Human eye most sensitive to ca. 550 nm

Question 23

Simple and compound magnifier

Answer 23

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.

Question 24

Accomodation width

Answer 24

Ability to shift from a short focus to infinity. A=Pn-Pf=4D

Question 25

Abberations

Answer 25

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.

Question 26

Ray-tracing method

Answer 26

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

Question 27

Image formation

Answer 27

Diverging rays from an object crosses after reflection/refraction. This crossing-point is the image of the object.

Question 28

Geometric optics

Answer 28

Describes light propagation in terms of rays.