Image Acquisition

Question 1

Bremsstrahlung

Answer 1

Bending of electron, loses velocity, releases radiation. (Happens in anode)

Question 2

Characteristic radiation

Answer 2

Electron knocks electron away in inner shell. Electron from outer shell falls to lower shell and emits radiation

Question 3

Rayleigh/Coherent scattering

Answer 3

(<30 keV) Photon is bent in its trajectory

Question 4

Photo-electric absorption

Answer 4

Photon knocks out electron

Question 5

Compton scattering

Answer 5

Photon knocks out electron but has energy left and continues in a different direction

Question 6

Pair production

Answer 6

(>1.02 MeV) Photon is annihilated, creating electron and positron

Question 7

(Nuclear) B- emission

Answer 7

n–>p+ e- ,immediate or delayed radiation, used for SPECT

Question 8

(Nuclear) Electron capture

Answer 8

p+ e- –> n ,electron collapses to nucleus, releasing radiation

Question 9

(Nuclear) B+ emission

Answer 9

p+ –> n + e+ ,positron annihilates after 2mm, 2 opposite radiation released

Question 10

(Radio)
GTV
CTV
PTV

Answer 10

Gross target volume (tumor size)
Clinical target volume (GTV + buffer with expected tumor cell infiltration)
Planning target volume (CTV + buffer to not miss target due to movement ect)

Question 11

IMRT
DVH
MLT

Answer 11

Delivery of radiation with non-uniform fluence
Dose volume histogram (volume of tumor or OAR that receives at least a dose)
Gives the radiation any shape desirable

Question 12

MRI fields

Answer 12

B0, main field
Gradient coils, local and linear (x mT/m) variations in B0 field. Essential for spatial encoding.
B1, block pulse

Question 13

Dephasing

Answer 13

Dephasing makes Mt decay faster in comparison to regrowth of Mz. Caused by spin-spin interactions and B0 inhomogenity.

Question 14

T2*

Answer 14

T2* is the relaxation time of Mt including field inhomogenity, T2 excludes this and is therefore always larger.

Question 15

TE

Answer 15

Time of echo

Question 16

y-stripe

Answer 16

D I V I D E by 2pi

Question 17

Truncated sinc pulse

Answer 17

Block function in f domain, becomes infinite sinc funtion when reverted but ends are cut off.

Question 18

Speed of Sound

Answer 18

c0= sqrt(k0/p0)

Question 19

(US) Transducer

Answer 19

Converts electrical energy to mechanical energy AND VICA VERCA (Inverse piezoelectric effect)

Question 20

(US) Acoustic Impedence

Answer 20

Difference causes reflection. Z(Rayl) = p/v = rho0*c0

Question 21

(US) Ri/e

Answer 21

What part is reflected back, root of this is the fraction reflected pressure

Question 22

(US) Ti/e

Answer 22

1 - Ri/e, What part is transmitted

Question 23

(US) Spin echo

Answer 23

Spins that were running ahead and behind are inverted and begin de-dephasing after a 180* pulse with t=TE/2

Question 24

Gradient Echo

Answer 24

e^(-TE/T2*) Is fast af

Question 25

Spin Echo

Answer 25

e^(-TE/T2)

Question 26

delta f

Answer 26

ystrike * Gz * delta z

Question 27

T1 weighed/T2 weighed

Answer 27

TR is too short for full Mz recovery/TE is long enough for significant Mt decay