dose fractionation in radiotherapy Flashcards

1
Q

in the linear-quadratic model, what does alpha link to

A

single-stranded DNA breaks

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2
Q

in the linear-quadratic model, what does beta link to

A

double-stranded DNA breaks

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3
Q

in the linear-quadratic model, what does “the shoulder” link to

A

“sublethal” damage

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4
Q

what is the cell response to cell death caused by ionising radiation

A
  1. repairing sublethal damage
  2. reassortment to more radiosensitive phases
  3. reoxygenation
  4. repopulation
  5. redistribution
  6. radiosensitivity
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5
Q

why do we fractionate

A

to limit damage to surrounding tissues

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6
Q

what does biologically equivalent dose allow us to do

A

compare the potency of various fractionation regimens - alpha-beta ratios needed

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7
Q

what does the linear quadratic model describe

A

the relationship between total isoeffective dose and dose from 1 Gy-5/6 Gy

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8
Q

conclusions of the linear quadratic model

A
  1. late response in normal tissues
  2. early response in rapidly proliferating carcinoma
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9
Q

what is the LQM useful for calculating

A

change in total dose for an altered dose

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10
Q

dose needed for lymphomas and semiomas

A

40Gy or less

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11
Q

dose needed for glioblastoma multiforme

A

70Gy (currently lowered to 60)

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12
Q

what must be considered for palliative RT

A

short timing, convenience, cost, minimal side effects

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13
Q

RT for management of signs of progressive cancer

A

higher doses, more conformal techniques to prevent symptoms

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14
Q

what is oligometastatic disease

A

the midway between localised and metastatic disease

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15
Q

pros of SABR

A

safe, feasible, efficient

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16
Q

stereotaxia meaning

A

3D arrangement to touch

17
Q

what is SRS

A

stereotactic radiosurgery

18
Q

what is fSRT

A

fractionated stereotactic radiation therapy

19
Q

what does SRS/SABR use to create a compact dose

A

intensity modulation
image guidance
motion control
stereotactic targeting

20
Q

what are the 8 different fractionation regimes

A
  1. CHART
  2. Hyperfractionation
  3. conventional
  4. SIB
  5. Moderate hypofractionation
  6. Extreme hypofractionation
  7. SBRT
  8. SRS/ FSRT
21
Q

advantage of hyperfractionation

A

more rapid increase in tolerance with decreasing dose for late tissues

22
Q

what does accelerated RT aim to reduce

A

the protective effect of tumour cell repopulation

23
Q

what does hypofractionation increase and what is it used for

A

increases late effects and is used for both curative and palliative care

24
Q

how long should the gap be if you’re giving multiple fractions per day

A

6 Hrs