Radiation Therapy Flashcards Preview

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Flashcards in Radiation Therapy Deck (33):
1

what makes up ionizing radiation?

accelerated high energy particles (photons, electrons, protons, neutrons)
(left end of electromagnetic spectrum)

2

whats it mean to be accelerated?

propelled by electromagnetic fields

3

what is the cellular target of radiation?

DNA

4

how does radiation treatment work?

waves and particles result in lethal double stranded DNA damage. When the cell tries to divide before repairing the damage, it is killed or apoptosed. (Cancer cells divide more often and have mutated repair systems)

5

direct ionization

damages directly within the DNA strand

6

indirect ionization

damages DNA through reactive intermediates (most commonly water)

7

waters role in indirect ionization?

photon knocks electron out of H2Os orbit, resulting in a hydroxyl radical

8

two main methods of radiation delivery

external beam radiation therapy (EBRT) & internal radiation therapy (brachytherapy)

9

EBRT

aiming stuff at the inside from the outside. 3-D conformal

10

brachytherapy

putting radiation close to what you want to hit. Seeds, cylinders, catheters, sutures, etc

11

three main types of EBRT

photons (X-rays), light charged particles (electrons), heavy charged particles (protons)

12

how did the linear accelerator advance radiation therapy?

by allowing high energy beams to be used, we can now treat something deep without the majority of the absorbance occurring at the skin

13

how does proton therapy work?

protons deposit energy and then stop. beam peaks where you want to treat and then has no exit dose. deposits all energy at area of interest

14

radiosensitivity

lab term referring to in vitro sensitivity, described by favorable cell survival curves

15

radioresponsiveness

clinical term referring to a measurable change in tumor size during or after treatment. generally correlated with radio sensitivity, but not always!

16

therapeutic index

measure of the relative effect of treatment on the tumor compared to normal tissues (aim for 10/15)

17

unit of radiation

Grey (Gy)

18

acute toxicity

acute side effects to RT. damage to quickly dividing tissues

19

late toxicity

late side effects of RT that damage slow/non-dividing cells

20

fractionation

stretching RT treatments out over a longer period of time. Can get away with higher dose treatments

21

four Rs of radiobiology

Reassortment, Reoxygenation, Repair, Repopulation

22

Reassortment/Redistribution

using fractionation to hit cells at different times in their cell cycles

23

Reoxygenation

when you first use RT, you damage some tumor cells and they then are remodeled, allowing more oxygen radicals to flow in and damage them the second time around

24

Repair

Fractionation allows normal tissues time to repair sublethal damage caused by the previous round of therapy

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Repopulation

Negative against fractionation. Tumor cells have a chance to grow back when treatment isn't continuous

26

hypofractionation

palliative treatment. goal is to help patient manage symptoms.

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standard fractionation

curative treatment daily

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hyperfractionation

curative treatment twice daily

29

definitive radiation therapy

using radiation therapy as a cure without surgery. for solid and lymphoid malignancies

30

neoadjuvant RT

pre-operative radiation.
Advantages: smaller treatment volume, more radiosensitive, improve surgeons success

31

adjuvant RT

post-operative radiation
Advantages: tailor RT fields to surgical findings, avoid unnecessary RT

32

chemotherapy's role with RT?

works as a radio sensitizer. low dose, concurrent chemo is synergistic with RT

33

how can chemo possibly help RT?

direct enhancement of radiation damage by incorporating drugs into DNA, inhibits cellular repair, accumulates cells in radiosensitive cycle phase, works against hypoxic (radioresistant cells), inhibits accelerated repopulation