DDT.6

Question 1

Explain the electromagnetic spectrum.

Answer 1

Towards the left (Visible light –> infrared –> Radiowaves) the energy decreases as the wavelength increases [longer].

Towards the right (UV –> X-rays –> Gamma rays) the energy increases as the wavelength decreases [shorter].

Question 2

Radiation with a frequency greater than ?? Hz will actually break bonds and cause electrons to be freed from an atom.

Answer 2

1X10^15 Hz

Question 3

For biological tissue, what wavelength and photon energies are said to be ionizing?

Answer 3

Wavelengths less than 300nm (UV).
Photon energies greater than 4 eV.

Question 4

What are the 2 types of ionizing radiation?

Answer 4

1) Electromagnetic Radiation
- Ultraviolet (UV)
- X-ray
- Gamma ray (Y)
2) Particle Radiation
- Alpha
- Beta
- Neutron

Question 5

Biological effects of ionizing radiation principally result from?

Answer 5

Damage to cellular DNA, which can either happen directly or indirectly.

Question 6

Radio [10^4Hz], Microwaves [10^8Hz], Millimeter [10^8Hz].

Answer 6

Commonly penetrated by this from Radio & TV.

Question 7

Infrared [10^12Hz]

Answer 7

Tiny amounts of absorption.

Question 8

Visible [10^15Hz]

Answer 8

Strongly absorbed, but not ionizing.

Question 9

Ultraviolet [10^16Hz]

Answer 9

Very strongly absorbed and can ionize.

Question 10

X-ray & Y [10^18Hz] + particles

Answer 10

Ionizing!!

Question 11

What 3 biological effects are not considered ionizing?

Answer 11

• Electron level changes (infrared)
• Molecular vibration (Microwave)
• Molecular rotation & torsion

Question 12

Radiotherapy

Answer 12

the use of ionizing radiation to stop cancer cells from growing and dividing, by damaging their genetic material (DNA). It is generally a loaclised treatment for solid tumors, such as: cancers of the skin, tongue, larynx, brain, breast, uterine cervix, etc…but may also be used to treat leukaemia and lymphoma.

Question 13

How are the normal, healthy cells not damaged by ionizing radiation?

Answer 13

White ionizing radiation can damage both healthy and malignant cells, the normal cells are given an opportunity to repair themselves and function normally.

Question 14

Describe the sequence of radiation effects.

Answer 14

Incident X-ray photon

Photoelectric absorption/compton scattering/pair production

Ionizing the DNA molecule AND/OR formation of free radicals

DNA damage

Biological affects
(mutation & cancer) –> Low dose
(cell death) –> high dose

Question 15

How can we save healthy tissue while trying to target malignant tissue?

Answer 15

By using fractionation of radiotherapy.
We determine how much radiation we need to treat the cancer and decide to administer this via a number of fractions over time. This way we can give healthy tissue the greatest chance to repair and survive.

Question 16

How are tumors not given an equal chance to repair and survive when using fractionation of radiotherapy?

Answer 16

Tumors are more sensitive tp radiation than normal tissues.

Question 17

A number of types of high energy radiation can be used in radiotherapy, what are they?

Answer 17

X-rays
Gamma rays
Electrons
(The type of radiation is selected for the specific patient and application).

Question 18

External Beam Radiotherapy

Answer 18

linear accelerator

Question 19

Brachytherapy

Answer 19

Radioactive material placed inside patient.

Question 20

For external treatments using X-rays, electrons, or cobalt-60 gamma rays, SEVERAL beams of radiation may be used to treat the tumor. What does this technique provide?

Answer 20

-Maximum cumulative dose to the tumor (where beams overlap).
-Minimal damages to surrounding healthy tissue.

Question 21

What are the side effects from Radiotherapy?

Answer 21

Body aches, swelling, second cancer, skin burning, feeling tired.

Question 22

Careful treatment planning is an integral part of the therapy process for all forms of radiotherapy. Explain the process of radiotherapy treatment planning.

Answer 22

1) The precise location of the tumor is located using advanced imaging techniques (Such as ultrasound, CT, MRI).
2) Complex mathematical models and simulations are used to predict what pattern of irradiation should be used to give an energy distribution within the tissue that would destroy the tumor, but cause minimal damage to healthy tissue and surrounding vital organs such as the spine.

Question 23

Radiotherapy Treatment Planning Process.
[The 4 determinations!]

Answer 23

1) Precise determination of the location, size, and structure of the tumor.

2) Precise determination of the energy dose required to destroy the tumor.

3) Determination of HOW the radiation must be distributed within the tissue to provide the appropriate energy distribution based on the tumor size and shape to destroy the tumor. [how many beams, direction, strength, etc].

4) Determination of the energy dose to normal non-malignant tissue in an attempt to minimise damage.

+the correct positioning of the patient (may use protective masks) according to the treatment plan to measure and monitor the incident energy at strategic locations to ensure doses are not exceeded.

Question 24

What is the purpose of protective masks?

Answer 24

-To hold the patient in place during treatment.
-To minimize unwanted exposure to sensitive areas.

Question 25

Complex Dosimetry Simulators for treatment planning in ______________ are available.

Answer 25

Radiotherapy

Question 26

The colored contours represent iso-contours of ???, resulting from 3 separate beams of radiation.

Answer 26

Cumulative deposited energy.

Question 27

The area bounded by the innermost contour will have a deposited energy greater than or less than required to kill the tumor? [area is where the tumor is completely contained]

Answer 27

Greater than

Question 28

What shape each beam to the outline of the tumor?

Answer 28

Multileaf collimators (MLC)

Question 29

Explain what is meant by the term ionizing radiation.

Answer 29

When the radiation can break bonds and cause electrons to be freed from an atom.