Th - Intensity Modulated Radiotherapy

Question 1

What does OAR mean?

Answer 1

Organ at Risk

Question 2

How much percent of the prescribed dose is PTV? (num-num)

Answer 2

95-107%

Question 3

What is IMRT?

Answer 3

Irradiation with fixed beam directions

Question 4

What is VMAT?

Answer 4

Continuous irradiation while rotating around the patient

Question 5

Is VMAT faster than IMRT?

Answer 5

Yes

Question 6

What kind of radiotherapy is done for breast cancer?

Answer 6

IMRT

Question 7

Systematic error since it will impact the entire treatment has a very big impact on the treatment margins

Answer 7

Random error is more about small differences between the average

Question 8

Question:
If we do something wrong in this definition, is it a systematic or a random error?

Answer 8

Answer is systematic.

Question 9

What kind of radiation is used for CT imaging?

Answer 9

High energy photons

Question 10

What kind of radiation is used for radiotherapy?

Answer 10

Even higher energy photons

Question 11

Does CT account for a dose burden?

Answer 11

Yes

Question 12

Why is target delineation so important in radiotherapy (RT)?

Answer 12

Needs to encompass the tumor (and spread)

Question 13

How do we handle delineation uncertainties?

Answer 13

Apply margins

Question 14

What kind of error is a delineation error? How does this impact the margin?

Answer 14

Delineation is systematic (not random) and is thus a large component in the margin.

Question 15

An error in the co-registration lead to what kind of error?

Answer 15

Systematic

Question 16

Co-registration of multiple modalities have residual mismatches. Can you name a few reasons for these mismatches? (3)

Answer 16

• Inter-observer error
• Organ motion
• Organ deformation

Question 17

What are ways to incorporate respiratory motion in radiotherapy? (4)

Answer 17

• Increase margins
• Gated RT (beam on/off)
• Tracking (following the motion)
• Minimize respiratory motion (breath-holding)

Question 18

Give examples on how pre-treatment CT is enhanced for RT

Answer 18

-> personalized treatment’

Question 19

What are in general the main reasons why imaging is always performed before any radiotherapy treatment is delivered.
(3)

Answer 19

Tumor location/extent Motion, organ motion, characterisation

Question 20

What is the trade off-challenge in radiation therapy

Answer 20

Damage

Question 21

Explain why cancer radiotherapy needs to be personalized

Answer 21

Needs to be personalized because no two people and tumours are the same