Th - Intensity Modulated Radiotherapy Flashcards
What does OAR mean?
Organ at Risk
How much percent of the prescribed dose is PTV? (num-num)
95-107%
What is IMRT?
Irradiation with fixed beam directions
What is VMAT?
Continuous irradiation while rotating around the patient
Is VMAT faster than IMRT?
Yes
What kind of radiotherapy is done for breast cancer?
IMRT
Systematic error since it will impact the entire treatment has a very big impact on the treatment margins
Random error is more about small differences between the average
Question:
If we do something wrong in this definition, is it a systematic or a random error?
Answer is systematic.
What kind of radiation is used for CT imaging?
High energy photons
What kind of radiation is used for radiotherapy?
Even higher energy photons
Does CT account for a dose burden?
Yes
Why is target delineation so important in radiotherapy (RT)?
Needs to encompass the tumor (and spread)
How do we handle delineation uncertainties?
Apply margins
What kind of error is a delineation error? How does this impact the margin?
Delineation is systematic (not random) and is thus a large component in the margin.
An error in the co-registration lead to what kind of error?
Systematic
Co-registration of multiple modalities have residual mismatches. Can you name a few reasons for these mismatches? (3)
- Inter-observer error
- Organ motion
- Organ deformation
What are ways to incorporate respiratory motion in radiotherapy? (4)
- Increase margins
- Gated RT (beam on/off)
- Tracking (following the motion)
- Minimize respiratory motion (breath-holding)
Give examples on how pre-treatment CT is enhanced for RT
-> personalized treatment’
What are in general the main reasons why imaging is always performed before any radiotherapy treatment is delivered.
(3)
Tumor location/extent Motion, organ motion, characterisation
What is the trade off-challenge in radiation therapy
Damage
Explain why cancer radiotherapy needs to be personalized
Needs to be personalized because no two people and tumours are the same
