Rad Onc High yield Q's Flashcards
MU calculation for electrons
Gamma decay effects on A & Z
A & Z stay the same
Us imaging
- uses sound waves for imaging.
- higher frequency-> shorter wavelength -> higher spatial resolution
- Increase in spatial resolution, decreases penetration
SBRT with arcs
Use non coplanar arcs
Arcs should not cross any critical structures
Electrons beam characteristics
ex 90% for 10 MEV : 10/3.3 = 3.0
What is NOT required for electron treatment?
Flattening filter
What is NOT required for photons treatment
scattering foil
Cataracts are caused by which type of radiation
Neutrons
Why do MLCs have round edges
to keep transmission penumbra constant for different leaf positions
Tongue and groove pattern for MLCs
to reduce leakage between leaves
How to calculate lead thickness for electron beam
- Electrons lose 2 MeV per cm of tissue when they pass through.
- so if 12 MeV is passing through a 3 cm lesion 6MeV is lost (3x3=6, 12-6=6)
- lead shield is used for attenuation. It attenuates by 2MeV per mm. so for 6MeV , a minimum of 3mm lead shielding is needed.
Mass of Electron
511”K”eV
How to calculate Dmax/hot spot
Dmax = Dd/PDD
- Dd = dose
- PDD = percent depth dose
TLDs
reusable
can detect wide dose range
Avg energy required for a charged particle to produce an ion pair
33.97eV
dmax for photon beam
6 MeV = 1.5 cm
10 MeV = 2.5 cm
15 MeV = 3 cm
18 MeV = 3.5 cm
Basic MRI sequences
T1: gray matter is gray white matter is white
T1 post:
T2: fluid is bright on T2
T2 Flair: edema/fluid accumulation
Another formula to remember
Make sure gms is converted to kg
What is half life
Time required for the activity to decrease by one half
What is fluence
ratio of N/A
N: Number of photons
A: area, cross sectional area
What is activity
Number of decay per second.
What is exposure
Ionization of a given mass by air.
TG-142
Light and radiation fields should be checked at what interval?
Monthly!
How to calculate BED?
Important Linac picture! Memorize!!
1 mCi is
37 MBq
.
.
Important to know milli curie and MBq for Becquerel
Inverse square law
Who discovered X-rays, got nobel prize
Wilhelm Conard Rontgen, 1901
