Wk09 HDR Brachytherapy Flashcards
What is the most common radioactive source for HRD brachytherapy?
Ir192
What is the dose rate for HDR brachytherapy?
> 12Gy/h
Name some vendors for Ir192 brachytherapy unit
Elekta (microselectron+flexitron)
Varian(Bravos)
BEBIG(Multiusource)
What is the half life of 192-Ir
74Days
What is the decay chain of Ir-192?
Beta decay to Pt-192 then electron capture to Os-192
What is the half-value layer of Ir-192 (Pb and concrete)
2.5mm Pb and 44.5 concrete
What is the function of the check cable in the afterloader?
- check the channels
- male sure no obstruction
What are the treatment parameters of brachytherapy plans?
Dwell positions and dwell times
The shielded safe reduce the air kerma rate to _________.
1-4 uGy/h
What material is used to make the shielded safe?
Tungsten or depleted uranium
What are the safety features of the brachytherapy suite?
- emergency switches
- emergency crank
- door interlock
- audio/visual system
- radiation monitor / treatment on monitor
- emergency service instrument
- back up battery
How do the Vienna ring helps in visualising source channel in MR images?
Real source positions are in relation to the outer dimensions and holes of the Vienna ring applicator. Acceptance tests and regular check is needed
What is the fractionation of IGBT cervix?
7Gy x 4, 2 fractions per week
What are the components of TG-43 2D formalism?
Source strength
Dose rate constant
Geometry function
Radial dose function
2D anisotropic function
The geometry function accounts only ______________, neglecting __________________
Inverse square law ; scatter and attenuation
The radial dose function accounts for _______________________________________.
Dose fall off in the transverse plane due to photon scattering and attenuation.
What are the limitations of TG-43 2D formalism.?
- homogeneous water medium is assumed
- full scatter condition assumed
- electrons produced are neglected
- 3D source geometry is not taken into account
Shielded applicator can ___________________.
Significantly reduce dose to OARs
What is the definition of commissioning?
The process by which an equipment, facility or plant is tested to verify if it functions according to its design objectives or specifications
What are the basic commissioning procedures?
- general software functions specify by manufacturer
- training
- integration into IT environment
- acceptance testing plans
Where do the point A defined?
2cm above the external cervical os
2cm lateral to midline
Where to point B defined?
2cm above the external cervical os
5cm lateral to midline
What is IPSA and its limitation
Inverse planning by simulated annealing
Too ideal and plan parameters varies dramatically
What is HIPO and its strengths?
Hybrid inverse planning optimazation
More user friendly and realistic / applicable
