Wk09 HDR Brachytherapy

Question 1

What is the most common radioactive source for HRD brachytherapy?

Answer 1

Ir192

Question 2

What is the dose rate for HDR brachytherapy?

Answer 2

> 12Gy/h

Question 3

Name some vendors for Ir192 brachytherapy unit

Answer 3

Elekta (microselectron+flexitron)
Varian(Bravos)
BEBIG(Multiusource)

Question 4

What is the half life of 192-Ir

Answer 4

74Days

Question 5

What is the decay chain of Ir-192?

Answer 5

Beta decay to Pt-192 then electron capture to Os-192

Question 6

What is the half-value layer of Ir-192 (Pb and concrete)

Answer 6

2.5mm Pb and 44.5 concrete

Question 7

What is the function of the check cable in the afterloader?

Answer 7

• check the channels
• male sure no obstruction

Question 8

What are the treatment parameters of brachytherapy plans?

Answer 8

Dwell positions and dwell times

Question 9

The shielded safe reduce the air kerma rate to _________.

Answer 9

1-4 uGy/h

Question 10

What material is used to make the shielded safe?

Answer 10

Tungsten or depleted uranium

Question 11

What are the safety features of the brachytherapy suite?

Answer 11

• emergency switches
• emergency crank
• door interlock
• audio/visual system
• radiation monitor / treatment on monitor
• emergency service instrument
• back up battery

Question 12

How do the Vienna ring helps in visualising source channel in MR images?

Answer 12

Real source positions are in relation to the outer dimensions and holes of the Vienna ring applicator. Acceptance tests and regular check is needed

Question 13

What is the fractionation of IGBT cervix?

Answer 13

7Gy x 4, 2 fractions per week

Question 14

What are the components of TG-43 2D formalism?

Answer 14

Source strength
Dose rate constant
Geometry function
Radial dose function
2D anisotropic function

Question 15

The geometry function accounts only ______________, neglecting __________________

Answer 15

Inverse square law ; scatter and attenuation

Question 16

The radial dose function accounts for _______________________________________.

Answer 16

Dose fall off in the transverse plane due to photon scattering and attenuation.

Question 17

What are the limitations of TG-43 2D formalism.?

Answer 17

• homogeneous water medium is assumed
• full scatter condition assumed
• electrons produced are neglected
• 3D source geometry is not taken into account

Question 18

Shielded applicator can ___________________.

Answer 18

Significantly reduce dose to OARs

Question 19

What is the definition of commissioning?

Answer 19

The process by which an equipment, facility or plant is tested to verify if it functions according to its design objectives or specifications

Question 20

What are the basic commissioning procedures?

Answer 20

• general software functions specify by manufacturer
• training
• integration into IT environment
• acceptance testing plans

Question 21

Where do the point A defined?

Answer 21

2cm above the external cervical os
2cm lateral to midline

Question 22

Where to point B defined?

Answer 22

2cm above the external cervical os
5cm lateral to midline

Question 23

What is IPSA and its limitation

Answer 23

Inverse planning by simulated annealing

Too ideal and plan parameters varies dramatically

Question 24

What is HIPO and its strengths?

Answer 24

Hybrid inverse planning optimazation

More user friendly and realistic / applicable