Wk09 HDR Brachytherapy Flashcards

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1
Q

What is the most common radioactive source for HRD brachytherapy?

A

Ir192

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2
Q

What is the dose rate for HDR brachytherapy?

A

> 12Gy/h

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3
Q

Name some vendors for Ir192 brachytherapy unit

A

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

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4
Q

What is the half life of 192-Ir

A

74Days

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5
Q

What is the decay chain of Ir-192?

A

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

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6
Q

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

A

2.5mm Pb and 44.5 concrete

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7
Q

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

A
  • check the channels
  • male sure no obstruction
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8
Q

What are the treatment parameters of brachytherapy plans?

A

Dwell positions and dwell times

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9
Q

The shielded safe reduce the air kerma rate to _________.

A

1-4 uGy/h

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10
Q

What material is used to make the shielded safe?

A

Tungsten or depleted uranium

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11
Q

What are the safety features of the brachytherapy suite?

A
  • emergency switches
  • emergency crank
  • door interlock
  • audio/visual system
  • radiation monitor / treatment on monitor
  • emergency service instrument
  • back up battery
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12
Q

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

A

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

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13
Q

What is the fractionation of IGBT cervix?

A

7Gy x 4, 2 fractions per week

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14
Q

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

A

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

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15
Q

The geometry function accounts only ______________, neglecting __________________

A

Inverse square law ; scatter and attenuation

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16
Q

The radial dose function accounts for _______________________________________.

A

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

17
Q

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

A
  • homogeneous water medium is assumed
  • full scatter condition assumed
  • electrons produced are neglected
  • 3D source geometry is not taken into account
18
Q

Shielded applicator can ___________________.

A

Significantly reduce dose to OARs

19
Q

What is the definition of commissioning?

A

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

20
Q

What are the basic commissioning procedures?

A
  • general software functions specify by manufacturer
  • training
  • integration into IT environment
  • acceptance testing plans
21
Q

Where do the point A defined?

A

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

22
Q

Where to point B defined?

A

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

23
Q

What is IPSA and its limitation

A

Inverse planning by simulated annealing

Too ideal and plan parameters varies dramatically

24
Q

What is HIPO and its strengths?

A

Hybrid inverse planning optimazation

More user friendly and realistic / applicable