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Ph RadOnc Residency PBRROE2-3 Review 2021 > Uterine Cervix: Brachytherapy (under construction) > Flashcards

Uterine Cervix: Brachytherapy (under construction) Flashcards

1
Q

Uterine Cervix

What is the ICRU 38 definition of “low lose rate (LDR)” brachytherapy?

A

0.4 to 2 Gy/hr

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2
Q

Uterine Cervix

What is the ICRU 38 definition of “medium dose rate (MDR)” brachytherapy?

A

2 to 12 Gy/hr

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3
Q

Uterine Cervix

What is the ICRU 38 definition of “high dose rate (HDR)” brachytherapy?

A

> 12 Gy/hr

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4
Q

Uterine Cervix

What is the most commonly used isotope for “low lose rate (LDR)” brachytherapy according to ICRU 38?

A

144Cs

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5
Q

Uterine Cervix

What is the most commonly used isotope for “high lose rate (HDR)” and PDR brachytherapy according to ICRU 38?

A

206Ir

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6
Q

Uterine Cervix

What is the conversion factor from LDR to HDR when using 3-5 HDR fractions?

A
  1. 54 to 0.6 (Orton et al.)
  2. 58 (Patel et al.)
  3. 75 when 6-8 HDR fractions are used.
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7
Q

Uterine Cervix

Late damage rises sharply as the number of HDR fractions is increased.

TRUE or FALSE?

A

False.

Late damage rises sharply as the number of HDR fractions is decreased.

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8
Q

Uterine Cervix

What are the conditions for an adequate intracavitary insertion?

A

The geometry of the insertion must prevent underdosing around the cervix.

Sufficient dose must be delivered to the paracervical areas.

Vaginal mucosal, bladder, and rectal tolerance doses must be respected.

(Fletcher)

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9
Q

Uterine Cervix

What “are” the purposes of an adequately placed vaginal packing?

A

to separate the bladder and rectum

to help to maintain applicator position

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10
Q

Uterine Cervix

What is the definition of point A based on ICRU and ABS if using tandem+ovoids, i.e., fletcher suit

Trace the course of delineation from the ovoids.

A

connect a line through the center of each ovoid, extended superiorly along the radius of the ovoids.

move an additional 2 cm superiorly along the tandem

then additional 2 cm laterally perpedicular to the tandem.

This is point A.

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11
Q

Uterine Cervix

What is the definition of Point A based on ICRU and ABS if using tandem+cylinder, i.e., Miami applicator.

A

2 cm superiorly from the cervical marker, along the tandem, then 2 cm laterally.

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12
Q

Uterine Cervix*

What anatomical structure is represented by the Point A?

A

paracervical triangle where uterine artery crosses the ureter

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13
Q

Uterine Cervix*

Locate the Point B in relation to Point A.

Also identify the anatomical structures is represented by this point.

A

Point B is located 5 cm lateral to midline (3 cm from point A) at the same level as point A. It also gives a guide as to the lateral spread of the radiation dose.

Point B - Represents the pelvic side wall/obturator nodes

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14
Q

Uterine Cervix

What is the definition of GTV based on CT imaging for an IGBT procedure?

A

None.

Gross tumor cannot be identified.
Instead, the entire uterus and cervix is contoured.

The superior border of the cervix cannot be defined, but instead, the entire tandem length is planned and the top dwell is optimized off the sigmoid to reduce bowel dose.

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15
Q

Uterine Cervix

GEC-ESTRO MRI contouring for IGBT.

GTV?

A

gross tumor + all T2 bright enhancing area

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16
Q

Uterine Cervix

GEC-ESTRO MRI contouring for IGBT.

HR-CTV?

A

GTV + entire cervix, + any regions of high to intermediate signal intensity in the parametria, uterus, or vagina, or any residual on clinical exam at the time of brachytherapy

17
Q

Uterine Cervix

GEC-ESTRO MRI contouring for IGBT.

IR-CTV

A

HR-CTV + 1 cm (including initial tumor extension), minus OARs

18
Q

Uterine Cervix

Recommended brachytherapy dose to point A (EQD2 dose) for patients with stage IB to IV treated with EBRT?

A

80 to 90 Gy to point A or HR-CTV.

19
Q

Uterine Cervix

Recommended brachytherapy dose to IR-CTV (EQD2 dose) for patients with stage IB to IV treated with EBRT?

A

60 Gy

20
Q

Uterine Cervix

Dose constraint (EQD2) for the bladder using HDR brachytherapy?

A

90 Gy

21
Q

Uterine Cervix

Dose constraint (EQD2) for the sigmoid and rectum using HDR brachytherapy?

A

D2cc = 70 to 75 Gy

22
Q

Uterine Cervix

What are the optimal dose fractionation schedules for HDR brachytherapy?

A

28 ± 3 Gy in 4 to 5 fractions,

34 ± 4 Gy in 8 to 10 fractions,

or 40 ± 5 Gy in 12 to 14 fractions at point A

(Arai et al.)

23
Q

Uterine Cervix

What is the EQD2 of 7 Gy x 4 fractions of HDR brachytherapy?

A

40 Gy

24
Q

Uterine Cervix

What is the EQD2 of 6 Gy x 4 fractions of HDR brachytherapy?

A

32 Gy

Ph RadOnc Residency PBRROE2-3 Review 2021 (57 decks)

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