Treatment Planning Flashcards

According to ICRU Report 62, which volume adds a margin to the CTV for physiologic motion such as breathing?

Answer: Internal target volume (ITV)

The ITV is the CTV plus an internal margin for changes in the target's size, shape and position.

ICRU Report 83 recommends reporting which dose as the 'near-maximum' dose?

Answer: D2%

D2%, the dose received by 2% of the volume, replaces the point maximum as the near-maximum dose.

The ICRU 83 homogeneity index is calculated as:

Answer: (D2% - D98%) / D50%

HI = (D2% - D98%)/D50%, and a value closer to zero means a more uniform dose.

The RTOG conformity index is defined as the:

Answer: Prescription isodose volume divided by the target volume

The RTOG CI is the volume covered by the prescription isodose divided by the target volume, with 1.0 as the ideal value.

A margin added around an organ at risk to account for its motion and setup uncertainty creates the:

Answer: PRV

The planning organ at risk volume (PRV) is the OAR plus a margin, which is commonly used for serial organs like the spinal cord.

ICRU Report 50 recommends that the dose across the PTV stay within:

Answer: +7% and -5% of the prescribed dose

ICRU 50 recommends PTV dose homogeneity between 95% and 107% of the prescription.

The PTV margin is made up of the internal margin plus the:

Answer: Setup margin

The PTV adds a setup margin to the ITV for daily positioning and machine uncertainties.