Treatment Planning for Board Study
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What is the correction factor for air/lung___, bone____, and normal tissue____
How many HVLs dose a photon block need to be?
As electron energy increases, skin dose
True or False
Setting up to bolus will help you NOT to have to worry about correction factor
As you increase field size but keep your monitor units the same, what happens to the dose being measured and why
dose will increase because even tho the MU stay the same, the fs increased which means more scatter which means the dose increased
In order for a block to have as little penumbra as possible, the block edge must be
Most common used contrast for MRIs
When field size increases, monitor units
decrease because we have more scatter and do not need more monitor units since the dose will increase via scatter
As field size decreases, the monitor units need to
increase because there is less scatter
Iodine contrast media is toxic to what organ?
- This is why docs will sometimes order a BUN or Creatine test to test the strength of the kidneys 1st
As slice thickness decreases, noise will
- Image will be grainer. You can increase the MAs to correct it, but then the patient will receive more dose.
Rotational arc tx time/monitor units are calculated using which method?
Why will tissue inhomogeneities like air cavities, lung, fat, and bone alter the dose distribution?
because any tissues without the same density as water may alter the dose
Back scatter factor depends on the ____and _____but is independent of
1st objective in tx planning is to determine ____ ____ and ____ ____
- tumor boundaries and
- critical structures
What is administered to the peritoneal cavity in the tx of gyno malignancies?
NTTD (normal tissue tolerance dose) is affected by 2 factors
Volume and fraction size
What is GTV and 1. cm of margin
reticule is also called the
The ____ is a source of electrons and the ____ stops the electrons
Positive or negative
- Cathode is negative
- Anode is positive
The # of electrons which pass from the cathode to the anode represents the ____ ____ and is measure in _____ and the potential difference between the cathode and the anode is measured in ____
- tube current
- mA (milliampere)
- kV kilivolts
What is barium sulfate commonly used for
- used to outline the GI tract (orally or rectally) and most often used for
- small bowel
- oral cavity
Iodine contrast is typically used for
list the symptoms of anaphylactic shock
- difficulty breathing
- abnormal (high pitched) breathing sounds
- Treat with epinephrine which will open up the airways and raise the blood pressure by constricting blood vessels
by subtracting the SSD from the SAD you can solve for
- isocenter location
- SSD-SAD= ioscenter depth
How would the wedge be positioned for an AP/PA Larynx treatment?
The heal would be anteriorly positioned to make the open area between the patient's chin and chest a virtual box, to help even the dose distributions.
When calculating Moving Rotational (SAD) fields, ____ is the calculation of choice
BSF is the ____ at dmax
T or F
Increase in beam energy will decrease the BSF, due to the forward motion of the beam.
What is defined as the ratio of dose on the CAX at dmax to the dose at the same point in air?
What is defined as the ratio of absorbed dose at a given depth in phantom to the absorbed dose at the same point in free space?
As TAR increases, depth will
Would you use TMR or TAR for irregular field calculations?
TMR because you are measuring the ratio of dose anywhere and comparing it to dmax.
You wouldn't use TAR because that only compares the ratio of absorbed dose to the dose at the same point in free space.
____ is the calculation of choice for isocentric field calcs and ____ is the calculation of choice for SSD (non isocentric) calcs
SDD and SCD are the same thing and is defined as
the distance along the beams axis
an Increase in SCD/SDD will____ Penumbra
Why do we use the Mayneord's factor
to calculate the change in PDD for small fields
The wedge transmission factor: the filter ____ the machine output
The ___ ____ is the angle, in which an isodose curve is tilted at the cax of the beam at a specified depth
The ___ ___ is the ratio of dose with and without the wedge at a point in phantom along the beams CAX
What does a larger focal spot do to the penumbra?
increases the penumbra
The width of the penumbra depends on what 3 things
- field size
- collimator size
Where on the beam is the highest portion of dose?
- on the CAX
- the dose is greatest at the cax and it decreases towards the edges of the penumbra.
smaller focal size will produce ___ and a larger focal spot size will produce ____
- a sharper beam edge
- decrease the sharpness of the beam's edge
The best way to make sure that the portal borders are accurate is to take a ____ ____. The best way to verify the isocenter is correct is to take _____ _____
- port films
- orthogonal films
_____ has a low melting point of 158- 163f and a high Z. blocks are used to attenuate primary radiation to _____ of the unblocked beam intensity
what does cerrobend contain and how much
- Lead- 26.7%
- Tin- 13.3%
- cadmium- 10%
The effective energy of the beam increases as it passes through the filter due to
Increase the collimator setting and it will ___ scatter
isodose shift method is used to correct for ____ _____
photoelectric effect will be accompanied by a ____ ____ emission
what defines the beam
The creation of a positron results from
TLD releases stored energy as ____ when heated
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