Finals Material Flashcards by Lan Chau

What do the initials in the following acronyms stands for:

GTV, CTV, PTV

GTV: gross tumors volume
CTV: clinical target volume
PTV: plan target volume

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Which term/acronym is the volume which accounts for organ movement and setup uncertainties

PTV

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This type of technique gives the shape of a diamond

“crossfire” technique which is 2Ap obliques and 2 PA obliques

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2 EQUALLY weighted parallel opposed AP-PA fields will give a shape of :

An hour glass

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AP-PA and a right and left laterals are nicknamed what

4 field “box” or “brick”

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Prior to the availability of IMRT- a technique using AP,RPO, LPO fields were frequently used to treat what area

Cervical esophagus

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A 3 field recital cease use PA and right and left laterals with wedges. The wedges should be placed with the ______ towards the posterior of the patient’s anatomy

Heel towards the posterior of the patient anatomy

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A wedge technique may be used on breast tangents. To compensate for the slope of the breast, where would the heel of the wedge be placed

Towards the nipple

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Name the technique which was used for ovarian cancer- total abdomen, pelvis, and sub diaphragmatic lymph nodes

Moving strip technique

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Next the 2 factors which affect the Roentgen to cGy conversion factor

Density of the irradiated material (Z)

Energy of the beam

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Lines that connect points of equal dose are called

Isodose curves

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Name any 2 factors which affect the shape of the isodose chart

Field size

Beam energy

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The point which is labeled 100% on an isodose chart is called

Normalization point

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The point labeled 100% for a treatment which uses MORE THAN ONE BEAM (FIELD) is generally placed where

At the isocenter

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What is the most accurate method to measure a radiation beam and create an isodose chart

Ionization chamber

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The rapid fall off of dose at the edge of the beam is called

Penumbra

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Formula for TAR

TAR= TAR0 + SAR

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When doing the clarkson calculation on a blocked field, which part of the TAR value is being “adjusted”

(Sc) for the lack of scatter

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TARo denotes the tissue air ratio value for field 0x0. This field size indicates the field from the portion of the beam created when the electrons hit the target. This is called the _____ beam

Primary

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The blocked equivalent square can also be called

Effective field size

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Write the 3 metals which makes up the Thoreaus filter in order from the tube to the patient

Tin (Sn), Cooper (Cu), Aluminum (Al).

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Tissue air ratio (TAR) at Dmax is also known as

Back scatter factor

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TAR is NOT dependent on

SSD

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When using either TAR or TMR for monitor unit calculations, the field size and machine output are measured at what distance

100 cm- SAD

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The ratio of dose at depth compared to the dose at Dmax when bOTH measurements are take at the same distance from the radiation is defined as

TMR- tissue maximum ration

Cherry end is a lead alloy and consists of what 4 metals

Lead, tin, bismuth, and cadiminum

In order to ensure adequate shielding of normal tissue s, the thickness of a block or MLC must be at least how many HVL thick

5 HVL thick

If the treatment is given through a "hole", in the block, like an electron cutout, this type of block is called

A negative block

If the Gantry rotates 360 while the radiation beam in on, this type of treatment is called

Rotational therapy

Name the radiation field which treats the lymph nodes ABOVE the diaphragm

Mantle field

How many centimeters of cerobend are needed to have the Same shielding ability as 1cm of pure lead

1.25

Name the machine which uses Thoreaus filter

Orthovoltage machine

PDD compares the dose at some depth to the dose at ___

Dmax

Sc and Sp correct for the change in scatter when the field size is different than the reference field size. What is the reference field size?

10x10

Sc is _____ than 1 when the treatment field size is larger than the reference field size

Greater than

Sp is ____ than 1 when the treatment field size is smaller than the reference field size

Lesser than

When using PDD to calculate the correct number of MU to deliver the prescribe tumor dose, the machine output (aka reference dose rate) used must be know at what distance from the radiation source?

Treatments SSD and Dmax depth

Field size will ____ as PDD increase

FS increase as PDD increase

PDD ____ as you go deeper into the patient

Decreases

When using PDD to calculate the correct number of MU to deliver a prescribe dose, where is the field size measured

On the skin surface

The PDD value at Dmax for any field size ,beam energy, or SSD is equal to

100% or 1

As beam energy increases, what happens to PDD

Energy increase, PDD increases

As field size increase, what happens to PDD

FS increase, PDD increase

As SSD increase, what happens to PDD

SSD increase,PDD increase

As you go deeper into the patient, what happens to PDD

Deeper, PDD decrease

Mayneord factor is an application of which law

Inverse square law

When would you use sterling formula (aka equivalent square)

When the treatment fields are not square field size. So this is an estimate of a rectangle to a square

If the SSD decreases, how would this affect the back scatter factor

SSD does NOT affect BSF

List in order from the MOST to the LEAST penetrating beam machine (Gorillas Can Swing Over Short Mountains)

``` Megavoltage - MOST Supervoltage Orthovoltage Superficial Contact Grenz Ray ```

Which machine type uses 10-15kVp beam

Grenz Ray

Which machine toe measured its HVL in millimeters of Copper

Orthovoltage

Which machine type uses beam energy greater than or equal to 1000kVp

Megavoltage

This is the intersection point of the Collimator axis and the gantry axis of rotation

Isocenter

Unit of exposure in air

Roentgen (R)

This distance between the patient skin and the depth of max ionization (Dmax) is called

The build up region

Tissue equivalent material is called Bolus. Examples includes

Wax Superfluous Water

The most frequently used beam modifying device is

Wedges

The standard range of wedge angle is from ___ to ____

15 degrees to 60 degrees

When the upper Collimator moves during the treatment and gives a "wedge effect". This type of wedge is called

EDW- enhance dynamic wedge

Name the type of wedge which is generally used on a Cobalt 60, where it's toe is aligned at the field edge and there is a separate wedge for each field width

Individual wedge

In order to Make up for the lack of tissue and maintain skin sparring, what can be used to account for a sloping skin surface

Compensators or wedges

The area where there is a lack of tissue is called

Air gap

Identify the factor which adjusts the PDD when the treatment SSD is different than the SSD used to measure PDD table

The Mayneord Factor (F)

" f " factor is the roentgen to cGy conversion factor and is affected by

Density of irradiated material | Beam energy

How do you calculate dose using " f" factor

(Exposure R)(f of the material)

Point where maximum absorb dose occurs for a single photon field

Dmax

What is the Dmax for cobalt 60

0.5cm

What is the Dmax for 6MV

1.5cm

What is the Dmax for 10Mv

2.5cm

What is the Dmax for 18Mv

3.5cm

Dmax is affected primarily by

Beam energy

Dmax occurs at the _____ for low energy

At the skin surface

Dmax occurs _____ for high energy

Beneath the skin surface

The distance between the patient skin surface and Dmax

Build up region

Blade pairs capable of independent movement

Asymmetrical jaws

PDD field size is measured on the

Skin

The amount of radiation coming from the machine at a specific distance

Reference dose rate

(Roentgen)x(BSF)x("f" factor) is the machine output for

Low energy machines like orthovoltage

Amount of radiation scattered "back", adding to the skin dose

Back scatter factor

For energies with HVL greater than 1mmCu, BSF

Decreases due to more forward scatter

Increase in FS cause an ______ in BSF

Increase FS cause increase n BSF due to more tissue being covered

The Mayneord factor is used when

There is a change in SSD

As FS increase, TAR

Increase

As energy increase, TAR

Increase

As you go deeper into the patient, TAR

Decrease due to moving further away from the source

As SSD increase, TAR

Is not affected. SSD does it change TAR

Blocks must be at least _____ thick to allow for less than 5% transmission

5HVL

Cerrobend is made of | Bacon, lettuce, tomato with cheese

Bismuth Lead Tin Cadmium

Main advantage of cerobend

Low melting point

Divergent blocks have ____ edges

Slanted edges

Non divergent blocks have ___ edges

Non slanted edges

Positive block treats ____

Around.

Negative blocks treats _____

Through the hole

This technique is used to treat BELOW the diaphragm

Inverted Y

Clarkson calculation is also called

Irregular field calculation

Clarkson calculation is done for

Calculation to correct for the lack of scatter due to blocking

Isodose curves is measured by

Radiographic films Solid sta detectors (TLD ) Ion chamber (most reliable)

Factors affecting isodose charts

Energy FS SSD Source size

For a single field, the normalization point is placed at

Dmax

For multiple fields, the normalization point is placed at

The isocenter

Isodose shift methods is used for

Sloping skin surface

MLC and cerobend modify the ____ of the beam

Shape of the beam

Wedges modify the ____ of the beam

Shape of the beam and changes the whole isodose chart

Angle through which an isodose curve is tilted at the central Ray of the beam

Wedge angle | 90- (.5hinge)

Angle between the central Ray of 2 beams

Hinge | 180- (2 x wedge)

Type of wedge that accommodates all field size

Universal wedge

Contours are measurements of the patient both ____ and ____

Internally and externally

The most accurate method of obtaining a patient contour

CT Scan