Final Exam

Question 1

For TMR, where is the field size measured?

Answer 1

at treatment SAD

Question 2

For TMR, where is the machine output measured?

Answer 2

at treatment SAD

Question 3

What is the TMR equation?

Answer 3

Tumor Dose/ (MO)x(Sc)x(Sp)x(TMR)x(any aborption factor)

Question 4

What is rotation therapy?

Answer 4

a treatment where the radiation source is moving around the patient during treatment

Question 5

What is a full rotation defined as?

Answer 5

traveling 360 degrees

Question 6

What a distance traveled less than 360 degrees?

Answer 6

Arc

Question 7

What is it called when isocenter is placed 2.0-2.5 cm beyond the middle of the tumor during partial rotation?

Answer 7

Past pointing

Question 8

Explain past pointing

Answer 8

During partial rotation, the isocenter is placed 2-2.5 cm past the middle of the tumor

Question 9

What is an Arc

Answer 9

a rotation less than 360 degree

Question 10

Define gantry speed

Answer 10

Monitor Units/Degrees in the arc (or rotation if 360 degrees)

Question 11

What is the Clarkson technique and its function?

Answer 11

Calculation utilized to adjust the scatter air ratio for irregular (blocked) fields

Question 12

What is the other name of the Clarkson technique?

Answer 12

Irregular Field Calculation

Question 13

What is the Clarkson technique equation?

Answer 13

TAR= TAR0 + SAR

Question 14

How many HVLs in order to transmit less than 5% of beam?

Answer 14

5 HVL

Question 15

In new linac, what device is utilized to shield normal tissue?

Answer 15

MLC

Question 16

What are the most cited irregular fields?

Answer 16

Mantle, Helmet and Inverted Y

Question 17

What does the mantle field treat?

Answer 17

All lymph nodes about the diaphragm

Question 18

What does the inverted Y field treat?

Answer 18

subdiaphrahmatic lymph nodes, can include spleen

Question 19

What does the helmet field treat?

Answer 19

whole brain and all/part of the c-spine

Question 20

What is cerrobend also known as?

Answer 20

Lipowitz Metal

Question 21

What is the composition of cerrobend?

Answer 21

Bismuth, Lead, Tin and Cadmium

Question 22

What is the ratio of cerrobend to lead?

Answer 22

1.25 cm of Cerrbond= 1 cm of lead

Question 23

What is the advantage of using cerrobend over lead?

Answer 23

lower melting point

Question 24

What is a negative block and give example?

Answer 24

Negative block is central opening and peripheral blocking, Ex. Electron cut out

Question 25

What is a Positive block and give example?

Answer 25

Positive block is central blocking and peripheral opening, Ex. Photon Block

Question 26

What is a divergent block?

Answer 26

blocks have slanted edges to mimic beam divergence

Question 27

What is a non-divergent block?

Answer 27

blocks have straight edges

Question 28

When projecting the size of the block on the film tray or tray, what type of relationship does it have?

Answer 28

Direct Proportion

Question 29

What is the most accurate modality to utilize for treatment planning?

Answer 29

CT Scan

Question 30

What are the three directions of a CT scan image?

Answer 30

Coronal, Transverse/axial and Sagittal

Question 31

What is the most commonly utilized beam modifying device

Answer 31

Wedge

Question 32

What is a universal wedge?

Answer 32

centrally mounted wedge, can accommodate all field sized

Question 33

What is an individualized wedge?

Answer 33

seperate wedge for each beam width, toe of the wedge aligns with field edge, used on Co60 machines

Question 34

What is a dynamic wedge?

Answer 34

wedge effect by varying dose rate and mechanical motion of the collimator during the treatment

Question 35

What is a wedge angle?

Answer 35

Angle through which an isodose curve is tilted at the central ray of a beam at a specified depth.

Question 36

What is the range of the wedge angles?

Answer 36

15-60 degrees

Question 37

What is the wedge angle formula?

Answer 37

90-(.5 x Hinge angle)

Question 38

What is a hinge angle?

Answer 38

angle between the central ray of two fields

Question 39

What is the optimum hinge angle formula?

Answer 39

180-(2 x wedge angle)

Question 40

What is the defintion of a gap or field separation calculation?

Answer 40

calculation done to match abutting fields at some depth to reduce cold/hot spots

Question 41

What is the gap calculation equation?

Answer 41

Gap= ((F1/2) x (Depth/SSD1)) + ((F2/2) x (Depth/SSD2))

Question 42

Electrons are generally used for what type of treatment?

Answer 42

boost

Question 43

What is the rule of thumb used to determine the electron isodose line coverage to the deepest part of a tumor?

Answer 43

``` Mev/4= 90% IDL Mev/3= 80% IDL Mev/2= 10% IDL ```

Question 44

What is the area of the 80-90% IDL called?

Answer 44

Therapeutic Range

Question 45

What is the area of the 10% IDL called?

Answer 45

Practical Range

Question 46

The therapeutic range covers what area?

Answer 46

80-90% IDL

Question 47

The practical range covers what area?

Answer 47

10% IDL

Question 48

What are isodose curves?

Answer 48

lines pass through points of equal dose in order to represent volumetric or planar variations in absorbed dose

Question 49

What are multiple isodose curves called?

Answer 49

Isodose chart

Question 50

What factors affect Isodose Curves?

Answer 50

Beam energy, Field Size, Source Size, Source Diaphragm Distance (SDD), AND Source to Skin Distance (SSD)

Question 51

What is penumbra?

Answer 51

the region at the edge of a radiation beam where the dose rate change rapidly

Question 52

Penumbra is located between what range of IDL?

Answer 52

20-90% IDL

Question 53

What is the penumbra formula?

Answer 53

s(SSD+depth-SSD)/SDD

Question 54

What is GTV and what does it include?

Answer 54

Gross Tumor Volume and Tumor or demonstrable disease extent

Question 55

What is CTV and what does it include?

Answer 55

Clinical Tumor Volume and GTV + Subclinical disease

Question 56

What is PTV and what does it include?

Answer 56

Planning Target Volume and CTV+ margins for setup uncertainties and patient/organ motion