Midterm

Question 1

During___, px is positioned on table with appropriate treatment accessory & the table is raised & rotated under gantry.

Answer 1

Simulation

Question 2

a diagnostic x-ray machine
mounted on a rotating gantry which provides geometries
identical with those found on megavoltage therapy machines. can be used in either a radiographic or fluoroscopic mode to provide diagnostic quality images on film or a television I mc nitor respectively

Answer 2

Simulator

Question 3

• deals with the measurements of the absorbed dose resulting from interaction of lonizing radiation with matter.

Answer 3

Radiation Dosimetry

Question 4

• total nur iber of particles or photons per unit area of the interacting material

Answer 4

Fluence (w)

Question 5

Amount of lonization per mass of air due to x and gamma rays

Answer 5

Exposure ( x)

Question 6

Conventional unit & SI unit of Exposure

Answer 6

Roentgen ( R)
Coulomb /kg ( C/kg)

Question 7

1R=

Answer 7

2.58 ×10^-4 c/kg

Question 8

Amount of energy Imparted by radiation per mass

Answer 8

Absorbed Dose ( D)

Question 9

Conventional unit & SI unit of Absorbed dose

Answer 9

rad, Gy

Question 10

1 rad=

Answer 10

10 mGy

Question 11

100 rad

Answer 11

1 gy

Question 12

1 j/kg

Answer 12

1Gy

Question 13

A measure of radiation specific biological damage in man

Answer 13

Dose Equivalent ( H)

Question 14

Conventional unit & SI UNIT OF Dose Equivalent ( H)

Answer 14

rem
Sv

Question 15

1 rem=
100 rem

Answer 15

10 mSv
1 Sv

Question 16

Amount of radioactive material expressed as, the nuclear transformation rate
Conventional unit:
SI UNIT:

Answer 16

Activity ( A)
Ci
Bq

Question 17

1 Ci=

Answer 17

3.7 x10^10 Bq

Question 18

4 absorbed dose measurements methods

Answer 18

Calorimetry
Fricked dosimetry
Film dosimetry
Ionization method

Question 19

Involves measurement of radiation based on the change in the thermal energy per unit mass of the medium. It is based on the fact that almost all the energy deposited in the medium by the radiation beam eventually appears as heat within the medium. For water, 1 Gy produces a temperature rise of 2.4x 10-4 Calories/gram which can be measured usina a sensitive device called thermistors.

Answer 19

CALORIMETRY

Question 20

based on chemical changes caused by
radiation.

Answer 20

FRICKED DOSIMETRY

Question 21

When x-ray film is exposed to ionizing/ radiation. the exposed siver bromide crystals form a latent image. The degree of blackening of the film is proportional to the energy absorbed and is measured by determining the optical density with a densitometer.

Answer 21

FILM DOSIMETRY -

Question 22

measurement of radiation energy based on ion pairs produced in a given mass of medium

Answer 22

IONIZATION METHOD-

Question 23

2 chamber use for photon beam

Answer 23

Thimble and farmer

Question 24

chamber-used or electron beam

Answer 24

Markus

Question 25

4 Dosimetry Parameters

Answer 25

Dose Dose rate Monitor unit Isocenter

Question 26

a general term used to refer the effect on a material when exposed on radiation

Answer 26

Dose

Question 27

the radiation dose delivered per unit time

Answer 27

Dose rate

Question 28

unit used in linear accelerator to determine the those most linear accelerator is calibrated to 1MU= cGy

Answer 28

Monitor unit

Question 29

a point in space where the x y and z axis intersect

Answer 29

Isocenter

Question 30

4 Modification to the Radiation Field

Answer 30

Bolus Compensation Thermoluminescence dosimetry Wedges

Question 31

-tissue equivalent material that have Electron Density, Physical Density, Atomic Number similar to that of tissue or water. It increases the dose to the skin. Ex. Paraffin Wax, Gauze soaked in water. "Super-Slab", Elastomeric Polymer

Answer 31

Bolus

Question 32

is intended to compensate for some topographical deficit. A balus placed in the tissue deficit of the patient is the simplest way to compensate, but since it diminishes the skin sparing effect, retracted tissue compensators are usually employed.

Answer 32

Compensator

Question 33

-constructed of brass, steel, or lead and when placed in the beam, progressively decreases in field intensity. A wedge bends dose distribution at a specified depth

Answer 33

Wedges

Question 34

an irradiated crystal stores a small fraction of energy in the crystal lattice. This energy can be recovered later as visible light when heated. The phenomena of releasing visible photon by thermal means is coined Thermoluminescence

Answer 34

Thermoluminescence Dosimetry-

Question 35

4 field arrangement in EBRT

Answer 35

SINGLE FIELD PARALLEL OPPOSED FIELD MULTI- FIELD ARRANGEMENT MOVING FIELD TECHNIQUE

Question 36

-simplest treatment and the dose distribution in tissue is represented in an isodose chart for the energy and field used - Electron is usually the radiation used to treat shallow tumors, where a rapid drop in dose beyond the 57 depths of the tumor

Answer 36

Single Field

Question 37

-pair of fields directed along the same axis of opposite sides of the treatment volume. Relatively easy to set up and to reproduce from day to day Isodose line is within the entire treatment volume.

Answer 37

Parallel Opposed Field

Question 38

ADVANTAGES of parallel field

Answer 38

-Simplicity and reproducibility of setup - Homogenous dose to tumor -Less geometrical miss chance

Question 39

DISADVANTAGES of parallel *

Answer 39

Excessive dose to normal tissues critical organs above and below tumors

Question 40

-directed at target volume requires that the beam entrance and exit of each field be aimed at different angles/segments. Reducing dose to adjacent tissues. -the___ technique is the famous multi-field arrangement, often used in pelvic malignancies. Composed of opposed posterior and anterior fields, and opposed right lateral and left lateral fields

Answer 40

Multi-field Arrangement box

Question 41

technique in which the axis of the therapy machine's rotation, the isocenter, is in the center of the target volume. Radiation source is moved around the Px through are, often in a complete circle. It yields a high dose in the target volume where the dose outside falls off rapidly

Answer 41

Moving Field Technique-

Question 42

-used to shield organs at risk, made of lead or Lipowit's metal (cerrobend) which consists of 13.3% Tin, 50% Bismuth, 26.7% Lead, and 10% Cadmium. The physical density of Lipowit's metal at 20 Celsius is 9.4 8/cm', compared with 11.3g/cm

Answer 42

BLOCKS

Question 43

Lipowit's metal _% Tin- Bismuth Lead& cadmium Density- cm ( 20 celcius)

Answer 43

13.3 50 26.7 10 9.48

Question 44

The chemical radiation dosimeter most commonly used in Fricked Dosimetry is____ which it is oxidized by radiation into ferric sulfate. Ferric Ion concentration is measured by absorption spectrometry at 224 nm and 304

Answer 44

Ferrous Sulfate

Question 45

For water, 1 Gy produces a temperature rise of___ which can be measured usina a sensitive device called thermistors.

Answer 45

2.4x 10-4 Calories/gram