Often used when the depth of the target is uncertain.

Dosimetry Parameters

It can also be used to compensate variations in contour surface contour to eliminate air gaps in cavities.

Cerrobend (lipowitz metal) melting point is what?

Sizes of wedges

Wedge Placed 15 cm from what

used in cobalt

As the distance between the skin and compensator increase the thickness ratio what?

Frequently employed in treating large fields.

High dose areas can be avoided by using a multiple field arrangement in which all beams encompass the target include different areas of surrounding normal tissues.

Three field technique is for what organs

Also often used during a portion of disease of the brain, pelvis, head and neck, lungs, pancreas, and extremities.

Is the volume of tissue that receive a dose considered significant in relation to tissue tolerance.

Shielding blocks thickness

Compensator consideration

Placed in the head of treatment unit, thus modifying the radiation beam to accommodate the contour of the patient.

Used to shape photon or electron fields, take several forms. Materials range from spent uranium to lead to lead alloys.

Types of beam modification

Can be designed to produce uniform dose distributions.

Bolus of a thickness equal to the depth of maximum dose eliminates WHAT of megavoltage photon beams.

Treatment preparation

As the distance between the skin and compensator what? the thickness ratio decreases

It is really just a variation of SAR and, like SAR, is mainly used in calculation of scattered dose in phantom or tissue.

More reproducible

Contains the tissues that are to be irradiated to a specific dose according to a specified time-dose pattern.

Full shielding blocks are constructed to transmit how much of the original beam

The acceptability of treatment plan depends not only on the dose distribution but also on:

Is the volume enclosed by an isodose surface, selected and specified by radiation oncologist as being appropriate to achieve the purpose of treatment.

Cadnium transmit how many percentage

It represents points of equal dose.

Shielding blocks how much at 20 degrees

It is define as the ratio of the dose at a specific point in tissue or in a phantom to the dose at the same distance in the beam at a reference depth, usually 5 cm.

Wedges are made of

Types of beam modification devices

Two types of shielding blocks

Originally designed to be used in the treatment of small shallow tumors..

The setup accuracy of a treatment may be better with what?

Multiple angled fields are possible to set up.

The target volume extends throughout a particular area treated.

Leadtransmit how many percentage

Wedges

Is defined as the ratio of dose on the central axis at Dmax to the dose at the same point in air.

Special beam modifiers where shadow trays made from lucite are kept at a certain distance from the skin

It is based on the measurement of the temperature rise of a given volume element of this instrument when it is exposed to a source of radiation.

Fricke dosimetry also called as

as been applied to measure relative dose distributions in an anthropomorphic polystyrene breast phantom having cork lungs, simulating a radiation therapy treatment with 6 MV opposing tangential beams. ... These results demonstrate that film dosimetry is a useful tool for treatment planning verification.

Wedge Placed how much from the skin surface

Box technique is for what organ

also called ferrous sulfate dosimetry, is one of the most useful chemical dosimeters in existence. This dosimetry technique depends on the oxidation of ferrous ions (Fe2+) to ferric ions (Fe3+) by ionizing radiation

Important factors to consider in choosing single field

Risks of tumor miss are reduced.

Certain beam angles are prohibited due to the presence of critical organs in those direction

Compensator devices

Probably the most commonly used field of arrangement.

Arc Treatment

The gross palpable or visible/demonstrable extent and location of malignant growth.

Shielding blocks 9.4 g/cm3 at how many degrees

Often used to treat metastatic disease in various sites.

Is a special case of TPR where the reference depth is chosen to be at Dmax.

What field is box technique

Allow to transmit of predetermined percentage of the treatment beam to a portion of the treatment field and may be used throughout the course of the treatment.

Rotation therapy

The used of these is use to alter the dose distribution in beam.

The incidental irradiation of large volume of normal tissues situated within the fields

Bismuth transmit how many percentage

provides a real advantage to radiation therapy departments in that it allows rapid and easy calibration of output at the end of treatment cones.

Output measured without a scattering phantom, sometimes referred to as in-air, increases with increase in field size.

Superficial targets

It is define as the ratio of the dose at a specific point in tissue or in a phantom to the dose at the same distance in the beam at a reference depth, usually HOW MUCH

It is designed to change the isodose curve relative to the beam axis at specified depth to the patient. Wedge reduce the dose in areas of overlap between fields that have hinge angles. Less than 180 degrees.

Refers to the material whose interactions with radiation beam mimic those tissue.

Typical Field Arrangement

Skewed dose distribution.

Individual wedges - used in what?

Define as the ratio of the dose rate at the depth maximum dose for the reference field size to the reference field size.

Used to shape photon or electron fields, take several forms. Materials range from spent what

Tin transmit how many percentage

Its melting point 165 degrees F (74 degrees Celsius)

It is the ratio of the scattered dose at a given point in a medium to the dose in air at the same point.

Combining Fixed and Moving-beam Technique.

It is the ratio of the dose at a given point in a medium to the dose at the same point in the free space

Field blocking shaping filters

In wedge x and y is what

The dimension and shape of the compensator must be adjusted to account for

is the best technique for absolute and direct measurement of absorbed dose.

Absorbed dose measurement methods

Is a tissue volume a demonstrable GTV and/or subclinical microscopic malignant disease must be eliminated.

It is the absorbed dose at a given depth expressed as a percentage of the absorbed dose at reference depth on the central axis of the field.

Bolus devices