What is small field dosimetry?
Small fields are usually defined between 4 cm × 4 cm and 0.3 cm × 0.3 cm. [1,2] Using such field sizes can cause uncertainty in dosimetry; therefore, special attention is required in both dose calculations and measurements.
What is a small field?
Small fields are those meeting the following conditions: 1. Lack of lateral charged particle equilibrium, even along the central axis. When the range of secondary electrons is approximately equal to or greater than the distance from field edge to central axis, lateral charged particle equilibrium cannot exist.
What is a small field in radiotherapy?
Such so called ‘small field’ radiation is used to treat smaller tumours in the early stages of cancer, as well as larger ones whose treatment requires differentiated intensity of the radiotherapy to deliver varying doses to various parts of the tumour.
What are treatment fields?
Listen to pronunciation. (TREET-ment feeld) In radiation therapy, the place on the body where the radiation beam is aimed.
What is field in field radiation?
The “Field in Field” technique is an often used alternative to the use of wedged fields in tangential irradiation for the treatment of breast cancers. The technique employs small fields, often only a few centimeters in diameter with small numbers of monitor units, frequently as few as five.
What are the different types of dosimeter?
There are two general types: dosimeter badges, which are used to measure cumulative doses over periods of weeks or months, and pocket dosimeters, which are generally used for monitoring over a shorter term.
What is Field in Field?
What is field size in radiotherapy?
field size is defined as “the projection, on a plane. perpendicular to the beam axis, of the distal end of the. collimator as seen from the front size.”
What are dosimetric quantities?
It is a physical quantity to measure radiation energy absorbed by unit mass of materials. Definition: Energy absorbed per unit mass of the material Unit: Gray (Gy)
What does field size mean?
Field size means the dimensions along the major axes of an area in a plane perpendicular to the central axis of the useful beam of incident radiation at a normal treatment distance and defined by the intersection of the major axes and the 50 percent isodose line.
What is field in radiation therapy?
What are the conditions for small field dosimetry?
Small field is a condition where dosimetry is usually difficult due to electronic disequilibrium Use of IAEA/AAPM protocol for reference and relative dosimetry based on Alfonso et al (2008) is recommended Focal spot of a machine is a critical parameter in small field dosimetry Absolute dosimetry protocol for small field is forthcoming
What is the best dosimetry protocol for small field?
Summary Small field is a condition where dosimetry is usually difficult due to electronic disequilibrium Use of IAEA/AAPM protocol for reference and relative dosimetry based on Alfonso et al (2008) is recommended Focal spot of a machine is a critical parameter in small field dosimetry Absolute dosimetry protocol for small field is forthcoming
What is the goal of dosimetry?
The goal of reference dosimetry is to establish the output, in absorbed dose per monitor unit (cGy/MU) of the reference field. The reference field is 10 x 10 cm 2 for machines able to produce such a field.
What is considered a small field size?
Conventional simplification: although not technically a correct definition, a rule of thumb is that fields become “small” when they are less than 3 x 3 cm 2. Key Point: Small fields are defined both by the actual field size and by the size of the detector used to measure the field!