What is penumbra in radiotherapy?
What is penumbra in radiotherapy?
In external beam therapy, radiation penumbra is one of the factors which hinder the confinement of the dose to tumour volume and cause unnecessary irradiation of the surrounding normal tissues in the penumbral region.
What is geometric penumbra?
The region, near the edge of a radiation beam, where the dose changes rapidly according to the distance from the beam axis is known as the penumbra. Transmission penumbra is the region irradiated. by photons which have traversed a part of a col- limator. Geometric penumbra is the region irradiat-
What are the 3 types of radiation treatment?
Radiation therapy can be given in 3 ways:
- External radiation (or external beam radiation): uses a machine that directs high-energy rays from outside the body into the tumor.
- Internal radiation: Internal radiation is also called brachytherapy.
What is a wedge in radiotherapy?
In radiation therapy, wedge filters are commonly used to improve dose uniformity toward the target volume [2]. A physical wedge is usually constructed from a high-density material, such as lead or steel, which attenuates the beam progressively across the entire field.
Why does geometric penumbra occur?
Geometric penumbra originates from the radiation source when it is not a single point. Transmission penumbra occurs when the beam passes through the edge of the jaw or MLC before it reaches the full attenuation point of the jaw and the MLC.
What affects penumbra?
Various factors such as source size, collimator to isocenter distance (CID), source to collimator distance (SDD), photon beam energy, field size and depth, affect the penumbra width (Farrukh et al., 2017).
What is the difference between radiation and radiotherapy?
Radiation therapy (also called radiotherapy) is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. At low doses, radiation is used in x-rays to see inside your body, as with x-rays of your teeth or broken bones.
What is virtual wedge in radiotherapy?
Virtual Wedge (VW) is a Siemens treatment modality which generates wedge-shaped dose distributions by moving a collimator jaw from closed to open at a constant speed while varying the dose rate in every 2 mm jaw position.
Why is bolus used in radiation therapy?
In radiation therapy, bolus is a material which has properties equivalent to tissue when irradiated. It is widely used in practice to reduce or alter dosing for targeted radiation therapy.
How do you minimize penumbra?
Penumbra width is decreased using compensating filter and intensity modulation technique. Penumbra width is improved by removing the flattening filter of linac. Increasing SDD results in decreasing geometric penumbra width. Penumbra width is increased by increasing depth and field size.
What is penumbra region in radiology?
Penumbra The rapid decrease at the edges of the radiation beam is called the penumbra region Usually defined as the space between the 80% and 20% isodose lines.
What is the penumbra in radradiation therapy?
Radiation Therapy (RT) Basics. Often, the 50% isodose line (defined as the geometric penumbra) is the standard for delineating the effective area of the beam. The light field that comes out of the linear accelerator indicates where the 50% isodose line will be.
What is the meaning of Penumbra?
Also found in: Dictionary, Thesaurus, Legal, Encyclopedia, Wikipedia. penumbra. 1. the part of a shadow in which there is a small amount of illumination from a light source. 2. blurring at the edges of a structure on a radiograph.
What is the difference between transmission penumbra and physical Penumbra?
Geometric Penumbra: Transmission Penumbra: variable transmission of beam through non divergent collimator angle. Physical Penumbra: the lateral distance between two specified isodose curves at a specified depth. ( lateral distance between 90%?10% or 80?20%)
