What is isodose curve in radiotherapy?
An isodose curve (or contour) is a line of constant absorbed dose. The line is in a plane and, for single radi- ation beams, its value is usually related by a simple percentage value (e.g., 90 percent, 80 percent, etc.) to the peak absorbed dose (or the surface absorbed dose, for x rays below 400 kV) on the beam axis.
What is isodose surface?
: of or relating to points or zones in a medium that receive equal doses of radiation.
What is isodose planning?
An isodose plan is a graphic display of patient’s anatomy to include the distribution of radiation based on a prescribed dose and plan of care created by a radiation oncologist.
What is SSD in radiotherapy?
Purpose: Source to surface distance (SSD) plays a very important role in external beam radiotherapy treatment verification. In this study, a simple technique has been developed to verify the SSD automatically with lasers. The study also suggests a methodology for determining the respiratory signal with lasers.
What is its significance of isodose curve to radiation therapy treatment planning?
The curves are usually drawn at regular intervals of absorbed dose and may be expressed as a percentage of the dose at a reference point. Thus, the isodose curves represent levels of absorbed dose in the same manner that isotherms are used for heat and isobars, for pressure.
What is gradient index in radiotherapy?
A dose gradient index (GI) is proposed that can be used to compare treatment plans of equal conformity. The steep dose gradient outside the radiosurgical target is one of the factors that makes radiosurgery possible.
What is the difference between SSD and sad in radiotherapy?
Modern photon beam radiotherapy is carried out with a variety of beam energies and field sizes under one of two set-up conventions: a constant source to surface distance (SSD) for all beams or an isocentric set-up with a constant source to axis distance (SAD).
How do you calculate gradient index?
Gradient Index: GI = PIVhalfPIV where PIVhalf is the prescription isodose volume, at half the prescription isodose and PIV is the prescription isodose volume.
Why do we use wedge filters?
Wedge filters can be used to restore dose uniformity in the treatment volume when limited arcs are employed.
Should treatment planning with isodose curves be mandatory for small field sizes?
Thus, treatment planning with isodose curves should be mandatory for small field sizes. In the case of 60Co, the isodose curvature increases as the field size becomes overly large.
What is an example of an isodose curve?
For example, the isodose curve at depth of Dmaxis 72%, indicating that the wedge factor is already taken into account in the isodose distribution. If such a chart is used for isodose planning, no further correction should be applied to the output.
What is the isodose curve size of a flattening filter?
Great caution should also be exercised in using field sizes smaller than 6 cm in which a relatively large part of the field is in the penumbra region. Depending on the source size, collimation, and design of the flattening filter, the isodose curves for small field sizes, in general, tend to be bell shaped.
What are the three parameters that affect isodose distribution?
PARAMETERS OF ISODOSE CURVES Among the parameters that affect the single-beam isodose distribution are beam quality, source size, beam collimation, field size, SSD, and the source to diaphragm distance (SDD). A discussion of these parameters will be presented in the context of treatment planning.