What is DMAX in radiation therapy?
What is DMAX in radiation therapy?
When a radiation beam interacts with tissue, a certain depth of tissue is required before we see the maximum amount of radiation (maximum dose or dmax). This region is called the build-up region and is responsible for the skin sparing effect.
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).
What is a vertex field radiation therapy?
Conclusions: When a vertex field is used for the treatment of the brain tumors, the entire axial length of the body is irradiated which adds to the integral dose. Unlike the scattered and leakage radiation, the primary dose to extracranial critical organs is greater for higher energies.
What is sad technique in radiotherapy?
The source-axis distance (SAD) is a treatment machine design parameter that affects integral dose, dose rate and patient clearance. The aim of this work was to investigate the effect of source-axis distance on integral dose for conformal arc therapy.
What is an isodose curve?
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 four field box technique in radiotherapy?
Abstract. Background: The advantage of 4-field radiation to the pelvis is that the use of lateral portals spares a portion of the small bowel anteriorly and rectum posteriorly. The standard lateral portals defined in textbooks are not always adequate especially in advanced cancer cervix.
What is SSD in radiation?
• SSD is source-surface or source- skin-distance. • SAD: distance from the source of the. radiation to the axis of the beam or.
What is Gap correction in radiotherapy?
Commonly, gaps in radiotherapy are offset by finishing courses faster, delivering some. remaining fractions twice-per-day or at the weekend as described in section 5.2 of the RCR. report. This is the most effective approach and should be used when possible (Hendry et al, 1996).
What is wedge angle in radiotherapy?
According to the International Commission on Radiation Units and Measurements, the wedge angle is defined as the angle at which an isodose curve is tilted at the central axis of the beam at a specified depth (usually 10 cm) [5].
Does PDD increase with field size?
It was found that the values of PDD0 increase as field size increases. The percentage depth dose at surface (PDD0) for open beams, at 80 cm, 100 cm, and 120 cm FSDs were 13.89%, 11.71%, and 10.74%, respectively, for a 10 × 10 cm2 field.
How is PDD measured?
PDDs were measured at 100 cm source-to-surface distance (SSD), for fields of size: 5 cm × 5 cm, 10 cm × 10 cm, 20 cm × 20 cm, 30 cm × 30 cm, and 40 cm × 40 cm. PDDs were measured at all available dose rates for 6 FFF and 10 FFF as PDD curves smoothing vary with dose rate.