It follows that
RBE cannot be a constant value
when taken in the context of the complexities of different tissues within the human body, the heterogeneity of cancer types, and the wide variety of doses used as well as the degree to which Bragg peaks are shifted or mixed with lower LET regions.
What effect does RBE have?
The RBE is an empirical value that varies depending on the type of ionizing radiation, the energies involved, the biological effects being considered such as
cell death
, and the oxygen tension of the tissues or so-called oxygen effect
What is the effect on RBE as LET increase?
Linear energy transfer
What is RBE in radiotherapy?
AbstractID: 11865 Title: Biological aspects of heavy charged particle radiation therapy. The
relative biological effectiveness
(RBE) is defined as the ratio of the doses required by two radiations to cause the same level of effect. Thus, the RBE depends on the dose and the bio- logical endpoint.
How does RBE depend on LET?
It describes the action of radiation into matter. It is identical to the retarding force acting on a charged ionizing particle travelling through the matter. By definition, LET is a positive quantity. … Hence
nuclear stopping power is not contained in LET
.
Why does OER decreases as LET increases?
The OER decreases with increasing LET, because
in the dense tracks there is more direct action and less chance of indirect interactions with molecules external to the track
(see Chapter 7.01).
ARE LET and RBE directly proportional?
A paper by Takatsuji et al. discusses the relationship between LET and RBE for certain chromosomal aberrations and cell death: it states that at low doses the RBE varies as about the square of the LET, the RBE value peaks at an LET of about 100 keV μm
– 1
, and then the
RBE decreases as LET increases further
.
Which type of radiation has the largest RBE?
The types R of ionizing radiation most considered in RBE evaluation are
X-rays
and gamma radiation (both consisting of photons), alpha radiations (helium-4 nuclei), beta radiation
Why do beta and gamma have same RBE?
The gamma radiation itself is much more penetrating than alpha or beta radiation
How do you calculate RBE?
RBE is calculated as
a ratio of the reference radiation dose to the dose of the test radiation
(ICRP, 2003): 3. However, the value of RBE varies depending on the level of effect being considered (Fig 1). The ratio Dγ High/Dn High may be different from Dγ Low/Dn Low.
What type of radiation is used as a standard for determining the RBE?
Although
250 kVp X-ray
was the common standard radiation to determine the RBE, the International Commission on Radiation Protection (ICRP) recommended in their 92
th
report to use gamma rays of
60
Co as reference radiation (3) and therefore was chosen as reference in this study.
What is protraction and fractionation?
Definitions Fractionation: the total dose to deliver is divided between several sessions (fractions). It is characterised by the dose per session and the number of sessions. Protraction:
total duration of the treatment
(number of days between the 1st and last session).
Why is oxygen enhancement ratio OER different from high and low LET radiation?
The Oxygen Enhancement Ratio (OER) or oxygen enhancement effect in radiobiology refers to
the enhancement of therapeutic or detrimental effect of ionizing radiation due to the presence of oxygen
. … Radiation with higher LET and higher relative biological effectiveness (RBE) have a lower OER in mammalian cell tissues.
When should I raise my RBE?
Don’t take it only when
your symptoms are
especially bothersome, or when you’re about to have a big event or take a long car ride. Take it with water and swallow the tablet whole. Do not chew, break, or crush the tablet. You can take Myrbetriq with or without food.
What is high LET radiation?
High LET radiation includes
particles with substantial mass and charge such as alpha particles
. Low energy neutrons, which carry no electrical charge, are also a high-LET radiation. The distribution of energy in cells has a marked influence on the amount of biological damage done by a fixed amount of radiation.
