الفهرس 
Theoretical AspectsOnly 14 pages are availabe for public view
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Abstract
Recently, in radiotherapy the linear accelerator is used with high
energy of photons. This high energy sometimes reaches to 25 MV. The
high photon energy produces neutrons when strike by a heavy metal like
tungsten, led and iron due to nuclear reaction this phenomenon is called
photoneutron. The induced photoneutron is considered undesirable dose
delivered to both of tumor and healthy organs of patient, so this requires a
degree of accuracy during the treatment to get the lowest possible hazard
to the healthy tissues around the tumor. For that reason, the detection of
the induced photoneutron inside the room at different points is a must in
order to know the energy of it and the achieved doses. According to the
energy spectrum of neutrons must measuring more than one energy of the
induced photoneutron.
In this work we used two techniques for neutron dosimetry; the first one
isThermoluminescence dosimetr and the second is Solid State Nuclear
Track Detection. from TLD using two dosimeters of lithium fluoride that
differ in the isotopes of lithium (6Li and 7Li). The two types of TLD have
been irradiated to gamma source (137Cs) where studying the correction
factor for each dosimeters sensitivity, and also the effect of pre irradiation
reading on the response curves for each type of dosimeter. In addition to
that, a Study was made on the method of calculation for the glow curves
to be satisfied in radiotherapy room such as total area under the curve,
dosimetric region and the maximum height of the dosimetric peak (P5).
3
The study with (SSNTD) was performed using CR-39 and a boron disk
was made from a material enriched with 10B which have highly cross
section with thermal neutron giving alpha particle detected by CR-39, so
bare CR-39 bare was used to detect fast neutron and CR-39 covered with
boron to detect thermal neutron .
We designed a dosimeter that consists of four components CR-39 bare,
CR-39 covered with boron, TLD (600+700) bare and TLD (700+600)
covered with Cd sheet. This samples were irradiated to neutron source
(241Am-Be) to get conversion curves to dose inside radiotherapy room.
The designed dosimeter which consists of four components were
irradiated at radiotherapy room to Elekta Precice 15 MV inside solid
phantom at different positions and at the maze of the treatment room. The
measuring doses at the points which represent the healthy tissues were
high in comparison to the maximum permissible dose for healthy tissues.
Therefore, the shield to the induced photoneutron must be made during
the treatment in order to reduce the risk dose as much as possible