الفهرس 
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Abstract
Radiochromic film dosimeters have wide-spread applications in radiation technology applications for γ-rays, X-rays and electron beam (EB) irradiation such as radiotherapy, blood irradiation and radiation processing of foods and medical devices. Radiation dosimetry is a very crucial tool for such applications. Thus, radiochromic film dosimeters have been developed for low- and high-dose monitoring in a wide radiation application for dose monitoring. Developing new types of films is due to the effort of looking for finding more reliable, more accurate, more stable, simple, and less expensive dosimeters. Many radiochromic films like GAFCHROMIC Dosimetry film media and radiation indicators are mostly depending on conjugated diacetylene monomers and polydiacetylenes polymers. Since these compounds are greatly sensitive to radiation and polymerize upon γ-ray exposure forming highly colored polyconjugated polymers, they are being successfully used in γ-rays and EB radiation dosimeters.
Continuous research and development in the dosimetry systems that allow full imaging of a radiation dose distribution especially in radiation therapy has led to the development of radiation-sensitive (radiochromic) gels.
Radiochromic gel dosimeters are fabricated from radiation sensitive chemicals, which, upon irradiation, exhibit change in color intensity as a function of radiation dose. These gel dosimeters are radiologically soft-ssue equivalent, which have properties enabling the gels to be modified depending on the radiotherapy applications.
The main objective of this work is to develop radiochromic film dosimeters, gel dosimeters and radiation indicators based on some synthesized and reactive diacetylenes. In addition, it aims to study the radiation-induced polymerization of new prepared diacetylene monomers by different spectroscopic techniques. The physico-chemical characteristics of the prepared dosimeters were then investigated for the potential of use in
radiotherapy, blood and radiation processing applications (food irradiation and medical sterilization). The results obtained in this work can be
summarized in the following:
Part 1
This part contains the synthesis of conjugated diacetylene derivative of
2,4-hexadeyne-1,6-bis (n-hexyl urethane) HDHU by reacting n-hexyl
isocyanate with a freshly synthesized 2,4-hexadeyne-1,6-diol (HDD)
monomer. HDD monomer was freshly prepared using an oxidative coupling
method (Hay method). The prepared HDHU monomer was characterized by
FTIR spectroscopy. Then, it was embedded into a polyvinyl butyral (PVB)
polymeric solution by casting this solution onto a polyester sheet and coating
using an Automatic Film Applicator System. This is to develop radiochromic
film dosimeter that can be applied for a wide dose ranges in radiation
technology applications. HDHU monomer polymerizes under γ-radiation
inducing change in the UV-Vis absorption spectra and color formation in the
PVB films. The change in the HDHU films by γ-radiation is related to the
topochemical polymerization due to the presence of the HDHU monomer in
its crystalline state in the PVB film. The radiation polymerization of HDHU
induces a change in the absorption spectra in the spectrum range of 450 –700
nm. HDHU/PVB films were investigated in the dose range of 5.0 Gy – 15.0
kGy at absorption bands at 579 nm and 529 nm for prospective application in dosimetry. The spectrum of unirradiated films has no any absorption band,
however, upon exposure to -radiation, two absorption bands at a λmax of 529
nm and 579 nm were developed. The intensity of these bands grows with the
increase of radiation dose without any noticeable shift in the positions of the
bands. The useful dose range is 5.0 Gy – 15.0 kGy based on the concentrations
of HDHU monomer and the selected wavelength. This dose range reflects the
appropriateness for use in radiotherapy, blood irradiation, fresh and dried
food irradiation, and radiation sterilization of some medical devices. The
radiation sensitivity of these films increases with the increase of HDHU
content in PVB film. FTIR spectrum of HDHU monomer exhibited two bands
at 3321 cm-1
(sharp and strong) and 1538 cm-1
specifying N-H bond
stretching and bending vibration of secondary amine, respectively. In
addition, a weak absorption band at 2104 cm-1
of diacetylenes (C≡C medial
alkyne) was observed in the spectrum. The dose response of the film varied
within approximately ±2% in the RH range of 0-33% during irradiation. The
response increased by 14.9% in the case of wavelength 579 nm with further
increase of RH from 53% to 94%. To minimize the environmental effects, it
is strongly recommended to calibrate the dosimeters under actual radiation
processing conditions in the production facility using an independent
reference dosimetry system. The signals of irradiated films stored at -4 oC
were very stable over the whole observation period of 65 days. The responses
of films stored at room temperature in the dark increased slightly in the first
24 h by a value of less than 2% and remained stable for further 48 h. Then,
they increased slowly with ≈21% and ≈11% for 100 phr and 150 phr HDHU
films, respectively. On the contrary, the responses of the films stored at room temperature under fluorescent light, showed a slow increase in the first 3 days after irradiation then grew more slowly until the end of the observation period. Thus, to minimize the systematic errors from the absorbance change
during the post-irradiation storage, it is better to keep these films after
irradiation and before the absorbance measurements in a dark and cool place,
or to standardize the period between irradiations and measurements in both
calibrations and routine dose determinations. The overall uncertainty of
absorbed dose determined with this dosimetry system was found to be less
than 5.22% (2σ).
Part 2
A poly(vinyl alcohol) (PVA) radiochromic dosimeter containing 2,4-
hexadiyn-1,6-bis(p-toluene sulfonyl urethane) (HDTU) monomer was
manufactured for potential use in radiation process control at a dose range of
10.0 Gy – 15.0 kGy. HDTU monomer was synthesized by reacting p-toluene
sulfonyl isocyanate with a freshly synthesized 2,4-hexadeyne-1,6-diol (HDD)
monomer. The synthesized HDTU monomer was then dispersed into PVA
solution using an emulsification process. After that, the dispersed HDTUPVA solution was coated on self-adhesive paper using an Automatic Film
Applicator System. This FTIR spectrum of the synthesized HDTU monomer
exhibited bands at 3452 cm-1
(N-H stretching vibration) and 3138 cm-1
(aromatic C-H stretching). It displays a band at 1634 cm-1
of phenyl C=C,
1600 cm-1
of conjugated C=C (formed due to partially polymerized monomer)
and another one at 2174 cm-1
of diacetylenes, C≡C medial alkyne. Bands of
C=O stretching was developed at 1758 cm-1
and 1738 cm-1
. This spectrum
has many bands in the range of 1420-1300 cm-1
and 1200-1100 cm-1
that can
be assigned for sulfur-oxy compounds (sulfonyl, sulfoxides, and sulfones
S=O). The physicochemical characteristics of the prepared radiochromic
dosimeters were investigated using a portable reflectance colorimeter at 480
nm, 560 nm and 610 nm. This dosimeter turns visually into purple color upon γ-irradiation and this color increases with the increase of radiation doses by a
bi-exponential rise to maximum, 4 parameters equation. This developed color
is attributed to topochemical polymerization of the solid HDTU monomer, in
a crystalline state, upon irradiation. XRD analyses showed that the HDTU
embedded into PVA films is greatly ordered and crystalline and, upon γirradiation, it produces a semi-crystalline polymer with nearly the same
interplanar distances as the HDTU monomer, demonstrating the occurrence
of topochemical polymerization. The radiation sensitivity of this dosimeter
increases significantly as the HDTU monomer concentration increases in
PVA films. The response increases proportionally with increasing doses then
tends to saturate at the higher radiation doses. The dosimeter response at
wavelength 480 nm is nearly unchanged by the temperature rise from 25 to
45oC; however, it is significantly influenced by temperature rise up to 55 oC.
On the other hand, the responses measured at 560 and 610 nm are nearly
independent of the temperature from 25 to 55oC. This dosimeter is not depend
on the humidity in the range of 0-53% RH for the three-selected wavelengths.
The useful dose range was found to be 10.0 Gy – 15.0 kGy depending on the
amount of HDTU in PVA and the selected wavelength for the analysis. This
dose range may confirm the validity of use of these labels for blood
irradiation, inhibition of sprouting, grain disinfestation, delay of ribbing in
fresh foods, and reduction of microorganisms in dry foods. The overall
uncertainty of dose measurement was found to be less than 5.20% and 5.0%
(2σ) at 560 and 610 nm, respectively. The results reveal that the label is
capable of estimating the radiation dose delivered to products, especially if
being calibrated under similar conditions of industrial irradiation. The
colorimeter used in the analysis of the dosimeter is a portable, which enables
the operators of irradiation facilities to release the irradiated products fast.
Part 3
This part is concerned with studying the dosimetric characteristics of
new radiochromic gel dosimeters prepared by using the laboratorysynthesized 2,4-hexadiyn-1,6-bis(n-hexyl urethane) (HDHU) (Chapter 4.3.).
These gel dosimeters were prepared by the addition of HDHU monomer into
aqueous gelatin solution by emulsification. HDHU monomer polymerizes
upon γ-irradiation inducing a visual color change into red. The gel dosimeter
was studied using UV-Vis spectrophotometer at different absorbed doses. In
the beginning of irradiation, the spectrum of irradiated gels featured two main
absorption bands located approximately at 530 nm and 570 nm. However,
with further increase of absorbed dose, the intensity of the two bands
increases without any major shift in the band positions. Thus, both bands were
selected for the present study.
The response decreases by the temperature increase during irradiation by a
linear trend from 10o
to 20 oC. However, the response is less influenced by
the increase of temperature from 20 to 30 oC, which is the useful range for
most dosimetric application; the increase in response is around 0.28% per oC.
It’s better to use this gel dosimeter in the range of 20 to 30 oC (i.e. at RT) to
minimize the error resulting from the effect of temperature otherwise to
perform the calibration curve under actual conditions of use. The response of
gels stored in refrigerator is good stable over the period of 12 days of storage.
The present results showed that the present gel dosimeter could be applied for
the dose range of 2.0 – 100.0 Gy based on HDHU monomer content in the
gel. This dose range can be useful for radiation therapy and blood irradiation
applications. The overall uncertainty in the estimated dose values by the gel
dosimeter was reported as 5.02% and 4.33% (at 2σ, 95% confidence level)
for 530 nm and 570 nm.
The HDHU monomer used in the gel exhibits higher radiation dose
sensitivity. Thus, in the future, it will be investigated in further studies to
introduce it into gel to make slices to be easily investigated by photo-flatted
scanner for validation and verification of radiotherapy treatments.
Part 4
This part is related to the study of radiation-induced polymerization
of laboratory-synthesized 2,4-hexadiyn-1,6-bis (n-ethyl urethane) (HDEU)
monomer using FTIR spectrometer, Raman spectrometer, UV-Visible
spectrophotometer, X-ray diffraction (XRD) analyzer and Electron
Paramagnetic Resonance (EPR) spectrometer (Chapter 4.3.). FTIR spectra
showed the absorption band of C≡C medial alkyne at around 2149 cm-1 that
confirm the presence of diacetylene compound. Other two absorption bands
were obtained at 3298 cm-1
and 1540 cm-1
indicating the presence of N-H
stretching and bending vibration of secondary amine, respectively. In
addition, the observed weak band at 3086 cm-1
characteristics of C–H
stretching of C=C–H that explain the partial polymerization of monomer. The
bands of C≡C and C=C bonds is clearly shown in Raman spectra of irradiated
monomer at the bands of 1515 cm-1 and 2130 cm-1 due to the presence of
HDEU in the red phase. The results of Raman spectroscopy confirm that
Raman technique can be used for the monitoring of DAs topochemical
polymerization and thus color intensity change for dosimetry purposes. Two
different types of HDEU films, HDEU/Acetone and HDEU/Dioxane, were
prepared and studied using a UV-Visible spectrophotometer. HDEU undergo
polymerization with gamma irradiation inducing coloration in the prepared
films. The intensity of the developed color increases significantly with increasing absorbed doses as confirmed by visible spectra. The irradiated
HDEU/Acetone and HDEU/Dioxane films exhibited absorption bands at λmax
≈573 nm and at ≈533 nm. The intensity of these bands increases gradually
with increasing the radiation exposure time without inducing any significant
shift in the band positions at high-absorbed doses. The radiation sensitivity of
HDEU/Acetone films is higher than that of HDEU/Dioxane films by 24.4%.
XRD pattern of HDEU monomer confirm the crystallinity of the
prepared HDEU molecules which leading to the occurrence of solid-state
topochemical polymerization after subjecting to ionizing radiation. Three
main sharp peaks of HDEU monomer are observed at 2θ = 20.62° (interplanar distance d=4.30 Ǻ), 2θ = 22.66° (d=3.92 Ǻ) and 2θ = 23.49° (d=3.78
Ǻ) with different intensities. In addition, two other sharp peaks appeared at
2θ = 10.39° (d=8.5 Ǻ) and 2θ = 11.53° (d=7.66 Ǻ). The XRD array of PolyHDEU show similar peaks to that of monomer with little broadening. XRD
display the perfect inter-planar distances between stacking molecules inside both films that matches the Wegner rule and offering the occurrence of topochemical polymerization to produce highly colored poly-HDEU films. In addition, the radiation-induced change in HDEU can be followed using an
EPR technique. HDEU monomer has no EPR signals, however, upon gamma
ray exposure, a sharp EPR signal develops and increases gradually by
increasing the radiation dose.