مجال
التميز
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تميز
دراسي و بحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Ge and
B doped collapsed photonic crystal optical fibre, a potential TLD material
for low dose measurements
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رابط إلى البحث:
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Click here
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تاريخ النشر:
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29/04/2016
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موجز عن البحث:
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Offering a
number of advantageous features, tailor-made silica-based fibres are
attracting attention as thermoluminesence (TL) dosimeters. We have performed
a detailed study of the TL properties of Ge-doped and Ge-B-doped collapsed
photonic crystal fibres (PCFc), most particularly with regard to their
potential use for the environmental and X-ray diagnostic dose monitoring. Extrinsic
doping and defects generated by strain at the fused inner walls of the
collapsed fibres result in the PCFc-Ge-B and PCFc-Ge fibres producing
markedly greater TL response than that of the phosphor-based dosimeter
TLD-100, by some 9 and 7×, respectively. The linearity of TL yield has been
investigated for X-ray doses from 0.5 mGy to 10 mGy. For a dose of
1 Gy, the energy response of the PCFs and TLD-100 has been studied using
X-rays generated at accelerating potentials from 20 kVp through to
200 kVp and for the 1.25 MeV mean gamma-ray energy from 60Co.
The effective atomic number,Zeffof PCFc-Ge and PCFc-Ge-B was estimated to be
12.5 and 14.4, respectively. Some 35 days post-irradiation, fading of the
stored TL signal from PCFc-Ge-B and PCFc-Ge were found to be ∼15%
and 20% respectively, with mean loss in TL emission of 0.4–0.5% per day. The
present doped-silica collapsed PCFs provide greatly improved TLD performance
compared to that of previous fibre designs and phosphor-based TLD-100.
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البحث (2):
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عنوان البحث:
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Tailor-made
Ge-doped silica-glass for clinical diagnostic X-ray dosimetry
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رابط إلى البحث:
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Click here
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تاريخ النشر:
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22/07/2017
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موجز عن البحث:
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In the
modern clinical practice of diagnostic radiology there is a growing demand
for radiation dosimetry, it also being recognized that with increasing use of
X-ray examinations additional population dose will result, accompanied by an
additional albeit low potential for genetic consequences. At the doses
typical of diagnostic radiology there is also a low statistical risk for
cancer induction; in adhering to best practice, to be also implied is a low
but non-negligible potential for deterministic sensitive organ responses,
including in regard to the skin and eyes. Risk reduction is important, in
line with the principle of ALARP, both in regard to staff and patients alike;
for the latter modern practice is usually guided by Dose Reference Levels
(DRL) while for the former and members of the public, legislated controls
(supported by safe working practices) pertain. As such, effective, reliable
and accurate means of dosimetry are required in support of these actions.
Recent studies have shown that Ge-doped-silica glass fibres offer several
advantages over the well-established phosphor-based TL dosimeters (TLD),
including excellent sensitivity at diagnostic doses as demonstrated herein,
low fading, good reproducibility and re-usability, as well as representing a
water impervious, robust dosimetric system. In addition, these silica-based
fibres show good linearity over a wide dynamic range of dose and dose-rate
and are directionally independent. In the present study, we investigate
tailor made doped-silica glass thermoluminescence (TL) for applications in
medical diagnostic imaging dosimetry. The aim is to develop a dosimeter of
sensitivity greater than that of the commonly used LiF (Mg,Ti) phosphor. We
examine the ability of such doped glass media to detect the typically low
levels of radiation in diagnostic applications (from fractions of a mGy
through to several mGy or more), including, mammography and dental radiology,
use being made of x-ray tubes located at the Royal Surrey County Hospital. We
further examine dose-linearity, energy response and fading.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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(IRRMA) “International topical meeting on industrial radiation
and radioisotope measurement applications conference
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تاريخ الإنعقاد:
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10/07/2017
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مكان
الإنعقاد:
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Chicago, USA
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طبيعة المشاركة:
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Paper
presentation
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عنوان المشاركة:
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Thermoluminscence
Measurement of Eye-Lens Dose in a Multicentre Stereotactic Radiosurgery Audit
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ملخص المشاركة:
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Stereotactic
radiosurgery (SRS) is a non-invasive radiation therapy technique aimed at the
delivery of a high dose of ionizing radiation to a precisely defined target
while preserving the surrounding tissue. SRS, now of increasing popularity,
is constantly being developed for treatment of various functional abnormalities,
malignant and benign brain lesions, with notable commercial platforms such as
Gamma Knife, and the Linac-based systems: X-Knife and Cyberknife. All
demonstrate usefulness in achieving local tumour control for single and multiple
brain metastases, while seeking to maintain a low rate of complications. The
imaging techniques used for localizing SRS targets include CT or MRI,
imported into special treatment planning software that allow simulation and
assessment of the most effective treatment approach. With a number of such
approaches in delivering SRS, this is an area befitting greater investigation
and standardization. Here we report efforts made in multi-centre (19 in all) dosimetric
audit, set up to investigate the range of SRS practices for a single brain
metastasis using a series of detectors and an anthropomorphic head phantom.
With the lens being one of the most radiosensitive tissues, one audit aim has
been to determine the dose received by the lens from scattered radiation
during an SRS treatment. A further aim has been the evaluation of the imaging
dose received during the CT-scan acquired at the planning stage. In
satisfying these aims, custom-designed holders have been fabricated to carry
three types of thermoluminscent dosimeter: Ge-doped optical fibres, glass
beads and TLD-100, the latter being adopted as a reference dosimeter. A
bespoke 3D-printed goggle insert was then produced for the head phantom to
allow reproducible placement of the TLD holders. The National Council on
Radiation Protection and the International Commission on Radiological
Protection have pointed to a threshold dose capable of producing cataract
formation of some 2 Gy in a single exposure and 5 Gy for fractionated or
protracted exposure [1]. Present guidance is for a reduction in the dose that
can be received by the lens, to 0.5 Gy [2]. Our preliminary results for the
SRS procedure show doses of between 0.2 to 0.3 Gy.
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المؤتمر (2):
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عنوان المؤتمر:
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9th Saudi students’ Conference
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تاريخ الإنعقاد:
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13/02/2016
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مكان
الإنعقاد:
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Birmingham.UK
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طبيعة المشاركة:
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Poster
presentation
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عنوان المشاركة:
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Thermoluminescence
studies of several forms of silica-based media for x-ray diagnostic imaging
dosimetry
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ملخص المشاركة:
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We
investigate doped-silica fibres thermoluminescence (TL) media. Offering high
spatial resolution, in the range 0.1 to 3 mm, the challenge is to develop a
material more dosesensitive than LiF (Mg, Ti) as popularly used in x-ray
imaging. Interest is in Gedoped silica telecommunication fibres (SMF) and
tailor-made doped photonic crystal fibres (PCF). The PCFs, Ge-doped or also
co-doped with boron, are formed of doped capillaries that are subsequently
collapsed-down at high temperatures in order to generate strain-related
defects, increasing the TL yield and hence dose sensitivity. We test their
ability to detect radiation from the low levels of diagnostic chest
radiography through to the doses observed in fluoroscopic investigations, use
being made of an x-ray tube operated at 80 kVp as typically used in chest
radiography. We further examine dose-linearity, energy response and
reproducibility.
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المؤتمر (3):
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عنوان المؤتمر:
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The
International Conference on Dosimetry and Its Applications-ICDA-2
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تاريخ الإنعقاد:
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08/07/2015
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مكان
الإنعقاد:
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Guildford,
UK
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طبيعة المشاركة:
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Poster
presentation
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عنوان المشاركة:
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Assessment
of the efficacy of a thermoluminscent dosimeters holder for a multicentre
stereotactic radiosurgery audit
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ملخص المشاركة:
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Stereotactic
radiosurgery (SRS) is a non-invasive radiation therapy technique which
involves delivering a high dose of ionising radiation to a precisely defined
target while preserving the surrounding tissue. The use of SRS is rapidly
increasing and constantly developing to treat various functional
abnormalities, malignant and benign brain lesions. There are several
commercial platforms available that can deliver SRS treatments including
Gamma Knife, Linac, and Cyberknife. All delivery techniques have demonstrated
their usefulness in achieving local tumour control for single and multiple
brain metastases whilst maintaining a low rate of complications.
The imaging
techniques used for localising SRS targets include CT or MRI that are then
imported into special treatment planning software that allow simulation and
assessment of the most effective treatment approach. However, there are a few
different approaches in delivering SRS and it remains a field that will
benefit from more investigation and standardisation.
A
multi-centre dosimetric audit has been set up to investigate the range of SRS
practices for a single brain metastasis using a series of detectors and an
anthropomorphic head phantom. As the lens is one of the most radiosensitive
organs in the body, one of the aims of this audit has been to determine the
dose received by the lens from scattered radiation during an SRS treatment.
The imaging dose received during the CT-scan acquired in the planning stage
is also a concern. For this purpose, custom-designed holders have been
manufactured to carry three types of thermoluminscent dosimeters: Ge-doped
optical fibres, glass beads and the TLD-100, the latter being used as a
reference dosimeter. The holders are in the form of cylindrical black boxes,
the dimensions of which are suited for placement onto the location of the eye
surface of the phantom. A bespoke 3D-printed (goggle) insert was produced for
the head phantom to allow reproducible placement of the TLD holders for CT
and SRS. In this work, we have demonstrated that the goggle insert and the
TLD holders produced are suitable for the dosimetric assessment undertaken in
the audit.
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المؤتمر (4):
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عنوان المؤتمر:
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XVI
International Symposium on solid state Dosimetry (ISSSD 2016)
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تاريخ الإنعقاد:
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24-28 /09/2016
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مكان
الإنعقاد:
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Chiapas,
Mexico.
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طبيعة المشاركة:
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Paper
presentation
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عنوان المشاركة:
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Tailor-made
Ge-doped Silica-glass for clinical diagnostic X-ray dosimetry
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ملخص المشاركة:
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In modern
clinical practice there is growing demand for radiation dosimetry in
diagnostic radiology. Here it is to be acknowledged that with the increasing
use of X-ray examinations, digital and otherwise, it is evident that there is
additional loading to population dose, with potential genetic consequences.
Further, although at the doses typical of diagnostic radiology cancer
induction remains a low statistical risk it is also true that there is a
non-negligible albeit low potential for deterministic response to sensitive
organs such as the skin and eyes of staff. As such, effective, reliable and
accurate means of dosimetry are required. Studies have shown that
Ge-doped-silica glass fibres offer several advantages over the
well-established phosphor-based TL dosimeters, including its good
sensitivity, low fading, good reproducibility and re-usability, water
impervious and robust nature. In addition, these silica based fibres show
good linearity over a wide dynamic range of dose and dose rate and are directionally
independent [2]. In the present study, we investigate tailor made
doped-silica glass thermoluminescence (TL) for applications in medical
diagnostic dosimetry. The aim is to develop a dosimeter of sensitivity
greater than that of the commonly used LiF (Mg,Ti) phosphor. We examine the
ability of such doped glass media to detect the typically low levels of
radiation (from fractions of a mGy through to several mGy or more) in
diagnostic applications that include mammography and dental radiology, use
being made of x-ray tubes located in the Royal Surrey County Hospital. We
further examine dose-linearity, energy response and reproducibility.
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المؤتمر (5):
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عنوان المؤتمر:
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International
Forum on Advances in Radiation Physics 2017
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تاريخ الإنعقاد:
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4-5 /05/2017
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مكان
الإنعقاد:
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Buenos
Aires, Argentina.
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طبيعة المشاركة:
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Paper
presentation
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عنوان المشاركة:
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Enhancement
in dose sensitivity of GeB-FF using (MCVD)
process for dosimetric applications in radiology
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ملخص المشاركة:
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Owing to the
increased demand for diagnostic radiation examinations, radiation dosimtery
has become an area of significant importance. It is also being recognized
that with increasing use of X-ray examinations the probability of low
potential risk for genetic consequences would also increase. Even though at
the doses typical of diagnostic radiology(DR) is considered low, there is
also a low statistical risk for cancer induction. In addition, there is also
non-negligible potential for deterministic effects for sensitive organs
responses, including the skin and eyes. In line with the principle of ALARP,
risk reduction is important for both in regard to staff and
patient.
There is
several important features ideal dosimeter that are useful in diagnostic
radiology dosimetry, such as high accuracy and precision, detection limit,
measurement range, dose response, spatial resolution, dose rate response
independence, energy independence, and tissue equivalent which are very
useful for diagnostic radiology dosimetry. All of these charactristics have
been obtained with the introduction of thermoluminescent dosimeters (TLDs)
the most commonly used in DR dosimetry applications are based on LiF:Mg,Ti
(dosimetry status and trends). In this
sense, for this purpose, two types of a novel GeB- Flat Fiber which have been
fabricated using MCVD process. In this technique, it is shown that there is
enhancement in the thermoluminescence (TL) response of optical fibers, based
on collapsing down hollow capillary optical fibers (COF) into flat fibers
(FF), producing fused inner walls and consequent defects generation. In the
present study, we examine tailor made doped-silica glass thermoluminescence
(TL) for applications in clinical diagnostic imaging dosimetry. The intent is
to develop a dosimeter of sensitivity greater than that of the commonly
used LiF (Mg,Ti) phosphor. We investigate the ability of such doped
glass media to detect the typically low levels of radiation in
diagnostic applications (from fractions of a µGy through to several mGy
or more), including, chest, mammography and dental radiology, use being made
of x-ray tubes located at the Royal Surrey County Hospital. We further examine
dose-linearity, energy response and fading.
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