Sinead O’Keeffe

Sinead O’Keeffe
University of Limerick | UL · Department of Electronic and Computer Engineering

About

130
Publications
36,264
Reads
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1,185
Citations
Citations since 2017
49 Research Items
680 Citations
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120

Publications

Publications (130)
Conference Paper
The radiation sensing capability of benzyl-dimethylketal(BDK) and diphenyl disulphide(DPDS) core doped POF-FBG is presented and demonstrates a wavelength shift with a sensitivity of 2.177 pm/Gy for DPDS and 1.327 pm/Gy for the BDK doped POF-FBG.
Article
This paper reports the characterization of two scintillating materials in powder form, Gadox and YVO embedded in a light-activated resin, used in a probe developed for oncological brachytherapy in-vivo dosimetry. The materials were characterized in terms of internal absorption, scintillation decay time, and light yield. The measurement of the optic...
Conference Paper
Doping of polymethyl-methacrylate (PMMA) polymer optical fibre (POF) with Trans-4-stilbenemethanol (TS) increases the sensitivity to radiation by a factor of over two. The potential of step index TS doped PMMA POF for online radiation monitoring is reported
Conference Paper
This work presents the feasibility of Kuraray's plastic scintillator based fibre for monitoring external beam radiation therapy. The sensor was investigated within a clinical linac for different energies, dose rates and field sizes for comparison.
Article
Full-text available
This work considers the feasibility of using a novel optical fiber based sensor, employing a Terbium-doped Gadolinium Oxysulfide (Gd2O2S:Tb) inorganic scintillator, as a real-time in-vivo dosimetry solution for applications in low dose rate (LDR) prostate brachytherapy (BT). This study specifically considers the influence of scintillator geometry (...
Conference Paper
Perfluorinated polymer fibre are tested to characterise the Bragg Peak of a 69 MeV proton beam for comparison to Marcus chamber results. This paper presents the potential of perfluorinated polymer fibre in relative proton dosimetry applications
Article
Full-text available
An optical fibre sensor based on radioluminescence, using the scintillation material terbium doped gadolinium oxysulphide (Gd2O2S:Tb) is evaluated, using a 3D printed anthropomorphic phantom for applications in low dose-rate (LDR) prostate brachytherapy. The scintillation material is embedded in a 700 µm diameter cavity within a 1 mm plastic optica...
Conference Paper
This paper presents an evaluation of optical fibre sensors for use in brachytherapy treatment where the sensor tip is embedded with radiosensitive scintillation powder, Terbium doped Gadolinium Oxysulphide (Gd 2 O 2 S:Tb). Two sensors, fabricated using the same fiber design parameter and size, have been fabricated and evaluated using a Standard Ima...
Article
A reliable, accurate and in-vivo dosimetry system for measuring the radiation dose and profiling the X-ray beam during radiotherapy is reported. Its dynamic range is investigated using an accurately controlled pulsed light emitting diode (LED) system. Highly resolved temporal analog and digital signals were captured from the analog and digital outp...
Article
Full-text available
An optical fiber sensor for monitoring low dose radiation is presented. The sensor, based on radiation sensitive scintillation material, terbium doped gadolinium oxysulphide (Gd2O2S:Tb), is embedded in a cavity of 700µm diameter within a 1mm plastic optical fiber. The sensor is compared with the treatment planning system for repeatability, angular...
Article
Full-text available
This paper presents the development of an extrinsic optical fibre sensor for continuous measurement of the human spine bending movement based on intensity modulation technique. Using the investigated sensor configuration, the bending angle was measurable in both flexion and extension direction with a maximum range of motion of 18° and -10°, respect...
Article
Full-text available
The system presented in this paper demonstrates how a novel fibre optic based sensing platform, capable of detecting minute changes in the level of impurity in a liquid, can be incorporated onto a Mote based platform enabling real time monitoring of a body of water. How these features can be used to detect a representative sample of chlorophyll wit...
Conference Paper
Optical fibers are close to ideal detectors to measure radiation beams for cancer therapy, either as beam monitors or for dosimetiy. Several organic and inorganic fibers were tested with proton and neutron beams. One material stood out in its almost complete lack of quenching for low proton energies.
Article
Purpose The aim of this study was to investigate the contribution of Cerenkov radiation to the overall signal measured with a novel inorganic scintillating detector (ISD). Methods An ISD based on terbium doped gadolinium oxysulphide (Gd2O2S:Tb) was used. A hyperspectral technique separated the Cerenkov signal from the radioluminescence (RL) signal...
Article
Full-text available
The power coupling ratio between step-index multimode fibers caused by combined transversal and angular misalignment is calculated. A theoretical description of the coupling efficiency between two optical fibers based on geometrical optics is provided. The theoretical calculations are collaborated by experiments, determining the power coupling rati...
Article
A novel robust compact light emitting diode (LED) based laboratory simulator system for mimicking the output from an optical fibre sensor used to detect therapeutic X-ray pulses from a clinical linear accelerator (linac) is described and performance characterised with reference to real clinical data. The purpose of configuring the LED system is to...
Article
Full-text available
This study aims to investigate the validity and reliability of a novel plastic optical fiber (POF) sensor, which was developed to measure the angles of flexion, extension and lateral bend at the lumbar region. The angles of flexion, extension and lateral bend for a standing position were measured simultaneously using both the novel POF sensor of th...
Article
The aim of this study was to investigate the dosimetric performance of a novel optical fiber sensor for use in external beam radiation therapy. Repeatability and reproducibility of the output signal, linearity, dose rate and dose per pulse dependence were evaluated. Angular dependence was investigated in the axial and azimuthal planes. The percenta...
Article
Full-text available
A Terbium activated Gadolinium Oxysulfide (Gd2O2S:Tb)-filled optical fibre sensor was developed and tested as a proton therapy beam dosimeter on a 74 MeV proton beam. Tests were carried out at the TRIUMF proton therapy centre, where a passively scattered beam is used for treatment. To create a clinically relevant spread-out Bragg peak, a modulator...
Article
Full-text available
A miniature optical fibre real time X-Ray radiation sensor based on plastic optical fibre coupled with a fast decay time trivalent cerium activated yttrium aluminium garnet Y3Al5O12 (YAG:Ce) scintillator material is reported. The YAG material was tested in powder and ceramic form. Three separate sensors were irradiated three times on a Siemens Arti...
Article
Modern radiation therapy treatment techniques and delivery methods introduce new challenges to existing dosimetry systems. As a result, much research has been conducted on the development of a radiation dosimetry system based on scintillating optical fibre. They offer many advantages over the currently employed dosimeters for real time dosimetry. O...
Article
A characterization study was carried out to determine if a novel, millimetre sized Terbium-activated Gadolinium Oxysulfide optical fibre detector has potential for future use in proton dosimetry. Preliminary studies employed a Theratronics Theratron 780C Cobalt-60 unit and were used to determine nominal dose response, field size response and Čerenk...
Chapter
The use of ionising radiation in a wide range of areas, from industrial processes to medical applications, has become increasingly significant in recent years. Radiation dosimetry, the measurement of absorbed dose delivered by ionising radiation, is fundamental to these radiation processes, ensuring tight control on radiation processes and the safe...
Article
Full-text available
A mechanically robust and compact novel optical fiber sensor system is described to monitor the bending of the lower back bone in both sagittal and frontal planes. Both bending modes are monitored through the change of the coupled optical intensity ratio between three output fibers aligned to one input fiber. This provides real-time feedback to the...
Article
Full-text available
Review is made of dosimetric studies of current optical fibre technology in radiotherapy for therapeutic applications, focusing particularly on in vivo dosimetry for prostate radiotherapy. We present the various sensor designs along with the main advantages and disadvantages associated with this technology. Optical fibres are ideally placed for app...
Conference Paper
An optical fibre sensor for monitoring low dose radiation is presented. The sensor is based on a scintillation material embedded within the optical fibre core, which emits visible light when exposed to low level ionising radiation. The incident level of ionising radiation can be determined by analysing the optical emission. An optical fibre sensor...
Conference Paper
Recent advancements in cloud computing technologies in the context of optical and optical fibre based systems are reported. The proliferation of real time and multi-channel based sensor systems represents significant growth in data volume. This coupled with a growing need for security presents many challenges and presents a huge opportunity for an...
Conference Paper
An optical fibre sensor is presented for applications in real-time in-vivo monitoring of the radiation dose a cancer patient receives during seed implantation in Brachytherapy. The sensor is based on radioluminescence whereby radiation sensitive scintillation material is embedded in the core of a 1mm plastic optical fibre. Three scintillation mater...
Article
Full-text available
This paper presents the theoretical investigation and experimental validation of an extrinsic optical fibre bending sensor based on intensity modulation with automatic compensation. The proposed optical fibre bending sensor can measure continuous bending movement in flexion, extension and lateral directions, simultaneously. The theoretical study is...
Article
Full-text available
This paper presents an overview of the recent developments and requirements in radiotherapy dosimetry, with a particular emphasis on the development of optical fibre dosimeters for radiotherapy applications, focusing particularly on in-vivo applications. Optical fibres offer considerable advantages over conventional techniques for radiotherapy dosi...
Article
Full-text available
A novel real-time optical fibre X-Ray dosimeter for monitoring the radiation pulses delivered from a clinical linear accelerator (Linac) is presented. The primary focus of the sensor is to measure low doses of ionising X-ray radiation in real time (limited to 0.1-ms gate time of the detector). The sensor tip material scintillates upon exposure to X...
Article
An extrinsic optical fibre bending sensor based on intensity modulation technique aimed for physiological application is presented. This sensing technique is capable of measuring the bending angle continuously in flexion, extension and lateral movements. The sensor working range is between -22o and 22o with 0.4o accuracy and 0.1o resolution. From t...
Conference Paper
This paper presents the implementation of an extrinsic optical fibre sensor based on intensity modulation technique aimed for continuous bending assessment of human spine movement. The sensor under investigation is non-invasive and capable of providing a continuous measurement of the bending angle in both flexion and extension directions of the hum...
Article
Full-text available
IEEE 802.15.4 is the technology behind wireless sensor networks (WSNs) and ZigBee. Most of the IEEE 802.15.4 radios operate in the crowded 2.4 GHz frequency band, which is used by many technologies. Since IEEE 802.15.4 is a low power technology, the avoidance of interference is vital to conserve energy and to extend the lifetime of devices. A light...
Conference Paper
Full-text available
This paper presents the development of an extrinsic optical fibre sensor for continuous measurement of the human spine bending movement based on intensity modulation technique. Using the investigated sensor configuration, the bending angle was measurable in both flexion and extension direction with a maximum range of motion of 18 o and -10 o , resp...
Conference Paper
Full-text available
The system presented in this paper demonstrates how a novel fibre optic based sensing platform, capable of detecting minute changes in the level of impurity in a liquid, can be incorporated onto a Mote based platform enabling real time monitoring of a body of water. How these features can be used to detect a representative sample of chlorophyll wit...
Conference Paper
Full-text available
The light attenuation measurement of a plastic optical fibre sensor based on a referenced intensity modulation technique with respect to different input voltage level and room temperature has been investigated. The results show that light attenuation at the sensor output and reference output are dependent on the source (LED) drive current and tempe...
Conference Paper
Full-text available
A PMMA based plastic optical fibre sensor for use in real time radiotherapy dosimetry is presented. The optical fibre tip is coated with a scintillation material, terbium-doped gadolinium oxysulfide (Gd2O2S:Tb), which fluoresces when exposed to ionising radiation (X-Ray). The emitted visible light signal penetrates the sensor optical fibre and prop...
Article
Full-text available
A novel extrinsic optical fiber X-ray dosimeter for biomedical applications is presented in this paper. The primary focus of the sensor is to measure low doses of ionizing X-ray radiation. The material in the sensor tip scintillates upon exposure to radiation and the resultant low level scintillating light is coupled to a polymethylmethacrylate pla...
Data
The paper presents a set of tests carried out in order to evaluate the design characteristics and the operating performance of a set of six X-ray extrinsic optical fiber sensors. The extrinsic sensor we developed is intended to be used as a low energy X-ray detector for monitoring radiation levels in radiotherapy, industrial applications and for pe...
Article
Full-text available
The paper presents a set of tests carried out in order to evaluate the design characteristics and the operating performance of a set of six X-ray extrinsic optical fiber sensors. The extrinsic sensor we developed is intended to be used as a low energy X-ray detector for monitoring radiation levels in radiotherapy, industrial applications and for pe...
Conference Paper
A PMMA (polymethyl methacrylate) based plastic optical fibre is coated with radiation sensitive inorganic scintillators that fluoresce when exposed to ionising radiation. The emitted signal penetrates the fibre and propagates along the fibre where it is remotely monitored using a fluorescence spectrometer. The dosimeter is characterised for a range...
Conference Paper
Full-text available
This paper presents the development of bending sensor using plastic optical fibre. The bending angle is measured with respect to the changes in light intensity at the receiving fibre. To study the relationship between the sensor's output intensity po wer and the bending angle, three mediums with different refractive index were used at the gap...
Conference Paper
Full-text available
This paper presents the investigation of sensing range limit for intensity modulated optical fibre bending sensor using single input and dual input fibres. Plastic optical fibre is used to measure the bending angle by measuring the changes of light inteusity using tilt angle loss measurement approach. To define the bending range of the seusor...
Article
Full-text available
Abstract: This paper presents the implementation of power fluctuation compensation for an intensity-based optical fibre bending sensor aimed at monitoring human spine bending in a clinical environment. To compensate for the light intensity changes from the sensor light source, a reference signal was provided via the light reflection from an aluminu...
Article
Full-text available
This paper presents a study on the application of plastic optical fibre for spine bending monitoring based on an intensity modulation. The bending angle is measured as the angle between the emitting and receiving fibres is changed. The measured light attenuation is compared with a theoretical evaluation and the differences between these values a...
Conference Paper
A plastic optical fibre, coated with a terbium-doped gadolinium oxysulfide phosphor (Gd2O2S:Tb) is presented. The paper presents the sensor's response to a range of known radiotherapy exposure patterns and characterises its response to varying energy levels and dose rates.