Evaluation of Bismuth Oxide Nanoparticles as Radiosensitizer for Megavoltage Radiotherapy

Metal-based nanoparticles such as gold, silver, platinum, and bismuth have been widely investigated for radiotherapeutic application. Basic understanding of the cellular interaction of the nanoparticles with the biological materials is crucial to ensure future clinical use. In this study, the cytotoxicity, cellular uptake, and generation of reactive oxygen species (ROS) induced by BiONPs were investigated prior elucidating the feasibility of BiONPs for radiotherapy application using megavoltage photon and electron beams. The BiONPs of diameter sizes 60, 70, 80 and 90 nm at concentrations within a range of 0.5 to 0.00005 mMol/L were tested on MCF-7, MDA-MB-231, and NIH/3T3 cells lines. The cytotoxicity results exhibit minimal cell death constituting less than 20 % of mortality on average. The ROS generation by BiONPs alone is found to be negligible as the ROS levels were slightly lower and higher than 100% of positive control. The increment of cellular nanoparticles uptake from a range of 1.50 % to 34.10 % indicates that BiONPs were internalized and bound to the surface of the cells. Sequencing from the results, 60 nm BiONPs are found to be the most suitable to be applied as a radiosensitizer in radiotherapy. Sensitization enhancement ratio (SER) quantified on MCF-7 cells demonstrated the highest enhancement from the highest concentration of BiONPs with SER of 2.29 and 1.42, for 10 MV photon beam and 6 MeV electron beam, respectively. In contrast to ROS production without radiation, the ROS induced from radiotherapy beams were found to be dose-dependent and play significant roles in radiosensitization effect. In conclusion, BiONPs could improve clinical radiotherapy, and further radiobiological characterization is crucial for future clinical translation

Imaging of moving fiducial markers during radiotherapy using a fast, efficient active pixel sensor based EPID

Purpose: The purpose of this work was to investigate the use of an experimental complementary metal‐oxide‐semiconductor (CMOS) active pixel sensor (APS) for tracking of moving fiducial markers during radiotherapy. Methods: The APS has an active area of 5.4 × 5.4 cm and maximum full frame read‐out rate of 20 frame s−1, with the option to read out a region‐of‐interest (ROI) at an increased rate. It was coupled to a 4 mm thick ZnWO4 scintillator which provided a quantum efficiency (QE) of 8% for a 6 MV x‐ray treatment beam. The APS was compared with a standard iViewGT flat panel amorphous Silicon (a‐Si) electronic portal imaging device (EPID), with a QE of 0.34% and a frame‐rate of 2.5 frame s−1. To investigate the ability of the two systems to image markers, four gold cylinders of length 8 mm and diameter 0.8, 1.2, 1.6, and 2 mm were placed on a motion‐platform. Images of the stationary markers were acquired using the APS at a frame‐rate of 20 frame s−1, and a dose‐rate of 143 MU min−1 to avoid saturation. EPID images were acquired at the maximum frame‐rate of 2.5 frame s−1, and a reduced dose‐rate of 19 MU min−1 to provide a similar dose per frame to the APS. Signal‐to‐noise ratio (SNR) of the background signal and contrast‐to‐noise ratio (CNR) of the marker signal relative to the background were evaluated for both imagers at doses of 0.125 to 2 MU. Results: Image quality and marker visibility was found to be greater in the APS with SNR ∼5 times greater than in the EPID and CNR up to an order of magnitude greater for all four markers. To investigate the ability to image and track moving markers the motion‐platform was moved to simulate a breathing cycle with period 6 s, amplitude 20 mm and maximum speed 13.2 mm s−1. At the minimum integration time of 50 ms a tracking algorithm applied to the APS data found all four markers with a success rate of ≥92% and positional error ≤90 μm. At an integration time of 400 ms the smallest marker became difficult to detect when moving. The detection of moving markers using the a‐Si EPID was difficult even at the maximum dose‐rate of 592 MU min−1 due to the lower QE and longer integration time of 400 ms. Conclusions: This work demonstrates that a fast read‐out, high QE APS may be useful in the tracking of moving fiducial markers during radiotherapy. Further study is required to investigate the tracking of markers moving in 3D in a treatment beam attenuated by moving patient anatomy. This will require a larger sensor with ROI read‐out to maintain speed and a manageable data‐rate

Integral application of electrical resistivity tomography, geochemistry and borehole data in groundwater seepage assessment

Electrical resistivity tomography (ERT) has increasingly adopted as an alternative approach in engineering, environmental and archeological studies. In the past, several limitation of conventional method in groundwater mapping was always relative to the high cost, time consuming and limited data coverage. Hence, this study adopted an ERT in order to identify the unknown problematic zone due to the excessive groundwater seepage occurrences. During data acquisition, five (five) ERT spread lines was conducted using ABEM SAS4000 equipment set. Then, field raw data was processed using RES2DINV and ROCKWORKS software to generate 2-D and 3- D of the inverse model resistivity section respectively. Engineering properties and information related to the borehole and geochemistry results was also used for interpretation and verification purposes. Geochemistry test was performed to identify groundwater sources using Atomic Absorption Spectrometer (AAS) and Ion Chromatography (IC) in order to determine the elements of cation (sodium, potassium, calcium and magnesium) and anions (chloride, bicarbonate, nitrate and sulfate) respectively. Based on ERT results, it was found that low electrical resistivity value (10 ~ 100 Ωm) which commonly associated to groundwater was detected at ground surface (0 m) until greater depth (> 10 m). Furthermore, it was found that the groundwater was classified as Ca-HCO that indicates the water was originally come from a typical shallow of the fresh groundwater. Finally, this study has successfully demonstrate that the integral application of ERT, geochemistry and borehole data was applicable to produced comprehensive outcome with particular reference to the problematic groundwater seepage assessment

A review of under-frequency load shedding scheme on TNB system

Safe operation of a power system will require that system frequency is kept within a specified range. When the generation is insuficient due to disturbances, the frequency might fall under the minimum allowable value which may lead to system blackout if not property counteracted. This frequency decline may be corrected by shedding certain amount OC load so that the system is back into balanced state. This paper reports a case study on Malaysia's TNB system. UFLS scheme used by TNB was reviewed, Then modification and improvement was made to reflect the current changes in the system making the scheme more .up to date. Et'fect of having more stages to reduce over shedding and combination of different amount of load at each stage are discussed

Setup uncertainty of head and neck cancer (HNC) patients treated with Image Guided and Intensity Modulated Radiotherapy (IG-IMRT)

Advances in radiotherapy technology has made it possible to deliver highly conformal beams such as Intensity Modulated Radiotherapy (IMRT). The treatment is often guided by on-board cone-beam CT (CBCT) imaging system known as Image Guided Radiotherapy (IGRT). This retrospective study investigates the reproducibility of treatment setup for 25 head-and-neck cancer (HNC) patients underwent IMRT treatment at a new centre using kiloVoltage CBCT based-IGRT. All patients were immobilised using the HeadSTEPTM iFRAME. The planning target volume (PTV) margin was set to 3 mm for all directions during treatment planning. The pre-treatment CBCT imaging was acquired after patient setup. The treatment setup was corrected using online correction protocol for any errors ≥ 3 mm. 231 pre-treatment CBCT scans were acquired and setup errors were recorded in left-right (LR), anterior-posterior (AP) and superior-inferior (SI) directions. The treatment setup error of ≥ 3 mm occurred in 2.2% of measurements in LR direction, 1.7% in AP direction and 6.5% in SI direction. A PTV margin of 2.96 mm, 2.55 mm and 3.30 mm in RL, AP and SI directions, respectively was calculated using Van Herk formula, when no online corrections were performed. After online correction protocol, there were no more setup errors ≥3 mm in all three directions. The PTV margin was reduced to 2.53 mm (LR), 2.39 mm (AP) and 2.81 mm (SI). Therefore, CBCT-based online correction improves the accuracy of IMRT for HNC and reduces irradiated margin by reducing both systematic and random errors

Harmonic currents compensator GCI at the microgrid

The main challenge associated with the grid-connected inverter (GCI) in distributed generation systems is keeping the harmonic content of the output current below the specified value and compensating for unbalanced loads even when the grid is subject to disturbances such as harmonic distortion and unbalanced loads. To overcome these challenges, a current control strategy for a three-phase GCI under unbalanced and nonlinear load conditions is presented. The proposed control method enables the GCI to inject balanced and clean currents to the grid even when the local loads are unbalanced and/or nonlinear; it also compensates for the harmonic currents and controls the active and reactive powers. The main advantage and objective of this method is to effectively compensate for the harmonic current content of the grid current and microgrid without the use of any compensation devices such as active, passive and LCL filters

Medical physicists in Malaysia: A national workforce survey 2019

Objective: Medical physics in Malaysia is still considered a young profession. This workforce survey aims to understand the status, aspirations, motivation and experiences of medical physicists (MPs) in the country. A subsection of this survey also aims to understand the role of women. Method: A survey was carried out between April 20 and May 30, 2018 by a working group under the Medical Physics Division of the Malaysian Institute of Physics (IFM). The survey form was designed using Google Form and sent to various public and private institutions nationwide that employed MPs registered with IFM. Results: A total of 106 responses (28% men and 72% women) were analysed. This represented 30% of the medical physics workforce. Majority of them had postgraduate degrees, but their clinical training is mostly obtained on the job with no certification. The number of low-ranking female MPs was disproportionately high. MPs worked long hours and achieving work-life balance (WLB) was a challenge. Factors that improved their WLB included working close to home, having a supportive manager and flexible working hours. Most MPs aspired to become professional and mentor younger compatriots, besides contributing to patient care and research. Gender discrimination was reportedly low. Conclusion: Medical physics in Malaysia is growing and has a strong representation of women. In future, they would probably take over the top management from their male counterparts, whose number had stagnated. A united effort was essential to set up a proper clinical training system to train clinically qualified MPs. © 2019 Associazione Italiana di Fisica Medic

Time Resolved Radioluminescence of Scintillating Optical Fibre Dosimeters

In radiotherapy, time-resolved radiation dosimetry aids in assessing the efficacy of patient-recommended doses. This work addresses a promising optical fiber dosimetry system technique and its application in external beam radiotherapy, with focus on time-resolved dosimetry. This will be valuable for verification purposes in radiotherap

An improved synchronous reference frame current control strategy for a photovoltaic grid-connected inverter under unbalanced and nonlinear load conditions - Fig 6

<p>System DG unit currents and NLL current waveforms with THD without any compensation: (a) system currents; (b) PV currents; (c) MT currents; (d) FC currents; (e) NLL 1 currents; (f) NLL 2 currents.</p