Status of Domestic and International Recommendations for Protection Design and Evaluation of Medical Linear Accelerator Facilities

Various types of high-precision radiotherapy, such as intensity-modulated radiation therapy (IMRT), tomotherapy (Tomo), and stereotactic body radiation therapy have been available since 1997. After being covered by insurance in 2015, the number of IMRT cases rapidly increased 18-fold from 2011 to 2018 in Korea. IMRT, which uses a high-beam irradiation monitor unit, requires higher shielding conditions than conventional radiation treatments. However, to date, research on the shielding of facilities using IMRT and the current understanding of its status are insufficient, and detailed safety regulation procedures have not been established. This study investigated the recommended criteria for the shielding evaluation of facilities using medical linear accelerators (LINACs), including 1) the current status of safety management regulations and systems in domestic and international facilities using medical LINACs and 2) the current status of the recommended standards for safety management in domestic and international facilities using medical LINACs. It is necessary to develop and introduce a safety management system for facilities using LINACs for clinical applications that is suitable for the domestic medical environment and corresponds to the safety management systems for LINACs used overseas.ope

Evaluation of the Influence of Additional Beam Filtration on Image Quality and Patient Dose in X-ray Fluoroscopy Procedures

The aim of the study was to evaluate the influence of additional filtration on radiation dose and image quality for patients during hysterosalpingography (HSG) and retrograde urethrography (RUG) procedures. The influence of filtering on image quality for each phantom thickness was made using a combination of different filter thicknesses. Entrance surface air kerma (ESAK) rates to Perspex phantom were measured using a solid state detector for various added combination of filter materials. Fluoroscopic image contrast was assessed using a Leeds TOR-18FG test object with a range of filter materials and phantom thicknesses. Phantom studies demonstrated that the use of additional filter materials of up to 0.35 mm thickness of copper could be used without significant effect on the image quality. ESAK values were determined for 16, 20, 24 and 28 cm phantom. Phantom ESAK reduced by 63%, 63%, 64% and 65% for 16, 20, 24 and 28 cm, respectively, when using 0.35 mm Cu + 1 mmAl, without degrading image contrast. Three independent radiologists perceived no change in clinical image quality with added filtration. On adding 0.35 mm Cu and 1 mm Al, the KAP per examination for the HSG was reduced by 71%, while for the RUG was reduced by 75%.Key words: Additional filtration; image quality; patient dose; X-ray fluoroscopy procedure

Determination of Radiation Doses to Patients Undergoing Fluoroscopically Guided Orthopaedic Procedures at Muhimbili Orthopaedic Institute in Tanzania

The aim of the present study was to determine the magnitude of radiation doses delivered to patients undergoing Fluoroscopically Guided Orthopaedic Procedures (FGOP’s) in Tanzania. The air Kerma Area Product (KAP), fluoroscopy time, organ dose and effective dose to patients undergoing FGOP’s were obtained from Muhimbili Orthopaedic Institute. A total of 72 adult patients from selected three FGOPs namely Lumbar Spine (LS), Dynamic Hip Screw (DHS) and Thoracic Spine (TS) procedures were investigated using C-arm fluoroscopy machine. The knowledge of patient demographic data, radiographic data, KAP and Monte Carlo-based PCXMC software were used to obtain the magnitude of organ doses (OD) and effective doses (ED) of the patients. The median values of KAP for the LS, DHS and TS were 2.569, 2.410 and 0.770 Gy cm2, respectively. The mean values of ED for the LS, DHS, and TS procedures were 0.27, 0.47 and 2.70 mSv, respectively. The observed wide variations of KAP, organ dose, effective and exposure protocols within the hospital under study and relative high dose in this study compared to reported values from the literature call for standardization of procedural protocols and optimize fluoroscopically guided orthopaedic procedures. Keywords: Kerma-area-product; organ dose; effective dose; C-arm fluoroscopy machine; orthopaedic proceduresDetermination of Radiation Doses to Patients Undergoing Fluoroscopically Guided Orthopaedic Procedures at Muhimbili Orthopaedic Institute in Tanzani

Radiotherapy electron beams collimated by small tubular applicators: Characterization by silicon and diamond diodes

High-energy electron beams generated by linear accelerators, typically in the range 6 to 20 MeV, are used in small field sizes for radiotherapy of localized superficial tumors. Unshielded silicon diodes (Si-D) are commonly considered suitable detectors for relative dose measurements in small electron fields due to their high spatial resolution. Recently, a novel synthetic single crystal diamond diode (SCDD) showed suitable properties for standard electron beams and small photon beams dosimetry. The aim of the present study is twofold: to characterize 6 to 15 MeV small electron beams shaped by using commercial tubular applicators with 2, 3, 4 and 5 cm diameter and to assess the dosimetric performance under such irradiation conditions of the novel SCDD dosimeter by comparison with commercially available dosimeters, namely a Si-D and a plane-parallel ionization chamber. Percentage depth dose curves, beam profiles and output factors (OFs) were measured. A good agreement among the dosimeters was observed in all of the performed measurements. As for the tubular applicators, two main effects were evidenced: (i) OFs larger than unity were measured for a number of field sizes and energies, with values up to about 1.3, that is an output 30% greater than that obtained at the 10 × 10 cm 2 reference field; (ii) for each diameter of the tubular applicator a noticeable increase of the OF values was observed with increasing beam energy, up to about 100% in the case of the smaller applicator. This OF behavior is remarkably different from what typically observed for small blocked fields having the same size and energy as those used in this study. OFs for tubular applicators depend considerably on the field size, so interpolation is unadvisable to predict the linear accelerator output for such applicators whereas reliable high-resolution detectors, as the silicon and diamond diodes used in this work allow OF measurements with uncertainties of about 1%. © 2013 Institute of Physics and Engineering in Medicine. Printed in the UK & the USA

A research study on Hong Kong's building services engineering profession: a review of the building services engineering profession in the United Kingdom

A review of the building services engineering profession in the United Kingdom is considered in this document. It provides supporting information for a comprehensive study into the profession in Hong Kong which is being conducted by Hong Kong Polytechnic University on behalf of the Hong Kong Institution of Engineers. The overall aim of the work is to investigate mechanisms for raising the profile of building services engineers in Hong Kong

A GPU Simulation Tool for Training and Optimisation in 2D Digital X-Ray Imaging

Conventional radiology is performed by means of digital detectors, with various types of technology and different performance in terms of efficiency and image quality. Following the arrival of a new digital detector in a radiology department, all the staff involved should adapt the procedure parameters to the properties of the detector, in order to achieve an optimal result in terms of correct diagnostic information and minimum radiation risks for the patient. The aim of this study was to develop and validate a software capable of simulating a digital X-ray imaging system, using graphics processing unit computing. All radiological image components were implemented in this application: an X-ray tube with primary beam, a virtual patient, noise, scatter radiation, a grid and a digital detector. Three different digital detectors (two digital radiography and a computed radiography systems) were implemented. In order to validate the software, we carried out a quantitative comparison of geometrical and anthropomorphic phantom simulated images with those acquired. In terms of average pixel values, the maximum differences were below 15%, while the noise values were in agreement with a maximum difference of 20%. The relative trends of contrast to noise ratio versus beam energy and intensity were well simulated. Total calculation times were below 3 seconds for clinical images with pixel size of actual dimensions less than 0.2 mm. The application proved to be efficient and realistic. Short calculation times and the accuracy of the results obtained make this software a useful tool for training operators and dose optimisation studies

What Is Worth Knowing in Interventional Practices about Medical Staff Radiation Exposure Monitoring: A Review of Recent Outcomes of EURADOS Working Group 12

EURADOS (European Radiation Dosimetry Group) Working Group 12 (WG12) SG1 activities are aimed at occupational radiation protection and individual monitoring in X-ray and nuclear medicine practices. In recent years, many studies have been carried out in these fields, especially for interventional radiology and cardiology workplaces (IC/IR). The complexity of the exposure conditions of the medical staff during interventional practices makes the radiation protection and monitoring of the exposed workers a challenging task. The scope of the present work is to review some of the main results obtained within WG12 activities about scattered field characterization and personal dosimetry that could be very useful in increasing the quality of radiation protection of the personnel, safety, and awareness of radiation risk. Two papers on Monte Carlo modelling of interventional theater and three papers on active personal dosimeters (APDs) for personnel monitoring were considered in the review. More specifically, Monte Carlo simulation was used as the main tool to characterize the levels of exposure of the medical staff, allowing to determine how beam energy and direction can have an impact on the doses received by the operators. Indeed, the simulations provided information about the exposure of the operator’s head, and the study concluded with the determination of an eye-lens protection factor when protection goggles and a ceiling shielding are used. Moreover, the review included the results of studies on active personal dosimeters, their use in IC/IR workplaces, and how they respond to calibration fields, with X-ray standard and pulsed beams. It was shown that APDs are insensitive to backscatter radiation, but some of them could not respond correctly to the very intense pulsed fields (as those next to the patient in interventional practices). The measurements during interventional procedures showed the potential capability of the employment of APDs in hospitals

Quality assurance of radiodiagnostic equipment -Overview of literature since 2004

Het Britse handboek voor de kwaliteitsborging (Quality Assurance) van CT-scanners en andere rontgentoestellen, kan met enkele aanpassingen ook in Nederland gebruikt worden. Dit blijkt uit een literatuurstudie van het RIVM naar de kwaliteitsborging van deze apparaten. Beelden van CT-scanners en andere rontgentoestellen moeten goed genoeg zijn om een juiste diagnose te kunnen stellen. Ze worden gemaakt met rontgenstraling en die is schadelijk voor de gezondheid. De beelden worden echter vaak beter als er meer straling wordt gebruikt. Om goede beelden te krijgen met een zo laag mogelijke stralingsdosis is er veel aandacht nodig voor het optimaal laten functioneren van de apparatuur. Het geheel van maatregelen die hieraan bijdragen wordt kwaliteitsborging genoemd. Er is in Nederland geen algemeen handboek voor de kwaliteitsborging van CT-scanners en andere rontgenapparaten. Uit het onderzoek van het RIVM blijkt dat het Britse handboek, aangevuld met enkele andere documenten, vrij eenvoudig naar de Nederlandse praktijk vertaald kan worden. Wel is er nog een enkele toevoeging nodig en moeten grenswaarden worden aangepast aan de Nederlandse regelgeving.The British handbook on quality assurance of CT and other x-ray equipment may, with some adaptations, also be used in the Netherlands. This is the main conclusion of a literature study by RIVM on quality assurance of such equipment. Images from CT scanners and other x-ray equipment must have sufficient quality to enable a correct diagnosis. They are obtained using x-rays, which have adverse health effects. However, in diagnostic imaging, higher x-ray doses often lead to better image quality. To obtain good images while keeping the radiation dose as low as reasonably achievable, much attention is needed for the optimal performance of the equipment. Quality assurance is the complex of all measures needed to achieve this. A general handbook on quality assurance of CT and other x-ray equipment adapted to the Dutch practice does not exist. The literature study by RIVM shows that it should be relatively straightforward to adapt, with some additions, the British handbook to the Dutch practice and legislation.Inspectie voor de Gezondheidszor

Computation of Electromagnetic Fields in Assemblages of Biological Cells Using a Modified Finite-Difference Time-Domain Scheme

When modeling objects that are small compared with the wavelength, e.g., biological cells at radio frequencies, the standard finite-difference time-domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating a generic lumped-element membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computation-ally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900, 1800, and 2450 MHz. This method will facilitate deeper investigation of the phenomena in the interaction between electromagnetic fields and biological systems. Index Terms-Finite difference time domain (FDTD), Floquet periodic boundary conditions, quasi-static method