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Applied Radiation and Isotopes :... Jan 2022Presently, public members are exposed to sources of ionizing radiation, and health risks due to radiation exposures should be a concern. This study aims to calculate the...
Presently, public members are exposed to sources of ionizing radiation, and health risks due to radiation exposures should be a concern. This study aims to calculate the whole-body cumulative radiation exposure of taxi drivers. Also, this study will provide the effect of using a simple lead shield and three types of glass shield AVT6, TZN-D, and SLGC-E5, by calculating the effective annual dose of the taxi drivers that work in medical centers. Two MIRD phantoms as a driver and patient, a sample body of a taxi, pure lead, and glass sheets as a shield, were simulated using the MCNP code. We assumed that the patients had undergone the brain, liver, and kidney SPECT imaging by injecting 99mTC-HMPAO, 99mTC-sulfur colloid, and 99mTC-DMSA with the activity of 740MBq, 185MBq, and 333MBq, respectively. These shields are simulated on two sides of the driver, in the back and right side. The annual effective dose was calculated for 0-3.5 g/cm area densities. It was observed that the 0.45, 1.09, 1.28, and 2.11 g/cm of Pb, TZN-D, AVT6, and SLGC-E5 respectively decrease the effective dose below the allowed limit. According to the results, using the lead shield, the effective dose was reduced by a factor up to 7.25 times. It is recommended that taxi drivers wear a 0.4 mm lead shield or its equivalent when they have Tc-99 m injected patients.
Topics: Automobile Driving; Humans; Lead; Occupational Exposure; Organotechnetium Compounds; Phantoms, Imaging; Radiation Protection
PubMed: 34781074
DOI: 10.1016/j.apradiso.2021.110026 -
Journal of Occupational and... Mar 2022The objective of this study was to determine the influence of face shields on the concentration of respirable aerosols in the breathing zone of the wearer. The...
The objective of this study was to determine the influence of face shields on the concentration of respirable aerosols in the breathing zone of the wearer. The experimental approach involved the generation of poly-dispersed respirable test dust aerosol in a low-speed wind tunnel over 15 min, with a downstream breathing mannequin. Aerosol concentrations were measured in the breathing zone of the mannequin and at an upstream location using two laser spectrophotometers that measured particle number concentration over the range 0.25-31 µm. Three face shield designs were tested (A, B, and C) and were positioned on the mannequin operated at a high and low breathing rate. Efficiency-the reduction in aerosol concentration in the breathing zone-was calculated as a function of particle size and overall, for each face shield. Face shield A, a bucket hat with flexible shield, had the highest efficiency, approximately 95%, while more traditional face shield designs had efficiency 53-78%, depending on face shield and breathing rate. Efficiency varied by particle size, but the pattern differed among face shield designs. Face shields decreased the concentration of respirable aerosols in the breathing zone when aerosols were carried perpendicular to the face. Additional research is needed to understand the impact of face shield position relative to the source.
Topics: Aerosols; Dust; Particle Size; Protective Devices; Respiration
PubMed: 34982641
DOI: 10.1080/15459624.2021.2023163 -
Biomedical Physics & Engineering Express Jan 2020This study was to evaluate dose reduction and resulting image quality of a new synthetic thyroid shield based on silicon rubber (SR)-lead (Pb) composites and compare to...
This study was to evaluate dose reduction and resulting image quality of a new synthetic thyroid shield based on silicon rubber (SR)-lead (Pb) composites and compare to tungsten paper (WP) and a Radibabarrier thyroid shields in CT examination of the neck. The synthetic SR-Pb thyroid shield had a Pb percentage from 0 to 5 wt% and a thickness of 0.6 cm. Scanning on the neck of an anthropomorphic phantom was performed with and without the SR-Pb, WP, and Radibarrier thyroid shields. The thyroid shields were placed directly on the neck surface. The thyroid dose was measured using radiophoto-luminescence (RPL) detectors. Image quality was characterized by consistency of the Hounsfield unit (HU) on the areas of anterior, posterior and lateral of the neck phantom. Detailed evaluation of the image quality was employed by image subtraction. It was found that the thyroid dose at the surface decreased with an increase of Pb percentage in the SR-Pb shield. The thyroid dose reduction was 34% for a Pb percentage of 5 wt%. The reduction of the dose using WP and Radibarrier were 36% and 67%, respectively. The dose reduction when using the WP and Radibarrier was higher than when using the SR-Pb 5 wt% thyroid shield. However the existence of artifact in the WP and the Radibarrier reduced the image quality, indicated by a significant change of HU, i.e. the increases of HU in the posterior area were 77% for the WP and 553% for the Radibarrier. The SR-Pb shield produced only a very small artifact, resulting in an increase of HU in the posterior area of only 9%. The SR-Pb shield is suitable in the daily clinical setting for thyroid dose reduction in CT examinations while maintaining image quality.
Topics: Artifacts; Humans; Phantoms, Imaging; Protective Devices; Radiation Dosage; Radiation Protection; Thyroid Gland; Tomography, X-Ray Computed
PubMed: 33438617
DOI: 10.1088/2057-1976/ab6ed1 -
Canadian Journal of Ophthalmology.... Aug 2023To evaluate the efficacy of patient-sided breath shields in preventing oronasal droplet transmission during slit-lamp examination.
OBJECTIVE
To evaluate the efficacy of patient-sided breath shields in preventing oronasal droplet transmission during slit-lamp examination.
DESIGN
Experimental study testing the efficacy of patient-sided breath shields on a slit lamp.
METHODS
Two commercially available patient-sided breath shields and a 3-dimensional (3D)-printed shield designed by the authors were attached to a slit-lamp chin rest for testing. Each shield was exposed to 3 standardized sprays of coloured dye from a spray gun with its nozzle adjusted to simulate the angular dispersion of a human sneeze. Any overspray not blocked by the shields was recorded and compared with spray with no shield (control). Image-processing software was used to ascertain the surface area of overspray not blocked by the tested shield compared with the control of no shield.
RESULTS
With typical use, both commercially available patient-sided shields and the 3D-printed shield blocked 100% of forward-travelling measurable droplets from a simulated sneeze spray. Even when set to the furthest distance setting to simulate the worst-case scenario, shield 1 and the 3D-printed shield blocked 99.96% and 99.65% of overspray, respectively. However, slow-motion footage did reveal that a considerable amount of spray rebounded off the shields and extended peripherally past its borders.
CONCLUSIONS
With typical use, all tested shields prevented 100% of oronasal transmission. To encourage accessibility, the authors offer a free 3D model and instructions for creating the tested patient-sided breath shield. Patient-sided shields should be combined with other infection-control measures to minimize transmission.
Topics: Humans; Slit Lamp Microscopy; Respiration; Protective Devices; Respiratory Aerosols and Droplets
PubMed: 35231395
DOI: 10.1016/j.jcjo.2022.02.002 -
Nature Communications Jan 2018Most systemic viral gene therapies have been limited by sequestration and degradation of virions, innate and adaptive immunity, and silencing of therapeutic genes within...
Most systemic viral gene therapies have been limited by sequestration and degradation of virions, innate and adaptive immunity, and silencing of therapeutic genes within the target cells. Here we engineer a high-affinity protein coat, shielding the most commonly used vector in clinical gene therapy, human adenovirus type 5. Using electron microscopy and crystallography we demonstrate a massive coverage of the virion surface through the hexon-shielding scFv fragment, trimerized to exploit the hexon symmetry and gain avidity. The shield reduces virion clearance in the liver. When the shielded particles are equipped with adaptor proteins, the virions deliver their payload genes into human cancer cells expressing HER2 or EGFR. The combination of shield and adapter also increases viral gene delivery to xenografted tumors in vivo, reduces liver off-targeting and immune neutralization. Our study highlights the power of protein engineering for viral vectors overcoming the challenges of local and systemic viral gene therapies.
Topics: Adenoviruses, Human; Animals; Capsid Proteins; Cell Line, Tumor; Crystallography, X-Ray; ErbB Receptors; Female; Gene Transfer Techniques; Genetic Vectors; Humans; Liver; Mice, Transgenic; Molecular Targeted Therapy; Receptor, ErbB-2; Single-Chain Antibodies; Spleen; Virion; Xenograft Model Antitumor Assays
PubMed: 29386504
DOI: 10.1038/s41467-017-02707-6 -
European Radiology Apr 2024The aim of the patient out-of-plane shield is to reduce the patient radiation dose. Its effect on tube current modulation was evaluated with the out-of-plane shield...
OBJECTIVES
The aim of the patient out-of-plane shield is to reduce the patient radiation dose. Its effect on tube current modulation was evaluated with the out-of-plane shield visible in the localizer but absent in the scan range in chest CT with different CT scanners.
METHODS
An anthropomorphic phantom was scanned with six different CT scanners from three different vendors. The chest was first scanned without any shielding, and then with the out-of-plane shield within the localizer but outside the imaged volume. All pitch values of each scanner were used. The tube current values with and without the out-of-plane shield were collected and used to evaluate the effect of overscanning and tube current modulation (TCM) on patient radiation dose.
RESULTS
The highest increase in cumulative mA was 217%, when the pitch was 1.531. The tube current value increased already 8.9 cm before the end of the scanned anatomy and the difference between the tube current of the last slices (with and without the out-of-plane shield in the localizer) was 976%.
CONCLUSION
Applying an out-of-plane shield outside the scanned volume but visible in the localizer images may increase the patient dose considerably if the scanner's TCM function is based only on localizer images.
CLINICAL RELEVANCE STATEMENT
The use of an out-of-plane shield in CT may strongly increase the tube current modulation and thus provide the patient with a higher radiation dose.
KEY POINTS
• Applying an out-of-plane shield outside the scanned volume but visible in the localizer images may increase patient radiation dose considerably. • The effect is visible with scanners that use solely localizer-based tube current modulation. • Features like overscanning may be difficult for the user to notice when planning the scanning, and yet they may affect tube current modulation and through it to patient dose.
Topics: Humans; Radiation Dosage; Tomography, X-Ray Computed; Tomography Scanners, X-Ray Computed; Thorax; Phantoms, Imaging
PubMed: 37707547
DOI: 10.1007/s00330-023-10211-3 -
Scientific Reports Aug 2022Magnetically shielded rooms (MSRs) use multiple layers of materials such as MuMetal to screen external magnetic fields that would otherwise interfere with high precision...
Magnetically shielded rooms (MSRs) use multiple layers of materials such as MuMetal to screen external magnetic fields that would otherwise interfere with high precision magnetic field measurements such as magnetoencephalography (MEG). Optically pumped magnetometers (OPMs) have enabled the development of wearable MEG systems which have the potential to provide a motion tolerant functional brain imaging system with high spatiotemporal resolution. Despite significant promise, OPMs impose stringent magnetic shielding requirements, operating around a zero magnetic field resonance within a dynamic range of ± 5 nT. MSRs developed for OPM-MEG must therefore effectively shield external sources and provide a low remnant magnetic field inside the enclosure. Existing MSRs optimised for OPM-MEG are expensive, heavy, and difficult to site. Electromagnetic coils are used to further cancel the remnant field inside the MSR enabling participant movements during OPM-MEG, but present coil systems are challenging to engineer and occupy space in the MSR limiting participant movements and negatively impacting patient experience. Here we present a lightweight MSR design (30% reduction in weight and 40-60% reduction in external dimensions compared to a standard OPM-optimised MSR) which takes significant steps towards addressing these barriers. We also designed a 'window coil' active shielding system, featuring a series of simple rectangular coils placed directly onto the walls of the MSR. By mapping the remnant magnetic field inside the MSR, and the magnetic field produced by the coils, we can identify optimal coil currents and cancel the remnant magnetic field over the central cubic metre to just |B|= 670 ± 160 pT. These advances reduce the cost, installation time and siting restrictions of MSRs which will be essential for the widespread deployment of OPM-MEG.
Topics: Brain; Functional Neuroimaging; Humans; Magnetic Fields; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Magnetoencephalography
PubMed: 35945239
DOI: 10.1038/s41598-022-17346-1 -
Radiography (London, England : 1995) Nov 2022The British Institute of Radiology (BIR) and American Association of Physicists in Medicine (AAPM) have recommended that gonad shielding is no longer used during pelvic... (Meta-Analysis)
Meta-Analysis Review
INTRODUCTION
The British Institute of Radiology (BIR) and American Association of Physicists in Medicine (AAPM) have recommended that gonad shielding is no longer used during pelvic X-ray examinations. The BIR guidance states that shielding may still be considered for use on males, but should not be used on females. This paper aimed to evaluate if this decision was supported by evidence from practice, by comparing the accuracy of gonad shield placement in paediatric males and females.
METHODS
A systematic review of databases including EMBASE, MEDLINE and PubMed was performed in February 2021. Studies were considered eligible if they provided data on the use of gonad shielding during pelvic X-ray examinations on male and female patients under the age of 18. Nine studies met the inclusion criteria and data extraction was performed. Quality appraisal was undertaken, and a meta-analysis of shielding accuracy was performed on seven studies.
RESULTS
The results from the meta-analysis (2187 total radiographs) demonstrated that female patients were significantly more likely (OR 1.38, 95% CI 0.88-1.87) than males to have gonad shields placed inaccurately (p value < 0.001).
CONCLUSION
Gonad shield placement on paediatric female patients is significantly less accurate than on males, and so the results support the AAPM and BIR guidance to stop the practice for females. Shield application may also be frequently inaccurate for males, but the review does not provide clear evidence for or against continuing the practice for males.
IMPLICATIONS FOR PRACTICE
Discontinuing the use of gonad shields in paediatric pelvic radiography on female patients is supported. Any continued use on male patients, or for reasons such as psychological reassurance, should be subject to enhanced training and audit to ensure benefits outweigh any risks.
Topics: Child; Female; Gonads; Humans; Male; Pelvis; Physical Examination; Radiation Protection; Radiography
PubMed: 35849887
DOI: 10.1016/j.radi.2022.06.009 -
Magnetic Resonance in Medicine Dec 2022An array-based z-gradient coil with a set of programmable power amplifiers can outperform a conventional z-gradient coil and make it highly customizable with a broader...
PURPOSE
An array-based z-gradient coil with a set of programmable power amplifiers can outperform a conventional z-gradient coil and make it highly customizable with a broader range of tunable features.
METHODS
A dynamically adjustable imaging volume can be achieved using a pair of independent arrays and a modified optimization procedure based on analytic equations. Two modes of operation are provided: (a) standard mode that resembles a conventional coil; (b) advanced mode, where all performance parameters can be adjusted employing a controllable feeding mechanism. Commercial software is used to demonstrate the validity and feasibility of the proposed coil.
RESULTS
Primary and shield array diameters are 24 and 30 cm, both of which comprise 12 bundles of 10 turns copper wires. Maximum feeding voltage/current is 250 V/100 A for all array elements. Four distinct magnetic profiles are provided: (a) conventional profile with 140 mm diameter spherical region of interest, 120 mT/m gradient, and up to 4500 T/m/s slew rate; (b) profile of 200 mT/m, 70 mm region of interest, and up to 6900 T/m/s slew rate; (c) 60 mm axially shifted 70 mm region of interest with 120 mT/m strength and 3600 T/m/s slew rate; and (d) profile of 370 mT/m, 120 mm region of interest, and 3700 T/m/s slew rate when the active shield is reverse fed.
CONCLUSION
By using an active-shielded gradient array coil, the magnetic field profile of the imaging volume can be adjusted dynamically, and it can provide new features and a wide range of field profiles for diverse applications in MRI.
Topics: Copper; Equipment Design; Magnetic Fields; Magnetic Resonance Imaging; Software
PubMed: 35916334
DOI: 10.1002/mrm.29390 -
Solid State Nuclear Magnetic Resonance Apr 2024The development of NMR crystallography methods requires a reliable database of chemical shifts measured for systems with known crystal structure. We measured and...
The development of NMR crystallography methods requires a reliable database of chemical shifts measured for systems with known crystal structure. We measured and assigned carbon and hydrogen chemical shifts of twenty solid natural amino acids of known polymorphic structure, meticulously determined using powder X-ray diffraction. We then correlated the experimental data with DFT-calculated isotropic shieldings. The small size of the unit cell of most amino acids allowed for advanced computations using various families of DFT functionals, including generalized gradient approximation (GGA), meta-GGA and hybrid DFT functionals. We tested several combinations of functionals for geometry optimizations and NMR calculations. For carbon shieldings, the widely used GGA functional PBE performed very well, although an improvement could be achieved by adding shielding corrections calculated for isolated molecules using a hybrid functional. For hydrogen nuclei, we observed the best performance for NMR calculations carried out with structures optimized at the hybrid DFT level. The high fidelity of the calculations made it possible to assign additional signals that could not be assigned based on experiments alone, for example signals of two non-equivalent molecules in the unit cell of some of the amino acids.
Topics: Crystallography; Amino Acids; Magnetic Resonance Spectroscopy; Carbon; Hydrogen
PubMed: 38422809
DOI: 10.1016/j.ssnmr.2024.101921