Optimizing non-Pb radiation shielding materials using bilayers

Study of the effect of implantation temperature on the migration behaviour of Xe implanted into glassy carbon

The effect of implantation temperature on the migration behaviour of xenon (Xe) implanted into glassy carbon and the effect of annealing on radiation damage retained by ion implantation were investigated. Glassy carbon substrates were implanted with 320 keV Xe+ to a fluence of 2 × 1016 cm-2. The implantation process was performed at room temperature (RT) and 100 °C Some of the as-implanted samples were isochronally annealed in vacuum at temperatures ranging from 300 °C to 700 °C in steps of 100 °C for 10 h. The as-implanted and annealed samples were characterized using Rutherford backscattering spectrometry (RBS) and Raman spectroscopy. The RT implanted depth profiles indicated that the migration of Xe towards the surface of glassy carbon was accompanied by a loss of Xe ions. The samples implanted at 100 °C indicated no diffusion or loss of Xe after annealing at 300 °C. However, annealing at temperatures ranging from 400 °C to 700 °C resulted in a slight shift in the Xe profile tail-end towards the bulk of glassy carbon. The diffusion coefficients (D) in the temperature range of 300 °C-700 °C for the RT and 100 °C implanted samples, activation energies (Ea), and pre-exponential factors (Do), were extracted. The values of D ranged from (9.72 ± 0.48) × 10-21 to (1.87 ± 0.09) × 10-20 m2/s with an activation energy of (6.25 ± 0.31) × 10-5 eV for RT implanted samples, and the samples implanted at 100 °C, D ranged from (3.85 ± 0.19) × 10-21 to (6.96 ± 0.34) × 10-20 m2/s with activation energy of (4.10 ± 0.02) × 10-5 eV. The Raman analysis revealed that implantation at the RT amorphised the glassy carbon structure while the samples implanted at 100 °C showed mild damage compared to RT implantation. Annealing of the RT-implanted sample resulted in some recovery of the damaged region as a function of increasing annealing temperature.

Performance of elastic x-ray shield made by embedding Bi2 O3 particles in porous polyurethane

BACKGROUND

Many healthcare institutions have guidelines concerning the usage of protective procedures, and various x-ray shields have been used to reduce unwanted radiation exposure to medical staff and patients when using x-rays. Most x-ray shields are in the form of sheets and lack elasticity, which limits their effectiveness in shielding areas with movement, such as the thyroid. To overcome this limitation, we have developed an innovative elastic x-ray shield.

PURPOSE

The purpose of this study is to explain the methodology for developing and evaluating a novel elastic x-ray shield with sufficient x-ray shielding ability. Furthermore, valuable knowledge and evaluation indices are derived to assess our shield's performance.

METHODS

Our x-ray shield was developed through a process of embedding Bi2 O3 particles into porous polyurethane. Porous polyurethane with a thickness of 10 mm was dipped into a solution of water, metal particles, and chemical agents. Then, it was air-dried to fix the metal particles in the porous polyurethane. Thirteen investigational x-ray shields were fabricated, in which Bi2 O3 particles at various mass thicknesses (ranging from 585 to 2493 g/m2 ) were embedded. To determine the performance of the shielding material, three criteria were evaluated: (1) Dose Reduction Factor (D R F $DRF$ ), measured using inverse broad beam geometry; (2) uniformity, evaluated from the standard deviation (S D $SD$ ) of the x-ray image obtained using a clinical x-ray imaging detector; and (3) elasticity, evaluated by a compression test.

RESULTS

The elastic shield with small pores, containing 1200 g/m2 of the metal element (Bi), exhibited a well-balanced performance. TheD R F $DRF$ was approximately 80% for 70 kV diagnostic x-rays. This shield's elasticity was -0.62 N/mm, a loss of only 30% when compared to porous polyurethane without metal. Although the non-uniformity of the x-ray shield leads to poor shielding ability, it was found that the decrease in the shielding ability can be limited to a maximum of 6% when the shield is manufactured so that theS D $SD$ of the x-ray image of the shield is less than 10%.

CONCLUSIONS

It was verified that an elastic x-ray shield that offers an appropriate reduction in radiation exposure can be produced by embedding Bi2 O3 particles into porous polyurethane. Our findings can lead to the development of novel x-ray shielding products that can reduce the physical and mental stress on users.

Heavy alloy based on tungsten and bismuth: fabrication, crystal structure, morphology, and shielding efficiency against gamma-radiation

W-Bi2O3 composites were fabricated using the hot isostatic pressing technique for the first time. The duration of the samples sintering was 3 minutes under conditions of high pressure and temperature. The study of microstructural features and chemical composition of sintered samples was carried out using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The effect of temperature on the quality of the obtained W-Bi2O3 composites is determined. The densest samples were obtained at a pressure of 5 GPa and temperatures of 25 °C and 500 °C, the densities of which were 18.10 and 17.85 g cm-3, respectively. It is presented that high temperature exposure during sintering adversely affects both the composite density and microstructure due to the redox reaction accompanied by the reduction of Bi and the oxidation of W. The results of the W-Bi2O3 structure study using X-ray diffraction analysis showed that all samples included the main bulk-centered cubic W phase. The presence of the WO2 phase is noted only when the sintering temperature is increased up to 850 °C, which is confirmed by the appearance of diffraction peaks that correspond to 111 and 22-2 crystallographic planes. The shielding efficiency of the W-Bi2O3 composite against gamma radiation using the Phy-X/PSD software was evaluated. A Co60 isotope with an energy of 0.826-2.506 MeV was used as a source of gamma radiation. The calculation results were compared with those for Pb and Bi. Key shielding parameters such as the linear attenuation coefficient, half-value layer, tenth-value layer, mean free path, and effective atomic number are determined. The calculation results revealed that the W-Bi2O3 composite surpasses Pb and Bi in its shielding properties, which makes it promising for use as a prospective material for radiation shielding applications.

Evaluation of the radiation protection effectiveness of a lead-free homopolymer in cone beam computed tomography

OBJECTIVE

The objective was to compare the radiation protection effectiveness of a lead-free thermoplastic homopolymer (Anti-RAD) to conventional lead shielding in cone beam computed tomography (CBCT) exposures.

STUDY DESIGN

Thermoluminescent dosimeters were placed on a human bone- and soft tissue-equivalent phantom to record equivalent doses in the thyroid gland, thyroid skin, and breast areas. CBCT images were obtained with the following 3 protocols: (1) without radiation shielding; (2) with 0.5-mm lead equivalent lead-containing shielding; and (3) with 0.5-mm lead equivalent Anti-RAD shielding. Independent t tests were used to evaluate the results.

RESULTS

Compared with exposures without shielding, both lead and Anti-RAD protective devices reduced thyroid gland equivalent doses by approximately 40%, thyroid skin doses by approximately 75%, right breast skin doses by approximately 80%, and left breast skin doses by 75%. The differences in equivalent dose for both types of shielding compared with exposure with no shielding were statistically significant (P ≤ .042). However, there were no significant differences in dose reduction at any site between lead and Anti-RAD shielding (P ≥ .135).

CONCLUSIONS

Radiation protection equivalent to lead can be provided with the Anti-RAD shield. With the use of this material, disadvantages such as damage to the aprons, lead toxicity, weight of lead aprons, and microbial contamination can be reduced.

Views on Radiation Shielding Efficiency of Polymeric Composites/Nanocomposites and Multi-Layered Materials: Current State and Advancements

This article highlights advancements in polymeric composite/nanocomposites processes and applications for improved radiation shielding and high-rate attenuation for the spacecraft. Energetic particles, mostly electrons and protons, can annihilate or cause space craft hardware failures. The standard practice in space electronics is the utilization of aluminum as radiation safeguard and structural enclosure. In space, the materials must be lightweight and capable of withstanding extreme temperature/mechanical loads under harsh environments, so the research has focused on advanced multi-functional materials. In this regard, low-Z materials have been found effective in shielding particle radiation, but their structural properties were not sufficient for the desired space applications. As a solution, polymeric composites or nanocomposites have been produced having enhanced material properties and enough radiation shielding (gamma, cosmic, X-rays, protons, neutrons, etc.) properties along with reduced weight. Advantageously, the polymeric composites or nanocomposites can be layered to form multi-layered shields. Hence, polymer composites/nanocomposites offer promising alternatives to developing materials for efficiently attenuating photon or particle radiation. The latest technology developments for micro/nano reinforced polymer composites/nanocomposites have also been surveyed here for the radiation shielding of space crafts and aerospace structures. Moreover, the motive behind this state-of-the-art overview is to put forward recommendations for high performance design/applications of reinforced nanocomposites towards future radiation shielding technology in the spacecraft.

Lead Free Multilayered Polymer Composites for Radiation Shielding

Silicone-based polymer composites containing high atomic number additives are prioritized for the development of new materials for radiation shielding, due to their mechanical, thermal, electrical, and multifunctional properties. The X-ray attenuation properties, as well as mechanical properties, of the newly developed-lead-free multi-layered structures for radiation shielding, based on silicone composite layers containing tin, cerium oxide, tungsten oxide, and bismuth additives, are analyzed and discussed in this paper. It is shown that, by varying the additive concentrations in silicone composites, lead-free and flexible layered structures, exhibiting lead-equivalent X-ray shielding, can be fabricated.

A comprehensive Monte Carlo study to design a novel multi-nanoparticle loaded nanocomposites for augmentation of attenuation coefficient in the energy range of diagnostic X-rays

Introduction: The present study aimed to investigate the radiation protection properties of silicon-based composites doped with nano-sized Bi2O3, PbO, Sm2O3, Gd2O3, WO3, and IrO2 particles. Radiation shielding properties of Sm2O3 and IrO2 nanoparticles were investigated for the first time in the current study.

Material and methods: The MCNPX (2.7.0) Monte Carlo code was utilized to calculate the linear attenuation coefficients of single and multi-nano structured composites over the X-ray energy range of 10–140 keV. Homogenous distribution of spherical nanoparticles with a diameter of 100 nm in a silicon rubber matrix was simulated. The narrow beam geometry was used to calculate the photon flux after attenuation by designed nanocomposites.

Results: Based on results obtained for single nanoparticle composites, three combinations of different nano-sized fillers Sm2O3+WO3+Bi2O3, Gd2O3+WO3+Bi2O3, and Sm2O3+WO3+PbO were selected, and their shielding properties were estimated. In the energy range of 20-60 keV Sm2O3 and Gd2O3 nanoparticles, in 70-100 keV energy range WO3 and for photons energy higher than 90 keV, PbO and Bi2O3 nanoparticles showed higher attenuation. Despite its higher density, IrO2 had lower attenuation compared to other nanocomposites. The results showed that the nanocomposite containing Sm2O3, WO3, and Bi2O3 nanoparticles provided better shielding among the studied samples.

Conclusions: All studied multi-nanoparticle nanocomposites provided optimum shielding properties and almost 8% higher attenuation relative to single nano-based composites over a wide range of photon energy used in diagnostic radiology. Application of these new composites is recommended in radiation protection. Further experimental studies are suggested to validate our findings.

A simple quality control tool for assessing integrity of lead equivalent aprons

Background

Protective lead or lead-equivalent (Pbeq) aprons play a key role in providing necessary shielding from secondary radiation to occupational workers. Knowledge on the integrity of these shielding apparels during purchase is necessary to maintain adequate radiation safety.

Aim

The aim of the study was to evaluate the lead equivalence in aprons based on simple quality assessment tool.

Materials and Methods

0.25 mm and 0.5 mm lead and lead-free aprons from 6 manufacturers were assessed using a calibrated digital X-ray unit. The percentage attenuation values of the aprons were determined at 100 kVp using an ionization chamber and the pixel intensities were analyzed using digital radiographic images of lead apron, copper step wedge tool, and 2 mm thick lead.

Results

Mean radiation attenuation of 90% and 97% was achieved in 0.25 mm and 0.5 mm lead or lead-free aprons respectively. The pixel intensities from 0.25 mm Pbeq apron correspond to 0.8-1.2 mm thickness of Cu while 0.5 mm Pbeq aprons correspond to 2.0-2.8 mm of Cu.

Conclusion

Pixel intensity increased with increase in the thickness of copper step wedge indicating a corresponding increase in lead equivalence in aprons. It is suggestive that aprons should be screened for its integrity from the time of purchase using computed tomography (CT), fluoroscopy, or radiography. It is recommended that this simple test tool could be used for checking lead equivalence if any variation in contrast is seen in the image during screening.

Analysis of Shielding Performance of Radiation-Shielding Materials According to Particle Size and Clustering Effects

In the field of medical radiation shielding, there is an extensive body of research on process technologies for ecofriendly shielding materials that could replace lead. In particular, the particle size and arrangement of the shielding material when blended with a polymer material affect shielding performance. In this study, we observed how the particle size of the shielding material affects shielding performance. Performance and particle structure were observed for every shielding sheet, which were fabricated by mixing microparticles and nanoparticles with a polymer material using the same process. We observed that the smaller the particle size was, the higher both the clustering and shielding effects in the high-energy region. Thus, shielding performance can be improved. In the low-dose region, the effect of particle size on shielding performance was insignificant. Moreover, the shielding sheet in which nanoparticles and microsized particles were mixed showed similar performance to that of the shielding sheet containing only microsized particles. Findings indicate that, when fabricating a shielding sheet using a polymer material, the smaller the particles in the high-energy region are, the better the shielding performance is. However, in the low-energy region, the effect of the particles is insignificant.

Designing and Fabricating Nano-structured and Micro-structured Radiation Shields for Protection against CBCT Exposure

Researchers have always been interested in finding new and effective materials for protection against radiation. This experimental study aimed to design and fabricate new types of nano-material and micro-material based shields against the ionizing effect of cone beam computed tomography (CBCT) X-rays. To fabricate a flexible prototype, we added dioctyl phthalate (DOP) oil to emulsion polyvinyl chloride (PVC) powder. The paste was mixed and dispersed. Then, nano- and micro-powders of WO₃ and Bi₂O₃ were added to the paste, with the weight ratio of 20% PVC, 20% DOP, and 60% nano- and micro-metals. Using an ultrasonic mixer, the polymer matrix and metals were mixed and a paste with a thick texture was developed. The resultant paste was poured into glass molds and the molds were then heated in an oven. After cooling, the resultant sheets were selected for further experiments. A CBCT unit and dosimeter were used to evaluate the characterization and X-ray shielding properties of the fabricated prototypes. The half-value layers (HVL) for nano-WO₃, micro-WO₃, nano-Bi₂O_3, and micro-Bi₂O₃ were 0.0390, 0.0524, 0.0351, and 0.0374 cm, respectively. In addition, the linear attenuation coefficient (µ) for these materials were 17.77, 13.20, 19.71, and 18.5 cm⁻¹, respectively. The findings indicate that nano-structured samples are more effective in the attenuation of X-ray energy. The nano-structured WO₃ prototype was nearly 34% more efficient in attenuating radiation compared to the micro-structured WO₃ prototype. This difference in nano- and micro-structured Bi₂O₃ prototypes was 6.5%.

Early-Stage Growth Mechanism and Synthesis Conditions-Dependent Morphology of Nanocrystalline Bi Films Electrodeposited from Perchlorate Electrolyte

Bi nanocrystalline films were formed from perchlorate electrolyte (PE) on Cu substrate via electrochemical deposition with different duration and current densities. The microstructural, morphological properties, and elemental composition were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray microanalysis (EDX). The optimal range of current densities for Bi electrodeposition in PE using polarization measurements was demonstrated. For the first time, it was shown and explained why, with a deposition duration of 1 s, co-deposition of Pb and Bi occurs. The correlation between synthesis conditions and chemical composition and microstructure for Bi films was discussed. The analysis of the microstructure evolution revealed the changing mechanism of the films’ growth from pillar-like (for Pb-rich phase) to layered granular form (for Bi) with deposition duration rising. This abnormal behavior is explained by the appearance of a strong Bi growth texture and coalescence effects. The investigations of porosity showed that Bi films have a closely-packed microstructure. The main stages and the growth mechanism of Bi films in the galvanostatic regime in PE with a deposition duration of 1–30 s are proposed.

Radiation dose reduction to the eye lens in head CT using tungsten functional paper and organ-based tube current modulation

PURPOSE

We investigated whether a tungsten functional paper (TFP) shield and/or organ-based tube current modulation (TCM) can reduce the dose to the eye lens.

MATERIALS AND METHODS

All scans were performed using our routine head examination protocol (spiral acquisition, 120 kVp, noise Index 3.5) with an anthropomorphic head phantom. The dose reduction rate was measured by the following methods with a scintillation fiber optic dosimeter: (a) without any dose reduction techniques (Original scan), (b) TFP shield, (c) TCM, and (d) TFP shield plus TCM. Image noise and CT number were obtained and compared between the three groups. In addition, image noise in method (d) was measured with varying distances between the TFP shield and eye lens.

RESULTS

The reduction rates using TFP shield, TCM, and TFP shield plus TCM compared with those for the Original scan were 17.8 %, 13.6 %, and 27.7 %, respectively. Image noise (mean ± standard deviation) in the anterior region for the Original scan, TFP shield, TCM, and TFP shield plus TCM were 4.1 ± 0.2, 4.6 ± 0.2, 4.4 ± 0.3, and 5.0 ± 0.2, while the CT numbers were 19.3 ± 0.8, 23.8 ± 0.8, 19.6 ± 0.8, and 24.1 ± 0.8, respectively. Increasing the distance between the TFP and the eye significantly decreased the CT number when using TFP shield plus TCM (p < .05).

CONCLUSION

TFP shield plus TCM reduced the dose to the eye lens in head CT while maintaining image quality with an air gap between the TFP and skin surface.

Don't be Caught Half-dressed When Working with Radiation

A typical 2-piece personal protective equipment apron covers only half the body. However, with radiation exposure there is evidence of the following: (1) Left-sided head exposure estimates equal to 100,000 chest X-rays over a 20-year career, (2) direct linear relationship between stroke and concentration of dose, (3) increases in ischemic heart disease and myocardial infarction, (4) accelerated aging processes, and (5) increased double-stranded DNA breaks in circulating lymphocytes when lower legs are exposed. Every exposure to ionizing radiation involves a health risk that accumulates. Interventionalists are treating more patients, more complex patients, using new complicated devices. Juxtaposed with the global obesity epidemic, the result is an unprecedented level of radiation exposure for those who use radiation in their daily work. By implementing a simple system of shields, we can dramatically reduce our radiation dose. This would give us a better chance to live a longer, healthier life, and pass quality DNA to our children. This narrative review examines the efficacy of protective barriers to reduce medical occupational radiation exposure and risk.

Biological polymeric shielding design for an X-ray laboratory using Monte Carlo codes

Photon irradiation facilities are often shielded using lead despite its toxicity and high cost. In this study, three Monte Carlo codes, EGS5, MCNPX, and Geant4, were utilized to investigate the efficiency of a relatively new polymeric base compound (C_nH_2n), as a radiation shielding material for photons with energies below 150 keV. The proposed compound with the densities of 6 and 8 g cm^-3 were doped with the weight percentages of 8.0 and 15.0% gadolinium. The probabilities of photoelectric effect and Compton scattering were relatively equal at low photon energies, thus the shielding design was optimized using three Monte Carlo codes for the conformity of calculation results. Consequently, 8% Gd-doped polymer with thickness less than 2 cm and density of 6 g cm^-3 was adequate for X-ray room shielding to attenuate more than 95% of the 150-keV incident photons. An average dose rate reduction of 88% can be achieved to ensure safety of the radiation area.

Use of tungsten sheet as an alternative for reducing the radiation dose behind the digital imaging plate during intra-oral radiography

OBJECTIVES

To verify the use of tungsten sheet as an alternative to lead foil for reducing the radiation dose behind storage phosphor plates (SPPs).

METHODS

At six sites (incisor, canine, and molar sites in both the maxilla and mandible) in a head phantom, radiation doses were initially measured behind conventional film packets containing two films and a lead foil. At the same sites, radiation doses were also measured behind packets containing only SPPs. Thereafter, the same dose measurements were performed with shielding materials (lead foil or tungsten sheet) within the packets. These doses were defined as behind doses.

RESULTS

There were no differences in the mean behind doses between the conventional film packets and the SPP packets without shielding materials for any of the six sites examined. The behind doses were reduced by both lead foil and tungsten sheet, with significant differences in all sites when compared with no shielding. Lead foil reduced the behind dose of the SPP packet to 37.6% on average, while tungsten sheet reduced the behind dose to less than 20% in all of the sites examined, with an average of 14.7%.

CONCLUSIONS

Tungsten sheet appeared to be effective as an alternative shielding material, sufficiently reducing the doses behind the SPP packets to less than 20% when compared with sheetless packets in all of the six sites examined.

Are Antimony-Bismuth Aprons as Efficient as Lead Rubber Aprons in Providing Shielding against Scattered Radiation?

AIM

The aim of this study is to compare the absorption ability of two lead-free aprons with a lead apron.

METHOD

The absorption ability of three aprons was measured and compared; Opaque Fusion 0.35 mm (OpaqFu) bilayer apron containing bismuth and antimony, No Lead 0.35 mm (NoLead) one-layer apron containing antimony, and a lead apron. The measurements were repeated with and without each of the aprons present in both primary and scattered beams. The selected tube voltages were between 60 and 113 kVp with constant mAs, a fixed field size, and fixed source-to-object distance.

RESULTS

No significant difference in absorption ability of the two lead-free aprons compared with that of the lead apron was observed when the dose was measured in the primary beam. When measurements were performed in the scatter radiation field, the absorption ability of the OpaqFu apron was 1.3 times higher than that of NoLead apron and nearly equal to the absorption ability of the lead apron. An increase in the difference between the OpaqFu and NoLead aprons was observed for the tube energies higher than 100 kVp in favour of OpaqFu apron.

CONCLUSION

It is safe to use the lead-free aprons that were tested in this study in a clinical environment for the tube energy range of 60 kVp-113 kVp.

Impact of using scatter-mimicking beams instead of standard beams to measure penetration when assessing the protective value of radiation-protective garments

PURPOSE

Use standardized methods to determine how assessment of protective value of radiation-protective garments changes under conditions employing standard beam qualities, scatter-mimicking primary beams, and a modified H_p (10) measurement.

METHODS

The shielding properties of radiation-protective garments depend on the spectrum of beam energies striking the garment and the attenuation properties of materials used to construct the garment, including x-ray fluorescence produced by these materials. In this study the primary beam spectra employed during clinical interventional radiology and cardiology procedures (clinical primary beams, CPB) were identified using radiation dose structured reports (RDSR) and fluoroscope log data. Monte Carlo simulation was used to determine the scattered radiation spectra produced by these CPB during typical clinical application. For these scattered spectra, scatter-mimicking primary beams (SMPB) were determined using numerical optimization-based spectral reconstruction that adjusted kV and filtration to produce the SMPB that optimally matched the scattered spectrum for each CPB. The penetration of a subset of SMPB through four radiation-protective garments of varying compositions and nominal thicknesses was measured using a geometry specified by the International Electrotechnical Commission (IEC). The diagnostic radiological index of protection (DRIP), which increases with increasing penetration through a garment, was calculated using these measurements. Penetration through the same garments was measured for standard beams specified by the American Society of Testing and Materials (ASTM). Finally, 10 mm of PMMA was affixed to the inside of each garment and the DRIP remeasured in this configuration to simulate H_p (10).

RESULTS

The SMPB based on actual CPB were in general characterized by lower kV (range 60-76) and higher half-value layer (HVL, range 3.44-4.89 mm Al) than standard beam qualities specified by ASTM (kV range 70-85; HVL range 3.4-4.0 mm Al). A lead garment of nominal thickness 0.5 mm (D) had a DRIP of 0.8%, two lead-free garments of 0.5 mm nominal thickness had DRIPs of 1.2% (A) and 2.2% (B), and a lead-free bilayer (C) had a DRIP of 1.4%. When standard beam qualities specified by the ASTM were used, the DRIP for D was 2.2%, 175% higher than the DRIP measured using SMPB, and for A, B, and C was 2.8%, 3.2%, and 2.9%, respectively. This was 133%, 45%, and 107% higher than the DRIP measured using SMPB. Differences between the DRIP of lead-alternative garments and the lead garment were reduced when measured with 10 mm of PMMA. Using this method, the measured DRIPs were 2.2% (A), 3.1% (B), 2.5% (C), and 2.3% (D).

CONCLUSIONS

Penetration of radiation through radiation-protective garments depended strongly on the methods and X-ray spectra used for evaluation. The DRIP was higher (i.e., protective value was lower) for lead-alternative garments than for lead garments in this evaluation. The DRIP was lower for all garments when SMPB based on actual clinical beam quality data were used to measure penetration compared to ASTM standard beams. Differences in penetration between lead-alternative and lead garments were less when the DRIP was measured with 10 mm of PMMA between the garment and the chamber.

Should We Keep the Lead in the Aprons?

Medical staff should not be exposed to the primary X-ray beam during fluoroscopy-guided interventional procedures (FGIP). The main source of staff exposure is scatter radiation from the patient, which can be significant. Although many aspects of X-ray exposure to the patient as well as occupational exposure to interventional radiologists and other staff are strongly regulated and monitored in most countries, it is surprising how loosely the labeling and testing of the protective aprons is regulated. Interventional radiologists (IRs) have to be experts in interventional radiology as well as in basic facts regarding ways to provide a satisfactory level of protection from occupational exposure. IRs, however, are not familiar with the apron testing methods. The accompanying documents provided with aprons by manufacturers may not be informative enough. Vendors often report apron effectiveness at a single beam quality and attenuation. The vendor reports repeatedly disagree with independent reports, which clearly show that the attenuation of these garments at other important unreported energies may be lower than expected. Better trust no one and check your protective garment yourself, or, better yet, consult a medical physicist when making purchasing decisions related to protective garments. Each interventionist should choose garments that are appropriately protective for that individual's practice. Review of past personal dosimetry results and consultation with a medical physicist can help the IR make the best decision. This article will help the reader to understand why all protective garments are not created equally, and provides some practical tools that will allow safe and healthy practice in FGIP.

LEAD COMPOSITE VS. NONLEAD PROTECTIVE GARMENTS: WHICH ARE BETTER? A MULTIVENDOR COMPARISON

This study aims to provide more insight in attenuation characteristics and corresponding lead (Pb) equivalences of a broad range of commercially available lead composite and nonlead protective garments. Thirty garments of five manufacturers (listed as 0.25-0.35-0.50 mm Pb equivalent) were tested. Transmission values were determined at 70, 90 and 110 kVp using an inverse broad beam geometry. Pb equivalence was determined using lead sheets as reference material. A substantial variability in photon transmission across garments was found. Differences between lead composite and nonlead garments were not statistically significant. Depending on tube voltage, between 9 and 12 out of 30 garments had a lower Pb equivalence than the indicated value. This work shows that lead equivalence as indicated on a garment's label may overestimate its protective performance. Depending on the application a more thorough verification of the effectiveness of protective garments at the desired kVp is warranted.

Estimation of the shielding ability of a tungsten functional paper for diagnostic x-rays and gamma rays

Tungsten functional paper (TFP) is a novel paper‐based radiation‐shielding material. We measured the shielding ability of TFP against x‐rays and gamma rays. The TFP was supplied in 0.3‐mm‐thick sheets that contained 80% tungsten powder and 20% cellulose (C₆H₁₀O₅) by mass. In dose measurements for x‐rays (60, 80, 100, and 120 kVp), we measured doses after through 1, 2, 3, 5, 10, and 12 TFP sheets, as well as 0.3 and 0.5 mm of lead. In lead equivalence measurements, we measured doses after through 2 and 10 TFP sheets for x‐rays (100 and 150 kVp), and 0, 7, 10, 20, and 30 TFP sheets for gamma rays from cesium‐137 source (662 keV). And then, the lead equivalent thicknesses of TFP were determined by comparison with doses after through standard lead plates (purity >99.9%). Additionally, we evaluated uniformity of the transmitted dose by TFP with a computed radiography image plate for 50 kVp x‐rays. A single TFP sheet was found to have a shielding ability of 65%, 53%, 48%, and 46% for x‐rays (60, 80, 100, and 120 kVp), respectively. The lead equivalent thicknesses of two TFP sheets were 0.10 ± 0.02, 0.09 ± 0.02 mmPb, and of ten TFP sheets were 0.48 ± 0.02 and 0.51 ± 0.02 mmPb for 100 and 150 kVp x‐rays, respectively. The lead equivalent thicknesses of 7, 10, 20, and 30 sheets of TFP for gamma rays from cesium‐137 source were estimated as 0.28, 0.43, 0.91, and 1.50 mmPb with an error of ± 0.01 mm. One TFP sheet had nonuniformity, however, seven TFP sheets provided complete shielding for 50 kVp x‐rays. TFP has adequate radiation shielding ability for x‐rays and gamma rays within the energy range used in diagnostic imaging field.

A novel radiation protection device based on tungsten functional paper for application in interventional radiology

Tungsten functional paper (TFP), which contains 80% tungsten by weight, has radiation‐shielding properties. We investigated the use of TFP for the protection of operators during interventional or therapeutic angiography. The air kerma rate of scattered radiation from a simulated patient was measured, with and without TFP, using a water‐equivalent phantom and fixed C‐arm fluoroscopy. Measurements were taken at the level of the operator's eye, chest, waist, and knee, with a variable number of TFP sheets used for shielding. A Monte Carlo simulation was also utilized to analyze the dose rate delivered with and without the TFP shielding. In cine mode, when the number of TFP sheets was varied through 1, 2, 3, 5, and 10, the respective reduction in the air kerma rate relative to no TFP shielding was as follows: at eye level, 24.9%, 29.9%, 41.6%, 50.4%, and 56.2%; at chest level, 25.3%, 33.1%, 34.9%, 46.1%, and 44.3%; at waist level, 45.1%, 57.0%, 64.4%, 70.7%, and 75.2%; and at knee level, 2.1%, 2.2%, 2.1%, 2.1%, and 2.1%. In fluoroscopy mode, the respective reduction in the air kerma rate relative to no TFP shielding was as follows: at eye level, 24.8%, 30.3%, 34.8%, 51.1%, and 58.5%; at chest level, 25.8%, 33.4%, 35.5%, 45.2%, and 44.4%; at waist level, 44.6%, 56.8%, 64.7%, 71.7%, and 77.2%; and at knee level, 2.2%, 0.0%, 2.2%, 2.8%, and 2.5%. The TFP paper exhibited good radiation‐shielding properties against the scattered radiation encountered in clinical settings, and was shown to have potential application in decreasing the radiation exposure to the operator during interventional radiology.

THE ABSORPTION PROPERTIES OF LEAD-FREE GARMENTS FOR USE IN RADIATION PROTECTION

In this study, the absorption capability and the weight of various radiation-shielding materials were evaluated, for applications as alternatives to lead garments. Toxicity, atomic number, density, K-edge absorption energy and availability of elements that can serve as an alternative to lead, including tin, antimony, bismuth and tungsten, were considered. The attenuation coefficients of these elements were determined using the XCOM software package, and these metals were mixed with polymers at 50, 70, 80 and 85 % mass ratios. It can be concluded that all of the new shielding materials used in the study can be used for a diagnostic range of X-rays. However, they were compared with the commercial lead garments in terms of weight and attenuation coefficient; the 85 % samples were lighter than a 0.5-mm lead garment and provided superior radiation protection, which demonstrates its potential for commercial applications.

Evaluation of the scattered radiations of lead and lead-free aprons in diagnostic radiology by MCNPX

BACKGROUND

Over the past few years, because of high attenuation and lightweight, non-toxic, lead-free aprons (LFAs) have been replaced by lead aprons (LAs). Lots of studies declared that this fact was based on the interactions of diagnostic X-ray with material such as the photoelectric effect (PE) and Compton scattering. These studies have demonstrated that in these types of aprons, due to the presence of different K-edge absorption, PE has a wide absorption in various metals with divers K-edges. The measurement geometry in most of these studies was narrow beam geometry, i.e. a collimated source and a collimated detector with a large source-detector distance.

OBJECTIVE

The present study intended to evaluate the attenuation of radiology scattered radiations in LAs and LFAs in both narrow and broad beam geometries, which is a more realistic situation, in order to check whether or not the higher attenuation is valid.

METHODS

In this study, a lead apron contains (Pb + EPV) and two non-lead compounds of (W + Sn + EPVC) with different weight percent (Wt%) were evaluated in the energy range of diagnostic radiology (100 kVp). The MCNPX code was applied to simulate broad - and narrow-beam measurement geometries. The evaluations have been performed in three situations: 1st) the same density thickness of LA and LFAs 2nd) same line thickness of LA and LFAs 3rd) considering the thickness of LFAs which has the same attenuation with LAs i.e. lead equivalent thickness for LFAs in the narrow beam. Finally, the x-ray transmission ratio (I/I_0) of LAs and LFAs was compared in 100 kVp for three mentioned conditions.

RESULTS

Our results indicated that LFAs had more radiation attenuation rather than LA in the 1st and 2nd conditions with both geometries. However, LFAs had lower attenuation in comparison to LAs in the 3rd condition with broad beam geometry. More importantly, the transmission ratio (I/I_0) of LFAs in the broad beam condition was more significant than LA.

CONCLUSION

The scattered radiations produced by LFAs are more than LAs because of the production of characteristic radiations resulted from K-edge absorption in composited aprons. Consequently, the LFAs should be evaluated in both narrow and broad beam situation using the lead equivalent thickness of LFAs to make sure that the non-lead aprons do not increase the radiation dose of the user.

Sensitivity of the diagnostic radiological index of protection to procedural factors in fluoroscopy

PURPOSE

To evaluate the sensitivity of the diagnostic radiological index of protection (DRIP), used to quantify the protective value of radioprotective garments, to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams to be used in measuring the DRIP.

METHODS

Monte Carlo simulations were performed to determine the shape of the scattered x-ray spectra incident on the operator in different clinical fluoroscopy scenarios, including interventional radiology and interventional cardiology (IC). Two clinical simulations studied the sensitivity of the scattered spectrum to gantry angle and patient size, while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial simulations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size, and beam quality for constant technical factors. Average energy (Eavg) was the figure of merit used to condense fluence in each energy bin to a single numerical index.

RESULTS

Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affect the scattered spectrum indirectly through their effect on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in IC, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type.

CONCLUSIONS

The scattered spectrum striking the operator in fluoroscopy is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle.

Liquid Metal Based Stretchable Radiation-Shielding Film

We reported a stretchable and flexible radiation-shielding film based on room-temperature liquid metal. Conceptual experiments showed that the liquid metal based printing technology can achieve an ultrathin flexible radiation-shielding film with a thickness of 0.3 mm. Moreover, the yield strength and ultimate strength of the liquid metal film appear much better than those of a conventional lead-particle-containing radiation-shielding material. In order to evaluate the radiation-shielding performance of the liquid metal material, X-ray radiation experiments to compare the liquid metal film and conventional lead-particle-based shielding material under different stretching conditions were performed. The results indicate that the liquid metal shielding film could achieve a certain radiation-shielding performance. Furthermore, because of the screen-printing properties of liquid metal, a low-cost X-ray mask method using a liquid metal selective radiation-shielding film was also studied, which could serve as a highly efficient and practical method for the medical X-ray shielding applications or semiconductor lithography industry.

Application of a semi-empirical model for the evaluation of transmission properties of barite mortar

The aim of this study was to estimate barite mortar attenuation curves using X-ray spectra weighted by a workload distribution. A semi-empirical model was used for the evaluation of transmission properties of this material. Since ambient dose equivalent, H(⁎)(10), is the radiation quantity adopted by IAEA for dose assessment, the variation of the H(⁎)(10) as a function of barite mortar thickness was calculated using primary experimental spectra. A CdTe detector was used for the measurement of these spectra. The resulting spectra were adopted for estimating the optimized thickness of protective barrier needed for shielding an area in an X-ray imaging facility.

On the (f)utility of measuring the lead equivalence of protective garments

PURPOSE

Protective garments incorporating lead (Pb) or other moderate to high atomic number elements are a necessary radiation protection tool. However, as lead has been replaced by other elements, verifying manufacturers' claims regarding the lead equivalence of such garments has become nearly impossible, and current standards only require measurement of attenuation or lead equivalence at a single beam quality. A garment may provide a high degree of protection at the specified beam quality, but underperform at others. The authors sought to measure the lead equivalence of several protective garments and propose a better method for quantifying the protective value of garments.

METHODS

The authors measured the penetration of primary and scattered radiation through lead sheets and three protective garments of nominal 0.5 mm Pb equivalence, one lead and two lead-free. Penetration was measured using beams of nominal 60, 80, 100, and 120 kVp. Primary penetration through protective garments at 70 kVp was also measured. A lead-lined enclosure was constructed for measuring scatter penetration, as instruments must be protected from stray radiation when measuring low-level penetration of scattered radiation. Using polynomial least-squares fits to the measured data of penetration through lead sheets, the authors determined the lead equivalence of the protective garments across a range of beam qualities.

RESULTS

The lead garment was 0.5 mm Pb equivalent across all beam qualities evaluated. While the maximum lead equivalence of the lead-free garments did occur at the manufacturer-specified beam quality, neither garment was 0.5 mm Pb equivalent at the specified beam quality. The lead equivalence of the lead-free garments was a strong function of beam quality and nature of the radiation, i.e., primary or scattered. The lead equivalence of the lead-free garments in primary beams ranged from 0.40 to 0.47 mm Pb equivalent and in scattered beams ranged from 0.37 to 0.46 mm Pb equivalent. The penetration through one lead-free garment at 60 kVp was 478% higher than the penetration through the lead garment. The authors have also provided linear fits of radiation penetration through lead as a function of half-value layer. It is likely that assessment of protective value can be performed using primary beams matched to the spectra of scattered beams. The authors propose the diagnostic radiation index of protection (DRIP), a weighted sum of the percentage of radiation penetration across a range of beam qualities, as a more robust method for specifying the protective value of garments.

CONCLUSIONS

The protective value of garments from both primary and scattered radiation is a strong function of beam quality. Assessment of the protective value should be performed across a range of beam qualities. Methods for performing such assessment must be developed and must specify beam qualities, measurement geometry, and the appropriate weighting across the beam quality range for different applications.

Polymer-composite materials for radiation protection

Unwanted exposures to high-energy or ionizing radiation can be hazardous to health. Prolonged or accumulated radiation dosage from either particle-emissions such as alpha/beta, proton, electron, neutron emissions, or high-energy electromagnetic waves such as X-rays/γ rays, may result in carcinogenesis, cell mutations, organ failure, etc. To avoid occupational hazards from these kinds of exposures, researchers have traditionally used heavy metals or their composites to attenuate the radiation. However, protective gear made of heavy metals are not only cumbersome but also are capable of producing more penetrative secondary radiations which requires additional shielding, increasing the cost and the weight factor. Consequently, significant research efforts have been focused toward designing efficient, lightweight, cost-effective, and flexible shielding materials for protection against radiation encountered in various industries (aerospace, hospitals, and nuclear reactors). In this regard, polymer composites have become attractive candidates for developing materials that can be designed to effectively attenuate photon or particle radiation. In this paper, we review the state-of-the-art of polymer composites reinforced with micro/nanomaterials, for their use as radiation shields.