Specific Absorption Rate Evaluation Research Articles

Crescent Antennas as Sensors: Case of Sensing Brain Pathology.

Microstrip crescent antennas offer compactness, conformability, low profile, high sensitivity, multi-band operability, cost-effectiveness and ease of fabrication in contrast to bulky, rigid horn, helical and Vivaldi antennas. This work presents crescent sensors for monitoring brain pathology associated with stroke and atrophy. Single- and multi-element crescent sensors are designed and validated by software simulations. The fabricated sensors are integrated with glasses and experimentally evaluated using a realistic brain phantom. The performance of the sensors is compared in terms of peak gain, directivity, radiation performance, flexibility and detection capability. The crescent sensors can detect the pathologies through the monitoring of backscattered electromagnetic signals that are triggered by dielectric variations in the affected tissues. The proposed sensors can effectively detect stroke and brain atrophy targets with a volume of 25 mm3 and 56 mm3, respectively. The safety of the sensors is examined through the evaluation of Specific Absorption Rate (peak SAR < 1.25 W/Kg, 100 mW), temperature increase within brain tissues (max: 0.155 °C, min: 0.115 °C) and electric field analysis. The results suggest that the crescent sensors can provide a flexible, portable and non-invasive solution to monitor degenerative brain pathology.

Wearable Antennas for Sensor Networks and IoT Applications: Evaluation of SAR and Biological Effects.

In recent years, there has been a rapid development in the wearable industry. The growing number of wearables has led to the demand for new lightweight, flexible wearable antennas. In order to be applicable in IoT wearable devices, the antennas must meet certain electrical, mechanical, manufacturing, and safety requirements (e.g., specific absorption rate (SAR) below worldwide limits). However, the assessment of SAR does not provide information on the mechanisms of interaction between low-intensity electromagnetic fields emitted by wearable antennas and the human body. In this paper, we presented a detailed investigation of the SAR induced in erythrocyte suspensions from a fully textile wearable antenna at realistic (net input power 6.3 mW) and conservative (net input power 450 mW) conditions at 2.41 GHz, as well as results from in vitro experiments on the stability of human erythrocyte membranes at both exposure conditions. The detailed investigation showed that the 1 g average SARs were 0.5758 W/kg and 41.13 W/kg, respectively. Results from the in vitro experiments demonstrated that the short-term (20 min) irradiation of erythrocyte membranes in the reactive near-field of the wearable antenna at 6.3 mW input power had a stabilizing effect. Long-term exposure (120 min) had a destabilizing effect on the erythrocyte membrane.

Evaluation of specific absorption rate and heating in children exposed to a 7T MRI head coil

Magnetic Resonance in MedicineVolume 88, Issue 3 p. C1-C1 COVER IMAGEFree Access Evaluation of specific absorption rate and heating in children exposed to a 7T MRI head coil First published: 28 June 2022 https://doi.org/10.1002/mrm.29388AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume88, Issue3September 2022Pages C1-C1 RelatedInformation

Evaluation of specific absorption rate and heating in children exposed to a 7T MRI head coil.

PurposeTo evaluate specific absorption rate (SAR) and temperature distributions resulting from pediatric exposure to a 7T head coil.MethodsExposure from a 297‐MHz birdcage head transmit coil (CP mode single‐channel transmission) was simulated in several child models (ages 3–14, mass 13.9–50.4 kg) and one adult, using time‐domain electromagnetic and thermal solvers. Position variability, age‐related changes in dielectric properties, and differences in thermoregulation were also considered.ResultsAge‐adjusted dielectric properties had little effect in this population. Head average SAR (hdSAR) was the limiting factor for all models centered in the coil. The value of hdSAR (normalized to net power) was found to decrease linearly with increasing mass (R2 = 0.86); no equivalent relationship for peak‐spatial 10g averaged SAR (psSAR10g) was identified. Relatively small (< 10%) variability was observed in hdSAR for position shifts of ±25 mm in each orthogonal direction when normalized to net power; accounting for B1+ efficiency can lead to much larger variability. Position sensitivity of psSAR10g was greater, but in most cases hdSAR remained the limiting quantity.For thermal simulations, if blood temperature is fixed (i.e., asserting good thermoregulation), maximum temperatures are compliant with International Electrotechnical Commission limits during 60‐min exposure at the SAR limit. Introducing variable blood temperature leads to core temperature changes proportional to whole‐body averaged SAR, exceeding guideline limits for all child models.ConclusionsChildren experienced higher SAR than adults for the 297‐MHz head transmit coil examined in this work. Thermal simulations suggest that core temperature changes could occur in smaller subjects, although experimental data are needed for validation.

Specific absorption rate assessment of fifth generation mobile phones with specific anthropomorphic mannequin model and high‐resolution anatomical head model

With the spread and application of the fifth generation (5G) of mobile communication technology, the number of 5G mobile phone users increase rapidly. The traditional safety standard of electromagnetic radiation of mobile phones was set two decades ago, in which a homogeneous specific anthropomorphic mannequin (SAM) head model with standardized size and shape is utilized for specific absorption rate (SAR) evaluation. The SAM model has been proved conservative for SAR evaluation of 2G, 3G and 4G mobile phone antennas. However, it needs to be validated whether it is still suitable for SAR evaluation of 5G mobile phone antennas. A high-resolution anatomical head model with tissues including muscle, skull, cerebrospinal fluid and brain is developed in this paper. The SAR values of three different generation mobile phone antennas are simulated by utilizing both the SAM model and the high-resolution anatomical head model to assess their applicability. Numerical simulations show that the anatomical model may produce a higher SAR value than the SAM model for a 5G mobile phone antenna. So new head model may need to be developed for the SAR evaluation of 5G mobile phone antennas.

Average SAR prediction, validation, and evaluation for a compact MR scanner head-sized RF coil

A recently developed compact 3 T (C3T) MRI scanner with high performance gradients [1, 2] has a dedicated radiofrequency (RF) transmit coil that exposes only the head, neck and a small portion of the upper body region during head-first scanning. Due to the unique coil geometry and patient positioning, the established SAR model used for a conventional whole-body scanner cannot be directly translated to the C3T. Here a specific absorption rate (SAR) estimation and validation framework was developed and used to implement a dedicated and accurate SAR prediction model for the C3T. Two different SAR prediction models for the C3T were defined and evaluated: one based on an anatomically derived exposed mass, and one using a fixed anatomical position located caudally to the RF coil to determine the exposed mass. After coil modeling and virtual human body simulation, the designed SAR prediction model was implemented on the C3T and verified with calorimetry and in vivo scan power monitoring. The fixed-demarcation exposed mass model was selected as appropriate exposed mass region to accurately estimate the SAR deposition in the patient on the C3T.

Biostimulation Effects and Temperature Variation in Stimulated Dielectric Substance (Diabetic Blood Comparable to Non-Diabetic Blood) Based on the Specific Absorption Rate (SAR) in Laser Therapy

Human blood exposed to irradiation absorbs electromagnetic energy which consequently effect temperature variation. The evaluation of Specific Absorption Rate (SAR) of human blood helps to ascertain the values for optimum laser power, time, and temperature variation for fair therapy to avoid blood-irradiation pollution but to enhance its rheological properties when using lasers. Prior knowledge of blood SAR evaluating its dielectric properties is significant, but this is under investigation. We investigate the appropriate SAR threshold value as affected by temperature variation using fundamental blood dielectric parameters to optimize the effect of low-level laser therapy based on physiological and morphological changes of the stimulated diabetic blood. Studies were carried out with Agilent 4294A impedance analyser at frequencies (40Hz – 30 MHz) and designed cells (cuvettes) comprises of electrodes were used in the pre- and post-irradiations measurements. At different laser power outputs, blood samples were subjected to various irradiation durations using portable laser diode-pumped solid state of wavelength 532 nm. Results showed laser at low energy is capable of moderating morphologically the proportion of abnormal diabetic red blood cells. Hence, there is a significant effect using a laser at low energy, as non-medicinal therapy in controlling diabetic health conditions. The positive biostimulation effects on the irradiated diabetic blood occurred within absorbance threshold SAR values range of 0.140?0.695 W/kg and average temperatures range of 24.2?28.0 0C before blood saturation absorbance peak. There is morphological stimulation at a laser power of 50 mW for an exposure time of 10–15 minutes and 60 mW for 5–10 minutes of laser therapy that demonstrates better blood rejuvenated conditions. This occurred within the threshold SAR of 0.140?0.695 W/kg and average temperatures range of 24.2?28.0 0C. Therefore, the diabetic blood irradiated using laser output powers of 70 and 80 mW during exposure durations of 5,10, 15 and 20 minutes rather bio-inhibits positive blood stimulation which has resulted to crenation due to excessive irradiation.

Design and Analysis of Rectangular Slot Microstrip Patch Antenna for Millimetrewave Communication and its SAR Evaluation

This paper presents the design and analysis of the compact patch antenna for 5G and future generation millimetre-wave communication system. The proposed design consists of FR4 substrate length, width, and height of 21.37 x 5 x 1.59 mm3 , besides two rectangular slots incorporated with a dimension of 0.2 x 2.6 mm2 within the patch of 4.22 x 3.46 mm2 , to enhance the resonance frequency more accurate and one more square slot incorporated in to feed line with the dimension of 0.2 x 0.5 mm2 . The obtained return losses of the design is-21.25dB with gain and voltage standing wave ratio (VSWR) of 3.90dBi,1.18 by using a lumped port configuration. For the specific absorption rate (SAR) evaluation considered as a human head model in high-frequency structure simulator (HFSS) software, the obtained values are within the standard limit, the design covers the frequency range of 28GHz, this design may capable of 5G and next-generation wireless communication system application.

Measurement and evaluation of specific absorption rate and temperature elevation caused by an artificial hip joint during MRI scanning

A primary safety concern in a magnetic resonance imaging environment is heating of metallic implants by absorbing radiofrequency (RF) energy during MRI scanning. Experimental measurement in conjunction with computational modeling was used to evaluate the risk of biological tissue injury from the RF heating of artificial hip joints by obtaining both specific absorption rate (SAR) and temperature elevation at 1.5 T and 3 T MRI systems. Simulation result showed that high SAR and high temperature appeared near both head and tail sections of the artificial hip joints. For five different 1.5 T and 3 T MRI systems, measured temperature location showed that high temperature rises occurred near both head and tail regions of the metallic hip joints. Measured SAR value of 24.6 W/kg and the high temperature rise (= 4.22 °C) occurred in the tail region of the hip joint at 1.5 T, which was higher than the limits for temperature required by the international electrotechnical commission 60601-2-33. We have demonstrated the feasibility of evaluating RF heating of metallic hip joints during MRI scans.

Investigation on The Specific Absorption Rate (sar) in A 3d Human Head Model Exposed to Electromagnetic Radiations

Exposure human tissue to electromagnetic radiation (EM) from radio wireless frequencies causes many negative health effects. The assessment of the absorbed EM by human tissue depends on the Specific Absorption Rate (SAR) factor. In this paper, a square patch antenna (SPA) is designed to be a source of EM radiation, and optimized to operate at several applicable frequencies, such as GSM 1800, IEEE 802.11 WLAN standard 2.4 GHz and 5.3 GHz bands, and 3.2 GHz WiMAX band. The radiated EM by the SPA antenna is evaluated in a 3D human head model or Specific Anthropomorphic Model (SAM), which consists of two layers, the outer shell (1.5 mm thickness) and filled with tissue simulating liquid (TSL). The investigation involved four aspects, first the distance between the SAM and the EM source has been moved between 0 mm to 50 mm, second for the specific distances (0 mm, 15 mm, 30 mm, and 45 mm) the frequency of EM source has been changed among 1.8 GHz, 2.4 GHz, 3.2 GHz, and 5.3 GHz. Third, the tilt angle (θ) between the SAM and the antenna has been shifted from 00to 900. Finally, the antenna encasement (2 mm thickness plastic material) was removed and the procedure in the first step is repeated to investigate the effect of encasement on the SAR reducing. The results reveal that there is an inversely proportional relation between SAR and distance, SAR and tilt angle. Besides, the antenna encasement has a large impact on attenuating SAR value, while the SAR is directly proportional to frequency. All SAR evaluations were performed by CST-2014 Microwave studio simulator which is built on the Finite-Difference-Time-Domain (FDTD) principle. All calculations are achieved over 1 g and 10 g of mass tissue averaging and according to IEEE/IEC 62704-1 standards.

Novel Low-Cost Integrated Multiband Antenna Design Customized for Smartwatch Applications with SAR Evaluation

This paper presents a novel low-cost integrated multiband antenna design customized for smartwatch applications and wearable devices. The design consists in using a broadband planar patch antenna with circular microstrip lines and a miniaturized feeding-point with a structure of 30 × 30 × 1.6 mm3, and it is easy to deploy inside the smartwatch and cost-effective for the wearable device industry. The parametric study and final dimensions of the design and the measured results of the reflection and radiation pattern are discussed. The antenna with maximum gain up to 6.6 dBi and S11 up to −22 dB exhibits excellent performance for all the frequencies required in wearable systems such as 1.9 GHz, 2.3 GHz, 2.4 GHz, 2.6 GHz, 5.2 GHz, and 5.8 GHz. We drew a comparison between similar research and this work in terms of antenna performance. Furthermore, we investigate the specific absorption rate (SAR) performance of the antenna for the smartwatch application, using both human hand wrist multilayer and SAM head mouth models. The SAR results in different positions for all the frequencies are compared to the Federal Communication Commission (FCC) standards.

Evaluation of SAR and Temperature Rise in Human Hand Due to Contact Current From 100 kHz to 100 MHz

International guidelines/standards for the protection of humans from radiofrequency exposure have set a limit by assuming the lowest threshold for a classical heating effect, among other effects. However, no computational study has been reported that evaluates temperature rise due to contact currents. This paper presents the computational dosimetry of a specific absorption rate (SAR) and temperature rise due to touch contact currents in the frequency range 100 kHz to 100 MHz using a detailed numerical model of a human hand. Tissue dielectric properties obtained from a conventional 4-Cole-Cole dispersion model have often been considered in dosimetry studies. However, a comparison of the computed electrical impedance with experimental results suggests that the conductivity of the subcutaneous fat in the finger should be higher than the 4-Cole-Cole values-potentially attributable to collagen fibers. We then proposed a set of tissue dielectric conductivities estimated from recent measurement results of conductivities for the epidermis, dermis, and subcutaneous tissue. Consequently, the computed electrical impedances exhibited good agreement with the measured ones. In addition, the SAR and temperature rise obtained using the proposed tissue conductivities were lower than those obtained using 4-Cole-Cole values. Therefore, the SAR and temperature rise obtained based on the 4-Cole-Cole dispersion model may be overstated. We also observed that the steady-state maximum temperature rise due to the contact current at the guidance/limit level was equivalent to 2.5 °C, which is the maximum permissible temperature rise (5 °C) divided by a reduction factor of 2.

Reduction of multiple‐input multiple‐output specific absorption rate synthesized using a fast estimation model

A technique that improves multiple-input multiple-output (MIMO) specific absorption rate (SAR) is proposed for multiple-antenna transmitters. When multiple antennas are implemented, the SAR evaluation is more complex than the stand-alone counterpart. Techniques for the reduction of stand-alone SAR cannot be applied to the MIMO scenario straightforwardly. To reduce MIMO SAR and preserve radiation characteristics simultaneously, a technique based on solving the fast estimation model of MIMO SAR is proposed. The proposed technique is cast into two phases. In the phase one, the fast estimation model is constructed for MIMO SAR. This model can predict arbitrary combinations of MIMO SAR once the contribution of the electric field of each antenna is obtained. The capability of the prediction is validated through 19 scenarios. In the phase two, the fast estimation model is formulated as a mathematical programming problem, where the current amplitude of each antenna is treated as decision variables. The combination of the decision variables that leads to the lowest SAR is thus the optimum solution. The proposed technique is tested using a quad-element antenna system that operates in 3.4 to 3.7 GHz. The results indicate that most of the scenarios depict reduced SAR. The averaging MIMO SAR is improved by 13.75%.

Analysis and Evaluation of Specific Absorption Rate of GSM Signal in Port Harcourt, Nigeria

There is a growing concern in the world that residents close to GSM base station facilities are exposed to electromagnetic radiation which causes different health illness like cancer, leukemia, memory lost, dizziness, fatigue, etc. This study puts to rest the position on the effect of radiofrequency (RF) radiation from GSM masts on human health. In this research work, the evaluation and assessment of radio frequency radiation in five selected mobile base stations facilities in Obio/Akpor Local Government of Rivers State, Nigeria were carried out using an EMF meter for measurement of Electric field. The measurements of the radio frequency radiation with the EMF meter was conducted from 0 – 300m away from the selected base transceivers stations facilities of the selected telecommunication operators (MTN, Globacom and Airtel) in Nigeria. The data obtained from the research were analyzed using Specific Absorption Rate formula to establish whether with time exposure to RF radiation will have negative impact on human health. The normal specific absorption rate (SAR) and the Power Density for the general public whole body was assessed from the measured electric field strength and the results were compared with that of International Commission on Non Ionization Radiation Protection (ICNIRP).The results showed that the average amount of SAR for the selected five base transceiver station (BTS) facilities were within the range of 0.0037 W/kg – 0.0084 W/kg and the power density 1.5183 W/m2 – 9.5083 W/m2. These values are lower than the recommended limit by ICNIRP which is 0.08w/kg for the human body. This study has shown that there is inconsequential effect on human health because the non-ionizing electromagnetic energy has no sufficient energy to affect any part of human body for the residents living close to the selected BTS facilities of the various telecommunication providers.

Evaluation of Specific Absorption Rate in Three-Layered Tissue Model at 13.56 MHz and 40.68 MHz for Inductively Powered Biomedical Implants

This paper presents an optimized 3-coil inductive wireless power transfer (WPT) system at 13.56 MHz and 40.68 MHz to show and compare the specific absorption rate (SAR) effects on human tissue. This work also substantiates the effects of perfect alignment, lateral and/or angular misalignments on the power transfer efficiency (PTE) of the proposed WPT system. Additionally, the impacts of different tissue composition, input power and coil shape on the SAR are analyzed. The distance between the external and implantable coils is 10 mm. The results have been verified through simulations and measurements. The simulated results show that the SAR of the system at 40.68 MHz had crossed the limit designated by the Federal Communications Commission and hence, it is unsafe and causes tissue damage. Measurement results of the system in air medium show that the optimized printed circuit board coils at 13.56 MHz achieved a PTE of 41.7% whereas PTE waned to 18.2% and 15.4% at 10 mm of lateral misalignment and 60° of angular misalignment respectively. The PTE of a combination of 10 mm lateral misalignment and 60° angular misalignment is 21%. To analyze in a real-environment, a boneless pork sample with 10 mm of thickness is placed as a medium between the external and implantable coils. At perfect alignment, the PTE through pork sample is 30.8%. A RF power generator operating at 13.56 MHz provides 1 W input power to the external coil and the power delivered to load through the air and tissue mediums are 347 mW and 266 mW respectively.

Polarization Reconfigurable Planar Inverted-F Antenna for Implantable Telemetry Applications

A polarization reconfigurable implantable planar inverted-F antenna (PIFA), operating at 2.45–GHz ISM band, is introduced for monitoring and biotelemetry purposes. The proposed implantable antenna featuring with the reconfigurability of two polarizations is effective to overcome the polarization mismatch and multi-path reflection in an indoor environment. By using two groups of PIN diodes as radio frequency (RF) switches along <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> -direction and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -direction respectively, two orthogonal linear polarizations can be switched to avoid communication link failure. The proposed antenna is based on a planar inverted-F antenna structure and the implantable environment of human body to develop. The antenna exhibits a good stability of an impedance bandwidth with the reflection coefficient ≤−10 dB in the environment of a human phantom. The simulated results in simple muscle-layer phantom, multi-layer phantom and 3D realistic human voxel model demonstrates the good robustness of the proposed antenna in the complex implantable environment. An in-vitro test was carried out in body tissue simulant liquid to validate our proposed design. A sleeve balun was fabricated and incorporated into the semirigid coax cable in order to eliminate the unwanted effect of the long cable during the measurement. The experimental results agree with simulation and show an overlapped impedance bandwidth of 9.1% from 2.3 GHz to 2.52 GHz in different reconfigurable states. The radiation performances, evaluation of Specific Absorption Rate (SAR), and link characteristics in different propagation scenarios are also discussed. This proposed antenna technology is suitable for implantable telemetry applications.

Research on an Anthropomorphic Phantom for Evaluation of the Medical Device Electromagnetic Field Exposure SAR

A medical device will emit electromagnetic radiation to its surrounding environment either actively or passively. However, clinicians are unaware as to whether the ambient electromagnetic radiation will exceed the human body’s endurance capacity. In this paper, the mathematical model of electromagnetic parameters devoted to Specific Absorption Rate (SAR) testing of medical devices was established using a Debye Model. Body liquids featuring dielectric properties including the conductivity and permittivity of tissues at various body parts were simulated on the basis of results derived from the model. A simplified anthropomorphic phantom for the SAR test was founded on the basis of geometric parameters by following the principles of resemblance and consistent conductivity. A full-band electromagnetic mathematical model of brain, muscle, heart, lungs, stomach, and kidneys was set up. Electromagnetic radiation levels of a wearable Electrocardiograph monitoring device were measured and found that the maximum electric field intensity was up to 30 V/m, and the electromagnetic radiation SAR value was 0.96 W/kg, which were equivalent to the electromagnetic radiation exposure of the occupational group. The results established that electromagnetic radiation of certain medical devices exceeded the allowed values specified by the World Health Organization (WHO). Therefore, further studies within the field of medicine are required to decide whether additional evaluation measures should be required.

SAR Evaluation of Metallic Loop-like Accessory Effect of Broadband Wearable Planar Monopole Textile Antenna

This paper presents the investigation influence of the common metallic loop like accessory on Specific Absorption Rate (SAR) averaged over 10g and 1 g tissue.The simulations were made by means CST Microwave Studio software at frequencies 2.45GHz and 2.6GHz. Numerical analysis conducted using broadband textile monopole antenna (TM) with variations of orientation and distance showed that the SAR value increased when the antenna horizontally polarized.This is up to 80% more than vertically polarized TM placed closest item to 2mm.

Rigorous Analysis and Evaluation of Specific Absorption Rate (SAR) for Mobile Multimedia Healthcare

The application of wireless body area network (WBAN) in health sector is crucial. It prolongs the life expectancy and improves the quality of life by enabling remote health monitoring. Despite many advantages, it may result and exacerbates various extant health issues especially in the context of mobile multimedia. Due to high data rate of mobile multimedia applications, heat generated from sensor devices is considerably high and results in thermal dissipation. The thermal impact of sensors on human body has largely been a neglected topic. The paper rigorously analyzes the specific absorption rate (SAR) impact on human body. Moreover, the paper largely contributes by comprehensively evaluating SAR impact under various circumstances and dependency factors. The analysis and evaluation show promising results that can significantly help the successful design and deployment of WBAN strategies. The paper also provides great guidance to numerous practitioners of this domain.

Investigation and reduction methods of specific absorption rate for biomedical applications: A survey

Specific Absorption Rate (SAR) is an inevitable parameter to be considered for various RF dosimetry evaluations in the field of biomedical engineering. There is a much concern in exposure studies as they have a significant impact on the social and health issues in the recent global community. SAR measures the absorption of electromagnetic radiation of RF from devices in an exposure area. The significance of SAR parameter has been awakened in broad areas of technology and even considered in the design of radiating structures from biomedical devices such as MRI to also popular mobile phones. Researchers have explicated the constant interaction of electromagnetic field interactions with biological systems. The advancements in technology pose a grave concern about the impact on human health. This paper intends to undertake an extensive survey of the various current investigations done with SAR in different scenarios with possible radiating structures and also focus on exposure areas on the human body. The SAR depends on estimation parameters that are analyzed and discussed. Further, the paper will analyze comparatively the facets of implied Methodologies in SAR computation. The parametric evaluation of SAR paves the way for a requirement reduction of SAR parameter. The paper discusses current reduction methodologies and its primary advantages and details possible setbacks. The analysis indicates a requirement of the specific radiation structure for a particular area of exposure of concern, followed by a need of ideal reduction methodology.