Human Equivalent Phantom Research Articles

Preclinical and Preliminary Evaluation of Perceived Image Quality of AI-Processed Low-Dose CBCT Analysis of a Single Tooth.

This study assessed AI-processed low-dose cone-beam computed tomography (CBCT) images for single-tooth diagnosis. Human-equivalent phantoms were used to evaluate CBCT image quality with a focus on the right mandibular first molar. Two CBCT machines were used for evaluation. The first CBCT machine was used for the experimental group, in which images were acquired using four protocols and enhanced with AI processing to improve quality. The other machine was used for the control group, where images were taken in one protocol without AI processing. The dose-area product (DAP) was measured for each protocol. Subjective clinical image quality was assessed twice by five dentists, with a 2-month interval in between, using 11 parameters and a six-point rating scale. Agreement and statistical significance were assessed with Fleiss' kappa coefficient and intra-class correlation coefficient. The AI-processed protocols exhibited lower DAP/field of view values than non-processed protocols, while demonstrating subjective clinical evaluation results comparable to those of non-processed protocols. The Fleiss' kappa coefficient value revealed statistical significance and substantial agreement. The intra-class correlation coefficient showed statistical significance and almost perfect agreement. These findings highlight the importance of minimizing radiation exposure while maintaining diagnostic quality as the usage of CBCT increases in single-tooth diagnosis.

Investigation of Imaging Conditions Using Human Body Equivalent Phantom and Neonatal Phantom in Portable Chest Radiography of Newborns

Investigation of imaging conditions using human body equivalent phantom and neonatal phantom in portable chest radiography of newborns. Although attempts have been made to reduce dose by image processing in portable X-ray radiography of neonates, no evaluation has been made at the raw data level of the images. In this study, we investigated dose reduction from the current imaging conditions using a simulated phantom and a neonatal phantom in terms of raw data level image quality and incident surface dose. The pixel values of each region were calculated from chest photographs of newborn infants taken at 60 kV and 2.0 mAs, and the thickness and combination of acrylic, aluminum, and copper were adjusted to create a simulated phantom with equivalent pixel values. The SdNR and incident surface dose at each site obtained from the simulated phantom were compared to obtain imaging conditions equivalent to or better than 60 kV, 2.0 mAs. The neonatal phantom was imaged, and the CNR of the processed images was compared to that of 60 kV, 2.0 mAs. SdNR and incident surface dose results showed that 62 kV, 1.8 mAs was superior. Comparison with neonatal phantoms showed no significant difference. The simulated phantom was used to reproduce the clinical situation and to obtain excellent imaging conditions.

Consideration on the Influence of the Direction Dependence of the Lens Dosimeter at the Attaching Position on the Equivalent Dose Management of the Lens

Since International Commission on Radiological Protection's 2011 statement on tissue reaction was released, our hospital recommends wearing radioprotection glasses for radiation workers. The introduction of the lens dosimeter is examined in order to grasp the equivalent dose of the lens; however, the lens dosimeter was guessed to have influence on the equivalent dose management of the lens based on the characteristics and the attaching position. In this study, the validity of the lens dosimeter was verified by examining the characteristics and simulating the attaching position. In the simulation of rotating the human equivalent phantom, the indicated value of the lens was 0.18 mGy in condition as the human equivalent phantom confronted the radiation field, and the indicated value of the lens dosimeter at the corner of the eye was 0.17 mGy. By rotation, the indicated value of the lens proximal to the radiation field became higher compared to the distal value. The values indicated at the distal corner of the eye were below the indicated value of proximal lens, except for 180° rotation. The indicated value of the lens proximal to the radiation field became higher compared to the distal value, except for 180° rotation, and the maximal difference was 2.97 times at 150 degrees to the left. These results suggest the necessity of management of the lens proximal to the radiation field and attaching the lens dosimeter to the proximal corner of eye, since overestimation ensures safety at radiation management.

Comparison of subjective image analysis and effective dose between low-dose cone-beam computed tomography machines.

To compare the cone-beam computed tomography (CBCT) image quality and effective dose between low-dose scanning and standard manufacturer-recommended protocols among different CBCT units. Three human-equivalent phantoms were scanned using the ultra-low-dose (ULD), low dose (LD), and standard dose (STD) modes of ProMax 3D Mid (Planmeca Oy, Helsinki, Finland) and Orthophos SL (Sirona, Bensheim, German) for the CBCT images. The quality of the dental anatomical images was assessed by four experienced oral and maxillofacial radiologists using a 5-point Likert scale. OnDemand3D (Cybermed Co., Seoul, Korea) was used as the third-party software for viewing. The percentage of absolute agreement was calculated to determine intra- and interrater agreements among the observers. The effective doses for all CBCT scanning protocols were also calculated. The STD protocol yielded a higher image quality than did the ULD and LD protocols in both ProMax 3D Mid and Orthophos SL. The ULD and LD protocols demonstrated an "acceptable-to-good" sense of visual perception of the CBCT images. The visibility scores significantly differed between the ULD and LD and the STD protocols in ProMax 3D Mid and Orthophos SL, except for the 120-kVp setting in ProMax 3D Mid. The average intra- and interrater agreement scores ranged from 0.63 to 0.89 and from 0.44 to 0.76, respectively. The ULD and LD protocols reduced the radiation dose sixfold compared with the STD protocol. High-tube-voltage protocols could remarkably reduce the imaging dose without degrading the image quality. Specifically, ULD and LD CBCT protocols may be adopted as routine practice for diagnosis and treatment planning.

Development of an aperture-type radiation regulator for shielding against secondary radiation from x-ray tubes and collimators in computed tomography

During computed tomography (CT) scans, radiation scatters in all directions, increasing radiation exposure. In this study, an aperture-type radiation regulator was developed to provide shielding against secondary radiation from the x-ray tube and collimator in CT. To evaluate the usefulness of the developed aperture-type radiation regulator, (1) spatial dose distribution within the CT room was measured, (2) dose intensity at 1 m from the isocenter was compared, (3) absorbed dose in the nearby organs was evaluated using a human equivalent phantom, and (4) noise, CNR, and SNR were compared for assessment of image quality. The results showed that the developed aperture-type radiation regulator reduced the intensity of secondary radiation by approximately 25% in front of the gantry and 15% to the rear of the gantry. The maximum dose distribution on 10 μGy was reduced by approximately 18% in front of the gantry and 12% in the rear. In addition, when the neck and head were scanned, the absorbed dose in the chest decreased by 25% and 40%, respectively, and noise was reduced by 3.3%–4.5% for different phantoms. Evaluation of abdominal CT images showed 18% noise reduction, with 27% and 28% increases in the signal-to-noise and contrast-to-noise ratios, respectively. These results confirmed that the proposed aperture-type radiation regulator can reduce radiation exposure without affecting primary radiation that creates medical images. The results also confirmed that the radiation regulator effectively improves the quality of medical images.

A Method to Realize Robust Flexible Electronically Tunable Antennas Using Polymer-Embedded Conductive Fabric

A new approach to realize robust, flexible, and electronically tunable wearable antennas is presented. Conductive fabric is used to form the conducting parts of the antenna on a polydimethylsiloxane (PDMS) substrate. Then the antenna and the lumped (active and passive) elements, required for electronic tuning and RF choking, are fully encapsulated with additional layers of PDMS. As a concept demonstration, a new frequency-reconfigurable antenna has been designed and fabricated. The details of the prototype manufacturing process are described. Two UWB human muscle equivalent phantoms were also fabricated for testing purposes. Furthermore, the antenna was subjected to several investigations on its RF performance (both in free space and on a flat phantom) and mechanical stability. The latter includes bending tests on several locations on a human-body shaped phantom and washing in a household washing machine. Good agreement between predicted and experimental results (both in free space and on the phantom) is observed, validating the proposed concept. The tests demonstrated that lumped components and other antenna parts remained intact and in working order even under extreme bending (to a bending radius of 28 mm) and after washing, thus maintaining the overall antenna performance including good frequency reconfigurability from 2.3 to 2.68 GHz. To the best of our knowledge, all these features have never been demonstrated in previously published electronically tunable antennas.

Dual-Band Dual-Mode Textile Antenna on PDMS Substrate for Body-Centric Communications

A dual-band antenna for off- and on-body communications in the 2.45- and 5.8-GHz Industrial, Scientific, and Medical bands is presented. The two radiation characteristics, i.e., patch-like radiation for the off-body link and monopole-like radiation for the on-body link, are achieved by utilizing inherently generated TM $_{11}$ and TM $_{02}$ modes of a circular patch antenna. A shorting pin and two arc-shaped slots are employed to tune both modes to the desired operating frequencies. This approach allows a realization of a dual-band dual-mode antenna with a very simple structure, i.e., a single radiator with a simple feed. A further advantage of the proposed antenna is its realization using a silver fabric integrated onto a flexible polydimethylsiloxane substrate that makes it more practical for wearable applications. An experimental investigation of the antenna performance has been carried out in free space and on a semisolid human muscle equivalent phantom, which shows a robust performance against the human body loading effect. When placed on the phantom, the measured bandwidths of 84 and 247 MHz in the 2.45- and 5.8-GHz bands, respectively, are achieved with the corresponding peak gains of 4.16 and 4.34 dBi, indicating a promising candidate for body-centric communications.

Low‐profile dipole antenna with parasitic elements for WBAN applications

ABSTRACTIn this letter, a low‐profile dipole antenna with parasitic elements for WBAN applications is proposed. The antenna consists of a dipole radiator, two parasitic elements, and a ground with a slot. The resonance created by the two parasitic elements along with the basic resonance of the dipole radiator, provides dual resonances covering the 5.8 GHz ISM band. By adding the slot in the ground plane, the impedance matching is improved and the resonance frequency is lowered. The antenna has enhanced radiation along the near phantom surface in the 5.8 GHz ISM band due to the parasitic elements. The proposed antenna is placed on a human equivalent flat phantom in order to analyze the performance of the antenna on a human body. Regardless of the existence of the phantom, the antenna stably operates in the 5.8 GHz ISM band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1093–1097, 2016

Low-Profile Repeater Antenna with Parasitic Elements for On-On-Off WBAN Applications

A low-profile repeater antenna with parasitic elements for on-on-off WBAN applications is proposed. The proposed antenna consists of a planar inverted-F antenna (PIFA), two parasitic elements, and a ground plane with a slot. Due to the slot, the impedance matching of the resonance formed by the PIFA is improved, which makes the proposed antenna operate in the 5.8 GHz industrial, scientific, and medical (ISM) band. To cover the 5.2 GHz wireless local area network (WLAN) band, a dual resonance characteristic is realized by the slot and the two parasitic elements. The first coupling between the PIFA and the slot not only makes the slot operate as a resonator, but also forms secondary coupling between the slot and the two parasitic elements. The two parasitic elements operate as an additional resonator due to secondary coupling. The antenna has the enhanced near surface radiation in the 5.8 GHz ISM band due to addition of the slot and radiation toward off-body direction in the 5.2 GHz WLAN band. In order to evaluate antenna performance considering the human body effect, the antenna characteristics on a human equivalent phantom are analyzed.

Dual‐band on‐body antenna for in‐on‐on WBAN repeater applications

ABSTRACTA dual‐band on‐body antenna for in‐on‐on wireless body area network repeater applications is proposed. This antenna consists of a dual‐patch antenna and a zeroth‐order resonance (ZOR) element. The two patch antenna elements form dual resonances that cover the 2.4 GHz ISM band. In addition, a triangle cut made at the lower edge of patch Element 1 improves the impedance matching in the 2.4 GHz ISM band. The ZOR element operates in the 403 MHz MICS band. The antenna has near surface radiation in the 2.4 GHz ISM band and nearly omnidirectional radiation in the 403 MHz MICS band. To evaluate the performance of the antenna on a human body, the proposed antenna is placed on a human equivalent flat phantom. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:436–441, 2016

Evaluation of nonuniform field exposures with coupling factors

In this study, the safety compliance for nonuniform field exposures is discussed using coupling factor concepts. The coupling factor, which is defined in the International Electrotechnical Commission 62311 standard, is extended to consider the effects of harmonics and also to apply to the specific absorption rate (for frequencies up to 30 MHz). The proposed compliance procedure is applied to and demonstrated for a prototype wireless power transfer (WPT) system with induction coupling operating at the fundamental frequency in 140 kHz band. First, measurements confirm that the perturbation of the external magnetic field strength and S11 parameter of a one-loop antenna by a human-equivalent phantom are sufficiently small, suggesting the applicability of the magneto-quasi-static approximation to frequencies up to 30 MHz. Then, the frequency characteristics of the coupling factor are derived for the WPT system. For the prototype system that is not optimized for commercial usage, the maximum allowable transmitting power is relaxed by a factor of 23 with the proposed procedure. The contribution of the harmonics decreased the allowable transmitting power by 39%, indicating their importance for safety compliance.

Evaluation of Effective Dose with Two-dimensional and Three-dimensional Dental Imaging Devices

ABSTRACT Objectives Different types of X-ray equipment are used in dental radiology. Purpose of this study was to measure the absorbed doses of some critical organs and tissues in head and neck which were exposed by dental imaging devices that are used routinely in dental radiology. Materials and Methods Radiation exposures were performed by using a human equivalent head phantom and dose measurements were determined with thermoluminescent dosimeters (TLD). After exposure of the phantom with dental imaging devices, absorbed and effective doses of critical organs were determined. Results Digital imaging systems produced lower effective doses. Effective doses of cone beam computed tomography (CBCT) and multi-slice computed tomography (MSCT) devices were close to each other. Conclusion Effective doses of digital imaging devices were measured lower than conventional imaging devices. Effective doses of 3D imaging devices were measured higher than all the other imaging devices. However, effective doses of 3D imaging devices were considered in acceptable levels. How to cite this article Eren H, Gorgun S. Evaluation of Effective Dose with Two-dimensional and Three-dimensional Dental Imaging Devices. J Contemp Dent 2015;5(2):80-85.

A Low-Profile IR-UWB Antenna With Ring Patch for WBAN Applications

A compact ultrawideband (UWB) antenna for on- body communications is proposed herein. The antenna consists of a mono- cone and a shorted ring patch. By using a ring patch with four shorting pins, the proposed antenna operates at TM41 resonance mode in the low-frequency band and achieves a compact low-profile structure with monopole-like radiation characteristics. The antenna has overall dimensions of 64 mm × 64 mm × 7 mm (0.64 λ0 × 0.64 λ0 × 0.07 λ0at 3 GHz) in the impulse radio UWB (3.1 GHz - 10.6 GHz) band and a 10-dB return loss bandwidth of 121.1% in the range from 2.8 to 11.4 GHz. The antenna performance was simulated and measured in free space and on a homogeneous human equivalent phantom to account for the human body effect. The results show that the antenna characteristics are relatively stable regardless of the existence of a human phantom.

인체 상 위치를 고려한 다양한 WBAN 안테나 설계

WBAN은 다양한 응용 가능성 때문에 최근 들어 많은 관심을 받고 있다. 본 논문에서는 기기의 위치에 따른 WBAN 통신 환경에 적합한 몇 가지 안테나와 모의 인체 제작에 대하여 소개하고자 한다. WBAN 시스템은 인체 내부 및 인체 표면에서 동작하므로 고유전율 및 고도전율을 갖는 인체 매질에 대한 영향을 고려해야 하며, 특히 안테나는 근역장 매질 특성에 따라 안테나의 방사 특성 및 반사 손실 특성이 변하게 되므로, 이를 고려한 안테나 설계가 요구된다. 또한, 안테나의 인체 영향을 고려하기 위해 모의 인체를 이용해 안테나를 설계하고 측정하였다. 서론에서는 WBAN 통신 채널의 분류를 소개하고, 각각의 통신 채널에 적합한 안테나의 특성에 대해 간단히 언급하였다. 제안된 몇 가지 안테나 사례 및 모의 인체 구현에 대하여 논의하였다. 결론에서는 안테나 설계 시 고려해야 할 사항과 향후 연구에 대해 언급하였다. WBAN has received great attention recently due to its versatile applicability. In this paper, antennas suitable for WBAN communication depending on the locations of mobile devices and the manufacturing of a human equivalent phantom are introduced. The effect of the body on the communication performance is largely dependent on the locations of devices. Specifically, the radiation and return loss characteristics of the antenna are greatly influenced by the characteristics of a medium existing in the near-field of an antenna. Thus, the proper WBAN antenna design is important in establishing a successful communication link between the transceivers. To consider the effect of the body on the antenna performance, the human equivalent phantom is also important factor in the WBAN antenna design and measurement. In introduction, categorization of the WBAN communication channel is introduced and antenna characteristics required for each communication channel are described. In the main subject section, several WBAN antenna design examples along with the implementation of the human equivalent phantom are discussed. In conclusion, the factors, which have to be considered in the design process, and future research are mentioned.

Planar MIMO Antenna with Slits for WBAN Applications

A planar MIMO antenna with slits for WBAN applications is proposed. The antenna consists of two PIFAs, ground pads, and two slits. By adding ground pads, the antenna size is reduced with improved impedance matching. Through two slits in a ground plane, the isolation characteristic is improved and the resonant frequency can be controlled. To analyze the antenna performance on a human body, the proposed antenna on a human equivalent flat phantom is investigated through simulations. Regardless of the existence of the phantom, the antenna operates in 2.4 GHz ISM band with the isolation higher than 18 dB.

A meandered inverted-f capsule antenna for an ingestible medical communication system

In this article, a capsule antenna used in an ingestible medical device is proposed. To achieve miniaturization and a wide bandwidth, an inverted-F antenna with a meandered strip line was used. The antenna performance in a human voxel model is analyzed through simulation, and the performance of the fabricated antenna is verified by comparing the measured data with that of the simulation, when the antenna is placed in a human-equivalent liquid phantom. To investigate the performance of the proposed antenna in an indoor environment, a typical sickroom model is set-up, and the propagation characteristics between the proposed antenna and the base station are analyzed at 1.4 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1761–1765, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26869

Effective radiation dose of ProMax 3D cone-beam computerized tomography scanner with different dental protocols

The aim of this study was to compare effective doses resulting from different scan protocols for cone-beam computerized tomography (CBCT) using International Commission on Radiological Protection (ICRP) 1990 and 2007 calculations of dose. Average tissue-absorbed dose, equivalent dose, and effective dose for a ProMax 3D CBCT with different dental protocols were calculated using thermoluminescent dosimeter chips in a human equivalent phantom. Effective doses were derived using ICRP 1990 and the superseding 2007 recommendations. Effective doses (ICRP 2007) for default patient sizes from small to large ranged from 102 to 298 μSv. The coefficient of determination (R(2)) between tube current and effective dose (ICRP 2007) was 0.90. When scanning with lower resolution settings, the effective doses were reduced significantly (P < .05). ProMax 3D can provide a wide range of radiation dose levels. Reduction in radiation dose can be achieved when using lower settings of exposure parameters.

Dosimetry study for a new in vivo X-ray fluorescence (XRF) bone lead measurement system

A new 109Cd γ-ray induced bone lead measurement system has been developed to reduce the minimum detectable limit (MDL) of the system. The system consists of four 16mm diameter detectors. It requires a stronger source compared to the “conventional” system. A dosimetry study has been performed to estimate the dose delivered by this system. The study was carried out by using human-equivalent phantoms. Three sets of phantoms were made to estimate the dose delivered to three age groups: 5-year old, 10-year old and adults. Three approaches have been applied to evaluate the dose: calculations, Monte Carlo (MC) simulations, and experiments. Experimental results and analytical calculations were used to validate MC simulation. The experiments were performed by placing Panasonic UD-803AS TLDs at different places in phantoms that representing different organs. Due to the difficulty of obtaining the organ dose and the whole body dose solely by experiments and traditional calculations, the equivalent dose and effective dose were calculated by MC simulations. The result showed that the doses delivered to the organs other than the targeted lower leg are negligibly small. The total effective doses to the three age groups are 8.45/9.37μSv (female/male), 4.20μSv, and 0.26μSv for 5-year old, 10-year old and adult, respectively. An approval to conduct human measurements on this system has been received from the Research Ethics Board based on this research.

Comparison between the calculated and measured dose distributions for four beams of 6 MeV linac in a human-equivalent phantom

Radiation dose distributions in various parts of the body are of importance in radiotherapy. Also, the percent depth dose at different body depths is an important parameter in radiation therapy applications. Monte Carlo simulation techniques are the most accurate methods for such purposes. Monte Carlo computer calculations of photon spectra and the dose ratios at surfaces and in some internal organs of a human equivalent phantom were performed. In the present paper, dose distributions in different organs during bladder radiotherapy by 6 MeV X-rays were measured using thermoluminescence dosimetry placed at different points in the human-phantom. The phantom was irradiated in exactly the same manner as in actual bladder radiotherapy. Four treatment fields were considered to maximize the dose at the center of the target and minimize it at non-target healthy organs. All experimental setup information was fed to the MCNP-4b code to calculate dose distributions at selected points inside the proposed phantom. Percent depth dose distribution was performed. Also, the absorbed dose as ratios relative to the original beam in the surrounding organs was calculated by MCNP-4b and measured by thermoluminescence dosimetry. Both measured and calculated data were compared. Results indicate good agreement between calculated and measured data inside the phantom. Comparison between MCNP-4b calculations and measurements of depth dose distribution indicated good agreement between both.

New method of voxel phantom creation: application for whole-body counting calibration and perspectives in individual internal dose assessment

The purpose of this work is to present an innovative approach for the creation and application of voxel phantoms associated with the Monte Carlo calculation (MCNP) for the calibration of whole-body counting systems dedicated to the measurement of fission and activation products. The new method is based on a graphical user interface called 'OEDIPE' that allows to simulate a whole measurement process using all measurement parameters, the final goal being to approach a numerical calibration of the facilities. The creation of voxel phantoms and validation of the method are presented in this paper using the IGOR phantom. Finally, the efficiency of the method is discussed, in particular, with the perspective of validating IGOR as a suitable human-equivalent phantom and for the assessment of uncertainties in dose estimation due to the inhomogeneous distribution of activity in the body, correlated to the bio-kinetic behaviour of the radionuclides.