Human Body Phantom Research Articles

TU-A-218-02: Method to Study Image Quality in Cardiac Angiography Using a Computational Observer and Monte Carlo Simulations

Purpose: Study the trade‐offs between lesion detectability and dose to radiosensitive organs during angiographic procedures using Monte Carlo techniques for quantitatively estimating peak/average organdoses and an implementation of the Hotelling observer. Methods: We performed a signal‐known‐exactly/background‐known‐exactly experiment by using a high‐resolution cardiac phantom with detailed coronary artery models (freely available at hades.googlecode.com) registered in a human body phantom. A set of stenoses with varying sizes were synthesized and placed on the coronaries. To consider the scatter effect, we applied the Monte Carlo method (freely available at penmesh.googlecode.com) to simulate angiographic procedure for different X‐ray tube currents and peak voltages with an ideal detector model. Projections, pixel uncertainty estimates and peak/average organdoses were determined for each simulation setting. We repeated the simulation for 50 times with the exact particle number and the same scenario. By this mean, the projection pixel values for the same detector bin are under Poisson distribution. Finally, we calculated signal‐ noise‐ratio (SNR) (to be available at mumoc.googlecode.com) by using a Hotelling observer from projection images to assess signal detectability.Results: We estimated 11 peak organdoses normalized by SNR2 for a 6.86‐mm3 stenosis at 60/90/120 kVp. Our findings suggest that the spinal cord is the most exposed organ with peak doses increasing by 4.6 times when the tube voltage increases from 60 to 120 kVp. For a constant SNR, peak/average organdoses increase 1.1/1.4 times on average between 60 and 90 kVp, and 3.0/4.2 times on average from 60 to 120 kVp. Conclusions: We investigated peak organdoses for deterministic radiation injuries in cardiac angiographic procedures. We found that lower X‐ray tube voltages (60 to 90 kVp) produce higher SNR than 120 kVp. The methodology presented here can be applied to the optimization of X‐ray imaging systems for other radiological procedures besides angiography.

Evaluation of patient dose and operator dose in swallowing CT studies performed with a 320-detector-row multislice CT scanner

Recently, attempts to develop new types of swallowing function analysis with 320-detector-row multislice CT (320-MDCT) have been reported. The present report addresses (1) patient exposure, (2) operator exposure, and (3) spatial dose distribution. For dose measurement, a human-body phantom in which 303 thermoluminescent dosimeter elements were inserted and a survey meter was used. The patient position was confirmed with a single-volume scan at a tube voltage of 120 kV, a tube current of 10 mA, a rotation speed of 0.35 s/rot., a slice thickness of 0.5 mm, coverage of 160 mm, a scan field of view of 240 mm, a small focal spot size, and a gantry tilt angle of 22° (volume CT dose index displayed on the console 0.8 mGy, dose-length product 12.1 mGy cm). The effective dose for the patient in swallowing CT (SCT) was 3.9 mSv. The conversion factor for obtaining the effective dose was 0.0066 mSv/mGy cm. The effective dose for the operator was 0.002 mSv. In the operator exposure measurement, the ambient dose equivalent H*(10), that would be produced by an expanded and aligned radiation field at a depth 10 mm in the International Commission on Radiation Units and Measurements sphere, was 0.012 mSv. In this report, the safety of SCT, which has become possible with the introduction of 320-MDCT, was evaluated by measurement of the exposure to the patient and operator.

Numerical Dosimetry Schemes for the Simulation of Human Exposure to Pulsed High-Power Electromagnetic-Field Sources

In this paper, a numerical dosimetry scheme is proposed for pulsed high-power electromagnetic (HPEM) sources, which may induce biological effects such as “microwave hearing.” This auditory effect is linked to the specific absorption (SA) of biological tissue which is subject to regulatory limits. The presented simulation scheme using high-resolution human body phantoms takes into account the widespread spectral excitation range of pulse sources with the frequency dependency of dispersive biological tissue properties and of corresponding regulatory restrictions. Different examples of numerically computed and evaluated HPEM exposure scenarios are presented.

112 MRE評価に向けた生体模擬ファントムの有限要素法振動解析(セッション3 画像処理と振動モード応用技術)

112 MRE評価に向けた生体模擬ファントムの有限要素法振動解析(セッション3 画像処理と振動モード応用技術)

Flexible Dual-Frequency Applicator for Local Hyperthermia

A flexible and dual-frequency microstrip applicator for microwave local hyperthermia is described. It is designed on conformal liquid crystal polymer (LCP) substrate and operating at ISM (Industrial, Scientific and Medical) frequencies of 915 MHz and 2.45 GHz. To conform the body’s curvature, the applicator is bent on a cylindrical body. 3D electromagnetic CST Microwave Studio was used to determine the performance of the applicator and to evaluate the specific absorption rate (SAR) distribution in cylindrical human body phantom. The results obtained show that the antenna can be used in curved situation for uniform and superficial treatment.

An Omnidirectional Wrappable Compact Patch Antenna for Wireless Endoscope Applications

An inductively loaded compact patch antenna for a radiation frequency of 433 MHz is designed taking into consideration a human-body model and fabricated on a flexible liquid crystalline polymer (LCP) substrate, which is subsequently wrapped into a cylindrical shape to achieve a monopole-like omnidirectional radiation pattern for wireless endoscope applications. The wrapped patch antenna has a stretched length of 31 mm (0.07λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ), and its cylindrical form has a diameter of 10 mm and a width of 18.5 mm, whose dimensions are designed to be comparable to those of a commercially available capsule endoscope. Compared to a traditional patch antenna with the same radiation frequency, an 86% length reduction is achieved. Omnidirectionality is desired to increase the space coverage in communication between the randomly moving capsule inside and the receiver outside the body. The enclosed cylindrical cavity, surrounded by the ground plane of the patch, provides an electromagnetic interference (EMI) protected room that is useful for the placement of other electronic components. Multiple inductive notches on a patch designed for antenna size reduction are described by an equivalent circuit model. Human-body phantom solution is used for antenna characterization. The antenna, located at the outermost layer, serves not only as a good radiating unit, but also as the EMI protecting, mechanically supporting, packaging layer of the endoscope system.

Integrated Resonant Structure for Simultaneous Wireless Power Transfer and Data Telemetry

Novel miniaturized transmitting (TX) and receiving (RX) wireless power transfer (WPT) resonators operating at 6.78 MHz integrated with an antenna for the Medical Implant Communication Service (MICS) band (402–405 MHz) are devised and presented. Parametric analysis and matching circuits of the integrated basket-weave shaped resonator topology are discussed. WPT and antenna radiation efficiencies are analyzed and optimized using a finite element method numerical solver. The prototype model is fabricated and tested in vitro, using human-body phantom mimicking electrical properties of the human body tissues. The power transfer efficiency (PTE) of 35% at 20 mm distance and implanted antenna gain of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${-}$</tex></formula> 23 dBi are confirmed via simulations and measurements.

Secure wireless actuation of an implanted microvalve for drug delivery applications

The capability to wirelessly control fluid flow through a microvalve can emerge as anattractive technology enabling various biomedical applications such as remote drug deliveryand in vitro diagnostics. Contactless powering of such a microvalve is best addressed bynear-field inductive coupling due to its close proximity to the external interrogator. In thispaper, we propose the use of the same technique for secure remote interrogation andpowering of a human implantable, surface acoustic wave (SAW) correlation-based, passivemicrovalve. This is carried out by interrogating the microvalve with a Barkersequence-encoded BPSK signal. A numerical and experimental analysis of the biotelemetrylink for the microvalve was undertaken in the vicinity of numerical and physical humanbody phantoms, respectively. To accurately account for the path losses and to address thedesign optimization, the receiver coil/antenna was solved simultaneously withthe transmitter coil/antenna in the presence of a human body simulant usingthree-dimensional, high frequency electromagnetic FEM modelling. The received relativesignal strength was numerically and experimentally derived for a miniature (6 mm × 6 mm × 0.5 mm), square spiral antenna/coil when interrogated by a handheld8 cm × 5 cm × 0.2 cm square spiral antenna/coil in the near-field. Finally, the experimental results agreed wellwith the FEM analysis predictions and hence ascertained the applicability of the developedsystem for secure interrogation and remote powering of the newly proposed microvalve.

Sample-Induced Resistance Estimation in Magnetic Resonance Experiments: Simulation and Comparison of Two Methods

Signal-to-noise ratio estimation in magnetic resonance experiments requires the knowledge of sample-induced resistance value, where the sample can be protein solutes, cell suspensions, plants, animals, portions of human body or saline solution phantoms. Many authors studied sample–coil interaction using homogeneous infinitely long cylinders, spheres or half-space as approximations of the sample geometry. However, in real magnetic resonance experiments, both sample shape and dimensions can be very different with respect to these models. This paper describes and compares two different methods developed by the authors for sample-induced resistance estimation, both useful for predicting the performance of radio-frequency coils strictly coupled to the sample, where the knowledge of a sample–coil interaction model permits to estimate the different noise contributors. The main goal of our research is testing the proposed algorithms and finding their limitations by comparing their performances for a simple case which uses a sample simplified geometry. The first method, based on the magnetostatic approach, employs vector potential calculation and can be easily implemented for simple coils and sample geometries. The second method uses finite-difference time-domain algorithm and permits to simulate systems with various geometries, without approximations in sample and coil geometries. Comparison with experimental data, performed on three homebuilt surface coils each of them successively tuned at three different frequencies, demonstrated the differences in accuracy of the developed methods.

Peripheral Organ Dose Evaluation using a Human Body Phantom in Intensity Modulated Radiation Therapy for Lung Cancer with Helical Type Accelerator

Purpose: Intensity modulated radiation therapy (IMRT) is characterized by a relatively long period for beam exposure and consequently the risk for unnecessary exposure to non-targeted organs, mainly due to the scattered radiation, should be considered. The puposes of this study are to measure the absorbed dose of the peripheral organs during helical IMRT using a fluorescent glass dosimeter. Materials and Methods: In this research, we took lung cancer as a model and measured the absorbed dose of the peripheral organs during helical IMRT using a fluorescent glass dosimeter. The planning target volume (PTV) dose of 95% was set to be 5 Gy in the phantom. Results and Discussion: The highest exposure dose was observed for the breasts, which were on the PTV trajectory, with the left and right breasts receiving doses of 227.94 mGy and 371.90 mGy, respectively. The exposure doses of the left and right lenses were 3.13 mGy for the left lens and 3.22 mGy for the right lens. An exponential dose reduction to the distance from PTV was confirmed. Our data suggest that the doses for peripheral organs were acceptable in lung cancer case based on past literature search. However, the use of custom blocks for the eyes should be considered to prevent possible late occurance of cataract.

Debugging of ORNL Series of Mathematical Phantoms of Human Body

Series of mathematical phantoms of human body, given by Oak Ridge National Laboratory (ORNL), wasprogrammed as input files for MCNP-4B code. Detailed check of geometry of these phantoms performed byMCNP-4B,discoveredsomeminorerrors,thatresultedinoverlappingofsomeorgans. Threetypesoferrorswerefoundanddescribedhere: (a)colonoverlapswithpelvisbone;(b)facialskeletonpenetratetheheadskin,and(c)esophagusoverlapswithstomach. Theseerrorspreventcorrectexecutionofprogram. Proposalforcorrectionoftheseerrorsaregiveninthispaper.PACS:02.50.Ng,07.05.Tp,87.53.Bn

Characterisation of the PSI whole body counter by radiographic imaging

A joint project between the Paul Scherrer Institut (PSI) and the Institute of Radiation Physics was initiated to characterise the PSI whole body counter in detail through measurements and Monte Carlo simulation. Accurate knowledge of the detector geometry is essential for reliable simulations of human body phantoms filled with known activity concentrations. Unfortunately, the technical drawings provided by the manufacturer are often not detailed enough and sometimes the specifications do not agree with the actual set-up. Therefore, the exact detector geometry and the position of the detector crystal inside the housing were determined through radiographic images. X-rays were used to analyse the structure of the detector, and (60)Co radiography was employed to measure the core of the germanium crystal. Moreover, the precise axial alignment of the detector within its housing was determined through a series of radiographic images with different incident angles. The hence obtained information enables us to optimise the Monte Carlo geometry model and to perform much more accurate and reliable simulations.

Horizontal five‐arm folded dipole over metal screening plane for UHF RFID of dielectric objects

AbstractThe article is concerned with the extremely low‐profile foam dielectric five‐arm folded dipole antenna, which was developed and manufactured. The aforementioned antenna is situated on the metal screening plane and is used for UHF RFID of dielectric objects. It is designed with a complex input impedance Zin = 22 + j195 Ω at 866 MHz. Its efficiency was evaluated by Wheeler cap method with and without enclosed a human body phantom, it accounts for ∼40%, irrespective of whether the phantom is enclosed or not. The preliminary test of the identification range in buildings corridor was performed. The identification range reaches as far as 15.8 m. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2291–2294, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25475

Analysis of the human body on the radiation of FM handset antenna

AbstractA simple human body phantom model is proposed and used to demonstrate that the radiation efficiency of an internal handset antenna operating at the FM band can be improved for a particular holding position up to 10 dB. To corroborate the numerical results, an experiment using a real human body has been performed showing very good agreement. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2588–2590, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24686

The generation of simple compliance boundaries for mobile communication base station antennas using formulae for SAR estimation

In this paper, a procedure is proposed for generating simple and practical compliance boundaries for mobile communication base station antennas. The procedure is based on a set of formulae for estimating the specific absorption rate (SAR) in certain directions around a class of common base station antennas. The formulae, given for both whole-body and localized SAR, require as input the frequency, the transmitted power and knowledge of antenna-related parameters such as dimensions, directivity and half-power beamwidths. With knowledge of the SAR in three key directions it is demonstrated how simple and practical compliance boundaries can be generated outside of which the exposure levels do not exceed certain limit values. The conservativeness of the proposed procedure is discussed based on results from numerical radio frequency (RF) exposure simulations with human body phantoms from the recently developed Virtual Family.

Conformal Asymmetric Meandered Flare (AMF) Antenna for Body-Worn Applications

A conformal body-worn antenna is presented for communications at 300 MHz. The antenna consists of a thin broadband flared-dipole element printed on a thin (0.1 mm) FR4 substrate without metallic backing or other shielding. The letter presents the design approach for tuning, matching, and mounting the antenna on the human body. Measurements are given for a human body phantom, and these are compared to simulations. Different antenna positions for improved coverage are also presented.

Whole-body SAR in spheroidal adult and child phantoms in realistic exposure environment

In the past, the absorption of electromagnetic fields in a human body has been studied for a homogeneous worst-case single plane wave exposure or for a deterministic heterogeneous exposure, i.e. a measured incident electric field distribution. The work presented in this report, investigated the absorption in homogeneous spheroidal human body phantoms in a realistic exposure environment for frequencies ranging from 150 to 950 MHz using a statistical multipath exposure tool. The absorption has been investigated for five different sizes of the spheroid model. It is reported that the highest absorption occurs in the smallest phantom and that the ICNIRP reference levels do not satisfy the absorption limits for a realistic exposure scenario. Therefore, ICNIRP reference levels should be adapted to provide compliance to the basic restrictions for realistic exposure scenarios.

胸部X線検査における放射線防護エプロンの生殖腺防護効果

Depending on the facility, a radiation protective apron (protector) is used to protect the gonad from radiation exposure in chest radiography. To determine the necessity of using a protector during chest radiography, we measured the effect of the protector on the gonad in this study. First, using a human body phantom, we measured the absorbed dose of the female gonad with and without the protector, using a thermoluminescence dosimeter (TLD), and confirmed its protective effect. Using the protector, the absorbed dose was reduced to 28+/-2% and 39+/-4% for field sizes of 14 x 17 inch and 14 x 14 inch, respectively. Next, we used Monte Carlo simulation and confirmed, not only the validity of the actual measurement values, but also the fact that the influence of radiation on the absorbed dose of the gonad was mostly from scattered radiation from inside the body for the 14 x 17 inch field size, and also from the X-ray tube for the 14 x 14 inch field size. Although a certain protective effect is achieved by using the protector, the radiation dose to the gonad is only a few microGy even without a protector. Thus, the risk of a genetic effect would be as small as 10(-8). Given that acceptable risk is below 10(-6), we conclude the use of a radiation protective apron is not necessary for diagnostic chest radiography.

CT検査時における防護シートの遮蔽効果について

Because the exposure to radiation from CT scanning is higher than that from other X-ray diagnostic devices, it is necessary to lower this exposure. In this study, we placed a protective seat on the abdomen and dorsal side of a human body phantom. Three different kinds of CT units, with a single detector, four detectors, and 16 detectors, were used to compare the absorbed dose on the skin surface and uterus. Head and chest CT scans were taken with the standard protocol. The difference in exposure to the uterus with and without the protective shield was found to be small. Exposure to the skin surface was about 0.2 mGy without the protective seat. We found that the exposure dose to chest could be reduced as much as 50% by using the protective seat. Effective radiation differs depending on the institution, and these differences can be more than the amount that can be reduced by using the protective seat. Thus, we conclude that it is important for each institution to determine the best protocol optimization for each individual.

Reconstruction of extended current sources in a human body phantom applying biomagnetic measuring techniques

We have prepared a human body phantom for experimental verification of inverse solution techniques which are applied to magnetic (and electric) measuring data. Physical models of extended primary current sources were used to generate these fields. Magnetic field maps closed to the phantom surface were recorded by means of multi-channel biomagnetic measuring systems. Different deterministic optimization techniques were applied to both measured and simulated data to reconstruct the impressed current density distribution. We have found that all common used minimum norm methods (L/sub p/-norms, 1/spl les/p/spl les/2) cannot reconstruct the extension of current source distributions satisfactorily. The physical phantom was found to be a suitable tool for validation of source reconstruction techniques.