Human Body Phantom Research Articles

Compton imaging with 99mTc for human imaging

We have been developing a medical imaging system using a Compton camera and demonstrated the imaging ability of Compton camera for 99mTc-DMSA accumulated in rat kidneys. In this study, we performed imaging experiments using a human body phantom to confirm its applicability to human imaging. Preliminary simulations were conducted using a digital phantom with varying activity ratios between the kidney and body trunk regions. Gamma rays (141 keV) were generated and detected by a Compton camera based on a silicon and cadmium telluride (Si/CdTe) detector. Compton images were reconstructed with the list mode median root prior expectation maximization method. The appropriate number of iterations of the condition was confirmed through simulations. The reconstructed Compton images revealed two bright points in the kidney regions. Furthermore, the numerical value calculated by integrating pixel values inside the region of interest correlated well with the activity of the kidney regions. Finally, experimental studies were conducted to ascertain whether the results of the simulation studies could be reproduced. The kidneys could be successfully visualised. In conclusion, considering that the conditions in this study agree with those of typical human bodies and imaginable experimental setup, the Si/CdTe Compton camera has a high probability of success in human imaging. In addition, our results indicate the capability of (semi-) quantitative analysis using Compton images.

Basic evaluation of a novel 4D target and human body phantom

Stereotactic body radiation therapy (SBRT) is usually verified with a dynamic phantom or solid phantom, but there is a demand for phantoms that can accurately simulate tumor dynamics within an individual that would allow customized validation in every patient. We developed a new 4D dynamic target phantom (multi-cell 4D phantom) that allows simulation of tumor movement in patients. The basic quality and dynamic reproducibility of this new phantom was verified in this investigation. The newly developed multi-cell 4D phantom comprises four main components: soft tissue, bones, lungs, and tumor (target). The phantom structure was based on computed tomography (CT) data of a male. In this study, we investigated the basic performance of a multi-cell 4D phantom. All the CT numbers of the phantom were very close to those of human data. The geometric maximum amplitudes were 4.57 mm in the lateral direction, 4.59 mm in the ventrodorsal direction, and 3.68 mm in the cranio-caudal direction. Geometric errors were 0.84, 0.58, and 0.40 mm, respectively. Movements of the abdominal surface were stable for 60 s. Repeated measurements show no actual differences in target movements between multiple measurements and indicated high reproducibility (r > 0.97). End-to-end tests using Gafchromic film revealed a gamma pass rate of 98% or above (2 mm/3%). Although our phantom performed limited reproducibility in the movement of the patient tumor at present, a satisfactory level of precision was confirmed in general. This is a very promising device for use in the verification of radiation therapy for moving targets.

Registration accuracy with the low dose kilovoltage cone-beam CT: A phantom study.

Objective:The aim of this study was to investigate low-dose kilovoltage cone-beam CT (kV-CBCT) for image-guided radiotherapy, with a particular focus on the accuracy of image registration with low-dose protocols.Methods:Imaging doses were measured with a NOMEX semiconductor detector positioned at the front of head, thorax, and pelvis human body phantoms while kV-CBCT scans were acquired at different tube currents. Aspects of image quality (spatial resolution, noise, uniformity, contrast, geometric distortion, and Hounsfield unit sensitivity) and image registration accuracy using bone and soft tissue were evaluated.Results:With preset and the lowest tube currents, the imaging doses were 0.16 and 0.08 mGy, 5.29 and 2.80 mGy, and 18.23 and 2.69 mGy for head, thorax, and pelvis, respectively. Noise was the only quality aspect directly dependent on tube current, being increased by 1.5 times with a tube current half that of the preset in head and thorax, and by 2.2 times with a tube current 1/8 of the preset in the pelvis. Accurate auto-bone matching was performed within 1 mm at the lowest tube current. The auto-soft tissue matching could not be performed with the lowest tube current; however, manual-soft tissue matching could still be performed within 2 mm or less.Conclusion:Noise was the only image quality aspect dependent on the imaging dose. Auto-bone and manual-soft tissue matching could still be performed at the lowest imaging dose.Advances in knowledge:When optimizing kV-CBCT imaging dose, the impact on bone and soft tissue image registration accuracy should be evaluated.

Method and software for photon dose calculation in phantoms of human body

The current study is focused on the development of the method of the calculation of the dose quantities required for the assessment or limitation of the ionizing exposure (mean organ doses, effective dose, distribution of the absorbed dose in the critical organ) based on the measured characteristics of the fields of the photon computational (kerma free-in-air, readings of the individual dosimeters) with the energy of 0,02-10 mEv. The dedicated software was developed based on the results of the study, allowing estimating the values of more than 20 mean organ doses, effective dose and the distribution of the absorbed dose in the red bone marrow in 8 computational children and adult models. Additionally, it is possible to calculate the ratios of the effective dose to the readings of the “individual dosimeters”, placed in 48fixed points on the phantom surface. The developed method and software can be used for: (1) calculation of the doses from external exposure and estimation of the level of the radiation injuries in case of the acute radiation exposure of the staff and public; (2) development of the models of the exposure of the staff working in the radiation fields with non-uniform distribution of their characteristics; (3)planning of the countermeasures for the remediation of the consequences of the radioactive contamination (calculation of the routes and working time in contaminated zones); (4) education and training of the staff participating in the investigation and remediation of the consequences of the radioactive contamination.

Wearable and meshed wideband monopole antennas and their interactions with the human body

This study considers a wideband monopole antenna and its interactions with different separations from the human body phantom over a wide frequency. A meshed alternative version has also been developed which has similar performance to the circular wideband monopole antenna but requires less material. The specific absorption rate and efficiency of this antenna have been analysed as a function of separation distance and frequency. The mesh design has been fabricated by using embroidery and 3D printing techniques.

Dielectric properties of muscle and adipose tissue-mimicking solutions for microwave medical imaging applications

The aim of the present study was to synthesize mixture solutions which can accurately mimic the dielectric properties of biological tissues, specifically muscle and adipose tissues between 500 MHz and 50 GHz. Mixtures utilizing concentrations of bovine serum albumin (BSA) dissolved in phosphate buffered saline (PBS) and Ringer’s solutions were synthesized to mimic in vivo and ex vivo muscle tissues. Solutions consisting of concentrations of peanut oil and Triton X-100 (TX) in PBS and Ringer’s solutions were also synthesized to mimic in vivo and ex vivo adipose tissue. Results were then analysed and compared to measured dielectric properties of in vivo and ex vivo biological tissues from another previous study. Good agreement with said dielectric property measurements were obtained since the solutions from this study yielded low RMSE and RMSRE values. This implied that such solutions can be utilized in the construction of human body phantoms for narrowband and ultra-wideband microwave devices for near field breast cancer imaging.

Dose Reduction Protocol for Full Spine X-ray Examination Using Copper Filters in Patients With Adolescent Idiopathic Scoliosis.

A prospective case series. The aim of this study was to assess a new protocol for full spine X-ray using copper (Cu) filters to reduce radiation exposure in patients with adolescent idiopathic scoliosis (AIS). Radiation exposure is associated with an increased risk of cancer development in children. To reduce the radiation exposure without compromising the image quality using existing radiographic equipment, a new computed radiography protocol was optimized using a variety of heavy metal filters. Study 1: Whole spine radiographs were obtained using a human body phantom, and radiation doses without and with 0.1, 0.2, and 0.3 mm thick Cu filters were compared. Study 2: Patients with AIS who underwent posterior fusion were radiographically evaluated at follow-ups; the X-ray protocols with or without the use of 0.2-mm Cu filters were alternated between consecutive follow-ups. The image quality was independently evaluated using six points in the anterior-posterior (AP) view and seven in the lateral [left-right (LR)] view by three spine surgeons using a three-point grading system. Study 1: The surface doses while obtaining nonfiltered X-rays in AP and LR views were 0.31 and 0.93 mGy, respectively, whereas those with 0.1-, 0.2-, and 0.3-mm Cu filters were 0.16 and 0.52, 0.11 and 0.36, and 0.08 and 0.27 mGy, respectively.Study 2: In patients with AIS, the percentage of grade 3 scores (both endplates were identifiable) on AP-view images was 85% with nonfiltered X-rays and 75% with the filtered X-rays. However, there were no significant differences between the two protocols. On LR images, the frequency of grade 3 scores was significantly lower at Th2 and Th12 on filtered images than on nonfiltered ones. Whole spine radiographs using 0.2-mm Cu filters in patients with AIS could reduce radiation exposure more than 60% while preserving the image quality. 4.

Assessment of SAR in human body model with the cochlear implant inside a railway vehicle

Abstract This article details simulation and analysis of electromagnetic field distribution within a railway vehicle, with special focus on distribution thereof in human body phantom with a cochlear implant. Research was carried out using modelling of electromagnetic fields based on the Finite Integration Method. Simulations were performed and analysed in cases where passengers were exposed to long-term radiofrequency field stemming from the use of mobile phones during railway transport. Results were evaluated based on the specific absorption rate (SAR) – the measure of electromagnetic energy absorption in the body (in watts per kilogram [W/kg]). Dual band (900 and 1800MHz) PIFA antennas were designed and employed as radio frequency sources. The homogeneous passenger model includes a cochlear implant and dielectric properties are set according to the evaluated frequency band. Results have shown that the calculated maximum values of SAR are higher than those established within the European maximum SAR limit and additionally, the obtained values are higher than values obtained in simulation in open space.

Platform Tolerant, High Encoding Capacity Dipole Array-Plate Chipless RFID Tags

In this paper, we first carry out an in-depth review of the performance parameters of frequency-domain chipless RFID transponders in terms of their spatial density, spectral capacity, and comprehensive encoding capacity (bit/ $\lambda ^{2}$ /GHz) comprising both spatial and spectral performance, and platform tolerance. Secondly, we theoretically and numerically investigate the recently introduced and promising concept of the platform-tolerant chipless RFID transponder based on a detuned dipole array-plate that provides high encoding capacity. We propose, fabricate and measure a 20-bit transponder consisting of an array of 20 detuned dipoles closely coupled to a 60 $\times $ 60 mm2 metallic plate. The radar cross section at the level of −15 dBsm exhibits reliably recognizable minima corresponding to individual dipole resonances. When compared to other published frequency-domain chipless RFID transponders, the encoding capacity reaches 47.4 bit/ $\lambda ^{2}$ /GHz, which constitutes one of the highest values, while achieving a concurrently high level of radar cross section (RCS) reflection response and platform tolerance performance. The measurements confirm very good performance parameters in the cases when the transponder is attached to various packaging materials, such as cardboard, plastic, wood, metal or a human body phantom. The essential benefits of the presented solution include a very good frequency and amplitude stability in the RCS response, which enables a reliable reading of encoded information (if zero bits are coded). The double layer metallization represents an inherent property of the proposed solution, which is a necessary trade-off for high encoding capacity and contemporary platform tolerance.

Implantable CPW fed M Shaped Antenna for Biomedical Applications

Implantable medical device has become very popular in medical sector for proper diagnosis and treatment. If, this devices are wireless, then it will very effective for remote communication. For this wireless communication, antenna is a suitable thing. So, this paper presents the design Implantable CPW fed M-shaped antenna for biomedical applications. Coplanar waveguide fed technique is used with ground plane in this antenna. The antenna is designed by Alumina ceramic (Al2O3) substrate and Copper ground plane with dimensions (8mm × 7mm × 0.85mm) and Silicon material of 0.1mm thickness is used as a coating for human body safety. This antenna works under 2.42 GHz resonate frequency of ISM band (2.40-2.48 GHz). The bandwidth percent of the antenna at -10dB is 7.66%. The return loss characteristic of the antenna is -56.96 dB. Based on the conductivity and permittivity of different tissue (such as: Muscle, Fat. Skin) a simple 3D human body phantom structure is designed for implantation of CPW fed antenna. The antenna is designed and simulated with the help of CST software. The antenna parameters such as: Return loss, Smith Chart, VSWR, Gain, SAR have been discussed in the paper.

Dose distribution of protons and flux of secondary particles in breast proton therapy.

Introduction: Proton therapy is newer therapeutic method for early stage breast cancer. Proton beams release most of their energy in the Bragg peak and then will be a rapid decline in their end. When protons interact with matter, produce secondary particles like neutrons and gammas, and these unwanted radiation has no beneficial effect and also is believed to increase the risk of secondary cancers, so it’s necessary to assess these secondary particles. Monte Carlo algorithm is the most accurate calculation method in the dosimetry. MCNPX is a modern, general purpose Monte Carlo code that were used to model the transport and interactions of particles in patient’s body, also is currently the most commonly used MC codes for proton therapy. In this study, calculated flux of secondary particles like neutron and photon in vital organs and dose distribution of Proton in energy range of 40 to 70 with 10 single step. Materials and Methods: Analytical phantom of the human body, ORNL used to create the input files and Protons as pencil beam modeled in front of left breast with energy of 40 to 70 MeV for covering the left breast, eventually Counting sensors for tracking the trajectory of secondary particles and provide the necessary data were used. Results: the dose distribution of protons shows they can have covered the exact shape of tumor with high accuracy and release most of their energy on it, so it’s best feature of proton therapy also flux of secondary particles shows the most important organs are Heart-left ventricle and left lung in left breast proton therapy because of the most flux of secondary particles reach to them. Conclusion: flux of secondary particles in vital organs shows that even though proton therapy is a good option Due to the favorable Bragg peak radiation and delivers high dose to a small volume of cancerous tissue while the healthy structures will be spared during proton radiation therapy and flux of secondary particles are low but they are not low enough to be negligible.

Effect of Physical Factors on Electromagnetic Radiation Therapy Planning Dose Calculation in Computed Tomography

The tube voltage in computed tomography (CT) changes the Hounsfield Unit (HU) and affects the electromagnetic radiation therapy planning (RTP) dose calculation. In this study, physical factors (tube voltage, tube current) of CT were analyzed for their RTP effects. A CT density phantom (CTDP) was exposed to measure the HU with an RTP system while we controlled the physical factors. The human body phantom was exposed with different CT tube voltages (70 kVp, 80 kVp, 100 kVp, 120 kVp, and 140 kVp) and electromagnetic radiation dose calculations were performed with the RTP system. The HU decreased when tube voltage was increased, in particular, the largest gap was found in bone, which has a high density (1792 ± 54 at 70 kVp, 1065 ± 13 at 140 kVp). However, a remarkable HU gap was not observed with the changes in tube current. In RTP the calculated dose increased when the tube voltage was raised, in particular, we observed a 3 % gap in brain tissue and bone, a remarkable HU gap. The chest had a small HU gap because of its relatively low density. The RTP dose calculation with changes in tube voltage had a 3 % error, which is acceptable. However, it can be eliminated of because daily QA/QC was performed and a CT density curve with rational exposure condition can be applied to brain or spine patients who experience large errors. This method enables reduction of the error caused by the physical factors in CT.

Design of a printed symmetrical CPW-fed monopole antenna for on-body medical diagnosis applications

A printed symmetric co-planar waveguide (CPW)-fed on-body monopole antenna is proposed for use on human arm body phantoms in medical diagnosis applications. The advantages of the presented antenna over other on-body antennas include low profile, miniaturization, wide bandwidth, and lower reflection coefficient, with good peak gain and better impedance matching with the human phantom. The optimized antenna had dimensions of \(0.020\lambda _{0}\,\times \,0.015\lambda _{0}\,\times \,0.0013\lambda _{0}\) (where \(\lambda _{0}\) is the wavelength in air of the lowest operating frequency). It covers almost all bands used in wireless body area network (WBAN) applications, including Medical Implant Communication Service (MICS, 402–405 MHz), Wireless Medical Telemetry Service (WMTS, 420–1430 MHz), Medical-BAN (2.36–2.4 GHz) as well as industrial, scientific, and medical (ISM, 2.4–2.485 GHz). The fractional impedance bandwidth was simulated to be 170 % (0.25–3.05 GHz) in free space and 168 % (0.32–3.67 GHz) in the presence of a multilayer tissue model. The fractional impedance bandwidth was measured to be 162 % in free space and 161 % in the presence of a human arm body phantom.

Deterministic Equation of Self-Resonant Structures for Normal-Mode Helical Antennas Implanted in a Human Body

Recently, helical antennas had been used as a very small implantable antenna in a capsule endoscopy system. For a helical antenna, a normal-mode helical antenna (NMHA) is promising because of its small size and the completeness of an antenna design method, which has already been established. However, in the human body, the effects of human tissues on the electrical characteristics of an NMHA were not clarified. The most important aspect is to determine the self-resonant structures. In this letter, a deterministic equation is derived for the self-resonant structures of an NMHA in the human body. By utilizing simulation results of an electromagnetic simulator, a capacitive reactance equation is deduced based on the electric field distributions around an antenna. An inductive reactance equation is obtained by modifying the equation of free space to the condition of inside a dielectric material. Finally, by equating the capacitive and inductive reactance equations, the self-resonant equation is determined. The accuracy of the equation is ensured through the agreements of the antenna structures given by equations and electromagnetic simulations. Moreover, by fabricating an NMHA and a human body phantom, the measured results are obtained. The self-resonant structure is ensured through the measured results.

Preliminary research on body composition measurement using X-ray phase contrast imaging

Body composition measurement is of cardinal significance for medical and clinical applications. Currently, the dual-energy X-ray absorptiometry (DEXA) technique is widely applied for this measurement. In this study, we present a novel measurement method using the absorption and phase information obtained simultaneously from the X-ray grating-based interferometer (XGI). Rather than requiring two projection data sets with different X-ray energy spectra, with the proposed method, both the areal densities of the bone and the surrounding soft tissue can be acquired utilizing one projection data set. By using a human body phantom constructed to validate the proposed method, experimental results have shown that the compositions can be calculated with an improved accuracy comparing to the dual energy method, especially for the soft tissue measurement. Since the proposed method can be easily implemented on current XGI setup, it will greatly extend the applications of the XGI, and meanwhile has the potential to be an alternative to DEXA for human body composition measurement.

Radiotherapy-induced Cherenkov luminescence imaging in a human body phantom.

Radiation therapy produces Cherenkov optical emission in tissue, and this light can be utilized to activate molecular probes. The feasibility of sensing luminescence from a tissue molecular oxygen sensor from within a human body phantom was examined using the geometry of the axillary lymph node region. Detection of regions down to 30-mm deep was feasible with submillimeter spatial resolution with the total quantity of the phosphorescent sensor PtG4 near 1 nanomole. Radiation sheet scanning in an epi-illumination geometry provided optimal coverage, and maximum intensity projection images provided illustration of the concept. This work provides the preliminary information needed to attempt this type of imaging in vivo.

Investigation of the use of external aluminium targets for portal imaging in a medical accelerator using Geant4 Monte Carlo simulation

To install a low-Z target on the wedge tray mount of a medical linear accelerator to create a new image beam and to confirm image contrast enhancement. Experimental low-energy photon beams were produced with the linac running in the 6 MeV electron mode and with a low-Z target installed on the wedge tray mount [denoted 6 MeV (low-Z target)]. Geant4 Monte Carlo simulation was performed to analyse the energy spectrum and image contrast of a 6 MeV (low-Z target) beam. This study modelled the 6 MeV (low-Z target) beam and the 6 MV (megavoltage) radiotherapy photon beam and verified model validity by measurement. In addition, a contrast phantom was modelled to quantitatively compare the image contrasts of the 6 MeV (low-Z target) beam and the 6 MV radiotherapy photon beam. A low-Z target was fabricated to generate low-energy photons (25-150 keV) from incident electrons, and a portal image of the Alderson RANDO phantom was acquired using a clinical linear accelerator for qualitative analysis. The measured and calculated percentage depth dose of the 6 MV photon and 6 MeV (Al) beams were consistent within 1.5 and 1.6%, respectively, and calculated lateral profiles of the 6 MV photon beam and the 6 MeV (Al) beam were consistent with the measured results within 1.5 and 1.9%, respectively. Although low-energy photons (25-150 keV) of the 6 MV photon beam were only 0.3%, the Be, C, and Al low-Z targets, but not the Ti target, generated 34.4 to 38.5% low-energy photons. In 5 to 20 cm water phantoms, contrast of the 6 MeV (Al) beam was approximately 1.16 times greater than that of the 6 MV beam. The contrasts of 6 MeV (Al) and 6 MV photon beams in the 20 cm water phantom were ~34% lower than those in the 5 cm water phantom. 6 MeV (Al)/CR (computed radiography) images of the human body phantom were more vivid and detailed than 6 MV/EPID (electronic portal imaging device) and 6 MeV (Al)/EPID images. The experimental beam with a low-Z target, which was simply installed on the wedge tray mount of the radiotherapy linear accelerator, generated significantly more low-energy photons than the 6 MV radiotherapy photon beam, and provided better quality portal images. Advances in knowledge: This study shows that, unlike the existing low-Z beam studies, a low-Z target can be installed outside the head of a linear accelerator to improve portal image quality.

Effects of tissues and geometric shapes of phantoms on the specific energy absorption rate

In this article, the effects of tissues and geometric shape complexity of human body and head phantoms on the performance of radio frequency (RF) antennas/coils are investigated. The magnetic field, H, electric field, E, and the specific energy absorption rate of a meander dipole RF coil are calculated. The coil has been designed and fabricated at the University laboratory to resonate at the operating frequency of 7 T magnetic resonance imaging machines. Three phantoms of different geometries, homogeneous and inhomogeneous, are used in this work. It was noticed that the homogeneous spherical human head phantom exhibited higher peak SAR value (by an amount of 30%) than a homogeneous simple rectangular body model. Similarly, the geometric shape complexity of the homogeneous SAM head phantom played the dominant role in the accuracy of SAR results. The coil with the homogeneous SAM head model exhibited higher peak SAR value (by an amount of 84%) than the homogeneous spherical head model. In contrary, the inhomogeneous multilayered spherical head phantom exhibited SAR value less than the single-layered homogenous one (by 40%). The complexity of tissues, in particular, the adult skull bone thickness, reduces the intensity of power coupled to the brain.

HILBERT CURVE FRACTAL ANTENNA FOR DUAL ON- AND OFF-BODY COMMUNICATION

We present a Hilbert curve fractal antenna operating at 2.45 GHz ISM and 5.5 GHz WLAN bands. The proposed antenna employs a third-order Hilbert curve and two shorting vias for antenna miniaturization and dual-band/mode operation. At 2.45 GHz, the antenna exhibits a monopole-like radiation pattern, while at 5.5 GHz, it provides a broadside radiation pattern, suitable for simultaneous on- and off-body communication using two distinct frequency bands. The antenna footprint is as small as 25. 5m m× 25.5 mm. Simulation and measurement results demonstrate that the antenna gain is more than 1.9 dBi if the antenna is mounted on a ground larger than 40 mm × 40 mm. The effect of human body presence on antenna performance was investigated by means of full-wave simulations locating the antenna on a human body phantom. It is shown that the proposed antenna is capable of maintaining its free-space performance over the human body phantom except for the gain reduction of 2.5 dBi at 5.5 GHz band.

Optimal design of focused arrays for microwave‐induced hyperthermia

This study studies optimal design of focused antenna arrays for microwave-induced hyperthermia. The phases and amplitudes of the driving signals of array elements are determined by optimising the power transmission efficiency of the system consisting of the transmitting antenna array, a receiving antenna located in the target area, and an equivalent phantom representative of human tissues. On the basis of the proposed technique, a 4 × 2 focused patch array is designed to operate on a fat-mimicking phantom with working frequency at 433 MHz. The measured patterns for specific absorption rate indicate that the energy is focused in the desired spot and are in close agreement with simulations, which validate the optimisation method in a medium with low permittivity and low loss. A 4 × 3 focused patch array operating on a human body phantom with same working frequency is then designed, in which an air space and two additional dielectric layers have been introduced between the planar array and the body-mimicking phantom for impedance matching. A good focal performance at desired spot is also achieved, and the simulated and measured specific absorption rate patterns agree very well. This demonstrates the validity of the proposed design method in a medium with high permittivity and high loss.