Abstract: The aim of the study is evaluation of absorbed doses for thyroids by using neck phantoms. For this purpose, it was arranged the irradiation set with different phantoms. Three different materials were used for phantom materials as, water, parafine and wood. The phantoms were three different dimensions for simulation of different ages and human race for each material. Co-60 gammao source was used for irradiation and the experimental procedure applied rigorously with narrow beam geometry. As the results of the experiments the relative radiation doses are evaluated for therapic applications for thyroids and backscattering factors were calculated and shown that water, parafine and wood can appropriate for phantom material with the converge values of backscattering factors.
Abstract: This paper investigates the impact of the hand-hold
positions on both antenna performance and the specific absorption
rate (SAR) induced in the user-s head. A cellular handset with
external antenna operating at GSM-900 frequency is modeled and
simulated using a finite difference time-domain (FDTD)-based
platform SEMCAD-X. A specific anthropomorphic mannequin
(SAM) is adopted to simulate the user-s head, whereas a semirealistic
CAD-model of three-tissues is designed to simulate the
user-s hand. The results show that in case of the handset in hand close
to head at different positions; the antenna total efficiency gets
reduced to (14.5% - 5.9%) at cheek-position and to (27.5% to 11.8%)
at tilt-position. The peak averaged SAR1g values in head close to
handset without hand, are 4.67 W/Kg and 2.66 W/Kg at cheek and
tilt-position, respectively. Due to the presence of hand, the SAR1g in
head gets reduced to (3.67-3.31 W/Kg) at cheek-position and to
(1.84-1.64 W/Kg) at tilt-position, depending on the hand-hold
position.
Abstract: This paper predicts the effect of the user-s hand-hold
position on the Total Isotropic Sensitivity (TIS) of GSM900/1800
mobile phone antennas of realistic in-use conditions, where different
semi-realistic mobile phone models, i.e., candy bar and clamshell, as
well as different antenna types, i.e., external and internal, are
simulated using a FDTD-based platform. A semi-realistic hand model
consisting of three tissues and the SAM head are used in simulations.
The results show a considerable impact on TIS of the adopted mobile
phone models owing to the user-s hand presence at different
positions, where a maximum level of TIS is obtained while grasping
the upper part of the mobile phone against head. Maximum TIS
levels are recorded in talk position for mobile phones with external
antenna and maximum differences in TIS levels due to the hand-hold
alteration are recorded for clamshell-type phones.
Abstract: The paper presents the multi-element synthetic
transmit aperture (MSTA) method with a small number of elements
transmitting and all elements apertures in medical ultrasound
imaging. As compared to the other methods MSTA allows to
increase the system frame rate and provides the best compromise
between penetration depth and lateral resolution.
In the experiments a 128-element linear transducer array with
0.3 mm pitch excited by a burst pulse of 125 ns duration were used.
The comparison of 2D ultrasound images of tissue mimicking
phantom obtained using the STA and the MSTA methods is
presented to demonstrate the benefits of the second approach. The
results were obtained using SA algorithm with transmit and receive
signals correction based on a single element directivity function.
Abstract: Sedimentation process resulting from soil erosion in
the water basin especially in arid and semi-arid where poor
vegetation cover in the slope of the mountains upstream could
contribute to sediment formation. The consequence of sedimentation
not only makes considerable change in the morphology of the river
and the hydraulic characteristics but would also have a major
challenge for the operation and maintenance of the canal network
which depend on water flow to meet the stakeholder-s requirements.
For this reason mathematical modeling can be used to simulate the
effective factors on scouring, sediment transport and their settling
along the waterways. This is particularly important behind the
reservoirs which enable the operators to estimate the useful life of
these hydraulic structures. The aim of this paper is to simulate the
sedimentation and erosion in the eastern and western water intake
structures of the Dez Diversion weir using GSTARS-3 software. This
is done to estimate the sedimentation and investigate the ways in
which to optimize the process and minimize the operational
problems. Results indicated that the at the furthest point upstream of
the diversion weir, the coarser sediment grains tended to settle. The
reason for this is the construction of the phantom bridge and the
outstanding rocks just upstream of the structure. The construction of
these along the river course has reduced the momentum energy
require to push the sediment loads and make it possible for them to
settle wherever the river regime allows it. Results further indicated a
trend for the sediment size in such a way that as the focus of study
shifts downstream the size of grains get smaller and vice versa. It
was also found that the finding of the GSTARS-3 had a close
proximity with the sets of the observed data. This suggests that the
software is a powerful analytical tool which can be applied in the
river engineering project with a minimum of costs and relatively
accurate results.
Abstract: The objective this study was to characterize and
develop anthropomorphic liver phantoms in tomography hepatic
procedures for quality control and improvement professionals in
nuclear medicine. For the conformation of the anthropomorphic
phantom was used in plaster and acrylic. We constructed three
phantoms representing processes with liver cirrhosis. The phantoms
were filled with 99mTc diluted with water to obtain the scintigraphic
images. Tomography images were analyzed anterior and posterior
phantom representing a body with a greater degree cirrhotic. It was
noted that the phantoms allow the acquisition of images similar to
real liver with cirrhosis. Simulations of hemangiomas may contribute
to continued professional education of nuclear medicine, on the
question of image acquisition, allowing of the study parameters such
of the matrix, energy window and count statistics.
Abstract: The work describes the use of a synthetic transmit
aperture (STA) with a single element transmitting and all elements
receiving in medical ultrasound imaging. STA technique is a novel
approach to today-s commercial systems, where an image is acquired
sequentially one image line at a time that puts a strict limit on the
frame rate and the amount of data needed for high image quality. The
STA imaging allows to acquire data simultaneously from all
directions over a number of emissions, and the full image can be
reconstructed.
In experiments a 32-element linear transducer array with 0.48 mm
inter-element spacing was used. Single element transmission aperture
was used to generate a spherical wave covering the full image region.
The 2D ultrasound images of wire phantom are presented obtained
using the STA and commercial ultrasound scanner Antares to
demonstrate the benefits of the SA imaging.
Abstract: Functional gastrointestinal disorders affect millions of people spread all age regardless of race and sex. There are, however, rare diagnostic methods for the functional gastrointestinal disorders because functional disorders show no evidence of organic and physical causes. Our research group identified recently that the gastrointestinal tract well in the patients with the functional gastrointestinal disorders becomes more rigid than healthy people when palpating the abdominal regions overlaying the gastrointestinal tract. Aim of this study is, therefore, to develop a diagnostic system for the functional gastrointestinal disorders based on ultrasound technique, which can quantify the characteristic above related to the rigidity of the gastrointestinal tract well. Ultrasound system was designed. The system consisted of transmitter, ultrasonic transducer, receiver, TGC, and CPLD, and verified via a phantom test. For the phantom test, ten soft-tissue specimens were harvested from porcine. Five of them were then treated chemically to mimic a rigid condition of gastrointestinal tract well, which was induced by functional gastrointestinal disorders. Additionally, the specimens were tested mechanically to identify if the mimic was reasonable. The customized ultrasound system was finally verified through application to human subjects with/without functional gastrointestinal disorders (Normal and Patient Groups). It was identified from the mechanical test that the chemically treated specimens were more rigid than normal specimen. This finding was favorably compared with the result obtained from the phantom test. The phantom test also showed that ultrasound system well described the specimen geometric characteristics and detected an alteration in the specimens. The maximum amplitude of the ultrasonic reflective signal in the rigid specimens (0.2±0.1Vp-p) at the interface between the fat and muscle layers was explicitly higher than that in the normal specimens (0.1±0.0Vp-p). Clinical tests using our customized ultrasound system for human subject showed that the maximum amplitudes of the ultrasonic reflective signals near to the gastrointestinal tract well for the patient group (2.6±0.3Vp-p) were generally higher than those in normal group (0.1±0.2Vp-p). Here, maximum reflective signals was appeared at 20mm depth approximately from abdominal skin for all human subjects, corresponding to the location of the boundary layer close to gastrointestinal tract well. These results suggest that newly designed diagnostic system based on ultrasound technique may diagnose enough the functional gastrointestinal disorders.
Abstract: Medical image registration is the key technology in image guided radiation therapy (IGRT) systems. On the basis of the previous work on our IGRT prototype with a biorthogonal x-ray imaging system, we described a method focused on the 2D/2D rigid-body registration using multiresolution pyramid based mutual information in this paper. Three key steps were involved in the method ： firstly, four 2D images were obtained including two x-ray projection images and two digital reconstructed radiographies（DRRs ） as the input for the registration ； Secondly, each pair of the corresponding x-ray image and DRR image were matched using multiresolution pyramid based mutual information under the ITK registration framework ； Thirdly, we got the final couch offset through a coordinate transformation by calculating the translations acquired from the two pairs of the images. A simulation example of a parotid gland tumor case and a clinical example of an anthropomorphic head phantom were employed in the verification tests. In addition, the influence of different CT slice thickness were tested. The simulation results showed that the positioning errors were 0.068±0.070, 0.072±0.098, 0.154±0.176mm along three axes which were lateral, longitudinal and vertical. The clinical test indicated that the positioning errors of the planned isocenter were 0.066, 0.07, 2.06mm on average with a CT slice thickness of 2.5mm. It can be concluded that our method with its verified accuracy and robustness can be effectively used in IGRT systems for patient setup.
Abstract: The stereophotogrammetry modality is gaining more widespread use in the clinical setting. Registration and visualization of this data, in conjunction with conventional 3D volumetric image modalities, provides virtual human data with textured soft tissue and internal anatomical and structural information. In this investigation computed tomography (CT) and stereophotogrammetry data is acquired from 4 anatomical phantoms and registered using the trimmed iterative closest point (TrICP) algorithm. This paper fully addresses the issue of imaging artifacts around the stereophotogrammetry surface edge using the registered CT data as a reference. Several iterative algorithms are implemented to automatically identify and remove stereophotogrammetry surface edge outliers, improving the overall visualization of the combined stereophotogrammetry and CT data. This paper shows that outliers at the surface edge of stereophotogrammetry data can be successfully removed automatically.
Abstract: Dynamic shear test on simulated phantom can be used
to validate magnetic resonance elastography (MRE) measurements.
Phantom gel has been usually utilized for the cell culture of cartilage
and soft tissue and also been used for mechanical property
characterization using imaging systems. The viscoelastic property of
the phantom would be important for dynamic experiments and
analyses. In this study, An axisymmetric FE model is presented for
determining the dynamic shear behaviour of brain simulated phantom
using ABAQUS. The main objective of this study was to investigate
the effect of excitation frequencies and boundary conditions on shear
modulus and shear viscosity in viscoelastic media.
Abstract: Electric impedance imaging is a method of
reconstructing spatial distribution of electrical conductivity inside a
subject. In this paper, a new method of electrical impedance imaging
using eddy current is proposed. The eddy current distribution in the
body depends on the conductivity distribution and the magnetic field
pattern. By changing the position of magnetic core, a set of voltage
differences is measured with a pair of electrodes. This set of voltage
differences is used in image reconstruction of conductivity
distribution. The least square error minimization method is used as a
reconstruction algorithm. The back projection algorithm is used to
get two dimensional images. Based on this principle, a measurement
system is developed and some model experiments were performed
with a saline filled phantom. The shape of each model in the
reconstructed image is similar to the corresponding model,
respectively. From the results of these experiments, it is confirmed
that the proposed method is applicable in the realization of electrical
imaging.
Abstract: To investigate the applicability of the EDR-2 film for
clinical radiation dosimetry, percentage depth-doses, profiles and
distributions in open and dynamically wedged fields were measured
using film and compared with data from a Treatment Planning
system.The validity of the EDR2 film to measure dose in a plane
parallel to the beam was tested by irradiating 10 cm×10 cm and 4
cm×4 cm fields from a Siemens, primus linac with a 6MV beam and
a source-to-surface distance of 100 cm. The film was placed
Horizontally between solid water phantom blocks and marked
with pin holes at a depth of 10 cm from the incident beam surface.
The film measurement results, in absolute dose, were compared with
ion chamber measurements using a Welhoffer scanning water tank
system and Treatment Planning system. Our results indicate a
maximum underestimate of calculated dose of 8 % with Treatment
Planning system.
Abstract: The aim of this study was to develop a dynamic cardiac phantom for quality control in myocardial scintigraphy. The dynamic heart phantom constructed only contained the left ventricle, made of elastic material (latex), comprising two cavities: one internal and one external. The data showed a non-significant variation in the values of left ventricular ejection fraction (LVEF) obtained by varying the heart rate. It was also possible to evaluate the ejection fraction (LVEF) through different arrays of image acquisition and to perform an intercomparison of LVEF by two different scintillation cameras. The results of the quality control tests were satisfactory, showing that they can be used as parameters in future assessments. The new dynamic heart phantom was demonstrated to be effective for use in LVEF measurements. Therefore, the new heart simulator is useful for the quality control of scintigraphic cameras.
Abstract: The paper presents the study of synthetic transmit
aperture method applying the Golay coded transmission for medical
ultrasound imaging. Longer coded excitation allows to increase the
total energy of the transmitted signal without increasing the peak
pressure. Signal-to-noise ratio and penetration depth are improved
maintaining high ultrasound image resolution.
In the work the 128-element linear transducer array with 0.3 mm
inter-element spacing excited by one cycle and the 8 and 16-bit
Golay coded sequences at nominal frequencies 4 MHz was used.
Single element transmission aperture was used to generate a spherical
wave covering the full image region and all the elements received the
echo signals. The comparison of 2D ultrasound images of the wire
phantom as well as of the tissue mimicking phantom is presented to
demonstrate the benefits of the coded transmission. The results were
obtained using the synthetic aperture algorithm with transmit and
receive signals correction based on a single element directivity
function.
Abstract: This paper proposes new enhancement models to the
methods of nonlinear anisotropic diffusion to greatly reduce speckle
and preserve image features in medical ultrasound images. By
incorporating local physical characteristics of the image, in this case
scatterer density, in addition to the gradient, into existing tensorbased
image diffusion methods, we were able to greatly improve the
performance of the existing filtering methods, namely edge
enhancing (EE) and coherence enhancing (CE) diffusion. The new
enhancement methods were tested using various ultrasound images,
including phantom and some clinical images, to determine the
amount of speckle reduction, edge, and coherence enhancements.
Scatterer density weighted nonlinear anisotropic diffusion
(SDWNAD) for ultrasound images consistently outperformed its
traditional tensor-based counterparts that use gradient only to weight
the diffusivity function. SDWNAD is shown to greatly reduce
speckle noise while preserving image features as edges, orientation
coherence, and scatterer density. SDWNAD superior performances
over nonlinear coherent diffusion (NCD), speckle reducing
anisotropic diffusion (SRAD), adaptive weighted median filter
(AWMF), wavelet shrinkage (WS), and wavelet shrinkage with
contrast enhancement (WSCE), make these methods ideal
preprocessing steps for automatic segmentation in ultrasound
imaging.
Abstract: The Brazilian legislation has only established
diagnostic reference levels (DRLs) in terms of Multiple Scan
Average Dose (MSAD) as a quality control parameter for computed
tomography (CT) scanners. Compliance with DRLs can be verified
by measuring the Computed Tomography Kerma Index (Ca,100) with
a pencil ionization chamber or by obtaining the kerma distribution in
CT scans with radiochromic films or rod shape lithium fluoride
termoluminescent dosimeters (TLD-100). TL dosimeters were used
to record kerma profiles and to determine MSAD values of a Bright
Speed model GE CT scanner. Measurements were done with
radiochromic films and TL dosimeters distributed in cylinders
positioned in the center and in four peripheral bores of a standard
polymethylmethacrylate (PMMA) body CT dosimetry phantom.
Irradiations were done using a protocol for adult chest. The
maximum values were found at the midpoint of the longitudinal axis.
The MSAD values obtained with three dosimetric techniques were
compared.
Abstract: The present paper presents a finite element model and
analysis for the interaction between a piezoresistive tactile sensor and
biological tissues. The tactile sensor is proposed for use in minimally
invasive surgery to deliver tactile information of biological tissues to
surgeons. The proposed sensor measures the relative hardness of soft
contact objects as well as the contact force. Silicone rubbers were
used as the phantom of biological tissues. Finite element analysis of
the silicone rubbers and the mechanical structure of the sensor were
performed using COMSOL Multiphysics (v3.4) environment. The
simulation results verify the capability of the sensor to be used to
differentiate between different kinds of silicone rubber materials.
Abstract: Most CT reconstruction system x-ray computed
tomography (CT) is a well established visualization technique in
medicine and nondestructive testing. However, since CT scanning
requires sampling of radiographic projections from different viewing
angles, common CT systems with mechanically moving parts are too
slow for dynamic imaging, for instance of multiphase flows or live
animals. A large number of X-ray projections are needed to
reconstruct CT images, so the collection and calculation of the
projection data consume too much time and harmful for patient. For
the purpose of solving the problem, in this study, we proposed a
method for tomographic reconstruction of a sample from a limited
number of x-ray projections by using linear interpolation method. In
simulation, we presented reconstruction from an experimental x-ray
CT scan of a Aluminum phantom that follows to two steps: X-ray
projections will be interpolated using linear interpolation method and
using it for CT reconstruction based upon Ordered Subsets
Expectation Maximization (OSEM) method.
Abstract: In the paper the study of synthetic transmit aperture
method applying the Golay coded transmission for medical
ultrasound imaging is presented. Longer coded excitation allows to
increase the total energy of the transmitted signal without increasing
the peak pressure. Moreover signal-to-noise ratio and penetration
depth are improved while maintaining high ultrasound image
resolution. In the work the 128-element linear transducer array with
0.3 mm inter-element spacing excited by one cycle and the 8 and 16-
bit Golay coded sequences at nominal frequency 4 MHz was used. To
generate a spherical wave covering the full image region a single
element transmission aperture was used and all the elements received
the echo signals. The comparison of 2D ultrasound images of the
tissue mimicking phantom and in vitro measurements of the beef liver
is presented to illustrate the benefits of the coded transmission. The
results were obtained using the synthetic aperture algorithm with
transmit and receive signals correction based on a single element
directivity function.