Abstract: Ultrasound is useful in demonstrating bone mineral
density of regenerating osseous tissue as well as structural alterations.
A proposed ultrasound method, which included ultrasonography and
acoustic parameters measurement, was employed to evaluate its
efficacy in monitoring the bone callus changes in a rabbit tibial
distraction osteogenesis (DO) model.
The findings demonstrated that ultrasonographic images depicted
characteristic changes of the bone callus, typical of histology findings,
during the distraction phase. Follow-up acoustic parameters
measurement of the bone callus, including speed of sound, reflection
and attenuation, showed significant linear changes over time during
the distraction phase. The acoustic parameters obtained during the
distraction phase also showed moderate to strong correlation with
consolidated bone callus density and micro-architecture measured by
micro-computed tomography at the end of the consolidation phase.
The results support the preferred use of ultrasound imaging in the
early monitoring of bone callus changes during DO treatment.
Abstract: We study the problem of reconstructing a three dimensional binary matrices whose interiors are only accessible through few projections. Such question is prominently motivated by the demand in material science for developing tool for reconstruction of crystalline structures from their images obtained by high-resolution transmission electron microscopy. Various approaches have been suggested to reconstruct 3D-object (crystalline structure) by reconstructing slice of the 3D-object. To handle the ill-posedness of the problem, a priori information such as convexity, connectivity and periodicity are used to limit the number of possible solutions. Formally, 3Dobject (crystalline structure) having a priory information is modeled by a class of 3D-binary matrices satisfying a priori information. We consider 3D-binary matrices with periodicity constraints, and we propose a polynomial time algorithm to reconstruct 3D-binary matrices with periodicity constraints from two orthogonal projections.
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 purpose of this study is to introduce a new
interface program to calculate a dose distribution with Monte Carlo method in complex heterogeneous systems such as organs or tissues
in proton therapy. This interface program was developed under
MATLAB software and includes a friendly graphical user interface
with several tools such as image properties adjustment or results display. Quadtree decomposition technique was used as an image
segmentation algorithm to create optimum geometries from Computed Tomography (CT) images for dose calculations of proton
beam. The result of the mentioned technique is a number of nonoverlapped
squares with different sizes in every image. By this way
the resolution of image segmentation is high enough in and near
heterogeneous areas to preserve the precision of dose calculations
and is low enough in homogeneous areas to reduce the number of
cells directly. Furthermore a cell reduction algorithm can be used to combine neighboring cells with the same material. The validation of this method has been done in two ways; first, in comparison with experimental data obtained with 80 MeV proton beam in Cyclotron
and Radioisotope Center (CYRIC) in Tohoku University and second, in comparison with data based on polybinary tissue calibration method, performed in CYRIC. These results are presented in this paper. This program can read the output file of Monte Carlo code while region of interest is selected manually, and give a plot of dose distribution of proton beam superimposed onto the CT images.
Abstract: In this paper, a novel and fast algorithm for segmental
and subsegmental lung vessel segmentation is introduced using
Computed Tomography Angiography images. This process is quite
important especially at the detection of pulmonary embolism, lung
nodule, and interstitial lung disease. The applied method has been
realized at five steps. At the first step, lung segmentation is achieved.
At the second one, images are threshold and differences between the
images are detected. At the third one, left and right lungs are gathered
with the differences which are attained in the second step and Exact
Lung Image (ELI) is achieved. At the fourth one, image, which is
threshold for vessel, is gathered with the ELI. Lastly, identifying and
segmentation of segmental and subsegmental lung vessel have been
carried out thanks to image which is obtained in the fourth step. The
performance of the applied method is found quite well for
radiologists and it gives enough results to the surgeries medically.
Abstract: The aim of the present study is to analyze the generation of osteoporotic vertebral bone induced by lack of calcium during growth period and analyze its effects for disc degeneration, based on biomechanical and histomorphometrical study. Mechanical and histomorphological characteristics of lumbar vertebral bones and discs of rats with calcium free diet (CFD) were detected and tracked by using high resolution in-vivo micro-computed tomography (in-vivo micro-CT), finite element (FE) and histological analysis. Twenty female Sprague-Dawley rats (6 weeks old, approximate weight 170g) were randomly divided into two groups (CFD group: 10, NOR group: 10). The CFD group was maintained on a refmed calcium-controlled semisynthetic diet without added calcium, to induce osteoporosis. All lumbar (L 1-L6) were scanned by using in vivo micro-CT with 35i.un resolution at 0, 4, 8 weeks to track the effects of CFD on the generation of osteoporosis. The fmdings of the present study indicated that calcium insufficiency was the main factor in the generation of osteoporosis and it induced lumbar vertebral disc degeneration. This study is a valuable experiment to firstly evaluate osteoporotic vertebral bone and disc degeneration induced by lack of calcium during growth period from a biomechanical and histomorphometrical point of view.
Abstract: Advances in clinical medical imaging have brought about the routine production of vast numbers of medical images that need to be analyzed. As a result an enormous amount of computer vision research effort has been targeted at achieving automated medical image analysis. Computed Tomography (CT) is highly accurate for diagnosing liver tumors. This study aimed to evaluate the potential role of the wavelet and the neural network in the differential diagnosis of liver tumors in CT images. The tumors considered in this study are hepatocellular carcinoma, cholangio carcinoma, hemangeoma and hepatoadenoma. Each suspicious tumor region was automatically extracted from the CT abdominal images and the textural information obtained was used to train the Probabilistic Neural Network (PNN) to classify the tumors. Results obtained were evaluated with the help of radiologists. The system differentiates the tumor with relatively high accuracy and is therefore clinically useful.
Abstract: A 3D industrial computed tomography (CT)
manufactured based on a first generation CT systems, single-source
– single-detector, was evaluated. Operation accuracy assessment of
the manufactured system was achieved using simulation in
comparison with experimental tests. 137Cs and 60Co were used as a gamma source. Simulations were achieved using MCNP4C code.
Experimental tests of 137Cs were in good agreement with the simulations
Abstract: In the present study, changes of morphology and
mechanical characteristics in the lumbar vertebrae of the
ovariectomised (OVX) rat were investigated. In previous researches,
there were many studies about morphology like volume fraction and
trabecular thickness based on Micro - Computed Tomography (Micro
- CT). However, detecting and tracking long-term changes in the
trabecular bone of the lumbar vertebrae for the OVX rat were few. For
this study, one female Sprague-Dawley rat was used: an OVX rat. The
4th Lumbar of the OVX rat was subjected to in-vivo micro-CT.
Detecting and tracking long-term changes could be investigated in the
trabecular bone of the lumbar vertebrae for an OVX rat using in-vivo
micro-CT. An OVX rat was scanned at week 0 (just before surgery), at
week 4, at week 8, week 16, week 22 and week 56 after surgery. Finite
element (FE) analysis was used to investigate mechanical
characteristics of the lumbar vertebrae for an OVX rat. When the OVX
rat (at week 56) was compared with the OVX rat (at week 0), volume
fraction was decreased by 80% and effective modulus was decreased
by 75%.
Abstract: Rapid prototyping (RP) techniques are a group of
advanced manufacturing processes that can produce custom made
objects directly from computer data such as Computer Aided Design
(CAD), Computed Tomography (CT) and Magnetic Resonance
Imaging (MRI) data. Using RP fabrication techniques, constructs
with controllable and complex internal architecture with appropriate
mechanical properties can be achieved. One of the attractive and
promising utilization of RP techniques is related to tissue engineering
(TE) scaffold fabrication. Tissue engineering scaffold is a 3D
construction that acts as a template for tissue regeneration. Although
several conventional techniques such as solvent casting and gas
forming are utilized in scaffold fabrication; these processes show
poor interconnectivity and uncontrollable porosity of the produced
scaffolds. So, RP techniques become the best alternative fabrication
methods of TE scaffolds. This paper reviews the current state of the
art in the area of tissue engineering scaffolds fabrication using
advanced RP processes, as well as the current limitations and future
trends in scaffold fabrication RP techniques.
Abstract: CT assessment of postoperative spine is challenging in the presence of metal streak artifacts that could deteriorate the
quality of CT images. In this paper, we studied the influence of different acquisition parameters on the magnitude of metal streaking.
A water-bath phantom was constructed with metal insertion similar with postoperative spine assessment. The phantom was scanned with
different acquisition settings and acquired data were reconstructed
using various reconstruction settings. Standardized ROIs were defined within streaking region for image analysis. The result shows
increased kVp and mAs enhanced SNR values by reducing image
noise. Sharper kernel enhanced image quality compared to smooth
kernel, but produced more noise in the images with higher CT fluctuation. The noise between both kernels were significantly
different (P
Abstract: Automatic tube current modulation (ATCM) systems are available for all CT manufacturers and are used for the majority of patients. Understanding how the systems work and their influence on patient dose and image quality is important for CT users, in order to gain the most effective use of the systems. In the present study, a new phantom was used for evaluating dose distribution and image quality under the ATCM operation for the Toshiba Aquilion 64 CT scanner using different ATCM options and a fixed mAs technique. A routine chest, abdomen and pelvis (CAP) protocol was selected for study and Gafchromic film was used to measure entrance surface dose (ESD), peripheral dose and central axis dose in the phantom. The results show the dose reductions achievable with various ATCM options, in relation with the target noise. The doses and image noise distribution were more uniform when the ATCM system was implemented compared with the fixed mAs technique. The lower limit set for the tube current will affect the modulations especially for the lower dose option. This limit prevented the tube current being reduced further and therefore the lower dose ATCM setting resembled a fixed mAs technique. Selection of a lower tube current limit is likely to reduce doses for smaller patients in scans of chest and neck regions.
Abstract: Computed tomography (CT) dosimetry normally uses
an ionization chamber 100 mm long to estimate the computed
tomography dose index (CTDI), however some reports have already
indicated that small devices could replace the long ion chamber to
improve quality assurance procedures in CT dosimetry. This paper
presents a novel dosimetry system based in a commercial
phototransistor evaluated for CT dosimetry. Three detector
configurations were developed for this system: with a single, two and
four devices. Dose profile measurements were obtained with them
and their angular response were evaluated. The results showed that
the novel dosimetry system with the phototransistor could be an
alternative for CT dosimetry. It allows to obtain the CT dose profile
in details and also to estimate the CTDI in longer length than the
100 mm pencil chamber. The angular response showed that the one
device detector configuration is the most adequate among the three
configurations analyzed in this study.
Abstract: Quality of 2D and 3D cross-sectional images produce
by Computed Tomography primarily depend upon the degree of
precision of primary and secondary X-Ray intensity detection.
Traditional method of primary intensity detection is apt to errors.
Recently the X-Ray intensity measurement system along with smart
X-Ray sensors is developed by our group which is able to detect
primary X-Ray intensity unerringly. In this study a new smart X-Ray
sensor is developed using Light-to-Frequency converter TSL230
from Texas Instruments which has numerous advantages in terms of
noiseless data acquisition and transmission. TSL230 construction is
based on a silicon photodiode which converts incoming X-Ray
radiation into the proportional current signal. A current to frequency
converter is attached to this photodiode on a single monolithic CMOS
integrated circuit which provides proportional frequency count to
incoming current signal in the form of the pulse train. The frequency
count is delivered to the center of PICDEM FS USB board with
PIC18F4550 microcontroller mounted on it. With highly compact
electronic hardware, this Demo Board efficiently read the smart
sensor output data. The frequency output approaches overcome
nonlinear behavior of sensors with analog output thus un-attenuated
X-Ray intensities could be measured precisely and better
normalization could be acquired in order to attain high resolution.
Abstract: In this study, a new and fast algorithm for Ascending
Aorta (AscA) and Descending Aorta (DesA) segmentation is
presented using Computed Tomography Angiography images. This
process is quite important especially at the detection of aortic
plaques, aneurysms, calcification or stenosis. The applied method has
been carried out at four steps. At first step, lung segmentation is
achieved. At the second one, Mediastinum Region (MR) is detected
to use in the segmentation. At the third one, images have been
applied optimal threshold and components which are outside of the
MR were removed. Lastly, identifying and segmentation of AscA and
DesA have been carried out. The performance of the applied method
is found quite well for radiologists and it gives enough results to the
surgeries medically.