Catálogo de publicaciones - libros

Scattering of X-rays at small angles is dominated by coherent (elastic) scattering. These coherent scattering events interfere and produce diffraction effects. The latter gives rise to a unique scattering signature characteristic of the tissue that has been irradiated. In this study Energy Dispersive X-Ray Diffraction (EDXRD) is used for study of breast tumors. Work is in progress, but until this step it can be understood it is easy to differentiate between normal and tumoral breast tissues but there is a little difference between ductal lobular carcinoma and insitu ductal carcinoma. In next step in addition of these types of tumors, fibrocystic changes will be examined too.

Measurement of elastic modulus by water bag pressing is under development in our laboratories. Basic experiments were performed by pressing breast cancer phantom by water bag. The phantom is made of 10 weight percent gelatin of the thickness of 40mm, in which Plexiglas cylinder of the diameter of 10mm, mimicking the cancer, was placed in 10mm and 20mm depth from each surface. Phantoms was placed on the desk and pressed by a balloon filled with water with the pressure. The height of the vessel of water was adjusted to change the pressure in the balloon. Deformation of the phantom was detected by ultrasound echo technique. Ultrasound frequency was 11MHz. The gelatin phantom (density of 1.03) was deformed around Plexiglas cylinder by water pressure of 1.1 to 2.4kPa. Apparent differences of gelatin surface deformation depending on different water pressure was confirmed from echogram thus obtained. The experimental results were simulated by computer using Finite Element Method (ANSYS 9.0) to confirm the experimental findings. The elastic modulus of gelatin phantom was compared to computer simulation using Finite Element Method (ANSYS 9.0) assuming Poisson ratio of gelatin of 0.49 and/or 0.45 to give the elastic modulus of gelatin to be 6kPa to 9kPa The apparent difference of elastic modulus seems to be due to stretching force of rubber of balloon containing water. Computer simulation by Finite Element Method were achieved for future experiments, showing simpler geometry is beneficial.

It is well-known that cancerous cells on mastectomy specimens represent glandular tissue, where it originated. This study was undertaken to develop a double-exposure dual energy subtraction microradiography technique and validate it by using a phantom study. The technique is used to quantify glandular component on the mastectomy specimen. This double-exposure dual energy subtraction microradiography technique had been developed using soft energy X-ray in conjunction with computed radiography. The technique involves exposing the phantom at low (15 kV) and high (20 kV; 0.1 mm tin added filtration), image registration, subtraction and image analysis. The phantom is designed to contain 100% glandular embedded in 100% adipose tissue equivalent materials. The subtracted phantom image was analyzed. The radiologist then analyzed five mastectomy specimens using manual delineation and computer techniques respectively. The technique is able to detect glandular tissue when in excess of 49.1% of the material. The resulting fibroglandular tissue area is 90.3% in agreement with the corresponding manually delineated technique used by the radiologist. We had developed a technique to quantify glandular component of the mastectomy specimen and validate its using a phantom study. The technique reported here in combination with histological examination of sliced mastectomy specimen s will enable us to ascertain that radiologically screened lesions have been effectively and totally cut out and extensively evaluated histologically.

A novel image reconstruction technique, which avoids aliasing artifacts by scalable image reconstruction in magnetic resonance imaging, is proposed. The signal obtained in the phase-scrambling Fourier imaging technique can be transformed to the signal described in the Fresnel transform equation of the objects. Therefore, image reconstruction can be performed not only by inverse Fourier transform but also by inverse Fresnel transform. Image reconstruction by inverse Fresnel transform allows optional scaling of images Thus, alias-free images can be reconstructed even from signals that produce serious aliasing artifacts by standard inverse Fourier transform reconstruction.

Low Back Pain is one of the most frequent medical problems in the western world and its consequent cost is enormous. Research has indicated that low back pain is often related to mechanical disorders of the spinal or holding elements. The study of lumbar spine motion could be helpful in diagnosis of low back pain. Low-dose Digital Videofluoroscopy (DVF) is currently the only practical medical imaging technique to obtain motion images of the lumbar spine. However, due to low dosage, DVF images suffer from the presence of noise, poor contrast and adjacent structures near the vertebrae.

Development of a suitable edge detector is the first step of characterization of the lumbar spine motion. Recently many wavelet-based approaches have been applied in edge detection to acquire multi-scale gradient images. This paper discusses a wavelet-based, scale multiplication, edge detection method which works well with the DVF images. Experimental results are presented to illustrate the potential of this approach. With the edge information, the movement of the lumbar spine can be tracked and the biomechanical factors can be studied.

Methodology for performing constancy test of X-Ray radiography devices with CR Systems are presented. The problems, results and parameters are discussed in this paper. Tools existing before digitalization were employed as test tools even for these studies. The tests are included in quality assurance manual (QAM) of Na Homolce Hospital.

The pulsatile motion artifacts in the radial spin-echo diffusion-weighted-imaging (rSE-DWI) are analyzed and a method to improve the image quality of the rSE-DWI using the projection data regeneration method is proposed in this work. In general, ECG-triggering is used together with the rSE-DWI in order to prevent the loss of projection data, where the amount of loss depends on the data acquisition timing in the cardiac cycle. The ECG-triggering reduces the artifacts related to the cardiac pulse to some extent, but still leaves some degraded projection data while increasing the data acquisition time. Thus, the projection data regeneration method is proposed in order to improve the image quality. In the proposed method, the projection data is acquired by the rSE-DWI from which a temporary image is generated by an inverse Radon transform (IRT). The projection data acquired at each view angle is tested to figure out whether it is damaged by the pulsatile motion, and then the degraded data are replaced with the data that are regenerated by the Radon transform (RT) of the temporary image. The regeneration process is repeated until the image gains reasonable quality. In the meanwhile, the thermal noise of the signal is removed using the mask generated by thresholding the intensity of the projection data. In order to demonstrate the efficiency, the proposed method for the improvement of image quality is applied to a phantom and images. The quality of the DW images acquired by either ECG-triggered or non-triggered rSE-DWI can be improved using the proposed method without increasing the imaging time.

In this paper, we investigated the imaging characteristic of Eu^3+-doped Gd_2O_3 nano phosphor for high resolution digital x-ray imaging system. The Gd_2O_3:Eu^3+ nano particles were synthesized using a low temperature solution-combustion method and then sintered at 900 °C. From the XRD and FE-SEM analysis, the x-ray peaks corresponding to the cubic phase of <222>, <400>, <440>, <622> with monoclinic phase and the average diameter of the particle was determined to be about 10~40 nm. The PL spectrum measurement shows the fabricated Gd_2O_3:Eu^3+ nano particles, the emission peaks correspond to transition from the excited ^5D_0 level to ^7F_J (J=0,1,2,3) level of the ^4F_6 configuration of the Eu^3+ ion and a commercial bulk phosphor’s and the strong peak exhibits at 611 nm. The evaluation of the imaging performance was performed by determining the Modulation Transfer Function (MTF), Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE). Determined MTF was 70 % at 3 lp/mm and DQE (0) was 37 %. These results means that Gd_2O_3:Eu^3+ nano phosphor may be appropriate for low-dose and high resolution digital x-ray imaging system.

A microfocus x-ray tube is useful in order to perform magnification digital radiography. The 100-µm-focus x-ray generator consists of a main controller for regulating the tube voltage and current and a tube unit with a high-voltage circuit and a fixed anode x-ray tube. The maximum tube voltage, current, and electric power were 105 kV, 0.5 mA, and 50 W, respectively. Using a 50-µm-thick tungsten filter, the x-ray intensity was 34.0 µGy/s at 1.0 m from the source with a tube voltage of 100 kV and a current of 0.50 mA. Since K-series characteristic x-rays from tungsten targets are absorbed effectively by gadolinium-based contrast media, these x-rays are very useful to perform enhanced angiography. Magnification angiography was performed by two-time magnification imaging with a computed radiography system. In angiography of non-living animals, we observed fine blood vessels of approximately 100 µm with high contrasts.

Software-based ultrasound imaging using commercial DSPs can offer various advantages compared to the conventional FPGA or ASIC based approach. However, it requires multiple DSPs to achieve the real time requirement of medical ultrasound imaging. In this paper, we present a multi-DSP system composed of six ADSP-TS201 DSPs connected with a crossbar switch network. Through efficient task grouping, scheduling, and data flow control, the echo processing function was implemented to support high PRF up to 2.5kHz without code optimization.