In order to evaluate cytotoxic effects of secondary Auger electron emission(Photon Activation Therapy:PAT)
from alginate-coated iron nanoparticles(Alg-SNP), Alg-SNP-uptaken C6 glioma cell lines were irradiated with 6.89/7.2
Kev synchrotron X-ray. 0-125 Gy were irradiated on three experimental groups including No-SNP group incubating
without SNP as control group, 6hr-SNP group incubating with SNP for 6hr and ON-SNP group incubating with SNP
overnight. Irradiated cells were stained with Acridine Orange(AO) and Edithium Bromide(EB) to count their viability
with fluorescent microscopy in comparison with control groups. AO stained in damaged DNA, giving FL color change in
X-ray plus SNP group. EB did not or less enter inside the cell nucleus of control group. In contrast, EB entered inside the
cell nucleus of Alg-SNP group which means more damage compared with Control groups. The results of MTT assay
demonstrated a X-ray dose-dependent reduction generally in cell viability in the experimental groups. 3 or 9 times
increase in cell survival loss rate was observed at 6hr-SNP and ON-SNP groups, respectively compared to No-SNP
control group in first experiment that was done to test cell survival rate at relatively lower dose, from 0 to 50 Gy. In
second experiment X-ray dose was increased to 125 Gy. Survival loss was sharply decreased in a relatively lower dose
from 5 to 25 Gy, and then demonstrated an exponentially decreasing behavior with a convergence until 125 Gy for each
group. This observation suggests PAT effects on the cell directly by X-ray in the presence of Alg-SNP occurs within
lower X-ray dose, and conventional X-ray radiation effect becomes dominant in higher X-ray dose. The cell viability
loss of ON-SNP group was three times higher compared with that of 6hr-SNP group. In conclusion, it is possible to
design photodynamic X-ray therapy study using a monochromatic x-ray energy and metal nanoparticle as x-ray sensitizer,
which may enable new X-ray PDT to disseminated tumors without side effects to normal surrounding tissue.
We have developed X-ray refraction based computed tomography (CT) which is able to visualize soft tissue in
between hard tissue. The experimental system consists of Si(220) diffraction double-crystals called the DEI (diffraction-enhanced
imaging) method, object locating in between them and a CCD camera to acquire data of 900 x-ray images.
The x-ray energy used was 17.5 keV. The algorithm used to reconstruct CT images has been invented by A.
Maksimenko et al.. We successfully visualized calcification and distribution of breast cancer nest which are the inner
structure. It has much higher contrast which in comparison with the conventional absorption based CT system.
In recent years, the X-ray refraction contrast was widely developed and applied in different fields of science which deal with the nondestructive observation methods. As it follows from the name, the refraction contrast is the distribution of the X-ray intensity dependent on the deflection angle of the X-ray beam. This property of the contrast provides certain advantages over other contrasts such as absorption and phase-shift. The refraction contrast can show tiny details of the inner structure which are invisible in other types of the X-ray imaging techniques. Another advantage of the X-ray refraction contrast is the sensitivity to the low Z materials. This property of the refraction contrast may be of great importance in the medical applications of the X-ray. The advantages provided by the refraction contrast allow one to expect the same advantages of the computed tomography (CT) from the refraction contrast. Therefore this report is dedicated to the realization of the refraction-based CT. It describes the theoretical background of the problem, experimental realization of the method and actual results of the reconstruction of the breast cancer sample. The experimental data were acquired using X-ray synchrotron source at Photon Factory (KEK, Japan). The energy of used in the experiment was 11.7keV. The spatial resolution of the reconstructed images is about 20 microns.
The excised rat kidney slices were investigated using the diffraction enhanced imaging (DEI) method under the different FWHM of the rocking curve with 33.7keV x-ray, for the first time. The narrower FWHM of the rocking curve is used in the DEI imaging, the finer structure of the sample can be clearly distinguished and more details can be seen in the DEI image. Tuning the rocking curve width between 1.7μrad and 0.31μrad was done with small loss of peak intensity using a Si (220) double-crystal analyzer. The reason related with the influence of the FWHM of the rocking curve to the contrast resolution of DEI method is discussed. For the thin sample, how small deflected angle can be distinguished determines how small difference of density can be distinguished in the DEI imaging.
X-ray dark-field imaging (DFI) due to refraction is under development with intension of its clinical application. In this system we have adopted an asymmetric-cut monochro-collimator (M) and an angular analyzer (A) of Si 440 diffraction at 35 keV of X-rays. By choosing an appropriate thickness T of A that satisfies the condition T = ΛN where Λ is the extinction distance and N integer the transmissivity in the region of |W| (angular parameter) < 1 should be theoretically almost zero and |W| > 1 should be approximately 70-80%. This has been experimentally proven. Under this condition the X-rays whose propagation direction may not change such as those receiving only absorption will not go into the forward diffraction direction after A but go into the diffraction direction, while the X-rays refracted by object may go into the forward diffraction direction after A. We have settled two targets of clinical views: soft tissues at joints and early check of breast cancer. A first clear image of articular cartilage of small joint was successfully obtained using a proximal interphalangeal joint that was amputated from a cadaver. Since larger view field is needed for clinical use the size of approximately 90 mm in square has been successfully achieved. Using this beam articular cartilage of knee and shoulder joints from the same cadaver have been successfully visualized. Further visibility test by the DFI is under way for a phantom of breast cancer, paraffin fixed sliced breast samples containing micro-calcification, tumor and excised breast tissue.
Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. Although various types of monochromatic x-ray CT systems using synchrotron radiation have been developed using a parallel x-ray beam for imaging of small samples with a high spatial resolution, imaging of large objects such as the human body have not been developed yet. We have developed a fan-beam monochromatic x-ray CT using fluorescent x-rays generated by irradiating metal targets by synchrotron radiation. A CdTe linear array detector of 512 mm sensitive width was used in the photon counting mode. We made phantom experiments using fluorescent x-rays ranging from 32 to 75 keV. Monochromatic x-ray CT images of a cylindrical lucite phantom filled with several contrast media have been obtained. Measured CT numbers are compared with linear attenuation coefficients, and they showed a good linearity over a wide range of contrast media concentrations.
We have developed a photon-counting 256ch CdTe line detector system for a monochromatic x-ray CT system using fluorescent x-rays generated by synchrotron radiation. The size of each detector element is 1.98 mm(w) X 1.98 mm(h) X 0.5 mm(t). Each element has two discriminators (an upper and a lower discriminator) and two 16-bit counters (an upper and a lower counter). Each discriminator rejects pulses having a pulse height lower than the chosen voltage limits. All pulses in between the upper and lower voltage limits were obtained by subtracting the upper counter value from the lower counter value. By changing the voltage limits, we can obtain an incident x-ray energy spectrum. Several energy spectra for the fluorescent x-ray and standard (gamma) -ray sources were measured by using this detector. The detector showed a sufficient energy resolution, and has been found to be suitable as a detector of monochromatic x-ray CT.
We, a user group for medical applications of the SPring-8, have proposed the introduction of white X-rays from insertion devices to BMIC (BioMedical Imaging Center) for clinical uses so that enough photon fluxes to a subject is guaranteed. The photon flux, depending on various monochromatizing methods, was compared at the surface of the subject 200 m from a light source.
In this paper, we describe a 3D computed tomography (3D CT) using monochromatic x-rays generated by synchrotron radiation, which performs a direct reconstruction of 3D volume image of an object from its cone-beam projections. For the develpment of 3D CT, scanning orbit of x-ray source to obtain complete 3D information about an object and corresponding 3D image reconstruction algorithm are considered. Computer simulation studies demonstrate the validities of proposed scanning method and reconstruction algorithm. A prototype experimental system of 3D CT was constructed. Basic phantom examinations and specific material CT image by energy subtraction obtained in this experimental system are shown.