Biomedical subjects

K Hyodo

Publications and source records attributed to K Hyodo.

At least 19 recordsLinked to original sources

PubMed2002

Application of synchrotron X-ray imaging to phase objects in orthopedics.

Novel imaging of the fine structures of the ribs of a pig and a specimen of human osteosarcoma utilizing the spatial coherence of X-rays was successfully performed with an incident X-ray energy of 30 keV at SPring-8, Japan. The image contrast appearing at the periphery of trabecular bone, small calcifications and small fractures is caused by the phase shift of the X-rays at the boundary of these objects that have different X-ray refractive indices. The image is recorded on mammography film without an intensifying screen. Comparison of the image contrast using different sample-to-film distances, Z, such as Z = 5 m and Z approximately 0 m, showed that the former images were always more informative, i.e. better in resolution and/or image contrast when imaging trabecular bone, bone marrow and small fractures in compact bone, and for imaging cartilage. Radiography using synchrotron X-rays for phase objects should be a powerful tool for diagnosis in orthopedics, especially for bone disease.

Animals↗

PubMed2001

Preliminary experiment of fluorescent X-ray computed tomography to detect dual agents for biological study.

The simultaneous observation of various information, such as blood flow, tissue metabolism and distribution of receptors, is quite important in order to understand the functional state of biomedical objects. The simultaneous detectability of contrast agents by fluorescent X-ray computed tomography (FXCT) with synchrotron radiation is examined in this study. The system consisted of a silicon (111) double-crystal monochromator, an X-ray slit system, a scanning table, a PIN diode, a highly purified germanium detector and an X-ray charge-coupled device (CCD) camera. The monochromatic X-ray beam energy was adjusted to 37.0 keV and collimated into a pencil beam of 1 x 1 mm. The fluorescent spectra of the K alpha lines for iodine and xenon were detected simultaneously. FXCT could image the distribution of both iodine and xenon agents in a phantom clearly and the contrast ratio was significantly better than that of transmission X-ray computed tomography images.

Fluorescence↗

PubMed2001

Morphology, fluorescence properties, and their photothermal changes of poly(substituted thiophene) films revealed by near-field fluorescence microspectroscopy.

The morphology and fluorescence spectrum of poly(3-[2-(N-dodecylcarbamoyloxy)ethyl]thiophene-2,5-diyl) film were examined with spatial resolution of 100 nm using near-field fluorescence microspectroscopy. Fluorescence spectra observed at protruding domains were blue-shifted compared with flat areas, and further blue-shift was observed there more appreciably by long-time irradiation via a near-field scanning optical microscope probe. It is considered that the polymer chains at the protruding domains take disordered conformations, in which conjugated lengths are shorter and further disordering can be induced more easily by irradiation compared with those in the flat areas.

Journal Article↗

PubMed2001

Design of synchrotron light source and its beamline dedicated to dual-energy x-ray computed tomography.

A synchrotron light source dedicated to medical applications has been designed at National Institute of Radiological Sciences. The storage ring, with circumference of 80 m, is designed for acceleration of 2.3 GeV and a stored current of 420 mA. It is equipped with two multipole wigglers to produce sufficient photon flux in a hard x-ray region required for medical applications. The purposes of the synchrotron light source are clinical performance of medical diagnoses clinically and research and development relating with medical applications. One of the most interesting applications for us is dual-energy x-ray computed tomography (CT). It gives the information about electron density of human tissue. The information plays an important role in advancing heavy-ion radiotherapy of cancers. Electron density can be derived from attenuation coefficients measured by different energy x rays. In this paper, a practical method of the dual-energy x-ray CT with synchrotron radiation is proposed with the theoretical consideration. The primitive experiment using monochromatic x rays emitted from radioisotopes proved the procedure of analysis mentioned here effective to derive electron densities from linear attenuation coefficients for two x rays of a different energy. The beamline dedicated to dual-energy x-ray CT is also proposed. It has a multipole wiggler as a light source and it mainly consists of a dual crystal monochromator and a rotating filter for attenuating photon flux of x rays and two-dimensional detector.

Equipment Design↗

PubMed2001

Comparison of in-phantom dose distributions for coronary angiography using an x-ray machine and synchrotron radiation.

Coronary cineangiography using synchrotron radiation is anticipated, owing to the high intensity and availability of monoenergy. To investigate allowable dose levels in clinical application, absorbed dose distribution in a tissue substitute phantom for a conventional x-ray machine was measured with thermoluminescent dosimeters at the University of Tsukuba under the practical conditions used for digital angiography. The dose rate at a 0.5-cm depth was 0.145 Gy/s, and the dose per frame was 0.725 mGy for the irradiation period of 5 ms per frame. For synchrotron radiation, the dose distribution measurement was made at a 5-GeV AR (Accumulation Ring) of the High Energy Accelerator Research Organization, in which a polymethylmethacrylate (PMMA) phantom was irradiated with the strongest beam available at the facility, which was 33.32 keV, 5.2 x 6.2 cm2 beam. Using this beam, a 1-mm-diameter coronary artery has been visualized at 1% iodine concentration at the AR. Nonhomogeneous strength distribution in the beam was observed in the vertical direction. The maximum dose rate was 0.556 Gy/s, and it attenuated to 1/3000 at a 30-cm depth in the beam center. At the deep positions, the doses were influenced by the high harmonics, which was confirmed with an EGS4 Monte Carlo calculation. Outside the beam, beam contamination on both sides of the main beam affected the doses. For comparison to the x-ray machine, the measured dose was analytically converted to that needed for a 5.2 x 16 cm2 beam that is used for clinical application. The dose rate at 0.5-cm depth was found to be 0.215 Gy/s, which is 1.48 times larger than that for x-rays. Moreover, the attenuation rate in the phantom was significantly greater than that of the x-ray machine, because of the difference of the energy spectra between the x-rays and synchrotron radiation used.

Biophysical Phenomena↗

PubMed2001

[Clinical laboratory data and reference intervals standardized in Fukuoka].

In Fukuoka whose population is approximately five million inhabitants, surveys on the accuracy of laboratory data have been performed by the Fukuoka Prefecture Medical Association for the last 30 years. We have been attempting to evaluate the data for routine use since 1988, and it has become possible to share laboratory data between all institutions in Fukuoka prefectures. As a result, reference intervals for 23 clinical chemistry analytes were established in 1995, to which were added in 1996 five serum protein constituents that have been utilized for clinical examinations. Methods for documentations and monitorings the data obtained in the prefecture were also established, standardization of the above analytes extended to 97% of the institutions in the prefecture. Results for 14 of the 23 clinical chemistry analytes have become highly reliable and clinically useful as differences between institutions in terms of results have narrowed. Standardization of other analytes is now in progress.

Aged↗

PubMed2000

High-resolution imaging of coronary calcifications by intense low-energy fluoroscopic X-ray obtained from synchrotron radiation.

PURPOSE: To obtain an intense monochromatic low-energy X-ray from synchrotron radiation (SR) and apply it to detect coronary calcifications. METHODS AND RESULTS: The SR beam was reflected with a silicon crystal to be expanded (150 mm in height and 80 mm in width) and to be monochromatized at an energy level of 37 keV. The X-ray was intermittently irradiated to obtain dynamic imaging of 30 images/s. Images were recorded by a digital fluorography system. The low-energy X-ray from SR sharply visualized calcification of coronary arteries, while conventional X-ray could not visualize coronary calcification. CONCLUSION: The intense monochromatic low-energy X-ray from SR is sensitive, has high-resolution for imaging coronary calcification and may serve as a screening method for coronary artery disease.

Calcinosis↗

PubMed1999

Synchrotron microangiography reveals configurational changes and to-and-fro flow in intramyocardial vessels.

In 8 dogs, in situ microangiography using synchrotron radiation visualized penetrating transmural arteries (PTAs) with a diameter of >60 micrometers and allowed quantitation of vessel diameters of >140 micrometers. Myocardial contraction reduced the vascular short-axial diameters to 87 +/- 17% (n = 62, P < 0.001, paired t-test) of the end-diastolic values and increased the longitudinal dimension to 129 +/- 5% (n = 45, P < 0.001). The diameter reduction in the subendocardial PTA segments was significantly more marked than that in the subepicardial PTA segments (60 +/- 12 vs. 88 +/- 12%, n=13, P < 0.001, paired t-test). Intracoronary administration of dobutamine (0.1 micrograms. kg-1. min-1) increased, and in contrast, partial clamping of the coronary artery (ischemia) decreased, the configurational changes. To-and-fro blood flow was clearly observed in PTAs with visual identification of capacitive backflow, resistive forward flow during ischemia on coronary arteriography, and even under baseline conditions in coronary venography. Thus this method advances our understanding of mechanical influences on the coronary circulation.

Animals↗

PubMed1999

Branching patterns of intramural coronary vessels determined by microangiography using synchrotron radiation.

The intramural coronary artery (IMCA) with a diameter of 50-500 micrometers is critical for blood supply to the inner layers of heart muscle. We introduced digital measurement to microangiography using monochromatic synchrotron radiation and quantified branching patterns of the IMCA, the epicardial coronary artery (EPCA), and the distal ileal artery (DIA). The pre- and postbranching diameters were measured (95-1,275 micrometers) in seven dogs. A typical arterial segment divided into two nearly equivalent branches, and a regression line of daughter-to-mother diameter plots was almost identical among the EPCA (y = 0.838x - 16.7 in micrometers), IMCA (y = 0.737x - 2.18), and DIA (y = 0.755x + 8.63). However, a considerable difference was present at a segment where a proximal IMCA branched off from an EPCA (y = 0.182x + 90.2). Moreover, a proximal IMCA diameter had no relationship to the branching order from an EPCA. The precision of this method was confirmed by the good correlation of diameter measurements between two independent observers (r = 0.999, y = 1.02x - 1.07). In conclusion, using digital microangiography we demonstrated that the self-similar branching pattern of coronary arteries was discrete at the connection between the IMCA and EPCA.

Angiography↗

PubMed1999

Dynamic intravenous coronary angiography using 2D monochromatic synchrotron radiation.

A method of examination for coronary artery disease that is less invasive and easier than coronary angiography (CAG) has been sought. We have developed a dynamic intravenous coronary angiography (IVCAG) system using synchrotron radiation (SR) and have used it clinically. Four patients suspected of having angina pectoris underwent IVCAG. An SR beam was reflected asymmetrically with a silicon crystal to produce a wide (150 mm x 80 mm) and monochromatic (37 keV) X-ray beam, with an energy level to achieve high sensitivity to the contrast agent. Following an intravenous injection of contrast agent, irradiation was applied for 4 ms periods at 33 ms intervals for dynamic IVCAG at 30 images s-1. Images were acquired with an image intensifier and recorded with a digital fluorography system. The dynamic images permitted clear visualization of the coronary arteries and permitted evaluation of coronary anatomy. Two patients exhibited no stenotic lesions, one patient had a 90% stenosis in the right coronary artery, and the remaining patient had a 25% stenosis at the site of previous percutaneous transluminal coronary angioplasty in the left anterior descending artery (LAD). The total irradiation doses used for IVCAG were less than those for conventional angiography. Dynamic IVCAG can be readily used for the evaluation of coronary arteries.

Aged↗

PubMed1999

[A study of mental and physical reactions after the Hanshin-Awaji Earthquake: mental and physical conditions of female undergraduate students immediately after, 2 months after, and 9 months after the earthquake].

This study assessed how time brings out changes in one's mental and physical reactions to traumatic experiences. Two surveys were conducted on students of Kobe College, located at one of the areas hardest hit by the Hanshin-Awaji Earthquake in January, 1995. Much of the traumatic reactions decreased in strength through January to March, while feelings of survival guilt did not. Guilt feelings of those whose housing were destroyed increased in March, and kept its level even in October. Although general health conditions of those surveyed in October was normal, several post-traumatic reactions increased in October as compared with March. The rate of recovery from post-traumatic reactions seemed to very according to the depth of one's psychological suffering, to one's financial situation, and to the presence of social support. The factor analysis on the items of mental and physical reactions yielded seven factors. The factor of highest eigenvalue in January was one named "anxiety about after-quake tremors", however, this was replaced by one named "emotional confusions" in March.

Data Collection↗

PubMed1999

Digitized cerebral synchrotron radiation angiography: quantitative evaluation of the canine circle of Willis and its large and small branches.

BACKGROUND AND PURPOSE: Conventional X-ray angiography lacks the sensitivity and spatial resolution needed to detect small amounts of iodinated contrast material and to quantitate diameters of the small vessels in the brain. The purpose of this study was to ascertain whether digitized synchrotron radiation microangiography, with the use of a high-definition TV camera system, can accurately show small cerebral vessels. METHODS: Six anesthetized dogs were exposed to monochromatic synchrotron radiation with an energy level of 33.3 keV optimized for iodine detection while iodinated contrast material was injected into the brachiocephalic and vertebral arteries. The images were detected with a high-definition TV camera system with a spatial resolution of 30 microm. In all, 26 cerebral angiograms of the circle of Willis with its branches were obtained, and the images were digitized at a workstation. RESULTS: The small branches of the circle of Willis were clearly visible on all images. Vasodilatation of the circle of Willis and its large and small branches induced by CO2 inhalation was quantitatively confirmed on the images: for example, the diameter of one small branch was increased from 0.24 +/- 0.04 mm to 0.38 +/- 0.12 mm. Temporal subtraction improved the image quality. CONCLUSION: The synchrotron radiation angiographic system is useful for visualizing large and small vessels deep in the brain as well as for quantitating their diameters.

Angiography, Digital Subtraction↗

PubMed1998

Dose response of various radiation detectors to synchrotron radiation.

Accurate dosimetry is particularly difficult for low- to medium-energy x-rays as various interaction processes with different dependences on material properties determine the dose distribution in tissue and radiation detectors. Monoenergetic x-rays from synchrotron radiation offer the unique opportunity to study the dose response variation with photon energy of radiation detectors without the compounding effect of the spectral distribution of x-rays from conventional sources. The variation of dose response with photon energies between 10 and 99.6 keV was studied for two TLD materials (LiF:Mg,Ti and LiF:Mg,Cu,P), MOSFET semiconductors, radiographic and radiochromic film. The dose response at synchrotron radiation energies was compared with the one for several superficial/orthovoltage radiation qualities (HVL 1.4 mm Al to 4 mm Cu) and megavoltage photons from a medical linear accelerator. A calibrated parallel plate ionization chamber was taken as the reference dosimeter. The variation of response with x-ray energy was modelled using a two-component model that allows determination of the energy for maximum response as well as its magnitude. MOSFET detectors and the radiographic film were found to overrespond to low-energy x-rays by up to a factor of 7 and 12 respectively, while the radiochromic film underestimated the dose by approximately a factor of 2 at 24 keV. The TLDs showed a slight overresponse with LiF:Mg, Cu, P demonstrating better tissue equivalence than LiF:Mg, Ti (maximum deviation from water less than 25%). The results of the present study demonstrate the usefulness of monoenergetic photons for the study of the energy response of radiation detectors. The variations in energy response observed for the MOSFET detectors and GAF chromic film emphasize the need for a correction for individual dosimeters if accurate dosimetry of low- to medium-energy x-rays is attempted.

Biophysical Phenomena↗

PubMed1997

Use of synchrotron radiation microangiography to assess development of small collateral arteries in a rat model of hindlimb ischemia.

BACKGROUND: Current methods of angiography cannot provide images of arteries measuring < 200 microns in diameter. We have recently developed a new angiography system that uses monochromatic synchrotron radiation and a high-definition video system with a spatial resolution of 30 microns. In the present study, we applied this microangiography system to visualize small arteries in normal and ischemic rat limbs and investigated the development of collateral arteries. METHODS AND RESULTS: Microangiography was performed in the normal and the ischemic limb 4 weeks after the excision of the femoral artery. In the normal limb, up to the fourth branches of the iliac and/or femoral arteries (diameter < 100 microns) were readily identified. Some of these branches were found to perfuse the distal thigh area. In the ischemic limb, an extensive structural remodeling of the vascular network was observed. Numerous small arteries had developed from the branches of the iliac artery to constitute a fine arterial network, the so-called "midzone," which was composed of linear, normal appearing arteries and those with an undulating, unbranched appearance. CONCLUSIONS: The small collateral artery network was angiographically visualized with a resolution limit < 100 microns. The linear collaterals appeared to result from an opening of preexisting vessels. The undulating, unbranched vessels were not observed in the normal limbs and seemed to be vessels that were newly formed after limb ischemia. Synchrotron radiation microangiography appears to be a powerful means of assessing the development of small collateral arteries, which may help to provide a basis for understanding of the collateral circulation.

Angiography↗

PubMed1997

Dynamic intravenous coronary arteriography using synchrotron radiation and its application to the measurement of coronary blood flow.

We have developed dynamic intravenous coronary arteriography (IVCAG) using a monochromatic (33.3 keV), 2-dimensional X-ray beam (70 x 70 mm) generated from synchrotron radiation. To investigate its use to visualize the coronary arteries and to estimate coronary blood flow, we performed IVCAG in 10 dogs and 1 goat. The animals were irradiated with the synchrotron beam after intravenous injection of a contrast agent, and images were obtained using a TV camera and videorecorder. In the dogs, blood flow in the left anterior descending coronary artery (LAD) was also estimated from the images by applying a transit-time analysis. We obtained dynamic IVCAG images in the dogs and goat and could visualize even a deliberately created coronary stenosis about 1 mm in length. In addition, coronary blood flow could be estimated with an acceptable degree of accuracy. LAD flow calculated from IVCAG was 14.7 +/- 5.1 ml/min, whereas measured LAD flow was 16.6 +/- 4.8 ml/min. There was a close correlation between the estimated and measured LAD flows (r = 0.90, p < 0.01). Thus, dynamic IVCAG is minimally invasive, permits the simultaneous evaluation of coronary anatomy and blood flow, and may be feasible for clinical application.

Animals↗

PubMed1996

Retropharyngeal abscess after radiation therapy and cis-platinum, 5-fluorouracil treatment for nasopharyngeal carcinoma with collagen disease: report of two patients and a review of the literature.

Collagen disease are frequently associated with malignant tumors. Recently, radiotherapy combined with chemotherapy has been recommended for improving the efficacy of treatment for nasopharyngeal carcinoma. Two patients with nasopharyngeal carcinoma complicated by collagen diseases (dermatomyositis in one, and Sjögren's syndrome with mixed connective tissue disease in the other) were given radiotherapy combined with chemotherapy consisting of cis-platinum and 5-fluorouracil. Following this combination therapy, both patients developed retropharyngeal abscess and ulceration of the mucosal membrane on the posterior wall of the oropharynx; there was no tumor cell involvement. Because these injuries were more severe than would have been expected from radiotherapy alone, it is recommended that special attention be paid to combination therapy in patients with nasopharyngeal carcinoma complicated by collagen disease.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1996

Small-vessel radiography in situ with monochromatic synchrotron radiation.

PURPOSE: To evaluate the usefulness of a radiographic system with monochromatic synchrotron radiation to depict small vessels and peripheral secretory ducts. MATERIALS AND METHODS: Radiography of various organs was tested in 14 anesthetized dogs and pancreatography was performed in an excised human pancreas by using the following system: monochromatic synchrotron radiation with an energy level just above the k absorption edge of iodine as an x-ray source and a high-definition TV system with a high-light-sensitivity image pick-up tube camera coupled with a fluorescent screen as a detector. RESULTS: This system allowed depiction of small vessels (diameter < 50-100 microns) of the heart (penetrating transmural artery), brain (perforating arteries that arise directly in the circle of Willis), and intestinal organs (vasa recta and their submucosal communications) and of small branches (down to the fifth order) of the pancreatic duct. CONCLUSION: The synchrotron radiation system may be useful for evaluating microcirculatory disorders and early-stage malignant tumors in various human organs.

Adult↗

PubMed1996

Synchrotron radiation in the study of the variation of dose response in thermoluminescence dosimeters with radiation energy.

Thermoluminescence dosimetry (TLD) is a versatile technique with many applications for dosimetry of ionising radiation. However, in the range of kilovoltage x-rays which is widely used for diagnostic and therapeutic medical applications, problems arise from the differing dose response of most TL dosimeters with the radiation energy. The dose response of various TL detector types was investigated in mono-energetic x-ray beams of 26.8, 33.2, 40, 80.4 and 99.6keV from a synchrotron radiation source at the National Laboratory for High Energy Physics in Japan. This response was studied as a function of TL material (LiF:Mg,Ti, LiF:Mg,Cu,P and Al2O3), the detector geometry and size, and their thermal history. Due to the asymmetric diffraction from a Si crystal employed to produce monoenergetic photons there was more than 50% dose inhomogeneity in some of radiation fields used. Therefore, the different TL dosimeter types were rotated around and the results related to the reading of a set of "standard" LiF:Mg,Ti ribbons which were included in all experiments as reference detectors. No significant influence of the detector shape (physical size, thickness) on the dose response with energy could be found. However, the pre-irradiation thermal history influences the dose response with radiation energy: a fast cool down of LiF:Mg,Ti after a high temperature anneal will increase the sensitivity by more than a factor of two. The relatively new TLD material LiF:Mg,Cu,P (GR-200, obtained from Solid Dosimeter & Detector Laboratories, Beijing) was found to be approximately 100 times more sensitive than the standard LiF:Mg,Ti. In addition it proved to be more tissue equivalent for photon radiation between 27keV and 40keV. The performance of LiF:Mg,Cu,P makes it a very interesting TL material deserving further evaluation for applications in diagnostic and therapeutic x-rays.

Aluminum Oxide↗