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Biomedical subjects

K Doi

Publications and source records attributed to K Doi.

At least 739 records · Page 41Linked to original sources
PubMed1984

Morphology of pancreatic tissue-containing accessory spleen in an APA hamster.

Accessory spleen (AS) was observed in 19 out of 71 (27%) golden hamsters of APA strain autopsied in the Institute of Physical and Chemical Research. When these AS were examined histologically, clusters of pancreatic tissues, such as islets and acini, were detected in the parenchyma of one AS located in the tail of pancreas of a 15-week-old male animal. This heterotopic pancreatic tissue was considered to penetrate deep into the AS from the pancreas through the adhesion site without any connective tissue border during the ontogenesis.

Age Factors↗
PubMed1984

Enzyme immunoassay of free thyroxin in serum.

We describe a double-antibody enzyme immunoassay for free thyroxin (FT4) in serum with use of beta-D-galactosidase conjugated to thyroxin. The method is uninfluenced by thyroxin-binding globulin or albumin. Values for FT4 so determined correlated well with those determined by radioimmunoassay (r = 0.98) and equilibrium dialysis (r = 0.89). The mean variability (CV) within and between assays was 7.4% and 7.6%, respectively. The measurable range of FT4 in serum was 2.8 to 109 ng/L. The FT4 concentrations in serum as determined by this method were 8.4 to 15.5 ng/L for 26 normal adult subjects; 26 to greater than 109 ng/L for 10 patients with hyperthyroidism; less than 2.8 to 8.0 ng/L for seven patients with hypothyroidism; 7.3 to 15.8 ng/L for eight pregnant women; and 12.2 and 13.5 ng/L for two patients with low concentrations of thyroxin-binding globulin.

Adult↗
PubMed1984

Investigation of energy responses of germanium detectors and correction of measured spectra by means of Monte Carlo simulation.

A Monte Carlo program was developed which determines the energy response of X-ray detectors of various "nested" sizes simultaneously. Twenty-one planar germanium detectors with cylindrical crystals were chosen, which are commercially available for X-ray spectrometry. The photopeak efficiency, K alpha and K beta escape fractions. Compton fraction, elastic fraction, penetration fraction, and the Compton continuum were tabulated as a function of incident X-ray energies from 12 to 300 keV in 2-keV increments. Coefficients of polynomials fitted to the Compton continua were also calculated to facilitate computer implementation of spectrum corrections. Spectrum correction methods which use the Compton continua determined by Monte Carlo calculation were compared with those approximated by rectangles. Comparison of the residual root-mean-square (RRMS) values between the incident and corrected spectra showed that the former method yielded lower RRMS values. However, the differences in these values are small, indicating that the simple rectangular approximation may be adequate for most spectral measurements.

Germanium↗
PubMed1984

[An autopsy case of membranous lipodystrophy (Nasu)].

Membranous lipodystrophy (Nasu) is characterized by polycystic osteodysplasia associated with dementia. We recently experienced a 9th autopsy case in Japan. This 50 year-old male, eldest in the reported autopsied case in Japan, presented bone fracture at 35 year of age and dementia started at 45. His parents were cousins. His sister, died with carcinoma of the bladder at 35, developed marked osteoporosis with multiple pathological fractures and "membrano-cystic" lesions were found in her adipose tissue. The roentgenogram of the patient's long bone revealed radiolucent and cystic areas with irregular boundaries at the metaphyses. Computer tomography of the brain examined during the last 3 years showed slowly progressive brain atrophy. Calcifications of the basal ganglia or low density area in the white matter were not found. Autopsy showed typical "membrano-cystic" lesions in the adipose tissue of the whole body including bone marrow. Brain weighed 1,030 g. There was a mild convolutional atrophy at the frontal lobe. White matter was diffusely atrophic. Demyelination was limited to the frontal lobe, where only small number of perivascular sudanophilic lipid-laden macrophages were found. Fibrillary astrocytes were rather diffusely proliferated, consistent with sclerosing leukoencephalopathy. Many spheroids were found in the frontal and occipital deep white matters, and external capsule. Ultrastructural study of spheroid revealed increased amount of neurofilament, vesicles with free patchy dense materials and degenerated mitochondria, which were consistent with primary axonal degeneration.

Adipose Tissue↗
PubMed1983

[Experimental study on diabetes and pregnancy: with special reference to the effects of insulin treatment on fetuses of diabetic dams].

Through the development of treatment of diabetes mellitus, diabetic cases of pregnancy have been increasing, and the effects of maternal hyperglycemia and insulin-treated hypoglycemia on the growth and life of fetuses and newborns are becoming very important problems. However, it is difficult for us to investigate the fetuses of human diabetic mothers as experimental models. Although many reports deal with the development of newborns of diabetic mothers and about their secretory changes of insulin and C-peptide reactivity, there have been few reports concerning the effects of severe diabetes on pregnancy and the effects of insulin treatment on fetuses. Concerning experimental animals, there are also few reports about the effects of insulin treatment on diabetic pregnant animals. We conducted the present investigation to determine the effects of insulin treatment on the growth and metabolism of the fetuses of diabetic pregnant rats. Virgin female Wistar rats weighing 200 approximately 300 g were caged overnight with male rats. The mated females were isolated and the gestational age was calculated from noon of this day (zero). Seventeen of 24 pregnant rats received a rapid intravenous injection of 50 mg/kg body weight of streptozotocin (STZ) in 0.4 ml of 0.01 M citrate buffer (pH 4.5) immediately after blood samples were collected through the jugular vein under light ether anaesthesia on the 5th day of gestation. Seven pregnant rats were injected with only 0.4 ml of citrate buffer and served as the controls. These rats were divided into four groups, and each group was named as follows: Normal pregnant rats group (group I, n = 7), diabetic pregnant rats group (group II, n = 6) and insulin-treated diabetic pregnant rats group (group III: plasma glucose level 60 approximately 300 mg/dl, n = 6 and group IV: plasma glucose level below 60 mg/dl, n = 5). Group III and IV rats were treated with a subcutaneous injection of Lente Insulin (from 2 u. to 6 u.) every day from the 13th to the 19th day of gestation. Group II rats were injected with saline every day in the same way. Maternal blood samples were collected under light ether anaesthesia after feeding ad libitum on the 5th and 12th days of gestation. On the 20th day of gestation, the pregnant rats were anaesthetized by an intraperitoneal injection of sodium pentobarbital, and blood samples were collected in the manner stated above. Each fetus and placenta was taken out individually by hysterotomy.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

The validity of Monte Carlo simulation in studies of scattered radiation in diagnostic radiology.

A computer program using Monte Carlo methods has been developed for the simulation of photon scattering in tissue-equivalent phantoms for incident x-rays in the diagnostic energy range. The study verified that the sampling schemes used in the program can produce random samples according to the theoretical probability distribution functions which describe the photon-scattering process. The Monte Carlo program was applied to determinations of the scatter fractions and edge responses for various phantom sizes, X-ray energies, and recording systems. These quantities were also measured experimentally under comparable imaging conditions. Excellent agreement was obtained between the predicted and experimental results. This investigation established the validity of our Monte Carlo calculations for studies of the physical characteristics of scattered radiation in diagnostic radiology.

Computers↗
PubMed1983

Energy and angular dependence of x-ray absorption and its effect on radiographic response in screen--film systems.

The relationship between the film density and the x-ray energy absorbed in the screens, and the effect of the components of a screen--film system on x-ray absorption in the screen phosphor has been studied. It is concluded that, to a good approximation, the total absorbed x-ray energy can be calculated ignoring components other than the phosphor, and that the absorbed energy is related to the film density through the characteristic curve of the film. This simple relationship provides a basis for the theoretical prediction of the radiographic performance of an imaging system. Analytical expressions have been derived for the energy absorbed in model screens containing one or two high-atomic-number elements. For incident energies above the K-edge of the high-Z elements, the contribution of the K x-rays to energy absorption was included by use of a K-reabsorption factor. This factor was determined for eight screen pairs as a function of incident photon energy and incident angle.

Mathematics↗
PubMed1983

Effect of collimators on the measurement of diagnostic x-ray spectra.

One of the difficulties in the measurement of diagnostic x-ray spectra is the high fluence rate of the photons, which may exceed the capability of the spectrometer system. Pinhole collimators are often used which reduce the count rate to an acceptable level. The measured spectrum, however, may be distorted due to the penetration of photons through the collimator material. In this study, the effects of collimators on the measured spectra were evaluated. As an indicator of collimator performance, we determined the transmission equivalent aperture (TEA), through which a portion of the incident photons impinge on the detector. The dependence of the TEA on the geometry of collimation, pinhole area, collimator material and thickness, detector area and incident x-ray energy was investigated. The penetration correction factors (PCF) for the measured spectra were also derived. We obtained good correspondence between the theoretical spectra and the measured spectra which were corrected for collimator penetration by means of the calculated PCFS. Our results indicate that diagnostic x-ray spectra generated at high tube current can be measured if one uses a collimator with a small aperture together with its PCF.

Mathematics↗
PubMed1983

Detectability of depth information by use of magnification stereoscopic technique in cerebral angiography.

Two types of stereoscopic phantoms were constructed to determine the sensitivity of observers in detecting depth information obtained by means of the magnification stereoscopic technique. One of these, a "plus" phantom, contained perpendicular aluminum wires at the top and bottom of steps of various thicknesses; the observer was asked to identify whether one of the wires was on the top, the bottom, or uncertain in location. The fraction of correct responses versus the height of the step was plotted, indicating the detectability of depth. Fourteen of 20 unselected observers (70%) responded consistently and were considered "good" observers. In general, the greater the stereo shift, the greater the fraction of correct responses. A second phantom, a mesh phantom, contained standard and randomly positioned test wires. The observer was asked to identify the depth position of a test wire with respect to the standard wire if they were in the same plane. It was found that observers can discriminate depth differences of one to two millimeters in magnification stereoscopy, and similar performance for magnification stereoscopic cerebral angiograms is expected.

Cerebral Angiography↗
PubMed1983

Evaluation of cassette performance: physical factors affecting patient exposure and image contrast.

Physical properties of four radiographic cassettes were investigated in combination with various screen/film systems. These properties included (a) transmittance of monoenergetic x rays over 14-96 keV and comparison with predictions based on attenuation coefficients; (b) relative patient exposure from 60 to 120 kV (from phantom measurements) and correlation with predictions based on measured transmittance as well as average energies and angles of incident radiation; and (c) amounts of scatter from various cassette materials and comparison with Monte Carlo calculations. The results provide a model of performance based on quantitation of cassette effects on system speed and image contrast. Carbon-fiber cassettes required the lowest patient exposure, produced the least scatter, and (in low-scatter situations) were capable of increased image contrast.

Aluminum↗
PubMed1983

Physical and clinical evaluation of new high-strip-density radiographic grids.

The imaging performance of new high-strip-density (HSD) grids having 57 lines/cm was compared with that of conventional low-strip-density (LSD) grids having 33 or 40 lines/cm. The unique advantage of HSD grids is that, under most standard radiographic conditions, the grid lines are not noticeable on the final image, even if the grid is stationary. This is due to the combined effect of the high fundamental spatial frequency of HSD grids, the modulation transfer function of screen-film systems and of the human visual system, and scattered radiation. Monte Carlo simulation studies, phantom images, and clinical evaluation indicate that HSD grids can provide contrast improvement factors and Bucky factors that are comparable to or slightly better than those obtained with LSD grids. Therefore, it may now be possible to eliminate moving Bucky trays from radiographic tables and fluoroscopic devices.

Bone and Bones↗
PubMed1983

High-speed, single-screen/single-emulsion film systems: basic imaging properties and preliminary clinical applications.

We investigated the potential clinical use of single-screen/single-emulsion film systems by comparing their relative speeds, modulation transfer functions (MTFs), Wiener spectra, and H & D curves with those of conventional screen-film systems. The relative speeds of single screens with single-emulsion Kodak OM film (single systems) were 50-60% lower than those of the conventional double screens with double-emulsion Kodak OG film (double systems), but the single systems yielded a 75-110% increase in the MTF at 2 cycles/mm. The single system had a noise level comparable to or slightly greater than that of the double systems. Phantom images and preliminary clinical radiographs indicated that single systems can improve image resolution over that obtainable with double systems under the same exposure conditions. More importantly, the use of a single system provided an approximately 40% reduction in patient exposure while providing a comparable radiographic image quality.

Humans↗