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N Motomura

Publications and source records attributed to N Motomura.

At least 19 recordsLinked to original sources
PubMed2001

The CdTe detector module and its imaging performance.

UNLABELLED: In recent years investigations into the application of semiconductor detector technology in gamma cameras have become active world-wide. The reason for this burst of activity is the expectation that the semiconductor-based gamma camera would outperform the conventional Anger-type gamma camera with a large scintillator and photomultipliers. Nevertheless, to date, it cannot be said that this expectation has been met. METHODS: While most of the studies have used CZT (Cadmium Zinc Telluride) as the semiconductor material, we designed and fabricated an experimental detector module of CdTe (Cadmium Telluride). The module consists of 512 elements and its pixel pitch is 1.6 mm. We have evaluated its energy resolution, planar image performance, single photon emission computed tomography (SPECT) image performance and time resolution for coincidence detection. RESULTS: The average energy resolution was 5.5% FWHM at 140 keV. The intrinsic spatial resolution was 1.6 mm. The quality of the phantom images, both planar and SPECT, was visually superior to that of the Anger-type gamma camera. The quantitative assessment of SPECT images showed accuracy far better than that of the Anger-type camera. The coincidence time resolution was 8.6 ns. All measurements were done at room temperature, and the polarization effect that had been the biggest concern for CdTe was not significant. CONCLUSION: The results indicated that the semiconductor-based gamma camera is superior in performance to the Anger-type and has the possibility of being used as a positron emission computed tomography (PET) scanner.

Brain↗
PubMed2001

Aortic root replacement and coronary interposition using a cryopreserved allograft and its branch.

This communication describes a modified aortic root replacement technique using a cryopreserved allograft consisting of the aortic conduit and its branch. This method was applied in a patient suffering from infective pseudoaneurysm which had developed after aortic root replacement using an artificial graft with a mechanical aortic valve. A piece of the innominate artery obtained from the aortic allograft was used for interposition between the fragile left coronary artery root and the main conduit of the allograft.

Aneurysm, False↗
PubMed2001

Thoracoscopy for minimally invasive axillo-coronary artery bypass.

Minimally invasive axillo-coronary artery bypass via a small thoracotomy or a limited sternotomy was performed in five patients. For this approach, videoscopy was used to determine the intrapleural path of each vein graft, which was curved by the expanded lung tissue and had the potential for kinking or distortion. Postoperative angiography confirmed the patency of each graft with no kinking or distortion. Thoracoscopy facilitates this approach, allowing appropriate placement of the vein graft in the chest cavity.

Aged↗
PubMed2001

Reduction of mental stress with lavender odorant.

The effect of the lavender odorant on a Japanese version of Cox and Mackay's stress/arousal adjective checklist for three groups was studied. One group of 14 was placed into a (2 x 2- x 3 m) sound protected room for 20 min without the presentation of an odor, an analogous group of 15 received the odor oil, and one group of 13 received a nonstressful condition. Analysis suggested that lavender odorants were associated with reduced mental stress and increased arousal rate.

Adult↗
PubMed2001

[Indications for and results of cryopreserved homograft valve replacement].

The cryopreserved aortic homograft valve is one of the most reliable of the stentless biological prosthesis if implanted properly. Due to the limited availability of homograft valves in Japan, the indications for their use are different from those in other countries. The first indication is active infective endocarditis in the aortic valve position, especially infection surrounding artificial implants. Another indication is for reconstruction of the right ventricular outflow tract during pulmonary autografting. Finally, aortic valve replacement in young women of childbearing age who wish become pregnant is an accepted indication. Since 1992, cryopreserved homograft valves have been used in Japan, and the number of surgeries performed with them has gradually increased. While efforts have been made to expand the homograft bank system in some areas, the supply remains insufficient. Because the demand for homografts is high, it is extremely important to establish a nationwide tissue bank system as soon as possible.

Aortic Valve↗
PubMed2000

Myotonic dystrophy associated with 47 XYY syndrome.

A case of myotonic dystrophy with 47 XYY presented with tall stature and mental retardation. The patient was a 37-year-old male. In addition to grip myotonia and percussion myotonia, severe weakness and atrophy were noted in the face and the neck muscles and in the distal muscles of the four limbs. He also had diabetes mellitus, cataracts and sexual behavior abnormalities. He was found to be 47 XYY from chromosomal examinations. The combination of 47 XYY syndrome and myotonic dystrophy has not been reported previously.

Adult↗
PubMed2000

Quantitative planar imaging method for measurement of renal activity by using a conjugate-emission image and transmission data.

We are proposing a method to accurately measure renal activity in renography using Tc-99m labeled tracers. This method uses a conjugate-view image and transmission data for attenuation correction, the triple energy window (TEW) method for scatter correction, and background correction techniques that consider the source volume for accurate background activity correction. To examine this method in planar imaging, we performed two renal phantom studies with various uniform background activity concentrations. One study used two ideal box-shaped kidney phantoms with a thickness of 2 or 4 cm in a water tank and the other study employed two real kidney-shaped phantoms in a fillable abdominal cavity. For these studies the kidney phantom-to-background activity concentration ratio (S) was changed from 5 to infinity. The transmission data were obtained with an external Tc-99m line array source. The anterior- and posterior-view emission images were acquired with a dual-headed gamma camera simultaneously and the TEW method was used to correct scatter for the emission and transmission images. The results showed that this method with both the accurate background correction and scatter correction could give depth-independent count rates and could estimate the true count rate with errors of less than 5% for all S values. However, if either accurate background correction or scatter correction was performed alone, the absolute error increased to about 50% for the smaller S values. Our proposed method allows one to accurately and simply measure the renal radioactivity by planar imaging using the conjugate-emission image and transmission data.

Kidney↗
PubMed2000

[Feasibility study of CdTe Semiconductor detector for gamma camera--evaluation of planar images].

To evaluate the performance of a semiconductor detector for use in a gammacamera system, we assembled a detector with a small field of view--1 inch x 1 inch and 1 inch x 2 inch--made from CdTe (Cadmium telluride). We then compared the planar images and energy resolution of the resulting detectors against those of a conventional gammacamera. Pixel pitch of the detector was 1.6 mm x 1.6 mm, and was manufactured by Acrorad Corporation. Average FWHM of the energy spectrum for the semiconductor detector was 5.11% (SD: 0.80%, Best: 3.26%, Worst: 6.68%). The planar images obtained were of a letter phantom made from pieces of lead and of an IMP brain phantom. Since the field of view of the semiconductor detector was small, the image of the IMP brain phantom was acquired by moving the semiconductor over the collimated detector module until the area of the entire phantom was covered. The images from the semiconductor assembly were compared with those from a conventional gammacamera using the same conditions, and it was found that visual image quality was superior to those of the conventional camera system.

Brain↗
PubMed2000

[Feasibility study of SPECT quantification using CdTe semiconductor detector].

Quantification of SPECT using CdTe semiconductors as a detector head in nuclear medicine equipment was investigated. A prototype of semiconductor detectors with an effective field-of-view as small as 2.54 cm x 5.08 cm was constructed, and a cylindrical phantom containing four spherical phantoms with capacities 71, 56, 42, and 15 ml, was used. Water was placed in three of these spherical phantoms (71, 56, and 42 ml), and 8.362 MBq of 99mTc was poured into the remaining 15 ml phantom. In the outer cylindrical phantom, 925 MBq (6200 ml) of 99mTc was placed. A Toshiba LEHR (Low Energy High Resolution) collimator was attached to the semiconductor detectors, and SPECT acquisition with a rotation radius 132 mm was performed. It was found that in the data thus acquired using the semiconductor detector, the amount of scattered gamma-rays decreased by 33% as compared to data acquired using NaI(Tl) scintillators under the same condition. Moreover, when attenuation correction was applied to SPECT data from the CdTe semiconductor detector, the measurement accuracy of radioactivity improved by 16% as compared to SPECT data from NaI(Tl) scintillators with the same acquisition and post-correction conditions. Finally, the CdTe detector data with only attenuation correction was found to have almost the same grade of accuracy as NaI scintillator data with both attenuation and TEW scatter corrections.

Feasibility Studies↗
PubMed2000

Comparative study on genomes of two Japanese melon necrotic spot virus isolates.

Nucleotide sequences of the genomes of two Japanese Melon necrotic spot virus (MNSV) isolates, NH and NK were determined. The open reading frames (ORFs) in both genomes encode five proteins: p29 (the pre-readthrough domain of p89), p89 (the readthrough domain of p89 identified as the putative RNA-dependent RNA polymerase), p14 (the pre-readthrough domain of p7A), p7A (the putative movement protein), and p42 (coat protein, CP). Nucleotide and amino acid sequence identities of the five proteins of NH and NK isolates were estimated at 97.4-99.5% and 97.7-100%, respectively. NK isolate but not NH isolate infected systemically leaves of Cucumis melo plants. When deduced amino acid sequences of p7A proteins of NH and NK isolates were compared, only one difference at position 16 (serine in NH isolate and isoleucine in NK isolate) was observed. p7A protein is considered the putative movement protein. The serine of p7A protein of NH isolates may be involved in systemic infection. In addition, phylogenetic relationships of genes based on nucleotide sequences revealed that NH and NK isolates might form a group, and S isolate, serologically different from NH and NK isolates, might represent a distinct isolate not belonging to this group.

Amino Acid Sequence↗
PubMed1999

Effects of scatter and attenuation correction on quantitative analysis of beta-CIT brain SPET.

The aim of this study was to evaluate the effects of scatter correction (SC) and attenuation correction (AC) on the quantification of dopamine transporters using 123I-beta-CIT brain SPET images. Quantitative analysis was carried out using static SPET images obtained 23 h after injection. We calculated V3" [(striatal-occipital)/occipital ratio] values from images without correction, with AC, and with SC and AC. Two types of regions of interest (ROI) were placed on the striatum: a small square ROI and a larger ROI containing most of the striatum. After validating the correction method in a phantom experiment, a human study was carried out involving eight normal volunteers and 15 patients. The larger ROI yielded smaller V3" values. The effect of attenuation correction was modest, whereas that of scatter correction was marked. It was shown that beta-CIT SPET quantification was affected by the size of the ROI, photon scattering and attenuation, and that scatter and attenuation correction improved the accuracy of the quantification. Methodological standardization in image processing and the type of ROI should be considered when a multi-centre trial is planned.

Aged↗
PubMed1999

Feasibility of simultaneous stress 99mTc-sestamibi/rest 201Tl dual-isotope myocardial perfusion SPECT in the detection of coronary artery disease.

UNLABELLED: This study assesses feasibility and diagnostic accuracy of simultaneous stress 99mTc-sestamibi/rest 201 TI dual-isotope myocardial perfusion SPECT with Moore's correction method, in which contamination originating from lead x-rays produced in a collimator was subtracted in the 201TI windows. METHODS: Eighty-one patients with suspected coronary artery disease received exercise 99mTc-sestamibi injection, followed by rest 201TI injection 50 min later, and dual-isotope SPECT was performed (group 1). These results were compared with coronary angiographic findings. Furthermore, to estimate the accuracy of Moore's correction method, 201TI crosstalk into the 99mTc acquisition window (group 2A, n = 20) and 99mTc crosstalk into the 201TI acquisition windows (group 2B, n = 20) were studied. For group 2A, stress 99mTc-sestamibi SPECT (single 99mTc-sestamibi SPECT) was performed, followed by 201TI injection at rest and dual-isotope SPECT acquisition 50 min later. For group 2B, rest 201TI SPECT (single 201TI SPECT) was performed, followed by 99mTc-sestamibi injection at rest and dual-isotope SPECT acquisition 30 min later. RESULTS: Sensitivity and specificity in group 1 were 83% and 99%, respectively, when > or =75% coronary artery narrowing was considered significant. In groups 2A and 2B, SPECT images were divided into 24 segments, and relative regional uptake in each segment was obtained. In group 2A, relative regional uptake of single 99mTc-sestamibi SPECT correlated well with that of dual-isotope SPECT (r = 0.942). In group 2B, relative regional uptake of single 201TI SPECT correlated well with that of dual-isotope SPECT (r = 0.935). Furthermore, in low 201TI uptake segments with relative regional uptake in both single- and dual-isotope SPECT of < or =70%, the degree of concordance between single- and dual-rest 201TI was considered to be high with Bland-Altman analysis and the kappa statistic. Comparison of perfusion defect type demonstrated that, of 22 stress defects within infarct zones, 95% were irreversible and 5% were reversible. In contrast, of 28 stress defects within stenosed vessel zones in noninfarct zones, 89% were reversible and 11% were irreversible (P < 0.0001 versus infarct zones). CONCLUSION: Simultaneous dual-isotope imaging with Moore's correction method is feasible, with acceptable accuracy for detection of coronary artery disease and a small amount of crosstalk into each window.

Aged↗
PubMed1999

[Practical compensation method of downscattered component due to high energy photon in 123I imaging].

We looked into the problem that the quantitative values of 123I data vary according to collimator type. First, we made the assumption that the quantitative values of 123I data are degraded by the scattered photons from the 529 keV component which contaminate the 159 keV imaging data. Then, the 123I Dual Window (IDW) method was proposed to improve the quantitative values of the 123I data. The IDW method uses the energy window on the high-energy side to estimate the amount of scattered 529 keV photons which contaminate the 159 keV data. Since only a dual-energy window acquisition and a simple image processing are needed, the IDW method can be performed in most conventional gamma camera systems. In the torso phantom studies, the IDW method reduced the error in the semi-quantitative value 'heart/mediastinum (H/M) ratio' in 123I-MIBG myocardial scintigraphy from 22% to 1%. The results of the phantom studies indicate that the IDW method can improve the quantitative values of 123I data.

3-Iodobenzylguanidine↗
PubMed1998

Estradiol inhibits allograft-inducible major histocompatibility complex class II antigen expression and transplant arteriosclerosis in the absence of immunosuppression.

BACKGROUND: The etiology of transplant arteriosclerosis is unknown, but current data point to the alloimmune response. Previously, we found that estradiol-17beta (E2) with immunosuppressant cyclosporine abolishes major histocompatibility complex (MHC) class II expression in the allograft. This study determines the effect of E2 on MHC class II antigen expression in the allograft, in the absence of immunosuppression. METHODS: Lewis male rats received orthotopic abdominal aorta allografts from male Brown-Norway rats. The recipients were treated continuously subcutaneously with either 20 microg x kg(-1) x day1 of E2 (n=20) or placebo (n=20), from 2 days before transplantation until death on posttransplant days 1, 3, 7, and 14. The allografts were harvested and processed for morphometry and for immunohistochemical staining of MHC class II antigens, macrophages, CD4 and CD8 T lymphocytes, interferon-gamma (IFN-gamma), and IFN-gamma receptor. RESULTS: With E2 treatment, we observed that inducible MHC class II antigen expression is abolished in the media of the vascular allograft; the expression of IFN-gamma and IFN-gamma receptor is unaffected; and macrophage infiltration of the vascular allograft is inhibited significantly (P<0.01), whereas the CD4 and CD8 T lymphocytes are not significantly (P=0.07) suppressed. The myointimal hyperplasia in the allografts from E2-treated-recipients was 3-4-fold less than that from the placebo-treated recipients. CONCLUSIONS: Without immunosuppression, E2 inhibition of transplant arteriosclerosis is still associated with inhibition of inducible MHC class II antigen expression in the allografts. The estradiol-17beta abolition of inducible MHC class II antigen expression in the aorta allograft occurs in spite of up-regulation of IFN-gamma ligand and receptor protein.

Animals↗
PubMed1998

Exposure of vascular allografts to insulin-like growth factor-I (IGF-I) increases vascular expression of IGF-I ligand and receptor protein and accelerates arteriosclerosis in rats.

BACKGROUND: Accelerated arteriosclerosis limits the survival of transplanted hearts. We hypothesized that insulin-like growth factor-I (IGF-I) is crucial in accelerating transplant arteriosclerosis. Recently, we reported that exposure to IGF-I prior to transplantation accelerates transplant arteriosclerosis in the rat aorta allograft model. Here, we studied the mechanism whereby IGF-I exposure accelerates transplant arteriosclerosis. METHODS: The abdominal aorta was harvested from male Brown Norway rats and exposed to 0, 200, or 500 ng/ml of IGF-I at 37 degrees C for 30 min prior to transplantation to the abdominal position of male Lewis rats. The allografts were harvested 14 days later and processed for immunohistochemical staining for alpha-actin, growth factors (IGF-I, IGF-I receptor, platelet-derived growth factor-BB, and basic fibroblast growth factor), and immunological markers (major histocompatibility complex class II antigen, macrophage, and CD4- and CD8-positive T cells). RESULTS: By 14 days, the ex vivo IGF-I donor aorta treatment with IGF-I increased in a concentration-dependent manner the expression of IGF-I and IGF-I receptor in both the intima and the adventitia. In contrast, the expression of platelet-derived growth factor-BB was decreased in a concentration-dependent manner in the intima while basic fibroblast growth factor remained unchanged. The cell-mediated immune response was not affected by IGF-I at 14 days after transplantation, which suggests that the immune events associated with acceleration of transplant arteriosclerosis may occur at an earlier time. CONCLUSION: Acceleration of transplant arteriosclerosis by exposure to IGF-I is associated with increased IGF-I ligand and receptor expression in the allograft vascular wall. These data further suggest that IGF-I may be a major factor in mediating graft arteriosclerosis.

Actins↗
PubMed1998

Application of transmission scan-based attenuation compensation to scatter-corrected thallium-201 myocardial single-photon emission tomographic images.

A practical method for scatter and attenuation compensation was employed in thallium-201 myocardial single-photon emission tomography (SPET or ECT) with the triple-energy-window (TEW) technique and an iterative attenuation correction method by using a measured attenuation map. The map was reconstructed from technetium-99m transmission CT (TCT) data. A dual-headed SPET gamma camera system equipped with parallel-hole collimators was used for ECT/TCT data acquisition and a new type of external source named "sheet line source" was designed for TCT data acquisition. This sheet line source was composed of a narrow long fluoroplastic tube embedded in a rectangular acrylic board. After injection of 99mTc solution into the tube by an automatic injector, the board was attached in front of the collimator surface of one of the two detectors. After acquiring emission and transmission data separately or simultaneously, we eliminated scattered photons in the transmission and emission data with the TEW method, and reconstructed both images. Then, the effect of attenuation in the scatter-corrected ECT images was compensated with Chang's iterative method by using measured attenuation maps. Our method was validated by several phantom studies and clinical cardiac studies. The method offered improved homogeneity in distribution of myocardial activity and accurate measurements of myocardial tracer uptake. We conclude that the above correction method is feasible because a new type of 99mTc external source may not produce truncation in TCT images and is cost-effective and easy to prepare in clinical situations.

Adult↗
PubMed1998

Simultaneous acquisition of iodine-123 emission and technetium-99m transmission data for quantitative brain single-photon emission tomographic imaging.

The aim of this study was to obtain quantitative iodine-123 brain single-photon emission tomographic (SPET) images with scatter and attenuation correction. We used a triple-headed SPET gamma camera system equipped with fan-beam collimators with a technetium-99m line transmission source placed at one of the focal lines of the fan-beam collimators. Four energy windows were employed for data acquisition: (a) 126-132 keV, (b) 132-143 keV, (c) 143-175 keV and (d) 175-186 keV. A simultaneous transmission-emission computed tomography scan (TCT-ECT) was carried out for a brain phantom containing 123I solution. The triple energy window scatter correction was applied to the 123I ECT data measured by means of the windows (b), (c) and (d) acquired by two detectors. Attenuation maps were reconstructed from 99mTc TCT data measured by means of the windows (a), (b) and (c) acquired by one detector. Chang's iterative attenuation correction method using the attenuation maps was applied to the 123I ECT images. In the phantom study cross-calibrated SPET values obtained with the simultaneous mode were almost equal to those obtained with the sequential mode, and they were close to the true value, within an error range of 5.5%. In the human study corrected images showed a higher grey-to-white matter count ratio and relatively higher uptake in the cerebellum, basal ganglia and thalamus than uncorrected images. We conclude that this correction method provides improved quantification and quality of SPET images and that the method is clinically practical because it requires only a single scan with a 99mTc external source.

Algorithms↗