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Kuniaki Hayashi

Publications and source records attributed to Kuniaki Hayashi.

At least 19 recordsLinked to original sources
PubMed2005

Effects of risedronate on trabecular microstructure and biomechanical properties in ovariectomized rat tibia.

We determined the effect of risedronate on the trabecular microstructure of ovariectomized rat tibiae, using micro-computed tomography, in order to investigate how changes in microstructure contribute to biomechanical properties. Fifty 18-week-old rats underwent sham operation (n=10) or ovariectomy (OVX) (n=40). The OVX rats were further divided into four groups (n=10 for each group) and treated with risedronate at doses of 0, 0.1, 0.5 or 2.5 mg/kg for 9 months. OVX caused deterioration of three-dimensional trabecular microstructure, notably structure model index (SMI) and connectivity density, while treatment of OVX rats with risedronate at 0.5 and 2.5 mg/kg improved those deleterious microstructural changes. Biomechanical property, as assessed by finite element analysis (FEA), correlated significantly with trabecular bone volume fraction (BV/TV), and the correlation further increased substantially when microstructural parameters were added, especially SMI and connectivity density, with risedronate therapy. Thus, it is suggested that, in addition to increasing bone mass, risedronate improves biomechanical property by maintaining a plate-like structure as well as connectivity of trabeculae.

Animals↗
PubMed2005

Visceral and peripheral arterial pseudoaneurysms.

OBJECTIVE: Pseudoaneurysms are not rare, and various conditions can cause a pseudoaneurysm in all the cardiovascular systems. In this article, we discuss and show images of pseudoaneurysms of various arteries caused by various conditions. CONCLUSION: CT, MRI, sonography, and angiography may all be valuable in the imaging workup of pseudoaneurysms. Knowledge of the various appearances of pseudoaneurysms and of the proper management is essential to prevent a catastrophic outcome in cases of pseudoaneurysm.

Aneurysm, False↗
PubMed2005

[Normal radiographic anatomy of thoracic structures: analysis of 316 lateral chest radiographs].

PURPOSE: To study the frequency of visualization and characteristics of normal thoracic structures on lateral chest radiographs in the Japanese population. MATERIALS AND METHODS: We reviewed 316 lateral chest radiographs of men and women ranging in age from 20 to 90 years. The frequency of visualization and configuration of structures including major, minor, superior and inferior accessory fissures, and orifices of the right and left upper lobe bronchi were reviewed. RESULTS: On lateral chest radiographs, major fissure and minor fissure were visualized in 99.4% and 87.3%, respectively. Superior accessory fissure and inferior accessory fissure were visualized in 1.9% and 9.5%, respectively. Orifices of the right and left upper bronchi were seen in 92.4% and 98.4%, respectively. CONCLUSION: Frequency of visualization and characteristics of various normal anatomic structures on lateral chest radiographs in the Japanese population differ from those reported previously from the West. Familiarity with these normal thoracic structures and variations is important for daily image interpretation.

Adult↗
PubMed2004

Growth rate of aortic diameter in patients with type B aortic dissection during the chronic phase.

BACKGROUND: The purpose of this study was to evaluate the growth rate of type B double-barrel aortic dissection with computed tomography (CT) and the factors influencing its enlargement. METHODS AND RESULTS: Sixty-two patients were entered into this study, and regular follow-up CT studies (mean; 49.1 months) were performed. The affected aortas and iliac arteries were divided into 5 segments (aortic arch, descending thoracic, suprarenal abdominal, infrarenal abdominal aorta, and iliac artery). Fifty-two of 62 patients (83.9%) had 1 or more segments increased in size during follow-up period. In a total of 177 segments, the presence or absence of blood flow in the false lumen and aortic diameter were evaluated on CT during the follow-up period. The factors (gender, diabetes mellitus, atherosclerotic disease, smoking, entry site in arch, initial diameter, chronic obstructive pulmonary disease, blood pressure, and age) influencing increase in the diameter and growth rate were also evaluated. Of 177 segments, 132 segments (74.6%) increased in size during the follow-up period. The presence of blood flow in the false lumen was the only significant risk factor for increase in the diameter in the univariate and multivariate analysis. The group with blood flow in the false lumen had a significantly higher mean growth rate (3.3 mm/year) than the group without blood flow (-1.4 mm/year) (P<0.0001). The growth rate of aortic dissections in thoracic aorta and abdominal aorta were 4.1 and 1.2 mm/year, respectively. There was a significant difference in the growth rate between the 2 groups (P=0.0003). CONCLUSIONS: In type B aortic dissection, the affected aortas have shown a high incidence of enlargement during the follow-up period, and more careful follow-up study is needed for aortic dissections in the thoracic aorta. The presence of blood flow in the false lumen is the most important risk factor for aortic enlargement.

Adult↗
PubMed2004

Long-term outcome of type B aortic intramural hematoma: comparison with classic aortic dissection treated by the same therapeutic strategy.

BACKGROUND: The long-term clinical course and therapeutic strategy of patients with type B aortic intramural hematoma (IMH) are not completely known. The purpose of this study was to clarify long-term prognosis of patients with type B IMH by comparison with type B classic aortic dissection (AD). METHODS: Clinical data were compared retrospectively between 37 patients with acute type B IMH (IMH group) and 69 patients with acute type B AD (AD group). Our therapeutic strategy for all patients was medical therapy with frequent follow-up imaging studies and timed surgical repair in cases with progression. RESULTS: Initially, medical therapy was selected for 104 of 106 (98%) patients. In two patients of the AD group, immediate surgical treatment was performed because of aortic rupture. As for complications, no significant difference was seen between the two groups. There was no significant difference in the incidence of the total number of deaths; early death, late death, or causes of deaths. The actuarial survival rates for the IMH group at 1, 2, 5, and 10 years were 97 +/- 3, 97 +/- 3, 85 +/- 9, and 85 +/- 9%, respectively; the values were 96 +/- 1, 96 +/- 1, 89 +/- 4, and 71 +/- 9%, for the AD group. The actuarial survival rates of the two groups were not significantly different from each other (p = 0.398). CONCLUSIONS: Patients with type B IMH have similar long-term prognosis to patients with type B AD. Medical therapy with frequent follow-up imaging studies and timed surgical repair in cases with progression can be a rational therapeutic strategy in patients with type B IMH.

Aged↗
PubMed2004

Imaging of the patulous Eustachian tube: high-resolution CT evaluation with multiplanar reconstruction technique.

OBJECTIVE: To evaluate the 3D anatomy of the ET and its surrounding tissues in cases with or without patulous Eustachian tube (ET) using CT with the multiplanar reconstruction (MPR) technique. MATERIAL AND METHODS: Twenty patients with a patulous ET and 25 without middle ear problems were investigated. After performing a temporal bone CT examination, MPR images of the ET were reconstructed and measurements were made. RESULTS: The ET lumen and its surrounding tissues were clearly identified. In the patulous ET group, the ET lumen was open throughout the cartilaginous portion and the volume of the low-density area was smaller in size than in the controls. In unilateral patulous ET patients, the anatomical features were found to be similar on both sides, in spite of the fact that the non-involved side did not show symptoms associated with a patulous ET. CONCLUSION: For the first time, we were able to obtain clear reconstructed images of the patulous ET and its surrounding structure and to study its anatomical features. This method is useful for obtaining a better understanding of the ET and ET-related diseases such as patulous ET.

Adolescent↗
PubMed2004

High resolution CT anatomy of the pulmonary fissures.

RATIONALE AND OBJECTIVES: Pulmonary interlobar fissures are important landmarks for proper identification of normal pulmonary anatomy and evaluation of disease. The purpose of this study was to define the radiologic anatomy of the pulmonary fissures using high resolution computed tomography (HRCT) in a large population. METHODS: HRCT of the lungs from aortic arch to diaphragm was performed in 622 patients, with a slice thickness of 1 mm and slice interval of 10 mm. Major, minor, and accessory fissures were studied for their orientation and completeness. RESULTS: Both major fissures were mostly facing laterally in their upper parts (100% and 89% right and left, respectively). The left major fissure faced medially (69%) while the right major fissure faced lateral (60%) in their lower parts. The right major fissure was more often incomplete (48% as compared with 43% on the left, P < 0.05). Minor fissures were convex superiorly with the apex in the anterolateral part of the base of the upper lobe, and were incomplete in 63% of cases. Azygos, inferior accessory, superior accessory, and left minor fissures were also seen in 1.2%, 8.6%, 4.6%, and 6.1% of the cases, respectively. CONCLUSION: The pulmonary fissures are highly variable and the right major fissure differs considerably from the left. The fissures are often incomplete.

Adolescent↗
PubMed2004

Application of an artificial neural network to high-resolution CT: usefulness in differential diagnosis of diffuse lung disease.

OBJECTIVE: The purpose of our study was to evaluate the diagnostic performance of an artificial neural network (ANN) in differentiating among certain diffuse lung diseases using high-resolution CT (HRCT) and the effect of ANN output on radiologists' diagnostic performance. MATERIALS AND METHODS: We selected 130 clinical cases of diffuse lung disease. We used a single three-layer, feed-forward ANN with a back-propagation algorithm. The ANN was designed to differentiate among 11 diffuse lung diseases by using 10 clinical parameters and 23 HRCT features. Therefore, the ANN consisted of 33 input units and 11 output units. Subjective ratings for 23 HRCT features were provided independently by eight radiologists. All clinical cases were used for training and testing of the ANN by implementing a round-robin technique. In the observer test, a subset of 45 cases was selected from the database of 130 cases. HRCT images were viewed by eight radiologists first without and then with ANN output. The radiologists' performance was evaluated with receiver operating characteristic (ROC) analysis with a continuous rating scale. RESULTS: The average area under the ROC curve for ANN performance obtained with all clinical parameters and HRCT features was 0.956. The diagnostic performance of four chest radiologists and four general radiologists was increased from 0.986 to 0.992 (p = 0.071) and 0.958 and 0.971 (p < 0.001), respectively, when they used the ANN output based on their own feature ratings. CONCLUSION: The ANN can provide a useful output as a second opinion to improve general radiologists' diagnostic performance in the differential diagnosis of certain diffuse lung diseases using HRCT.

Adolescent↗
PubMed2004

[Evaluation of strongly hyperintense area in breast lesions on fat-suppressed T2-weighted images correlated with histopathology].

The purpose of this study was to correlate strongly hyperintense areas(SHI) in breast lesions on FS-T2WI with histopathology and to evaluate the usefulness of the distribution patterns of SHI in the differentiation of benign and malignant breast lesions. MR imaging with pathological correlation was available in 157 breast lesions of 153 patients. The distribution patterns of SHI were classified into seven types. SHI on FS-T2WI was identified in 36 of 157 breast lesions. The irregular and inhomogenous types corresponded to various histological features and were only seen in malignant lesions. The central type corresponded to central necrosis and was only seen in 2 solid-tubular carcinomas. The crescent type corresponded to peripheral fluid collection in the intracystic tumor. The septal type corresponded to fibromyxoid stroma with fibrous septations in the lesions except for one cavernous hemangioma, and was only seen in benign lesions. The smooth type corresponded to mucinous pool, fibromyxoid stroma, and ductal dilatation and did not contribute to differentiation between benign and malignant lesions only on FS-T2WI. SHI in breast lesions on FS-T2WI pathologically corresponded to mucin, fibromyxoid change, necrosis, and ductal dilatation. Evaluation of patterns of SHI is useful in differentiating between benign and malignant lesions.

Adolescent↗
PubMed2003

Which bone densitometry and which skeletal site are clinically useful for monitoring bone mass?

Long-term precision, as well as reproducibility, is important for monitoring bone mineral density (BMD) alteration in response to aging or therapy. In order to investigate which bone densitometry and which skeletal site are clinically useful for monitoring bone mass, we examined the standardized long-term precision of several bone density measurements in 83 healthy Japanese women. Annual BMD measurements were performed for 5 or 6 years using dual X-ray absorptiometry (DXA) on the lumbar spine, radius (EXP5000) and calcaneus (HeelScan); peripheral quantitative computed tomography (pQCT) on the radius (Densiscan1000); and quantitative ultrasound (QUS) on the calcaneus (Achilles+). The long-term precision error for the individual subject was given by the standard error of estimate (SEE), and the standardized long-term precision was defined as the percentage coefficient of variation (CV%) divided by the percentage ratio of the annual bone-loss rate. Based on the CV% of spinal DXA, speed of sound (SOS) and diaphyseal pQCT showed significantly higher precision than others, while radial ultradistal (UD) DXA and heel DXA showed significantly lower precision. The long-term precision errors of other measurements were statistically the same as that of the spinal DXA. The spinal DXA, the radial DXA, and pQCT at both the distal metaphysis and diaphysis showed high rates of annual bone loss. The radial trabecular BMD (pQCT) was significantly higher than that of spinal DXA. The annual rates of bone loss of QUS and of heel DXA were significantly lower than that of spinal DXA. Taken together, standardized long-term precision was obtained in the spinal DXA and radial pQCT. In conclusion, spinal DXA and radial pQCT were considered the most useful monitoring method for osteoporosis, while QUS was considered less useful.

Absorptiometry, Photon↗
PubMed2003

Bone structure and mineralization demonstrated using synchrotron radiation computed tomography (SR-CT) in animal models: preliminary findings.

We investigated the ability of synchrotron radiation computed tomography (SR-CT) to demonstrate trabecular microstructure, detail of trabecular surfaces, and mineralization of bones. Eight rat vertebrae, six rat tibiae, and eight minipig vertebrae were scanned using SR-CT at the synchrotron radiation facility Super Photon ring-8GeV (SPring-8). Images obtained using conventional micro-CT, scanning electron microscopy (SEM), and contact microradiography (CMR) were compared with the SR-CT images. SR-CT showed high image quality without visible partial volume effect. Three-dimensional SR-CT revealed shallow concavities in the bone surface, which were considered to correspond to osteoclastic resorption areas, as well as the connectivity, anisotropy, and shape (rod- or platelike) of trabeculae. Two-dimensional SR-CT showed different density along the surface of the trabecular bone, indicating the degree of bone mineralization. In conclusion, SR-CT seems to be a useful tool for delineating trabecular surfaces, evaluating bone mineralization, and revealing precise trabecular structure.

Animals↗
PubMed2003

CT imaging of the patulous eustachian tube--comparison between sitting and recumbent positions.

OBJECTIVE: The objective was to evaluate the three-dimensional anatomy of the eustachian tube (ET) and its surrounding tissues of patulous ET patients in the sitting positions by the horizontal computed tomography (CT) system with the multiplanar reconstruction (MPR) technique, and to compare the findings with those obtained in the recumbent position. METHODS: Two patients with severe bilateral patulous ET were investigated. After performing temporal bone CT examination both in the sitting and recumbent position, MPR images of the ET were reconstructed and measurement was made on a workstation. RESULTS: The ET lumen was identified at most of the portion from the pharyngeal orifice to the tympanic orifice in both positions. At the cartilaginous portion, the air space in the ET lumen was larger in the sitting position than in the recumbent position. At the bony portion of the ET, there did not seem to be any significant difference in the results of measurement in both cases. CONCLUSION: For the first time, we were able to obtain reconstructed images of patulous ET patients in the sitting position and to compare the findings with those of the recumbent position. We suggest that this method is useful for better understanding of the ET and ET-related diseases such as patulous ET.

Aged↗
PubMed2003

Magnetic resonance imaging features of aortic diseases.

The usefulness of magnetic resonance imaging (MRI) for aortic diseases is discussed, with special attention given to the MRI features of aortic dissection and Takayasu arteritis. Computed tomography (CT) and MRI provide excellent visualization of vessels and their relationship to surrounding structures; however, CT depicts the vessel lumen optimally only when contrast enhancement is used. MRI, with its inherent multiplanar imaging capability, is well suited for evaluation of the thoracic and abdominal aorta and can be used with or without contrast enhancement. Basic technical considerations in cardiac imaging, which include conventional spin-echo, fast spin-echo, cine gradient, and echo-planar imaging, with time-of-flight and phase-contrast methods, are discussed and applied to aortic aneurysm, aortic dissection, and Takayasu arteritis. The diagnostic capacity of spin-echo MRI in patients with suspected aortic dissection is enhanced when it is combined with cine MRI. Despite the ability of CT and MRI to demonstrate luminal and mural changes of aortic abnormalities, conventional angiography still may be necessary at first admission for selected patients in the late occlusive phase to provide additional information on the degree and extent of the arteritis. CT angiography and MR angiography are promising imaging techniques that will overcome difficulties in visualizing distal branch vessel lesions and obviate the need for conventional angiography in the near future.

Aortic Diseases↗
PubMed2003

Interpretation of normal anatomic structures on chest radiography: comparison of Fuji computed radiography (FCR) 5501D with FCR 5000 and screen-film system.

The purpose of this study was to investigate the usefulness of Fuji Computed Radiography (FCR) 5501D by comparing it with FCR 5000 and a screen-film system (S/F). Posteroanterior chest radiographs of ten patients with no abnormality on chest CT scans were obtained with FCR 5501D, FCR 5000, and S/F. Six observers (three radiologists and three radio-technologists) evaluated the visibility of nine normal anatomic structures (including lungs, soft tissue, and bones) and overall visibility on each image. Observers scored using a five-point scale on each structure. FCR 5000 showed a significantly higher score in soft tissue and bone structures, and overall visibility compared with S/F, but, there was no significant difference between them in the visibility of all four normal lung structures. Compared with S/F, the score for FCR 5501D was higher in eight of the nine normal structures, including three of the four lung structures (unobscured lung, retrocardiac lung, and subdiaphragmatic lung), and overall visibility. Compared with FCR 5000, the score for FCR 5501D was higher in three normal structures, including two of the four lung structures (unobscured lung and subdiaphragmatic lung), and overall visibility. FCR 5501D was the best among the three techniques to visualize normal anatomic structures, particularly the obscured and unobscured lung.

Adult↗