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Biomedical subjects

F Mihara

Publications and source records attributed to F Mihara.

At least 55 records · Page 3Linked to original sources
PubMed1992

Magnetic resonance imaging of orbital lymphangioma with and without gadolinium contrast enhancement.

BACKGROUND: Lymphangioma is a vascular tumor of the orbit with a propensity for recurrent hemorrhage. These tumors may be difficult to diagnose in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. Magnetic resonance imaging (MRI) should be ideally suited for evaluating lymphangioma due to the unique ability of MRI to characterize hemorrhage because of the paramagnetic qualities of hemoglobin. METHODS: The authors performed T1-, T2-, and proton density-weighted MRI on 12 patients with orbital lymphangioma. Six patients underwent MRI with gadolinium-DTPA contrast enhancement. The MRI studies were performed using a 1.5 Tesla super-conducting magnetic resonance unit, except for 3 early studies performed with a 0.5 Tesla unit. All studies were performed with orbital surface coil imaging. Computed tomography (CT) was performed in 10 patients. RESULTS: Tumor was visible on MRI in all 12 patients. Magnetic resonance imaging delineated clearly the internal structure of subacute and chronic hemorrhagic cysts, and differentiated between these tumors because of the different paramagnetic qualities of subacute hemorrhage compared to chronic hemorrhage. In two patients, MRI detected large tumor feeding vessels by the flow void phenomenon unique to MRI. Computed tomography did not detect these vessels. Gadolinium-contrasted T1-weighted MRI did not further delineate or characterize the tumor. CONCLUSION: Magnetic resonance imaging is the modality of choice for imaging orbital lymphangioma because of its unequalled differentiation of hemorrhagic cysts, and its unique ability to detect tumor feeding vessels by the flow void phenomenon.

Contrast Media↗
PubMed1991

Magnetic resonance imaging of choroidal melanoma with and without gadolinium contrast enhancement.

Choroidal melanoma is the most common intraocular tumor and is uniquely suited for evaluation by magnetic resonance imaging (MRI) because of the paramagnetic effect of the melanin molecule. The authors performed T1-, T2-, and proton-density-weighted MRI on 34 patients with choroidal melanoma. Nineteen patients received gadolinium contrast, T1-weighted images were superior in both detecting and delineating tumors, showing increased contrast-to-noise ratios over other images. Gadolinium contrast further increased this ratio. These images are presented as evidence that gadolinium-enhanced MRI is valuable in the evaluation of choroidal melanoma.

Choroid Neoplasms↗
PubMed1991

Gd-DTPA-enhanced short repetition time and short inversion time inversion recovery magnetic resonance imaging. Experimental and clinical assessment.

To suppress both water and fat signal while retaining the high signal of Gd-DTPA enhancement, magnetic resonance imaging (MRI) of phantoms and 28 patients with mass lesions was done using short repetition time (TR) and short inversion time inversion recovery (STIR) sequences. Optimal STIR pulse sequences of 500 to 1000/80-100/20-30 (TR/TI/TE) were determined by an experimental study. In most instances, a signal bandwidth of +/- 8 kHz was used to increase the signal-to-noise ratio. The authors measured image contrast between lesions and adjacent fatty tissue and compared postcontrast STIR and T1-weighted spin-echo (T1-W SE) images. When the signal intensity of a lesion is 80% of adjacent fatty tissue on postcontrast T1-W SE, short TR STIR images provide better tumor delineation.

Contrast Media↗
PubMed1986

99mTc-methylene diphosphonate uptake by ossifications and calcifications of non-osseous metastatic tumors.

Two cases of extra-osseous uptake of 99mTc-methylene diphosphonate (MDP) by non-osseous metastatic tumors are reported. One was a metastasis with ossification in the abdominal wall from carcinoma of the sigmoid colon and the other was a metastasis with calcification from an ovarian carcinoma. The mechanism of extra-osseous uptake of 99mTc-MDP is discussed. Bone scintigraphy can be a potential means to assess tumor spread with ossifications and calcifications.

Abdominal Neoplasms↗
PubMedDate not supplied

MRI and MR angiography in moyamoya disease.

The role of radiological imaging in moyamoya disease includes screening of the disease based on clinical findings, evaluation of the changes in vasculature and brain parenchyma, and clinical follow-up. The imaging findings in moyamoya disease are classified as primary and secondary. The primary findings essentially consist of occlusion of the circle of Willis and collateral formation, including moyamoya vessel formation. The secondary findings include cerebral infarction, white matter lesions, atrophy, and hemorrhage. For the visualization of the primary and secondary findings as well as postoperative results, MRI and MR angiography are the most reliable methods and play important roles because of their excellent diagnostic yield and noninvasiveness.

Brain↗
PubMedDate not supplied

MR imaging of orbital mass lesions with contrast agent: a preliminary report.

To investigate the advantage and limit of contrast enhancement in the examination of orbital mass lesions, precontrast T1- and T2-weighted, and postcontrast T1-weighted spin-echo images were retrospectively compared by two experienced observers. Using contrast material, intraocular tumors were well detected and characterized, and several orbital tumors were characterized as to whether cystic or necrotic and intracranial involvement was better evaluated. On the other hand, tumor-fat interface lost conspicuity when tumors showed enhancement. We conclude that gadopentetate-dimeglumine-administered T1-weighted images were helpful in detecting, differentiating and characterizing tumors of the orbit. However, the loss of contrast with fatty tissue is a disadvantage to be considered.

Contrast Media↗
PubMedDate not supplied

Peripheral findings in MR using surface coil.

Incidental peripheral lesions found during neuroradiological MR examinations with surface coils are reviewed. These include intracranial metastases during orbital examinations, cerebellar and thyroid lesions during cervical spine examinations, and dissecting and saccular abdominal aneurysms, as well as renal and intrapelvic abnormalities during lumbar spine examinations. Because of the reduced field-of-view and rapid signal drop-off in deeper portions of the body when examinations are performed with surface coils, peripheral and deep regions also need careful attention during routine evaluation.

Aged↗
PubMedDate not supplied

Intraocular hemorrhage and mimicking lesions: role of gradient-echo and contrast-enhanced MRI.

Intraocular hemorrhage and mimicking lesions on precontrast spin-echo magnetic resonance images were examined with contrast material and/or gradient-echo pulse sequence. Twenty-two melanomas, nine retinoblastomas, four hemorrhages, one metastasis, and one toxocara endophthalmitis were examined. With contrast material, all tumors demonstrated enhancement, whereas hemorrhage did not. Retinoblastomas demonstrated a heterogeneous enhancement pattern. Computed tomography demonstrated corresponding intratumoral calcifications at the areas of no enhancement. Gradient-echo images demonstrated a heterogeneous pattern in the majority of the lesions compared to spin-echo images. However, relatively characteristic small round areas of signal drop-off representing calcification were observed in about half of the retinoblastomas.

Animals↗
PubMedDate not supplied

Vertebral body metastasis of glioblastoma multiforme with epidural mass formation. Contrast-enhanced MRI study.

A 35-year-old woman with left frontoparietal glioblastoma was subtotally resected twice and 1 year later demonstrated extracranial metastasis. Magnetic resonance imaging (MRI) demonstrated metastasis to the first thoracic vertebral body with epidural and paravertebral extension. Bone scintigrams of the spine appeared normal. The mechanisms and radiological findings of the extracranial metastasis of an astrocytic glioma are reviewed.

Adult↗
PubMedDate not supplied

Manganese intoxication during intermittent parenteral nutrition: report of two cases.

BACKGROUND AND METHODS: The administration of trace elements is thought to be needed in patients receiving long-term parenteral nutrition. Recently, manganese intoxication or deposition was documented in such patients. We report two cases of manganese intoxication during intermittent parenteral nutrition including manganese. Manganese had been administered for 4 years at a frequency of one or two times per week in one case and for 5 years at a frequency of one or two times per month in the other case. Both cases showed mild symptoms with headache and dizziness. One case had mild hepatic dysfunction and the other did not. The whole-blood manganese level increased in one case, but not in the other case. T1-weighted magnetic resonance images revealed symmetrical high-intensity areas in basal ganglia and thalamus in both cases. After the administration of manganese was stopped, these symptoms all disappeared and the magnetic resonance images abnormalities gradually improved in both patients. Mild long-term manganese intoxication is thus considered to occur regardless of the frequency of using a manganese supplement. CONCLUSIONS: Patients should be carefully monitored when receiving long-term parenteral nutrition including manganese, even when the manganese dose is small and the frequency of receiving a manganese supplement is low.

Adolescent↗
PubMedDate not supplied

MR imaging of human herpesvirus-6 encephalopathy after hematopoietic stem cell transplantation in adults.

BACKGROUND AND PURPOSE: Human herpesvirus-6 (HHV-6)-associated encephalopathy tends to develop in immunocompromised patients. Neurologic symptoms, such as disorientation, short-term memory loss, convulsion, coma, and hypopnea could occur, but they may be nonspecific. We retrospectively reviewed MR images of 6 adults with HHV-6-associated encephalopathy to study characteristic imaging findings that could be useful in making the diagnosis. MATERIALS AND METHODS: Between 2003 and 2005, we encountered 6 cases of HHV-6-associated encephalopathy (3 men and 3 women; age range, 36-55 years) in 3 hospitals. The diagnosis was made clinically according to the neurologic symptoms accompanied by high-level copies of HHV-6 DNA in CSF or peripheral blood by quantitative polymerase chain reaction without the detection of any other infectious pathogen. RESULTS: All 6 patients had abnormal hippocampus/amygdala findings on presentation, and no other regions were involved. In the early period (0-2 days from onset), abnormal high signal intensity on fluid-attenuated inversion recovery (FLAIR) imaging (2 of 3, 67%) and on diffusion-weighted images accompanied by apparent diffusion coefficient (ADC) reduction (2 of 2, 100%) were observed. In the middle period (3-30 days), abnormal low signal intensity on T1-weighted images (5 of 6, 83%) and abnormal high signal intensity on T2-weighted images (4 of 6, 67%) and FLAIR (5 of 6, 83%) were confirmed. In the late period (> 30 days), we saw the resolution of signal intensity abnormalities and the appearance of atrophic change (4 of 4, 100%) of the affected regions. CONCLUSION: HHV-6-associated encephalopathy in adults tends to affect the mesial temporal lobe. MR imaging is useful for detecting HHV-6 encephalopathy and distinguishing it from the other diseases of the central nervous system in immunocompromised patients.

Adult↗
PubMedDate not supplied

Leiomyosarcoma after retinoblastoma radiotherapy.

The CT and MR appearance of leiomyosarcoma in the left orbit in a 15-year-old girl is presented. This tumor developed after successful radiation therapy for bilateral retinoblastoma.

Adolescent↗
PubMedDate not supplied

MR imaging of malignant uveal melanoma: role of pulse sequence and contrast agent.

To determine the most sensitive pulse sequence and to clarify the role of each pulse sequence in the MR diagnosis of uveal malignant melanoma, noncontrast T1- and T2-weighted, and postcontrast T1-weighted, spin-echo images were compared blindly and independently by two experienced observers. Thirty uveal malignant melanomas, preselected by ophthalmoscopy and sonography for size greater than 2 mm, were examined with a 1.5-T superconducting MR unit with an orbital surface coil. Fifteen tumor studies were done after the patient was injected with gadopentetate dimeglumine. Postcontrast T1-weighted images were the most sensitive in detecting melanomas, demonstrating tumors 2 mm in height accurately on axial planes and 1.6 mm in height on combined orthogonal planes. The contrast-to-noise ratio between melanoma and vitreous fluid was greatest on postcontrast T1-weighted images (average, 72.1), followed by noncontrast T1-weighted images (average, 32.9), and then by T2-weighted images (average, -21.2). Postcontrast T1-weighted images also proved useful in differentiating melanomas from subretinal fluid collections when combined with noncontrast images. We conclude that postcontrast T1-weighted images are most helpful in detecting small uveal melanomas and in differentiating melanomas from subretinal fluid collections.

Contrast Media↗
PubMedDate not supplied

Gd-DTPA administered MR imaging of intracranial mass lesions: a comparison with CT and precontrast MR.

Magnetic resonance (MR) images of 13 intracranial mass lesions taken with the intravenous administration of gadolinium-DTPA were evaluated in comparison with precontrast computed tomography (CT), postcontrast CT, and precontrast MR. In the MR images taken with Gd-DTPA, tumor delineation improved in eight of 13 cases (62%) in comparison with precontrast MR images, and in seven of 13 cases (54%) in comparison with the overall evaluation of precontrast CT, postcontrast CT, and precontrast MR images. Tumor demarcation was unchanged in the remaining cases; no deterioration was observed with Gd-DTPA administration. MR imaging with Gd-DTPA should be performed to better evaluate the extent of intracranial mass lesions and to provide additional information.

Adult↗
PubMedDate not supplied

Aging factors and cardiovascular dimensions: a longitudinal study.

The effects of selected aging factors including body weight, blood pressure, and radiation dose on the cardiac and aortic arch transverse diameters, based on posteroanterior and lateral radiographs obtained 17 to 22 years apart were evaluated for 200 normal subjects. Increases in body weight and blood pressure caused increases in transverse cardiac diameter of 26% and 2%, respectively, but no appreciable effect on aortic arch transverse diameter. Radiation dose caused no significant effects. Effects of increases in body weight and blood pressure on cardiac and aortic arch transverse diameters with age ought not be overestimated in healthy adults.

Adult↗