PubMed Health⌕ Search

Biomedical subjects

Isamu Ohashi

Publications and source records attributed to Isamu Ohashi.

9 recordsLinked to original sources
PubMed2005

Apparent diffusion coefficient measurements with diffusion-weighted magnetic resonance imaging for evaluation of hepatic fibrosis.

PURPOSE: To evaluate the use of apparent diffusion coefficient (ADC) measurements based on diffusion-weighted MRI (DWI) to assess stage of liver disease. MATERIALS AND METHODS: A total of 31 patients who underwent both a liver biopsy and DWI and 132 patients who only underwent DWI were enrolled. Biopsy specimens were scored for fibrosis and necroinflammation according to the Knodell histology activity index (HAI). The 31 patients consisted of 21 patients with chronic hepatitis and 10 with cirrhosis (Child-Pugh stage A in nine and stage B in one), and the 132 patients consisted of 56 patients with cirrhosis (Child-Pugh stage A in 41, stage B in 10, and stage C in five), 42 with chronic hepatitis, and 34 with normal liver function. The ADCs in the liver parenchyma were measured using DWI with relatively low b factors (b = 0.01 and 128.01 seconds/mm(2)) and were compared among the HAI scores and among patients with cirrhosis, chronic hepatitis, and normal liver function. RESULTS: The ADCs decreased as the fibrosis score in the HAI increased, and the correlation was statistically significant (P < 0.0001). No relationship between the ADCs and the necroinflammation scores in the HAI was found. The ADCs decreased as the stage of liver disease progressed or as the Child-Pugh stage progressed, and these relationships were statistically significant (P < 0.0001). CONCLUSION: ADC measurements are potentially useful for the evaluation of fibrosis staging in the liver.

Adult↗
PubMed2004

Long-term change in size of cerebral infarction: predictive value of brain perfusion SPECT using statistical parametric mapping.

A focus of infarction is surrounded by hypoperfused areas. The present study was undertaken to examine the long-term changes in the size of infarcts, the relationship between the size of an infarct and the extent of the surrounding hypoperfused areas, and the background of such changes. The subjects of this study were 11 patients with ischemic lesions of the brain who had undergone brain SPECT ((99m)Tc-ethyl cysteinate dimer) within 1 week after initial MRI, and who underwent MRI again more than half a year later. Statistical parametric mapping (SPM) was conducted to detect significantly hypoperfused areas on the SPECT images. Relative size of significantly hypoperfused areas on SPM and infarcts on T(2)-weighted MR images were measured. The patients were divided into two groups based on the percentage of the infarct's size relative to the size of the surrounding hypoperfused areas (75-125 and 0-39%). Infarcts in the '75-125%' group showed little change in size, while in the '0-39%' group infarcts increased slowly until it reached the same rate as the former group. All patients with infarct in the '0-39%' group were noted to have severe stenosis of the internal carotid arteries bilaterally. Patients having severe stenosis of the internal carotid artery often had a slowly enlarging infarct. SPM seems to be useful in predicting the ultimate size of the infarct.

Adult↗
PubMed2004

Simple new technique for sonographic measurement of the thyroid in neonates and small children.

PURPOSE: The aim of this study was to determine whether the ratio of the thyroid width (Th) to the trachea width (Tr) is a useful technique for sonographic estimation of thyroid size in neonates and small children. METHODS: We prospectively performed sonographic examination of the thyroid gland in 30 pediatric subjects ranging in age from 1 week to 12 years. The sum of the maximum width of the left thyroid lobe and the maximum width of the right lobe was considered the Th. Each subject's thyroid was classified as small, normal sized, or large on the basis of the Th value in reference to the subject's body height. The ratios of the Th to the Tr were then calculated and compared among the 3 groups by 1-way analysis of variance. Correlation and regression analyses were performed to determine the correlation between body height and Tr. A p value of less than 0.05 was considered significant. RESULTS: The mean Th/Tr ratios (+/- standard deviations) for the 3 groups were as follows: small, 1.25 +/- 0.19; normal sized, 2.09 +/- 0.19; and large, 4.10 +/- 2.42. The difference in the Th/Tr ratios between the 3 groups was statistically significant (p < 0.0001). A significant positive correlation was found between Tr and body height (p < 0.001; r = 0.85). CONCLUSIONS: The Th/Tr ratio is a simple, practical parameter for estimating the size of the thyroid gland in neonates and small children.

Anthropometry↗
PubMed2004

Differentiation between completely hyalinized uterine leiomyomas and ordinary leiomyomas: three-phase dynamic magnetic resonance imaging (MRI) vs. diffusion-weighted MRI with very small b-factors.

PURPOSE: To assess the possibility of differentiating between completely hyalinized leiomyomas and ordinary leiomyomas by using diffusion-weighted (DW) magnetic resonance imaging (MRI) (DWI) employing very small b-factors (b = 1.51 and 55.3 seconds/mm(2)) in comparison with three-phase dynamic MRI. MATERIALS AND METHODS: The subjects were 25 patients with 52 histopathologically confirmed uterine leiomyomas. All leiomyomas were divided into two histopathologic subtypes (5 completely hyalinized leiomyomas and 47 ordinary leiomyomas). For each leiomyoma, the enhancement index (EI) at three-phase dynamic MRI and apparent diffusion coefficient (ADC) were obtained and then compared. RESULTS: The EIs at second and third dynamic phases clearly differentiated the two types of leiomyomas without overlap of values. ADCs also clearly differentiated the two types of leiomyomas without overlap of values. Moreover, there were significant positive correlations between ADCs and EIs at all dynamic phases (r = 0.41-0.50, P < 0.01). CONCLUSION: Not only three-phase dynamic MRI but also DWI with very small b-factors could be useful for differentiating completely hyalinized leiomyomas from ordinary leiomyomas.

Adult↗
PubMed2004

Determination of the depth of 50% of maximum ionization, I50, for electron beams by the divided difference method.

A new characterization of depth-ionization parameters for electron beams is empirically deduced from our data analysis based on the divided difference method (the DD method), which employs the numerical differential of an ionization curve. The important feature of the present method is that it does not necessarily require normalized percent depth-ionization (NPDI) data. The depth of 50% of maximum ionization, I50, which is an important parameter for electron beam dosimetry, can be deduced from the analysis of an unnormalized (or partial) depth-ionization (UDI) curve obtained over a short interval of depth. The values of I50 determined by the DD method are in agreement to within 0.1 mm for energies of 4, 6, and 9 MeV, compared with the ones determined by the TG-51 protocol method (or the conventional method), and the difference was 0.9 mm for 12 and 15 MeV. The dose at the reference depth, dref, calculated from I50 by the DD method, is found to be in agreement with TG-51 to within 0.1%. The field size dependence of the DD method using UDI data was studied for three field sizes: 6 x 6, 10 x 10, and 20 x 20 cm2. For all energies, the discrepancies of I50 as determined by both methods were 0.9 mm on average for the 6 x 6 cm2 fields and 0.6 mm for the other two field sizes. This dependence was remarkable for 6 x 6 cm2 fields for 12 and 15 MeV, and the discrepancies shown by the DD method were 1.2 mm for 12 MeV and 1.8 mm for 15 MeV, respectively. Since the reference field size in clinical dosimetry is usually 10 x 10 cm2, this dependence will not affect clinical dosimetry. The DD method could be an alternative option for checking beam quality in dose calibration.

Algorithms↗
PubMed2004

Triple-phase dynamic MRI of intratumoral vessel density and hyalinization grade in uterine leiomyomas.

OBJECTIVE: Our purpose was to clarify the relationship between the tissue vascularity shown on triple-phase dynamic MRI and the number of intratumoral vessels and degree of hyalinization, which are two histopathologic changes in leiomyoma. SUBJECTS AND METHODS. The subjects were 10 premenopausal patients with 20 leiomyomas who had undergone surgery without preoperative gonadotropin-releasing hormone analogue treatment. Intratumoral vessel density was determined by the mean number of intratumoral vessels with at least one smooth-muscle layer in the optic fields magnified 100 times. Hyalinization grade was determined by the severity of hyalinization, histopathologically classified in three grades. The enhancement index (EI) of the leiomyoma was calculated using the formula EI(t) = [S(t) - S(0)] / S(0), where S(0) is the signal intensity on pre-enhanced T1-weighted images and S(t) is the signal intensity on each dynamic phase image (t = 20, 60, and 180 sec) [corrected]. The histopathologic parameters of intratumoral vessel density and hyalinization grade were compared with the enhancement indexes obtained from the triple-phase dynamic MRI. RESULTS: We found positive correlations between intratumoral vessel density and EI(60) and between intratumoral vessel density and EI(180) (in both cases, p = 0.0028 and r = 0.69). We found significant differences among the mean enhancement indexes for each hyalinization grade at all dynamic phases (p < 0.01). The leiomyomas with lower intratumoral vessel densities tended to show greater hyalinization. CONCLUSION: Our results showed that leiomyomas with only slight hyalinization or with abundant vessels were well enhanced, but the leiomyomas with severe hyalinization enhanced poorly.

Adult↗
PubMed2003

MR imaging of the thyroid: correlation between apparent diffusion coefficient and thyroid gland scintigraphy.

PURPOSE: To evaluate the usefulness of echo-planar MR imaging for assessing the thyroid function and confirm the clinical use of MR imaging for thyroid diseases. MATERIALS AND METHODS: Thirty-four patients with a variety of thyroid disorders (24 Graves disease; five subacute thyroiditis; five Hashimoto thyroiditis) were examined using T1-, T2-, and diffusion-weighted magnetic resonance (MR) imaging and thyroid scintigraphy with Tc-99m pertechnetate. RESULTS: The ADC values obtained from the diffusion-weighted images of the patients with Graves disease were significantly higher than those of patients with subacute hyroiditis and Hashimoto thyroiditis, though no difference among those disorders was observed on T1- and T2-weighted images. Based on the ADC value, anisotropy was not observed in the thyroid gland. An ADC value of 1.82 x 10(-3) mm(2)/second or higher indicated the presence of Graves disease (sensitivity 75%, specificity 80%). CONCLUSION: Diffusion-weighted MR images may be of value for the diagnosis of thyroid diseases and could be clinically important in the evaluation of thyroid function.

Diffusion Magnetic Resonance Imaging↗
PubMed2003

Computed tomography-guided transarterial chemoembolization as the initial therapy for hepatocellular carcinoma: experience of 75 cases in a single institute.

We present the survival rates of 75 nonruptured hepatocellular carcinoma cases initially treated with computed tomography-guided transarterial chemoembolization in a single institute. The 1-, 3-, and 5-year survival rates were 93.9%, 74.7%, and 47.4% in 50 Child's A cases; 75.0%, 43.6%, and 6.8% in 20 Child's B cases; and 60.0%, 40.0%, 0.0% in 5 Child's C cases, respectively. The 1-, 3-, and 5-year survival rates of the 38 estimated resectable hepatocellular carcinoma cases (Child's A, tumors limited in a single lobe) were 94.7%, 82.0%, and 44.6%, respectively. The 1-, 3-, and 5-year survival rates of the 41 cases with estimated indication for percutaneous ethanol injection therapy (tumors less than 3 cm in diameter and three or fewer in number) were 96.8%, 84.6%, and 55.5% in 31 Child's A cases; and 90.0%, 46.7%, and 0% in 10 Child's B cases, respectively. In conclusion, computed tomography-guided transarterial chemoembolization is an excellent primary therapy for hepatocellular carcinoma.

Adult↗