Isamu Ohashi

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

To evaluate the use of apparent diffusion coefficient (ADC) measurements based on diffusion‐weighted MRI (DWI) to assess stage of liver disease.

Relationship between bone marrow cellularity and apparent diffusion coefficient.

This study was performed to determine if there is a relationship between apparent diffusion coefficient (ADC) and cellularity of bone marrow of the posterior ilium. Four groups of various marrow cellularity underwent diffusion‐weighted echo‐planar imaging: 1) adults with normal hypocellularity (21 patients); 2) adults with normal normocellularity (13 patients); 3) young children with normal hypercellularity (5 patients); and 4) adults with lymphoma‐related hypercellularity (3 patients). In all adults, marrow cellularity was confirmed by uni‐or bilateral bone marrow biopsies. In children, the iliac marrow was presumed hypercellular because of their ages. A total of 66 ADC values of bone marrow calculated from diffusion‐weighted images with b‐values of 30 and 300 seconds/mm2 was evaluated. Hypercellular marrow (normal and lymphoma‐related) showed the highest mean ADC, and hypocellular the lowest ADC. Statistically significant differences were found between three groups of normal marrow: hypocellular, normocellular, and hypercellular. There is a positive correlation between ADC and cellularity of bone marrow. J. Magn. Reson. Imaging 2001;13:757–760.

Anisotropic diffusion in kidney: Apparent diffusion coefficient measurements for clinical use

The purpose of this study was to evaluate anisotropy of the kidney by measurements of the apparent diffusion coefficient (ADC) using commercially available magnetic resonance (MR) imaging. Fifty‐one consecutive patients underwent diffusion‐weighted echoplanar MR imaging of the upper abdomen with five different strengths of motion probing gradients (b = 1.51, 55.3, 36.6, 317, and 932 sec/mm2) applied along the z‐axis. Four ADC values for the upper pole and central portion of the kidney were calculated from four different b‐value ranges and compared. The ADCs for the kidney calculated in the lower b‐value ranges were significantly higher than those in the higher ranges. The ADCs for the upper pole portion were significantly higher than those for the central portion except for one in the highest b‐value range. Diffusion in the kidney is anisotropic, probably due to the kidneys radially oriented structures such as renal vessels and tubules. J. Magn. Reson. Imaging 2000;11:156–160.

Functional evaluation with intravoxel incoherent motion echo-planar MRI in irradiated salivary glands: a correlative study with salivary gland scintigraphy.

The purpose of this study was to determine the relationship between the apparent diffusion coefficient (ADC) measured on intravoxel incoherent motion (IVIM) echo‐planar magnetic resonance imaging (MRI) and salivary gland function. Twenty‐one patients with head and neck malignancies underwent MRI and salivary gland scintigraphy before and after radiotherapy. Based on the scintigraphic results, each major salivary gland was classified into two groups (dysfunctional and functional) and ADCs measured on IVIM MRI were compared between the two groups. Furthermore, the relationship of ADC to scintigraphic parameters, maximum accumulation (MA), and the uptake ratio (UR), were analyzed. ADCs of the dysfunctional group decreased significantly after radiotherapy (P < .01), whereas those of the functional group showed no significant change. Furthermore, positive correlations were found between the ADC ratio and both MA (P < .005) and UR (P < .001). ADC measurement on IVIM echo‐planar MRI is a potentially useful means of evaluating salivary gland function. J. Magn. Reson. Imaging 2001;14: 223–229.

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

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.

Differential diagnosis of early homogeneously enhancing hepatocellular carcinoma and hemangioma by two-phase CT.

PURPOSE Our goal was to differentiate between early homogeneously enhancing hepatocellular carcinoma (HCC) and hemangioma by two-phase CT. METHOD Two phase images of 51 HCCs and 28 hemangiomas showing homogeneous high attenuation in the first series (arterial dominant phase) were reviewed. Enhancement patterns of the lesions in the second series (parenchymal phase) were classified as homogeneous high, peripheral high, iso-, and low attenuation. The attenuation values of all and the enhancement values of some (21 HCCs and 18 hemangiomas) in the first series were calculated. RESULTS Although low and peripheral high attenuation patterns were seen during the second series only in HCCs (n = 35), which could be used to correctly diagnose HCC, other nonspecific patterns were demonstrated in both HCCs (n = 16) and hemangiomas (n = 28). The attenuation values of 49 of the 51 HCCs and 5 of the 28 hemangiomas were below 130 HU on the first series. The enhancement values of all 21 HCCs and 3 of 18 hemangiomas were below 70 HU. Combining the enhancement patterns with a borderline attenuation value of 130 HU or borderline enhancement value of 70 HU yielded overall accuracies of 94 and 92%, respectively. CONCLUSION The combined criteria (enhancement pattern plus attenuation or enhancement value) were useful for differentiating between early homogeneously enhancing HCCs and hemangiomas.

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

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/mm2) in comparison with three‐phase dynamic MRI.

Fibromuscular disease of the brachial artery with digital emboli treated effectively by transluminal angioplasty

We present a 45-year-old male with fibromuscular dysplasia (FMD) of the left brachial artery causing microemboli with digital ischemia. The angiographic diagnosis was medial fibroplasia. Treated with percutaneous transluminal angioplasty (PTA), the corrugated arterial wall was made smooth and production of new thrombi apparently stopped, as 3.5 years after PTA the patient has had no recurrence. Although FMD of the brachial artery is rarely encountered, PTA seems to be an effective treatment as an alternative to surgical interposition grafting.

Aberrant left gastric vein demonstrated by helical CT

PURPOSE Our goal was to describe the CT findings of aberrant left gastric vein (ALGV) and to evaluate the clinical significance of this vein. METHOD Four patients in whom ALGVs were demonstrated by helical CT were examined. Each patient had either intrahepatic cholangiocarcinoma, cirrhosis with gastric varices, chronic hepatitis, or nonspecific abdominal pain. All patients underwent two phase helical CT, and the patient with cholangiocarcinoma underwent CT during arterial portography, and 3D images of the abdominal veins were obtained. RESULTS In all patients, the ALGVs ran along the hepatogastric ligament and were directly connected with the left portal branch. In the patient with cholangiocarcinoma, the portal vein had severe stenosis by tumor invasion, and both the ALGV and the aberrant right gastric vein functioned as a collateral pathway of the portal flow into the liver. In the patient with cirrhosis, dilated ALGV with hepatofugal flow caused gastric varices. CONCLUSION The ALGV is directly connected with the left portal branch and may play an important role in the collateral pathway of the portal system.

Long-term follow-up using 18F-FDG PET/CT for postoperative olfactory neuroblastoma.

PurposeThe present study evaluated the usefulness of postoperative fluorine-18 fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in the management of olfactory neuroblastoma (ONB). Materials and methodsTen patients (eight men and two women; mean age, 48.5 years) with histologically confirmed ONB who underwent craniofacial resection were retrospectively included in this study. A total of 42 whole-body 18F-FDG PET/CT scans for postoperative surveillance or restaging were reviewed. The mean time from operation until the PET/CT scan was 42.1 months. We evaluated the 18F-FDG uptake and the presence of recurrent lesions during the follow-up period and compared the PET/CT results with the results of MRI and clinical examination (endoscopy). ResultsSeven of the 10 patients had 24 recurrent lesions, and 18 of these recurrent lesions (seven local recurrences, eight cervical lymph node metastases, one intracranial metastasis, and two distant metastases) were 18F-FDG positive (75.0%). Three local recurrences and three intracranial metastases were false negative and were detected by endoscopy and MRI, respectively. The mean time from operation until recurrence was 51.4 months, and 17 lesions (70.8%) occurred more than 2 years after the initial operation. ConclusionAlthough 18F-FDG PET/CT is useful for the detection of postoperative recurrences of ONB, long-term follow-up combined with endoscopy and MRI is mandatory.