Toshiyuki Okubo

Normal aging in the central nervous system: quantitative MR diffusion-tensor analysis.

The purpose of this study is to elucidate changes in mean diffusivity (ADC) and fractional anisotropy (FA) using MR diffusion tensor imaging (DTI) in the central nervous system during normal aging. We studied 50 normal volunteers (30 men, 20 women; mean age 44.8 +/- 14.0; age range, 21-69 years) without disorders affecting the central nervous system. The frontal, parietal white matter, lentiform nucleus, posterior limb of internal capsule, thalamus, genu and splenium of the corpus callosum were selected for investigation. There was no significant difference in ADC or FA between male and female or between the right and left hemisphere. A significant ADC increase with advancing age was observed in frontal white matter (P = 0.010) and lentiform nucleus (P = 0.022). A significant FA decline was found only in the genu of the corpus callosum (P < 0.001) with advancing age. Quantitative diffusion tensor analysis correlate with normal aging and may help in assessing normal age-related changes and serve as a standard for comparison with neurodegenerative disorders.

Congenital absence of the portal vein

Absence of the terminal portion of the portal vein and its intrahepatic branches was demonstrated in a 22-year-old woman with focal nodular hyperplasia (FNH) of the liver. Various imaging studies and angiography showed that the portal vein entered into the inferior vena cava just above the renal veins. The clinical and radiological features of this patient and nine previously reported cases of this entity are herein reviewed.

Line scan diffusion tensor MRI at low magnetic field strength: Feasibility study of cervical spondylotic myelopathy in an early clinical stage

To implement line scan diffusion tensor MR imaging (LSDTI) on a 0.2 Tesla MR imager, and investigate the findings in the spinal cord of patients with cervical spondylotic myelopathy in an early clinical stage.

Temporal changes of the apparent diffusion coefficients of water and metabolites in rats with hemispheric infarction: experimental study of transhemispheric diaschisis in the contralateral hemisphere at 7 tesla.

The purpose of the present study was to clarify the temporal changes of the apparent diffusion coefficients (ADCs) of cerebral metabolites during early focal ischemia using stimulated echo acquisition mode with short echo time at a 7 T magnet to assess the pathophysiology of the reduction in diffusion properties observed both in the ischemic cerebral hemisphere and in the contralateral hemisphere. The ADCs of metabolites in the infarcted hemisphere 1 hour and 3 hours after the onset of ischemia decreased with 25% and 29% for choline-containing compounds (Cho), 16% and 26% for creatine and phosphocreatine (Cre), and 19% and 19% for N-acetylaspartate (NAA), respectively, compared with the ADC values 2 hours later in the contralateral hemisphere. There were decreases in the ADC of Cho, Cre, and NAA with 21%, 7%, and 18% 8 hours later, respectively, in the noninfarcted hemisphere, which suggested transhemispheric diaschisis in rats with focal cerebral ischemia. The present study proposed that the diffusion characteristics of the brain metabolites might offer new insights into circulatory and metabolic alteration in the cerebral intracellular circumstance.

Corticospinal tracts by diffusion tensor tractography in patients with arteriovenous malformations.

Objective: To visualize the corticospinal tract (CST) in patients with arteriovenous malformations (AVMs) by using diffusion tensor tractography (DTT) and to confirm the clinical reliability of DTT in patients with AVMs. Methods: We performed DTT in 24 patients who had their AVMs near the CST. Tracts and AVMs were shown simultaneously, providing information on their spatial relationships. We also counted numbers of voxels in the DTT-CST at the level of the AVM. Results: DTT was visualized in 23 patients. In all 9 patients with hemiparesis, their DTT-CSTs were involved in the AVM or its surrounding lesion. Their volume of DTT-CST at the affected side was significantly decreased when compared with the contralateral side (P = 0.0469). All 14 patients whose DTT-CSTs were free from lesion had no hemiparesis. Conclusions DTT was safe and clinically applicable in patients with AVMs. DTT is recommended when an AVM is located near the corticospinal tract.

Visual Field Damage in Normal-tension Glaucoma Patients With or Without Ischemic Changes in Cerebral Magnetic Resonance Imaging

PurposeTo compare the pattern of visual field damage between normal-tension glaucoma (NTG) patients with signs indicative of ischemic changes and those NTG patients without signs of ischemic changes, using brain magnetic resonance imaging (MRI), in a single center, cross-sectional study.MethodsIn 94 consecutive NTG patients who were younger than 61 years old, brain MRI images were obtained using fluid-attenuated inversion recovery pulse sequences. The presence of signs indicative of ischemic changes in brain MRI images was decided separately by two neuroradiologists masked to the diagnosis and stage of glaucoma. Visual field testing was performed using the 30-2 program of the Humphrey Visual Field Analyzer. Between the patients with signs indicative of ischemic changes in brain MRI (ischemic group) and those without MRI signs (nonischemic group), total deviation (TD) at each test point less the average of TDs of the 30-2 program ([TD − TDmean])—was compared at each test point.ResultsSigns indicative of ischemic changes in brain MRI were found in 32 of the 94 patients (34.0%). Age, blood pressure, refraction, intraocular pressure, the average of TDs, mean deviation, and corrected pattern standard deviation were not significantly different between the ischemic (N = 32) and nonischemic (N = 62) groups (P > 0.2). [TD − TDmean] in the ischemic group was significantly smaller than that in the nonischemic group at 6 nonedge contiguous test points in the inferior pericentral to nasal field (P = 0.005–0.047).ConclusionNTG patients with signs indicative of ischemic changes in brain MRI had a relatively deeper depression in the inferior pericentral visual field.

In vitro validation of bioluminescent monitoring of disease progression and therapeutic response in leukaemia model animals.

PurposeThe application of in vivo bioluminescence imaging to non-invasive, quantitative monitoring of tumour models relies on a positive correlation between the intensity of bioluminescence and the tumour burden. We conducted cell culture studies to investigate the relationship between bioluminescent signal intensity and viable cell numbers in murine leukaemia model cells.MethodsInterleukin-3 (IL-3)-dependent murine pro-B cell line Ba/F3 was transduced with firefly luciferase to generate cells expressing luciferase stably under the control of a retroviral long terminal repeat. The luciferase-expressing cells were transduced with p190 BCR-ABL to give factor-independent proliferation. The cells were cultured under various conditions, and bioluminescent signal intensity was compared with viable cell numbers and the cell cycle stage.ResultsThe Ba/F3 cells showed autonomous growth as well as stable luciferase expression following transduction with both luciferase and p190 BCR-ABL, and in vivo bioluminescence imaging permitted external detection of these cells implanted into mice. The bioluminescence intensities tended to reflect cell proliferation and responses to imatinib in cell culture studies. However, the luminescence per viable cell was influenced by the IL-3 concentration in factor-dependent cells and by the stage of proliferation and imatinib concentration in factor-independent cells, thereby impairing the proportionality between viable cell number and bioluminescent signal intensity. Luminescence per cell tended to vary in association with the fraction of proliferating cells.ConclusionAlthough in vivo bioluminescence imaging would allow non-invasive monitoring of leukaemia model animals, environmental factors and therapeutic interventions may cause some discrepancies between tumour burden and bioluminescence intensity.

Imaging living mice using a 1‐T compact MRI system

To determine the feasibility of imaging living mice with a 1‐T compact MRI system and investigate appropriate imaging techniques for use in routine animal experiments.

Diffusion property in a hamartomatous lesion of neurofibromatosis type 1.

Though diffusion-weighted MRI has been applied to various intracranial lesions, few reports had been presented about cerebral hamartomatous lesions in patients with neurofibromatosis type 1 (NF1). In this study, we report the interval changes of apparent diffusion coefficient (ADC) in a presumed hamartomatous lesion. In our case, the ADC increased slightly over a 3 year period. This diffusion property may provide specific insight into the etiology of cerebral hamartomatous lesions observed in NF1.

Quantitative Assessment of Tendon Healing by Using MR T2 Mapping in a Rabbit Achilles Tendon Transection Model Treated with Platelet-rich Plasma.

PURPOSE To determine if magnetic resonance (MR) imaging T2 mapping can be used to quantify histologic tendon healing by using a rabbit Achilles tendon transection model treated with platelet-rich plasma (PRP). MATERIALS AND METHODS Experiments were approved by the Institutional Animal Care and Use Committee. The Achilles tendons of 24 New Zealand white rabbits (48 limbs) were surgically transected, and PRP (in the test group) or saline (in the control group) was injected into the transection site. The rabbits were sacrificed 2, 4, 8, and 12 weeks after surgery. Thereafter, T2 mapping and histologic evaluations were performed by using the Bonar scale. A mixed-model multivariate analysis of variance was used to test the effects of time and PRP treatment on the T2 value and Bonar grade, respectively. The correlation between the T2 value and Bonar grade was also assessed by using the Spearman correlation coefficient. RESULTS The Bonar scale values decreased in both groups during tendon healing. The T2 value also shortened over time (P < .001 for both groups). The T2 values were positively correlated with the Bonar grade (ρ = 0.78, P < .001). Both the T2 value and Bonar scale value were lower in the PRP group than in the control group at 4, 8, and 12 weeks; however, there was no significant effect of PRP treatment on the T2 value or Bonar grade. CONCLUSION The T2 value changes reflected histologic tendon healing. While T2 and Bonar grade were lower at all time points in tendons treated with PRP, there was no significant difference between the treatment and control tendons.