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We attempted to assess the feasibility of a 1.6-mm isotropic voxel diffusion tensor imaging (DTI) tractography at 3T in visualizing nerve bundles in the limbic system. We examined 20 healthy volunteers by conventional DTI with a voxel size of 1.6 × 1.6 × 3.0 mm and by high-resolution DTI with a voxel size of 1.6 × 1.6 × 1.6 mm and generated tractographs of three limbic nerve bundles: the fornix, cingulum, and uncinate fasciculus. We visually assessed whether these bundles reached their targets and compared their diffusion parameters between the two techniques. The entire pathways of the fornix, cingulum, and uncinate fasciculus were more readily visualized by high-resolution DTI than by conventional DTI. Among these, the fimbria of the fornix and the uncinate fasciculus adjacent to the temporal pole were identified more frequently by high-resolution DTI (visualization rate 83 and 100%, respectively) than by conventional DTI (visualization rate 63 and 83%, respectively) at a statistical significance of P

Object Preoperative planning for meningiomas requires information about tumor consistency as well as location and size. In the present study the authors aimed to determine whether the fractional anisotropy (FA) value calculated on the basis of preoperative magnetic resonance (MR) diffusion tensor (DT) imaging could predict meningioma consistency. Methods In 29 patients with intracranial meningiomas, MR DT imaging was performed preoperatively, and the FA values of the tumors were calculated. Tumor consistency was intraoperatively determined as hard or soft, and the histological diagnosis of the tumor was established. Results Of the 29 tumors, 11 were classified as hard and 18 as soft. The FA values of fibroblastic meningiomas were significantly higher than those of meningothelial meningiomas (p = 0.002). The FA values of hard tumors were significantly higher than those of soft tumors (p = 0.0003). Logistic regression analysis demonstrated that the FA value was a significant independent predictor of tumor consistency (p = 0.007). Conclusions The FA value calculated from preoperative MR DT imaging predicts meningioma consistency.

Purpose: We used a whole-brain, isotropic-voxel acquisition technique to improve the geometric distortion in diffusion-weighted (DWI) and diffusion tensor imaging (DTI) in coronal directions, which is remarkable at high magnetic fields. Materials and Methods: We performed magnetic resonance imaging of 17 healthy volunteers using a 3T scanner and obtained coronal DWI/DTI as well as coronal images that were reformatted from isotropic volume data acquired by 1.6-mm-thick axial DWI/DTI. We visually evaluated the degree of image distortion and quantitated the findings by co-registration analysis. Results: In-plane geometric distortions in coronal DWI/DTI, particularly at the frontal base and medial temporal lobe, were dramatically diminished when the isotropic-voxel acquisition technique was used. Quantitative measurement revealed a reduction in areas of misregistration, but not their absence, in reformatted coronal images, mainly because of distortion in the anteroposterior direction in the source images. Conclusion: The isotropic-voxel DWI/DTI technique enabled acquisition of coronal images that represented anatomical details accurately with permissible spatial distortion while maintaining spatial resolution, even at 3T.

Background and Purpose— Cerebrovascular reactivity (CVR) to acetazolamide is a key parameter in determining the severity of hemodynamic impairment in patients with major cerebral artery occlusive disease. Perfusion-weighted MRI (PW MRI) can measure the cerebral blood volume (CBV) as an indicator of hemodynamic impairment. CBV measured by PW MRI was compared with CVR measured by positron emission tomography (PET). Methods— Twelve normal subjects and 17 patients with major cerebral artery occlusive disease underwent PW MRI and PET. The images were coregistered with 3-dimensional spoiled gradient-recalled acquisition images. Quantitative PW MRI-CBV maps were generated using the indicator dilution method with arterial input function. One large cortical region of interest for each unilateral middle cerebral artery territory was determined on each image. PET-CVR was calculated by measuring cerebral blood flow before and after acetazolamide challenge. Results— A significant negative correlation was observed between PW MRI-CBV and PET-CVR ( r =−0.713; P Conclusions— The PW MRI-CBV method can simply and accurately identify patients with hemodynamic impairment without exposure to ionizing radiation.

Purpose: To investigate age-related changes in the locus ceruleus (LC) in healthy subjects using neuromelanin magnetic resonance (MR) imaging at 3 Tesla. Methods: We examined 64 healthy volunteers (aged 23 to 80 years) using neuromelanin-sensitive T1-weighted images and measured the contrast of areas of high signal intensity corresponding to the LC. Results: A pair of punctate areas of high signal intensity that represented neuromelanin within the noradrenergic neurons of the LC was easily recognized in all subjects. The contrast ratio of the LC to the adjacent pontine tegmentum increased to the age of 40 to 59 years and gradually and significantly decreased in elderly subjects. This correlates well with pathologically proven age-related changes in neuromelanin content within the LC. Conclusion: Age-related variance should be considered when determining the existence of abnormalities in the LC.

The temperature change of the fractional dissociation of imidazole (alpha-imidazole) in resting human lower leg muscles was measured noninvasively using (1)H-nuclear magnetic resonance spectroscopy at 3.0 and 1.5 T on five normal male volunteers aged 30.6 +/- 10.4 yr (mean +/- SD). Using (1)H-nuclear magnetic resonance spectroscopy, water, carnosine, and creatine in the muscles could be simultaneously analyzed. Carnosine contains imidazole protons. The chemical shifts of water and carnosine imidazole protons relative to creatine could be used for estimating temperatures and alpha-imidazole, respectively. Using the chemical shift, the values of temperature in gastrocnemius (Gast) and soleus muscles at ambient temperature (21-25 degrees C) were estimated to be 35.5 +/- 0.5 and 37.4 +/- 0.6 degrees C (means +/- SE), respectively (significantly different; P0.01). The estimated values of alpha-imidazole in these muscles were 0.620 +/- 0.007 and 0.630 +/- 0.013 (means +/- SE), respectively (not significant). Alternation of the surface temperature of the lower leg from 40 to 10 degrees C significantly changed the temperature in Gast (P0.0001) from 38.1 +/- 0.5 to 28.0 +/- 1.2 degrees C, and the alpha-imidazole in Gast decreased from 0.631 +/- 0.003 to 0.580 +/- 0.011 (P0.05). However, the values of alpha-imidazole and the temperature in soleus muscles were not significantly affected by this maneuver. These results indicate that the alpha-imidazole in Gast changed significantly with alternation in muscle temperature (r = 0.877, P0.00001), and its change was estimated to be 0.0058/ degrees C.

Background: The efficacy of surgical evacuation in patients with intracerebral hemorrhage (ICH) remains unclear for recovery of motor function. The relationship between improvement of motor function outcome and sequential change of fractional anisotropy (FA) values was investigated in patients with ICH, to explore whether motor function outcome can be predicted in the early phase. Indication of the surgical hematoma evacuation was also considered. Methods: This prospective study included 23 patients with ICH. All patients underwent diffusion tensor imaging to measure the FA value five times: within 3 days, day 14, day 30, day 60, and day 90 after the onset. The regions of interest were determined on the b = 0 step of the echo planar imaging scans in the bilateral cerebral peduncles and were automatically transferred onto the FA images. The FA value was then calculated for each patient. Patients were divided into good and poor recovery groups according to the motor function outcome on day 90. Results: The mean FA value of the poor recovery group gradually decreased until day 90, but remained unchanged in the good recovery group. The mean FA value on day 3 was significantly higher (p < 0.001) in the good recovery group (0.745 ± 0.0073) than in the poor recovery group (0.682 ± 0.0090). Receiver operating characteristic curve analysis showed that the FA value on day 3 could predict motor function outcome with a sensitivity of 100% and a specificity of 77.8% at an FA value of 0.7 on day 3. Conclusion: The main finding of this study was that the FA values of the cerebral peduncle on the pathological side in patients with ICH on day 3 could predict the motor function outcome on day 90.

Background Magnetic resonance imaging can provide a preoperative diagnosis of pontine glioma, but the findings sometimes do not correspond with the clinical symptoms. We describe 2 cases of pontine gliomas who did not present with motor and sensory disturbance. Case Report Three-dimensional anisotropy contrast (3DAC) imaging was used to assess the neuronal tracts in 2 patients with pontine gliomas. Conventional MR imaging depicted markedly abnormal findings of abnormally high or heterogeneous signal intensity in the pons in 2 cases. In contrast, 3DAC imaging obviously showed the corticospinal and spinothalamic tracts and cerebellar peduncles without destruction by tumors. Conclusion Three-dimensional anisotropy contrast imaging provides more information about damage to the neuronal tracts in cases of pontine gliomas than other MR imaging techniques. This technique may be used for preoperative mapping of the tumor and its relationship to the tracts, thus, providing an accurate road map for tumor resection.