The efficacy of a voxel-based morphometry on the analysis of imaging in schizophrenia, temporal lobe epilepsy, and Alzheimer's disease/mild cognitive impairment: a review

Voxel-based morphometry (VBM) done by means of MRI have provided new insights into the neuroanatomical basis for subjects with several conditions. Recently, VBM has been applied to investigate not only regional volumetric changes but also voxel-wise maps of fractional anisotropy (FA) computed from diffusion tensor imaging (DTI). The aim of this article is to review the recent work using VBM technique in particular focusing on schizophrenia, temporal lobe epilepsy (TLE), and Alzheimer's disease (AD)/mild cognitive impairment (MCI). In patients with schizophrenia, VBM approach detects the structural brain abnormalities that appear normal on conventional MRI. Moreover, this technique also has the potential to emerge as a useful clinical tool for early detection and monitoring of disease progression and treatment response in patients with schizophrenia or AD/MCI. In TLE, VBM approach may help elucidate some unresolved important research questions such as how recurrent temporal lobe seizures affect hippocampal and extrahippocampal morphology. Thus, in the future, large cohort studies to monitor whole brain changes on a VBM basis will lead to a further understanding of the neuropathology of several conditions.     

Usefulness of Quantitative Susceptibility Mapping for the Diagnosis of Parkinson Disease

BACKGROUND AND PURPOSE:Quantitative susceptibility mapping allows overcoming several nonlocal restrictions of susceptibility-weighted and phase imaging and enables quantification of magnetic susceptibility. We compared the diagnostic accuracy of quantitative susceptibility mapping and R2* (1/T2*) mapping to discriminate between patients with Parkinson disease and controls.MATERIALS AND METHODS:For 21 patients with Parkinson disease and 21 age- and sex-matched controls, 2 radiologists measured the quantitative susceptibility mapping values and R2* values in 6 brain structures (the thalamus, putamen, caudate nucleus, pallidum, substantia nigra, and red nucleus).RESULTS:The quantitative susceptibility mapping values and R2* values of the substantia nigra were significantly higher in patients with Parkinson disease (P < .01); measurements in other brain regions did not differ significantly between patients and controls. For the discrimination of patients with Parkinson disease from controls, receiver operating characteristic analysis suggested that the optimal cutoff values for the substantia nigra, based on the Youden Index, were >0.210 for quantitative susceptibility mapping and >28.8 for R2*. The sensitivity, specificity, and accuracy of quantitative susceptibility mapping were 90% (19 of 21), 86% (18 of 21), and 88% (37 of 42), respectively; for R2* mapping, they were 81% (17 of 21), 52% (11 of 21), and 67% (28 of 42). Pair-wise comparisons showed that the areas under the receiver operating characteristic curves were significantly larger for quantitative susceptibility mapping than for R2* mapping (0.91 versus 0.69, P < .05).CONCLUSIONS:Quantitative susceptibility mapping showed higher diagnostic performance than R2* mapping for the discrimination between patients with Parkinson disease and controls.

The diagnosis of Parkinson disease (PD), a movement disorder with varying combinations of rest tremors, bradykinesia, rigidity, and postural instability, is based mainly on clinical assessments that do not yield great accuracy. One objective of noninvasive neuroimaging techniques in PD is to find markers that aid in the diagnosis, disease-progression monitoring, and long-term drug-impact evaluation.¹ MR imaging with rich tissue contrasts and high spatial resolution offers a unique value for probing PD brain structure and function.Particularly, there has been substantial interest in in vivo MR imaging of increased nigral iron content,^2,3 a pathophysiologic feature involved in the selective dopaminergic neurodegeneration of the substantia nigra in patients with PD.⁴ Iron likely stored in ferritin⁵ is highly paramagnetic and can be sensitized in MR imaging by using relaxation contrast (such as T2-weighted imaging) and susceptibility contrasts (such as T2*-weighted imaging and R2* [1/T2*] mapping).⁶ For quantitative study of brain iron, R2* mapping has been used,^7,8 demonstrating increased iron in the substantia nigra in patients with PD,^9–11 and a recent postmortem correlation study has demonstrated that the relationship with R2* can be linear in regions of more uniform iron deposition.¹² However, R2* mapping depends on field strength,¹³ contains substantial blooming artifacts that increase with TE,¹⁴ and generally relates to iron concentration in a complex way, varying from linear to quadratic.^15–17Recently, quantitative susceptibility mapping (QSM) has been developed to determine tissue magnetic susceptibility from gradient-echo data.^18–20 Because ferritin susceptibility is much stronger than other tissues in brains free of hemorrhages and aggregates of other metals, QSM can be used to quantify brain iron distribution.^21,22 Clinical data from patients with multiple sclerosis suggest that QSM is more sensitive than R2* mapping in detecting changes in multiple sclerosis brains.²³According to a previously published study using QSM, a significant difference was not found between patients with PD and healthy control subjects for the susceptibility value of the substantia nigra.²⁴ However, because only 9 patients were available for the previous study, the clinical potential of QSM has not been fully elucidated. Furthermore, the difference between QSM and the standard method for studying iron change, including R2* mapping, has not been evaluated in patients with PD. In this study, we tested the hypothesis that QSM is more sensitive than R2* mapping to pathologies in PD brains by comparing QSM and R2* values in 6 brain structures (the thalamus, putamen, caudate nucleus, pallidum, substantia nigra, and red nucleus) in patients with PD and healthy controls.     

No alterations of brain GABA after 6 months of treatment with atypical antipsychotic drugs in early-stage first-episode schizophrenia

We investigated the effects of atypical antipsychotic drugs on GABA concentrations in early-stage, first-episode schizophrenia patients. Sixteen (8 males, 8 females; age, 30 ± 11 years old) patients were followed up for six months. We also included 18 sex- and age-matched healthy control subjects. All patients were treated with atypical antipsychotic drugs (5 patients with risperidone, 5 patients with olanzapine, 4 patients with aripiprazole, and 2 patients with quetiapine). In all three regions measured (frontal lobe, left basal ganglia, and parieto-occipital lobe), no differences in GABA concentrations were observed in a comparison of pre-treatment levels and those six months after treatment. These results suggest that relatively short-term treatment with atypical antipsychotic drugs may not affect GABAergic neurotransmission; however, it is also possible that such treatment prevents further reductions in brain GABA levels in people with early-stage, first-episode schizophrenia.     

Intraarterial infusion chemotherapy and conformal radiotherapy for cancer of the mouth: prediction of the histological response to therapy with magnetic resonance imaging

Background: Although intraarterial chemotherapy has been used to treat head and neck cancers, some cases have shown poor response. If we can predict the response to this therapy on MRI, individual treatment plans may be altered to the most appropriate form of treatment.

Purpose: To evaluate whether MRI can predict the histological response to preoperative chemoirradiation in patients with cancer of the mouth.

Material and Methods: This study comprised of 29 consecutive patients with 30 oral cancers. All patients underwent tumor resection after intraarterial infusion chemotherapy and conformal radiotherapy. We compared the margin of the tumor, the presence of bone invasion, tumor area, and volume on pre- and post-treatment MRI with histological responses.

Results: Eighteen lesions showed an excellent response, nine exhibited a good response, and three a poor response. Only the tumor area on pretreatment T1-weighted images and the tumor area and volume on pretreatment enhanced T1-weighted images were significantly correlated with the histological response (P = 0.039, 0.008, and 0.016, respectively); smaller cancers showed better responses. The other factors were not significantly correlated with the histological responses.

Conclusion: MRI parameters, excluding initial tumor area and volume, were not predictive of the histological response of oral tumors to preoperative treatment.     

Preoperative embolization for meningeal tumors: evaluation of vascular supply with angio-CT

When evaluating vascular supply, a combined angiography and CT (angio-CT) system provides more accurate vascular anatomy than digital subtraction angiography. To the best of our knowledge, however, the application for intracranial tumors has not been described. We herein describe a technique of an angio-CT system for diagnosis of vascular anatomy of the feeding artery for preoperative embolization of meningeal tumors.     

Evaluation of Vascular Supply with Angio–Computed Tomography During Intra-Arterial Chemotherapy for Brain Tumors

We report the utility of a combined angiography and computed tomography (angio-CT) system in assessing drug distribution to the tumor during intra-arterial chemotherapy for metastatic brain tumors in a 65-year-old man. Although digital subtraction angiography did not clearly show tumor perfusion in two cerebellar tumors, angio-CT provided definite tumor perfusion in the complicated vascular territory, and anticancer agents were infused based on its findings. To our knowledge, however, this application for intra-arterial chemotherapy of brain tumors has not been previously described.     

Spinal MR findings in continuous epidural analgesia without infection

BACKGROUND AND PURPOSE: Spinal epidural abscesses are major complications of epidural anesthesia, and their MR features have been reported. In patients receiving continuous infusion via an epidural catheter, MR findings may mimic those of spinal epidural abscess in the absence of infection. The purpose of this study was to assess the spinal MR findings associated with continuous epidural anesthesia. METHODS: Spinal MR findings in five consecutive patients receiving continuous epidural anesthesia were retrospectively evaluated. Axial and sagittal T1- and T2-weighted spin-echo and contrast-enhanced fat-suppressed T1-weighted spin-echo images were obtained. Infection was ruled out on microbiologic analysis three patients and on follow-up in two. Each lesion was evaluated for its MR signal intensity, location, extent, delineation, and enhancement pattern. In three patients, follow-up MR imaging was performed within 5-150 days, and the images were compared. RESULTS: Posterior epidural lesions were identified in all five patients. The lesions were isointense to hypointense relative to the spinal cord on T1-weighted images, isointense relative to CSF on T2-weighted images, and well enhanced on enhanced T1-weighted images. The anomalous enhancement involved two to seven vertebral bodies. In one patient, the enhanced lesion slightly compressed the spinal cord. On follow-up MR imaging, the epidural lesions decreased in two patients and did not change in one. CONCLUSION: Continuous epidural anesthesia can result in MR findings similar to those of epidural abscess, even in the absence of infection.     

Transthyretin-related familial amyloid polyneuropathy: evaluation of CSF enhancement on serial T1-weighted and fluid-attenuated inversion recovery images following intravenous contrast administration

BACKGROUND AND PURPOSE: CSF enhancement on MR images after intravenous administration of gadolinium chelate, which mimics subarachnoid hemorrhage, has been reported. The purpose of this study was to determine whether CSF enhancement can be seen on serial MR images following administration of contrast material in patients with transthyretin-related familial amyloid polyneuropathy (FAP) and to assess other ancillary MR findings. METHODS: We serially studied T1-weighted and fluid-attenuated inversion recovery (FLAIR) images of the brain before, immediately after, and 3, 6, and 24 hours after contrast administration in 6 patients with genetically confirmed transthyretin-related FAP. By consensus, 2 radiologists assessed the presence, degree, and extent of enhancement of the CSF, leptomeninges, brain parenchyma, and other structures. Statistical analysis was performed to define the difference of the enhancement between the 2 MR imagings. RESULTS: In 3/6 patients with cysteine-for-tyrosine substitutions at position 114 (Tyr114Cys mutations), marked CSF enhancement was observed on the FLAIR images at 3 and 6 hours and on T1-weighted images at 3 hours after contrast administration. Although there was no significant difference between the 2 MR imagings, leptomeningeal enhancement for these 3 patients was evident only on FLAIR images. The labyrinth and vitreous body was also enhanced on postcontrast delayed MR images of these 3 patients. These enhancements were not observed in the other 3 patients with Val30Met mutation. In none of the 6 patients did images demonstrate parenchymal enhancement of the brain. CONCLUSION: In FAP patients with Tyr114Cys mutations, contrast material can leak into the CSF. This finding may depend on the subtype of FAP and be more evident with FLAIR images. The enhancement of the leptomeninges, labyrinth, and vitreous body was also seen in the patients.     

Pseudostenosis in vessels adjacent to intracranial aneurysms on volume-rendered 3D angiograms: a phantom study

RATIONALE AND OBJECTIVE: Among artifacts on three-dimensional (3D) angiograms, pseudostenosis in vessels adjacent to intracranial aneurysms has not been described. By using a phantom, artifacts seen in vessels adjacent to intracranial aneurysms on volume-rendered 3D angiograms were assessed. MATERIALS AND METHODS: Using a 3D angiography system and a C-arm sweep, digital images were obtained with a 512 x 512 matrix. Rotation was 30 degrees /second, and frame rate was 30 frames/second. Phantom aneurysms were designed to simulate intracranial saccular aneurysms and their parent arteries. Phantoms, consisting of a cylinder (inner diameter, 2 or 4 mm) and spheres, 10, 7, 5, 3, or 2 mm in diameter, were placed at 0 degrees and 45 degrees to the axis of rotation. Two radiologists consensually recorded their findings regarding the presence and location of stenosis and its relationship to the angle of rotation. The maximum percentage of stenosis in the pseudostenosis area was measured on multiplanar reconstruction images by using a workstation computer. RESULTS: Pseudostenosis was observed in the cylinder adjacent to the sphere at both 0 degrees and 45 degrees angles; it was on a plane perpendicular to the axis of rotation. Pseudostenosis was most obvious with 10-mm spheres; it was not seen when spheres were 3 mm or less in diameter. The maximum percentage of stenosis of the pseudostenosis increased with sphere size. CONCLUSION: On volume-rendered 3D angiograms, pseudostenosis was seen in the cylinder adjacent to the sphere. The artifact lay on a plane perpendicular to the axis of rotation, and sphere size affected the artifact.