Insight on AV-45 binding in white and grey matter from histogram analysis: a study on early Alzheimer’s disease patients and healthy subjects

Purpose

AV-45 amyloid biomarker is known to show uptake in white matter in patients with Alzheimer’s disease (AD), but also in the healthy population. This binding, thought to be of a non-specific lipophilic nature, has not yet been investigated. The aim of this study was to determine the differential pattern of AV-45 binding in white matter in healthy and pathological populations.

Methods

We recruited 24 patients presenting with AD at an early stage and 17 matched, healthy subjects. We used an optimized positron emission tomography-magnetic resonance imaging (PET-MRI) registration method and an approach based on an intensity histogram using several indices. We compared the results of the intensity histogram analyses with a more canonical approach based on target-to-cerebellum Standard Uptake Value (SUVr) in white and grey matter using MANOVA and discriminant analyses. A cluster analysis on white and grey matter histograms was also performed.

Results

White matter histogram analysis revealed significant differences between AD and healthy subjects, which were not revealed by SUVr analysis. However, white matter histograms were not decisive to discriminate groups, and indices based on grey matter only showed better discriminative power than SUVr. The cluster analysis divided our sample into two clusters, showing different uptakes in grey, but also in white matter.

Conclusion

These results demonstrate that AV-45 binding in white matter conveys subtle information not detectable using the SUVr approach. Although it is not more efficient than standard SUVr in discriminating AD patients from healthy subjects, this information could reveal white matter modifications.     

Differential diagnosis of infarct-like intracranial ectopic germinomas and subacute lacunar infarct on susceptibility-weighted imaging

Purpose:

To determine the efficacy of susceptibility‐weighted imaging (SWI) in the differential diagnosis between basal ganglia (BG) infarct‐like early stage intracranial ectopic germinomas (IEGs) and subacute lacunar infarct (SLI).

Materials and Methods:

Six children with early stage BG IEGs displaying an infarct‐like episode proven by pathology and eight children with BG SLI proven by clinic and vascular imaging were investigated retrospectively. On SWI, the contrast‐to‐noise ratio (CNR) in abnormal signal intensity regions was calculated and compared between the two groups.

Results:

For both IEGs and SLI the BG lesions were invisible or showed slight hyperintensity/hypointensity on T1‐weighted images and diffusion‐weighted images, patchy slight hyperintensity on T2‐weighted images without mass effect, and variable enhancement on postcontrast magnetic resonance imaging (MRI). On SWI, obvious hypointensity in BG lesions and pineal gland (PG) was found in IEG patients but unremarkable in SLI patients. The CNRs of BG lesions and PG were significantly higher in IEG patients compared with those in SLI patients (P < 0.01).

Conclusion:

SWI is useful in differentiating IEGs from SLI when clinical symptoms and conventional MRI manifestations overlap in these two conditions. PG may be involved with tumor, although it is normal on conventional MRI in patients with IEGs. J. Magn. Reson. Imaging 2012;36:92–98. © 2012 Wiley Periodicals Inc.     

Breathhold‐regulated blood oxygenation level‐dependent (BOLD) MRI of human brain at 3 tesla

Purpose:

To investigate the cerebrovascular response to repeated breathhold challenges using blood oxygenation level‐dependent (BOLD) MRI at 3T and compare the results with previous data at 1.5T.

Materials and Methods:

Six normal volunteers and six patients with brain tumors were recruited for this 3T study. For the normal group, BOLD MRI during repeated breathholds of different durations (five to 30 seconds) were acquired. Maximum signal change, full‐width at half‐maximum (FWHM) and onset time (defined as the time to the first half‐maximum) were determined by curve fitting. The fractional activation volume was also calculated. Patients performed a 10‐ or 15‐second breathhold paradigm according to individual capability.

Results:

Significant BOLD signal increases in the gray matter for a breathhold period as short as 5 seconds at 3T, instead of 10 seconds at 1.5T. The fractional activation volume vs. breathhold duration reached a plateau of 49.54 ± 7.26% at 15 seconds at 3T, which was higher and shorter than that at 1.5T. The maximum signal changes were significantly larger (a 69% increase) at 3T than at 1.5T. In the patient group, there were BOLD signal increases in gray matter but not in tumor bulk or perifocal edema, which agreed with the results previously found at 1.5T.

Conclusion:

BOLD MRI at 3T is more sensitive for detecting breathhold‐regulated signal changes than at 1.5T, which allows a shorter and more feasible breathhold paradigm for clinical applications in patients with brain tumors. J. Magn. Reson. Imaging 2010;31:78–84. © 2009 Wiley‐Liss, Inc.     

Cerebral asymmetry in patients with schizophrenia: A voxel‐based morphometry (VBM) and diffusion tensor imaging (DTI) study

Purpose:

To evaluate the differences in gray‐ and white‐matter asymmetry between schizophrenia patients and normal subjects.

Materials and Methods:

Forty‐eight right‐handed patients with chronic schizophrenia (24 males and 24 females) and 48 right‐handed age‐ and sex‐matched healthy controls (24 males and 24 females) were included in this study. The effects of diagnosis on gray‐matter volume asymmetry and white‐matter fractional anisotropy (FA) asymmetry were evaluated with use of voxel‐based morphometry (VBM) and voxel‐based analysis of FA maps derived from diffusion tensor imaging (DTI), respectively.

Results:

The mean gray‐ and white‐matter volumes were significantly smaller in the schizophrenia group than in the control group. The voxel‐based morphometry (VBM) showed no significant effect of diagnosis on gray‐matter volume asymmetry. The voxel‐based analysis of DTI also showed no significant effect of diagnosis on white‐matter FA asymmetry.

Conclusion:

Our results of voxel‐based analyses showed no significant differences in either gray‐matter volume asymmetry or white‐matter FA asymmetry between schizophrenia patients and normal subjects. J. Magn. Reson. Imaging 2010;31:221–226. © 2009 Wiley‐Liss, Inc.     

Gray Matter Concentration Abnormality in Brains of Narcolepsy Patients

Objective

To investigate gray matter concentration changes in the brains of narcoleptic patients.

Materials and Methods

Twenty-nine narcoleptic patient with cataplexy and 29 age and sex-matched normal subjects (mean age, 31 years old) underwent volumetric MRIs. The MRIs were spatially normalized to a standard T1 template and subdivided into gray matter, white matter, and cerebrospinal fluid (CSF). These segmented images were then smoothed using a 12-mm full width at half maximum (FWHM) isotropic Gaussian kernel. An optimized voxel-based morphometry protocol was used to analyze brain tissue concentrations using SPM2 (statistical parametric mapping). A one-way analysis of variance was applied to the concentration analysis of gray matter images.

Results

Narcoleptics with cataplexy showed reduced gray matter concentration in bilateral thalami, left gyrus rectus, bilateral frontopolar gyri, bilateral short insular gyri, bilateral superior frontal gyri, and right superior temporal and left inferior temporal gyri compared to normal subjects (uncorrected p < 0.001). Furthermore, small volume correction revealed gray matter concentration reduction in bilateral nuclei accumbens, hypothalami, and thalami (false discovery rate corrected p < 0.05).

Conclusion

Gray matter concentration reductions were observed in brain regions related to excessive daytime sleepiness, cognition, attention, and memory in narcoleptics with cataplexy.     

Regional atrophy of transcallosal prefrontal connections in cognitively normal APOE ϵ4 carriers

Purpose

To investigate the possible effect of the APOE ?4 allele on age‐related regional volume loss within the corpus callosum (CC) in healthy ?4 allele carriers compared with noncarriers.

Materials and Methods

A total of 211 subjects, ages 27 to 83 years, 51 ?4 carriers and 160 noncarriers underwent T1‐weighted MRI scan. All subjects had normal MRI scan and performed within normal range on a neuropsychological battery of tests. CC was segmented into seven functionally relevant regions using a previously published probabilistic map of the CC connectivity. We measured the volumes of the CC and its subregions. We used a regression model (with volumes as dependent and age as independent variables) and compared the slopes between carriers and noncarriers using an analysis of covariance model. We also carried out voxel‐based‐morphometry analysis to investigate the possible effect of the APOE ?4 gene on the gray matter.

Results

We found that the volume of the CC and all subregions decreased with increasing age in both groups. The slope was steeper in the APOE ?4 carriers compared withthe noncarriers particularly in the prefrontal region (P = 0.02). No gray matter differences were observed between the two groups.

Conclusion

APOE ?4 polymorphism is associated with accelerated age‐related volume loss in the prefrontal callosal tracts without gray matter loss. This result suggests the role of APOE ?4 in the brain aging by primarily affecting white matter structures particularly in the frontal lobe. J. Magn. Reson. Imaging 2009;29:1021–1026. © 2009 Wiley‐Liss, Inc.

     

18F-Fluoromisonidazole positron emission tomography may differentiate glioblastoma multiforme from less malignant gliomas

Purpose

Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor and its prognosis is significantly poorer than those of less malignant gliomas. Pathologically, necrosis is one of the most important characteristics that differentiate GBM from lower grade gliomas; therefore, we hypothesized that ¹⁸F fluoromisonidazole (FMISO), a radiotracer for hypoxia imaging, accumulates in GBM but not in lower grade gliomas. We aimed to evaluate the diagnostic value of FMISO positron emission tomography (PET) for the differential diagnosis of GBM from lower grade gliomas.

Methods

This prospective study included 23 patients with pathologically confirmed gliomas. All of the patients underwent FMISO PET and ¹⁸F-fluorodeoxyglucose (FDG) PET within a week. FMISO images were acquired 4?h after intravenous administration of 400?MBq of FMISO. Tracer uptake in the tumor was visually assessed. Lesion to normal tissue ratios and FMISO uptake volume were calculated.

Results

Of the 23 glioma patients, 14 were diagnosed as having GBM (grade IV glioma in the 2007 WHO classification), and the others were diagnosed as having non-GBM (5 grade III and 4 grade II). In visual assessment, all GBM patients showed FMISO uptake in the tumor greater than that in the surrounding brain tissues, whereas all the non-GBM patients showed FMISO uptake in the tumor equal to that in the surrounding brain tissues (p?≤?0.001). One GBM patient was excluded from FDG PET study because of hyperglycemia. All GBM patients and three of the nine (33%) non-GBM patients showed FDG uptake greater than or equal to that in the gray matter. The sensitivity and specificity for diagnosing GBM were 100 and 100% for FMISO, and 100 and 66% for FDG, respectively. The lesion to cerebellum ratio of FMISO uptake was higher in GBM patients (2.74?±?0.60, range 1.71–3.81) than in non-GBM patients (1.22?±?0.06, range 1.09–1.29, p?≤?0.001) with no overlap between the groups. The lesion to gray matter ratio of FDG was also higher in GBM patients (1.46?±?0.75, range 0.91–3.79) than in non-GBM patients (1.07?±?0.62, range 0.66–2.95, p?≤?0.05); however, overlap of the ranges did not allow clear differentiation between GBM and non-GBM. The uptake volume of FMISO was larger in GBM (27.18?±?10.46%, range 14.02–46.67%) than in non-GBM (6.07?±?2.50%, range 2.12–9.22%, p?≤?0.001).

Conclusion

These preliminary data suggest that FMISO PET may distinguish GBM from lower grade gliomas.     

Quantitative analysis in clinical applications of brain MRI using independent component analysis coupled with support vector machine

Purpose:

To effectively perform quantification of brain normal tissues and pathologies simultaneously, independent component analysis (ICA) coupled with support vector machine (SVM) is investigated and evaluated for effective volumetric measurements of normal and lesion tissues using multispectral MR images.

Materials and Methods:

Synthetic and real MR data of normal brain and white matter lesion (WML) data were used to evaluate the accuracy and reproducibility of gray matter (GM), white matter (WM), and WML volume measurements by using the proposed ICA+SVM method to analyze three sets of MR images, T1‐weighted, T2‐weighted, and proton density/fluid‐attenuated inversion recovery images.

Results:

The Tanimoto indexes of GM/WM classification in the normal synthetic data calculated by the ICA+SVM method were 0.82/0.89 for data with 0% noise level. As for clinical MR data experiments, the ICA+SVM method clearly extracted the normal tissues and white matter hyperintensity lesions from the MR images, with low intra‐ and inter‐operator coefficient of variations.

Conclusion:

The experiments conducted provide evidence that the ICA+SVM method has shown promise and potential in applications to classification of normal and pathological tissues in brain MRI. J. Magn. Reson. Imaging 2010;32:24–34. © 2010 Wiley‐Liss, Inc.     

Fluid and white matter suppression with the MP2RAGE sequence

Purpose:

To develop a magnetic resonance imaging (MRI) sequence (fluid and white matter suppression, FLAWS) for generating two sets of images from a single acquisition: one with contrast similar to a T1‐weighted magnetization‐prepared rapid gradient‐echo sequence (MPRAGE) for structural definition; the other with nulled white matter (WM) signal intensity, similar to the fast gray matter T1 inversion recovery (FGATIR) sequence, for improved delineation of subcortical brain structures.

Materials and Methods:

The recently proposed MP2RAGE, which is a modification of the MPRAGE and generates two image sets at different inversion times, was employed to generate the FGATIR‐like contrast (FLAWS1) and MPRAGE‐like contrast (FLAWS2). Five healthy volunteers were scanned at 3T and brain tissue contrast and contrast‐to‐noise were compared.

Results:

FLAWS1 and FLAWS2 exhibited similar tissue contrast and contrast‐to‐noise as the “reference” sequences, FGATIR and MPRAGE, respectively. Synthetic minimum value images generated from FLAWS1 and FLAWS2 provided a gray matter‐dominant image.

Conclusion:

FLAWS provides two coregistered 3D volumes, one with nulled WM signal intensity and another with nulled cerebrospinal fluid. The coregistered nature of the two datasets allows for generating images that might be helpful in segmentation algorithms and clinical diagnosis. J. Magn. Reson. Imaging 2012;35:1063‐1070. © 2011 Wiley Periodicals, Inc.     

Differentiating multiple sclerosis from other causes of demyelination using diffusion weighted imaging of the corpus callosum

Purpose

To compare diffusion weighted imaging metrics in gray and white matter brain regions of patients diagnosed with multiple sclerosis (MS) to those diagnosed with secondary demyelinating diseases such as neurosarcoid and acute disseminated encephalomyelitis (ADEM).

Materials and Methods

Diffusion weighted scans were performed and apparent diffusion coefficients of 12 regions of interest were determined in 30 MS patients, 21 neurosarcoid patients, and 4 ADEM patients.

Results

Mean apparent diffusion coefficients were significantly higher in MS patients than in non‐MS patients in 6 of 6 of the corpus callosal regions assessed but not in any of the non‐callosal white or gray matter regions assessed.

Conclusion

Elevated apparent diffusion coefficients within the corpus callosum on diffusion weighted imaging may potentially help differentiate between patients with MS and patients with other diseases affecting the central nervous system white matter. J. Magn. Reson. Imaging 2009;30:732–736. © 2009 Wiley‐Liss, Inc.     

T2* MRI of minimal hepatic encephalopathy and cognitive correlates in vivo

Purpose:

To evaluate regional brain iron deposition in minimal hepatic encephalopathy (MHE) patients using T2*‐weighted gradient‐echo imaging and to explore the relationship between T2* MR changes and cognitive performance.

Materials and Methods:

Forty hepatitis‐B virus (HBV)‐related cirrhotic patients and 22 age‐, sex‐, and education‐matched healthy controls were included in this study. Of the patients, twenty eight patients were diagnosed with MHE. All subjects were administered Number Connection Test‐A (NCT‐A), Letter Digit Substitution Test (LDST), Rey‐Osterrieth Complex Figure Test (RCFT), and the Mini‐Mental State Examination (MMSE). T2*‐weighted gradient‐echo images were acquired using 3 Tesla MRI. Phase values (putative iron levels) in the frontal–basal ganglia–thalamocortical circuits were measured. Spearman correlation and multiple linear regression analysis were performed.

Results:

MHE patients exhibited significantly prolonged NCT‐A time and decreased LDST, RCFT immediate and delayed recall scores. Significant decreases of phase values in the bilateral putamen were detected in MHE patients compared to without MHE patients and controls. Multiple linear regression analysis confirmed significant correlations between the phase values in the putamen and right frontal white matter and cognitive performances by MHE patients.

Conclusion:

Decreased phase values in the frontal cortical–basal ganglial circuits independently contribute to cognitive impairments in MHE patients. J. Magn. Reson. Imaging 2013;37:179–186. © 2012 Wiley Periodicals, Inc.     

Correspondence of human visual areas identified using functional and anatomical MRI in vivo at 7 T

Purpose:

To study the correspondence of anatomically and functionally defined visual areas (primary visual cortex, V1, and motion selective area V5/human MT+) by using structural magnetic resonance imaging (MRI) and functional MRI (fMRI) in vivo at 7 T.

Materials and Methods:

Four subjects participated in this study. High‐resolution (≈0.4 mm isotropic) anatomical MRI was used to identify cortical regions based on their distinct cortical lamination. The optimal contrast for identifying heavily myelinated layers within gray matter was quantitatively assessed by comparing T₁‐weighted magnetization‐prepared rapid gradient echo (MPRAGE) and T₂*‐weighted, 3D fast‐low angle shot (FLASH) imaging. Retinotopic mapping was performed using GE‐based fMRI at 1.5 mm isotropic resolution to identify functional areas.

Results:

T₂*‐weighted FLASH imaging was found to provide a significantly higher contrast‐to‐noise ratio, allowing visualization of the stria of Gennari in every slice of a volume covering the occipital cortex in each of the four subjects in this study. The independently derived boundary of V1, identified in the same subjects using retinotopic mapping by fMRI, closely matched the border of anatomically defined striate cortex in the human brain. Evidence of banding was also found within the functionally defined V5 area; however, we did not find a good correlation of this area, or the functionally identified subregion (MT), with the banded area.

Conclusion:

High‐resolution T₂*‐weighted images acquired at 7 T can be used to identify myelinated bands within cortical gray matter in reasonable measurement times. Regions where a myelinated band was identified show a high degree of overlap with the functionally defined V1 area. J. Magn. Reson. Imaging 2012;287‐299. © 2011 Wiley Periodicals, Inc.     

In vivo high‐resolution imaging of the injured rat spinal cord using a 3.0T clinical MR scanner

Purpose

To investigate the feasibility of obtaining high‐resolution MR images for the detection of pathological changes occurring in the injured rat spinal cord with a routine clinical 3.0T imaging system.

Materials and Methods

Adult female Fischer 344 rats received thoracic spine contusion injuries. In vivo MR imaging was performed on days 1 and 43 postinjury with a clinical head 3.0T imaging system equipped with a dedicated small animal 4‐channel phased array spine surface coil using T2‐weighted turbo spin‐echo and T1‐weighted spin‐echo sequences.

Results

The acquired images provide good spatial resolution allowing reliable gray/white matter differentiation in the intact spinal cord as well as detection of hemorrhage, edema, and cystic degenerative changes in the injured rat spinal cord as confirmed by correlation with structural alterations in histological sections.

Conclusion

Results from the present study demonstrate that a routine clinical MR imaging system can be employed for noninvasive analysis of pathological changes occurring in the injured rat spinal cord and thus might represent a more broadly available, powerful tool to monitor the effects of experimental therapeutic interventions in vivo. J. Magn. Reson. Imaging 2009;29:725–730. © 2009 Wiley‐Liss, Inc.     

Characterization of low‐grade gliomas using RGB color maps derived from ADC histograms

Purpose

To use normalized apparent diffusion coefficient (nADC) histograms from patients with grade II oligodendroglioma (OD) and astrocytoma (AC) to generate RGB color maps that emphasize the differences between normal‐appearing white matter (NAWM), oligo‐like, and astro‐like regions.

Materials and Methods

NAWM and nonenhancing lesion (NEL) ADC values from 19 ODs and 11 ACs were summed to generate oligo‐like (red), NAWM (green), and astro‐like (blue) nADC histograms. These nADC histograms were then used to map nADC values to an RGB matrix.

Results

Color maps of oligodendroglial tumor regions were generally visualized in pink, while color maps of astrocytic tumor regions showed various shades of blue. This technique was also applied to 23 patients with the more mixed subtype, oligoastrocytoma (OA), which showed a mixture of both blue and pink, which in many cases appeared to bleed into each other and were blotchy.

Conclusion

This technique allows for the visualization of biologically different regions within the whole tumor mass, which may aid in directing image‐guided biopsies. This can be used to ensure that the biopsy is directed to regions that can more accurately define the dominant tumor characteristics. J. Magn. Reson. Imaging 2009;30:209–213. © 2009 Wiley‐Liss, Inc.     

qMRI relaxometry of mandibular bone marrow: A monomodal distribution in sickle cell disease

Purpose:

To identify and characterize sickle cell disease (SCD)‐related changes in the composition of mandibular bone marrow using qMRI relaxometry histograms.

Materials and Methods:

Thirteen SCD patients and 17 controls underwent brain MR imaging with the mixed turbo spin‐echo (TSE) pulse sequence at 1.5T. The mandible was manually segmented and divided into body, angle, ramus, and condyle. T1 and T2 histograms of each mandible were modeled with Gaussian functions. The relaxation time histogram peaks were calculated, and the number of monomodal versus bimodal curves was compared.

Results:

SCD patients exhibited monomodal distributions on both T1 and T2 histograms, consistent with a composition of predominantly red hematopoietic marrow. Eighty‐eight percent of mandibles in control subjects exhibited a bimodal distribution in T1 and all showed a bimodal distribution in T2, indicating mixed but predominantly yellow marrow composition. The second peak in control subjects was shorter in T1 and longer in T2, consistent with yellow marrow composition.

Conclusion:

Instead of physiological fatty replacement, SCD patients exhibit red marrow persistence in the mandible, likely due to the increased demand for hematopoiesis. This phenomenon can be manifested by a monomodal curve in both T1 and T2 relaxometric histograms. J. Magn. Reson. Imaging 2013;37:1182–1188. © 2012 Wiley Periodicals, Inc.     

In vivo measurement of T1rho dispersion in the human brain at 1.5 tesla

Purpose

To measure T_1ρ relaxation times and T_1ρ dispersion in the human brain in vivo.

Materials and Methods

Magnetic resonance imaging (MRI) was performed on a 1.5‐T GE Signa clinical scanner using the standard GE head coil. A fast spin‐echo (FSE)‐based T_1ρ‐weighted MR pulse sequence was employed to obtain images from five healthy male volunteers. Optimal imaging parameters were determined while considering both the objective of the study and the guarantee that radio‐frequency (RF) power deposition during MR did not exceed Food and Drug Administration (FDA)‐mandated safety levels.

Results

T_1ρ‐weighted MR images showed excellent contrast between different brain tissues. These images were less blurred than corresponding T₂‐weighted images obtained with similar contrast, especially in regions between brain parenchyma and cerebrospinal fluid (CSF). Average T_1ρ values for white matter (WM), gray matter (GM), and CSF were 85 ± 3, 99 ± 1, and 637 ± 78 msec, respectively, at a spin‐locking field of 500 Hz. T_1ρ is 30% higher in the parenchyma and 78% higher in CSF compared to the corresponding T₂ values. T_1ρ dispersion was observed between spin‐locking frequencies 0 and 500 Hz.

Conclusion

T_1ρ‐weighted MRI provides images of the brain with superb contrast and detail. T_1ρ values measured in the different brain tissues will serve as useful baseline values for analysis of T_1ρ changes associated with pathology. J. Magn. Reson. Imaging 2004;19:403–409. © 2004 Wiley‐Liss, Inc.

     

MR imaging findings of small bowel hemorrhage: Two cases of mural involvement and one of perimural

Purpose

To demonstrate the MR appearance of small bowel wall hemorrhage.

Materials and Methods

A search was performed of the clinical information system (CIS) and the abdominal MRI databases of our institution for patients diagnosed with bowel hemorrhage on MRI between January 1, 2000, and July 31, 2008. All patients were imaged using a protocol that included noncontrast T1‐ and T2‐weighted images and postgadolinium gradient echo images.

Results

Two male patients, 44 and 55 years of age, were identified with small bowel mural hemorrhage, one in the duodenum and one in the jejunum. A third patient, a 66‐year‐old man, was identified with perimural hematoma. The following imaging features were observed: for mural hemorrhage, mural‐based increased signal intensity (SI) in the bowel wall on fat suppressed T1‐weighted images, variable increased SI on T2‐weighted images and no appreciable enhancement on the postcontrast T1‐weighted image; perimural hemorrhage exhibited normal thickness low SI wall on T2‐weighted single shot images, with ill‐defined material surrounding the bowel. SI features of this material, was similar to mural‐based abnormality.

Conclusion

In two patients with small bowel wall hemorrhage, the wall showed increased thickness with increased SI on noncontrast T1‐weighted images and lack of enhancement on postgadolinium images. Perimural hematoma showed an intact normal thickness wall that was low SI on T2 with surrounding material that was high SI on noncontrast T1‐weighted images and did not enhance. J. Magn. Reson. Imaging 2009;29:1185–1189. © 2009 Wiley‐Liss, Inc.     

Comparative study of standard space and real space analysis of quantitative MR brain data

Purpose:

To compare the robustness of region of interest (ROI) analysis of magnetic resonance imaging (MRI) brain data in real space with analysis in standard space and to test the hypothesis that standard space image analysis introduces more partial volume effect errors compared to analysis of the same dataset in real space.

Materials and Methods:

Twenty healthy adults with no history or evidence of neurological diseases were recruited; high‐resolution T₁‐weighted, quantitative T₁, and B₀ field‐map measurements were collected. Algorithms were implemented to perform analysis in real and standard space and used to apply a simple standard ROI template to quantitative T₁ datasets. Regional relaxation values and histograms for both gray and white matter tissues classes were then extracted and compared.

Results:

Regional mean T₁ values for both gray and white matter were significantly lower using real space compared to standard space analysis. Additionally, regional T₁ histograms were more compact in real space, with smaller right‐sided tails indicating lower partial volume errors compared to standard space analysis.

Conclusion:

Standard space analysis of quantitative MRI brain data introduces more partial volume effect errors biasing the analysis of quantitative data compared to analysis of the same dataset in real space. J. Magn. Reson. Imaging 2011;33:1503–1509. © 2011 Wiley‐Liss, Inc.     

Computer‐aided detection of brain tumor invasion using multiparametric MRI

Purpose

To determine the potential of using a computer‐aided detection method to intelligently distinguish peritumoral edema alone from peritumor edema consisting of tumor using a combination of high‐resolution morphological and physiological magnetic resonance imaging (MRI) techniques available on most clinical MRI scanners.

Materials and Methods

This retrospective study consisted of patients with two types of primary brain tumors: meningiomas (n = 7) and glioblastomas (n = 11). Meningiomas are typically benign and have a clear delineation of tumor and edema. Glioblastomas are known to invade outside the contrast‐enhancing area. Four classifiers of differing designs were trained using morphological, diffusion‐weighted, and perfusion‐weighted features derived from MRI to discriminate tumor and edema, tested on edematous regions surrounding tumors, and assessed for their ability to detect nonenhancing tumor invasion.

Results

The four classifiers provided similar measures of accuracy when applied to the training and testing data. Each classifier was able to identify areas of nonenhancing tumor invasion supported with adjunct images or follow‐up studies.

Conclusion

The combination of features derived from morphological and physiological imaging techniques contains the information necessary for computer‐aided detection of tumor invasion and allows for the identification of tumor invasion not previously visualized on morphological, diffusion‐weighted, and perfusion‐weighted images and maps. Further validation of this approach requires obtaining spatially coregistered tissue samples in a study with a larger sample size. J. Magn. Reson. Imaging 2009;30:481–489. © 2009 Wiley‐Liss, Inc.