Imaging diagnosis and fundamental knowledge of common brain tumors in adults

The most common primary brain tumors in Japanese adults are meningiomas, gliomas, pituitary adenomas, and schwannomas, which together account for 84.0% of all primary brain tumors. The typical imaging findings of these tumors are well known by radiologists; therefore, the clinical and pathological issues, including terminology, genetics, and relation to hormones are discussed in this article. Other diseases important for the differential diagnoses are also mentioned. The molecular genetic analysis of brain tumors has recently become important. For instance, genetic analysis is important for differentiating oligodendroglial tumors from astrocytic tumors, and the gene mutation predicts response to chemotherapy for anaplastic oligodendrogliomas. Background factors such as hormones, history of cranial irradiation, and medications influence oncogenesis, tumor growth, and tumor appearances as seen by imaging modalities. A differential diagnosis with knowledge of the above may have some advantages over diagnoses based on imaging findings alone. Nonneoplastic diseases such as abscesses and demyelinating diseases may mimic gliomas. Pituitary adenomas may be confused with nonneoplastic conditions such as physiological hypertrophy and Rathke's cleft cyst. Such misdiagnoses would result in a treatment protocol very different from what would be suitable. Such conditions should be carefully distinguished from neoplasms. This work was presented as an educational lecture at the 64^th Japan Radiological Society meeting (April 2005) in Yokohama.     

Use of half-dose gadolinium-enhanced MRI and magnetization transfer saturation in brain tumors

The aim of this study was to search if half-dose gadolinium (Gd)-enhanced MR imaging with magnetization transfer saturation (MT) can replace standard-dose T1-weighted spin echo (SE) without MT saturation in brain tumors. Thirty patients with a total of 33 brain tumors (14 gliomas, 13 meningiomas, 6 metastases) were prospectively studied using T1-weighted SE half-dose of Gd with MT, and T1-weighted SE standard-dose Gd without MT. The contrast-to-noise ratio (CNR) of the two sequences was calculated and four radiologists reviewed qualitatively the images of the two sequences. There was no significant difference between both techniques for quantitative analysis (Wilcoxon test). However, there was a good agreement between sequences to evidence an intraclass correlation coefficient (r = 0.70) of all lesions. In cases of meningioma, the agreement was better (r = 0.84). The results show a difference in the qualitative data between the two sequences, suggesting the use of the T1-weighted MR images with MT and half-dose of Gd with good results in the whole tested parameters except the lesional edema and the presence of artifacts. Half-dose T1-weighted SE with MT can replace standard-dose T1-weighted SE without MT with no loss of contrast enhancement in investigation of meningiomas and saving 50% of the contrast material.     

PET/MRI: Multiparametric imaging of brain tumors

A combination of morphological imaging of the brain with microstructural and functional imaging provides a comprehensive overview of the properties of individual tissues. While diffusion weighted imaging provides information about tissue cellularity, spectroscopic imaging allows us to evaluate the integrity of neurons and possible anaerobic glycolysis during tumor hypoxia, in addition to the presence of accelerated synthesis or degradation of cellular membranes; on the other hand, PET metabolic imaging is used to evaluate major metabolic pathways, determining the overall extent of the tumor (¹⁸F-FET, ¹⁸F-FDOPA, ¹⁸F-FCH) or the degree of differentiation (¹⁸F-FDG, ¹⁸F-FLT, ¹⁸F-FDOPA and ¹⁸F-FET). Multi-parameter analysis of tissue characteristics and determination of the phenotype of the tumor tissue is a natural advantage of PET/MRI scanning. The disadvantages are higher cost and limited availability in all centers with neuro-oncology surgery. PET/MRI scanning of brain tumors is one of the most promising indications since the earliest experiments with integrated PET/MRI imaging systems, and along with hybrid imaging of neurodegenerative diseases, represent a new direction in the development of neuroradiology on the path towards comprehensive imaging at the molecular level.     

延脊髓型脑干肿瘤的诊断和显微手术切除

目的 探讨延脊髓型脑干肿瘤的诊断和显微手术治疗效果。方法 16例患者经MRI诊断为延脊髓型脑干肿瘤。采用小脑延髓裂入路,于显微镜下手术切除病变及康复治疗。结果 12例肿瘤达全切除,3例获次全切除,1例为部分切除。瘤标本经病理学检查分别为星形细胞瘤、胶质母细胞瘤、血管网状细胞瘤。临床痊愈出院11例,好转出院4例,死亡1例。结论 MRI是诊断延脊髓型脑干肿瘤的最佳检查方法 ,采用显微手术治疗此类肿瘤,尽可能多的切除肿瘤,减少并发症,达到解除症状及延长生命的目的 ,手术效果良好。同时长期有效的后期康复治疗也很重要。     

Dynamic imaging of intracranial lesions using fast spin-echo imaging: Differentiation of brain tumors and treatment effects

The purpose of this study was to develop a technique for differentiating between recurrent brain tumors and treatment-related changes, such as radiation necrosis, using dynamic MRI. Ninety-five patients with intracranial mass lesions were evaluated using T1-weighted fast spin-echo (FSE) MRI at 1.5 T. Pathologies included treatment-related changes (n = 32), primary tumors (n = 41), metastatic tumors (n = 5), meningiomas (n = 4), and mixed primary/treatment related changes (n = 13). Signal enhancement-time curves were analyzed by fitting to a sigmoidal-exponential function. Maximal enhancement rates were calculated as the first derivative of the fitted curve. Based on the maximal enhancement rates, treatment-related changes could be differentiated from primary tumors, metastatic tumors, and meningiomas at the P < .05 confidence level. Lesions of mixed tumor and treatment-related change had intermediate values. Dynamic MRI can be used to differentiate treatment-related changes from primary tumors in previously treated patient populations based on maximal enhancement rates. Individual case studies demonstrate the clinical significance of these findings.     

Influence of fMRI on operative planning of brain tumors: Initial experience in a histopathologically variable subset of tumors

Background and purpose

Conventional MR imaging permits subcategorization of brain tumors; however, assessment of relation of the tumor to eloquent cortical centers is limited. Functional MRI (fMRI) is a promising method for visualizing cortical brain centers and for studying their relation to brain tumors which is an essential factor in proper planning of treatment strategy. The aim of this study is to assess and evaluate the value of fMRI in guiding preoperative decision making in patients with brain tumors.

Materials and methods

Both conventional and functional MRI were analyzed in 21 patients with brain tumors, the decision for treatment strategy for each case was determined twice, first with the data provided by the conventional MRI alone, second with the data provided by conventional and functional MRI.

Results

Accurate localization of eloquent cortical centers and as well as detailed assessment of their relation to the brain tumor were feasible in the majority of the examined patients, the data provided by this new technique modified the treatment strategy in seven of them aiming to avoid damage of eloquent brain areas.

Conclusion

fMRI can provide essential data about cortical centers and their relation with the tumor helping in safer preoperative planning.     

脑膜瘤瘤周水肿的MRI表现与手术病理对照研究

目的：分析脑膜瘤瘤周水肿的MRI表现与手术、病理的关系。材料和方法：对51例磁共振图像中脑膜瘤的瘤周水肿特点进行分析，并与手术、病理对照。结果：51％脑膜瘤伴瘤周水肿，磁共振T2WI瘤周水肿有月晕型（50％）和指样型（50％）两种，该分型与显微外科手术界面相对应。结论：MRI有助于脑内、外肿瘤的鉴别诊断。     

Target definition and trajectory optimization for interactive MR-guided biopsies of brain tumors in an open configuration MRI system

We present an imaging strategy for planning and guiding brain biopsies in an open configuration MR system. Preprocedure imaging was performed in a 1.5-T MR system and was designed to provide, in a clinically efficient manner, high resolution anatomical and functional/physiologic information for precise definition and tissue characterization of the target, aiming at optimization of the biopsy trajectory for planning a safe and accurate procedure. The interventions were performed in a .5-T open bore magnet, and imaging was optimized to provide the imaging quality and temporal resolution necessary for performing the procedure interactively in near real time. Brain biopsies of 21 patients were performed in a 10-month period. Segmentation and surface rendering analysis of the lesions and vascular structures and dynamic MR perfusion and cortical activation studies provided an efficient and comprehensive way to appreciate the relationship of the target to surrounding vital structures, improved tissue characterization and definition of the tumor margins, and demonstrated the location of essential cortex, allowing appropriate placement of the burr hole and choice of optimal trajectory. Interactive protocols provided good visualization of the target and the interventional devices and offered the operator real-time feedback and control of the procedure. No complications were encountered. Advanced methods of image acquisition and processing for accurate planning of interventional brain procedures and interactive imaging with MR guidance render feasible the performance of safe and accurate neurointerventional procedures.     

MR imaging of the brain: tumors

The radiologic modality that most likely provides the imaging information needed in a patient suspected of having a brain tumor is MR imaging. A brain tumor can be reliably ruled out if the MR examination is performed properly and experts interpret the results as negative. If there is a tumor, however, its exact location and topography must be determined. Important for therapy and prognosis are also tumor properties such as histologic type and grade, as well as effects on adjacent brain structures. Although potentially a noninvasive method of in vivo neuropathology, MR is still far from being sufficiently specific, as dissimilar lesions may look the same despite the use of refined imaging protocols. The evolution of MR imaging continues, however, making further methodologic improvement likely. Presently, advanced methods, such as diffusion- and perfusion-weighted MR imaging, functional MR imaging, neuronavigation based on MR imaging data, and the use of MR imaging during surgery (intraoperative MR imaging), influence the way patients are treated. Likewise, follow-up imaging (monitoring) of tumor patients by MR has become more effective, and experience has shown how to distinguish reactive changes from recurrent tumor. In the future, MR imaging may gain importance in the development of novel therapeutic concepts.     

MR spectroscopy in post-treatment follow up of brain tumors

PurposeTo detect the role of MR spectroscopy in evaluating the whole area of signal alteration within the irradiated volume aiming to differentiate recurrent/residual tumors from radiation injury and to detect the tumor margin and extent.Materials and methodsThis prospective study included 25 patients with previously treated primary intracranial tumors. All patients received radiotherapy. MRI and multivoxel MRS were performed. The volume of interest was placed over the whole area of signal alteration. The spectra were analyzed for the signal intensity of choline (Cho), creatine (Cr), and N-acetyl aspartate (NAA), lipid (Lip), lactate (Lac), and myo-inositol (mI). Metabolite ratios for Cho/NAA, Cho/Cr, and NAA/Cr were calculated.ResultsCho/NAA and Cho/Cr were significantly higher while NAA/Cr ratios were significantly lower in tumors than radiation injury (p = 0.001 for all ratios). The Cho/NAA and Cho/Cr ratios were significantly higher in radiation injury than in normal-appearing brain tissue (p = 0.032 and p = 0.008, respectively), whereas NAA/Cr was insignificantly lower in radiation injury than normal-appearing brain tissue (p = 0.051). Value >1.8 for Cho/NAA ratio was considered as indicator for tumor.ConclusionMR spectroscopy can differentiate recurrent/residual tumor from radiation injury and delineate the tumor margin and extent.     

MRS of brain tumors: Diagrammatic representations and diagnostic approach

Purpose

To evaluate magnetic resonance spectroscopy (MRS) in the assessment of brain tumors and grading brain glioma.

Patients and methods

Retrospective study was done for 42 patients with diagrammatic representations suggested by the author for the assessment of MRS data.

Results

Pathology grading was correlated with metabolic ratios in cases of brain glioma. Ratios higher than 1.5 for either Cho/Cr or Cho/NAA were consistent with tumors and ratios higher than 2 were consistent with high grade glioma or metastases.

Conclusion

MRS can be used to grade cases of brain glioma. Diagrammatic representations and a diagnostic approach were suggested by the author to simplify clinical practice.     

Uptake of 11C-l-and d-methionine in brain tumors

¹¹C-labeled l-and d-methionine uptake was measured in seven patients with brain tumors using positron emission tomography. Tumors accumulated both isomers of the tracer. The strongest uptake occurred in tumors with a high grade of malignancy, while low grade tumors accumulated less activity. The l to d uptake ratio in tumor regions ranged from 0.92–1.25. Conventional ^99mTc-DTPA scans revealed blood-brain barrier damage in two patients with no or only slight ¹¹C-methionine accumulation, while one patient with a negative ^99mTc-DTPA scan accumulated ¹¹C-methionine in the tumor region. In view of the biochemical pathway of methionine and the present findings, it is concluded that the uptake reflects metabolic activity in brain tissue rather than uptake by diffusion due to disruption of the blood-brain barrier.     

Segmentation of tumors in magnetic resonance brain images using an interactive multiscale watershed algorithm

RATIONALE AND OBJECTIVE: This article presents the evaluation of an interactive multiscale watershed segmentation algorithm for segmenting tumors in magnetic resonance brain images of patients scheduled for neuronavigational procedures. MATERIALS AND METHODS: The watershed method is compared with manual delineation with respect to accuracy, repeatability, and efficiency. RESULTS: In the 20 patients included in this study, the measured volume of the tumors ranged from 2.7 to 81.9 cm(3). A comparison of the tumor volumes measured with watershed segmentation to the volumes measured with manual delineation shows that the two methods are interchangeable according to the Bland and Altman criterion, and thus equally accurate. The repeatability of the watershed method and the manual method are compared by looking at the similarity of the segmented volumes. The similarity for intraobserver and interobserver variability for watershed segmentation is 96.4% and 95.3%, respectively, compared with 93.5% and 90.0% for manual outlining, from which it may be concluded that the watershed method is more repeatable. Moreover, the watershed algorithm is on average three times faster than manual outlining. CONCLUSION: The watershed method has an accuracy comparable to that of manual delineation and outperforms manual outlining on the criteria of repeatability and efficiency.     

Echo-planar magnetic resonance imaging (EPI) with high-resolution matrix in intra-axial brain tumors

The aim of this study was to assess the potential of high-speed interleaved echo-planar imaging (EPI) to achieve diagnostic image quality comparable to T2-weighted imaging in patients with brain tumors. Seventeen patients with intra-axial, supratentorial tumors (10 untreated gliomas, 7 radiated gliomas) were investigated on a 1.5-T scanner. The conventional scan (SE, TR/TE = 2200/80 ms, 18 slices) was acquired in 8 min, 4 s, and EPI (TR/TE = 3000/80 ms, 18 slices) was completed in 25 s. The films were compared in a blinded trail by three radiologists. On the general impression and anatomic display, both sequences were rated to be of similar quality. Artifacts were slightly more pronounced at the skull base and around surgical clips using EPI. Tumor delineation was nearly equivalent using EPI, compared with the T2-weighted sequence. Echo-planar imaging reached diagnostic quality in all patients. Interleaved high-resolution EPI yielded sufficient quality to depict intra-axial, supratentorial brain tumors. Since EPI can be obtained in a small fraction of the time needed for conventional spin echo, in addition to other indications it could be considered to study patients unable to cooperate. Received: 7 September 1998; Revision received: 6 November 1998; Accepted: 24 November 1998     

Peritumoral edema of meningiomas and metastatic brain tumors: differences in diffusion characteristics evaluated with diffusion-tensor MR imaging

Introduction We prospectively compared the fractional anisotropy (FA) and mean diffusivity (MD) of the peritumoral edema of meningiomas and metastatic brain tumors with diffusion-tensor magnetic resonance (MR) imaging. Methods The study protocol was approved by the local ethics committee, and written informed consent was obtained. Preoperative diffusion-tensor MR imaging was performed in 15 patients with meningiomas and 11 patients with metastatic brain tumors. Regions of interest (ROI) were placed in the peritumoral edema and normal-appearing white matter (NAWM) of the contralateral hemisphere to measure the FA and MD. The FA and MD ratios were calculated for each ROI in relation to the NAWM of the contralateral hemisphere. Changes in peritumoral MD and FA, in terms of primary values and ratios, were compared using a two-sample t-test; P < 0.05 was taken as indicating statistical significance. Results The mean MD values (×10⁻³ mm²/s) of the peritumoral edema for metastases and meningiomas, respectively, were 0.902 ± 0.057 and 0.820 ± 0.094, the mean MD ratios were 220.3 ± 22.6 and 193.1 ± 23.4, the mean FA values were 0.146 ± 0.026 and 0.199 ± 0.052, and the mean FA ratios were 32.3 ± 5.9 and 46.0 ± 12.1. All the values were significantly different between metastases and meningiomas (MD values P = 0.016, MD ratios P = 0.006, FA values P = 0.005, FA ratios P = 0.002). Conclusion The peritumoral edema of metastatic brain tumors and meningiomas show different MD and FA on diffusion-tensor MR imaging.     

The use of a partial transmission shield to reduce the optic chiasm doses during radiation therapy treatment of brain tumors

Historically, brain tumors have been treated with lateral opposed beams for 40–45 Gy followed by more conformal reduced fields. Advances in treatment planning computers have led to the implementation of conformal non-axial techniques, allowing for escalation of dose. In patients where total doses exceed 50 Gy, adjacent critical structures can be protected with a partially shielded transmission block over the optic nerves and chiasm. By eliminating the conedown portion of the treatment a more cost and time effective treatment is achieved. Partially shielded blocks can be designed by using cerrobend or multileaf collimation. They can be included in the treatment plan and verified by an irregular field calculation and/or thermoluminescent dosimeters.     

Diffusion-weighted echo-planar MR imaging in differential diagnosis of brain tumors and tumor-like conditions

We assess diffusion-weighted MR images in the differential diagnosis of intracranial brain tumors and tumor-like conditions. Heavily diffusion-weighted (b = 1100 or 1200 s/mm²) axial images were obtained with single-shot echo-planar technique in 93 patients with pathologically confirmed various intracranial tumors and tumor-like conditions with diffusion gradient perpendicular to the images. We compared signal intensity of the lesions with those of gray and white matter, and cerebrospinal fluid (CSF). In 29 cases (31.1 %) the lesions were isointense to gray and/or white matter. However, 5 cases (5.4 %) showed extremely increased signal intensity: two epidermoid cysts; two chordomas; and one brain abscess. The entire portion of a tumor was markedly hyperintense in 10 cases (10.8 %): four malignant lymphomas; four medulloblastomas; one germinoma; and one pineoblastoma. A CSF-like hypointense signal was seen in many cystic tumors, and cystic or necrotic portions of tumors. A neurosarcoid granulation was the only solid lesion showing characteristically a hypointense signal like CSF. The combination of markedly hyperintense and hypointense signals was seen generally in hemorrhagic tumors. Diffusion-weighted echo-planar MR imaging is useful in the differential diagnosis of brain tumors and tumor-like conditions, and suggests specific histological diagnosis in some cases. Received: 30 July 1999; Revised: 2 November 1999; Accepted: 9 December 1999     

Cerebral NMR: diagnostic evaluation of brain tumors by partial saturation technique with resistive NMR

Summary One hundred and forty patients with cerebral neoplasms were examined in a 0.12-Tesla prototype resistive NMR proton imaging device by partial saturation technique. NMR was superior to CT in tumor and edema localization and equal to CT in tumor and edema detection. NMR, however, was not able to clearly separate tumor from edema, a separation that contrast enhanced CT achieved.     

Localized 2D J-resolved H MR spectroscopy of human brain tumors in vivo

Application of two-dimensional (2D) J-resolved MR spectroscopy, fully localized in three dimensions to monitor the metabolites in human brain tumors in vivo on a whole body MR scanner is presented. A modified PRESS sequence with [90° – 180° – t₁/2 – 180° – t₁/2-acquisition] was used for voxel localization (2D J point-resolved spectroscopy [PRESS]); chemical shift selective (CHESS) sequence was used for suppression of water. The incremental delay (t₁/2) added to the intervals before and after the last slice-selective 180° RF pulse allowed the monitoring of the J-evolution in a localized 2D NMR spectrum. The addition of the second frequency dimension in 2D J-resolved spectroscopy to encode the indirect spin-spin coupling allowed the visualization of lactate peaks not observed in the 1D MR spectrum because of severe overlap with lipid peaks. 2D spectra of a two-layer phantom with 100 mM alanine and corn oil and also from three patients with tumors are presented here. The 2D spectra show that the J-coupled lactate peaks could be separated even when the lipids peaks severely overlap.     

Proton magnetic spectroscopic imaging of the child's brain: the response of tumors to treatment

Our aim was to determine and/or predict response to treatment of brain tumors in children using proton magnetic resonance spectro-scopic imaging (MRSI). We studied 24 patients aged 10 months to 24 years, using MRI and point-resolved spectroscopy (PRESS; TR 2000 TE 65 ms) with volume preselection and phase-encoding in two dimensions on a 1.5 T imager. Multiple logistic regression was used to establish independent predictors of active tumor growth. Biologically vital cell metabolites, such as N-acetyl aspartate and choline-containing compounds (Cho), were significantly different between tumor and control tissues (P < 0.001). The eight brain tumors which responded to radiation or chemotherapy, exhibited lower Cho (P = 0.05), higher total creatine (tCr) (P = 0.02) and lower lactate and lipid (L) (P = 0.04) than 16 tumors which were not treated (except by surgery) or did not respond to treatment. The only significant independent predictor of active tumor growth was tCr (P < 0.01). We suggest that tCr is useful in assessing response of brain tumors to treatment.