颅内先天性胆脂瘤的MRI诊断

目的:评价颅内先天性胆脂瘤的MRI影像学特征.方法:回顾性复习20例经手术与病理证实的颅内先天性胆脂瘤.术前均行MRI平扫与增强检查.结果:肿瘤发生于桥小脑角区11例,鞍上区3例,鞍旁区3例,四脑室1例,侧脑室1例,小脑蚓部1例.典型表现者16例,占80%,表现为T1WI低信号,T2WI高信号;非典型者4例,占20%,T1WI表现为欠均匀高信号,T2WI表现为低信号.增强扫描,16例肿瘤不强化,4例边缘强化.结论:MRI对诊断颅内先天性胆脂瘤有重要价值.     

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.     

Application of contrast agents in CT and MRI (NMR): their potential in imaging of brain tumors

Summary 21 patients with clinical and CT diagnoses of intracranial tumor were studied by MRI (NMR) prior to and after administration of intravenous Gadolinium-DTPA. Resultant MRI images were compared with corresponding CT sections with respect to lesion detection, contrast enhancement, tumor delineation and visualization of perifocal edema. All intracranial lesions shown on CT were identified on MRI. Contrast enhancement in MRI images was achieved in 19 out of 21 patients, as it was also with CT. In these cases improved differentiation between tumor, perifocal edema and adjacent brain structures were obtained. In most cases sufficient visualization of perifocal edema in MRI required T₂ weighted images (SE 1600/70) in addition to spin echo scans routinely performed prior to and after contrast medium (SE 400/30 or 800/30). No side effects were encountered following administration of Gadolinium-DTPA. The good tolerance and the efficacy justifies the use of Gadolinium-DTPA for contrast enhanced MRI imaging.Dedicated to Professor S. Wende on the occasion of his 60th birthday     

The significance of added ADC value to conventional MR imaging in differentiation between benign and malignant ovarian neoplasms

Purpose

To highlight the role of ADC value measurement in differentiating benign from malignant ovarian tumors.

Materials and methods

Twenty patients with ovarian neoplasms underwent conventional MRI including ADC value calculation before surgery. Retrospective analysis of the pathological specimen with lesion morphology, signal characteristics, enhancement criteria and correlation with the appearance at DWI followed by ADC value measurement were obtained.

Results

Twenty patients with ovarian mass lesions were included. They were divided into purely solid, purely cystic and complex solid/cystic lesions. All solid malignant lesions showed diffusion restriction as well as the wall and septations of most malignant cystic lesion however, except one case. All benign lesions did not display diffusion restriction in DWI. The best cut off value of ADC to discriminate between benign and malignant lesions was 0.9 with specificity of 100%, sensitivity of 88.9%, NPV of 75%, PPV of 100% and accuracy of 91.7%.

Conclusion

Addition of ADC value measurement to conventional MRI increases its specificity from 78.6% to 85.7% which could be useful in differentiating benign from malignant lesions.     

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.     

Diagnostic yield of combined magnetic resonance spectroscopy and diffusion weighted imaging in intracranial neoplasms

Purpose

Our intention was to evaluate the role of combined diffusion magnetic resonance imaging and spectroscopy in diagnosis and grading of brain tumors.

Materials and methods

Ninety-three included cases underwent magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) of the brain lesion, stereotactic or open biopsies and histopathological examination. MRI protocol included DWI and calculated ADC values. Multivoxel MRS spectroscopic technique (MVS) was used and all MRS metabolic parameters were obtained.

Results

High grade tumors had significantly lower ADC values than low grade tumors (P < 0.001). ADC values were the lowest in lymphoma (0.54 × 10⁻³ mm²/s) and the highest in craniopharyngioma (1.9 × 10⁻³ mm²/s). MRS revealed a statistically significant difference in CHO/NAA and CHO/Cr ratios between low and high grade tumors with P < 0.01 and P < 0.001, respectively. The mI/Cr ratio and presence of lactate, lipid and taurine also aided in differentiation and grading of brain tumors. The overall MRI/MRS sensitivity and specificity were 91%, 90.5%, respectively.

Conclusion

MRS has a robust diagnostic accuracy in cases of well defined high or low grade brain neoplasms. ADC value had the ability to confirm and differentiate low from high grade tumors in many situations where there were diagnostic confusions with MRS due to borderline values.     

MR imaging of hemorrhagic intracranial neoplasms

Thirty patients with intracranial tumors containing hemorrhage of varying stages were examined with high-field-strength MR imaging and CT to determine what differences might exist between hemorrhagic tumor and pure hemorrhage. Pathology was obtained in the six patients with primary tumors and in 14 of the 24 patients with metastases. Similar to evolving intraparenchymal hematomas, hemorrhagic neoplasms undergo changes in their appearance that can be categorized into three distinct intensity patterns, or stages. Stage 1 is characterized as iso- or hypointensity on short TR sequences and as hypointensity on long TR sequences; stage 2 as developing hyperintensity on both short and long TR sequences, without evidence of a well-defined black rim; and stage 3 as a hyperintense lesion with a well-defined black rim on long TR sequences. An additional mixed-intensity pattern was identified, which contained areas corresponding to more than one stage. In all of the cases exhibiting this pattern, pathology confirmed that the appearance was due to recurrent bleeding. We found several characteristics on MR that, when present, suggest an underlying neoplasm. These include delay in evolution between stages, central or eccentric hyperintensity in stage 2, and a mixed-intensity pattern. In addition, the presence of a hemosiderin rim does not exclude an underlying neoplasm. We found that the MR patterns that characterize hemorrhagic intracranial neoplasms should help to determine the cause of the hemorrhage.     

Grading of CNS neoplasms using continuous arterial spin labeled perfusion MR imaging at 3 Tesla

PURPOSE: To differentiate glioma grade based on blood flow measured using continuous arterial spin labeled (CASL) perfusion MRI, implemented at 3 Tesla for improved signal-to-noise ratio (SNR) and spin labeling effect. MATERIALS AND METHODS: CASL perfusion images were obtained preoperatively in 26 patients with brain neoplasms (19 high-grade gliomas (HGGs; WHO grades 3 and 4) and seven low-grade gliomas (LGGs; WHO grades 1 and 2)). The mean and maximum tumor blood flow (TBF and TBFmax) were calculated in the neoplasm, including surrounding infiltrating tumor vs. edema. Measures normalized to global CBF (nTBF and nTBFmax) were also obtained. RESULTS: Normalized measures of TBFmax provided the best distinction between HGG and LGG groups (Wilcoxon rank sum test, P = 0.01). Seventeen of 19 HGGs showed nTBFmax > 1.0, and 15 of 19 showed nTBFmax > 1.3. Four of seven LGGs showed nTBFmax < 1.0, and six of seven showed nTBFmax < 1.3. Absolute TBFmax also differed significantly between the HGG and LGG groups (P = 0.04). TBFmax in 11 of 17 HGGs was >50 mL/100 g/min (mean +/- SD = 94.9 +/- 71.7 mL/100 g/min). All but one LGGs showed TBFmax < or = 50 mL/100 g/min (mean +/- SD = 42.8 +/- 22.0 mL/100 g/min). CONCLUSION: CASL perfusion MRI provides a quantitative, noninvasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating gliomas.     

Diffusion tensor and tensor metrics imaging in intracranial epidermoid cysts

Purpose

To explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics (DTM) in characterizing the structural pathology of epidermoid cysts. DTI gives information about the tissue structure; a high fractional anisotropy (FA) indicates a highly structured orientation of the tissue, fibers, or white matter tracts. Based on the tensor rank, a set of three metrics has been described that can be used to measure the directional dependence of diffusion: linear anisotropy (CL), planar anisotropy (CP), and spherical anisotropy (CS). DTM takes into account the shape of diffusion anisotropy and hence may provide better insight into the orientation of structures than FA.

Materials and Methods

DTI was performed in three patients with epidermoid cysts. FA, directionally‐averaged mean diffusivity (Dav), exponential apparent diffusion coefficient (eADC), and DTM, such as CL, CP, and CS, were measured from the tumor core as well as from the normal‐appearing white matter. Histopathological correlation was obtained.

Results

Epidermoid cysts showed high FA with Dav values similar to that of normal white matter. eADC maps did not show any restriction of diffusion. FA values were high, but not as high as that for the white matter. CP values were higher and CL values were lower than those obtained for the white matter in various regions.

Conclusion

High CP values suggest preferential diffusion of water molecules along a two‐dimensional geometry, which could be attributed to the well‐structured orientation of keratin filaments and flakes within the tumor as demonstrated by histopathology. Advanced imaging modalities like DTI with DTM can provide information regarding the microstructural anatomy of the epidermoid cysts. J. Magn. Reson. Imaging 2009;29:967–970. © 2009 Wiley‐Liss, Inc.     

NMR imaging of the brain

Summary The basic features of an NMR imaging system are outlined and three pulse sequences which produce images with varying dependence on proton density T₁ and T₂ are described. The first of these sequences, Repeated Free Induction Decay produces images which demonstrate changes in proton density as well as flow effects. The second sequence, Inversion-recovery, produces images which are dependent on T₁ and show a high level of grey, white matter contrast giving considerable anatomical detail. In addition pathological processes such as infarction, haemorrhage, demyelination and malignancy produce changes in T₁ enabling lesions to be localised. The third sequence, Spin-echo, produces images which are dependent on T₂. These show very little grey, white matter contrast but demonstrate acute and space occupying lesions as well as cerebral oedema. The high level of grey, white matter contrast, lack of bone artefact, variety of sequences, capacity for multiplanar imaging, sensitivity to pathological change and lack of known hazard make NMR an important addition to existing techniques of neurological diagnosis.     

颅内不典型表皮样囊肿MR表现和病理对照分析

目的 探讨颅内不典型表皮样囊肿的MR表现及其与病理所见的关系.方法 回顾性分析7例颅内不典型表皮样囊肿的MR表现,并与手术病理所见对照.全部病例均行MR平扫检查,2例行MR增强扫描,1例行CT扫描.结果 4例表皮样囊肿位于小脑半球实质,2例位于大脑半球实质,1例位于小脑周围.T1WI 6例表皮样囊肿呈高信号,1例呈等信号,T2WI 5例呈很低信号,2例呈高信号.增强扫描囊肿不强化.病理检查镜下可见囊肿内大量蛋白物质.结论 颅内表皮样囊肿呈短T1和等T1信号主要与囊肿内存在大量蛋白物质有关,需要与颅内短T1信号的病变鉴别.     

Fetal intracranial tumors: a review of 27 cases

Fetal intracranial tumors are rare. The diagnosis is generally made on histology after birth. The aim of this study was to analyze clinical and imaging data in a series of fetal intracranial tumors and emphasize the findings that may help approach the diagnosis antenatally. We retrospectively analyzed imaging and clinical findings in 27 cases of fetal intracranial tumors assessed by ultrasound (27/27) and MR imaging (24/27). A histological diagnosis was always obtained. Main diagnoses included 15 germinal tumors (13 teratomas), 4 glial tumors, 2 craniopharyngiomas and 3 hamartomas. Average gestational age at diagnosis was 27 weeks for teratomas, 21 weeks for hamartomas and 34 weeks for glial tumors. All tumors but one were supra tentorial, and the lesion extended in the posterior fossa in two teratomas. A heterogeneous pattern, which was more frequently seen in teratomas, was better visualized by MR than US imaging. In addition, in two cases of teratomas, MR imaging better assessed the extension of the tumor. Teratomas and gliomas are the most frequent brain tumors in the fetus. US and MR imagings appear complementary in the prenatal assessment of these lesions.     

High-dose gadoteridol in MR imaging of intracranial neoplasms.

Twelve patients with a high suspicion of brain metastases by previous clinical or radiologic examinations were studied in a phase III investigation with magnetic resonance (MR) imaging at 1.5 T after a bolus intravenous injection of 0.1 mmol/kg gadoteridol followed at 30 minutes by a second bolus injection of 0.2 mmol/kg gadoteridol. All lesions were best demonstrated (showed greatest enhancement) at the 0.3-mmol/kg (cumulative) dose, with image analysis confirming signal intensity enhancement in the majority of cases after the second gadoteridol injection. More lesions were detected with the 0.3-mmol/kg dose than with the 0.1-mmol/kg dose, and more lesions were detected with the 0.1-mmol/kg dose than on precontrast images. In this limited clinical trial, high-dose gadoteridol injection (0.3-mmol/kg cumulative dose) provided improved lesion detection on MR images specifically in intracranial metastatic disease.     

Magnetic resonance imaging of intracranial neoplasms at 0.02 tesla

Sixty-five patients with single or multiple intracranial neoplasms were examined with an MR imager operating at 0.02 tesla. In 56 patients the diagnosis was histologically confirmed. All patients had an abnormal CT finding. MR images were positive in 59 cases, while the lesion remained undetected or equivocal in 6 cases (2 pituitary adenomas and 4 meningiomas). The MR signal intensity of several meningiomas was equal to that of normal brain tissue. Some astrocytomas were better delineated on MRI than on CT. For the study of pituitary lesions, the spatial resolution was unsatisfactory. The ultralow field MR imager was found to be sensitive for the detection of other intracranial neoplasms.     

NMR imaging in the recognition of giant intracranial aneurysms

Most giant aneurysms present clinically as intracranial mass lesions. Many contain an organized lamellated thrombus with only a small eccentric lumen remaining that can be opacified at angiography. Four patients with such aneurysms were studied using flow-dependent nuclear magnetic resonance scanning sequences. The aneurysms show a smooth rounded margin, and the thrombus within is clearly distinguishable from the blood flowing through the patent lumen, which gives a low signal. By using different scan sequences it is possible to prove that the area of low signal is indeed fluid in rapid motion, thus confirming the diagnosis.     

Pancreatic neuroendocrine tumor: added value of fusion of T2-weighted imaging and high b-value diffusion-weighted imaging for tumor detection

Objectives

To investigate the added value of fusion of high b-value diffusion-weighted images (DWI) and T2-weighted (T2) MR images for the detection of pancreatic neuroendocrine tumors (PNT).

Methods

18 patients with 18 histologically proven PNT were included. Two radiologists independently and retrospectively reviewed four randomized images sets (T2+T1, DWI, T2+DWI, and DWI+T2 fusion). Lesion detection confidence level was assessed using a three grade score (no lesion; uncertain lesion and certain lesion); lesion size and signal intensity were recorded. Apparent diffusion coefficients (ADC) of tumor and adjacent pancreas were measured.

Results

Readers 1 and 2 respectively detected 14/18 and 16/18 lesions on T2+T1, 13/18 and 12/18 on DWI, 16/18 and 15/18 on T2+DWI and 17/18 and 16/18 on DWI+T2 fusion. Lesion median size was 16 mm (range: 7 mm–40 mm), 22% were hyperfunctioning (all insulinomas) and 72% were low-grade (Rindi 1). All tumors except one (with cystic component) showed lower ADC than adjacent pancreatic parenchyma. Fusion imaging had significantly better detection score by both authors (p < 0.005) and provided the higher inter-reader agreement (kappa 0.7). DWI alone had the worst score for both readers.

Conclusions

Fusion images improve the detection of PNT, especially in patients with small isointense lesions on conventional MR sequences.     

MR imaging of peripheral intracranial neoplasms: extraaxial vs intraaxial masses

In an effort to determine magnetic resonance (MR) features of peripheral brain tumors that allow accurate localization. 11 extraaxial neoplasms were compared with 11 peripheral intraaxial tumors. The MR findings most often seen in extraaxial lesions include interruption of bone, white matter buckling, widening of adjacent subarachnoid space or cistern, and medial displacement of pial arteries or veins. Invasion of the cortex without white matter buckling, as well as flattening and lateral displacement of the surface veins, was most often seen in intraaxial lesions. Neither simple contiguity to a bony or dural surface nor vasogenic edema is a reliable predictor of intra- vs extraaxial masses.     

MRI (NMR) in the diagnosis of brain-stem tumors

Summary Patients with a brain-stem tumor were studied with NMR. The full extent of the lesion as well as its relationship with the adjacent structures was clearly demonstrated in all cases. Although NMR is, in many aspects, superior to CT and angiography, these examinations remain useful complementary methods.     

CT and MR imaging in atypical teratoid/rhabdoid tumors of the central nervous system

Introduction Atypical teratoid/rhabdoid tumors (ATRT) are rare aggressive neoplasms of the CNS affecting predominantly very young children. Methods We retrospectively reviewed the imaging findings of 9 CT and 32 MR examinations of the brain and spine of 33 children. Results Of the 33 tumors, 11 were located in the infratentorial compartment, 16 in the supratentorial compartment, 5 in both cranial compartments, and 1 in the lower thoracic spinal cord. The mean age of the children with infratentorial or infra- and supratentorial tumors was significantly lower than the mean age of the children with purely supratentorial tumors. Heterogeneity on imaging, large size and high tumor stages are striking features reflecting the aggressive nature of this histopathological entity. Although not present in the majority of children, a distinct and unusual pattern of a wavy band-like enhancement surrounding a central hypointensity was present in 12 of 32 children (38%) in whom contrast medium was used. Conclusion To the best of our knowledge this is the largest number of imaging examinations of ATRTs so far reported. A rather unusual pattern of contrast enhancement may be typical of ATRTs. This work was funded by the German Children’s Cancer Foundation (Deutsche Kinderkrebsstiftung).     

CT and MR imaging findings of endocrine tumor of the pancreas according to WHO classification

The pancreatic endocrine tumors are rare neuroendocrine tumors of the pancreas originating from totipotential stem cells or differentiated mature endocrine cells within the exocrine gland. Endocrine tumors are usually classified into functioning and non-functioning tumors and presents with a range of benignity or malignancy. In this article, we present the various CT and MR imaging findings of endocrine tumors of pancreas according to recent WHO classification.