脑肿瘤治疗后磁共振质子波谱评价

目的：评估脑肿瘤手术后、放疗后的多体素^1H MRS的临床应用价值。方法：21例脑肿瘤手术后、放疗后行多体素^1H MRS检查。结果：^1H MRS显示脑肿瘤内Cho升高5例，其中4例手术证实为肿瘤复发，1例为胶质增生。放射治疗后肿瘤生长抑制。^1H MRS表现为Cho降低，NAA、Cr明显下降。放射性坏死^1H MRS表现为肿瘤坏死区出现乳酸-脂质峰。结论：^1H MRS可评估脑肿瘤术后复发和监测肿瘤放疗后的病理变化，是一种有价值的检查方法。     

^1H磁共振波谱在胶质瘤放疗后复发和放射性脑坏死鉴别中的初步应用

目的：探讨质子磁共振波谱（^H MRS）对胶质瘤放射后复发和放射性脑坏死鉴别诊断的价值。方法：15例有脑部放疗史,临床及CT、MRI难以判断为肿瘤复发或放射性脑坏死的患者5例病史明确的放射性脑坏死的患者,均行^H MRS检查,结果：15例经手术证实,14例为胶质瘤1例放射性脑坏死,^H MRS诊断正确。（1）14例胶质瘤在^H MRS上均表现为明显增高的胆碱（Cho)峰,氮乙酰门冬氨酸（NAA）,肌酸（Cr)峰下降 或消失,Cho/Cr比值升高,NAA／Cr比值降低;12例出现乳酸（Lac)峰。（2）放射性脑坏死表现为：5例Cho,NAA,Cr下降或消失,出现脂质（Lipid)峰;1例Cho,NAA,Cr峰均消失,仅表现一较平坦的曲线,无Lac峰。结论^H MRS对胶质瘤疗后复发和放射性脑坏死的鉴别有重要价值。     

鼻咽癌放疗后放射性脑病的1H-MR波谱研究

目的　探讨鼻咽癌放疗后放射性脑病的磁共振氢波谱 (1H MRS)表现 ,了解N 乙酰天门冬氨酸 (NAA)、肌酸 (Cr)和胆碱 (Cho)这 3种物质的代谢规律 ,为放射性脑病的早期诊断提供方法。方法　对照组 10例健康志愿者 ,病例组 2 1例病理诊断为鼻咽癌并进行根治性放疗后经症状及影像学诊断为放射性脑病的病人 ,用化学位移成像法 (CSI)行1H MRS检查。观察各像素中NAA、Cr和Cho的含量、代谢图及它们之间比例。结果　放射性脑病MRI可见病灶中的液化坏死区 3种物质含量基本为零 ,代谢图中无信号 ;可见病灶中非液化坏死区NAA轻度升高 ,Cr和Cho明显降低或为零 ,NAA代谢图呈高信号 ,Cr和Cho低信号 ;可见病灶周边存在 1个区域性的NAA降低、Cr和Cho升高 ,NAA/Cr和NAA/Cho <1,代谢图中信号区分不明显 ;远离可见病灶的区域NAA、Cr和Cho含量及比例正常。结论　1H MRS发现物质代谢变化是有规律的 ,变化的区域大于MRI中可见病变区 ,为早期诊断提供了可能性。     

3.0T氢质子磁共振波谱成像在胶质瘤术前分级及术后随访中的应用

目的分析3.0T MRS成像在脑胶质瘤术前分级及术后随访中的应用价值。方法对61例临床及常规磁共振成像考虑胶质瘤者行2D-MRS检查并与3D-ASL比较,观察各代谢物成分及比值,术前对胶质瘤级别进行前瞻性判断,对照术后结果进行回顾性分析及随访。结果肿瘤实质部分NAA下降、Cho升高,高级别胶质瘤Cho/NAA为5.3±2.2、Cho/Cr为3.5±1.5,低级别Cho/NAA为1.6±0.3、Cho/Cr为1.8±0.5,差异有统计学意义(P﹤0.05)。术后6月内随访,12例复发,7例并发放射性脑病中4例复发。结论磁共振波谱成像可在术前准确判断胶质瘤级别、术后敏感监测肿瘤复发。与3D-ASL比较,MRS对瘤周水肿肿瘤细胞的浸润及术后放疗后肿瘤复发识别优于3D-ASL。     

中枢神经系统血管外皮细胞瘤的MRI表现与病理分析

目的:分析中枢神经系统血管外皮细胞瘤影像学特征及其诊断价值。材料和方法:回顾性分析经手术病理证实的中枢神经系统血管外皮细胞瘤MRI征象、弥散加权成像、灌注成像及波谱成像结果。结果:中枢神经系统血管外皮细胞瘤39例,其中35例位于颅脑,4例在脊髓。大多数呈分叶状且病灶大,有血管流空信号,易发生囊变坏死,水肿及占位征象明显;MRI显示不均匀稍长、等或混杂T1WI,均匀等或稍长和T2WI信号,累及静脉窦及硬脑膜常见,典型病例显示增强明显且极不均匀或中度不均一增强。弥散加权成像表现混杂或略低信号,其实性部分信号略高,病灶内ADC值为(12.68±4.01)10-4mm2/s,病灶侧ADC值大于对侧正常脑组织。13例行灌注成像的病变显示病灶侧相对局部脑血容量明显升高,呈不均质高灌注。时间-信号曲线显示负性增强显著,下降支与上升支分别显示不对称。7例行MRS检查的病变显示NAA降低,Cho升高。结论:中枢神经系统血管外皮细胞瘤MRI具有特征性表现,结合弥散加权成像与灌注成像及MRS检查有助于对该肿瘤的诊断。     

~1H磁共振波谱在胶质瘤放疗后复发和放射性脑坏死鉴别中的初步应用

目的　探讨质子磁共振波谱 (1HMRS)对胶质瘤放疗后复发和放射性脑坏死鉴别诊断的价值。方法　 15例有脑部放疗史 ,临床及CT、MRI难以判断为肿瘤复发或放射性脑坏死的患者 ,5例病史明确的放射性脑坏死的患者 ,均行1HMRS检查。结果　前 15例经手术证实 ,14例为胶质瘤 ,1例放射性脑坏死 ,1HMRS诊断正确。 (1) 14例胶质瘤在1HMRS上均表现为明显增高的胆碱(Cho)峰 ,氮乙酰门冬氨酸 (NAA)、肌酸 (Cr)峰下降或消失 ,Cho/Cr比值升高 ,NAA/Cr比值降低 ;12例出现乳酸 (Lac)峰。 (2 )放射性脑坏死表现为 :5例Cho、NAA、Cr下降或消失 ,出现脂质 (Lipid)峰 ;1例Cho、NAA、Cr峰均消失 ,仅表现一较平坦的曲线 ,无Lac峰。结论　1HMRS对胶质瘤放疗后复发和放射性脑坏死的鉴别有重要价值。     

MRS和ASL技术在脑胶质瘤复发和放射性损伤鉴别诊断中的应用

目的 分析磁共振波谱(MRS)和动脉自旋标记(ASL)技术在胶质瘤复发和放射性损伤中的鉴别诊断价值.方法 对手术和放射治疗后的18例脑胶质瘤患者,于再次手术前进行常规MRI平扫、增强扫描、ASL和MRS检查.MRS分析病变区代谢物含量及其比值,ASL测量病变区血流量,判断是否存在肿瘤复发和放射性损伤.对照患者再次手术的病理结果,比较上述2种技术在区分胶质瘤复发和放射损伤的诊断价值.结果 18例患者中,12例为肿瘤复发,6例为放射性坏死.所有患者病变强化区内均可见Cho/Cr比值增高和NAA/Cr比值的降低,2组患者间未见显著差异(P>0.05).肿瘤复发患者12例,ASL灌注图像显示病变区rCBF增高,而6例放射性损伤者rCBF降低,二者间具有显著性差异(P<0.05).结论 ASL技术在区分脑胶质瘤术后复发和放射性损伤方面具有应用价值.     

磁共振波谱成像对颅脑肿瘤的鉴别诊断价值

目的:分析脑肿瘤的氢质子磁共振波谱成像(1H-MRSI)改变,评价1H-MRSI对颅内常见肿瘤的诊断和鉴别诊断价值.方法:本组共42例颅内肿瘤患者行1H-MRSI检查,其中胶质瘤17例、脑膜瘤14例、脑转移瘤11例.测量比较3种肿瘤的实质强化区、周围水肿区和对侧正常脑组织的代谢物浓度(包括N-乙酰天门冬氨酸、肌酸和胆碱)并进行分析比较.结果:常规MRI检查T1WI上肿瘤多为等、低信号,T2WI上呈不均匀高信号,伴有不同程度强化和周围水肿.脑肿瘤的主要MRS袁现为NAA/Cho、NAA/Cr下降,Cho/Cr升高;3纽肿瘤周围水肿区的NAA/Cho分别为1.0167±0.314,1.4250±0.326和2.2900±1.186,组间比较差异均有显著性意义(P＜0.05);其它代谢物指标(NAA/Cr和Cho/Cr)在3种肿瘤间的差异无显著性意义(P＞0.05).3组肿瘤实质强化区各代谢物比值间差异无显著性意义(P＞0.05).结论:1H-MRSI可无创地分析脑肿瘤的代谢状况,对脑肿瘤的诊断、鉴别诊断均有很大的价值.     

自闭症的常规MRI和1H-MRS表现

目的 探讨常规MR成像和1H MR波谱(MRS)在自闭症诊断中的价值.资料与方法 回顾性分析12例自闭症患者的全脑常规MR扫描及其中8例患者额叶和海马的多体素2D 1H MR波谱扫描表现.结果 常规MR扫描发现3例患者的顶叶白质在FLAIR上出现斑片状高信号.1H MRS分析发现5例患者额叶的NAA/Cho明显下降(NAA/Cho<1),其中1例患者的左侧额叶出现Lac峰;另外有2例患者海马的NAA/Cho出现下降(NAA/Cho<1).结论 常规MR成像和1H MRS可发现部分自闭症患者脑组织异常.     

DWI和1H-MRS在儿童脑肿瘤中的诊断价值

目的:探讨DWI及单体素1H-MRS在儿童脑肿瘤影像诊断中的价值.方法:对21例脑肿瘤患儿行常规MRI、DWI及单体素1H-MRS成像,在DWI上测量病变实质区3个感兴趣区的ADC值,计算其平均值,单体素MRS感兴趣区选在肿瘤实质部分(强化者选在强化区域),计算感兴趣区的Cho/Cr、NAA/Cho、NAA/Cr比值,...     

^H磁共振波谱在恶性胶质瘤与脑单发转移瘤鉴别诊断中的应用

目的:探讨1H磁共振波谱(1HMRS)鉴别恶性胶质瘤与脑单发转移瘤的价值.材料和方法:选择经病理证实的22例单发脑肿瘤患者(14例脑胶质瘤,8例脑转移瘤)术前行常规和增强MRI扫描及1HMRS.对其中16例患者术后6个月后进行MRI复查.结果:14例脑胶质瘤患者胆碱复合物波高高于脑转移瘤;肿瘤增强区肌醇波高及肿瘤周围区谷氨酸及谷氨酰胺(Glu-n)波高高于脑转移瘤.8例脑转移瘤患者肿瘤增强区Glu-n波高高于脑胶质瘤.术后复查MRI,3例出现复发,1HMRS显示Glu-n及脂质波高显著升高(占18.8%).结论:1HMRS鉴别恶性胶质瘤与脑单发转移瘤有诊断价值,并可对预后判定提供帮助.     

CT and MR imaging after placement of the GliaSite radiation therapy system to treat brain tumor: initial experience

BACKGROUND AND PURPOSE: The GliaSite system delivers local, high radiation after brain tumor resection. We describe the imaging appearance of the device and the changes it causes. METHODS: Eight patients with brain tumors were treated with this system. After surgery, all underwent MR imaging, and one underwent CT. Five were examined 1 month after radioactive unloading and every 2 months thereafter (total, 6-9 months). Initial studies were assessed for balloon appearance and complications; subsequent studies, for signal intensity and enhancement. Three patients underwent multivoxel proton MR spectroscopy, and one underwent MR perfusion study. Spectra were reviewed for metabolites suggesting tumor; perfusion studies were reviewed for increased relative cerebral blood volume and flow. RESULTS: CT showed the hyperattenuating balloon with considerable artifact. All MR images showed the device and adjacent brain. Follow-up studies showed enhancement and T2 hyperintensity in five patients. In one, enhancement progressively disappeared with no evidence of tumor recurrence. Another patient had progressive enhancement and low relative cerebral blood volume and flow; biopsy showed necrosis and inflammation. One patient had progressive enhancement and high choline levels (proved anaplastic astrocytoma). In another, T2 signal intensity and contrast enhancement progressed owing to tumor and bacterial infection. The last patient had a high choline level (proved radionecrosis); enhancement progressed over 5 months. In three, the device was removed early because of bleeding, mass effect, and therapeutic changes (no follow-up). CONCLUSION: Good balloon visualization was possible with MR imaging. After brachytherapy, all patients developed T2 hyperintensity; stable or progressive enhancement occurred with tumor recurrence and radionecrosis. High choline levels were suggestive of, but not necessarily diagnostic of, tumor.     

Late temporal lobe necrosis in patients with nasopharyngeal carcinoma: evaluation with combined multi-section diffusion weighted and perfusion weighted MR imaging

Late temporal lobe necrosis is a well-known and serious complication in patients with nasopharyngeal carcinoma (NPC) following radiotherapy. Owing to the close proximity to the skull base, the medial temporal lobes are inevitably included in the target volume of irradiation. Patients with NPC provide a unique opportunity in study of delay radiation effect in normal human brain. The objective of this study was to evaluate late temporal lobe radiation injury by combined multi-section diffusion weighted and perfusion weighted MR imaging. We prospectively studied 16 patients with typical clinical symptoms of late temporal lobe necrosis or other abnormalities in the temporal lobes incidentally detected by conventional MR imaging. All patients had a previous history of radiotherapy for histologically proven NPC. Conventional T1- and T2-weighted images, fast gradient echo with echo-planar diffusion-weighted and perfusion-weighted MR imaging were performed. Apparent diffusion coefficient (ADC) map and relative cerebral blood volume (rCBV) map were computed via commercially available software. MR diffusion and perfusion images were then analyzed and graded by two independent observers with focusing on the diffusion and perfusion mismatch. The temporal lobe lesions displayed marked high diffusion on the ADC map. The rCBV map also revealed marked hypoperfusion in these temporal lobe lesions in all patients. The areas of abnormality on the rCBV map were significantly larger than the lesions on the ADC map in 14 patients (observer 1) and 13 patients (observer 2). Since late temporal lobe necrosis is probably caused by damage of the endothelium of vessels and ischemia, perfusion and diffusion mismatch might imply injured tissue but potentially salvageable brain tissue. A mismatch may be potentially used to predict the response to treatment in-patients with late temporal lobe necrosis.     

Role of diffusion weighted imaging and proton magnetic resonance spectroscopy in ring enhancing brain lesions

Aim of the work

To assess and compare the usefulness and efficacy of both diffusion weighted imaging (DWI) and proton magnetic resonance spectroscopy (¹HMRS) in brain lesions with ring enhancement in post contrast T1WI and to determine which method is more effective.

Subjects and methods

Thirty patients with ring-enhanced brain lesions were classified into 2 groups, abscess group (11 patients) and tumor group (19 patients), were examined using diffusion-weighted imaging (DWI) and H-proton magnetic resonance spectroscopy (¹HMRS).

Results

Restricted diffusion and low ADC value were seen in 9 (81%) patients of brain abscesses, however, free diffusion and high ADC value were found in 18 (94%) patients with necrotic brain tumor. The abscess group showed aminoacids, acetate and lactate in 9 patients and extra peak of succinate was found in 1 patient; however in the tumor group lactate alone was found in 12 patients, lactate and choline were seen in 5 patients, none of the patients showed amino acids, succinate or acetate.

Conclusion

Both DWI and ¹HMRS are useful and efficient imaging techniques in ring enhancing brain lesions and differentiate between pyogenic brain abscesses and necrotic tumors, but DWI is accurate, has less imaging time than ¹HMRS, also is available in many imaging centers.     

Preoperative proton MR spectroscopic imaging of brain tumors: correlation with histopathologic analysis of resection specimens

BACKGROUND AND PURPOSE: Tumor progression is often difficult to distinguish from nonneoplastic treatment response on the basis of MR images alone. This study correlates metabolite levels measured by preoperative MR spectroscopic (MRS) imaging with histologic findings of biopsies, obtained during image-guided resections of brain mass lesions, to clarify the potential role of MRS in making this distinction. METHODS: Twenty-nine patients with brain tumors underwent high-resolution (0.2-1 cc) 3D proton MRS imaging and MR imaging before undergoing surgery; 11 had a newly diagnosed neoplasm, and 18 had recurrent disease. Surgical biopsies were obtained from locations referenced on MR images by guidance with a surgical navigation system. MR spectral voxels were retrospectively centered on each of 79 biopsy locations, and metabolite levels were correlated with histologic examination of each specimen. RESULTS: All mass lesions studied, whether attributable to tumor or noncancerous effects of previous therapy, showed abnormal MR spectra compared with normal parenchyma. When the pattern of MRS metabolites consisted of abnormally increased choline and decreased N-acetyl aspartate (NAA) resonances, histologic findings of the biopsy specimen invariably was positive for tumor. When choline and NAA resonances were below the normal range, histologic findings were variable, ranging from radiation necrosis, astrogliosis, and macrophage infiltration to mixed tissues that contained some low-, intermediate-, and high-grade tumor. CONCLUSION: This study demonstrated that 3D MRS imaging can identify regions of viable cancer, which may be valuable for guiding surgical biopsies and focal therapy. Regions manifesting abnormal MR spectra had a mixture of histologic findings, including astrogliosis, necrosis, and neoplasm.     

Discrepant MR spectroscopic and perfusion imaging results in a case of malignant transformation of cerebral glioma

We present serial MR perfusion and spectroscopic findings of a pathologically proved low grade glioma, which evolved into glioblastoma multiforme in 2 years in a 24-year-old man. The initial MR imaging studies, including enhanced conventional T1-weighted and perfusion imaging, were characteristic of a benign glioma with the only exception being that multi-voxel proton MR spectroscopy showed malignant features with a high choline:phosphocreatine ratio. Postoperative follow-up MR imaging revealed findings consistent with malignant glioma, with increased angiogenesis on perfusion images and heterogeneous enhancement on contrast-enhanced T1-weighted images that were further confirmed by second surgery. We suggest conducting close MR imaging follow-up of patients with glioma who have discrepant MR spectroscopic and perfusion results after treatment.     

Distinction between high-grade gliomas and solitary metastases using peritumoral 3-T magnetic resonance spectroscopy,diffusion, and perfusion imagings

This study compared the effectiveness of relative cerebral blood volume, apparent diffusion coefficient, and spectroscopic imaging in differentiating between primary high-grade gliomas and solitary metastases. A 3.0-T MR unit was used to perform proton MR spectroscopy, diffusion imaging, and conventional MR imaging on 26 patients who had solitary brain tumors (14 high-grade gliomas and 12 metastases). All diagnoses were confirmed by biopsy. Twelve perfusion MR studies (8 high-grade gliomas and 4 metastases) were also performed. The results showed that the choline to creatine ratio and relative cerebral blood volume in the peritumoral regions of high-grade gliomas were significantly higher than they were in the metastases. The apparent diffusion coefficient values in tumoral and peritumoral regions of metastases were significantly higher than they were in the primary gliomas. Although conventional MR imaging characteristics of solitary metastases and primary high-grade gliomas may sometimes be similar, the peritumoral perfusion-weighted and spectroscopic MR imaging enable distinction between the two. Diffusion-weighted imaging techniques were complementary techniques to make a differential diagnosis between the two malignant tumors.     

Neuroimaging in pediatric brain tumors: Gd-DTPA-enhanced, hemodynamic, and diffusion MR imaging compared with MR spectroscopic imaging

BACKGROUND AND PURPOSE: Gadolinium-enhanced MR images assist in defining tumor borders; however, the relation between tumor cell extent and contrast-enhanced regions is unclear. Our aim was to improve conventional neuroimaging of pediatric brain tumors with hemodynamic, diffusion, and spectroscopic MR imaging. METHODS: We performed conventional MR and MR spectroscopic imaging in 31 children with neuroglial brain tumors. Hemodynamic MR imaging was performed in 16 patients with a first-pass intravenous bolus of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA); apparent diffusion coefficients (ADCs) were measured in 12 patients. To account for multiple measurements in a patient, we used a nested analysis of variance. RESULTS: At MR spectroscopy, choline (Cho)-containing compounds (indicating tumor) and lipid levels (indicating necrosis) did not correlate with percent Gd-DTPA enhancement on MR images. Percent enhancement was positively correlated with relative cerebral blood volumes (rCBVs) (P =.05) and negatively correlated with ADCs (P <.001). Stepwise multiple linear regression revealed that rCBV (P =.008), ADC (P =.022), and lipid (P <.001) levels were significant independent predictors of percent enhancement. Tumor spectral patterns were detected in tumor regions and outside enhancing tumor beds in patients with clinical progression; these were confirmed at neuropathologic analysis. CONCLUSION: MR spectroscopic imaging improves the assessment of pediatric brain tumors by adding biochemical information regarding tumor involvement and by depicting residual or recurrent tumor outside the Gd-DTPA-enhanced tumor bed. rCBV and ADC mapping complemented MR spectroscopic imaging. We recommend the use of MR spectroscopic imaging in addition to conventional MR imaging in assessing pediatric brain tumors.     

H proton MR spectroscopy and diffusion-weighted imaging in discrimination between pyogenic brain abscesses and necrotic brain tumors

Background

Differentiation between cerebral abscesses and necrotic brain tumors showing ring enhancement can be confusing at times by conventional MRI. The introduction of advanced imaging techniques, such as MR spectroscopy and diffusion WI, have contributed to the differentiation.The purpose of this study is to test the hypothesis that MR spectroscopy and diffusion weighted can be used to differentiate between necrotizing or cystic brain tumor and brain abscesses.

Methods

The study was conducted on 45 patients (necrotic or cystic tumor (30 cases); brain abscess (15 cases) showing ring-shaped contrast enhancement on conventional MRI. 1.5-T ¹H-MR Spectroscopy and diffusion WI were performed and the results were ensured by stereotactic biopsy or aspiration procedures in surgically indicated cases and/or follow up.

Results

14 patients (out of 15) with pyogenic abscess had lactate, amino acids, and acetate peaks; Succinate peak is seen as extra peak in three of these patients, and lipid peaks are also seen as extra peaks in 3 patients. One patient with brain stem abscess after 20 days treatment by antibiotics shows only lactate and lipid peaks. 2 of them show mild increase in choline with decrease in NAA (brain tissue contamination).17 out of 30 patients with cystic or necrotic tumor showed only lactate peak in MRS. While 13 patients show lactate and lipid peaks, four of them show additional high choline peak with low NAA and creatine peak (contamination with brain tissue).The results were confirmed by Sterotactic biopsy in 27 cases and aspiration in 13 cases and follow up for all cases.The sensitivity, specificity, PPV, NPV and overall accuracy of diffusion and MRS were 88%, 100%, 100%, 93.3% and 95.5% respectively.

Conclusion

¹H-MRS and diffusion WI are fast, easy to perform, noninvasive, and provide additional information that can accurately differentiate between necrotic/cystic tumors and cerebral abscesses.     

Use of diffusion-weighted imaging in recurrent central nervous system Whipple's disease: a case report and review of the literature

A case of Whipple's disease with development of antibiotic resistance is reported. The patient's symptomatology correlated with evolution of diffusion abnormality rather than with lesion enhancement. The lesion demonstrated no hyperperfusion, moderately elevated choline, and decreased N-acetylaspartate.Conventional magnetic resonance (MR) imaging findings of central nervous system Whipple's disease are nonspecific and may mimic neoplasm. MR perfusion and spectroscopy findings are reported, which may assist in diagnosis. Change in diffusion restriction appears to be a potential imaging indicator of clinical progression and response to therapy.