脑肿瘤MR弹性成像的初步临床研究

目的 探讨MR弹性成像(MRE)在脑肿瘤手术前评价其硬度的价值.方法 14例常规影像检查确定为实性脑肿瘤患者(男5例、女9例,年龄16～63岁),术前接受脑MRE检查,以脑白质为参照对肿瘤硬度进行评价.采用自行研制的用于脑MRE成像的激发装置,固定于头线圈上,并与患者头部固定,产生低频率振荡经颅骨传至颅内,引起剪切波在脑组织内传播;脉冲序列采用相位对比梯度回波序列,获得相位图像,从而显示脑组织内剪切波的传播.相位图像经局部频率估算法(LFE)处理后获得弹性图像;肿瘤的硬度在术中与正常脑白质对比,由术者判断分为偏软、中等和偏硬.将MRE的评价结果与手术结果作对照.结果 MRE检查结果显示,1例肿瘤的弹性模量低于正常脑白质、11例高于正常脑白质、2例与正常脑白质相似;术中检查1例肿瘤硬度偏软、11例偏硬,2例中等.14例由MRE评估的肿瘤弹性均与手术结果相符.结论 MRE可以无创地显示脑肿瘤的弹性,在术前对脑肿瘤的硬度进行评价.     

Harnessing brain waves: a review of brain magnetic resonance elastography for clinicians and scientists entering the field

Brain magnetic resonance elastography (MRE) is an imaging technique capable of accurately and non-invasively measuring the mechanical properties of the living human brain. Recent studies have shown that MRE has potential to provide clinically useful information in patients with intracranial tumors, demyelinating disease, neurodegenerative disease, elevated intracranial pressure, and altered functional states. The objectives of this review are: (1) to give a general overview of the types of measurements that have been obtained with brain MRE in patient populations, (2) to survey the tools currently being used to make these measurements possible, and (3) to highlight brain MRE-based quantitative biomarkers that have the highest potential of being adopted into clinical use within the next 5 to 10 years. The specifics of MRE methodology strategies are described, from wave generation to material parameter estimations. The potential clinical role of MRE for characterizing and planning surgical resection of intracranial tumors and assessing diffuse changes in brain stiffness resulting from diffuse neurological diseases and altered intracranial pressure are described. In addition, the emerging technique of functional MRE, the role of artificial intelligence in MRE, and promising applications of MRE in general neuroscience research are presented.     

Relationship between Shear Stiffness Measured by MR Elastography and Perfusion Metrics Measured by Perfusion CT of Meningiomas

BACKGROUND AND PURPOSE:When managing meningiomas, intraoperative tumor consistency and histologic subtype are indispensable factors influencing operative strategy. The purposes of this study were the following: 1) to investigate the correlation between stiffness assessed with MR elastography and perfusion metrics from perfusion CT, 2) to evaluate whether MR elastography and perfusion CT could predict intraoperative tumor consistency, and 3) to explore the predictive value of stiffness and perfusion metrics in distinguishing among histologic subtypes of meningioma.MATERIALS AND METHODS:Mean tumor stiffness and relative perfusion metrics (blood flow, blood volume, and MTT) were calculated (relative to normal brain tissue) for 14 patients with meningiomas who underwent MR elastography and perfusion CT before surgery (cohort 1). Intraoperative tumor consistency was graded by a neurosurgeon in 18 patients (cohort 2, comprising the 14 patients from cohort 1 plus 4 additional patients). The correlation between tumor stiffness and perfusion metrics was evaluated in cohort 1, as was the ability of perfusion metrics to predict intraoperative tumor consistency and discriminate histologic subtypes. Cohort 2 was analyzed for the ability of stiffness to determine intraoperative tumor consistency and histologic subtypes.RESULTS:The relative MTT was inversely correlated with stiffness (P = .006). Tumor stiffness was positively correlated with intraoperative tumor consistency (P = .01), while perfusion metrics were not. Relative MTT significantly discriminated transitional meningioma from meningothelial meningioma (P = .04), while stiffness did not significantly differentiate any histologic subtypes.CONCLUSIONS:In meningioma, tumor stiffness may be useful to predict intraoperative tumor consistency, while relative MTT may potentially correlate with tumor stiffness and differentiate transitional meningioma from meningothelial meningioma.

Meningioma is the most common primary intracranial tumor with an incidence of approximately 8 cases per 10,000 persons per year.¹ Radiosurgery, chemotherapy, or arterial embolization play supplementary roles, though surgical resection is the primary treatment for meningiomas. Tumor consistency is recognized as a major indicator of complete resection for meningiomas.² To date, various imaging modalities including T2-weighted images, diffusion MR imaging measurements, and magnetization transfer imaging have been investigated to predict meningioma consistency.³ However, there have been conflicting results, and no widely accepted method has been established.MR elastography (MRE) is a dynamic MR imaging–based technique used for the noninvasive measurement of the mechanical properties of soft tissue in vivo.⁴ Recently, the mechanical properties of the brain have been studied in normal aging,^5-9 Alzheimer disease,^6,10,11 Parkinson disease,¹² frontotemporal dementia,⁶ normal pressure hydrocephalus,⁶ and brain tumors,¹³ including menigniomas.^14-17 More recently, slip interface imaging using specialized processing of MRE data was shown to provide a dynamic measure of adherence between the tumor and the adjacent brain tissue.¹⁸The global shear modulus of soft biologic tissue can be influenced by the scale of perfusion,¹⁹ which relates to the topology and geometry of microvessels,²⁰ indicating a potential effect of perfusion on the macroscopic viscoelastic response of brain tissue. Previous MRE studies have indicated a close correlation between tissue perfusion and mechanical properties in the brain^21,22 and abdominal organs.²³ Moreover, in investigations of the pathologic determinants underpinning MRE data,^24,25 microvascular density, which is related to perfusion metrics,²¹ has been shown to contribute to the stiffness of soft brain tumor models in mice. Nevertheless, the perfusion conditions and mechanical properties of meningiomas have not been concurrently analyzed. Meningioma consistency and histologic subtype are indispensable factors influencing operative strategy and patient counseling. Recently, MRE has been increasingly recognized as a useful indicator of meningioma consistency,^14-17 while perfusion metrics provide physiologic and functional information about the tumor microenvironment. Because stiffness and perfusion status are intricately related, MRE and perfusion metrics may serve to preoperatively characterize the viscoelastic properties of meningiomas and further develop clinically applicable predictors for intraoperative tumor consistency. Relatively few studies have reported the relationship between stiffness ¹⁶ or perfusion metrics ^26-28 and histologic subtype, and no definite association has been established. Investigating the relationship of stiffness and perfusion metrics to intraoperative meningioma consistency and histologic subtypes may contribute to understanding and objective comparison of these techniques and provide valuable information affecting risk assessment, patient management, and workflow optimization.The purposes of this study were the following: 1) to investigate the correlation between stiffness and perfusion metrics, 2) to evaluate whether preoperative MRE and perfusion metrics could predict intraoperative tumor consistency, and 3) to explore the predictive value of stiffness and perfusion metrics in distinguishing among histologic subtypes of meningiomas.     

侵袭性垂体腺瘤:MRI与术中对照研究(附35例回顾分析)

目的:探讨MRI推断侵袭性垂体瘤质地、侵袭性的价值。方法:35例行MR检查侵袭性垂体瘤病人,测量T1WI及T2WI肿瘤信号与脑白质信号的比值和强化前后肿瘤T1WI信号强度比值,与其术中所见及术后病理对照,术中据肿瘤硬度分为质软、中等、硬;术后瘤体送检,结果进行统计学分析。结果:T2WI瘤体与白质信号比值与瘤体质地有明显相关性(P<0.01);MRI所示垂体瘤海绵窦及鞍周侵袭与术中及术后病理总符合率达85.3%。结论:MRI可以在术前准确预测侵袭性垂体瘤的质地、侵袭性。     

Assessment of radiotherapeutic effect on brain tumors by dynamic susceptibility contrast MR imaging: a preliminary report.

PURPOSE: The purpose of this study was to assess tumor vascularity of the brain by dynamic susceptibility contrast (DSC) MR imaging and to determine whether this method is clinically useful for monitoring radiation effects on brain tumors. We, furthermore, compared DSC MR imaging with single-photon emission computed tomography (SPECT) using technetium-99m diethylene-triamine-pentaacetic acid human serum albumin (99mTc-HSA-D) in the assessment of tumor vascularity in a limited numbers of cases. METHODS: Twelve patients with various kinds of brain tumors were studied. DSC MRI was performed on all patients before and after radiation therapy. SPECT using 99mTc-HSA-D was also performed in five patients. The rate of change in tumor blood volume in response to radiation therapy was evaluated with DSC MRI and SPECT. The rate of change in tumor volume in response to radiation was also measured. RESULTS: Ten patients were successfully studied. The rate of change in tumor blood volume correlated well between DSC MRI and SPECT. There was no significant correlation between the rates of change for tumor blood volume and tumor volume. Changes in tumor vascularity preceded the reduction in tumor volume seen following radiotherapy. CONCLUSION: DSC MRI provides information regarding radiation effects on tumor vessels that is not available with conventional MRI.     

磁共振弹性成像对肝脏局灶性良恶性肿瘤鉴别价值的初步研究

目的：探讨磁共振弹性成像(MRE)在肝脏良恶性肿瘤的诊断价值。方法对36例肝脏肿瘤患者(共39个病灶,其中肝细胞癌20个,血管瘤7个,胆管细胞癌5个,转移瘤3个,平滑肌脂肪瘤2个,癌肉瘤1个,巨淋巴增生1个)以及9例健康志愿者行 MRE。通过 FUNCTOOL 后处理获得肿瘤层面弹性图。测量、比较恶性肿瘤、良性肿瘤、恶性肿瘤周围组织、良性肿瘤周围组织和健康志愿者肝组织平均弹性值。结果恶性肿瘤平均弹性值[(7.39±1.70)kPa]明显高于良性肿瘤[(4.11±0.37)kPa,P <0.001]、恶性肿瘤周围组织[(3.50±0.73)kPa,P <0.001]、良性肿瘤周围组织[(2.61±0.45)kPa,P <0.001]及志愿者正常肝组织平均弹性值[(2.38±0.24)kPa,P <0.001]。恶性肿瘤周围组织平均弹性值[(3.50±0.73)kPa]明显高于良性肿瘤周围组织平均弹性值[(2.61±0.45)kPa, P <0.001]。良性肿瘤周围组织[(2.61±0.45)kPa]稍高于志愿者正常肝组织的平均弹性值[(2.38±0.24)kPa],两者无显著差异(P >0.05)。当取截断值为5.08 kPa 时,可鉴别区分良恶性肝肿瘤和正常肝实质。结论MRE 技术可用于肝脏局灶肿瘤性病变的诊断,有助于对肝脏良恶性肿瘤的鉴别。     

Morphologisches Erscheinungsbild neuroendokriner Tumoren des Dünndarms im MR-Enteroklysma

Purpose

To determine the value of MR enteroclysis (MRE) in the localization and characterization of primary carcinoid tumors of the small bowel and to describe typical imaging features.

Material and methods

Twenty patients with suspicion of primary small bowel carcinoid tumors (pCT) were recruited to undergo MRE following nasojejunal intubation and small bowel filling with 2.5 l of 0.5% methylcellulose solution under MR fluoroscopic guidance. MRE was performed on a 1.5 T MR scanner including T2w SSFSE, SSFP and contrast enhanced T1w GRE sequences with fat saturation. Fifteen patients, who subsequently had surgery for resection of their pCT, were retrospectively included in the study. All MRE were analyzed as for the presence, location, number, size, multiplicity and morphologic appearance of the pCT by two board certified radiologists in consensus. The conspicuity of the tumors was rated for each sequence type separately, according to a 4-point rating scale. Signal intensity measurements were performed in tumor and muscle. The presence of desmoplastic reaction, vascular involvement and lymph node metastases was also analyzed.

Results

pCT were correctly identified and localized in 14/15 patients. Due to their hyperenhancement tumors was best detected on contrast-enhanced T1w fat saturated GRE sequences. SSFSE was clearly inferior with the tumors being either hyperintense or isointense to muscle. pCT appeared as nodular intraluminal masses in 40% of the cases, as focal wall thickening in 33.3% and in 20% with both. Mean size was 25 (7–46 mm) with a tendency to smaller size for ileal tumors. MRE failed to depict superficial micronodular peritoneal spread in one patient. Desmoplastic reaction was observed in 73.3% of the cases with mesenteric masses exhibiting lower signal than the pCT due to fibrotic changes.

Conclusion

MRE is a valuable method for the detection and localization of primary carcinoid tumors, provided that appropriate bowel distension is achieved. Various characteristic morphologic features could be identified which may contribute to characterize pCT and their loco-regional metastases.     

Early-postoperative magnetic resonance imaging in glial tumors: prediction of tumor regrowth and recurrence

OBJECTIVE: This study investigated the value of early-postoperative magnetic resonance (EPMR) imaging in the detection of residual glial tumor and investigated the role of EPMR for the prediction of tumor regrowth and recurrence. METHODS AND MATERIALS: We retrospectively analyzed pre- and post-operative magnetic resonance imaging results from 50 adult patients who underwent surgical treatment for supratentorial glial tumor. There were glioblastoma multiforme in 25 patients, astrocytoma (grades II and III) in 11 patients, oligodendroglioma (grades II and III) in 9 patients, and oligoastrocytoma (grades II and III) in 5 patients. EPMR imaging was performed within 24 h after surgery. EPMR findings were compared with the neurosurgeon's intraoperative estimation of gross tumor removal. Patterns of contrast enhancement at the resection site, in residual and developing tumor tissue and blood at the resection site were evaluated on EPMR and in follow-up studies. 'Residual tumor' was defined as contrast enhancing mass at the operative site on EPMR. 'Regrowth' was defined as contrast enhancing mass detected on follow-up in the same location as the primary tumor. 'Recurrence' was defined as appearance of a mass lesion in the brain parenchyma distant from the resection bed during follow-up. RESULTS: Nineteen patients showed no evidence of residual tumor, regrowth, or recurrence on EPMR or any of the later follow-up radiological examinations. EPMR identified 20 cases of residual tumor. Follow-up showed tumor regrowth in 10 patients, and tumor recurrence in 1 case. EPMR showed contrast enhancement of the resection bed in 45 of the 50 patients. Four of the 20 residual tumors showed a thick linear enhancement pattern, and the other 16 cases exhibited thick linear-nodular enhancement. No thin linear enhancement was observed in the residual tumor group. Nine of the 10-regrowth tumors showed a thick linear-nodular enhancement pattern, and one exhibited thin linear enhancement in EPMR. For predicting regrowth tumor EPMR sensitivity was 91%, specificity was 100%, positive predictive value 1; negative predictive value was 0.9375. CONCLUSION: EPMR, depending on the surgical site enhancement pattern, is a valuable means of demonstrating residual tumors, and can be used to predict possible regrowth after surgery.     

High-resolution contrast-enhanced, susceptibility-weighted MR imaging at 3T in patients with brain tumors: correlation with positron-emission tomography and histopathologic findings

BACKGROUND AND PURPOSE: The purpose of this work was to demonstrate susceptibility effects (SusE) in various types of brain tumors with 3T high-resolution (HR)-contrast-enhanced (CE)-susceptibility-weighted (SW)-MR imaging and to correlate SusE with positron-emission tomography (PET) and histopathology. MATERIALS AND METHODS: Eighteen patients with brain tumors, scheduled for biopsy or tumor extirpation, underwent high-field (3T) MR imaging. In all of the patients, an axial T1-spin-echo (SE) sequence and an HR-SW imaging sequence before and after IV application of a standard dose of contrast agent (MultiHance) was obtained. Seven patients preoperatively underwent PET. The frequency and formation of intralesional SusE in all of the images were evaluated and correlated with tumor grade as determined by PET and histopathology. Direct correlation of SusE and histopathologic specimens was performed in 6 patients. Contrast enhancement of the lesions was assessed in both sequences. RESULTS: High-grade lesions demonstrated either high or medium frequency of SusE in 90% of the patients. Low-grade lesions demonstrated low frequency of SusE or no SusE. Correlation between intralesional frequency of SusE and histopathologic, as well as PET, tumor grading was statistically significant. Contrast enhancement was equally visible in both SW and SE sequences. Side-to-side comparison of tumor areas with high frequency of SusE and histopathology revealed that intralesional SusE reflected conglomerates of increased tumor microvascularity. CONCLUSIONS: 3T HR-CE-SW-MR imaging shows both intratumoral SusE not visible with standard MR imaging and contrast enhancement visible with standard MR imaging. Because frequency of intratumoral SusE correlates with tumor grade as determined by PET and histopathology, this novel technique is a promising tool for noninvasive differentiation of low-grade from high-grade brain tumors and for determination of an optimal area of biopsy for accurate tumor grading.     

18F-FDOPA PET imaging of brain tumors: comparison study with 18F-FDG PET and evaluation of diagnostic accuracy.

We evaluated the amino acid and glucose metabolism of brain tumors by using PET with 3,4-dihydroxy-6-(18)F-fluoro-l-phenylalanine ((18)F-FDOPA) and (18)F-FDG. METHODS: Eighty-one patients undergoing evaluation for brain tumors were studied. Initially, 30 patients underwent PET with (18)F-FDOPA and (18)F-FDG within the same week. Tracer kinetics in normal brain and tumor tissues were estimated. PET uptake was quantified by use of standardized uptake values and the ratio of tumor uptake to normal hemispheric tissue uptake (T/N). In addition, PET uptake with (18)F-FDOPA was quantified by use of ratios of tumor uptake to striatum uptake (T/S) and of tumor uptake to white matter uptake. The accuracies of (18)F-FDOPA and (18)F-FDG PET were determined by comparing imaging data with histologic findings and findings of clinical follow-up of up to 31 mo (mean, 20 mo). To further validate the accuracy of (18)F-FDOPA PET, (18)F-FDOPA PET was performed with an additional 51 patients undergoing brain tumor evaluation. RESULTS: Tracer uptake in tumors on (18)F-FDOPA scans was rapid, peaking at approximately 15 min after intravenous injection. Tumor uptake could be distinguished from that of the striatum by the difference in peak times. Both high-grade and low-grade tumors were well visualized with (18)F-FDOPA. The sensitivity for identifying tumors was substantially higher with (18)F-FDOPA PET than with (18)F-FDG PET at comparable specificities, as determined by simple visual inspection, especially for the assessment of low-grade tumors. Using receiver-operating-characteristic curve analysis, we found the optimal threshold for (18)F-FDOPA to be a T/S of greater than 1.0 (sensitivity, 96%; specificity, 100%) or a T/N of greater than 1.3 (sensitivity, 96%; specificity, 86%). The high diagnostic accuracy of (18)F-FDOPA PET at these thresholds was confirmed with the additional 51 patients (a total of 81 patients: sensitivity, 98%; specificity, 86%; positive predictive value, 95%; negative predictive value, 95%). No significant difference in tumor uptake on (18)F-FDOPA scans was seen between low-grade and high-grade tumors (P = 0.40) or between contrast-enhancing and nonenhancing tumors (P = 0.97). Radiation necrosis was generally distinguishable from tumors on (18)F-FDOPA scans (P < 0.00001). CONCLUSION: (18)F-FDOPA PET was more accurate than (18)F-FDG PET for imaging of low-grade tumors and evaluating recurrent tumors. (18)F-FDOPA PET may prove especially useful for imaging of recurrent low-grade tumors and for distinguishing tumor recurrence from radiation necrosis.     

Usefulness of whole-body (18)F-FDG PET in patients with suspected metastatic brain tumors.

The aim of this study was to evaluate the diagnostic value of whole-body (18)F-FDG PET imaging in the differentiation of metastatic brain tumor from primary brain tumor and in the localization of the primary lesion in patients with metastatic brain tumor. METHODS: The subjects consisted of 127 patients (77 men, 50 women; mean age +/- SD, 55 +/- 12 y) with brain masses that were suspected to be metastatic brain tumors on radiologic studies: 77 with confirmed metastatic brain tumor and 50 with primary brain tumor. Whole-body (18)F-FDG PET was performed on all patients. When the abnormal lesion was detected outside the brain, we interpreted the brain lesion as metastatic brain tumor. RESULTS: In 61 of the 77 patients with metastatic brain tumor, primary lesions were detected using whole-body (18)F-FDG PET. Of the remaining 16 patients (all false-negative cases), 7 were classified as metastases of unknown origin. In 47 of the 50 patients with primary brain tumor, whole-body (18)F-FDG PET did not show any other abnormal lesions. The sensitivity, specificity, positive and negative predictive values, and accuracy of PET for the detection of primary origin were 79.2%, 94.0%, 95.3%, 74.6%, and 85.0%, respectively. The most common primary origin of metastatic brain tumors on PET examination was lung cancer (48/61, 78.7%). The concordance rate between (18)F-FDG PET and conventional radiologic work-up was 80% in identifying primary lesion. Unknown bone or bone marrow metastases and unsuspected distant metastases were found in 14 patients (18%) and 24 patients (31%), respectively, on PET examination. CONCLUSION: Screening the patients with suspected metastatic brain tumors using whole-body (18)F-FDG PET could be helpful in differentiating metastatic brain tumor from primary brain tumor and in detecting the primary lesion.     

Magnetic resonance enteroclysis in the diagnosis of small-intestinal Crohn's disease: diagnostic accuracy and inter- and intra-observer agreement

Purpose: To evaluate the diagnostic accuracy and inter- and intra-observer agreement of magnetic resonance enteroclysis (MRE) in patients with or without Crohn's disease of the small intestine.

Material and Methods: 60 consecutive patients with or without Crohn's disease examined with MRE were included. Two observers independently reviewed the MRE examinations, searching for 12 pathological signs. The reference standard was ileoscopy or surgery of the terminal ileum performed in 41 patients.

Results: Crohn's disease of the small intestine was found in 24 (40%) patients. MRE findings of increased intestinal wall thickness, intestinal wall enhancement, intestinal wall ulcer, and inflammatory activity of the terminal ileum showed high sensitivity, specificity, and positive and negative predictive values. Intestinal stenosis had sensitivities ranging from 43% to 100%, depending on the cut-off value. Inter- and intra-observer agreement was good or excellent for most pathological signs. However, observer agreement of intestinal wall edema was only fair and moderate.

Conclusion: MRE evaluated Crohn's disease with a high diagnostic accuracy in the terminal ileum. Most MRE variables were evaluated with good or excellent observer agreement, indicating that the method was highly reproducible. Our study supports the notion that MRE is an appropriate method for diagnosing Crohn's disease.     

CT and MRI features of recurrent tumors and second primary neoplasms in pediatric patients with retinoblastoma

OBJECTIVE: The aim of our study was to describe the CT and MRI findings of recurrent tumors and second primary (malignant and benign) neoplasms in patients with retinoblastoma and to evaluate imaging features to assist in distinguishing them. MATERIALS AND METHODS: Records of 445 pathologically confirmed retinoblastomas were retrospectively reviewed. Thirty-four patients with recurrent retinoblastomas and 15 patients with second primary neoplasms who underwent CT and MRI were evaluated by two radiologists with agreement by consensus. RESULTS: Invasive patterns of recurrent tumors included type A, intraocular tumor (n = 13); type B, intraorbital tumor with spread into the optic nerve shown as enlargement and marked enhancement of the optic nerve on contrast-enhanced CT or MRI (n = 6); and type C, tumor extending to the lateral aspect of the orbit and invading the brain via the sphenoidal bone (n = 2). Thirty-eight percent of patients with recurrent tumors had distant metastases (n = 7) or leptomeningeal metastases (n = 6). Leptomeningeal metastases were found only in recurrent tumors. Second primary neoplasms included osteosarcoma (n = 5), rhabdomyosarcoma (n = 5), meningioma (n = 4), and other tumors (n = 3). A significant difference was seen between the patients' ages at the time of diagnosis of recurrent tumors and second primary neoplasms (p < 0.0001). Extraorbital tumors were found more frequently among second primary neoplasms than among recurrent tumors (p < 0.001). CONCLUSION: Both recurrent tumors and second primary neoplasms in patients with retinoblastoma often show characteristic imaging features. The tumor distribution on CT and MRI may help in differentiating recurrent tumors and second primary neoplasms.     

A combination of small bowel imaging methods: conventional enteroclysis with complementary magnetic resonance enteroclysis

AIM: The aim of this prospective study was to evaluate the overall findings of conventional enteroclysis (CE) with complementary magnetic resonance enteroclysis (MRE) in small bowel disease. METHODS: The study included 32 patients referred from various clinical departments, with known or suspected small bowel disease and abnormalities on CE. Immediately after CE, true fast imaging with steady-state precession (true FISP), and unenhanced and gadolinium-enhanced T1-weighted fast low-angle shot (FLASH) sequences with fat saturation were obtained. Mucosal, mural and luminal changes of the small bowel were evaluated by each technique. In addition, bowel wall thickening, bowel wall enhancement and perienteric changes were assessed by MRE. The radiological findings obtained were evaluated together as a combination, and the role of MRE in the determination of the activity and complications of the small bowel disease was assessed. Radiological findings were correlated with clinical evaluation and follow-up in all cases, including endoscopy in 14 cases and surgery in 5 cases. RESULTS: MRE provided important supplementary mural and extramural information, including degree of pathological wall thickness, mural enhancement pattern associated with disease activity, perivisceral collection, abscess formation, mesenteric fibrofatty proliferation, lymphadenopathy and increase in perienteric vascularity. Short strictures were not revealed on MRE; however, for patients with a history of abdominal malignancy, MRE helped characterize the level of any obstruction and the extent of the disease. CONCLUSION: We recommend MRE for patients who have findings of advanced inflammatory bowel disease or neoplasm on CE examination. The combination of these two techniques can provide important information on the degree and extent of the disorder.     

The role of diffusion-weighted imaging in patients with brain tumors.

BACKGROUND AND PURPOSE: Diffusion-weighted images (DWIs) have been used to study various diseases, particularly since echo-planar techniques shorten examination time. Our hypothesis was that DWIs and tumor apparent diffusion coefficients (ADCs) could provide additional useful information in the diagnosis of patients with brain tumors. METHODS: Using a 1.5-T MR unit, we examined 56 patients with histologically verified or clinically diagnosed brain tumors (17 gliomas, 21 metastatic tumors, and 18 meningiomas). We determined ADC values and signal intensities on DWIs both in the solid portion of the tumor and in the peritumoral, hyperintense areas on T2-weighted images. We also evaluated the correlation between ADC values and tumor cellularity in both gliomas and meningiomas. RESULTS: The ADCs of low-grade (grade II) astrocytomas were significantly higher (P =.0004) than those of other tumors. Among astrocytic tumors, ADCs were higher in grade II astrocytomas (1.14 +/- 0.18) than in glioblastomas (0.82 +/- 0.13). ADCs and DWIs were not useful in determining the presence of peritumoral neoplastic cell infiltration. The ADC values correlated with tumor cellularity for both astrocytic tumors (r = -.77) and meningiomas (r = -.67). CONCLUSION: The ADC may predict the degree of malignancy of astrocytic tumors, although there is some overlap between ADCs of grade II astrocytomas and glioblastomas.     

Review of MR elastography applications and recent developments

The technique of MR elastography (MRE) has emerged as a useful modality for quantitatively imaging the mechanical properties of soft tissues in vivo. Recently, MRE has been introduced as a clinical tool for evaluating chronic liver disease, but many other potential applications are being explored. These applications include measuring tissue changes associated with diseases of the liver, breast, brain, heart, and skeletal muscle including both focal lesions (e.g., hepatic, breast, and brain tumors) and diffuse diseases (e.g., fibrosis and multiple sclerosis). The purpose of this review article is to summarize some of the recent developments of MRE and to highlight some emerging applications. J. Magn. Reson. Imaging 2012;36:757–774. © 2012 Wiley Periodicals, Inc.     

多层螺旋CT灌注成像在脑肿瘤诊断中的临床研究

目的: 探讨多层螺旋CT(multislice spiral CT,MSCT)脑肿瘤灌注成像方法及其临床应用价值.材料和方法: 对27例脑肿瘤先用常规CT平扫确定肿瘤中心实质部位,然后进行MSCT灌注扫描.扫描图像经ADW4.0工作站PerfusionⅡ软件进行计算,得出灌注图像及参数,包括脑血流量(CBF)、脑血容量(CBV)、造影剂平均通过时间(MTT)和肿瘤微血管表面通透性(PS).结果: 27例中,脑胶质瘤7例、脑膜瘤8例、脑转移瘤8例、颅咽管瘤2例,淋巴瘤、血管母细胞瘤各1例.27例灌注图像均可以清晰显示肿瘤的大小、轮廓,清晰地区分肿瘤和水肿;不同类型肿瘤的CBF、CBV、MTT及PS值不尽相同,灌注伪彩图表现不同;PS图能清晰显示脑肿瘤的实质部分及微血管通透性.结论: MSCT灌注成像对脑肿瘤血流灌注的定量研究提供了新的方法,对了解脑肿瘤内部血流状态及微血管通透性的改变有一定的价值.     

Surveillance imaging and cost effectivity in pediatric brain tumors

OBJECTIVE: The purpose of this study was to determine the role and cost effectiveness of surveillance imaging at the management of pediatric brain tumors. MATERIALS AND METHODS: In this study, the imaging and clinical finding of 59 patients who had been diagnosed and followed by the Dokuz Eylul University Pediatric Oncology Group as primary central nervous system tumors between 1988 and 2000 were retrospectively evaluated. RESULTS: We found that the 87.5% of tumor recurrence occurs within 21 months and 93.8% occur within 29 months. About 25% of these recurrences were asymptomatic and these (n=16) could be detected by surveillance imaging with a frequency rate of 1.59%. The cost of imaging for our patients was calculated to be 788 US$ (mean) for a follow-up period of 24 months which would have been 739 US$ if a standard surveillance protocol would have been followed. CONCLUSION: Surveillance imaging is an effective follow-up in detecting symptomatic recurrence in pediatric brain tumors.     

Accelerating MR elastography: a multiecho phase-contrast gradient-echo sequence

PURPOSE: To demonstrate the feasibility of using a multiecho phase-contrast (PC) gradient-echo sequence with motion-sensitizing gradient (MSG) to accelerate MR elastography (MRE) acquisitions in comparison to single-echo PC sequences. MATERIALS AND METHODS: The sequence was implemented and compared with a conventional single-echo sequence as the standard of reference in both agarose phantoms and in vivo in the biceps of three healthy volunteers. For reconstruction of the elasticity modulus, a local frequency estimation (LFE) algorithm was used. ETL factors of 1-16 were evaluated. RESULTS: Phantom experiments demonstrated excellent consistency between single-echo and multiecho measurements in terms of wave equivalency, SNR, and reconstructed shear modulus. Additionally, the in vivo MRE examinations showed an excellent correspondence to the single-echo results. Minor loss of wave amplitude was observed at higher ETL factors. CONCLUSION: The results demonstrate that a multiecho sequence is suitable for accelerating MRE in nearly homogeneous tissue, such as muscle. It provides equivalent elasticity values in a significantly reduced scan time compared to a single-echo sequence. The maximum achievable ETL factor must be individually determined for the target tissue.