Magnetic Resonance Imaging (MRI) Appearances of Syringohydromyelia

Magnetic resonance imaging (MRI) examination of the spinal cord is now a first-line in vestigation for the evaluation of suspected syringohydromyelia. It is an accurate, non-invasive means of detecting cavities within the spinal cord and for assessing spinal cord size and the position of the cerebellar tonsils. It has considerable advantages over post-myelographic computerised tomography (CT). The current study discusses our initial experience of thirteen surgically proven cases of syringomyelia with special reference to appearances on T 1 and T2 weighted images and a discussion of the apparently confusing appearances of the cavities on the T2 weighted images.     

Magnetic Resonance Imaging (MRI) of Pseudosyrinxes

Six patients whose post-myelographic computed tomography (CT) showed syringomyelia but whose clinical findings were not consistent were evaluated with magnetic resonance imaging (MRI). In five of these patients no cavity was seen with MRI. A cavity was demonstrated in the sixth case but not in the region of abnormali ty on CT. MRI confirmed the clinical impression that intake of contrast into the cord did not represent a sryinx cavity. Possible causes are discussed. The term ‘pseudosyrinx’ is used for such a situation.     

磁共振功能成像在脑肿瘤诊断中的应用

目前,MRI因软组织分辨率高、无辐射及多平面成像等优势已成为脑肿瘤疾病的一种常规检查手段。近年来,随着磁共振技术的发展及磁场强度的增加,一些新的MR功能成像技术已开始越来越多的应用于临床,如磁共振波谱、脑功能成像、灌注成像、磁敏感加权成像、弥散张量成像等,主要用于脑肿瘤之间及脑肿瘤与非肿瘤性疾病的鉴别、肿瘤的分级、指导外科术式的选择、放疗方案的制订等。     

The Role of Magnetic Resonance Imaging in Brachytherapy

The application of magnetic resonance imaging (MRI) in image-guided brachytherapy has expanded rapidly over the past two decades. In cervix cancer, significant improvements in overall survival, local control and long-term morbidity have been shown in patients treated with MRI-guided brachytherapy, changing clinical practice and directing an international approach to standardise the technique; unifying adaptive target volume definition and dose reporting. MRI-guided prostate brachytherapy has significantly improved the accuracy of tumour and organ-at-risk delineation, facilitating targeted implantation and dose optimisation. It also has potential to improve clinical outcomes through enhancement of the therapeutic ratio and the identification of dominant lesions that can be the targets of sub-volume boosting and salvage therapy. However, MRI-guided brachytherapy presents a number of logistical and financial challenges in modern healthcare systems, requiring technologically advanced imaging and planning techniques, as well as robust safety and quality assurance procedures. A collaborative, multidisciplinary approach involving clinical oncologists, radiologists, medical physicists, therapy radiographers, nurses and technical staff is therefore critical to its successful incorporation into any clinical brachytherapy workflow. In this overview we evaluate the current role of MRI in image-guided brachytherapy, primarily in cervix and prostate cancer, but also in other tumour sites, and review its potential future developments in the context of both clinical and research spheres.     

Efficacy of Proton Magnetic Resonance Spectroscopy Inclinical Decision Making for Patients with Suspected Malignant Brain Tumors

We wished to determine the utility of single voxel proton (¹H) magnetic resonance spectroscopy (MRS) when used as an alternative or adjunct to brain biopsy in patients harboring lesions suggestive of brain tumors identified by MRI scan. Fifteen patients (age 7–58 years) with MRI scans and clinical histories suggestive of primary brain tumors underwent single voxel ¹H-MRS. MRS (16 regions of interest in 15 patients) was used to aid in differentiation between tumor and other pathologies such as stroke or demyelinating plaque (n=6), radiation necrosis (n=5), or edema (n=5). Spectra were quantified to determine absolute molar values of N-acetyl aspartate (NAA), choline (Cho), creatine (Cr), lactate (LAC), and myo-inositol (mI), metabolite ratios relative to Cr were calculated, and spectra were interpreted based on metabolite ratios. Subsequent clinical management was based on MRS interpretation, and patients were then followed to determine if MRS interpretation accurately predicted clinical outcome or surgical findings. Mean follow-up was 12.5 months (range 3–28 months). MRS suggested the presence of recurrent tumor in 7 cases, all of which were subsequently confirmed by tumor resection (n=4) or disease progression (n=3). MRS suggested the presence of new tumor in 1 case, subsequently confirmed by surgical resection. MRS suggested the presence of necrosis in 3 patients; all 3 remained radiographically stable during the follow-up period, and one was confirmed by stereotactic biopsy. MRS suggested non-neoplastic lesions in 4 cases, 3 of whom were followed until radiographic resolution of lesions and one of which was confirmed as a pyogenic abscess via stereotactic aspiration. Overall, MRS accurately predicted the pathological nature and clinical outcome of lesions in 15/16 (96%) situations, influenced clinical decision making in 12 cases, and altered surgery planning in 7 patients. In appropriate circumstances MRS can reduce the need for biopsy and provide an important guide for clinical decision-making in difficult cases.     

磁共振成像诊断原发性肝癌评价

本文分析了１６５例原发性肝癌的磁共振成像（ＭＲＩ）价值。ＳＥ序列为Ｔ１加权成像（Ｔ１ＷＩ）；ＲＡＲＥ序列为Ｔ２加权成像（Ｔ２ＷＩ）。在Ｔ１ＷＩ上对肝脏结构显著显示清楚，而Ｔ２ＷＩ上主要对肝癌信号异常敏感性高，故对肝癌的范围、大小显示较为清楚。两处序列联合应用以及多层多平面横断加冠状切层可以精楚构画肝癌的部位、大小和范围。本研究提示，其敏感性ＭＲＩ比ＣＴ略高，但无统计学意义。ＭＲＩ优于Ｂ超，但不及Ｂ     

鼻咽癌颅底骨质破坏放疗前后MRI评估

[目的]探讨磁共振(MRI)对鼻咽癌颅底骨侵犯的诊断价值。[方法]分析2003年7月至2004年12月35例颅底骨质破坏初诊鼻咽癌患者放疗前后MRI的变化。[结果]35例鼻咽癌患者放疗前均存在程度不等的颅底骨质破坏,MRI可见T1WI骨髓高信号消失及压脂增强后明显强化。经放射治疗,35例患者均呈放疗后状态。[结论]MR平扫及增强扫描图像对鼻咽癌TNM分期及疗效判断有重要价值。     

Classification of Brain Tumor from Magnetic Resonance Imaging Using Vision Transformers Ensembling

The automated classification of brain tumors plays an important role in supporting radiologists in decision making. Recently, vision transformer (ViT)-based deep neural network architectures have gained attention in the computer vision research domain owing to the tremendous success of transformer models in natural language processing. Hence, in this study, the ability of an ensemble of standard ViT models for the diagnosis of brain tumors from T1-weighted (T1w) magnetic resonance imaging (MRI) is investigated. Pretrained and finetuned ViT models (B/16, B/32, L/16, and L/32) on ImageNet were adopted for the classification task. A brain tumor dataset from figshare, consisting of 3064 T1w contrast-enhanced (CE) MRI slices with meningiomas, gliomas, and pituitary tumors, was used for the cross-validation and testing of the ensemble ViT model’s ability to perform a three-class classification task. The best individual model was L/32, with an overall test accuracy of 98.2% at 384 × 384 resolution. The ensemble of all four ViT models demonstrated an overall testing accuracy of 98.7% at the same resolution, outperforming individual model’s ability at both resolutions and their ensembling at 224 × 224 resolution. In conclusion, an ensemble of ViT models could be deployed for the computer-aided diagnosis of brain tumors based on T1w CE MRI, leading to radiologist relief.     

Magnetic Resonance Imaging of Intramedullary Spinal Cord Tumors

The advent of MRI has significantly changed the diagnosis of spinal cord tumors. Standard imaging provides excellent localization and characterization of the tumor in a noninvasive fashion. Exact histologic diagnosis of the two most common tumors, ependymoma and astrocytoma, remains elusive but there are some suggestive imaging characteristics. It is hoped that some of the newer MR imaging sequences will improve characterization of the tumor and thereby influence therapy. Several of these pulse sequences are already used routinely in brain imaging. Evaluation of new imaging sequences in the spine has lagged behind brain MR imaging, mainly due to technical factors. Work on animal spine models and extrapolation from brain imaging studies suggest that it is only a matter of time before some of these techniques become clinically relevant.     

The contribution of Magnetic Resonance Spectroscopy and echoplanar perfusion-weighted MRI in the initial assessment of brain tumours

Summary Conventional Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) are the cornerstone in the initial evaluation of brain tumours. The purpose of this study is to evaluate the contribution of Magnetic Resonance Spectroscopy (MRS) and Perfusion-weighted MRI to distinguish malignant from benign tumours.We included 55 patients diagnosed with single brain tumour by CT and MRI, and final histopathological verification of the tumour type: 25 were low-grade gliomas, 8 anaplastic gliomas, 11 glioblastomas, and 11 solitary metastases. We carried out brain MRS and dynamic perfusion-weighted echoplanar MRI in all cases. Perfusion was assessed in the centre of the lesion and in the area of maximum contrast-enhancement.In MRS, we found significant differences in Choline/Creatine ratios in relation to the tumour type with the highest values in high-grade gliomas and metastases. A Ch/Cr ratio equal or higher than 1.78 predicted malignancy at 80% sensitivity and 73% specificity. We found no significant differences in the relative cerebral blood volume (rCBV) for every type of tumour. The mean rCBV was 1.24 for benign tumours and 1.5 for the malignant ones(1.24 for low-grade gliomas, 1.91 for anaplastic gliomas, 1.03 for glioblastomas, and 1.57 for metastases).We conclude that, individually considered, MRS is superior to Perfusion-weighted MRI in the initial assessment of brain tumours. Perfsion MRI has not demonstrated predictive power to distinguish malignant from benign tumours.     

血管母细胞瘤的 MRI 及 MRS 特点分析

目的：对血管母细胞瘤的 MRI 及 MRS 特点进行分析,提高对该病的认识并探讨 MRI 联合 MRS 检查对该病的诊断价值。方法：回顾性分析经病理证实的21例血管母细胞瘤的临床及影像学资料,分析病变部位、MRI 及 MRS 特点及其与患者的预后关系。结果：21例病例中,囊实性病变19例,呈典型“大囊小结节”样改变,实质性者2例。MRI 表现为病变囊性部分呈长 T1长 T2信号,增强扫描18例未见强化,1例囊壁轻微强化;附壁结节及病变实质部分 T1WI 呈等或稍低信号,T2WI 呈等或稍高信号,增强扫描明显强化,实质性病变内可见血管流空、脂肪及脑膜强化信号。MRS 示病变实性部分 Cho 及 Cr 峰明显增高,NAA 峰明显减低,可见高耸的“LL”峰。3例 VHL 中2例伴有其他肿瘤。结论：血管母细胞瘤的 MRI 表现具有特征性,在掌握典型血管母细胞瘤 MRI 特点的基础上,MRS 可以提供更多信息以提高对该病的早期诊断率。     

前列腺磁共振扩散张量成像研究进展

扩散张量成像（DTI）是一种可以无创反映活体组织内水分子扩散的各向异性程度的磁共振功能成像方法,在前列腺的应用尚处于初步研究阶段。DTI能够提供前列腺的组织微观结构信息,并直观显示前列腺纤维走形,有助于前列腺疾病的诊断及鉴别诊断。文章就DTI在前列腺的研究进展及临床应用近况进行综述。     

颞叶放射性脑病磁共振成像的特征分析

背景与目的：鼻咽癌(nasopharyngeal carcinoma,NPC)放疗后放射性脑病(radiation encephalopathy,REP)的表现形式多样,对其多样性表现的报道并不多,本研究观察NPC放射性脑病的磁共振成像(magnetic resonance imaging,MRI)形态学表现特征并探讨其诊断价值。方法：对104例NPC患者共160处病灶经MRI诊断为颞叶REP的MRI资料进行回顾性分析。在NPC放射治疗8个月～13年进行MRI检查,成像序列包括T1WI,T2WI,111处病灶作了T1WI Gd—DTPA增强,37处病灶有水抑制反转恢复(fluid attented inversion recovery FLAIR)检查,其中2例有磁共振脑血流灌注成像(MR perfusion weighted imaging,MR PWI)。结果：104例REP中累及单侧颞叶48例,双侧颞叶56例,共160个病灶。脑白质病变在T2WI为高信号,信号可均匀一致,但其中59个病灶在高信号区内出现不均匀低信号影;有91个病灶同时伴有灰质病变,表现为T1WI低信号,T2WI高信号;在111个病灶T1WI Gd—DTPA检查中91个病灶出现强化灶;有5个病灶出现出血及含铁血黄素沉着。结论：鼻咽癌放射性脑病表现具有多样性,除了常见的脑白质病变外,脑灰质病变、脑出血及含铁血黄素沉着及血脑屏障破坏等均比较常见;MRI能清楚地显示这些病变。     

Brain MRI findings in two cases with eclampsia

Neurological complications in patients with eclampsia are varied and include headache, visual disturbances, focal neurological deficits, altered mental status and coma. Occasionally, a focal neurological deficit includes a variety of visual disturbances. The pathophysiology of CNS abnormalities in patients with eclampsia is uncertain. Our cases, combined with a review of the literature, demonstrate that there is no correlation among severity of hypertension, parity, and location of lesions at initial magnetic resonance (MR) imaging findings or between the severity of hypertension and neurological symptoms. Two typical patterns are seen on MR images of patients with eclampsia. Lesions in the region of the posterior cerebral circulation are most common and are frequently associated with visual disturbances. Although there are lesions in the deep white matter or basal ganglia, a focal neurological deficit or alterations in mental status may not develop. This demonstrates the sensitivity of MR imaging in the detection of abnormalities in patients with eclampsia, even those without neurological deficits.     

Dynamic Contrast-enhanced Magnetic Resonance Imaging: Applications in Oncology

Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) allows functional characterisation of tissue perfusion characteristics and acts as a biomarker for tumour angiogenesis. It involves serial acquisition of MRI images before and after injection of contrast, as such, tissue perfusion and permeability can be assessed based on the signal enhancement kinetics. The ability to evaluate whole tumour volumes in a non-invasive manner makes DCE MRI especially attractive for potential oncological applications. Here we provide an overview of the current research involving DCE MRI as a biomarker for the diagnosis and characterisation of malignancies, prediction of the therapeutic response and survival outcomes, as well as radiation therapy planning.     

磁共振功能成像在脑胶质瘤侵袭性行为评价中的作用

脑胶质瘤的侵袭常沿着有髓神经纤维和血管基底膜途径进行。MR功能成像包括MRS、PWI和DWI．具有一定的分子成像的能力。MRS代谢物浓度变化可以明确瘤体和瘤周的代谢物变化。Cho／Cr值自近瘤周区向远瘤周区有逐渐降低的趋势．而NAA／Cr则有升高趋势．符合胶质瘤沿白质纤维自近向远侵袭性生长的特点。MRI灌注成像rCBV对胶质瘤分级的预测具有一定价值。MRI弥散成像通过反映组织内水分子的扩散特性反映脑内肿瘤的病理变化,常以扩散张量成（DTI）、表观扩散系数（ADC）和白质纤维柬追踪~（V13来间接反映胶质瘤的生物学侵袭性特点。MR功能成像在评价脑胶质瘤侵袭性上具有一定价值,临床医生应把传统MRI与多种功能成像技术联合应用来提高MRI对胶质瘤侵袭性的认识。