Post-therapeutic magnetic resonance imaging of bone tumors

Magnetic resonance imaging plays an important role in the therapeutic follow-up of patients with bone tumors. Follow-up includes monitoring of response to neoadjuvant chemotherapy prior to limb salvage surgery, assessment of local recurrence of tumor, differentiation of suspected recurrence from hematopoietic bone marrow reconversion, inflammation, seroma, or reactive tissue, and detection of therapeutic complications, such as osteonecrosis, infection, and radiation-induced sarcoma. This article reviews the role of magnetic resonance imaging in the therapeutic follow-up of patients with bone tumors.     

Diffusion tensor magnetic resonance imaging of brain tumors

DTI seems to offer the possibility of adding important information to presurgical planning. Although experience is limited, DTI seems to provide useful local information about the structures near the tumor, and this seems to be useful in planning. In the future, DTI may provide an improved way to monitor intraoperative surgical procedures as well as their complications. Furthermore, evaluation of the response to treatment with chemotherapy and radiation therapy might also be possible. Although DTI has some limitations, its active investigation and further study are clearly warranted.     

Otogenic intracranial inflammations: role of magnetic resonance imaging

The clinical course of acute otitis media is usually short, and the process terminates because of the host's immune system, the infection-resistant properties of the mucosal linings, and the susceptibility of the major organisms (beta-hemolytic streptococcus or pneumococcus) to penicillin. However, a small proportion (1% to 5%) of untreated or inadequately treated patients may experience complications. Prior to the development of an intracranial complication of otomastoiditis, warning symptoms or signs may be evident; these include severe earache, severe headache, vertigo, chills and fever, and meningeal symptoms and signs. Increasing headache, particularly temporoparietal headache near the affected ear, often indicates an impending intracranial complication. This symptom, often the only indication of an epidural abscess, demands prompt investigation and medical and surgical intervention. In our experience, computed tomography (CT) permits accurate diagnosis of acute coalescent or latent (masked) mastoiditis and its associated complications. However, magnetic resonance imaging (MRI) remains the study of choice to evaluate otogenic intracranial complications. This article demonstrates the important role of MRI in diagnosing various stages of acute otomastoiditis and its associated complications.     

Magnetic resonance imaging and proton magnetic resonance spectroscopy of intracranial epidermoid tumors

Intracranial epidermoid tumors or cysts are considered benign lesions. Differentiation of epidermoid tumors from arachnoid cysts is important for appropriate patient care because the treatment is different for each lesion. Arachnoid cysts can appear very similar to epidermoid tumors on computed tomography (CT). Epidermoid tumors can grow in the cerebellopontine angle (CPA) cistern, the most common location of these lesions, resulting in trigeminal neuralgia and facial paralysis. Treatment for epidermoid tumors is exclusively surgery. Arachnoid cyst, on the other hand, is a benign condition that rarely produces symptoms. Recent advances in magnetic resonance imaging (MRI) have allowed more accurate imaging diagnosis of epidermoid tumors. This article reviews the recent advances in MRI using conventional T1W, post-contrast T1W, T2W, steady-state free precession imaging, fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and proton magnetic resonance spectroscopy (MRS) in the imaging diagnosis of epidermoid tumors.     

Langerhans histiocytosis of temporal bone: role of magnetic resonance imaging

Langerhans cell histiocytosis (LCH) may involve nearly every organ of the body. In children, head and neck involvement has been reported in as many as 82% of patients. Sites of head and neck involvement include skull, temporal bone, orbit, mandible, maxilla and cervical nodes. In addition, patients may have coexisting central nervous system (CNS) involvement adjacent to, or remote from, osseous lesions. Magnetic resonance imaging (MRI) of the temporal bone in patients with LCH is ideal for evaluating the extracranial extent of the soft-tissue mass and is complementary to computed tomography (CT) in the assessment of osseous erosion. MRI is superb in the evaluation of intracranial extension, usually into the middle cranial fossa, and of patency of adjacent vascular structures. It is the imaging modality of choice to evaluate patients with suspected CNS involvement of LCH, which includes lesions of the infundibulum, cerebrum, cerebellum, and extra-axial spaces.     

Diffusion-weighted magnetic resonance imaging for the evaluation of musculoskeletal tumors

Conventional MR imaging provides low specificity in the differential diagnosis of musculoskeletal (MSK) tumors and is unable to offer information about the extent of tumoral necrosis and the presence of viable cells, information crucial to assess treatment response and prognosis. Therefore, diffusion-weighted imaging (DWI) is now used with conventional MR imaging to improve diagnostic accuracy and treatment evaluation. This article discusses the technical aspects of DWI, particularly the quantitative and qualitative interpretation of images in MSK tumors. The clinical application of DWI for tumor detection, characterization, differentiation of tumor tissue from others, and assessment of treatment response are emphasized.     

磁共振成像在胎儿检查中的应用价值

目的 探讨磁共振成像在胎儿检查中的应用价值。方法回顾性分析B超发现胎儿发育异常并经引产或手术证实的8例孕妇胎儿MR图像，并将MR与B超的图像进行对比分析。结果 胎儿发育异常的病种有：前置胎盘2例，胎儿肾脏发育不良1例，先天性膈疝1例，羊水过少2例，腹膜后畸胎瘤1例，小脑发育不良1例。与B超相比，MRI可清晰显示B超发现的胎儿异常。结论磁共振成像在胎儿检查中具有重要的临床应用价值，当B超怀疑胎儿发育异常时MRI更是重要的补充。     

3.0T磁共振成像对四肢肿瘤的诊断价值

目的:评价3.0T磁共振成像对四肢肿瘤各征象的显示特征及诊断价值.方法:回顾性分析经病理证实的34例四肢肿瘤患者3.0T MRI影像学资料,分析肿瘤生长部位、体积大小与良、恶性的关系.结果:上肢肿瘤4例,良性2例、恶性2例;下肢肿瘤30例,其中大腿肿瘤19例,恶性13例、良性6例,小腿肿瘤11例,恶性4例、良性7例.良性肿瘤体积小于恶性肿瘤体积(P＜0.05).根据MRI特征,术前诊断四肢肿瘤良、恶性准确率为91.2%.结论:3.0T磁共振成像可作为四肢肿瘤临床诊断及手术治疗的影像学方法.     

Exertional compartment syndrome and the role of magnetic resonance imaging

A 47-yr-old woman presented with a 1-yr history of progressive bilateral anterior lower leg pain and swelling with walking, which resolved 10 min after activity. Postexercise (forced dorsiflexion) magnetic resonance imaging revealed increased T2 signal intensity in the entire anterior muscle compartment, and anterior compartment pressures were elevated at rest and postexercise. Chronic exertional compartment syndrome can occur in some patients after even minimal physical activities, and magnetic resonance imaging without the use of radioisotopes was a useful adjunct for diagnosis.     

心血管MRI第一部分--磁共振基本物理原理及成像策略

MRI以其独特的优势广泛应用于临床,特别是在心血管系统疾病中的诊断价值得到日益体现。心血管MRI(CMR)能无创地一站式评价心血管的解剖、功能、心肌灌注和病变的组织特性,并且评价的可重复性高。CMR成像技术内容丰富,尚具挑战性,需克服心脏自身和随呼吸的运动伪影。MRI的软硬件系统性能不断提高,特别是磁场强度革命性地提升,使得成像技术不断地完善和更新。作者用4个篇章分别阐明上述MRI尤其是CMR的基本成像原理及技术要点,致力于用简明易懂的语言使大多数放射科一线工作者能轻松愉悦地领悟MRI尤其是CMR的魅力。此文为第一部分,归纳MRI基本物理原理及MR图像的产生过程。     

Icteric-type hepatoma: magnetic resonance imaging and magnetic resonance cholangiographic features

Background: We evaluated the imaging features of magnetic resonance imaging (MRI) and magnetic resonance cholangiography (MRC) of icteric-type hepatoma and correlated these with the findings of endoscopic retrograde cholangiography (ERC), percutaneous cholangiography, and surgery. Methods: Thirteen patients with viral hepatitis complicated by cirrhosis of the liver and obstructive jaundice underwent MRC and dynamic MRI. Five patients received percutaneous transhepatic cholangiography and drainage; one of these patients also underwent resection of the left hepatic lobe. Another patient received MRC followed by thrombectomy and T-tube insertion. ERC and endoscopic nasobiliary drainage were performed in another patient for bile diversion. Results: Primary liver tumors and dilatation of biliary system were demonstrated in all patients. No capsule formation could be found in any primary liver tumors. MRI showed the simultaneous presence of an intraluminal tumor in the portal trunk and common hepatic duct in eight patients. Three different MRC features were found: (a) an oval defect in the hilar bile duct(s) with dilated intrahepatic ducts (n= 9), (b) dilated intrahepatic ducts with missing major bile ducts (n= 2), and (c) localized stricture of the hilar bile duct(s) (n= 2). Conclusion: The presence of one or more of the following features in multiplanar MRI and MRC help to identify this rare, specific type of hepatocellular carcinoma: (a) the presence of an intraluminal tumor in both the portal trunk and the common hepatic duct, (b) enhancement of the intraluminal tumor in the common hepatic duct on the arterial phase, (c) type I MRC feature, and (d) hemobilia, blood clot within the gallbladder, and/or type II MRC feature. Received: 12 January 2000/Revision accepted: 12 July 2000     

Clinical magnetic resonance imaging of brain tumors at ultrahigh field: a state-of-the-art review

With the advancement of the magnetic resonance (MR) technology, the whole-body ultrahigh field MR system operated from 7 to 9.4 T becomes feasible for the routine patient imaging in clinical settings. The associated potentials and challenges from the perspectives of technology, physics, and biology as well as clinical application of the ultrahigh field MR systems are different from those systems operated at 3 T, 1.5 T, or lower field strength. In this article, we will present our initial experiences of brain tumor imaging using the 7 and 8 T whole-body MR systems at the Ohio State University Medical Center and provide a brief overview pertinent to the ultrahigh field clinical MR systems.     

Endometrial cancer: magnetic resonance imaging

Carcinoma of the endometrium is the most common invasive gynecologic malignancy of the female genital tract. Clinically, patients with endometrial carcinoma present with abnormal uterine bleeding. The role of magnetic resonance imaging (MRI) in endometrial carcinoma is disease staging and treatment planning. MRI has been shown to be the most valuable imaging mod-ality in this task, compared with endovaginal ultrasound and computed tomography, because of its intrinsic contrast resolution and multiplanar capability. MRI protocol includes axial T1-weighted images; axial, sagittal, and coronal T2-weighted images; and dynamic gadolinium-enhanced T1-weighted imaging. MR examination is usually performed in the supine position with a phased array multicoil using a four-coil configuration. Endometrial carcinoma is isointense with the normal endometrium and myometrium on noncontrast T1-weighted images and has a variable appearance on T2-weighted images demonstrating heterogeneous signal intensity. The appearance of noninvasive endometrial carcinoma on MRI is characterized by a normal or thickened endometrium, with an intact junctional zone and a sharp tumor-myometrium interface. Invasive endometrial carcinoma is characterized disruption or irregularity of the junctional zone by intermediate signal intensity mass on T2-weighted images. Invasion of the cervical stroma is diagnosed when the low signal intensity cervical stroma is disrupted by the higher signal intensity endometrial carcinoma. MRI in endometrial carcinoma performs better than other imaging modalities in disease staging and treatment planning. Further, the accuracy and the cost of MRI are equivalent to those of surgical staging.     

Three-dimensional magnetic resonance imaging

Three-dimensional surface reconstruction images of the heart and great vessels can be produced from contiguous sequences of ECG-triggered MR scans in patients with congenital heart disease. The methods allow separation of the epi- and endocardial surfaces and definition of the enclosed blood volumes on a slice-by-slice basis. Surface reconstruction images have value in communicating the results of MR examinations to clinicians in cases where cardiac morphology is unusually complex; in depicting intracardiac defects, size, and location; and in aiding the study of pulmonary venous drainage. This method can be practical in studying cardiac morphologic abnormalities and especially in planning cardiac surgery.     

Intravascular magnetic resonance imaging

The purpose of this article is to review the current state of the art with respect to intravascular magnetic resonance imaging, including intravascular coils, their implementation for plaque identification and characterization, and strategies for future approaches to coronary imaging and other cardiovascular applications.     

Fetal magnetic resonance imaging

Ultrafast magnetic resonance imaging (MRI) sequences have changed the use of MRI to evaluate fetal abnormalities. Currently, the best application is the evaluation of suspected brain abnormalities found on ultrasound. MRI differentiates the various types of fetal ventriculomegaly. Superior posterior fossa visualization allows differentiation of Dandy-Walker malformation from a large cisterna magna. Anomalies of the corpus callosum can be seen. MRI also is valuable in the evaluation of fetal giant neck masses for planning delivery of the baby and surgery for life-threatening airway obstruction. In the chest, MRI differentiates masses such as diaphragmatic hernia, cystic adenomatoid malformation, and sequestration, and it aids in planning fetal surgery because MRI directly visualizes the position of the lung, liver, and bowel.