MR imaging of the normal and abnormal clivus

We retrospectively reviewed 330 T1-weighted sagittal images, 80 T2-weighted sagittal images, and 83 gadopentetate-dimeglumine-enhanced scans of normal adults to determine the MR appearance of the normal adult clivus. MR images of 21 patients with an abnormal clivus (19 with tumor invasion and two with marrow reconversion) were also evaluated retrospectively and compared with those of the control group to assess MR features distinguishing the two groups. Our study revealed that a normal adult clivus consisted of low- and high-intensity portions mixed in various proportions on T1-weighted images. The low-intensity portion was isointense or hyperintense relative to the pons and always contained foci of bright signal intensity. The low-intensity tumor of a pathologic clivus tended to be hypointense relative to the pons (17/19), and was completely devoid of foci of bright signal intensity. The normal adult clivus was approximately isointense relative to the pons on T2-weighted images. Clival tumors were grossly hyperintense relative to the pons on T2-weighted images in 11 of 17 patients. In the remaining six patients, either a portion of or the entire lesion was isointense relative to the pons and, therefore, was not detectable on T2-weighted images. A normal adult clivus can enhance to some degree (19/83). Clival tumors were found to enhance intensely. A clivus of very low signal intensity (signal void) on T1- or T2-weighted images was always abnormal. The clivus with marrow reconversion was uniformly hypointense relative to the pons on T1-weighted images and isointense relative to normal marrow on T2-weighted images. The intensity patterns of the normal clivus on T1- and T2-weighted MR images change predictably with advancing age. Intensity patterns of abnormal clivi differ from those of normal clivi. When contrast material is used, normal and abnormal clivi generally show different patterns of enhancement.     

Sagittal MR imaging of the chest: normal and abnormal

To determine the value of sagittal magnetic resonance (MR) in diagnosing thoracic abnormality, we reviewed the multisection sagittal spin-echo MR images of 13 normal subjects and 23 patients with a variety of thoracic abnormalities. In the abnormal subjects sagittal images were compared with transaxial MR performed with repetition time values of both 0.5 and 2.0 s. Sagittal images were most helpful in the evaluation of structures lying in the sagittal plane such as the thoracic aorta. Mediastinal masses in most locations were better seen and evaluated in the transaxial plane. However, the relationship of subcarinal masses to the trachea, left atrium, and pulmonary artery was better appreciated in the sagittal plane. The relationship of hilar masses to hilar vessels, bronchi, and the mediastinum was usually better seen on transaxial images. Also, the relationship of paramediastinal masses to the mediastinum was difficult to evaluate with sagittal scans.     

MR灌注成像在正常肾和肾脏疾病中的应用价值

目的 探讨正常肾脏及常见肾脏疾病MR灌注加权成像(PWI)的主要表现特征和临床应用价值.方法 搜集共31例患者行MR PWI,其中9例非泌尿系统疾病患者作为正常肾对照组,肾癌14例,肾囊肿6例,肾结核2例.31例均行冠状面常规T1WI、T2WI与PWI.原始图像经工作站处理后获得灌注曲线及各功能图像,比较正常肾脏及病变部位的时间-信号强度曲线、血容量(RBV)、血流量(RBF)、平均通过时间(MTT)、达峰值时间(TTP)及相应灌注功能图像.正常肾脏灌注参数(RBV、RBF、MTT和TTP)的相对值通过左肾/右肾获得,异常肾脏灌注参数通过病变组织/对侧同一部位肾组织获得.观察两组肾脏的血流灌注参数变化,并结合灌注图像对其病变组织的血流变化进行分析.对正常对照组左、右肾和正常肾皮、髓质各灌注参数的比较采用t检验;对异常肾与正常肾各灌注参数的比较行q检验.结果 正常肾脏皮质的相对RBV(1.33±0.08)和RBF(1.44 ±0.09)均明显大于髓质相对RBV(0.58 ±0.05)和相对RBF(0.78 ±0.13),差异均有统计学意义(t值分别为9.2241和5.0336,P值均＜0.01);肾脏皮质相对MTT(1.11±0.08)和相对TTP(1.04 ±0.06)与髓质相对MTT(0.97±0.04)和相对TTP(0.94±0.03)差异无统计学意义(t值分别为2.2551和2.2613,P值均＞0.05).肾癌相对RBF(1.35±0.34)明显高于正常肾脏组织相对RBF(1.02±0.06)(q=3.0882,P＜0.01).结论 PWI可以测量正常肾组织与病理情况的血液动力学变化,在肾功状态变化和疾病的鉴别诊断方面具有较高的应用价值.     

健康成人枕骨斜坡骨髓3．0T磁共振多b值扩散加权成像的可行性研究

目的：探讨健康成人枕骨斜坡骨髓3．0T磁共振多b值扩散加权成像（DWI）的可行性。方法采用Philips 3．0T TX Achieva磁共振成像仪、16通道头颈神经血管线圈,对61名健康志愿者行多b值DWI扫描。利用随机工作站的diffusion软件包对原始数据进行后处理,获取表观扩散系数（ADC）图,由1名工作未满2年的低年资、1名工作满10年的高年资影像医生,先对图像进行质量分级,对入选的58例进行双盲测量枕骨斜坡骨髓的ADC值及其面积,1个月后,高年资医生进行第2次测量,将所得数据进行统计学分析。结果 ADC图的图像质量分级：Ⅰ级42例、Ⅱ级16例、Ⅲ级3例,优良率约95%（58/61）。不同年资者之间、高年资者2次测量枕骨斜坡骨髓ADC值的差异均无统计学意义（P＞0．05）,而测量面积的差异均有统计学意义（P＜0．05）。结论健康成人枕骨斜坡骨髓3．0T磁共振多b值DWI图像质量良好,ADC值测量在观察者间、观察者内具有很高的一致性和可行性。     

Diffusion-weighted MR imaging findings in an isolated abscess of the clivus

We report the finding of restricted diffusion in an isolated abscess of the clivus and discuss the imaging differential diagnosis, with an emphasis on the usefulness of diffusion-weighted imaging.     

Cartilaginous epiphysis and growth plate: normal and abnormal MR imaging findings.

The cartilaginous structures at the ends of growing bones constitute the "growth mechanism." These structures are not visible on radiographs, but they can be seen with MR imaging. Improved definition of cartilaginous abnormalities by MR imaging may permit earlier detection and treatment of these disorders and thus prevent bone deformity. This pictorial essay contains examples of normal and abnormal growth cartilage as seen with MR imaging. The indications for MR imaging in the evaluation of certain growth disorders are discussed, and the usefulness of MR imaging in certain clinical situations in which the role of this technique is still evolving is illustrated.     

Cortical maturation in normal and abnormal fetuses as assessed with prenatal MR imaging

PURPOSE: To establish the appearance of normal fetal cortical development in utero and compare it with the appearance of abnormal cortical development. MATERIALS AND METHODS: Magnetic resonance (MR) images of the brain in 53 normal and 40 abnormal fetuses at 14-38 weeks gestational age (GA) were reviewed. The GAs at the time of MR imaging visualization of the fissures or sulci were compared with the GA guidelines based on neuroanatomic studies. RESULTS: In normal fetuses, the sulcation landmarks appeared on MR images in the order predicted by using anatomic studies, with a 0-8-week lag in the MR imaging visualization of the sulci compared with the reported time of visualization of the sulci in anatomic specimens. When landmarks were grouped by range of GAs, the expected MR imaging sulcation landmarks in the group with younger GAs than the actual GA were seen in 50 of 53 (94%) normal fetuses, in five of nine fetuses (56%, P < .05) with isolated mild ventriculomegaly, and in 24 of 31 fetuses (77%, P < .05) with other CNS anomalies. CONCLUSION: Normal fetal cortical maturation at MR imaging follows a predictable course that is slightly delayed compared with that described in neuroanatomic specimens. This maturation is often further delayed in fetuses with CNS abnormalities.     

MR appearance of normal and abnormal bile: Correlation with imaging and endoscopic finding

Identification of abnormal bile related to various pathological processes in the pancreaticobiliary tract can be important in the diagnosis of disease and the determination of appropriate treatment. Magnetic resonance (MR) imaging can allow comprehensive evaluation of abnormal bile because MR usually provides better tissue characterization than other imaging modalities. A high-intensity signal from bile is frequently encountered on T1-weighted images and can be seen in concentrated bile, sludge, stones, or hemobilia. Contrast-enhanced MR features, such as inhomogeneous hepatic enhancement in the arterial phase and papillitis or mild-to-moderate bile duct wall thickening with enhancement, along with clinical characteristics, may suggest clinically significant bile, such as sludge or purulent bile, rather than merely concentrated bile. A history of trauma and appropriate imaging findings in the hepatobiliary tract can support a diagnosis of hemobilia. MR imaging may assist in diagnosing intraductal papillary mucinous neoplasm of the bile duct via detection of an intraductal mass or several indirect signs, suggesting a large amount of mucin. Additionally, Gd-EOB-DTPA-enhanced MR may delineate mucin as a filling defect surrounding hyperintense bile. A floating filling defect on all MR sequences is helpful in discriminating pneumobilia from other intraluminal filling defects. Familiarity with the various different MR features of abnormal bile signals can therefore facilitate accurate diagnosis and treatment.     

MR of the normal and abnormal internal auditory canal

MR performed with thin, contiguous sections has replaced CT for the study of the cerebellopontine angle and for diagnosis of acoustic neuromas. In our experience large acoustic neuromas are well seen in all pulse sequences. Tumors with small extracanalicular components are seen in the T1- and spin-density-weighted sequences whereas purely intracanalicular lesions are often visualized only in the T1-weighted images. Small acoustic neuromas producing thickening of the nerve are easily recognizable in narrow internal auditory canals but may be missed in large canals because of partial volume averaging. Since further enhancement of the signal intensity of tumors can be obtained by IV injection of paramagnetic agents, we foresee the use of such agents in the near future in the diagnosis of acoustic neuromas.     

MR imaging of the normal shoulder

Magnetic resonance (MR) images of the shoulders of a healthy volunteer were obtained in axial, sagittal, and coronal orientations using a 0.5-T imaging system. Multiple high-resolution spin-echo images were generated using an off-center zoom technique and a specially designed surface coil. Several anatomic structures, including the rotator cuff, long biceps tendon, articular capsule, muscles, and bones, were visualized. The coronal and sagittal views were the most useful for demonstrating the rotator cuff. MR imaging has potential as a new non-invasive tool for the evaluation of the shoulder region.     

MR imaging of the normal larynx

Magnetic resonance imaging of the larynx was performed on 15 volunteers. Searching for optimal images in the sagittal, frontal, and transverse planes, we compared images made with a special surface coil and the standard head coil, images with different slice thicknesses, images with different repetition times (TR) and images with different matrices. The field of view and the scan times were kept as small as possible. Using a surface coil, we obtained high resolution images in all three planes. These images provide clinically relevant information, not shown by current radiological techniques: hyoepiglottic ligament, thyrohyoid ligament, thyroepiglottic ligament and cricothyroid ligament, the borders between the preepiglottic space and both paraglottic spaces (PGS), the borders between both PGS and thyroid cartilage, and the vocalis and thyroarytenoid muscles. Short TR is preferred because, with shorter scan time, more measurements could be made. Images with a 128 X 128 matrix size had a much better signal-to-noise ratio than images with a 256 X 256 matrix size. Magnetic resonance has great potential in imaging normal and pathological anatomy of the larynx.     

MR imaging of the normal knee

The knees of 11 volunteers were examined by magnetic resonance (MR) imaging. The imaging was done with a 0.15 T resistive magnet using spin-echo pulse sequences. Normal anatomy was well displayed. The visualized structures included the menisci, cruciate ligaments, articular cartilage, cortical and cancellous bone, muscles, tendons, subcutaneous and intraarticular fat, and blood vessels. To obtain optimal visualization of the anterior cruciate ligaments, various positionings of the subjects and angulation of the imaging planes were tried. Rotation of the sagittal scanning plane away from the longitudinal axis of the body was found to be most satisfactory. The results obtained so far are very promising and demonstrate the real potential of MR imaging in the knee, which we believe lies in its ability to visualize the menisci and cruciate ligaments without use of contrast agents.     

MR imaging of the tarsal tunnel and related spaces: normal and abnormal findings with anatomic correlation

The tarsal tunnel syndrome may be caused by extrinsic or intrinsic pressure on the posterior tibial nerve or its terminal branches. The specific symptoms depend on the extent of nerve involvement, and compression distal or proximal to the tarsal tunnel may result in variants of the syndrome. To define better the capability of MR imaging for evaluating this entity, we performed MR imaging on three normal subjects and correlated the images with cryomicrotome sections. Six patients with symptoms suggestive of tarsal tunnel syndrome also were studied with MR. In all normal subjects, MR images showed the flexor retinaculum and the structures passing deep to the retinaculum: the tibialis posterior tendon, flexor digitorum longus tendon, flexor hallucis longus tendon, and the posterior tibial neurovascular bundle. The medial calcaneal sensory branch(es) and the medial and lateral plantar nerves also were delineated. Mechanical causes of compression were shown in all six symptomatic patients. The pathologic entities included two neurilemomas, tenosynovitis involving all three tendons, a ganglion cyst arising from the flexor hallucis longus tendon sheath, posttraumatic fibrosis, and post-traumatic fibrosis with associated posttraumatic neuroma. The MR findings were confirmed surgically in five cases. MR imaging can accurately depict the contents of the tarsal tunnel and the courses of the terminal branches of the posterior tibial nerve. In our small series, MR imaging accurately showed the lesions responsible for tarsal tunnel syndrome.     

正常和异常舌组织的DCE-MRI评价

目的:评价正常舌组织和其他颌面颈部组织的动态增强MRI(DCE-MRI)表现,比较正常和异常舌组织的TIC曲线类型和最大斜率值之间的差异.方法:对15例健康成人和65例经手术病理证实的舌肿块性病变患者(良性19例,恶性46例)行DCE-MRI检查.分别获取正常颌面颈部肌肉和腮腺组织的TIC曲线类型和最大斜率值,以及舌病...     

臂丛神经MRI正常表现

目的：分析臂丛神经在MRI不同成像序列中的正常表现。方法：20名正常志愿者行常规及MR新技术检查。观察各序列中臂丛神经的表现。结果：常规T1WI、T2WI臂丛神经呈等信号,STIR上呈高信号。横断面上,显示神经根自椎间孔处穿出,行于斜角肌间隙,后与锁骨下动脉及腋动脉伴行;冠状面上,显示为由C5～T1神经孔旁起始的条索状结构;矢状面上表现为结节状结构,行于斜角肌间隙,围绕锁骨下动脉。3D-FIESTA-c序列显示椎管内神经前后根为脑脊液高信号环绕下的等信号丝状结构。薄层无间隔STIR图像上背景组织信号抑制,椎管外臂丛神经显示为条状高信号结构,3D—FSPGR图像显示神经为条状等信号,同时反应其与邻近组织结构的关系。结论：联合常规及MRI新技术,可全面、清晰地显示臂丛神经。     

MR imaging of the normal appendix and acute appendicitis

PURPOSE: To describe the MR appearance of the normal appendix and the MR imaging characteristics of acute appendicitis with correlation to pathological severity. MATERIALS AND METHODS: A total of 20 volunteers participated in this study to demonstrate normal appendices by MR imaging. A total of 37 consecutive patients with clinically diagnosed acute appendicitis were also scanned. T1-weighted (T1WI) spin-echo images, T2-weighted (T2WI) fast spin-echo, and fat-suppressed spectral presaturation inversion recovery T2-weighted (T2SPIR) fast spin-echo images were obtained. The MR criteria for considering acute appendicitis were as follows: 1) thickening of the appendiceal wall with high intensity on T2WI or T2SPIR; 2) dilated lumen filled with high intensity material on T2WI or T2SPIR; and 3) increased intensity of periappendiceal tissue on T2WI or T2SPIR. RESULTS: The visibility of a normal appendix on MR imaging was 90% (18/20). It appeared as a cord-like structure of medium intensity without fluid collection in the lumen. A total of 30 cases with clinically diagnosed acute appendicitis had positive MR findings and all except one were pathologically proven. The one had cecal diverticulitis. These cases demonstrated filled lumen, with a hypointense wall on T1WI and slightly hyperintense on T2WI or T2SPIR. MR findings correlated well with pathological severity, especially a thicker wall, periappendiceal high intensity, and ascites were useful for suspecting severe appendicitis. CONCLUSION: Correct diagnosis of acute appendicitis was obtained with MRI, and correlated well with its pathological severity. MRI is a powerful alternative for diagnosing acute appendicitis especially for the patients in whom the radiation is major concern.     

Normal and abnormal thymus in childhood: MR imaging

Magnetic resonance (MR) imaging studies of 47 children without thymic disease were compared with those of 14 children with proved thymic abnormalities (eg, lymphoma, leukemia, hyperplasia) to evaluate the spectrum of MR features of the normal and abnormal thymus and to determine the best indicators of thymic disease. In healthy children younger than 5 years of age, the thymus had a quadrilateral shape and biconvex lateral contours. Older children and adolescents had a triangular thymus with straight lateral margins. The thymus appeared homogeneous with a signal intensity slightly greater than that of muscle on T1-weighted images and close to that of fat on T2-weighted images. Qualitative evaluation of gross thymic morphology (size, shape, margins, and signal intensity) usually was sufficient for distinguishing between the normal and abnormal thymus. The abnormal thymus generally was enlarged, multilobular, or inhomogeneous because of the presence of cystic degeneration, hemorrhage, septations, fibrosis, or calcification on pathologic sections. In patients with lymphoma, the presence of associated lymphadenopathy also was helpful in distinguishing the normal from the abnormal thymus.     

Color Doppler flow imaging of the normal and abnormal orbit

Twenty-six normal orbits (16 subjects) and seven patients with suspected orbital disease were studied with color Doppler flow imaging CDFI). Arterial structures consistently identified included the ophthalmic artery, central retinal artery, and posterior ciliary branches. The terminal lacrimal branch was seen in the majority of orbits (n = 19). Venous structures consistently seen included the central retinal vein and venae vorticosae; the superior ophthalmic vein was identified in the majority of normal orbits (n = 22). Response of the superior ophthalmic vein to the Valsalva maneuver was assessed in six of the normal subjects (12 orbits). Retrograde flow was typically seen during the maneuver and accentuated antegrade flow after cessation of the maneuver. Pathologic entities correctly diagnosed with CDFI included a dural arteriovenous malformation (AVM) with spontaneous carotid-cavernous fistula, an orbital AVM, and superior ophthalmic vein thrombosis. Vascular lesions were excluded in two patients with orbital masses. Bilaterally enlarged superior ophthalmic veins were identified in a patient with unilateral symptoms suggestive of a varix; CDFI results were confirmed with computed tomography, but orbital venograms were interpreted as normal. These findings suggest that CDFI may be helpful in the evaluation of suspected vascular orbital disease.     

Magnetic resonance imaging of the normal and abnormal pulmonary hila

Magnetic resonance (MR) images of the hila were reviewed in 25 normal subjects and 12 patients with unilateral or bilateral hilar masses. On spin echo MR images in normal patients, collections of soft tissue large enough to be confused with an abnormally enlarged lymph node were seen in three locations. In patients with a hilar mass, the mass was differentiated from hilar vasculature more easily using MR than contrast-enhanced CT. In five of these patients, hilar lymph nodes approximately 1 cm in diameter were easily seen using MR, but were difficult or impossible to appreciate prospectively on CT. However, because the spatial resolution of MR is inferior to that of CT, bronchi were difficult to evaluate using MR. In general, images obtained with a short TR (0.5 sec) provided the best definition of mediastinal extension of the hilar mass, and images with a longer TR (1.5 to 2.0 sec) provided a better signal-to-noise ratio and showed increased signal strength from hilar masses. Electrocardiographic-gated images showed better resolution of hilar structures but may not be necessary for large masses.     

MR imaging of the scrotum: normal anatomy

High-resolution magnetic resonance (MR) imaging with a surface coil was utilized to evaluate the normal scrotum. Scrotal contents, spermatic canal, and inguinal regions were visualized within the same field of view. Differences in signal intensity in the testis, epididymis, tunica albuginea, fluid, fat, and spermatic cord allowed for clear delineation of these structures in detail. The high contrast and spatial resolution of MR imaging, coupled with the wide field of view and absence of ionizing radiation, make MR imaging well suited for evaluation of the scrotum.