The MR appearance of gray and white matter in the cervical spinal cord

Artifacts that can distort the appearance of the cervical spinal cord are caused by data truncation during MR image reconstruction. We used a phantom and then correlated anatomic sections with MR images in cadavers and normal volunteers to evaluate the effect of truncation artifacts on the MR appearance of the spinal cord. When truncation artifacts are minimized, the gray matter and major white-matter columns in the cervical cord can be recognized. T2-weighted gradient-echo MR techniques can best differentiate gray from white matter.     

MR imaging of the tendons of the foot and ankle

Hindfoot pain from tendon pathology is common and seen in a wide range of patients from young athletes to older sedentary individuals. Magnetic resonance (MR) is an excellent technique for imaging tendons and for identifying injuries that can be treated with surgery. MR also demonstrates the presence of bone marrow edema, which is a cause of pain and often a marker for adjacent tendon injury. Finally, MR can reveal other etiologies that cause similar hindfoot pain, such as osteochondral injuries and impingement. In this article, we review the normal MR appearance of the ankle tendons and tendon sheath fluid. MR protocols for imaging the various ankle tendon groups are presented. We discuss the MR appearance of tendon pathology, including tendonosis/ tendinopathy, tenosynovitis and peritendonosis, partial and complete tears, subluxation and dislocation, and entrapment. The Achilles, medial, lateral, and anterior tendon groups are discussed separately so as to focus on the MR appearance specific to each region of the ankle.     

The knee after partial meniscectomy: MR imaging features

The magnetic resonance (MR) examinations of 51 menisci treated by means of partial meniscectomy were reviewed. Menisci were divided into three groups: group 1, near normal length without osteoarthritis; 2, substantially shortened without osteoarthritis; and 3, any length with osteoarthritis. Group 1 menisci resembled normal menisci except for mild shortening and frequent signal inhomogeneity (56%). Group 2 menisci varied in appearance, with marked contour irregularity simulating fragmentation in 40% of segments despite a normal postoperative appearance at follow-up arthroscopy. Group 3 menisci appeared similar to menisci of the same length without osteoarthritis. Arthroscopic correlation, available for 23 menisci (45%), confirmed the MR diagnosis of a tear in 11 and no tear in 49 and revealed an unsuspected tear in three meniscal segments. There is a spectrum of normal MR appearances after partial meniscectomy. Standard MR criteria can be used to diagnose tears in the absence of marked contour irregularity; however, the diagnosis of tears of segments with marked contour irregularity must be made cautiously, since this irregularity can mimic a tear and was not predictive of an arthroscopically visible tear.     

跗骨窦区断层解剖与影像学表现对照

目的研究跗骨窦结构及颈韧带在断层解剖与CT、MRI表现,并进行对照,为影像学诊断提供解剖学依据。方法解剖1例尸体跗骨窦标本,颈韧带表面涂抹对比剂后CT扫描,图像后处理观察颈韧带;对17例标本行MRI扫描,40例正常人行CT容积扫描与MRI扫描,并将标本制作成不同典型断层标本,分别通过测量观察跗骨窦特征及颈韧带走行特征。辨认跗骨窦内部结构及周围结构,对测量结果进行统计学分析。结果跗骨窦及颈韧带径线测量在断层解剖上与MRI对比、MRI与CT图像对比无显著性差异。跗骨窦内部结构及周围结构在CT、MRI均可清晰显示。结论 MRI图像与断层解剖标本测量结果基本一致,能够清晰显示跗骨窦局部结构,跗骨窦软组织的CT容积扫描多平面重组图像与MRI图像无明显差异。     

Dural arteriovenous fistulas: evaluation with MR imaging

The preangiographic diagnosis of cerebral dural arteriovenous fistula (DAVF) can be difficult. The magnetic resonance (MR) images of 12 patients with angiographically proved DAVF were evaluated to characterize the appearance of these lesions and to identify those patients at increased risk for complications. Patients with DAVF demonstrating venous occlusive disease are at higher risk for complications from the arterialized collateral venous system. This venous occlusive disease is demonstrated best at arteriography. The MR imaging appearance of dilated cortical veins without a parenchymal nidus is suggestive of a DAVF with veno-occlusive disease. Eight of the 12 patients in our series demonstrated this finding at angiography. Complications, including infarction and hemorrhage, were identified at MR imaging in eight patients with MR imaging evidence of veno-occlusive disease. At angiography 42% of these complications were not apparent. In one patient with a DAVF draining into an unobstructed right sigmoid sinus, results of MR study were normal. Although patients with DAVF without veno-occlusive disease may have normal findings at MR imaging, DAVF associated with veno-occlusive disease and dilated pial venous drainage can be documented on MR images. This subset of DAVF patients, many of whom were identified only at MR imaging, is at higher risk for complications due to veno-occlusive disease. These patients are believed to require more urgent therapy. MR imaging is useful in the pretherapeutic planning for patients with DAVF.     

Normal myelination of the pediatric brain imaged with fluid-attenuated inversion-recovery (FLAIR) MR imaging.

BACKGROUND AND PURPOSE: As in adult imaging, FLAIR can be applied to pediatric brain imaging, and this requires an appreciation of the normal pediatric brain appearance by FLAIR imaging. The purpose of this study was to describe the MR appearance of the brain in normal infants and young children as demonstrated by fluid-attenuated inversion-recovery (FLAIR) MR imaging. METHODS: We retrospectively examined MR brain studies, interpreted as normal by pediatric radiologists, from 29 patients (aged 1 to 42 months) to catalog the appearance of myelination in multiple brain areas. RESULTS: On T2-weighted images, white matter progressed from hyperintense to hypointense relative to adjacent gray matter over the first 2 years of life. An analogous, although slightly delayed sequence was observed on FLAIR images with the exception of the deep cerebral hemispheric white matter, which followed a triphasic sequence of development. On FLAIR images, the deep cerebral white matter was heterogeneously hypointense relative to gray matter in the young infant, became hyperintense early in the first few months of life, and then reverted to hypointense during the second year of life. CONCLUSION: The normal appearance and development of brain white matter must be taken into account when interpreting FLAIR images of infants and young children.     

Pancreatic transplantation using portal venous and enteric drainage: the postoperative appearance of a new surgical procedure

PURPOSE: To review the normal radiologic appearance of pancreatic transplants that use portal venous and enteric drainage, and to review the appearance of a variety of postoperative complications. METHOD: We retrospectively reviewed the computed tomographic (CT) scans, magnetic resonance (MR) images, and ultrasounds of patients who had undergone pancreatic transplantation using portal venous and enteric drainage. RESULTS: At CT, the normal pancreatic transplant appears as a heterogeneous mass composed of pancreatic parenchyma, vessels, and omental wrap. On MR imaging, a normal transplant demonstrates intermediate signal intensity on T1- and T2-weighted sequences. Sonographic evaluation of a normal transplant reveals a hypoechoic gland that contains readily detectable low-resistance arterial and venous Doppler waveforms. Acute postoperative complications include acute rejection, which has a nonspecific radiologic appearance, and transplant pancreatitis, which is often manifested on CT by stranding of the peritransplant fat. Chronic postoperative complications include small bowel obstructions, graft pancreatitis secondary to obstruction of the Roux loop, and chronic rejection. CONCLUSION: Knowledge of the radiologic appearance of the normal pancreatic transplant is required before transplant-related complications can be detected.     

Extrafetal findings at fetal MR: evaluation of the normal placenta and correlation with ultrasound

Despite the increasing use of magnetic resonance (MR) for fetal imaging, few studies have addressed the MR appearance of the normal placenta. The goal of this paper is to describe the MR features and thickness of the normal placenta during the second and early third trimester of gestation, based on a retrospective study comparing MR with the reference standard of obstetric imaging, ultrasound.     

膝关节内侧副韧带薄层断面与MRI解剖及其诊断价值

目的研究膝关节内侧副韧带薄层断面表现及其正常和损伤的MRI表现。方法分析内侧副韧带薄层断面标本解剖特点,对120例正常膝关节内侧副韧带及25例损伤病例MRI表现进行回顾性分析。结果薄层断面清晰显示膝关节内侧副韧带解剖特点,MRI与薄层断面具有很好对应性。MRI能够对内侧副韧带损伤进行准确分级。结论薄层断面与MRI能够清晰显示内侧副韧带的解剖学特点。横轴位MRI分级评价对内侧副韧带损伤的诊断和治疗具有重要价值。     

Magnetic resonance imaging of the cavernous sinus

The magnetic resonance (MR) appearance of the cavernous sinus was studied by correlating the MR images of normal volunteers and cryomicrotomic sections from six cadavers. In addition, MR images of patients with parasellar masses were compared with corresponding intravenously enhanced computed tomographic (CT) scans. The MR appearance of the cranial nerves in the cavernous sinuses is demonstrated, as well as MR signs of a parasellar mass, including obliteration of intracavernous venous spaces, displacement of the intracavernous internal carotid artery, and bulging of the lateral wall of the cavernous sinus. MR proved to be more effective than CT in delineating the parts of the cavernous sinus.     

MR imaging of the normal shoulder: anatomic correlation

The complex anatomy and the requirement to image in the peripheral magnetic field have made the shoulder difficult to examine with MR. However, the use of high-resolution scanning techniques and specialized surface coils has improved the quality of MR images obtained. Seventy-five scans of the shoulders of normal volunteers were correlated with multiplanar cryomicrosections of six cadaver shoulders to study the MR appearance of normal structures. MR was shown to provide excellent depiction of shoulder anatomy.     

MRI of medial malleolar bursa

OBJECTIVE: This study was designed to assess the MR appearance of the medial perimalleolar fat in an asymptomatic population and describe the MRI appearance of the medial malleolar bursa. CONCLUSION: The MRI findings of medial perimalleolar fat in asymptomatic individuals and in patients with suspected medial malleolar bursa include normal fat, minimal or extensive subcutaneous edema, and a fluid-filled sac. The latter pattern is consistent with the MR appearance of the medial malleolar bursa.     

MR imaging of anterior cruciate ligament repair

Magnetic resonance (MR) imaging is an accurate means of analyzing disruptions of the native anterior cruciate ligament (ACL). Various techniques may be used to repair a disrupted ACL. A common repair is the MacIntosh lateral-substitution over-the-top repair in which a strip of fascia lata from the iliotibial band is used as a "neoligament." The results of 27 MR examinations of 17 athletes with this repair were analyzed to determine the appearance of the neoligament on MR. Thirteen of the 17 patients had returned to full athletic activity and four were capable of strenuous activity. Examinations were made at both 0.5 and 1.5 T in varied extents of external rotation from 0 to 20 degrees, and at variable time intervals after surgery from 1 to nearly 40 months. Only two patients clinically required postrepair arthroscopy, but both had normal repairs. Neoligaments were classified as well-defined (n = 6 studies), ill-defined (n = 10), and not discernible (n = 11), based on clarity of appearance. Reasons for this variable appearance include the variable presence of fibrous and fatty tissue investing the neoligament. We conclude that the normal neoligament, unlike the normal active ACL, has a variable appearance, including nonvisualization on MR and that criteria used in evaluating the native ligament will be inadequate to assess the repair.     

How I diagnose meniscal tears on knee MRI

OBJECTIVE: The goal of this article is to summarize the literature about the diagnosis of meniscal tears on MRI including the normal appearance of the meniscus and the appearance of the various types of meniscal tears. In addition, I discuss my experience with the causes of errors in the MR diagnosis of meniscal abnormalities and the nuances of meniscal abnormalities that can mimic a meniscal tear. CONCLUSION: MRI is a highly accurate imaging method for diagnosing meniscal tears. To avoid errors in diagnosing meniscal tears, those interpreting MR examinations of the knee need to be aware of the attachments of the menisci and the normal variations in meniscal anatomy that may resemble a meniscal tear. In addition, by being aware of the patterns of meniscal tears, it is easier to diagnose the less common tears.     

Normal bone marrow: dynamic aspects in magnetic resonance imaging]

The bone marrow is a complex organ that contains fat and nonfat cells, the proportion of which varies greatly with age and in the different bones of the skeleton. Magnetic resonance imaging provides information on the composition of the medullary cavity of any given bone and on the distribution of red and yellow marrow in the skeleton. The wide spectrum of appearances of the normal bone marrow at MR imaging will be reviewed. The purpose of this paper is to determine the MR appearance of the bone marrow, to illustrate the phenomenon of marrow conversion and to familiarize the readers with the complex parameters that interfere with the MR appearance of normal bone marrow.     

Extrinsic carpal ligaments: normal MR arthrographic appearance in cadavers

PURPOSE: To describe the normal magnetic resonance (MR) arthrographic anatomy of the major carpal ligaments (excluding scapholunate and lunotriquetral ligaments) and their osseous attachments by using standard imaging planes. MATERIALS AND METHODS: MR images of 22 wrists derived from fresh human cadaveric hands were obtained after tricompartmental arthrography. The MR arthrographic appearance of the carpal ligaments and their bone attachments were analyzed and correlated to those seen on anatomic sections. Two readers determined in consensus which was the best plane to observe the course and attachment sites for each ligament. They further analyzed the size and sites of attachment of these ligaments in two orthogonal planes chosen for optimal viewing. RESULTS: Each ligament was well seen as a hypointense linear structure with MR arthrography. The radioscaphocapitate, radiolunotriquetral, radioscapholunate, dorsal radiotriquetral, palmar scaphotriquetral, and dorsal scaphotriquetral ligaments were best evaluated in the transverse plane. The palmar and dorsal ulnotriquetral and ulnolunate ligaments were best visualized in the sagittal plane. The radial collateral ligament was best analyzed in the coronal plane. The attachment sites of all ligaments were best analyzed either in the transverse or sagittal planes. CONCLUSION: MR arthrography allows visualization of the carpal ligaments. Detailed knowledge of the normal appearance of these ligaments can serve as a baseline for future studies in which MR arthrography is used to characterize wrist instability.     

MR imaging of the trigeminal ganglion,nerve, and the perineural vascular plexus: normal appearance and variants with correlation to cadaver specimens

BACKGROUND AND PURPOSE: MR imaging is the method of choice for evaluating the trigeminal nerve. Detection of abnormalities such as perineural tumor spread requires detailed knowledge of the normal MR appearance of the trigeminal nerve and surrounding structures. The purpose of this study was to clarify the normal MR appearance and variations of the trigeminal ganglion, maxillary nerve (V2), and mandibular nerve (V3) with their corresponding perineural vascular plexus. METHOD:S: MR images obtained in 32 patients without symptoms referable to the trigeminal nerve were retrospectively reviewed. The trigeminal ganglion in Meckel's cave, V2 within the foramen rotundum, and V3 at the level of foramen ovale were assessed for visualization and enhancement. The configuration of the perineural vascular plexus was recorded. Correlation to cadaver specimens was made. RESULTS: The trigeminal ganglion and V3 were observed to enhance in 3-4% of patients unilaterally. V2 and V3 were well visualized 93% of the time. The perineural vascular plexus of V2 was observed 91% of the time, and that of V3 in 97% of instances. CONCLUSION: This study characterizes the normal MR appearance of the trigeminal ganglion and its proximal branches. The trigeminal ganglion, V2, and, V3 are almost always reliably seen on thin-section MR studies of the skull base. Enhancement of the perivascular plexus is routinely seen; however, enhancement of the trigeminal ganglion, V2, or V3 alone is seen only on occasion as supported by the avascular appearance of these anatomic structures in cadaver specimens.     

Magnetic resonance imaging of the female pelvis

Magnetic resonance (MR) imaging is particularly well suited for the evaluation of the female pelvis because of the lack of respiratory motion and the multiplanar imaging ability of MR. The MR appearance of normal anatomy is dependent on the pulse sequence used. This is also true for pelvic pathology. Primary cervical carcinoma is best seen on T2-weighted images; parametrial extension and lymph node metastases are best evaluated on T1-weighted images. Endometrial carcinoma is also best seen on T2-weighted images. Absence of the junctional low intensity band of the uterus may indicate myometrial invasion by endometrial tumor, although more data are needed to make a final diagnosis. Uterine leiomyomata have a variable MR appearance which may be related to the degree of cellularity of the tumor. Our experience in the MR appearance of adnexal masses is limited. MR imaging should assume a more important role in imaging the female pelvis in the future.     

MR imaging of the corpus callosum: normal and pathologic findings and correlation with CT

The MR appearance of the corpus callosum was investigated in 80 normal volunteers. Normal variations in appearance were recorded with regard to age, gender, and handedness. The MR studies of 47 patients with a wide spectrum of callosal disease were also reviewed. Abnormalities included trauma, neoplasia, congenital abnormalities, vascular lesions, and demyelinating and inflammatory conditions. The information provided by MR was compared with that obtained from other radiographic examinations, particularly CT and angiography. In all cases MR provided as much, and frequently more, information than was obtained by other imaging techniques. We believe that MR should be the primary imaging technique for the evaluation of corpus callosal disease.