Magnetic resonance imaging of intracranial epidermoid tumours

Epidermoid tumours are rare lesions within the skull which are usually found in a cerebellopontine angle. In the computed tomography (CT) literature, they have been described as well-defined lesions of low density which seldom show calcification or tissue enhancement. We have recently encountered three intracranial epidermoids, which appeared to exhibit uniform findings on low field strength magnetic resonance (MR) of moderate signal intensity in the T1-weighted images and a bright signal (increased T2) in the T2-weighted sequences. It may be possible to predict accurately the presence of an epidermoid tumour when this particular configuration of findings is present.     

Magnetic resonance imaging of ganglion cell tumours

Summary The MRI and CT studies of four patients with ganglion cell tumours, one with a cerebellar gangliocytoma (Lhermitte-Duclos disease), and three with gangliogliomas are reported. MRI in Lhermitte-Duclos disease clearly demonstrated a mass of low signal intensity in the left cerebellum on T1-weighted spin-echo (SE) images and an area of high signal intensity with a blurred margin on T2-weighted SE images. These MRI studies were useful for delineating the lesion, which was verified at surgery. In the ganglioglioma, MRI demonstrated two isointense solid masses on T1-weighted SE images, which enhanced clearly with Gd-DTPA. The enhancement study was advantageous in planning surgery.This study was presented in part at the 14th Annual Meeting of The Japan Society for CNS Computed Tomography, January 25, 1991     

Magnetic resonance imaging of the cerebello-pontine angle

A variety of extra-axial lesions occurring at the cerebello-pontine angle was examined by magnetic resonance imaging (MRI). Differences in spin sequence characteristics were found between neurilemmomas and meningiomas, with neurilemmomas exhibiting a greater increase in T2 than meningiomas. The T1 images were of less value in differentiating between neurilemmomas and meningiomas but were of value in the diagnosis of vascular lesions, due to the decreased T1 of blood clot. The T1 images were also of value in the assessment of tumour size and in the diagnosis of an epidermoid cyst. Extension of tumour into the internal auditory meatus was seen on MRI with acoustic neuromas and with one other lesion. The transverse perspective was of greatest value in lesion assessment. The coronal perspective was useful in certain situations but the sagittal perspective was of minimal clinical value.     

Computer tomography in the diagnosis of cerebellopontine angle tumours

Summary 53 patients clinically suspected of having a cerebellopontine angle (CPA) lesion were examined by computer tomography (CT) with 160 x 160 matrix EMI scanner. 17 cases (32%) had tumour positive CT, of which 12 were neurinomas and 1 meningioma. 1 CT suggestive of a CPA lesion was false positive and 1 unoperated case is probably a false negative CT. Three of the eleven verified neurinomas (27%) were of the medial type originating in the angle cistern. One neurinoma protruding 1 cm into the cistern showed no contrast enhancement. 2 CT scans (3.8%) were unsatisfactory due to movements and the large size of the head. CT is valuable for the investigation of CPA pathology and the diagnostic efficiency compares favourably to other neuroradiological procedures.     

桥小脑角区髓母细胞瘤的 MRI 表现

目的：分析桥小脑角区(CPA)髓母细胞瘤的 MRI 特点,提高该病的诊断率。方法回顾性分析5例经手术病理证实的发生于 CPA 髓母细胞瘤的 MRI 表现特点及病理特征。结果5例髓母细胞瘤中4例见囊变,且均位于肿瘤的边缘,1例为完全实性肿块。肿瘤实性部分 T1 WI 呈低、稍低信号,T2 WI 呈稍高或高信号为主混杂信号。2例行 DWI 扫描呈高信号。增强后强化程度多样。5例肿瘤均引起桥脑及四脑室受压,2例邻近基底脑膜强化,2例出现瘤周水肿。结论MRI 可显示 CPA 髓母细胞瘤肿瘤的范围、继发改变及与周围组织的关系。     

Magnetic resonance imaging evaluation of perianal fistula

Aim of work

To clarify the role of MRI in diagnosis and classification of perianal fistula and to evaluate the additional clinical value of preoperative MR imaging and its benefit to surgeon.

Methods

This prospective study contained 25 patients (21 males and 4 females; age range 10–60 years; mean age 34.8 years) selected from 40 patients referred to the Radiodiagnosis department with perianal sepsis, the study was conducted between October 2009 and September 2011, MRIs were performed and the results were ensured by surgical results, sensitivity, specificity and predictive values of MRIs were determined.

Results

25 patients with perianal sepsis were included in this study, 3 cases grade 1 (simple linear intersphincteric fistula), 2 cases grade 2 (intersphincteric fistula with abscess or secondary track), 9 cases grade 3 (trans-sphincteric fistula), 9 cases grade 4 (trans-sphincteric fistula with abscess (5 cases), secondary track within the ischiorectal fossa (3 cases) and both (1 case)) and 2 cases grade 5 (supralevator and translevator disease one case for each).

Conclusion

MRI is a useful procedure for successful management of peri-anal fistula by correct assessment of the extent of disease and relationship to sphincter complex. Also it helps in identification of secondary extensions, particularly horseshoe tracts and abscesses resulting in complete evaluation and highest possible diagnostic accuracy aiding successful surgical interventions, aiming to reduce complications and recurrences.     

Magnetic resonance imaging of extracranial head and neck tumours.

The role of magnetic resonance imaging (MRI) in the investigation of head and neck tumours (excluding those primarily arising from the central nervous system or orbits) has been investigated. Follow-up data were obtained on 45 scans on 42 patients. MRI provided significant additional information compared with computed tomography (CT) in nine out of 17 (53%) scans performed for staging purposes. In the assessment of 19 patients with suspected tumour recurrence, MRI demonstrated a sensitivity of 100%, a specificity of 80% and an accuracy of 89%.     

Magnetic resonance imaging of primary tumours and tumour-like lesions of bone

The experience with magnetic resonance imaging (MRI) of 81 patients with primary bone tumours and tumour-like lesions is reported. MRI proved to be a sensitive method of detecting primary bone tumours. Intramedullary and extraosseous parts of bone tumours were, delineated better than by plain films and computed tomography (CT). Surgical clips and Harrington rods did not appreciably limit the estimation of tumour recurrence. MRI provided definite advantages compared to CT in the surgical staging of bone tumours and tumour-like lesions. MRI was found to be an imaging method with low specificity. Differentiation of tissue components, such as haematoma, fat, necrosis, and cystic areas, led to a specific diagnosis only in rare cases. Plain films and CT were found to be superior to MRI in assessing the biological activity and the differential diagnosis of bone tumours and tumour-like lesions.     

Magnetic resonance imaging evaluation of spontaneous portosystemic collaterals

Three patients, two of whom had histories of episodic hepatic encephalopathy, were shown by magnetic resonance imaging (MRI) to have occult spontaneous portosystemic shunts. The multiplanar imaging capabilities of MRI provided an optimal, noninvasive method of visualization of collateral anatomy in each case.     

Magnetic resonance imaging in the evaluation of abscesses

Ten patients with percutaneous biopsy or surgically proven abscesses were evaluated with magnetic resonance imaging (MRI) to describe the appearance of abscesses, define the capability of MRI to localize abscesses, and compare the capabilities of MRI and CT for the diagnosis and determination of the extent of an abscess. Comparative CT scans were available in six cases. The most common MRI finding was an abnormal area of low signal intensity, either homogeneous or heterogeneous, on the short repetition rate (500 msec TR) images with a relative increase in signal intensity on the longer repetition rate (1500 or 2000 msec TR) images. MRI demonstrated a more clear delineation of the extent of inflammatory changes than did CT, and MRI demonstrated the abscess as a collection distinct from surrounding structures on at least one repetition rate. Intravenous contrast medium was unnecessary with MRI to evaluate vasculature or to define the capsule around an abscess. With CT, unless an abscess contained air or was of low attenuation, it often blended with the surrounding structures and was difficult to differentiate from them. Surgical clips in the postoperative patient with an abscess did not degrade the MR images as often occurred with CT. This study describes the MRI appearance of abscess and indicates a potential value of the use of MRI to evaluate abscess outside the central nervous system and spine.     

Magnetic resonance imaging evaluation of acute spine trauma

A comparison study of magnetic resonance imaging (MR), computed tomography (CT), and plain film evaluation of 113 consecutive spine trauma cases was conducted. The rate of true-positive findings (sensitivity) on MR was shown to be significantly higher than for CT or plain films in the evaluation of soft tissue or ligamentous injury (P<0.001). MR had a significantly lower rate of positive findings for fracture than CT (P<0.001) and was also shown to be significantly less sensitive for fracture than plain films (P<0.001). Spinal cord contusion, epidural hematoma, high-grade stenosis, and ligamentous or soft tissue injury were best evaluated with MR. MR, CT, and plain films are all important modalities for the evaluation of acute spine trauma. It is recommended that, after clinical examination, patients with spine trauma be evaluated first by plain film. If there is clinical or radiologic suspicion for acute spine injury, MR should be the next diagnostic procedure performed. If MR is positive for acute injury, CT may be indicated. CT best defines the extent of bony injury, and MR the extent of soft tissue injury, intrinsic spinal cord pathology, and extrinsic dural sac compression.     

Magnetic resonance imaging in the evaluation of pneumonia

Magnetic resonance imaging (MRI) of the lung is challenging because of substantial drawbacks. However, lung pathologies that are associated with increased attenuation values in CT enhance visualization in MRI: proton density is increased and tissue-air interfaces, resulting in susceptibility artifacts, are reduced in pneumonia, pneumonitis, edema, and carcinoma. On the other hand, many lung diseases result in shortness of breath, so that patients cannot hold their breath for long periods. Therefore, fast imaging techniques are required which should also allow for high spatial resolution so that small lesions can be detected. Calcifications and air pockets within lesions are not readily recognized with MRI. Thin section CT is standard for the diagnosis of pneumonia. With parallel imaging techniques, MRI examination of the lungs can be performed with short periods of breath holding, which allow for sub-centimeter resolution in the z-axis. Especially for follow-up examinations in immunocompromised patients and, in some instances, for the staging of malignant diseases (malignant pleural mesothelioma, lung cancer, respectively), MRI is very promising and may contribute to a decrease in the radiation exposure of the patients.     

MR imaging of epidermoids at the cerebellopontine angle.

The most common location of intracranial epidermoid is the cerebellopontine angle (CPA). The present study compared the visibility of epidermoid at the CPA in various pulse sequences. Seven patients with epidermoid at the CPA underwent conventional MR imaging (T(1)-, T(2)- and proton density-weighted imaging) as well as diffusion-weighted echo-planar imaging. Fast fluid-attenuated inversion recovery (FLAIR) sequences, magnetization transfer contrast (MTC) sequences, and MR cisternography were employed for selected patients. The signal intensity of the lesions relative to cerebrospinal fluid (CSF), the degree of lesion demarcation and the displacement of surrounding structures were evaluated. Proton density-weighted imaging depicted the lesions as hyper-intense to CSF with clearer delineation than T(1)- and T(2)-weighted imaging. Diffusion-weighted imaging depicted all lesions as strongly hyper-intense relative to CSF and brain tissue. FLAIR sequences depicted the lesions with mixed signal intensities but with poor-to-medium demarcation. MTC imaging increased delineation of the lesions to some degree. MR cisternography depicted the lesions as hypo-intense to CSF and clearly showed the anatomical relation to neighboring nerves and vessels. We concluded that diffusion-weighted imaging could specifically reveal an epidermoid at the CPA as a strongly hyper-intense lesion, and that MR cisternography is mandatory for preoperative planning.     

Magnetic resonance imaging in the evaluation of the brainstem

Magnetic resonance (MR) images of the brainstem region from 100 normal or asymptomatic individuals were reviewed in addition to those of 17 patients with intra-axial brainstem lesions and 15 patients with extra-axial masses around the brainstem. MR was able to demonstrate consistently the normal anatomy of the brainstem and adjacent cisterns, though the distinction between gray and white matter was seldom possible with the present technology. Masses in and around the brainstem were all accurately identified on MR and its sensitivity was superior to that of x-ray computed tomography (CT). These study results show that despite its technical limitations, MR is presently the examination of choice for the evaluation of brainstem abnormalities and eventually it will undoubtedly replace metrizamide CT cisternography.     

Magnetic resonance imaging in the evaluation of lung cancer

MRI is used most efficaciously in the evaluation of patients with bronchogenic carcinoma when employed as a tailored examination designed to answer specific questions relevant to patient management. CT continues to be used more generally in staging lung cancer when imaging beyond conventional chest radiography is required. Specific areas in which MRI can provide important and unique information (which may supplement a CT study) include the following: (1) evaluation of the local extent of superior sulcus tumors, and (2) distinction between stage IIIA (resectable) and stage IIIB (unresectable) tumors. Confirmation of tumor invasion of major mediastinal structures is necessary before depriving a patient of potential curative resection. MRI may contribute important information when CT findings are indefinite, particularly with regard to invasion of major cardiovascular structures (eg, superior vena cava, pulmonary artery, pericardium, and heart); invasion of the tracheal carina or bilateral involvement of main bronchi; and the presence of contralateral mediastinal or hilar lymphadenopathy. MRI should be considered as a primary imaging modality to evaluate central tumors in patients for whom intravenous contrast agents are contraindicated, and as a problem-solving modality when CT is inconclusive in the detection of a possible hilar or mediastinal mass. Other specific applications of MRI include the identification of tumor recurrence in the presence of radiation fibrosis, assessment of the extent of chest wall invasion of peripheral lung tumors, and the noninvasive characterization of adrenal masses. The scope of these MRI applications in patients with lung cancer may expand in the future with refinements in motion suppression techniques, implementation of ultrafast MRI (using variations of the echoplanar method), and further development of MRI spectroscopy and MRI contrast agents.     

Magnetic resonance imaging in the evaluation of the retroperitoneum

Magnetic resonance imaging techniques have made it possible to delineate a variety of pathologic processes in the retroperitoneum, including lymphadenopathy, atherosclerotic and aneurysmal disease of the aorta, congenital venous anomalies, and primary and secondary retroperitoneal neoplasms. The availability of multiplanar image display, the excellent soft tissue contrast resolution, and the fact that exogenous contrast materials are not needed are valuable assets of this imaging modality.     

Magnetic resonance imaging in the evaluation of the retroperitoneum

Magnetic resonance imaging techniques have made it possible to delineate a variety of pathologic processes in the retroperitoneum, including lymphadenopathy, athersclerotic and aneurysmal disease of the aorta, congenital venous anomalies, and primary and secondary retroperitoneal neoplasms. The availability of multiplanar image display, the excellent soft tissue contrast resolution, and the fact that exogenous contrast materials are not needed are valuable assets of this imaging modality.     

Magnetic resonance imaging in the evaluation of ligament injuries

Magnetic resonance imaging has had a dramatic effect on the means by which we diagnose ligament injuries. Tears resulting from either acute trauma or overuse can be detected noninvasively, directing appropriate therapy be it conservative or surgical. For the elite athlete, earlier diagnosis leads to earlier intervention, or alternatively, a normal MRI examination can result in an earlier return to play. While MRI is accepted for the diagnosis of certain injuries such as complete tears of the cruciate ligaments of the knee, other injuries, such as partial cruciate ligament tears or tears of the intercarpal ligaments of the wrist, remain controversial. Received: 4 August 1998 Revision requested: 1 October 1998 Revision received: 23 October 1998 Accepted: 29 October 1998