Intracranial vascular malformations: MR and CT imaging

Twenty-four patients with 29 cerebrovascular malformations were evaluated with a combination of computed tomography (CT), angiography, and magnetic resonance (MR) imaging. Characteristics of the malformations on MR images were reviewed retrospectively, and a comparative evaluation of MR and CT images was made. Of 14 angiographically evident malformations, 13 intra-axial lesions were detected on both CT and MR images, and one dural malformation gave false-negative results on both modalities. The appearance of parenchymal lesions on MR images closely mirrored characteristic CT findings. Calcific foci were difficult to separate from vessels on both images. Clot was more easily identified on MR images. In the detection of 15 angiographically occult malformations, CT proved more sensitive when focal calcification was the only evidence of their presence. MR study failed to detect two small supratentorial lesions evidenced by faint calcifications on CT scans. In two patients, MR images showed small hemorrhages not detectable by CT, and MR provided strong evidence for the diagnosis of hematoma for 12 lesions. Angiographically evident malformations have a highly characteristic appearance on MR images. MR may be more sensitive than CT in the detection of small hemorrhagic foci associated with cryptic arteriovenous malformations and may add specificity in the diagnosis of occult malformations in some cases, but MR is less sensitive than CT for the detection of small calcified malformations.     

Intracranial tuberculoma: MR imaging

Summary MR studies of 6 patients with intracranial tuberculoma are reviewed. All patients also underwent CT scans which showed hypo- or isodense lesions with abnormal enhancement following contrast administration. MR showed lesions with prolongation of the T1 relaxation time in every case. On the T2-weighted sequences, the signal properties of the tuberculoma varied according to the stage of evolution of the lesion. Incipient tuberculomas appeared as scattered areas of hypointensity surrounded by edema. Mature tuberculomas were composed of a dark necrotic center surrounded by an isointense capsule which was, in turn, surrounded by edema. In one patient, the center of the lesion was hyperintense probably because of liquefaction and pus formation (tuberculous abscess). While both, CT and MR, were equally sensitive in visualizing the intracranial tuberculoma in every patient, MR was slightly superior in demonstrating the extent of the lesion, especially for brainstem tuberculomas. Nevertheless, the potential role for MR diagnosis of intracranial tuberculoma is limited by the fact that other infectious or neoplasic diseases may present similar findings. The diagnosis of intracranial tuberculoma should rest on a proper integration of data from clinical manifestations, cerebrospinal fluid analysis, and neuroimaging studies.Presented at the 23th Latinoamerican Congress of Neurosurgery, Acapulco, Mexico, 13–19 November 1988     

Intracranial aneurysms: MR imaging

Summary MR studies of 17 patients with 19 intracranial aneurysms are reviewed. All patients also underwent CT and angiography. MR has been able to visualize the aneurysms in all cases. Aneurysms present various MR appearances because of flow characteristics, thrombosis in different stages of organization, calcific and ferric deposits. Based on MR signal changes it is possible to distinguish between flow effects and histopathological components such as thrombosis. Flow patterns are complex and sometimes it is difficult to define the cause responsible for intraluminal signal. MR allows a precise definition of perilesional brain tissue and demonstrates associated lesions. Angiography remains the definitive procedure in the diagnosis of small aneurysms, but shows only that part of the lesion in continuity with the circulation. MR clearly delineates the size, the residual lumen and the extraaxial location of giant aneurysms. In completely thrombosed aneurysms, when CT suggest a tumor, MR is able to demonstrate the vascular nature of the lesion.     

Fetal thoracic abnormalities: MR imaging

PURPOSE: To elucidate the appearance of fetal thoracic abnormalities at prenatal magnetic resonance (MR) imaging and determine whether MR imaging yields information additional to that obtained with ultrasonography (US). MATERIALS AND METHODS: US and MR imaging data from 83 MR examinations of 74 fetuses with thoracic abnormalities and confirmatory US performed within 1 week before MR imaging were compared with respect to resulting changes in patient counseling and/or care. Lung parenchyma and lesion signal intensities and vascularity, airway, esophagus, and diaphragm appearances were reviewed retrospectively on MR images. Student t tests and analyses of variance were performed. RESULTS: MR imaging yielded information additional to that acquired with US in 28 (38%) of 74 fetuses. The additional findings were confirmed in 19 of the 28 fetuses at postnatal follow-up; no follow-up data were available for the other nine fetuses. Thoracic MR information affected care with regard to six (8%) of 74 fetuses. Mean gestational age of 15 fetuses with lung signal intensity (SI) slightly lower than that of amniotic fluid (28.4 weeks +/- 6.8 [SD]) at T2-weighted MR imaging was significantly older than that of 18 fetuses with intermediate SI (21.3 weeks +/- 4.3) (P <.05). Mean SI of 13 congenital cystic adenomatoid malformations (CCAMs) and/or sequestrations (1.74 +/- 1.05) at T2-weighted MR imaging was significantly higher than that of the normal lungs of 33 fetuses (2.63 +/-.63) (P <.001). Among nine studies in which vessels were visualized in CCAMs and/or sequestrations, six involved a normal vascular branching pattern. Portions of the esophagus were seen in 31 (36%) of 85 fetuses. Nonvisualization of a major airway was not sufficient for diagnosis of pulmonary atresia. Visualization of a portion of the esophagus did not correlate with esophageal atresia. In all except one fetus, who had anhydramnios and pulmonary hypoplasia, and the fetuses with congenital diaphragmatic hernia, at least a portion of the diaphragm was visualized at MR imaging. CONCLUSION: MR imaging yields information additional to that yielded with US in fetuses with thoracic abnormalities.     

Intracranial hematomas: imaging by high-field MR

Twenty intracranial hematomas between 1 day and over 1 year old were imaged using magnetic resonance at 1.5 T, with T1- and T2-weighted spin-echo pulse sequences. Characteristic intensity patterns were observed in the evolution of the hematomas, which could be staged as acute (less than 1 week old), subacute (greater than 1 week and less than 1 month old), or chronic (greater than 1 month old). Acute hematomas were characterized by central hypointensity on T2-weighted images (WIs). Subacute hematomas had peripheral hyperintensity on T1-WIs and then on T2-WIs. This hyperintensity proceeded to fill in the hematoma in the chronic stage. In subacute and chronic hematomas, there was hypointensity on T2-WIs in the immediately adjacent part of the brain. On T2-WIs of acute and subacute hematomas, the nearby white matter was characterized by hyperintensity, consistent with edema. A different mechanism is proposed for each of the three characteristic intensity patterns. Two of these mechanisms increase in proportion to the square of the magnetic field magnitude.     

Intracranial MR imaging of achondroplasia]

Intracranial MR imaging was performed in five patients with achondroplasia. All patients had narrowing of the subarachnoid space at the level of the foramen magnum that was mainly due to protrusion of the posterior aspect. Three patients had compressive deformities of the brainstem and/or upper cervical spine. Among them, two patients had deformities of the pons. Relative upward displacement of the brainstem was seen in all patients. Hydrocephalus was seen in three patients.     

肝脏磁化传递对比MRI:无法区分健康的肝脏和肝硬化

目的使用磁化传递脉冲频率偏离波谱评估磁化传递对比MRI区分健康的肝脏和肝硬化的能力。材料与方法符合HIPAA法案的前瞻性研究已获机构审查委员会批准,并获得所有参与者的书面知情同意书,使用蛋白浓度在     

Patellofemoral joint: kinematic MR imaging to assess tracking abnormalities

The patellofemoral joint was imaged with magnetic resonance (MR) in the axial plane while the knee was positioned from 0 degrees to 32 degrees of flexion (nine positions). These multiple sequential images obtained within the early phases of flexion of the knee were viewed in a "cine-loop" format, producing a kinematic study that clearly demonstrated the relationship of the patella to the trochlear groove. Four healthy subjects and one patient with known bilateral subluxing patellae were studied. The preliminary results suggest that kinematic MR imaging of the patellofemoral joint is potentially useful for the evaluation of patellar tracking abnormalities.     

Cardiac tumors and thrombus: evaluation with MR imaging

Thirty patients with a suspected cardiac or pericardial mass underwent MR imaging. Twenty-six also had two-dimensional (2D) echocardiography, and three also had CT; one patient had MR only. Overall, 18 (60%) of the 30 patients were found to have a mass lesion. The lesion was confirmed by biopsy, surgery, or unequivocal demonstration on CT, 2D echocardiography, and/or MR imaging. Fourteen of the lesions were soft-tissue or tumor masses, and four were thrombi. The findings on 2D echocardiography and MR were in agreement in 17 (65%) of 26 patients who had both studies. MR was equivocal or in error in two patients (7%), and 2D echocardiography was nondiagnostic in seven (27%). In all seven patients with equivocal 2D echocardiography, the diagnosis was made by MR. In the four patients who did not have 2D echocardiography, MR showed the mass clearly. MR imaging is useful in the diagnosis of cardiac mass lesions. It can be used effectively in addition to 2D echocardiography to increase the certainty of diagnosis, and it is useful when 2D echocardiography is equivocal or inadequate.     

Applying protein-based amide proton transfer MR imaging to distinguish solitary brain metastases from glioblastoma

Objectives

To determine the utility of amide proton transfer-weighted (APTw) MR imaging in distinguishing solitary brain metastases (SBMs) from glioblastomas (GBMs).

Methods

Forty-five patients with SBMs and 43 patients with GBMs underwent conventional and APT-weighted sequences before clinical intervention. The APTw parameters and relative APTw (rAPTw) parameters in the tumour core and the peritumoral brain zone (PBZ) were obtained and compared between SBMs and GBMs. The receiver-operating characteristic (ROC) curve was used to assess the best parameter for distinguishing between the two groups.

Results

The APTw_max, APTw_min, APTw_mean, rAPTw_max, rAPTw_min or rAPTw_mean values in the tumour core were not significantly different between the SBM and GBM groups (P?=?0.141, 0.361, 0.221, 0.305, 0.578 and 0.448, respectively). However, the APTw_max, APTw_min, APTw_mean, rAPTw_max, rAPTw_min or rAPTw_mean values in the PBZ were significantly lower in the SBM group than in the GBM group (P?<?0.001). The APTw_min values had the highest area under the ROC curve 0.905 and accuracy 85.2% in discriminating between the two neoplasms.

Conclusion

As a noninvasive imaging method, APT-weighted MR imaging can be used to distinguish SBMs from GBMs.

Key Points

? APTw values in the tumour core were not different between SBMs and GBMs. ? APTw values in peritumoral brain zone were lower in SBMs than in GBMs. ? The APTw _min was the best parameter to distinguish SBMs from GBMs.

     

Arterial input functions from MR phase imaging

A method is presented for obtaining high-sensitivity arterial input functions following bolus intravenous contrast agent administration. Arterial contrast agent is monitored by phase reconstruction of single-shot echo-planar images. During bolus injections of a gadolinium (Gd) agent in a baboon, data were acquired at the mid-abdominal aorta, and magnitude and phase-shift images were reconstructed. Pair-wise image subtraction was used to minimize phase aliasing. The phase-based method is shown to have a significant potential improvement in sensitivity compared to the magnitude approach. The phase method also has a general linear response to concentration. This method may have potential utility in quantitative imaging of blood flow and contrast agent kinetics.     

MR imaging of fetal abnormalities.

Our purpose was to evaluate the capability of ultrafast single-shot fast spin-echo MR imaging to assess normal fetal anatomy and abnormalities of different fetal organ systems. Fetal MR imaging was performed prospectively in consecutive 40 pregnant women because of abnormal findings or suspected fetal abnormalities on prenatal US. No statistically significant difference between US and MR imaging was found for the detection of abnormality in any organ system. MR imaging was slightly superior to US with regard to cerebral abnormalities only. In four (10%) of 40 fetuses, additional information provided by MR imaging altered counseling. However, MR imaging of the extremities-face and soft tissues was limited because of the lack of real-time information.     

MR imaging of pediatric cerebral abnormalities

One hundred sixteen magnetic resonance (MR) imaging studies from 105 pediatric patients with a variety of cerebral abnormalities were reviewed to determine the diagnostic efficacy of MR in the pediatric population. All subjects tolerated the MR procedure well, although sedation was necessary for younger children. Compared with CT, MR proved to be advantageous in detection and characterization of the pathology in 23 of 105 patients, especially when the abnormality was located along the base of the brain and midline, or when it involved primarily the white matter. Intracranial calcification was the one abnormality not detected with MR although dense calcifications could be seen as areas of low signal intensity. Some characteristics of various pathological entities were compared in an attempt to differentiate among abnormalities in the same anatomical location: craniopharyngioma from optic chiasm and hypothalamic glioma, cystic glioma from arachnoid cyst, and chronic subdural hematoma from subdural hygroma. The lack of ionizing radiation in MR is of particular interest in pediatric neuroradiology since radiation is of special concern in the young age group.     

Anterior tibial tendon abnormalities: MR imaging findings

PURPOSE: To retrospectively evaluate the magnetic resonance (MR) imaging findings of anterior tibial tendon (ATT) abnormalities. MATERIALS AND METHODS: Institutional review board approval was not necessary for review of patient images and was granted for examination of the volunteers; informed consent was obtained. MR imaging findings in 28 consecutive patients (20 women, eight men; mean age, 63.2 years) clinically suspected of having an ATT abnormality were compared with those in an age- and sex-matched control group of 28 asymptomatic volunteers (20 women, eight men; mean age, 62.9 years). Surgical correlation was available for 11 patients. The short-axis diameter of the ATT and the longitudinal extent of signal intensity abnormalities were measured (Mann-Whitney U test). Signal intensity abnormalities of the ATT and irregularities of the underlying tarsal bones were analyzed in consensus by two blinded radiologists (chi2 test). RESULTS: In the symptomatic group, three cases of tendinosis and 13 partial and 12 complete ATT tears were diagnosed. In 11 cases (one case of tendinosis and two cases of partial and eight cases of complete ATT tear), surgical correlation was available and the MR imaging diagnosis was confirmed. In the asymptomatic group, four cases of tendinosis of the ATT were seen. The ATT diameter was significantly thicker in symptomatic patients at 1 cm (5.1 vs 3.1 mm in control group, P < .001), 3 cm (5.8 vs 3.4 mm, P < .001), and 6 cm (5.4 vs 4.3 mm, P = .006) proximal to the distal point of insertion. Most ATT abnormalities (in 23 [82%] of 28 patients) were located within the first 3 cm proximal to the insertion. Signal intensity abnormalities were seen in the anterior portion of the ATT in two (7%) of the 28 symptomatic patients and in the posterior portion in 11 (39%); diffuse involvement was seen in 15 (54%). Bone spurs on the navicular surface (nine [32%] patients vs no [0%] control subjects, P = .001), a ridged shape of the medial surface of the medial cuneiform bone (13 [46%] vs one [4%], P < .001), and osteophyte formation at the first tarsometasarsal joint (eight [29%] vs two [7%], P = .036) were significantly more common in the symptomatic patient group. CONCLUSION: Characteristic findings of ATT abnormalities include tendon thickening (> or =5 mm) and diffuse or posterior signal intensity abnormalities of the tendon within 3 cm from the distal point of insertion.     

Intracranial epidermoid cyst with hemorrhage: MR imaging findings

We present a case of a 28-year-old woman with a cerebellopontine angle and prepontine cistern epidermoid cyst with unusual signal intensity. She presented with cranial nerve neuropathy and unsteady gait. MR imaging showed a tumor mass with central area of hemorrhage and a focal area of heterogeneous signal intensity with spotty enhancement, which correlated histologically to old blood in a cystic lumen and granulation of a cystic wall, with a large area of hemorrhage and mild vascularity.     

颅内髓母细胞瘤术后播散MRI表现

目的 分析颅内髓母细胞瘤(medulloblastoma,MB)术后复发播散的MRI特征,为临床治疗及估计预后提供参考.方法 回顾性分析48例颅内MB术后复发播散患者的临床及影像资料.结果 颅内MB术后播散,MRI表现为线状增厚型35例(72.9%),结节型40例(83.3%),呈单发或多发结节,肿块型14例(29%),弥漫性柔脑膜强化型4例(8.3%).增强扫描所有病例均发现线状增厚、结节状或团块状强化.21例(43.7%)出现不同程度的脑积水征象.结论 颅内MB术后易发生复发播散,MRI增强扫描对诊断、治疗、术后随访及估计预后提供有价值的信息.