Obstetrical magnetic resonance imaging: maternal anatomy

Eleven patients whose pregnancies were at 34-36 weeks of gestational development underwent magnetic resonance (MR) imaging. Images of the maternal pelvis were assessed for anatomical changes of pregnancy in comparison with MR images of five non-pregnant volunteers. The relationship of the fetal presenting part to the internal os of the cervix was seen in all patients. Effacement of the cervix was identified when present. The maternal spine demonstrated disk abnormalities in nine patients. Changes in venous flow patterns were readily identified in all patients. The inferior vena cava was flattened or obliterated, a high signal was present in the iliac vessels (TE 56), and large collateral vessels were present.     

Fast fetal magnetic resonance imaging

Fetal magnetic resonance imaging (MRI) can be used as a problem-solving tool when ultrasonic findings are equivocal. The role of fetal MRI has increased as obstetricians become aware of its potential and in utero therapy for anomalies becomes increasingly sophisticated. In this pictorial essay, we present a wide range of anomalies diagnosed or confirmed using MRI and discuss findings that help in the differential diagnosis.     

Hepatic vascular anatomy on magnetic resonance imaging

This study evaluated the ability of magnetic resonance imaging (MRI) to depict the hepatic vasculature and surgical anatomy of the liver using the transaxial, coronal, and sagittal planes. Retrospective analysis of the abdominal MRI examinations of 94 patients was performed. The spin-echo imaging technique was used to obtain transaxial images in all patients and coronal and sagittal sections in 35 of these patients. Overall, the hepatic vasculature was better delineated on the longer repetition rates (2000 msec TR) and the first echo images (28 msec TE). The inferior vena cava, right and middle hepatic veins, and main and right portal veins were seen in 100% of the cases in the transaxial plane. The left hepatic vein was seen in 98%, the left portal vein in 93%, and the hepatic artery in 44% in the transaxial plane. In the sagittal and coronal planes, the inferior vena cava and main and right portal veins were seen in 100% of cases. The other hepatic vasculature was less frequently demonstrated. In the sagittal plane, the right hepatic vein was seen in 85% of the cases, the left hepatic vein in 62%, the middle hepatic vein in 90%, the left portal vein in 90%, and the hepatic artery in 14%. In the coronal plane, the right hepatic vein was seen in 85% of cases, the left hepatic vein in 14%, the middle hepatic vein in 79%, the left portal vein in 71%, and the hepatic artery in 7%. These results are from preliminary work. Further developments with MRI technology may render better visualization of hepatic vasculature.     

High-resolution magnetic resonance imaging of the ankle: normal anatomy

An imaging-anatomic correlative study of ankle anatomy based upon six healthy adults and six fresh cadaveric specimens was performed to evaluate the diagnostic capabilities of magnetic resonance imaging (MRI). Optimal pulsing sequences and imaging planes for various structures of interest were established. MRI afforded exquisite depiction of anatomic detail, particularly the diagnostically important collateral ligaments. Limitations in the ability to delineate the joint capsule and articular cartilage were documented, with the former detectable only on T2 weighted images in the presence of synovial fluid.     

High-resolution magnetic resonance imaging of the wrist: normal anatomy

Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms, TE 25 ms) were most useful because of short imaging times, satisfactory image quality, and the absence of motion artifacts. The coronal plane provided the clearest definition of important structures. Potential diagnostic limitations exist due to the inability of MRI ot clearly delineate articular cartilage, joint capsules, and small interosseous ligmaents. The presence of intra-articular fluid in both living subjects and cadaveric specimens, however, allowed for fine depiction of these structures on T2 weighted images.     

High-resolution magnetic resonance imaging of the knee joint: normal anatomy

Excellent morphologic detail was depicted in thin-section, high-resolution magnetic resonance (MR) images obtained with the use of a solenoid surface coil specifically designed for the knee joint. The multiplanar anatomy of the knee was determined by correlating MR images of six fresh cadavers and 10 normal adult knees with corresponding photographs of cryoplaned specimens and by a cross-referencing multiplanar imaging technique.     

Serial fetal magnetic resonance imaging of cloacal exstrophy

Cloacal exstrophy (CE) is a rare congenital malformation involving the urinary, intestinal, and genital systems. We present a case of CE in which characteristic findings were detected at two serial fetal magnetic resonance imaging (MRI) sessions. At 18 weeks’ gestation, the initial fetal MRI revealed a cystic mass protruding from the infra-umbilical abdominal wall. During fetal development, the cystic mass disappeared, and an omphalocele and heterogeneous soft tissue mass were recognized at 28 weeks’ gestation. The bladder was not visualized on either examination. CE can be diagnosed by prenatal MRI, thereby permitting prenatal counseling and appropriate postnatal management.     

胎儿结肠三维磁共振成像研究

目的:探讨三维磁共振成像技术(3D-MRI)在显示胎儿结肠正常解剖和病变方面的临床应用价值.方法:对38例孕19～37周经超声诊断或怀疑胎儿畸形的孕妇在超声检查后1～2 d内进行MRI检查,使用单次激发快速自旋回波序列(SSFSE)行胎儿矢状面和冠状面常规扫描,三维快速扰相梯度回波序列(3D-FSPGR)行胎儿三雏磁共...     

Human fetal anatomy: MR imaging

Twenty-four pregnant women carrying 26 fetuses (two sets of twins) were imaged with magnetic resonance (MR) imaging at 0.35 T following sonographic evaluation. Each study was retrospectively evaluated to determine which of 33 normal fetal structures were visible on the images and which imaging parameters were most useful for depicting fetal anatomy. Fetal motion degraded fetal images in all but two cases, both with oligohydramnios and in the third trimester of gestation. Nevertheless, many fetal structures were identifiable, particularly in the third trimester. Visualization of fetal anatomy improved with intravenous maternal sedation in five cases. Relatively T1-weighted images occasionally offered the advantage of less image degradation owing to fetal motion and improved contrast between different fetal structures. More T2 weighting was believed to be advantageous in one case for outlining the fetal head and in one case for delineation of the brain. In many cases, structures were similarly identifiable (though with different signal intensities) regardless of the parameters selected. The authors conclude that MR imaging of many fetal structures is currently unsatisfactory and is probably of limited value, particularly in the first and second trimesters. However, the relative frequency and detail with which the fetal head and liver can be depicted indicate that these may be areas for further investigation, and the potential utility of imaging fetal fat warrants further investigation.     

Computed tomography and magnetic resonance imaging of the pericardium: anatomy and pathology.

The purpose of this article is to review the characteristics of computed tomography (CT) and magnetic resonance imaging (MRI) of the pericardium and pericardial diseases. Because patients with pericardial diseases usually present with nonspecific symptoms, these diseases may not be detected until they have reached an advanced stage. It is therefore important to distinguish between normal pericardial structure and disease. Multiplanar reconstruction images of CT and MRI are useful for evaluating faint changes of the pericardium. The specific pericardial diseases described in this article include pericardial cyst, constrictive pericarditis, pericarditis with radiation pericarditis, postoperative pericardial hematoma, and cardiac tamponade due to a paracardiac mass (lymphoma).     

High resolution surface coil magnetic resonance imaging of the spine: normal and pathologic anatomy

In a brief two year period, magnetic resonance imaging of the spine has developed from a single slice, low signal/noise ratio, extremely time consuming technique to a multiplanar, high resolution examination that can be performed in a time frame similar to that of CT imaging. MR has already assumed a primary imaging role in myelopathic states. It is premature to evaluate its place vis-a-vis CT and myelography in many other disease states of the spine, but clearly, MR is assuming an ever expanding role. As technical improvements continue, it is perhaps realistic to predict that magnetic resonance will, in the near future, assume a dominant role in the imaging of the spine for the demonstration of most types of spinal disease.     

Phenylketonuria: diffusion magnetic resonance imaging and proton magnetic resonance spectroscopy

Two patients with phenylketonuria are reported with white matter lesions. Diffusion magnetic resonance (MR) imaging revealed restricted diffusion patterns (high signal) on b = 1000 s/mm2 images associated with low apparent diffusion coefficient values ranging between 0.44 x 10-3 mm2/s and 0.56 x 10-3 mm2/s. On proton MR spectroscopy obtained in 1 of the patients, a prominent peak resonating at approximately 3.80 ppm was consistently present attributable to the peak rising from the alpha-proton of the phenylalanine molecule.     

Quantitative magnetic resonance imaging of the fetal brain in utero: Methods and applications

Application of modern magnetic resonance imaging (MRI) techniques to the live fetus in utero is a relatively recent endeavor. The relative advantages and disadvantages of clinical MRI relative to the widely used and accepted ultrasonographic approach are the subject of a continuing debate; however the focus of this review is on the even younger field of quantitative MRI as applied to non-invasive studies of fetal brain development. The techniques covered under this header include structural MRI when followed by quantitative (e.g., volumetric) analysis, as well as quantitative analyses of diffusion weighted imaging, diffusion tensor imaging, magnetic resonance spectroscopy and functional MRI. The majority of the published work reviewed here reflects information gathered from normal fetuses scanned during the 3^rd trimester, with relatively smaller number of studies of pathological samples including common congenital pathologies such as ventriculomegaly and viral infection.     

Hepatic cirrhosis: magnetic resonance imaging

The effect of periportal collagen deposition on magnetic resonance images and T1 and T2 relaxation times was studied in the rat. Hepatic cirrhosis was induced in 29 rats by chronic intraperitoneal thioacetamide injections. Another 14 rats in which liver abnormalities did not develop were used as controls. The rats were imaged using a small-bore resistive magnet. Histologic correlations and hydroxyproline measurements were performed to document the changes in periportal collagen deposition. The T1 and T2 relaxation times, determined both in vivo and in vitro with spectroscopy, were compared between the normal group and the group with moderate to severe histologic evidence of cirrhosis. The deposition of two to four times the normal amount of collagen in the liver did not affect the T1 or T2 relaxation time. Relatively pure periportal collagen fibrosis does not appear to affect the magnetic resonance image or T1 or T2 relaxation times of the rat liver.     

Aortic dissection: magnetic resonance imaging

Fifteen patients with suspected or known aortic dissection were imaged with magnetic resonance (MR). Thirteen of these patients were eventually shown to have dissection. In most instances the diagnosis was established by aortography and/or computed tomography (CT) prior to the MR study. Surgical proof (6/13) and/or aortographic proof (10/13) were available in 11/13 patients with aortic dissection. MR demonstrated the intimal flap and determined whether the dissection was type A or type B. In addition, MR: differentiated between the true and false lumens; determined the origins of the celiac, superior mesenteric, and renal arteries from the true or false lumen in the cases where the dissection extended into the abdominal aorta (8/12); allowed post-surgical surveillance of the dissection; and identified aortoannular ectasia in the three patients who had Marfan syndrome. In addition to the 13 cases with dissection, there were two cases in whom the diagnosis of dissection was excluded by MR. Our early experience suggests that MR can serve as the initial imaging test in clinically suspected cases of aortic dissection and that the information provided by MR is sufficient to manage many cases. Additionally, MR obviates the use of iodinated contrast media.