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The brain illustrations of Vesalius and Willis were the first in anatomic history with pictorial accuracy. Their illustrations, illustrators, and methods are discussed. Woodcut blocks were used for the prints of figures in the Vesalian anatomy. Figures of the brain appear to be done after external fixation in the work of Willis.

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Forty-two postmortem formalin-fixed brains of known patients with AIDS were examined with T2-weighted MR imaging before brain cutting. The gross and microscopic brain findings were correlated with the T2 signal changes in the postmortem MR imaging. The brains included examples of progressive multifocal leukoencephalopathy with involvement of the central brain and cerebellum. The authors also encountered the coexistence of progressive multifocal leukoencephalopathy and HIV encephalitis, and the T2 signal changes for each were compared. The T2 signal changes of leptomeningeal and perivascular space cryptococcal infection and CMV ependymitis are documented. Several expressions of primary cerebral lymphoma, including large nodules, choroid plexus infiltration, and diffuse microscopic sites of tumor also are assessed.

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Leptomeningeal enhancement on CT and MR imaging studies secondary to cryptococcal meningitis is an uncommon finding. In immunocompromised patients, this meningitis incites only a mild inflammatory reaction and abnormalities are often absent on imaging studies. We recently encountered two patients with cryptococcal meningitis in whom postcontrast MR imaging showed thick enhancing subarachnoid spaces. Both had cryptococcal meningitis at autopsy. In a different patient with cryptococcal meningitis, postmortem MR imaging and pathologic examinations showed that these areas of enhancement correspond to abundant mucoid material secreted by the yeasts.

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Postmortem magnetic resonance (MR) imaging features of different types of lobar cerebral infarction are correlated with the findings in gross and histologic specimens. The postmortem findings are also correlated with in vivo findings in similar cases selected from teaching files. In acute infarction, white matter vasogenic edema leads to high signal intensity on T2-weighted images and blurring of the gray-white matter junction. Petechial hemorrhage in the cortex results in inhomogeneous signal intensity on T2-weighted images. In laminar necrosis, the hyperintense cortex on T1-weighted images is due not to hemorrhage but possibly to necrosis and the presence of lipid-laden macrophages. In subacute infarction, cortical edema and necrosis may cause the gyral pattern of enhancement. Meningeal inflammation and early fibrosis are probably responsible for meningeal enhancement. In chronic infarction, gliosis and cystic malacia are responsible for the increased signal intensity of white matter on T2-weighted images. Knowledge of the pathologic features of cerebral infarction helps in understanding the MR imaging findings.

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RATIONALE AND OBJECTIVES: We sought to demonstrate the usefulness of proton and fluorine magnetic resonance spectroscopy (MRS) techniques in characterizing small ring enhancing lesions produced by experimental malignant gliomas. METHODS: The growth characteristics of a rat glioma model (RT2) were studied using contrast-enhanced magnetic resonance imaging scans of the tumors and histologic correlates obtained at various times. Changes in tumor metabolite levels were monitored on a serial basis using water-suppressed proton spectroscopy. The existence of tumor hypoxia was established using 19F MRS in combination with a fluorinated nitroimidazole and subsequently confirmed by immunohistochemical staining of tumor sections. RESULTS: Ring-enhancing lesions are produced by RT2 rat brain gliomas approximately 7 days after intracerebral implantation. Beginning at day 5, marked deviations in brain metabolite levels are observed on proton MR spectra. However, while the signal from the fluorinated nitroimidazole is first detected by 19F MRS at day 7, immunohistochemical staining of tissue sections reveals bound drug as early as day 5, when the first histologic signs of necrosis become apparent. CONCLUSIONS: Magnetic resonance imaging of RT2 rat brain glioma exhibits ring-enhancing characteristics similar to those observed in clinical studies. The appearance of the ring enhancement corresponds with the development of central necrosis and could serve as an indicator for rapid growth. Proton and fluorine MRS may be useful in confirming that a small ring-enhancing lesion represents an active tumor process early in its development.

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Fifty-one patients with ultrasound diagnosis of intraventricular hemorrhage (Grades III and IV) were studied retrospectively for the presence of ependymal echogenicity. The sonographic findings were then correlated with histologic findings in six autopsy cases. Forty-one out of fifty-one newborns with intraventricular hemorrhage developed ependymal echogenicity on serial ultrasound studies. This echogenicity appeared approximately seven days after the hemorrhagic event and usually disappeared in about six weeks. Histologic examination revealed disruptions in the ependyma with proliferation and extension of subependymal glial cells onto the ventricular surface in those cases in which ependymal echogenicity was present at the time of death. This layer of proliferating subependymal glial cells may account for the ependymal echogenicity.

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We reviewed 104 consecutive cases of closed dysraphism in patients seen at one institution between December 1984 and June 1987. All patients had myelographic studies, and 43 had associated CT examinations. Clinical and surgical findings (64 patients) were correlated with myelographic information. Twenty-three patients (22%) with clinical or plain film findings compatible with dysraphism had normal-appearing cords on conventional myelography, movement between supine and prone positions, and no lesions in the spinal canal. Cerebellar tonsillar ectopia (majority of tonsils between foramen magnum and C1) was found in 17 patients (16%). Six patients (6%) exhibited varying degrees of hydromyelia. In the supine position, CT-myelography of meningoceles, meningomyeloceles, or lipomeningomyeloceles may limit demonstration of the neural placode and nerve roots because of compression of the CSF-containing sac. In the decubitus position, CT scans improved demonstration of neural tissue-CSF space relationships. CT scans were useful in demonstrating anomalous paraspinal bones, diastematomyelia spurs, and spinal and sacral bone deficiency. Axial CT-myelography of intradural lipomas showed apparent neural tissue extension into the lipomas.

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Twenty-three pulmonary pseudocysts were identified in 20 preterm neonates undergoing mechanically assisted ventilation. Most of the pseudocysts occurred in a right parahilar location; cysts were either single (13) or multiple/multilocular (10). The pseudocysts persisted from less than 2 days to longer than 3 months (modal duration, 7 days), and they were commonly associated with generalized pulmonary interstitial emphysema (18 of 20), pneumothorax (18 of 20), bronchopulmonary dysplasia (16 of 20), and pneumomediastinum (six of 20). The reason for the predominantly right parahilar location of these pseudocysts remains uncertain. Pulmonary pseudocysts are almost always right-sided and are associated with pulmonary interstitial emphysema and pneumothoraces; complete resolution usually occurs.

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The authors have developed a resident evaluation system that minimizes inefficiencies and achieves the aims of evaluation. Individual resident performance is evaluated on each monthly rotation by those who have had significant contact with him as determined by the resident. Residents are rated as "below," "adequate," or "above" for these performance categories: (1) overall performance, (2) basic knowledge, (3) organizational skills, (4) communication skills, (5) interpersonal relationships, and (6) other areas and comments. The results are shared with the resident in a feedback session and recommendations made. These evaluations are summarized and discussed with the resident by the program director at the end of each year. This system has proved to be an efficient use of attending radiologist's and program director's time. The format has been accepted readily by all participants. The system has been helpful in identifying problem areas in resident performance and in curriculum and has resulted in prompt corrective action.

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A multimodality projection console for the radiology conference room is described. The configuration of the TV camera, view boxes, switches, and adjacent lectern allows better transmission and easier manipulation of images during consultation and lecture sessions with the faculty, and house officers.

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Residency recruitment in diagnostic radiology remains a challenge. We recommend a unified policy of recruitment, to be agreed upon and adhered to by all residency training program directors. We endorse the action discussed at the 1985 Residency Training Program Symposium in Nashville to institute a Resident Match and strongly urge all program directors to participate. With more qualified candidates and a shrinking number of positions, it is the only rational solution to this dilemma.

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Massive thymic hyperplasia in the neonate and young infant can be difficult to diagnose. Differentiation from neoplastic lesions may require thoracotomy for a pathologic specimen. We review a case in a 15-month-old child referred to our institution and discuss the radiographic, ultrasound, and computerized tomographic features of hyperplastic thymic tissue. We review current concepts of the hyperplastic thymus as an anterior mediastinal mass in infancy.

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Three cases of omphalomesenteric band obstruction in early infancy with various radiographic presentations, including intermittent obstruction in one, are reported. Small-bowel volvulus was found in all three patients at surgery. One case progressed to bowel necrosis with portal venous gas. A survey of the mode of presentation, surgical findings, and pathology of 135 published cases of intestinal obstruction in children demonstrates that a closed loop, with or without volvulus, is the most common complication of remnant bands.

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