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Medical images typically exhibit complex feature space distributions due to high intra-class variation and inter-class ambiguity. Monolithic classification models are often problematic. In this study, we propose a novel Large Margin Local Estimate (LMLE) method for medical image classification. In the first step, the reference images are subcategorized, and local estimates of the test image are computed based on the reference subcategories. In the second step, the local estimates are fused in a large margin model to derive the similarity level between the test image and the reference images, and the test image is classified accordingly. For evaluation, the LMLE method is applied to classify image patches of different interstitial lung disease (ILD) patterns on high-resolution computed tomography (HRCT) images. We demonstrate promising performance improvement over the state-of-the-art.

Objective: Patients with polydipsia and intermittent hyponatremia have greater ventricle-brain ratios (VBRs) than matched patients without polydipsia and intermittent hyponatremia and normal subjects. Unlike previous studies, this study controlled for the impact of water loading when examining the volume of intracranial structures., Method: Under controlled conditions, eight male schizophrenic patients with polydipsia and intermittent hyponatremia were first assigned to either normal fluid intake or oral water loading and then the alternative condition the following day. Magnetic resonance imaging (MRI) volumetric measurements were made with the use of a standardized protocol., Results: During water loading, total VBR and lateral ventricle volume significantly decreased by 13.1% and 12.6%, respectively. A strong association between change in serum sodium concentration and change in VBR was noted across conditions., Conclusions: These findings indicate that 1) water loading does not account for the diminished brain volume observed in patients with polydipsia and intermittent hyponatremia in previous studies, and 2) hyponatremia can significantly alter brain morphology on MRI.

Purpose: To evaluate the imaging findings, possible pathogenesis, and frequency of hemorrhage near the tentorial surface of the cerebellum after supratentorial surgery., Methods: Over a 5-year period, 13 patients with posterior fossa hemorrhage after supratentorial surgery were identified with postoperative CT studies, which were obtained in all patients after craniotomy. Four of the 13 patients also had postoperative MR examinations. Preoperative and postoperative radiologic studies and medical records were reviewed., Results: All hemorrhages were located along the superior aspect of the cerebellum transversely oriented along the cerebellar fossa and fissures. None of the patients had coagulopathy or radiologic evidence of posterior fossa tumor or vascular malformation. None of the hemorrhages had an appearance typical of hypertensive hemorrhage. Ten patients (77%) had lumbar drains placed before surgery and all had epidural drains placed at the conclusion of surgery. One patient had surgery for a meningioma, and 12 had surgery for aneurysms. The frequency of hemorrhage after aneurysmal surgery was 3.5%. No neurologic deficits developed referable to the cerebellum., Conclusions: Hemorrhage should be viewed as a potentially benign sequela of surgery rather than as an indication of hypertension, aneurysm, or previously unrecognized vascular malformation or neoplasm.

Idiopathic intracranial hypertension is commonly associated with an empty sella, caused by herniation of subarachnoid cerebrospinal fluid through an absent or patulous diaphragma sellae. We describe the findings in two patients who presented with headache, papilledema, and visual disturbances. Diagnosis of idiopathic intracranial hypertension was made on the basis of clinical symptoms and laboratory data. Initial imaging studies in each patient showed an empty sella. After treatment, one with acetazolamide and the other with lumboperitoneal shunting, the appearance of the sellar contents became normal.

Surgical access to the sinus tympani remains a challenge for otologic surgeons. Usually, the retrotympanum is approached through the middle ear in an anterior to posterior direction during chronic ear surgery. Whether this is via a posterior tympanotomy or after canal wall down tympanomastoidectomy, visualization of the most posterior recess of the sinus tympani is often inadequate. The purpose of this investigation is two fold: (1) to describe the highly variable anatomy of the posterior tympanic cavity and (2) to review the retrofacial approach to the sinus tympani. Histologic sections, cadaver dissections, and diagrammatic illustrations are combined with computed tomographic (CT) imaging to provide a three-dimensional understanding of the sinus tympani and adjacent labyrinthine structures. Viewed from the mastoid, the anatomic structures that define the boundaries of the retrofacial approach include the facial nerve and stapedius muscle laterally, the lateral semicircular canal superiorly, the posterior semicircular canal posteromedially, the vestibule anteromedially, and the jugular bulb inferiorly. When the sinus tympani is well developed, saucerization within these boundaries gives wide access into the sinus and round window niche. The authors suggest that preoperative imaging can select patients who are candidates for a retrofacial approach to expose and remove disease in the sinus tympani. Contraindications to this approach include axial CT image measurements showing a contracted space between the posterior semicircular canal and the medial aspect of the facial nerve, lack of posterior expansion of the sinus tympani, and in cases where these measurements are marginal, the presence of a high jugular bulb or anteriorly positioned sigmoid sinus.

Purpose: To determine whether plain films alone are sufficient in the evaluation of stability of simple wedge-compression fractures of the lumbar spine., Methods: Plain films and CT scans of 53 consecutive patients seen during a 2-year period with lumbar spine fractures were retrospectively reviewed. Six readers blinded to the CT diagnosis independently read each patient's plain films. Plain-film findings were scored on a five-point graded response scale using criteria proposed by Gehweiler and Daffner. In addition, a fracture was considered to be possibly unstable if there was involvement of more than one vertebral level or greater than 50% loss of anterior vertebral body height. CT findings represented the standard for comparison. CT scans were independently evaluated by three additional readers. Two-column involvement, middle-column involvement alone but with retropulsion, multiple-level involvement, or greater than 50% loss of vertebral height indicated potential instability., Results: For 14 stable and 39 potentially unstable lumbar spine fractures, the pooled (mean) plain-film negative predictive value for detection of potentially unstable fractures was 0.62 (95% confidence interval, 0.53 to 0.70), with a sensitivity of 0.83 (95%, confidence interval; 0.78 to 0.87), and specificity of 0.80 (95% confidence interval, 0.70 to 0.87)., Conclusion: Plain films are not adequate for determining stability of lumbar spine fractures.

Referring physicians often are supplied with copies of images to illustrate a report of the findings of a radiologic study or so that the radiologist can retain the original images. The increasing costs of production, film, and recovery of chemicals have enhanced the requirement for a clean, low-cost dry printing process. An ink-jet gray-scale paper printer (Unitone, Scitex Medical Systems, Bedford, MA) can print high-quality (300 dots per inch [dpi]) images with an effective 10-bit gray scale range by using the Hertz continuous ink-jet method [1-3], which does not require the use of a darkroom or hazardous chemicals. Several types of media (matte paper, glossy paper, transparency film) with a printing area of 26.9 x 43.7 cm (10.6 x 17.4 inches) may be used. The consumables are approximately 50-70% less expensive than the cost of silver halide film, providing a cost advantage over film for referral and archival copies. The results of an initial evaluation of the ink-jet printer at our institution are reported here.

This preliminary study demonstrates the vital role that magnetic resonance imaging plays in the study of neuronal grafts in a nonhuman primate model of Huntington's disease. MRI scans were used to accurately locate and stereotactically lesion the anterior putamen of an adult rhesus monkey, thereby mimicking the anatomical and biochemical changes in Huntington's disease. Follow-up scans were utilized to confirm correct placement of the lesion and to stereotactically implant primate fetal neuronal tissue precisely into the lesion. Additionally, MRI appeared capable of imaging the fetal striatal grafts in rhesus monkeys. While the precise cellular composition of growing grafts was not identifiable on MRI scans, differentiation between normal, lesioned, and engrafted tissue was possible. Correlation of the magnetic resonance images of the grafted regions with actual graft tissue in perfused sections of the brain was shown. The use of magnetic resonance imaging, as indicated in these neuronal implantation studies, allows for a wide variety of future research possibilities where noninvasive and precise localization of the graft is mandated.

Purpose: To analyze and discuss CT and MR features of pleomorphic xanthoastrocytoma (PXA) and present salient histopathologic features of this distinctive astroglial tumor., Method: CT, MR, and histopathologic studies on seven patients with the histologic diagnosis of PXA were reviewed retrospectively., Results: All patients were in their first 3 decades of life when first diagnosed and demonstrated peripherally situated supratentorial tumors of varying size involving the superficial cortex and leptomeninges. Five of six cases examined with CT showed areas of mixed attenuation with four demonstrating well-demarcated enhancement. MR demonstrated low or mixed signal intensity on T1-weighted and high or mixed signal intensity on T2-weighted sequences. All five who received gadopentetate dimeglumine showed well-defined enhancement. Three showed cyst formation. Typical histologic features included marked cellular pleomorphism with giant cells, bizarre nuclei, variable cytoplasmic lipidization and positive immunoreactivity for glial fibrillary acidic protein. Necrosis and endothelial-pericytic cell proliferation were absent., Conclusion: PXA has a highly suggestive neuroradiologic and distinctive histopathologic appearance.

Cerebral vasospasm continues to be the leading treatable cause of morbidity and mortality following aneurysmal subarachnoid hemorrhage. In this preliminary anecdotal series of 12 patients who were candidates for balloon angioplasty, vasospasm was treated instead with intra-arterial papaverine. Eight patients had marked angiographic reversal of the arterial narrowing following papaverine infusion, four of whom showed dramatic reversal of profound neurological deficits. Two patients deteriorated clinically 5 days after the initially successful papaverine infusions. In both, repeat angiography demonstrated severe recurrent vasospasm, which was partially reversed with a second intra-arterial papaverine treatment. Two patients developed focal neurological deficits during papaverine infusion, which resolved spontaneously over several hours after cessation of the intra-arterial infusion. Arterial narrowing in the posterior circulation and middle cerebral artery distribution appeared to be more responsive to papaverine infusion than was spasm in the anterior cerebral arteries. The infusion of 300 mg of papaverine over 1 hour seemed to be an adequate and safe dose to effect these angiographic and clinical improvements.

We have presented two cases of chordoma arising from an unusual location within the skull. Chordomas in the skull usually arise from within the body of the clivus, reputedly from notochordal remnants. The first case, which was diagnosed both with CT and MRI, had its origin from the petrous bone, with extension into the left cerebellopontine angle. Chordoma was not considered high on the list of differential diagnoses. A right pontine hemorrhage, which was evacuated surgically, was diagnosed in the second case both from its clinical appearance and from that on CT scan. Only when bone windowing technique was used with CT was a lytic lesion of the right petrous bone evident. Chordoma was only diagnosed on autopsy. In reviewing these two cases and the literature, it is evident that chordoma must be considered in the differential diagnosis of erosive lesions of the petrous bone.

MR imaging of four children with neurofibromatosis demonstrated areas of increased T2 signal involving widespread multifocal regions of basal ganglia and brainstem. Such abnormalities have not been previously reported. No corresponding CT abnormalities were present. These regions may represent hamartomatous or low-grade gliomatous change, and appear to be characteristic of neurofibromatosis in children.

Twenty-seven new cases of stroke in Down syndrome are reported, two probands, 13 patients from review of institutional records, and 12 patients from a survey of child neurologists. Forty-one patients from previous reports are summarized. Most stroke episodes were related to congenital heart disease and infections. Seven cases were associated with angiographic abnormalities; there were three cases of unknown etiology and four cases of moyamoya. The understanding of moyamoya and other causes of stroke may be advanced by further study of stroke in Down syndrome patients.

Simple meningoceles are infrequent forms of dysraphism and are often benign. They have been associated with other spinal anomalies. The uncommon cervical meningocele may have a higher propensity to be associated with other spinal anomalies. Four patients with cervical meningocele are presented with radiographic evaluation and clinical course. Multiple abnormalities were documented radiographically and operatively, including hydrocephalus, Chiari malformation, hydromyelia, lipomeningomyelocele, tethered cord, thickened filum terminale, diastematomyelia, Klippel-Feil syndrome, and thoracic hemivertebrae. Prior to the development of any late neurological abnormality from associated spinal anomalies, magnetic resonance imaging is recommended early in a child born with a simple meningocele.

A 2-day-old neonate with a spinal cord arteriovenous malformation developed severe paraparesis. The abrupt neurological deterioration was not associated with hemorrhage or aneurysmal dilatation. Ischemic damage of the spinal cord is suggested as the cause of the clinical manifestation.

Two cases of renal cell carcinoma associated with polycystic disease of the kidney are presented. The literature is reviewed and the angiographic findings are discussed. These cases suggest that angiography is necessary to make the diagnosis of renal tumors associated with renal polycystic disease.

A case of symptomatic Rathke's cleft cyst was studied preoperatively with x-ray computed tomographic and magnetic resonance imaging. A Rathke's cleft cyst may be differentiated from other cystic-appearing sellar masses.

The most common anomaly of the lumbosacral nerve roots consists of a composite root sleeve containing the roots for two spinal nerves. Before the advent of water-soluble myelography, this anomaly was rarely diagnosed except at operation. Metrizamide myelography readily demonstrates the anomaly because of improved filling of the root sleeves and greater definition of the nerve roots within the subarachnoid space. However, an underlying disk herniation may not be evident on the myelogram because of the unique anatomic configuration.

Thrombosis of the deep cerebral venous system is usually fatal, and patients are frequently stuporous or comatose at presentation. This report describes serial radiological and neuropsychological observations in an 18-year-old woman who remained alert and survived this disorder. In association with diencephalic edema seen on computed tomographic scan, she demonstrated disorientation, abulia, attentional deficits, memory loss, and dyscalculia and had impaired IQ scores: the performance scores were worse than the verbal scores. Significant aphasia or sensory loss was absent. She recovered full intellectual capacity in the course of follow-up examinations, and the diencephalic edema seen on the computed tomographic scan resolved despite persistent thrombosis of the straight sinus demonstrable on follow-up digital angiography.