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OBJECTIVE: The objective of our study was to evaluate the morphologic appearances of small-bowel lymphoma using MR enterography to identify key morphologic traits capable of providing an association between imaging manifestations and likely histologic diagnosis. MATERIALS AND METHODS: Over a 54-month period, 10 patients with subsequently confirmed small-bowel lymphoma were imaged using a standardized MR enterography technique. Retrospective chart review was performed to detect associated disease processes, such as celiac disease. The morphologic characteristics of each segment with lymphomatous involvement were evaluated with respect to tumor location, tumor size, mural characteristics, fold features, loop dilatation, luminal stricturing, mesenteric or antimesenteric distribution, mesenteric involvement, and signal intensity. RESULTS: Nineteen distinct segments of lymphomatous involvement were identified in 10 patients, and underlying celiac disease was confirmed in six of the 10 patients. This patient group comprised 10 patients with non-Hodgkin's lymphoma (NHL) of various subtypes. No cases of Hodgkin's lymphoma were encountered. Analysis revealed celiac NHL enteropathy to have a tendency toward localization to a single, long (> 10 cm), smooth continuous bowel segment, often with aneurysmal loop dilatation, in the absence of a distinct mesenteric or antimesenteric distribution. Luminal stricturing was encountered in cases of low-grade lymphoma, whereas mesenteric fat infiltration represented a characteristic of high-grade disease. CONCLUSION: We describe the characteristics of small-bowel lymphoma on MR enterography, identifying a number of key features that may help the interpreting radiologist in suggesting the underlying histologic subtype and whether the presence of underlying celiac disease is likely.

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Atlanto-occipital dislocation (AOD) is a devastating condition that frequently results in prehospital cardiorespiratory arrest and accounts for 15% of fatal spinal trauma. Atlanto-occipital dislocation occurs 5 times more commonly in children than adults, and is believed to be caused by hyperextension. Because of improvements in prehospital resuscitation, more victims with AOD now survive to reach the emergency department. Neurologic injury is usually severe secondary to ligamentous disruption that allows the cranium to move with respect to the cervical spine, and associated facial and head injuries are common. There are, however, reports of survivors without neurologic deficits. We present the case of a 46-year-old woman who suffered an AOD after a motor vehicle crash and we discuss the diagnosis of this condition. The signs of AOD are often subtle, and the possibility of this diagnosis must be kept in mind in all patients with a neck injury, even in the absence of neurologic signs. A systematic approach to assessing the cranio-cervical relationship on the lateral cervical x-ray and the appropriate use of CT scanning is essential to identifying AOD. Through this case report we hope to familiarize clinicians with mechanisms of injury and appropriate imaging interpretation that will assist in the diagnosis of AOD.

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OBJECTIVE: The aim of our study was to compare the assessment of peripancreatic lymph nodes using CT with the gold standard of detailed histopathologic assessment of resected specimens in patients with pancreatic ductal adenocarcinoma. SUBJECTS AND METHODS: Sixty-two patients with presumed pancreatic carcinoma were prospectively studied with dual-phase contrast-enhanced helical CT, and images were interpreted in consensus by three radiologists. Complete surgical resection was performed in 28 patients. A detailed nodal classification system was used for radiologic, surgical, and pathologic staging in the nine patients whose final diagnosis at histology was pancreatic ductal adenocarcinoma. RESULTS: Forty lymph nodes were prospectively identified on CT in these nine patients. Two of 23 nodes (9%) measuring less than 5 mm in the short-axis diameter were malignant, four of 11 nodes (36%) measuring 5-10 mm were malignant, and one of six nodes (17%) larger than 10 mm was malignant. Using a short-axis diameter of greater than 10 mm as the criterion for nodal involvement, we found a sensitivity of 14% (1/7) and a specificity of 85% (28/33), with a positive predictive value of 17% (1/6), a negative predictive value of 82% (28/34), and an overall accuracy of 73% (29/40). Ovoid nodal shape, clustering of nodes, and the absence of a fatty hilum were not useful predictors of malignancy on CT. CONCLUSION: In resectable pancreatic ductal adenocarcinoma, CT is not accurate overall for the prediction of nodal involvement. In a patient with presumed pancreatic carcinoma that is considered to be resectable, the depiction on CT of peripancreatic nodes should not prevent attempted curative resection.

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Certain pathologic conditions have classic radiologic manifestations that resemble various types of food. These "food signs" are highly memorable and easily recognizable and include findings that resemble various fruits and vegetables; meat, fish, and egg dishes; pasta, rice, grains, and bread (carbohydrates); desserts, cakes, and candy; and dishes, cutlery, condiments, and so on. It is important that radiologists recognize these classic signs, which will allow confident diagnosis on the basis of imaging findings alone or narrowing of the differential diagnosis.

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The cervical spine is a common focus of destruction from rheumatoid arthritis, second only to the metacarpophalangeal joints. Joint, bone and ligament damage in the cervical spine leads to subluxations which can cause cervical cord compression resulting in paralysis and even sudden death. Because many patients with significant subluxations are asymptomatic, the radiologist plays a key role in recognizing the clinically important clues to instability on plain radiographs of the cervical spine-often difficult in rheumatoid arthritis when the bony landmarks are osteoporotic or eroded. This review focuses on the signs of instability on plain radiographs of the cervical spine, using diagrams and clinical examples to illustrate methods of identifying significant subluxations in rheumatoid arthritis.

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AIMS: To measure the range of rotation and determine the instantaneous axis of rotation of the atlanto-axial joint in healthy volunteers using magnetic resonance imaging (MRI) and to highlight the appearances of the rotated atlanto-axial joint on computed tomography (CT) and MRI. MATERIALS AND METHODS: Twenty-eight healthy volunteers were examined using MRI during maximal head rotation. In addition, an anatomical specimen of the atlanto-axial joint, fixed in varying degrees of rotation, was imaged using CT. RESULTS: At the extremes of physiological rotation in healthy subjects there is striking but incomplete loss of contact between the articular surfaces of the atlas (C1) and the axis (C2). The range of rotation to the right was 20-48.5 degrees (mean 32.4 degrees ) and to the left was 13-52.75 degrees (mean 34.2 degrees ). There was no significant difference between rotation to the right and left (P = 0.455). Total rotation was 45-88.5 degrees (mean 69.25 degrees ). The instantaneous axis of rotation was located within the odontoid peg. CONCLUSION: There is a wide range of atlanto-axial rotation in normal subjects. The instantaneous axis of rotation lies within the odontoid peg. The appearances of the rotated atlanto-axial joint are striking and may be misinterpreted as subluxation.

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The vertebral column is composed of a series of joints, each capable of a specific range of movement. To investigate these movements, a study into the physiological range of rotation at the atlanto-axial joint has been undertaken. The movements and their interpretation under imaging conditions are crucial if any underlying spinal deformity or the consequences of trauma are present in an individual. 28 healthy volunteers were examined using dynamic Magnetic Resonance Imaging with maximum head rotation to the right and left sides in turn. An anatomical specimen of the atlanto-occipital joint was imaged using Computed Tomography with the specimen fixed in varying degrees of rotation. The results indicate that there is a significant but incomplete loss of contact between the articular surfaces of C1 (atlas) and C2 (axis). The range of motion to the right was between 20 and 48.5 degrees (mean 32.4 degrees) and to the left was between 13 and 52.75 degrees (mean 3.2 degrees). Statistical significance between left and right movement was not demonstrated. The instantaneous axis of rotation was examined for the joint and was found to be located within the odontoid peg (dens). These findings indicated that a wide range of movement occurs within the atlanto-axial joint in normal subjects. Furthermore, the appearances under imaging could be misinterpreted as a pathological subluxation. This has implications if the subject with a spinal deformity also has a dysplasia associated with a potential subluxation. The siting of the instantaneous axis of rotation within the odontoid is also important in furthering the understanding of the movement of this joint.

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