Faculty Bibliography

PURPOSE: To retrospectively determine the accuracy of low-dose (20-mAs) computed tomography (CT) in the diagnosis of acute appendicitis in children by using a technique that enables the simulation of human CT scans acquired at a lower tube current given the image acquired at a standard dose. MATERIALS AND METHODS: Institutional review board approval was obtained, informed consent was not required, and the study was HIPAA compliant. The authors reviewed 100 standard-dose pediatric abdominal-pelvic CT scans (50 positive and 50 negative scans) obtained in 100 patients and corresponding simulated low-dose (20-mAs) scans. The standard-dose scans were obtained for evaluation in patients suspected of having appendicitis. Scans were reviewed in randomized order by four experienced pediatric radiologists. The patients with positive findings included 21 girls (mean age, 9.2 years) and 29 boys (mean age, 8.4 years). The patients with negative findings included 28 girls (mean age, 9.2 years) and 22 boys (mean age, 8.4 years). Simulation was achieved by adding noise patterns from repeated 20-mAs scans of a pediatric pelvis phantom to the original scans obtained with a standard tube current. Observers recorded their confidence in the diagnosis of appendicitis by using a six-point scale. Dose-related changes were analyzed with generalized estimating equations and the nonparametric sign test. RESULTS: There was a statistically significant (P < .001, sign test) decrease in both sensitivity and accuracy with a lower tube current, from 91.5% with the original tube current to 77% with the lower tube current. A low dose was the only statistically significant (P < .001) risk factor for a false-negative result. The specificity was unchanged at 94% for both the images obtained with the original tube current and the simulated low-dose images. The overall accuracy decreased from 92% with the original dose to 86% with the low dose. CONCLUSION: Preliminary findings indicate that it is feasible to optimize the CT dose used to evaluate appendicitis in children by using phantom-based computer simulations

Metanephric adenoma (MA) is a renal tumor that is rarely found in children. We present a case of MA that was incidentally discovered in an 8-year-old child on computed tomography. We also review the literature regarding this lesion in the pediatric population. There are certain imaging features of MA that may suggest the diagnosis preoperatively. Metanephric adenoma is often hyperechoic on sonography, hyperdense on noncontrast computed tomography scans, and of low signal intensity on T1- and T2-weighted magnetic resonance images. Nephron sparring surgery has been performed in several cases. However, the distinction of MA from other metanephric lesions as well as from Wilms' tumor and papillary renal cell carcinoma may not be readily apparent at the time of surgery

Hepatic hematomas in newborn infants are not frequently detected clinically, but are often found at perinatal autopsies. These hematomas of the liver are usually subcapsular in location. A variety of etiologies for such hematomas has been implicated, such as trauma, sepsis, and coagulopathies. We present a neonate who presented with jaundice and abdominal distention. Initial imaging studies revealed a large intraparenchymal lesion of the liver, which was at first thought to be suspicious for neoplasm; however, MRI showed the lesion to be hemorrhagic and follow-up sonographic studies showed total resolution of this lesion, compatible with hematoma. The intraparenchymal location and the idiopathic nature of this lesion distinguish this case from others previously reported

To identify cell adhesion molecules required for angiogenesis, we used an in vitro model in which bovine capillary endothelial cells can be induced to form capillary-like tubes. Monoclonal antibodies directed against the carbohydrate epitopes sialyl Lewis-X and sialyl Lewis-A inhibited capillary formation. We postulated that a member of the selectin family of adhesion molecules may be involved in capillary formation because these proteins bind to sialyl Lewis-X/A-containing ligands. We isolated a 2.8-kilobase complementary DNA from a bovine capillary endothelial cell cDNA library which encodes a polypeptide with 71% identity to human E-selectin. We report here that antibody directed against the bovine E-selectin inhibited capillary formation, suggesting that in addition to its role in leukocyte adhesion to endothelium, a form of E-selectin is involved in capillary morphogenesis

A cDNA encoding a homologue of human P-selectin has been isolated from a bovine capillary endothelial cDNA library. The 2.7 kb cDNA encodes a 646 amino acid polypeptide with 77% identity to the human P-selectin except that it lacks three of the consensus repeat domains found in human P-selectin. Human P-selectin, expressed in platelets and endothelium, is a Ca(2+)-dependent receptor for myeloid cells that binds to carbohydrates on neutrophils and monocytes. To determine if bovine P-selectin exhibits a similar binding activity, its cDNA was expressed in COS cells and the ability of the transfectants to bind HL-60 human myelogenous leukemia cells was examined. The bovine P-selectin bound the myeloid cells in a manner similar to human P-selectin, indicating that the altered domain structure of bovine P-selectin does not affect P-selectin function in this in vitro cell adhesion assay

Most (approximately 80%) strains of Fusobacterium nucleatum adhere to human erythrocytes in a lectin-like manner that is strongly inhibited by N-acetyl-D-galactosamine (GalNAc). In this study, we investigated the capacity of F. nucleatum 10953, a strain that is weakly inhibited by GalNAc, to adhere to and activate human lymphocytes in vitro. Experiments using [3H]-labeled bacteria and scanning electron microscopy clearly showed that 10953 adhered to lymphocytes and that adherence was blocked by L-arginine+GalNAc greater than L-arginine much greater than GalNAc. Adherence was Ca(2+)-dependent, inhibited by pretreatment of the bacteria with proteases or heat, and unaffected by paraformaldehyde fixation of the bacteria. Strain 10953 induced lymphocyte mitogenesis that was blocked by L-arginine but not by GalNAc. These results suggest that certain strains of F. nucleatum, such as 10953, express a distinct, non-lectin-like mechanism by which they adhere to and activate lymphocytes. Activation of lymphocytes may be an important mechanism in the pathogenesis of periodontal diseases associated with these bacteria