Accuracy of MRI in defining tumor-free margin in optic nerve glioma surgery.

PURPOSE: To determine the value of preoperative MRI in predicting the histopathologic margin of optic nerve glioma undergoing surgical resection. METHODS: Retrospective, noncomparative, multicenter case series of patients diagnosed with prechiasmal optic nerve glioma, using MRI, who underwent surgical resection. Clinical data were abstracted from patient medical records at 6 medical centers through a survey vehicle. Preoperative MRI findings were compared with intraoperative findings and postoperative histopathologic interpretations of the posterior margins of 13 surgically resected optic nerve gliomas. RESULTS: A total of 13 patient submissions qualified for study entry based on preoperative MRI having identified a unilateral optic glioma anterior to the optic chiasm. Of these, 2 cases (15%) demonstrated an abnormal macroscopic appearance of the chiasm intraoperatively and were surgically debulked rather than resected as planned preoperatively. The remaining 11 patients underwent resection posterior to the margins indicated by preoperative MRI. Of these, 3 (27%) demonstrated evidence of microscopically positive margins on histopathologic examination. Follow up ranged from 3 months to 21 years. One patient with involvement of the chiasm manifested tumor growth; no other recurrences or evidence of growth occurred in the remaining patients, including 1 other case with involvement of the chiasm and 3 cases with positive surgical margins. CONCLUSIONS: Unilateral optic nerve gliomas limited to the prechiasmatic nerve on MRI not infrequently extend beyond the MRI borders. This finding is of significance when considering management options, particularly surgical resection.

Fast decision in favor of the slow fission process.

The fission probability P(f) of highly excited targetlike nuclei produced in reactions of 2.5 GeV protons on Au, Bi, and U was studied as a function of excitation energy E* whereby E* is deduced eventwise from the multiplicity of evaporated light particles. At the highest E* of 1000 MeV P(f) amounts to approximately 30% with all 3 target nuclei irrespective of the initial fissility. Statistical-model calculations satisfactorily reproduce the observed evolution of P(f) with E*--provided that no extra transient delay is introduced. Fission thus is decided upon very fast and early in the long deexcitation chain towards scission which comprises as much as approximately 80% of all evaporated alpha particles.

Preadsorption of polymers on glass and silica to reduce fibrinogen adsorption.

Glass and silica beads were precoated with various polymers to obtain steric exclusion chromatography (SEC) supports which are nonadsorbant for hydrophilic macromolecules. The efficiency of this treatment was estimated by subsequent radiolabeled fibrinogen adsorption. The result obtained with a block copolymer was better than with various hydrophilic homopolymers. This ABA type block copolymer, where A is a poly(N-acetylethyleneimine) (PAEI) sequence and B a polyethylene oxide (PEO) sequence was preadsorbed at pH 4.5 and 25 degrees C; the fibrinogen adsorption was reduced to less than 5% of the value observed on untreated solid surfaces. Thus the hemocompatibility of solid supports should be increased by precoating with this block copolymer. Results for nonporous glass beads and porous silica particles were in good correlation.

Synthesis and adsorption of a poly(N-acetylethyleneimine)-polyethyleneoxide-poly (N-acetylethyleneimine) triblock-copolymer at a silica/solution interface. Influence of its preadsorption on platelet adhesion and fibrinogen adsorption.

The synthesis of a triblock copolymer poly-(N-acetylethyleneimine)-polyethylenoxide-poly(N-acet ylethyleneimine) includes two successive steps: the first is the functionalization of a poly(ethyleneglycol) precursor by creating sulfonic esters at its chain ends, the second uses these esters to initiate the cationic polymerization of 2-methyl-2-oxazoline. Homopolymers appear in the raw product; hence successive selective extractions of the copolymer with benzene and dioxane are necessary. The final yield in pure copolymer was 11%. The copolymer was characterized by UV and 1H-NMR spectrometry and light scattering. Adsorption isotherms were determined on silica, for varying pH and salt concentration. Optimum conditions for coating silica with the polymer were determined. The efficiency of this precoating to reduce the adsorption of fibrinogen was very high (99.2% reduction with respect to bare silica). Steric exclusion chromatography of a variety of proteins gave a satisfactory calibration curve. Platelet accumulation on copolymer precoated glass was reduced to 10-20% of its value on bare glass, a result superior to that obtained by albumin passivation of the same glass surface.