High relaxivity trimetallic nitride (Gd3N) metallofullerene MRI contrast agents with optimized functionality.

Water-soluble poly(ethylene glycol) (PEG) functionalized and hydroxylated endohedral trimetallic nitride metallofullerene derivatives, Gd(3)N@C(80)[DiPEG(OH)(x)], have been synthesized and characterized. The (1)H MRI relaxivities in aqueous solution were measured for the derivatives with four different molecular weights of PEG (350-5000 Da) at 0.35, 2.4, and 9.4 T. The 350/750 Da PEG derivatives have the highest relaxivities among the derivatives, 237/232 mM(-1) s(-1) for r(1) and 460/398 mM(-1) s(-1) for r(2) (79/77 mM(-1) s(-1) and 153/133 mM(-1) s(-1) based on Gd(3+) ion), respectively, at a clinical-range magnetic field of 2.4 T. These represent some of the highest relaxivities reported for commercial or investigational MRI contrast agents. Dynamic light scattering results confirm a larger average size for 350/750 Da PEGs derivatives (95/96 nm) relative to longer chain length derivatives, 5000 Da PEG derivatives (37 nm). Direct infusion of the optimized 350 Da PEG derivatives into live tumor-bearing rat brains demonstrated an initial uniform distribution, and hence, the potential for effective brachytherapy applications when the encapsulated Gd(3+) ions are replaced with radioactive (177)Lu.

A randomized comparison of a new flexible bipolar hemostasis forceps designed principally for NOTES versus a conventional surgical laparoscopic bipolar forceps for intra-abdominal vessel sealing in a porcine model.

BACKGROUND: Current devices for hemostasis in flexible endoscopy are inferior to methods used during open or laparoscopic surgery and might be ineffective for natural orifice transluminal endoscopic surgery. OBJECTIVE: To compare new flexible bipolar forceps (FBF), designed principally for natural orifice transluminal endoscopic surgery, with laparoscopic bipolar forceps (LBF) for hemostasis of intra-abdominal porcine arteries. SETTING: Surgical laboratories in Europe and the United States. DESIGN AND INTERVENTIONS: New FBF for hemostasis (3.7-mm diameter), featuring electrode isolation, were compared with rigid 5-mm LBF (ERBE BiClamp LAP forceps) at recommended settings. A porcine model of acute hemostasis was prepared by suturing the uterine horns and cecum to the abdominal wall, exposing uterine arteries, ovarian pedicles, cecal mesenteric bundles, and the inferior mesenteric artery. This allowed access to 10 vessels in each pig by transabdominal laparoscopic devices or a transgastric double-channel gastroscope. Vessels were measured, coagulated at 4 and more points, and transected. Blood pressure was increased to more than 200 mm Hg for 10 minutes by administering phenylephrine. Delayed bleeding was identified. MAIN OUTCOME MEASUREMENTS: In 7 pigs, a total of 65 vessels (1.5-6.0 mm) were randomly allocated to FBF (n = 32) or LBF (n = 33). Successful hemostasis both before and after blood pressure increase was equivalent between the 2 groups (before: 88% FBF vs 88% LBF, not significant [NS]; after: 97% FBF vs 94% LBF, NS). With FBF, the number of seals per vessel was 4.8 vs 4.4 with LBF (NS). The energy used to create FBF seals was 19.8 J vs 38.2 J for LBF (P < .05). LIMITATIONS: Results from porcine studies may not reflect patient outcomes. CONCLUSIONS: In a porcine model, transgastric FBF endoscopic hemostasis was as effective as conventional laparoscopic hemostasis using LBF across a wide range of vessels.

Optimizing bipolar electrocoagulation for endoscopic hemostasis: assessment of factors influencing energy delivery and coagulation.

BACKGROUND: Few data inform decisions on the optimal bipolar electrocoagulation (BPEC) technique. OBJECTIVES: To assess how technical factors influence energy delivery and coagulation. DESIGN: Prospective, randomized study in experimental models: meat, live pig mesenteric arteries. INTERVENTIONS: Standard and prototype BPEC probes were applied at varying durations (2, 10, and 20 seconds), application forces (5, 75, and 150 g), and watt settings (10, 15, and 20 W). BPEC devices were applied to arteries with 40 g versus no additional force. MAIN OUTCOME MEASUREMENTS: For the meat model: energy delivered, impedance, coagulation and cavitation depth, and coagulation surface area. For the mesenteric arteries: hemostasis. RESULTS: The energy delivered increased with duration and force (P < .001) but not with the watt setting. Impedance rose rapidly at higher watt settings (>300 ohms within approximately 5 seconds at 20 W and approximately 10 seconds at 15 W), with a coincident drop in power. Coagulation depth and surface area correlated with energy delivered (r = 0.70-0.97). Only duration was associated with the coagulation depth (P < .001); cavitation (which occurred with a standard BPEC probe) plus coagulation depth was also associated with application force (P < .001). Hemostasis of the mesenteric arteries was achieved only with 40 g of force. LIMITATIONS: The accuracy of these models in predicting clinical results is uncertain. CONCLUSIONS: Increasing BPEC duration increased the energy delivered and the coagulation, whereas increasing the watt setting did not because of a rapid rise in impedance. Optimal BPEC technique included a lower watt setting (eg, 15 W), a longer duration (eg, approximately 10-12 seconds), and tamponade of the bleeding site.

Students with an undisclosed hearing loss: a challenge for academic access, progress, and success?

It has been suggested that only 8% of postsecondary students in the United States who have a hearing loss have disclosed that hearing loss to their institutions. Consistent with this suggestion, two anonymous surveys of students enrolled in courses with the Open University in the United Kingdom suggested that there were roughly 9,000 students in the Open University itself and over 42,000 students in higher education across the United Kingdom as a whole who had a hearing loss that they had not disclosed to their institutions. These students tended to be older people with a relatively mild hearing loss that did not disrupt their communication with other students or their active engagement with learning activities. The impact of the students' hearing loss upon their approaches to studying seemed to be relatively slight, but it was associated with an increase in the students' perceived academic workload.

Academic engagement in students with a hearing loss in distance education.

This investigation compared 267 students with a hearing loss and 178 students with no declared form of disability who were taking courses by distance learning in terms of their scores on an abbreviated version of the Academic Engagement Form. Students with a hearing loss obtained lower scores than students with no disability with regard to communication with other students, but some felt that communication was easier than in a traditional academic situation. Students who were postvocationally deaf had lower scores than students with no disability on learning from other students, but they obtained higher scores on student autonomy and student control. In general, the impact of a hearing loss on engagement in distance education is relatively slight.