Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Paediatric dacryocystorhinostomy

Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease.     

Hematologic changes during and after cardiopulmonary bypass and their relationship to the bleeding time and nonsurgical blood loss.

The hemostatic dysfunction induced by cardiopulmonary bypass is due, in part, to a platelet dysfunction evidenced by a postoperative extension of the bleeding time; it leads to increased postoperative blood loss and morbidity. This study, which was conducted in 85 patients undergoing cardiopulmonary bypass, was designed to characterize the hematologic changes during and after cardiopulmonary bypass and to elucidate the relationships between these changes, the extension of the bleeding time, and the magnitude of the postoperative nonsurgical blood loss. Variables were measured before, during, and 2, 24, 48, and 72 hours after cardiopulmonary bypass. Univariate and multivariate analyses were performed with either the 2-hour postbypass bleeding time or the 4-hour postbypass blood loss as the dependent variables. The reversal of the extension of the bleeding time in the postoperative period was accompanied by a significant increase in the mean platelet volume and by a significant increase in the level of thromboxane B2 measured in the blood shed from the site of the bleeding time determination. The postoperative bleeding time correlated with the postoperative blood loss, and both parameters were dependent on the duration of cardiopulmonary bypass. In addition, the postoperative bleeding time correlated with the skin temperature and the plasma level of D-dimer, while the postoperative blood loss also correlated with temperature and the plasma levels of C3. These data establish a direct relationship between the postoperative bleeding time, the postoperative blood loss, and temperature. They indicate that the reversal of the postoperative extension of the bleeding time is due in part to rewarming and to the release of larger platelets into the circulation, and they suggest that hyperfibrinolysis and complement activation may play an important role in the cardiopulmonary bypass-induced platelet dysfunction.     

Molecular-weight distribution in the activated-monomer polymerization of ethylene oxide. Mechanistic implications

The mechanism of the activated-monomer polymerization of ethylene oxide catalyzed by protic acids was investigated by means of an analysis of the molecular-weight distribution curves from the polymers obtained. The results suggest that polymer ether groups participate in the polymerization by forming hydrogen-bonded complexes and tertiary oxonium cations in the reaction with the activated monomer, both being intermediates of the propagation reactions.     

Solid-phase radioimmunoassay for the detection of rotavirus.

A solid-phase radioimmunoassay method has been developed for the detection of rotavirus in the form of a purified antigen and in stool. The parameters of the radioimmunoassay were examined and optimized to give high sensitivity and same-day results. Compared with electron microscopy, the assay is up to 10 times as sensitive for detection of the virus in stool and up to 128 times as sensitive for detection of a purified virus antigen. In a field study on stool specimens it was at least as efficient as electron microscopy.