The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. The production of Ac-225 has been achieved using bremsstrahlung photons from an 18 MV medical linear accelerator (linac) to bombard a Ra-226 target. A linac dose of 2800 Gy produced about 64 microCi of Ra-225, which decays to Ac-225. This result, while consistent with the theoretical calculations, is far too low to be of practical use. A more powerful linac is required that runs at a higher current, longer pulse length and higher frequency for practical production. This process could also lead to the reduction of the nuclear waste product Ra-226. 相似文献
This study reports on the development of a model for studying skeletal muscle metabolism in humans using NMR spectroscopy. Graded exercise was simulated using electrical stimulation in 10 healthy, fit subjects (mean VO2max = 53 +/- 4 ml.kg-1.min-1). The effects of varying the stimulation parameters, namely, the stimulation frequency, the stimulation intensity, and the duty cycle, as well as the spectral interrogation volume, were compared using data acquired from the rectus femoris muscle. With stimulation, the inorganic phosphate to phosphocreatine concentration ratio ([P(i)]/[PCr]) and the intracellular pH both follow curvilinear relationships over the stimulation frequencies from 3 to 30 Hz, with the magnitude of the observed change related closely to stimulation intensity and duty cycle. Oxidative phosphorylation predominates at stimulation frequencies below 12 Hz, while anaerobic metabolism increases sharply above 12 Hz. Our findings show clearly the interdependence of the effects of the various stimulation parameters and emphasize the care that must be exercised in interpreting the physiological significance of the biochemical data obtained from electrical stimulation models used to study skeletal muscle metabolism. 相似文献
During the development of a silicone rubber implant for the delivery of estradiol 17-beta some batches of implants made from a certain lot of commercial estradiol inexplicably developed surface crystals of estradiol after several days of storage. An impurity profile was obtained for 28 lots of estradiol by a newly developed HPLC method. One or more impurities may have had a role in the spontaneous crystal growth on the surface of the implants, because the one lot of estradiol that initially had surface crystals on aging produced acceptable implants after multiple recrystallizations. Attempts to isolate suspected impurities for characterization were unsuccessful. During the manufacture of the implants, temperatures sufficient to melt the estradiol (mp, 173-179 degrees C) were used. It was expected that, upon implant cooling, melted impure estradiol would form a thermodynamically more active (i.e., noncrystalline) physical form. This metastable form could have migrated to the implant surface, where ambient conditions favored crystallization. Because melted estradiol of a higher purity tended to crystallize more readily, it was less likely to form a glass upon cooling. The phenomenon of surface crystallization was limited to one lot of estradiol with the highest level of impurities. Data from differential scanning calorimetry studies supported this conclusion. 相似文献
Summary Placement of feeding tubes is a common procedure for general surgeons. While the advent of percutaneous endoscopic gastrostomy
has changed and improved surgical practice, this technique is contraindicated in many circumstances. In some patients placement
of feeding tubes in the stomach may be contraindicated due to the risks of aspiration, gastric paresis, or gastric dysmotility.
We describe a technique of laparoscopic jejunostomy tube placement which is easy and effective. It is noteworthy that this
method may be used in patients who have had previous abdominal operations, and it has the added advantage of a direct peritoneal
view of the viscera. We suggest that qualified laparoscopic surgeons learn the technique of laparoscopic jejunostomy. 相似文献
Background: Small doses of bupivacaine may be a reasonable choice for spinal anesthesia for patients having ambulatory surgery. However, few dose-response data are available to guide the selection of reasonable doses of bupivacaine for different ambulatory procedures.
Methods: Eight volunteers per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind manner. Sensory block was assessed with pinprick, transcutaneous electrical stimulation equivalent to surgical incision at the ankle, knee, pubis, and umbilicus, and with duration of tolerance to pneumatic thigh tourniquet. Motor block at the quadriceps and gastrocnemius muscles was assessed with isometric force dynamometry. Times until recovery from spinal anesthesia were recorded. Dose-response relationships were determined by linear regressions. Mean (95% confidence intervals) for durations of sensory and motor block per milligram of bupivacaine administered were calculated from linear regressions.
Results: Significant dose-response relationships (P < 0.006) were determined for sensory block, motor block, and time until recovery (R from 0.6 to 0.9). Within the range of doses studied, each additional milligram of bupivacaine was associated with an increase in duration of tolerance to transcutaneous electrical stimulation of 10 (7 to 13) min, an increase in tolerance to tourniquet of 7 (2 to 11) min, an increase in duration of motor block of 8 (5 to 12) min, and an increase in time until recovery of 21 (17 to 25) min. 相似文献
The natural history of spinal deformities in the cerebral palsy patient is different than that in the idiopathic patient. Consequently, the approach to the patient with cerebral palsy and the surgical decision-making are different from that in the idiopathic patient. The present article gives the UTMB approach to the treatment of the cerebral palsy patient and the unique considerations that must be taken into account when treating these patients. Specific references are made to the use of L-rod instrumentation to stabilize the spinal deformity in the cerebral palsy patient. 相似文献
Over the 3-year period from Jan. 1, 1986, through Dec. 31, 1988, we have implanted 101 automatic implantable cardioverter-defibrillators into patients with life-threatening ventricular arrhythmias. There were 82 male patients and 19 female patients. The mean age was 58 years with a range of 25 to 82 years. The indication for implantation was ventricular fibrillation in 89 patients and recurrent ventricular tachycardia in 12 patients. Seventy-seven patients had a history of prior myocardial infarction or coronary artery disease, or both. Eighteen patients had nonischemic cardiomyopathy. One patient had a prolonged QT syndrome and five patients had no evidence of preexisting structural heart disease. The mean injection fraction was 37% +/- 17%. Forty-one of the automatic implantable cardioverter-defibrillator implantations were associated with procedures necessitating cardiopulmonary bypass. The hospital mortality rate was 4% and the morbidity rate was 15%. The only statistical difference between those patients who did and did not have postoperative complications was a history of a prior myocardial infarction (90% versus 54%, p less than 0.05). Twenty percent of patients had new-onset postoperative atrial fibrillation after implantation of the device. Eleven percent of patients had sustained ventricular tachycardia postoperatively. Although there was a trend toward a higher complication/death rate in the patients whose automatic implantable cardioverter-defibrillator was inserted in association with cardiopulmonary bypass (24% versus 15%) and the occurrence of new-onset postoperative atrial fibrillation (27% versus 15%), these findings were not statistically significant. Automatic implantable cardioverter-defibrillator implantation with and without concomitant cardiopulmonary bypass is associated with a clinically important morbidity and mortality rate and development of postoperative arrhythmias. 相似文献