Investigation of the Pulsing Characteristic of a Carbon Nanotube Emitter.

The carbon nanotube (CNT) field emitter is suitable for the high frequency pulsing of X-ray. Pulsing reduces 49% of the dose in grid-controlled fluoroscopy and improves the image of moving objects. Various structures and manufacturing processes are being studied. However, more studies on the dynamic characteristic of a pulsing CNT and its application are needed. In this study, the combined dynamics including the field emission, MOSFET, and modified gate driver for MOSFET have been analyzed. In this configuration, between the cathode of the tube and ground, there is a MOSFET switch that turns the tube current on/off and a shunt resistor that measures the tube current. Due to the high impedance of the vacuum between the gate and cathode of the tube, about 85% of the gate voltage is still exerted between the Gate and cathode of the tube during the off-state of the MOSFET. Therefore, space charges are built during the off-state and then released at the beginning of the on-state of the MOSFET. The modified gate driver structure for MOSFET that we propose in this paper can limit the amount of current flow through the cathode. Tube current (boosted current) can be accurately controlled through a modified gate driver structure. Combining the boosted current and pulse control of MOSFET, the dynamic current performance of a CNT tube can be enhanced and the average tube current or dose can be accurately controlled. Experiments, simulation, and analysis have been conducted to study the combined dynamics and its applications.

Use of Tuohy needle for intraamniotic methotrexate injection through the cervical canal in a cervical pregnancy after failure of systemic methotrexate treatment.

A case of cervical pregnancy resistant to systemic methotrexate (MTX) administration is presented. A 41 year old patient with cervical pregnancy at 6 weeks 4 days' gestation was successfully treated by intraamniotic MTX injection through the cervical canal using Tuohy needle after failure of systemic MTX treatment.

Treatment with piroxicam before embryo transfer increases the pregnancy rate after in vitro fertilization and embryo transfer.

OBJECTIVE: To examine the effect of beta-cyclodextrin piroxicam treatment for priming of the uterus on the pregnancy outcome of IVF-embryo transfer (ET) programs. DESIGN: Prospective, randomized, double-blinded placebo-controlled clinical study. SETTING: Large urban medical center. PATIENT(S): One hundred eighty-eight consecutive cycles of fresh IVF-ET and 78 cycles of frozen-thawed ET. The patients underwent IVF because of tubal, male infertility, unexplained, or endometriosis factors. They were randomly divided into treatment and control groups. INTERVENTION(S): In the treatment group, 94 cycles in fresh ET and 39 cycles in frozen-thawed ET the patients received an oral dose of 10 mg of piroxicam. In the control group, the same number cycles corresponding to the treatment group were treated with placebo. Both groups started piroxicam or placebo treatment 1-2 hours before ET. Patients and staff were blinded to the treatment. MAIN OUTCOME MEASURE(S): Implantation rate (IR) and pregnancy rate (PR). RESULT(S): Piroxicam increased significantly IR (18.7%) and PR (46.8%) compared to the control group (8.6% and 27.6%, respectively) in fresh cycles. With the exception of an unexplained factor, patients with the tubal, male infertility, or endometriosis factor had significantly higher PR in the treatment group compared to the control group. The beneficial effect of piroxicam was found in patients less than 40 years old, but was not found in patients more than 40 years. In frozen-thawed cycles, there were statistically significant differences between the treatment group and the control group in IR (9.4% vs. 2.3%) and PR (25.6% vs. 7.7%), respectively. CONCLUSION(S): Our study showed that piroxicam increases IR and PR after IVF-ET in both fresh and frozen-thawed ET cycles. The beneficial effect seems to be more remarkable in patients less than 40 years old with tubal, male infertility, or endometriosis factors. These results suggest that piroxicam treatment before ET is very effective in the priming of a uterus suitable for embryo implantation. This is the first study to investigate the possible consequence of piroxicam for improving the PR after IVF-ET.

Short coasting of 1 or 2 days by withholding both gonadotropins and gonadotropin-releasing hormone agonist prevents ovarian hyperstimulation syndrome without compromising the outcome.

OBJECTIVE: To evaluate the effect of short coasting, by withdrawing both gonadotropins and gonadotropin-releasing hormone (GnRH) agonist, on the prevention of severe ovarian hyperstimulation syndrome (OHSS) without compromising pregnancy outcome. DESIGN: Retrospective study. SETTING: Large urban medical center. PATIENT(S): Forty-four women who had been coasted during controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF). INTERVENTION(S): When >or=20 follicles >15 mm with serum estradiol (E(2)) level of 4000 pg/mL were detected, both gonadotropins and GnRH agonist were withheld for 1 to 2 days. MAIN OUTCOME MEASURE(S): Changes of serum E(2) levels, number of oocytes retrieved, pregnancy rate. RESULT(S): The mean serum E(2) level fell from 7915 pg/mL at the onset of coasting to 3908 pg/mL on the day of human chorionic gonadotropin (hCG) administration. The mean number of oocytes retrieved and fertilization rate were 17.2% and 75.0%, respectively. Eighteen patients became pregnant (43.9%), and the implantation rate was 12.7%. Twenty-eight patients were coasted for 1 day, and 13 were coasted for 2 days. The mean decrease rate of serum E(2) level was 45.3% in 1-day coasting and 26.4% (first day) and 75.3% (second day) in 2-day coasting. The pregnancy outcome was similar between both groups. After coasting, three mild and two severe cases of OHSS occurred. CONCLUSION(S): Coasting for 1 or 2 days can be used successfully to prevent OHSS without compromising IVF cycle outcome.