EVALUATION OF A TUBULAR MESH AND A SPIRAL STENT WOVEN FROM TITANIUM NICKEL ALLOY FOR PROSTATIC OBSTRUCTION IN PATIENTS AT HIGH RISK FOR SURGERY REPORT OF 62 CASES

The use of two urethral stents woven from titanium nickel alloy (TiNi) in the form of a tubular mesh or a spiral stent (both made in China) is described. They were implanted in 62 patients,vith prostatic outflow obstruction. till patients were considered contraindicated for surgery. They were divided into a spiral stent group (group I) treated between March 1992 and May 1993, comprising 35 cases, and a tubular mesh group (group 2) treated between October 1993 and December 1994, comprising 31 cases, including four failures in group 1. Thirty-three out of the 35 patients in group 1 were treated successfully. Good results were achieved in eight cases (22.8%) and significant improvements occurred in 24 (68.5%), giving a total effective rate of 91.3%, with a follow-up of 11 to 27 months. Fourteen stents were removed within 6 months after the insertion and six more were removed within 12 months. The mean effective time of the stent in situ was 10.8 months. All 31 cases in the mesh group were treated successfully. Dramatically good effects were obtained in 28 cases (over 90%) and distinct improvements were achieved in two, giving a total effective rate of over 96.5%, with a follow-up of 6 to 14 months (mean 10.5 months). Cystoscopy was carried out in 12 patients after 6 months following the insertion. The major part of the meshes became covered by urothelium. Compared with the spiral, the mesh makes it possible to insert a prosthesis with a larger diameter and anti-pressure. The spiral, however, can be used as a temporary alternative for the relief of prostatic obstruction. A tubular mesh can work well for the relief of prostatic obstruction and remain in situ without causing major problems for at least I year.

Arc and Droplet Behaviors in Horizontal Short-Arc Pulsed Gas Metal Arc Welding of 9%Ni Steel with ERNiCrMo-3 Welding Wire

Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur.Short-arc P-GMAW with or without arc length stabilizer was compared.The droplet transfer,arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section.When the arc length stabilizer was deactivated,the arc length was unstable and too short.The droplet transfer mode was mainly short circuit partial transfer,with only a small part of the droplet transferred into the molten pool,with the characteristics of no obvious necking,a few spatters,small droplet impact,long short circuit duration and high short-circuit current.There was also a small proportion of short circuit complete transfer with obvious necking,larger droplet impact,shorter short-circuit duration and lower short-circuit current.With arc length stabilizer,droplet transfer modes were short circuit complete transfer and spray transfer.The spray transfer had the largest droplet impact,no short circuit and no spatter.With the arc length stabilizer activated,a deep penetration,a high penetration ratio,a small reinforcement and a large reinforcement factor were acquired.This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire.