Regardless of the Puncture Angle, a Tuohy Needle with Sand-Blasted Steel at the Tip of the Bevel Is a Valid Needle on the Ultrasonic Images

Background: A high ability to visualize the needle on the ultrasonic images is necessary to perform the ultrasound-guided nerve block safely. The Rafa Tuohy needleR (Vygon, Paris, France, Rafa) is a non-stimulating Tuohy needle with sand-blasted steel at the tip of the bevel. We examined the degree to which the Rafa enhanced the visibility of ultrasonic images compared with the non-coated Tuohy needle. Methods: We punctured the Blue Phantom. The dimensions of both the Rafa and the non-coated Tuohy needles were 18 G × 80 mm. The puncture angle is 30 degrees and 45 degrees from the Blue Phantom. We measured the intensity of the tip of the bevel at a depth of 0.5, 1.0, 1.5 and 2.0 cm for the puncture angle of 30 degrees, and 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm for the puncture angle of 45 degrees. Six anesthesiologists with more than seven years of experience performed three punctures using each needle. Results: As an outcome, we concluded that at a puncture angle of both 30 degrees and 45 degrees, the intensity of the non-coated Tuohy needle decreased with the depth. On the other hand, at an angle of 30 degrees, the intensity of the Rafa needle did not decrease, and at an angle of 45 degrees the intensity only decreased very slightly as the depth increased. Conclusions: The Tuohy needle with sand-blasted steel at the tip of the bevel provided greater visualization than the non-coated Tuohy needle on the ultrasound images.

Plasma Nitriding-Assisted Printing of Stainless Steel Punches for Micro-piercing Process

MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.