Controllability Over Wall Thickness of Tubular Structures and Encapsulation During Co-Axial Extrusion of a Thermal-Crosslinking Hydrogel

Tubular structures of the hydrogel are used in a variety of applications such as delivering nutrient supplies for 3D cell culturing. The wall thickness of the tube determines the delivery rate. In this study, we used the coaxial extrusion process to fabricate tubular structures with varying wall thicknesses using a thermal-crosslinking hydrogel, gellan gum (GG). The objectives of this study are to investigate the thermal extrusion process of GG to form tubular structures, the range of achievable wall thickness, and a possibility to form tubular structures with closed ends to encapsulate fluid or drug inside the tube. The wall thickness is controlled by changing the relative flow velocity of the inner needle (phosphate-buffered saline, PBS) to the outer needle, while keeping the velocity of outer needles (GG) constant. Two pairs of coaxial needles were used which are 18-12 gauge (G) and 20-12G. The controllable wall thickness ranges from 0.618 mm (100% relative velocity) to 0.499 mm (250%) for 18-12G and from 0.77 mm (80%) to 0.69 (200%) for 20-12G. Encapsulation is possible in a smaller range of flow velocities in both needle combinations. A finite element model was developed to estimate the temperature distribution and the wall thickness. The model is found to be accurate. The dynamic viscosity of GG determines the pressure equilibrium and the range of achievable wall thickness. Changing the inner needle size or the flow velocity both affect the heat exchange and thus the temperature-dependent dynamic viscosity.

Intraoperative use of cone-beam computed tomography for the safe epidural blood patch: Technical case report

Background: Epidural blood patch (EBP) is a common method utilized to treat intracranial hypotension, and secondarily, to treat unintentional dural puncture. The authors propose an effective technique for correct epidural needle positioning during EBP using cone-beam computed tomography (CB-CT) images. Case Description: A 31-year-old female underwent an EBP. Following confirmation of the spinal level of the cerebrospinal fluid leakage, the ideal trajectory for the proposed EBP was assessed from the entry point on the skin to the spinolaminar line under CB-CT imaging. The epidural needle was then gently advanced along the appropriate trajectory. At the 10 mm mark, behind the spinolaminar line, the inner needle was removed. This allowed for slow advancement of the outer needle until its tip reached the epidural space, and its location was confirmed by the “loss of resistance to the saline technique.” Using biplane epidurography, the spread of dye within the epidural space for appropriate localization was confirmed. In this case study, the patient’s postural headache immediately improved. Conclusion: Using the CB-CT technique described, a patient successfully underwent EBP without complications.

New strategy for firm ventricular wall tap

We report the effectiveness of a new strategy for ventricular cannulation that allows for easy insertion into the firm ventricular wall.The new ventricular needle consisting of an outer needle, a dull inner needle, and a sharp inner needle was used for a firm ventricular wall tap in five patients. The dull inner needle was used for the brain mantle tap, whereas the sharp needle was used for penetrating the ventricular wall. The outer needle with the insertion of the dull inner needle was set for initial puncture. If the operator felt that the ventricular wall was firm or confirmed that the tip of the cannula indented the wall of the ventricle using real-time ultrasound monitoring before penetrating the ventricle wall, then the inner needle was changed to the sharp one to penetrate the ventricular wall. After confirming that the trajectory was now passing into the ventricle, the ventricular catheter was placed using the trajectory.There was no perioperative complication associated with insertion of the device. All catheters were inserted with a single pass through the brain mantle.The new ventricular tap strategy is safe and effective for firm ventricular wall tap and ventricular catheter insertions.

Development of a shape memory alloy multiple-point injector for chemotherapy

A medical needle is described that allows injection to take place at multiple sites through a single stab wound. This is achieved by extruding multiple, thin, and curved internal needles from a larger, straight, outer needle. The development and finite element modelling of the shape memory alloy (SMA) inner needles is presented in this paper. A non-linear elastic element model was used in this process to allow for the non-linear properties of the alloy and the large deformations that occur. The model provided maximum strain values and penetration forces for the inner needles. The deformation force on the tip of the needle was measured against displacement to confirm the predicted penetration force. Applications for the device include the treatment of liver cancer by direct injection of alcohol into the tumours.