Needle Retraction Research Articles

Ultrasound-guided needle positioning confirmation with injection of saline solution for nodal dynamic contrast-enhanced MR-lymphangiography in pediatric patients.

To assess the success rate of confirmation of ultrasound-guided intranodal needle positioning by saline injection for dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) in pediatric patients. Data from children undergoing nodal DCMRL after ultrasound-guided needle positioning into inguinal lymph nodes and validation of the needle position by injection of plain saline solution between 05/2020 and 12/2022 were reviewed. On injection of saline solution, adequate needle position was confirmed by lymph node distension without leakage. Detection rates and lymph node diameters were recorded. Technical success of needle placement was defined as enhancement of ipsilateral iliac draining lymph vessels on DCMRL, while clinical success was based on enhancement of central lymphatics and/or lymphatic pathologies being observed. One hundred sixteen DCMRLwere performed in 90 children (58 male, mean age 6.1 years, range 3 weeks-18 years). In 232/232 groins lymph nodes were identified on ultrasound with a mean diameter of 2.5 mm (smallest diameter 1 mm in n = 24 patients). Due to skin inflammation, no puncture was performed in 2/232 groins. Saline injection showed lymph node distension in 230/230 punctured nodes. On MR contrast injection enhancement of draining lymph vessels was seen in 228/230 nodes. In 1/230 nodes, in-bore needle retraction led to lymphatic enhancement, so a total of 229/230 needle placements were technically successful. One of the 230 DCMRLs was successful with only a unilateral contrast application. Overall, 116/116 DCMRLs were clinically successful. Confirmation of ultrasound-guided needle positioning for nodal DCMRL using saline injection is a reliable technique with a very high success rate in pediatric patients with small lymph nodes. Question Evaluation of ultrasound-guided injection needle positioning for dynamic contrast-enhanced MR-lymphangiography in children requires validation. Findings Confirmation of needle positioning by ultrasound-guided saline injection is a reliable technique with a very high success rate for MR-lymphangiography in pediatric patients. Clinical relevance Intranodal needle position for dynamic contrast-enhanced lymphangiography can be confirmed with a very high success rate using saline injection alone in a pediatric cohort.

The Survivability of Bacterial Contaminants on a Retracted Stainless-Steel Needle Within a Novel Vascular Access Device

Highlights Abstract Background: Over-the-needle (OTN) peripheral intravenous catheters (PIVCs) are crucial in modern medicine. However, the OTN design allows for direct catheter-to-skin contact during insertion, leaving the sterile catheter at risk for bacterial contamination from the skin. A novel through-the-needle (TTN) PIVC design aims to minimize this risk by shielding the sterile catheter during insertion with the introducer needle. This needle then permanently retracts into the device housing and remains with the patient. In this study, we evaluate the survivability of bacterial contaminants on the retracted needle to address concerns about potential infection risks associated with this design. Methods: Fifteen TTN PIVC devices were inoculated with Staphylococcus aureus (101 to 102 CFU) on the outer surface of the needle. After needle retraction, devices were stored for 0, 24, 72, and 120 hours. At each time point, devices were processed, and bacterial survival was quantified using standard microbiological techniques. Results: The initial bacterial load (105.1 ± 51.4 CFU per device) decreased significantly over time. By 72 hours, bacterial count had reduced to 1.4 ± 2.4 CFU per device, representing a 98.7% reduction (P < 0.05). No significant change was observed between 72 and 120 hours. The most substantial decline occurred within the first 72 hours, with the difference between 0 hours and both 72 and 120 hours being statistically significant (P = 0.016 for both). Conclusions: The significant reduction in bacterial population on the retracted needle over time suggests a low risk of bacterial propagation within the TTN PIVC device. These findings indicate that the TTN design effectively addresses catheter contamination concerns during insertion without introducing additional infection risks due to needle retention.

Enzymatic Digestion of the Intervertebral Disc Alters Intradiscal Injection and Leakage Mechanics.

Intradiscal injection is required to deliver therapeutic agents to the intervertebral disc (IVD) nucleus pulposus (NP). However, injectate leakage following needle retraction may result in decreased treatment efficacy and adverse side effects. While enzymatic digestion is a common research approach for simulating degeneration in healthy animal IVDs, contributions to the leakage phenomenon are unknown. In this study, bovine caudal discs were treated with injection into the NP of either a tris buffer control, collagenase (to primarily target collagen), or trypsin (to primarily target proteoglycans) and then injected with fluorescent saline using a through-puncture defect protocol. Pressure-volume records during injection were used to determine volume and pressure at leakage. Discs were then frozen, transected, and photographed to visualize injectate dispersion. Collagenase treatment resulted in a large increase in injectate dispersion, along with a decrease in injection pressure relative to control. Trypsin treatment resulted in a moderate increase in dispersion, with no associated effect on pressure. This study concludes that care should be taken when employing enzymatic digestion to simulate IVD degeneration, as NP tissue disruption may affect both retention and dispersion of subsequent therapeutic injections.

3D-printed, aptamer-based microneedle sensor arrays using magnetic placement on live rats for pharmacokinetic measurements in interstitial fluid

Molecular monitoring in the dermal interstitial fluid (ISF) is an attractive approach to painlessly screen markers of health and disease status on the go. One promising strategy for accessing ISF involves the use of wearable patches containing microneedle sensor arrays. To date, such microneedle sensors have been fabricated via various manufacturing strategies based on injection molding, machining, and advanced lithography to name a few. Our groups previously reported 3D-printed microneedles as a convenient and scalable approach to sensor fabrication that, when combined with aptamer-based molecular measurements, can support continuous molecular monitoring in ISF. However, the original platform suffered from poor patch stability when deployed on the skin of rodents in vivo. We identified that this problem was due to the rheological properties of the rodent skin, which can contract post microneedle placement, physically pushing the microneedles out of the skin. This sensor retraction caused a loss of electrical contact between working and reference needles, irreversibly damaging the sensors. To address this problem, we report here an innovative approach that allows magnetic placement of microneedle sensor arrays on the skin of live rodents, affixing the patches under light pressure that prevents needle retraction. Using this strategy, we achieved sensor signaling baselines that drift at rates comparable to those seen with other in vivo deployments of electrochemical, aptamer-based sensors. We illustrate real-time pharmacokinetic measurements in live Sprague-Dawley rats using SLA-printed, aptamer-functionalized microneedles and demonstrate their ability to support drift correction via kinetic differential measurements. We also discuss future prospects and challenges.

Ultrasound-guided needle positioning for nodal dynamic contrast-enhanced MR lymphangiography

The aim of the study was to assess injection needle positioning for contrast-enhanced MR-lymphangiography (MRL) by ultrasound-guided injection of saline-solution. 80 patients (33 male, mean age 43.1 years) were referred for MRL. The injection needle position was assessed by injection of saline-solution. Consecutive lymph node distension was observed on sonography followed by MRL. Transpedal MRL was performed when no inguinal lymph nodes could be identified. The inguinal lymph node detection rate was recorded. MR-lymphangiograms were assessed regarding primary (i.e. enhancement of draining lymph vessels) and secondary technical success (i.e. lymph vessel enhancement after repositioning of the needle). MRL was considered as clinically successful if enhancement of the central lymphatic system and/or a lymphatic pathologies were observed. For a total of 92 MRLs 177 groins were evaluated sonographically. In 171/177 groins (96.6%) lymph nodes were identified. After needle placement lymph node distension was observed in 171/171 cases (100%) on saline injection. MR-contrast injection demonstrated enhancement of draining lymph vessels in 163/171 cases (95.3%). In 6/171 cases (3.5%) in-bore needle retraction lead to lymphatic enhancement. In one patient [2/171 nodes (1.1%)] no lymphatic enhancement was seen despite repeated needle repositioning. Overall contrast application was technically successful in 169/171 cases (98.8%). In the 6 groins in which no nodes were identifiable, transpedal MRL was successful. So overall 91/92 MRLs (98.9%) were clinically successful. No complications were recorded. Confirmation of the needle position for nodal MRL by sonographically controlled saline injection is a reliable technique with a high success rate of MRL.

Self-Plugging Microneedle (SPM) for Intravitreal Drug Delivery.

Intravitreal injection (IVI) is a common technology which is used to treat ophthalmic diseases inside eyeballs by delivering various drugs into the vitreous cavity using hypodermic needles. However, in some cases, there are possible side effects such as ocular tissue damage due to repeated injection or eyeball infection through the hole created during the needle retraction process. The best scenario of IVI is a one-time injection of drugs without needle retraction, keeping the system of the eyeball closed. Microneedles (MNs) have been applied to ocular tissues over 10 years, and no serious side effects on ocular tissue due to MN injection have been reported. Therefore, a self-plugging MN (SPM) is developed to perform intraocular drug delivery and to seal the scleral puncture simultaneously. The SPMs are fabricated by a thermal drawing process and then coated with a polymeric carrier of drugs and a hydrogel-based scleral plugging component. Each coated functional layer is characterized and demonstrated by in vitro and ex vivo experiments. Finally, in vivo tests using a porcine model confirms prompt sealing of SPM and sustained intraocular drug delivery.

Establishing a through-puncture model for assessing post-injection leakage in the intervertebral disc.

Needle injection through the outer annulus fibrosus of the intervertebral disc (IVD) is the most practical approach for delivery of therapeutic agents, which have been shown to potentially leak following needle retraction. The goal of this work was to establish a protocol for quantifying post-injection leakage and test its sensitivity to factors believed to affect needle track geometry. A through-puncture defect procedure, followed by controlled injection, was performed on bovine caudal IVDs. Sensitivity to needle size was tested by injection of saline into unconstrained discs with either a 30G, 26G, or 21G hypodermic needle. Sensitivity to axial load was tested by repeated injection via a 26G needle with either no constraint, fixed height, or 10% axial compressive strain. Sensitivity to flexion was tested by applying combined 0.2MPa compression and 15° of flexion following injection of 5% of disc volume. Needle diameter significantly affected maximum volume prior to leakage, ranging from 34.6 ± 31.9µL when using 21G to 115.6 ± 23.6µL when using 30G. While all unloaded discs leaked, axial compression decreased the incidence of leakage events by 50-100% depending on load history. Forward flexion resulted in a 22% incidence of leakage. Fluid injected into IVDs is at significant risk of leakage following needle retraction. This risk depends on factors which alter the geometry of the needle track, including needle size, pinching due to axial compression, and stretching as a result of forward flexion.

PD18-04 UROLIFT AND REZUM: A COMPARISON OF DEVICE RELATED ADVERSE EVENTS IN A NATIONAL REGISTRY

You have accessJournal of UrologyBenign Prostatic Hyperplasia: Surgical Therapy & New Technology III (PD18)1 Sep 2021PD18-04 UROLIFT AND REZUM: A COMPARISON OF DEVICE RELATED ADVERSE EVENTS IN A NATIONAL REGISTRY Elie Kaplan-Marans, James Cochran, Andrew Wood, Elliot Dubowitch, Michael Lee, and Ariel Schulman Elie Kaplan-MaransElie Kaplan-Marans More articles by this author , James CochranJames Cochran More articles by this author , Andrew WoodAndrew Wood More articles by this author , Elliot DubowitchElliot Dubowitch More articles by this author , Michael LeeMichael Lee More articles by this author , and Ariel SchulmanAriel Schulman More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002007.04AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Urolift and Rezum have demonstrated efficacy as minimally invasive surgical therapies (MIST) for the treatment of benign prostatic hyperplasia (BPH). Both modalities can be safely performed in the ambulatory setting and offer superior preservation of sexual function than alternative treatments. Our objective was to describe device malfunctions and complications to help guide procedural selection and performance. METHODS: The Manufacturer and User Facility Device Experience (MAUDE) database was examined for reports related to the use of Urolift and Rezum for the treatment of BPH between January 1, 2015 and July 1, 2020. Reports were evaluated for device malfunctions and surgical complications using a previously described externally validated classification system developed for the MAUDE database. Chi square analysis was used for statistical comparison between groups. RESULTS: A total of 289 adverse events were reported: UroLift (n=132) and Rezum (n=157). The most common UroLift device malfunctions were device misfire (n=27), needle fragmentation (n=21), failed needle retraction (n=6), and misplaced implant (n=5). The most common Rezum device malfunctions were unresolvable error message (n=19), generator failure (n=10), packaging dysfunction (n=8), and failed needle retraction (n=6). As seen in table 1, there were 69 (52%) severe or life threatening adverse events for UroLift vs. 24 (15%) for Rezum (p<0.001). Notable complications included: UroLift (3 laparotomies, 1 arterial embolization, 21 blood transfusions, 13 pelvic or retroperitoneal hematomas, 1 bladder perforation, 1 percutaneous nephrostomy, 1 orchiectomy, 16 implants needing to be removed, 9 implants causing a problem with a later procedure); Rezum (1 blood transfusion, 1 bladder perforation, 3 epididymites, 2 hydrocele infections). CONCLUSIONS: Urolift had more severe adverse event reports in a national registry than Rezum. Many of these events were related to bleeding or to the improper placement or failed deployment of the UroLift implants. Both patients and providers should be aware of potential risks when selecting these novel BPH treatments. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e356-e356 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Elie Kaplan-Marans More articles by this author James Cochran More articles by this author Andrew Wood More articles by this author Elliot Dubowitch More articles by this author Michael Lee More articles by this author Ariel Schulman More articles by this author Expand All Advertisement Loading ...

Pain associated with arteriovenous fistula cannulation: Still a problem

ContextPuncture-related pain during arteriovenous fistula cannulation is a crucial influential factor in the quality of life of chronic hemodialysis patients. Objectives/methodsIn this prospective single center study, we used a questionnaire to evaluate the patterns of pain of arteriovenous fistula cannulation in a group of hemodialysis patients. ResultsFrom a total of 123 eligible patients with arteriovenous fistula invited to participate, 83 (58 M/25 F) (median age 58 y.o.) returned questionnaires. Sixty-five benefitted from an analgesic intervention on cannulation, and 62 found this intervention effective. We evaluated the pain intensity with the échelle visuelle analogique score, the equivalent of Visual Analogue Scale score in French. No specific analgesic intervention (lidocaine patch or cream, vapocoolant spray) was more effective than the others (pNS). 30/65 patients with and 10/18 patients without analgesic intervention reported pain on cannulation (échelle visuelle analogique>1) (pNS). 21/65 patients with and 6/18 patients without analgesic intervention reported pain on needle retraction (pNS). Forty of the 65 patients with analgesic intervention and 11/18 patients without intervention feel stressed before each cannulation. The stress of arteriovenous fistula-related pain is significantly associated with a sensation of pain on cannulation (P=0.047) and needle retraction (P=0.002). ConclusionDespite prophylactic measures for arteriovenous fistula cannulation pain, patients frequently experience stress and unpleasant sensations associated with the procedure.

A Proof-of-Principle Study of the Design and Optimization of a Novel Fluid-Driven Automated Retracting Needle System

Abstract The cannulation of blood vessels is one of the most basic and essential interventions in medical practice. A common adverse event of this procedure is miscannulation with infiltration of the second part of the vessel wall, often resulting in a perivascular hematoma. In hemodialysis patients, surgically created arteriovenous conduits are cannulated 3–4 times per week to provide sufficient blood supply to the hemodialysis machine. However, the high blood flow and pressure in these vascular access sites increase the risk of complications upon miscannulation. A novel needle system that allows for rapid automatic retraction of the needle in response to contact with blood after positioning the cannula in the blood vessel was developed to reduce the risk of miscannulation. The device can easily be incorporated into existing needle designs. The mechanical functionality of the device was validated by testing prototypes in an ex vivo system. Optimization of the needle system was performed to enhance response time and piston shape. A final prototype design was manufactured and validated. The optimal membrane composition and piston shape were determined, which resulted in a needle response time of 40 ms upon contact with fluid at a pressure of 100 mmHg (arterial pressure). Here, we have successfully designed, mechanically validated, and tested a novel automated rapid needle retraction system that allows incorporation into existing needle systems. This device could notably decrease the difficulty of vessel cannulation and the prevalence of hematoma formation.

Slow depressurization following intradiscal injection leads to injectate leakage in a large animal model.

Needle injection has been indicated as the most practical method of delivering therapeutic agents to the intervertebral disc due to the disc's largely avascular nature. As the disc is characterized by both high stiffness and low permeability, injection requires substantial pressure, which may not relax on practical time scales. Additionally, needle puncture results in a localized disruption to the annulus fibrosus that can provide a leakage pathway for pressurized injectate. We hypothesized that intradiscal injection would result in slow relaxation of injectate pressure, followed by leakage upon needle retraction. This hypothesis was tested via controlled injection of fluorescently labeled saline into bovine caudal discs via a 21 gauge needle. Injections were performed with 10% of total disc volume injected at 3%/s followed by a 4‐minute dwell. An analytical poroelastic model was calibrated to the experimental data and used to estimate injectate delivery with time. Experimental results confirmed both pressurization (with a peak of 199 ± 45 kPa) and slow recovery (final pressure of 81 ± 23 kPa). Injectate leakage through the needle puncture was verified following needle retraction in all samples. Histological sections of the discs displayed a clear defect at each disc's injection site with strong fluorescent labeling indicating a leakage pathway. The modeling results suggest that less than one‐fourth of the injected volume was absorbed by the tissue in 4 minutes. Taken together these results suggest that needle injection is a feasible, albeit inefficient method for delivery of therapeutic agents into the intervertebral disc. Particular care should be taken to aspirate un‐absorbed injectate prior to needle retraction to prevent leakage and exposure of surrounding tissues.

A Hand-Held Robot for Precise and Safe PIVC

Peripheral intravenous catheterization (PIVC) is pervasively needed in hospitals. However, given the levels of precision and controllability needed for PIVC, this operation suffers from very low success rates. For young patients, about half of the first insertions fail. Robotic systems have great potential to effectively assist the operation and improve the success rates, which has led to the recent development of different robots to automate PIVC. These robots are equipped with various sensors and actuators, resulting in expensive, complex, and grounded machines. Yet, fully automating the operation is neither needed nor desired, as current clinical preference is oriented toward keeping the practitioner involved and in control of the operation. Therefore, in this study we proposed an innovative smart hand-held robotic device, named CathBot, that enhances intra-operative control during PIVC with automatic features that guarantee very high success rates. It exploits an electrical impedance sensor to detect the venipuncture and a crank-slider mechanism to automate the subsequent cannula advancement and needle retraction. Here, CathBot is first characterized through engineering experiments that demonstrate its capability to successfully perform the whole PIVC operation on a realistic baby arm phantom without human involvement. Subsequent experiments evaluate the device with naive subjects on the same realistic pediatric PIVC scenario. The results demonstrate that CathBot can significantly improve the PIVC performance. Naive subjects achieved an average 86% success rate, and 80% of the subjects succeeded in their first attempt. These results demonstrate the technology has potential to greatly improve both the clinician's and the patient's PIVC experience.

Residual strain effects in needle-induced cavitation.

Needle-induced cavitation (NIC) locally probes the elastic and fracture properties of soft materials, such as gels and biological tissues. Current NIC protocols tend to overestimate properties when compared to traditional techniques. New NIC methods are needed in order to address this issue. NIC measurements consist of two distinct processes, namely (1) the needle insertion process and (2) the cavitation process. The cavitation process is hypothesized to be highly dependent on the initial needle insertion process due to the influence of residual strain below the needle. Retracting the needle before pressurization to a state in which a cylindrical, tube-like fracture is left below the needle tip is experimentally demonstrated to reduce the impact of residual strain on NIC. Verification of the critical cavitation pressure equation in this new geometry is necessary before implementing this retraction NIC protocol. Complementary modeling shows that the change in initial geometry has little effect on the critical cavitation pressure. Together, these measurements demonstrate that needle retraction is a viable experimental protocol for reducing the influence of residual strain, thus enabling the confident measurement of local elastic and fracture properties in soft gels and tissues.

Experimental study on injecting highly viscous liquids by using a reciprocating needle dispensing system

The reciprocating needle dispensing technique is capable of patterning functional inks with a wide range of viscosities. As injections are performed by extruding an ink driven by the reciprocating needle motion, the mechanical specifications and the ink properties are expected to influence the amount of ink conveyed by the needle, thereby affecting the size of drops formed on a substrate. Needle dispensing tests were performed by using Newtonian silicone oils of different viscosities and a pseudoplastic conductive ink with various needle speeds and positions of the needle and the ink reservoir. Time-resolved analysis of the dispensing motions indicated that the formation of the dynamic meniscus around the needle was primarily described by the Landau–Levich–Derjaguin ink-coating theory. However, a slight modification that accounted for the initial gap between the needle and the glass capillary was needed to precisely describe the ink extrusion behaviors. The scaling analysis presented herein provides a perspective for the precise control of drop formation via optimal tuning of the ink injection. Regarding ink filament pinch-off, we discovered that the pseudoplastic liquid exhibited a faster pinch-off at higher needle retraction speed, which is attributed to a reduction of the apparent viscosity due to shear thinning. This behavior is preferable for needle dispensing with better stability.

Survey of US Patients with Multiple Sclerosis: Comparison of the New Electronic Interferon Beta-1b Autoinjector (BETACONNECT™) With Mechanical Autoinjectors.

IntroductionPatients with multiple sclerosis (MS) generally undergo long-term treatment with disease-modifying therapies (DMTs). In the US, patients taking glatiramer acetate, interferon beta-1a, or interferon beta-1b, typically use a mechanical autoinjector. Recent survey results have shown that using an electronic autoinjector, such as BETACONNECT™ (Bayer Pharma AG) for interferon beta-1b/Betaseron® (Bayer Pharma AG) may reduce injection discomfort and increase patient satisfaction with treatment. The aim of the current survey was to assess patient perceptions of BETACONNECT compared with mechanical autoinjectors using a survey integrated with demonstrations and simulated injections with BETACONNECT.MethodsPatients with MS currently using mechanical autoinjectors for glatiramer acetate/Copaxone® (Teva Pharmaceuticals USA, Inc.), interferon beta-1a/Rebif® (EMD Serono Inc.), or interferon beta-1b/Extavia® (Novartis Pharmaceuticals Corp.), participated in a 60-min in-person interview. Patients rated the importance of 18 ideal autoinjector attributes, and the performance of their current autoinjectors across these attributes. BETACONNECT was demonstrated and patients performed simulated injections with BETACONNECT before rating it across the same attributes. Patient overall autoinjector preference was assessed.ResultsNinety patients completed the survey: 63 were using autoinjectors for Copaxone, 25 for Rebif, and 2 for Extavia. BETACONNECT scored higher than mechanical autoinjectors across all 18 attributes. The top attributes of an ideal autoinjector were the injection process is easy overall, easy to push the button to start the injection, and autoinjector is comfortable to hold during injections. Unique BETACONNECT features most valued by patients were the built-in dwell time, self-check function, greater ability to customize injections, adjustment of injection speed, low injection noise, and automatic needle retraction. Overall, 75 out of 90 patients (83%) expressed a preference for BETACONNECT over their current autoinjector.ConclusionBETACONNECT attributes and features were highly rated by patients, compared with both an ideal autoinjector and their current mechanical autoinjectors. These findings suggest that the use of BETACONNECT may increase patient satisfaction and potentially increase overall medication adherence.FundingBayer HealthCare Pharmaceuticals.Electronic supplementary materialThe online version of this article (doi:10.1007/s40120-016-0047-3) contains supplementary material, which is available to authorized users.

153 - Comparison of Biodistribution Following Delivery of Human Skeletal Muscle Derived Cells (hSkMDCs) into Porcine Skeletal Muscle Tissue via Cook® ProFusion™ Therapeutic Infusion Needles and Conventional Hypodermic Needles

The use of stem cell and gene therapies for the treatment of critical limb ischemia (CLI) has shown promising results in clinical settings. While these procedures have conventionally been performed using intramuscular delivery with standard hypodermic needles, recent data suggest that the use of the Cook ProFusion Therapeutic Infusion Needle may allow for the simplification and standardization of the infusion technique, and greater biodistribution of therapeutic agents within the target tissue. In the current study, fluorescently-labeled hSkMDCs were infused into porcine tissue using Cook ProFusion Therapeutic Needles as well as standard hypodermic needles. The primary endpoint was the approximate biodistribution of hSkMDCs in porcine skeletal muscle. For the hypodermic needles, infusion occurred simultaneously with needle retraction, simulating conventional clinical use, with an aim to improve biodistribution. No such retraction was necessary with the ProFusion needles due to the sideported infusion segment located at the distal 1 cm of the device (Figure 1). Following cell infusions, injected tissue was collected and fluorescently imaged using an IVIS Lumina System (Figure 2). Results suggest that the use of Cook ProFusion needles allow for greater biodistribution of therapeutic agents when compared to conventional hypodermic needles and delivery techniques. Figure 2 View Large Image Figure Viewer

In vivo evaluation of needle force and friction stress during insertion at varying insertion speed into the brain.

Convection enhanced delivery (CED) infuses drugs directly into brain tissue. Needle insertion is required and results in tissue damage which can promote flowback along the needle track and improper targeting. The goal of this study was to evaluate friction stress (calculated from needle insertion force) as a measure of tissue contact and damage during needle insertion for varying insertion speeds. Forces and surface dimpling during needle insertion were measured in rat brain in vivo. Needle retraction forces were used to calculate friction stresses. These measures were compared to track damage from a previous study. Differences between brain tissues and soft hydrogels were evaluated for varying insertion speeds: 0.2, 2, and 10mm/s. In brain tissue, average insertion force and surface dimpling increased with increasing insertion speed. Average friction stress along the needle-tissue interface decreased with insertion speed (from 0.58 ± 0.27 to 0.16 ± 0.08 kPa). Friction stress varied between brain regions: cortex (0.227 ± 0.27 kPa), external capsule (0.222 ± 0.19 kPa), and CPu (0.383 ± 0.30 kPa). Hydrogels exhibited opposite trends for dimpling and friction stress with insertion speed. Previously, increasing needle damage with insertion speed has been measured with histological methods. Friction stress appears to decrease with increasing tissue damage and decreasing tissue contact, providing the potential for in vivo and real time evaluation along the needle track. Force derived friction stress decreased with increasing insertion speed and was smaller within white matter regions. Hydrogels exhibited opposite trends to brain tissue.

Effect of needle insertion speed on tissue injury, stress, and backflow distribution for convection-enhanced delivery in the rat brain.

Flow back along a needle track (backflow) can be a problem during direct infusion, e.g. convection-enhanced delivery (CED), of drugs into soft tissues such as brain. In this study, the effect of needle insertion speed on local tissue injury and backflow was evaluated in vivo in the rat brain. Needles were introduced at three insertion speeds (0.2, 2, and 10 mm/s) followed by CED of Evans blue albumin (EBA) tracer. Holes left in tissue slices were used to reconstruct penetration damage. These measurements were also input into a hyperelastic model to estimate radial stress at the needle-tissue interface (pre-stress) before infusion. Fast insertion speeds were found to produce more tissue bleeding and disruption; average hole area at 10 mm/s was 1.87-fold the area at 0.2 mm/s. Hole measurements also differed at two fixation time points after needle retraction, 10 and 25 min, indicating that pre-stresses are influenced by time-dependent tissue swelling. Calculated pre-stresses were compressive (0 to 485 Pa) and varied along the length of the needle with smaller average values within white matter (116 Pa) than gray matter (301 Pa) regions. Average pre-stress at 0.2 mm/s (351.7 Pa) was calculated to be 1.46-fold the value at 10 mm/s. For CED backflow experiments (0.5, 1, and 2 µL/min), measured EBA backflow increased as much as 2.46-fold between 10 and 0.2 mm/s insertion speeds. Thus, insertion rate-dependent damage and changes in pre-stress were found to directly contribute to the extent of backflow, with slower insertion resulting in less damage and improved targeting.

WE‐A‐BRB‐01: Robotic Brachytherapy Demonstration: Implant of HDR Brachytherapy Needle Configuration Computer‐Optimized to Avoid Critical Structures Near the Bulb of the Penis

Purpose: To develop a robotic system to implant high dose rate brachytherapy (HDR‐BT) needle configurations meeting clinical dose objectives while avoiding puncture of non‐target structures. This system consists of (1) a robotic needle insertion device, (2) needle and dose planning software, and (3) a human with no clinical experience. Methods: Acubot‐RND is a joy‐stick controlled 7‐DoF stereotactic needle insertion robot with a remote center of motion (RCM) allowing needle pivot around the RCM point. For this project, a digital needle coordinate input and execution system was developed to replace the analog joy‐stick control. Custom pelvic phantoms were built, CT imaged, and contoured. A custom needle‐geometry optimization engine was used to generate a planned needle configuration (PNC) within the robot workspace and tailored to the phantom anatomy. Configurations of parallel and angulated needles (up to 53 deg. from parallel) were instructed to avoid puncture of the critical structures near the penile bulb (CSNB). The PNC was transferred to Acubot for sequential insertion. After each insertion, the robot released the needle in place. Needle stylets were passed through the needle and deposited in the phantom during needle retraction by the human user making the implanted needle configuration (INC). Results: Two phantoms were implanted using the robotic system. Post‐implant CT were obtained, puncture avoidance of the CSNB, pubic arch, and urethra confirmed, and the INC digitized for treatment plan generation. Satisfaction of RTOG‐0321 clinical dose objectives was verified and quantitatively compared against a phantom implant performed by an experienced physician. Conclusions: A clinically‐ relevant robotic brachytherapy workflow able to avoid the CSNB and guide needles behind the pubic arch while meeting clinical dose requirements was demonstrated. Operation of this system mitigates some reliance on brachytherapy implant expertise. This workflow is valid for both PPI and HDR‐BT. Supported by American Cancer Society Grant #IRG‐97‐150‐13.

Infusion pressure and pain during microneedle injection into skin of human subjects

Infusion into skin using hollow microneedles offers an attractive alternative to hypodermic needle injections. However, the fluid mechanics and pain associated with injection into skin using a microneedle have not been studied in detail before. Here, we report on the effect of microneedle insertion depth into skin, partial needle retraction, fluid infusion flow rate and the co-administration of hyaluronidase on infusion pressure during microneedle-based saline infusion, as well as on associated pain in human subjects. Infusion of up to a few hundred microliters of fluid required pressures of a few hundred mmHg, caused little to no pain, and showed weak dependence on infusion parameters. Infusion of larger volumes up to 1 mL required pressures up to a few thousand mmHg, but still usually caused little pain. In general, injection of larger volumes of fluid required larger pressures and application of larger pressures caused more pain, although other experimental parameters also played a significant role. Among the intradermal microneedle groups, microneedle length had little effect; microneedle retraction lowered infusion pressure but increased pain; lower flow rate reduced infusion pressure and kept pain low; and use of hyaluronidase also lowered infusion pressure and kept pain low. We conclude that microneedles offer a simple method to infuse fluid into the skin that can be carried out with little to no pain.