Needle Configuration Research Articles

Modelling and characterisation of a ultrasound-actuated needle for improved visibility in ultrasound-guided regional anaesthesia and tissue biopsy

Clear needle visualisation is recognised as an unmet need for ultrasound guided percutaneous needle procedures including regional anaesthesia and tissue biopsy. With inadequate needle visibility, these procedures may result in serious complications or a failed operation. This paper reports analysis of the modal behaviour of a previously proposed ultrasound-actuated needle configuration, which may overcome this problem by improving needle visibility in colour Doppler imaging. It uses a piezoelectric transducer to actuate longitudinal resonant modes in needles (outer diameter 0.8–1.2mm, length>65mm). The factors that affect the needle’s vibration mode are identified, including the needle length, the transducer’s resonance frequency and the gripping position. Their effects are investigated using finite element modelling, with the conclusions validated experimentally. The actuated needle was inserted into porcine tissue up to 30mm depth and its visibility was observed under colour Doppler imaging. The piezoelectric transducer is able to generate longitudinal vibration with peak-to-peak amplitude up to 4μm at the needle tip with an actuating voltage of 20Vpp. Actuated in longitudinal vibration modes (distal mode at 27.6kHz and transducer mode at 42.2kHz) with a drive amplitude of 12–14Vpp, a 120mm needle is delineated as a coloured line in colour Doppler images, with both needle tip and shaft visualised. The improved needle visibility is maintained while the needle is advanced into the tissue, thus allowing tracking of the needle position in real time. Moreover, the needle tip is highlighted by strong coloured artefacts around the actuated needle generated by its flexural vibration. A limitation of the technique is that the transducer mode requires needles of specific lengths so that the needle’s resonance frequency matches the transducer. This may restrict the choice of needle lengths in clinical applications.

Intraoperative Adductor Canal Block for Augmentation of Periarticular Injection in Total Knee Arthroplasty: A Cadaveric Study

BackgroundFunction is often sacrificed for pain control after total knee arthroplasty. Motor-sparing blocks, including adductor canal block (ACB) and periarticular injection (PAI), have gained interest to address this compromise. Our study evaluates the anatomic feasibility, accuracy, and safety of intraoperative ACB as an adjunct to PAI by analyzing 3 different injection orientations and needle configurations. MethodsEleven cadaveric knees underwent a standard medial parapatellar arthrotomy. Blunt dissection through the suprapatellar recess was performed. Using a 10-mL syringe, various colors of dyed liquid gelatin were injected toward the proximal and distal adductor canal (AC) using 3 needle configurations. Medial dissection of the knee for each specimen was performed. The position of each needle and location of injected dye was identified and described relative to the AC. ResultsAccuracy of each injection orientation and/or needle configuration was different: 86% for a blunt needle in the distal AC, 57% for blunt needle in the proximal AC, and 14% for a spinal needle in the proximal AC. Puncture of the femoral artery was observed with the spinal needle 43% of the time and had the closest average proximity to the femoral artery with a distance of 5.9 mm. There were no vascular punctures using blunt needles, and the average distance from the femoral artery with proximal and distal orientation was 10.2 mm and 15.4 mm, respectively. ConclusionIntraoperative ACB augmentation of PAI appears to be anatomically feasible and safe. There was decreased accuracy and increased risk of vascular puncture using a 3.5-inch spinal needle. A blunt 1.5-inch needle directed toward the distal AC had the highest accuracy while minimizing vascular injury.

The effect of the plasma needle on the human keratinocytes related to the wound healing process

In the present study we aim to verify the influence of a non-thermal atmospheric pressure plasma on the wound healing process. In this process the major contributors are the keratinocytes, which migrate to fill in the gap created by the wound. Therefore, we performed the direct treatment of HPV-immortalized human keratinocytes, protected by a layer of phosphate buffered saline (PBS) solution, with the glow discharge generated in flowing helium by a plasma needle. To mimick a wound, a 4 mm scratch was performed on the cell culture (scratch assay). We conducted two types of experiments: (i) cell proliferation and (ii) wound-healing model experiments. The plasma needle configuration, the plasma treatment conditions and the thickness of the protecting PBS layer were set based on viability experiments. The proliferation studies showed that short, 5–10 s, and low power treatments, such as 18 W and 20 W input power, could positively influence the cell proliferation when keratinocytes were protected by PBS. On the other hand, the plasma treatment of cell medium covered keratinocytes resulted in the decrease of proliferation. The wound-healing model (scratch assay) studies showed, that there was a maximum in the wound reduction as a function of the input power and treatment time, namely, at 18 W and 5 s. Furthermore, the wound reduction strongly depended on the treated cell—PBS interaction time. To mimic an infected wound, the scratch assay was covered with a cfu ml−1 Propionibacterium acnes suspension. The plasma treatment of this infected assay resulted in closing of the scratch, while in the non-treated assay the wound did not close at all.

Optical Flow-Based Tracking of Needles and Needle-Tip Localization Using Circular Hough Transform in Ultrasound Images.

Image-guided interventions have become the standard of care for needle-based procedures. The success of the image-guided procedures depends on the ability to precisely locate and track the needle. This work is primarily focused on 2D ultrasound-based tracking of a hollow needle (cannula) that is composed of straight segments connected by shape memory alloy actuators. An in-plane tracking algorithm based on optical flow was proposed to track the cannula configuration in real-time. Optical flow is a robust tracking algorithm that can easily run on a CPU. However, the algorithm does not perform well when it is applied to the ultrasound images directly due to the intensity variation in the images. The method presented in this work enables using the optical flow algorithm on ultrasound images to track features of the needle. By taking advantage of the bevel tip, Circular Hough transform was used to accurately locate the needle tip when the imaging is out-of-plane. Through experiments inside tissue phantom and ex-vivo experiments in bovine kidney, the success of the proposed tracking methods were demonstrated. Using the methods presented in this work, quantitative information about the needle configuration is obtained in real-time which is crucial for generating control inputs for the needle and automating the needle insertion.

Reliable Peeling of Ultrathin Die With Multineedle Ejector

Flip chip packaging as a mainstream packaging interconnect technology has proliferated rapidly within the last decade or so. With the applications of high-performance chip, its thickness and size have been much thinner and bigger, which is challenging the current assembly technique, especially for the reliable peeling of ultrathin die from the wafer due to its vulnerability and flexibility. Here, we present some significant analytical formulas to estimate die cracking stress and peeling energy in die peeling process. The effects of two factors, including peeling cracking propagation and ejecting needle configuration, are investigated using a fracture mechanics framework. Meanwhile, all analytical predictions have been verified via finite element modeling with virtual crack technique. Theoretical results have shown that die cracking stress could be effectively reduced, but it rarely works to improve peeling energy when more needles are embedded below the adhesive tape. In particular, the essence of the technique with the multi-needle is discussed, compared with the normal single-needle technique, which can be used to guide the design of ultrathin die peeling process.

Surface Coating of Bonded PDMS Microchannels by Atmospheric Pressure Microplasma

The surface coating of sealed microchannels is useful for a variety of applications in microfluidics and lab-on-a-chip devices. This paper demonstrates a novel coating technique for a bonded polydimethylsiloxane (PDMS) microchannel using atmospheric pressure microplasma. Plasma was generated by using two types of electrode arrangements: (i) needle–aluminum foil with dielectric barrier (DB) and (ii) needle–needle configuration without DB. The microplasma configuration with the DB was selected for deposition in this study. The monomer ethylenediamine was used as organic precursor for plasma polymerization. Oil-in-water microemulsions were formed in a T-shaped microchannel in order to test the stability and durability of the plasma polymerized films. The coatings were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements.

NPIP: A skew line needle configuration optimization system for HDR brachytherapy

In this study, the authors introduce skew line needle configurations for high dose rate (HDR) brachytherapy and needle planning by integer program (NPIP), a computational method for generating these configurations. NPIP generates needle configurations that are specific to the anatomy of the patient, avoid critical structures near the penile bulb and other healthy structures, and avoid needle collisions inside the body. NPIP consisted of three major components: a method for generating a set of candidate needles, a needle selection component that chose a candidate needle subset to be inserted, and a dose planner for verifying that the final needle configuration could meet dose objectives. NPIP was used to compute needle configurations for prostate cancer data sets from patients previously treated at our clinic. NPIP took two user-parameters: a number of candidate needles, and needle coverage radius, δ. The candidate needle set consisted of 5000 needles, and a range of δ values was used to compute different needle configurations for each patient. Dose plans were computed for each needle configuration. The number of needles generated and dosimetry were analyzed and compared to the physician implant. NPIP computed at least one needle configuration for every patient that met dose objectives, avoided healthy structures and needle collisions, and used as many or fewer needles than standard practice. These needle configurations corresponded to a narrow range of δ values, which could be used as default values if this system is used in practice. The average end-to-end runtime for this implementation of NPIP was 286 s, but there was a wide variation from case to case. The authors have shown that NPIP can automatically generate skew line needle configurations with the aforementioned properties, and that given the correct input parameters, NPIP can generate needle configurations which meet dose objectives and use as many or fewer needles than the current HDR brachytherapy workflow. Combined with robot assisted brachytherapy, this system has the potential to reduce side effects associated with treatment. A physical trial should be done to test the implant feasibility of NPIP needle configurations.

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.

Fundamental Study of Barrier Discharge and Ozone Generation Characteristics for Multiple Needles to Plane Configuration

A multiple needles electrode system is one of the good configurations because of easy generation of corona and dielectric barrier discharge suitable to ozone production. On this configuration, discharge and ozone generation characteristics are affected by needle configuration such as needle density, adjacent needles, but their influence has not been clarified in detail until now. In this study, the relationship between barrier discharge characteristics and ozone generation under AC voltage application has been investigated for triple needles-plane configuration with two different needle-tip curvatures (r = 15, 80 m) in dry air, which is a simpler multiple needles configuration. Characteristics of barrier discharge and ozone generation depend on the needle-tip distance and need-tip radius. In the case of the multiple needles configuration with a smaller needle-tip's distance, the barrier discharge characteristics have been strongly affected by the adjacent needles each other. Especially, the ozone production characteristics depend on the needles configurations. The configuration with a smaller needles distance has good ozone productivity compared with other configurations. In addition, ozone concentration and ozone generation efficiency for the triple needles with r = 80 m were higher than those for the needles with r = 15 m. These results can be interpreted by the effect of the space charges and accumulated charges induced by corona discharge and barrier discharge on the space for ozone generation.

Spinal anaesthesia in young patients: evaluation of needle gauge and design on technical problems and postdural puncture headache

AbstractBackground: The well-known complication of spinal anaesthesia, postdural puncture headache (PDPH), is especially troublesome in young patients. The needle gauge and configuration of needle tip appear to be the important factors in reducing the incidence of PDPH; however it may increase the incidence of technical problems.Objective: To evaluate the role of 25 and 27 gauge Quincke and Whitacre spinal needles on technical difficulties and incidence of PDPH in patients between 16 and 40 years of age.Methods: Eight hundred patients receiving spinal anaesthesia for urological surgery were divided into four groups of 200 each according to spinal needle used. Group Q-25 and group Q-27 received spinal anaesthesia with 25 gauge and 27 gauge Quincke needles whereas in group W-25 and group W-27, 25 gauge and 27 gauge Whitacre needles were used. The parameters observed were technical problems in terms of number of attempts, failure rate, time to cerebrospinal fluid (CSF) detection and incidence and severity of...

Methods for prostate stabilization during transperineal LDR brachytherapy

In traditional prostate brachytherapy procedures for a low-dose-rate (LDR) radiation seed implant, stabilizing needles are first inserted to provide some rigidity and support to the prostate. Ideally this will provide better seed placement and an overall improved treatment. However, there is much speculation regarding the effectiveness of using regular brachytherapy needles as stabilizers. In this study, we explored the efficacy of two types of needle geometries (regular brachytherapy needle and hooked needle) and several clinically feasible configurations of the stabilization needles. To understand and assess the prostate movement during seed implantation, we collected in vivo data from patients during actual brachytherapy procedures. In vitro experimentation with tissue-equivalent phantoms allowed us to further understand the mechanics behind prostate stabilization. We observed superior stabilization with the hooked needles compared to the regular brachytherapy needles (more than 40% in bilateral parallel needle configuration). Prostate movement was also reduced significantly when regular brachytherapy needles were in an angulated configuration as compared to the parallel configuration (more than 60%). When the hooked needles were angulated for stabilization, further reduction in prostate displacement was observed. In general, for convenience of dosimetric planning and to avoid needle collision, all needles are desired to be in a parallel configuration. In this configuration, hooked needles provide improved stabilization of the prostate. On the other hand, both regular and hooked needles appear to be equally effective in reducing prostate movement when they are in angulated configurations, which will be useful in seed implantation using a robotic system. We have developed nonlinear spring-damper model for the prostate movement which can be used for adapting dosimetric planning during brachytherapy as well as for developing more realistic haptic devices and training simulators.

Needle-type field-effect transistor based on carbon nanotube derivative without lithography process

A carbon nanotube network field effect transistor was fabricated on the edge of a glass needle using no lithography. A glass pipette with solder inside was heated and stretched to form a needle. After Au layer deposition on the outer needle, a CNT network was fabricated by immersing the needle top into a CNT solution. The current between the solder and the Au layer, which depends on the liquid gate potential and the buffer pH, is measured. Because the needle configuration is controllable by heating the glass tube, it can be fabricated easily without lithography, producing sensors for use in various fields.

A greedy heuristic using adjoint functions for the optimization of seed and needle configurations in prostate seed implant**Part of this work was presented at the 45th Annual AAPM meeting in San Diego, California on 10–14 August 2003.

We continue our work on the development of an efficient treatment-planning algorithm for prostate seed implants by incorporation of an automated seed and needle configuration routine. The treatment-planning algorithm is based on region of interest (ROI) adjoint functions and a greedy heuristic. As defined in this work, the adjoint function of an ROI is the sensitivity of the average dose in the ROI to a unit-strength brachytherapy source at any seed position. The greedy heuristic uses a ratio of target and critical structure adjoint functions to rank seed positions according to their ability to irradiate the target ROI while sparing critical structure ROIs. Because seed positions are ranked in advance and because the greedy heuristic does not modify previously selected seed positions, the greedy heuristic constructs a complete seed configuration quickly. Isodose surface constraints determine the search space and the needle constraint limits the number of needles. This study additionally includes a methodology that scans possible combinations of these constraint values automatically. This automated selection scheme saves the user the effort of manually searching constraint values. With this method, clinically acceptable treatment plans are obtained in less than 2 min. For comparison, the branch-and-bound method used to solve a mixed integer-programming model took close to 2.5 h to arrive at a feasible solution. Both methods achieved good treatment plans, but the speedup provided by the greedy heuristic was a factor of approximately 100. This attribute makes this algorithm suitable for intra-operative real-time treatment planning.

Electrode Configuration and Polarity Effects on Physicochemical Properties of Electric Field Treated Apples Post Harvest

The trial compared the use of needle and plate electrode configuration (corona discharge) with parallel plate electrode configuration for postharvest treatment of apples ( Malus domestica Borkh, cv. Fuji and Golden Delicious) during storage. The effect of electric field direction on physicochemical properties of fruit was also investigated. In Fuji apple storage, physicochemical parameters varied with water core content. Treatment of apples kept between parallel plate electric field suppressed weight loss unlike in the corona discharge field. Respiration and climacteric peak were suppressed in apples kept between parallel plate electric field. In corona discharge, after 7 days more respiration was noted in the treated than the untreated samples. The ‘reversed’ electric field treatment (apples on cathode plate) gave higher weight loss than the corresponding ‘forward’ electric field treatment (apples on anode plate) in the parallel plate arrangement. In corona discharge, the multiple of evaporation rate (ratio of water loss in treated sample to that of untreated sample) was higher for the ‘forward’ electric field direction (negative needle polarity) than the ‘reversed’ electric field direction (positive needle polarity).

Underestimation of access flow by ultrasound dilution flow measurements

For hemodialysis access surveillance, flow measurements are increasingly considered important because they identify accesses at risk of thrombosis. Usually these flow measurements are performed with the ultrasound dilution technique. In a previous patient study it was observed that the resulting flow values were systematically low as compared to magnetic resonance flow measurements, but a satisfactory explanation was lacking. In the present study, we will demonstrate by hemodynamic calculations and in vitro experiments that this discrepancy can be explained by a temporary reduction of the access flow rate, caused by the reversed needle configuration during ultrasound dilution flow measurements. In this configuration, blood is injected retrogressively at one needle and flow between the needles is increased, causing an increased dissipation of energy. The proposed explanation is subsequently confirmed in a patient with a loop graft, by measuring the blood velocity by Doppler ultrasound as a function of reversed dialyzer flow rate. Apart from the ultrasound dilution technique, these findings are applicable to other recently proposed methods for measuring access flow that employ the reversed needle configuration.

Modulation of the optical path through pork using sliding needles

Pork muscles were probed with a pair of hypodermic needles containing optical fibers. The 1-mm diameter optical fibers formed elliptical windows in the 30° tips of the hypodermics. The windows faced each other, trapping 60° of sample when the needle tips were level. The detector needle was linked to a grating monochromator and photomultiplier, while the illuminating needle (linked to a halogen source and solenoid shutter) moved in and out of the meat (range±9.5 mm relative to the tip of the detector needle). In distilled water, the relationship between needle position and direct transmittance ( T) from one needle to the other approximated a sine wave (wavelength 10 mm). Maximum T did not occur when the needle tips were level, but when the illuminating needle was 2.5 mm ahead of the detector needle. In pork muscles, selective absorbance by myoglobin created a strong Soret absorbance band at 420–440 nm. As the sliding needle moved into the meat, T at 400 nm showed little change (0.1–0.2 T relative to white Teflon with needles level). But light at 700 nm peaked ( T=2.3) with the illuminating needle 2.59±1.30 mm ahead of the detector needle. However, as the illuminating needle was withdrawn from pork samples, this distance was reduced to 1.17±1.03 mm ( P < 0.05; n=11), possibly indicating a reflective boundary in the collapsed needle track. This needle configuration is suggested for on-line use because it is highly responsive to scattering ( T sine wavelength > 15 mm) and allows optical path length to be modulated.

In vitro investigation of cerebrospinal fluid leakage after dural puncture with various spinal needles.

Postspinal headache is one of the most common complications of spinal anesthesia and has repeatedly led to controversy concerning needle size and configuration. In an in vitro investigation, we measured cerebrospinal fluid (CSF) leakage with Sprotte, Whitacre, Quincke, and Atraucan needles under physiological conditions in human dura. The puncture characteristics were examined under an electron microscope. The pencil-point needles show 2-3 times less leakage of CSF compared with the cutting Quincke needles of corresponding size. Between the Sprotte and the Whitacre needles, there were no significant differences. The least loss of CSF occurred with the 26-gauge Atraucan needle. Under the electron microscope, a sharply delineated, persistent perforation channel was shown with the Quincke needles, which may explain the high CSF loss. With pencil-point needles, which push the tissue apart bluntly, a large opening on the inside is found, with some tearing of the dura. However, in contrast to the cutting needles, a persistent perforation channel is not manifested. The 26-gauge Atraucan needle, which both cuts and pushes apart conically, shows a relatively discrete opening on the inside, with slight tears in the dura and arachnoidea but without a visible perforation channel. The results of our study show that larger needles (26-gauge Atraucan) that are easier to handle can lead to good and, in some cases even better, puncture results if they have characteristics of both the cutting and the pencil-point needles. We compared several brands of pencil-point and standard cutting spinal needles of varying sizes. All pencil-point needles had less cerebrospinal fluid leakage, the least loss occurring with 26-gauge Atraucan needles. Electron microscopic examination of the dura after puncture showed characteristic findings with each needle type. We conclude that the combined cutting and pencil-point characteristics seen in the Atraucan needle may have clinical advantages.

Negative heterosis not apparent in 22-year-old hybrids of Picea mariana and Picea rubens

Work from the 1970s indicated that, relative to either parent species, crosses between red spruce (Picea rubens Sarg.) and black spruce (Picea mariana (Mill.) B.S.P.) were inferior with respect to both growth and photosynthesis. We re-examined the hypothesis that there is negative heterosis in hybrids of red and black spruce using 22-year-old trees in a common garden study planted on two sites. The trees were the product of controlled crossings and represent a continuum from hybrid class 0 (pure black spruce) to hybrid class 1 (pure red spruce). Progeny of all controlled crosses were measured for height and diameter. A subset of families were measured for gas exchange and were assessed using a hybrid index based on needle color, needle configuration, twig ridges, twig bark color, vegetative bud color, and cone scale morphology. Tree growth rate linearly declined with the increasing proportion of red spruce germplasm (increasing hybrid index). In 1994, intermediate hybrid index classes did not differ in gas exchange from either pure black spruce (hybrid index class 0) or pure red spruce (hybrid index class 1), and in 1996, hybrids displayed slightly higher rates of gas exchange. Thus, negative heterosis was not apparent in 22-year-old trees. Individual tree hybrid index generally agreed with expectation based on midparent means, although the relationship was stronger on the higher productivity site (r2 = 0.91) than the poorer productivity site (r2 = 0.54).Key words: black spruce, heterosis, hybrid, photosynthesis, red spruce.

5423193 Low-maintenance system for maintaining a cargo in a refrigerated condition over an extended duration: Claterbos John K; Fulton Stephen C Warrenton, OR, 97146, United States

Clear needle visualisation is recognised as an unmet need for ultrasound guided percutaneous needle procedures including regional anaesthesia and tissue biopsy. With inadequate needle visibility, these procedures may result in serious complications or a failed operation. This paper reports analysis of the modal behaviour of a previously proposed ultrasound-actuated needle configuration, which may overcome this problem by improving needle visibility in colour Doppler imaging. It uses a piezoelectric transducer to actuate longitudinal resonant modes in needles (outer diameter 0.8–1.2 mm, length > 65 mm). The factors that affect the needle’s vibration mode are identified, including the needle length, the transducer’s resonance frequency and the gripping position. Their effects are investigated using finite element modelling, with the conclusions validated experimentally. The actuated needle was inserted into porcine tissue up to 30 mm depth and its visibility was observed under colour Doppler imaging. The piezoelectric transducer is able to generate longitudinal vibration with peak-to-peak amplitude up to 4 μm at the needle tip with an actuating voltage of 20 Vpp. Actuated in longitudinal vibration modes (distal mode at 27.6 kHz and transducer mode at 42.2 kHz) with a drive amplitude of 12–14 Vpp, a 120 mm needle is delineated as a coloured line in colour Doppler images, with both needle tip and shaft visualised. The improved needle visibility is maintained while the needle is advanced into the tissue, thus allowing tracking of the needle position in real time. Moreover, the needle tip is highlighted by strong coloured artefacts around the actuated needle generated by its flexural vibration. A limitation of the technique is that the transducer mode requires needles of specific lengths so that the needle’s resonance frequency matches the transducer. This may restrict the choice of needle lengths in clinical applications.

Hemostatic protein polymer sheath: improvement in hemostasis at percutaneous biopsy in the setting of platelet dysfunction.

To study the effectiveness of the protein polymer sheath (PPS), a device intended to limit hemorrhage caused by percutaneous biopsy, in the setting of platelet dysfunction (which may be an important cause of such hemorrhage), percutaneous biopsies were performed in eight anesthetized pigs: four control pigs and four pigs treated with the experimental aspirinlike drug venopirin. These biopsies were performed with (a) a cutting needle only, (b) the cutting needle equipped with the PPS, and (c) the cutting needle equipped with a thrombin-coated PPS. Needle configuration and biopsy site were randomized. Blood loss associated with each needle configuration was measured and compared with that associated with the other configurations. Venopirin caused a statistically significant increase in blood loss with all needle configurations. The PPS significantly reduced blood loss in both the control pigs and those treated with venopirin (P < .05); thrombin coating was a statistically significant factor only in the venopirin-treated pigs.