Effects of Needle and Catheter Size on Commercially Available Ultrasound Contrast Agents

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1 ORIGINAL RESEARCH Effects of Needle and Catheter Size on Commercially Available Ultrasound Contrast Agents John R. Eisenbrey, PhD, Annemarie Daecher, BS, Michael R. Kramer, BS, Flemming Forsberg, PhD Received November 3, 2014, from the Department of Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania USA (J.R.E., A.D., M.R.K., F.F.); Villanova University, Villanova, Pennsylvania USA (A.D.); and School of Medicine, Temple University, Philadelphia, Pennsylvania USA (M.R.K.). Revision requested December 9, Revised manuscript accepted for publication February 6, We thank Lei Yu, PhD, of Thomas Jefferson University s Flow Cytometry Core Facility for assistance with the flow cytometry system. The ultrasound contrast agents SonoVue and Sonazoid were provided by Bracco SA (Geneva, Switzerland) and GE Healthcare (Oslo, Norway), respectively. Address correspondence to John R. Eisenbrey, PhD, Department of Radiology, Thomas Jefferson University, 132 S 10th St, Philadelphia PA USA. john.eisenbrey@jefferson.edu Abbreviations UCA, ultrasound contrast agent doi: /ultra Objectives To investigate effects of needle and catheter size on in vitro ultrasound contrast agent (UCA) enhancement and concentrations using 4 commercially available UCAs. Methods Definity (Lantheus Medical Imaging, North Billerica, MA), Optison (GE Healthcare, Princeton, NJ), SonoVue (Bracco SA, Geneva, Switzerland), and Sonazoid (GE Healthcare, Oslo, Norway) were investigated. The UCA was injected via a 1-mL syringe (BD, Franklin Lakes, NJ) into a 3-way stopcock (Smith Medical, Dublin, OH) and flushed with 10 ml of saline through an 18-cm infusion extension tube connected to either a 16-, 18-, 20-, 22-, or 24-gauge catheter (BD) or an 18-, 20-, 21-, or 25-gauge needle (BD). In vitro enhancement was determined in a flow phantom (ATS Laboratories, Bridgeport, CT), and microbubble concentrations were determined using an LSRII flow cytometer (BD Biosciences, San Jose, CA). Results Significant decreases in enhancement and microbubble concentrations were observed for all 4 UCAs (P <.001) when administration was performed through a 25- gauge needle. No statistically significant differences in enhancement or concentrations were observed between all catheter sizes and 18- to 21-gauge needles for SonoVue and Sonazoid. Definity and Optison administration through a 24-gauge catheter resulted in a significant loss of enhancement (P <.02), although these differences were not significant on flow cytometry. Conclusions Administration of commercial UCAs in a clinical scenario is possible with catheters or needles smaller than 20 gauge, although the minimal allowable size appears to be UCA specific. Key Words catheter size; Definity; needle size; Optison; Sonazoid; SonoVue Ultrasound contrast agents (UCAs) are shell-stabilized, gasfilled microbubbles whose differences in acoustic impedance and compressibility relative to the surrounding blood provide ultrasound enhancement. 1 These UCAs act as blood pool agents and are generally introduced into the bloodstream via a bolus injection or an infusion through an intravenous catheter. Additionally, because microbubbles are relatively fragile (they can be destroyed by higher-intensity acoustic pulses or hydrostatic pressure), larger catheters or needles are generally preferred to avoid destruction via shear stresses and hydrostatic pressure during administration. Consequently, current clinical guidelines recommend using a venous catheter or needle with a diameter of 20 gauge or larger by the American Institute of Ultrasound in Medicine J Ultrasound Med 2015; 34:

2 Achieving intravenous access with larger catheters or needles may be difficult in some patients, may be associated with increased patient discomfort, and is not feasible in smaller-animal models. Costantino et al 3 reported a success rate of 33% for first-attempt sticks to obtain intravenous access with 18-gauge catheters in 2 emergency departments in urban settings (although this rate increased to 97% with the addition of ultrasound guidance). Other studies have reported success rates of 64% to 91% but have not included details on numbers of attempts or catheter sizes. 4,5 In an ongoing research study on contrast-enhanced breast ultrasound imaging in humans, 6 our group has observed an estimated 70% success rate on first attempts in the placement of 20-gauge catheters for UCA injection and has lost approximately 5% of study patients after 3 or more failed attempts at obtaining intravenous access. The use of smaller venous access catheters or needles may partially avoid some of these complications, although little published data on their influence on microbubble properties exist. Hence, the purpose of this study was to examine the quantitative effects of needle and catheter size on commercial UCA enhancement and concentrations in vitro. Materials and Methods Ultrasound Contrast Agent Administration In this study, Definity (Lantheus Medical Imaging, North Billerica, MA), Optison (GE Healthcare, Princeton, NJ), SonoVue (Bracco SA, Geneva, Switzerland), and Sonazoid (GE Healthcare, Oslo, Norway) were investigated. The properties of these agents, as well as dosages used (based on published recommendations for liver imaging), are provided in Table The UCA was injected via a 1-mL syringe (BD, Franklin Lakes, NJ) into a 3-way stopcock (Smith Medical, Dublin, OH) parallel to the tubing and flushed with 10 ml of saline through an 18-cm infusion extension tube (with a volume of 0.72 ml) connected to either a 16-, 18-, 20-, 22-, or 24-gauge catheter (19 30 mm in length; BD) or an 18-, 20-, 21-, or 25-gauge needle (16 44 mm in length; BD) into a stirred reservoir. The extension tubing connecting the stopcock to the needle/syringe had an internal diameter of 3 mm and offered no noticeable increased resistance. The reservoir was stirred with a magnetic stir bar spinning at approximately 300 rpm and used to maintain a homogenous solution within the flow phantom. This setup (with catheters) is used for off-label testing and research studies at our institution and is also the recommended setup in the literature. 11 An infusion rate of approximately 2.5 ml/s was used during saline flushing (administered by a single investigator and timed by a stopwatch) for all sizes greater than 25 gauge. This flow rate was based on case report forms from published UCA clinical research studies 6,12 13 as well as off-label examinations for liver imaging at our institution. A slightly slower infusion rate (1 ml/s) was required when using the 25-gauge needle because of pressure encountered during administration through this needle size. Although slower flow administration rates may result in decreased microbubble destruction, a reasonably quick flush is required during clinical examinations with bolus injections to achieve adequate wash-in/wash-out kinetic measurements and to better appreciate enhancement during peak enhancement in less vascularized applications such as breast imaging. In Vitro Enhancement Ultrasound imaging was performed using a LOGIQ 9 scanner (GE Healthcare, Milwaukee, WI) with a 9L linear probe fixed with a positioning arm and operating in the coded harmonic imaging mode. After the catheter/administration process described above, the scaled liver-imaging dosages were added to 800 ml of stirred water. This scaling of 16% of the recommended clinical dosage was selected to provide similar microbubble concentrations within the reservoir (800 ml) to the approximate total human blood volume (5 L). Contrast was imaged in a flow phantom (ATS Laboratories, Bridgeport, CT) within a 6-mm vessel at a depth of 2 cm, connected to a stirred reservoir and a peristaltic pump (S10k II; Terumo, Tokyo, Japan). Still images were collected every 30 seconds for 20 minutes and stored. Enhancement was then quantified in ImageJ (National Institutes of Health, Bethesda, MD) with signal intensity in the vessel expressed in decibels relative to baseline. Table 1. Properties of Commercial UCAs Used Reported Reported Concentration, Dosage for Liver UCA Shell Gas Diameter, μm Bubbles/mL Imaging, ml Definity Phospholipid Octafluoropropane E Optison Albumin Octafluoropropane E Sonazoid Phosphatidylserine Perfluorobutane E SonoVue Phospholipid Sulfur hexafluoride E J Ultrasound Med 2015; 34:

3 Flow Cytometry Flow cytometry was performed with an LSRII flow cytometer (BD Biosciences, San Jose, CA) to determine the effects of 18-gauge or smaller catheter or needle administration on microbubble concentrations and size distributions. After the administration described above from a second set of experiments injected into a 50-mL glass beaker, 10 μl of a microbubble and flush mixture was added to 0.5 ml of deionized water and 10 μl of CountBright ultraviolet absolute counting beads (Life Technologies, Grand Island, NY). These beads contain μm beads/10 μl and are used as a counting standard in flow cytometric applications. The addition of a known quantity of beads with a unique ultraviolet signal (allowing later separation from the microbubble signal) provides the ability to correlate the machine counts to a total solution concentration. No direct interaction between these beads and the microbubbles is expected. This process is a unique counting method, although our group has recently used it to quantify experimental microbubble concentrations. 14 Counting beads and microbubbles were separated by bead fluorescence using forward scatter and phycoerythrin filters. Concentration and relative size distribution analysis was then performed using Flowing version software (Perttu Terho, Turku, Finland). Statistical Analysis All experiments were performed in triplicate and plotted as the mean ± standard deviation. Statistical significance between groups was determined using a 1-way analysis of variance with a Bonferroni posttest adjustment for multiple comparisons. Significance between individual groups was determined using a Student t test. All statistical analyses were performed in Prism software (GraphPad Software, San Diego, CA) with significance determined by α =.05. Results Example ultrasound images from the flow phantom are provided in Figure 1. These examples show enhancement (gold signal on right) within the vessel lumen 5 minutes after injection of Optison through 18-gauge (A), 20-gauge (B), 21-gauge (C), and 25-gauge (D) needles. A noticeable reduction in enhancement was observed when Figure 1. Ultrasound images of the flow phantom showing in vitro enhancement (gold signal on right) 5 minutes after injection of Optison through 18-gauge (A), 20-gauge (B), 21-gauge (C), and 25-gauge (D) needles. J Ultrasound Med 2015; 34:

4 administration was performed through 25-gauge needles. In vitro enhancement over time for all 4 UCAs after administration through each set of catheters and needles is shown in Figures 2 and 3, respectively. A significant decrease in enhancement was observed for all 4 UCAs (P<.001) when administration was performed through a 25-gauge needle, with an approximate drop in enhancement of 4 to 7 db at injection and 7 to 18 db 20 minutes after injection. No statistically significant differences in in vitro enhancement were observed between all catheter sizes and 18- to 21- gauge needles for SonoVue and Sonazoid (P >.3). Administration of Optison through a 24-gauge catheter resulted in a significant loss of enhancement relative to all larger catheters and needles (P <.02), but no other significant differences were observed between 16- to 22-gauge catheters or 18- to 21-gauge needles. Thirty seconds after injection, administration of Optison through a 25-gauge needle showed significantly reduced enhancement relative to all other needles and catheters (P <.001). However, at this initial time point, no significant differences in enhancement were observed between 24-gauge catheter administration and all larger needles and catheters (P >.28). For Definity, administration through 24-, 22-, and 20- gauge catheters resulted in no significant differences in enhancement relative to each other (P >.24), but decreases in enhancement relative to the 16- and 18-gauge catheters and 18-, 20-, and 21-gauge needles were observed (P<.04). At 30 seconds after administration (the initial time point), the only statistically significant difference between enhancement was found to be between administration through 25- and 18-gauge needles (P =.023). Figure 4 depicts the effect of catheter and needle size on each UCA s concentration. Microbubble concentrations through all needles and catheters other than the 25-gauge needle were found to be consistent with the manufacturers specifications (Table 1). Administration through a 25- gauge needle resulted in a significant decrease in micro - bubble concentration relative to all other needles and catheters for Definity (P =.0006), Optison (P =.0162), and Sonazoid (P =.0162). Administration of SonoVue Figure 2. In vitro signal intensity over time after administration through varying catheter sizes for Definity (top left), Optison (top right), Sonazoid (bottom left), and SonoVue (bottom right) J Ultrasound Med 2015; 34:

5 through a 25-gauge needle showed a decrease in micro bubble concentration, although it was not found to be statistically significant (P =.11). Figure 5 shows the effects of catheter size on size distributions of Definity, Optison, and SonoVue and the effects of needle size on the size distribution of Sonazoid. No appreciable changes in size distributions were apparent between different groups, although a dramatic change in the total number of counts was observed for all agents after 25-gauge needle administration (shown in this example for Sonazoid). Discussion Current clinical guidelines recommend administration of UCAs through venous catheters or needles with a diameter of 20 gauge or larger. 2 However, to our knowledge, no empirical evidence exists supporting this recommendation. In this article, we detail the effects of catheter and needle administration size on in vitro enhancement and population of 4 commercially available UCAs. Defining the minimally required administration route size should allow easier and less painful intravenous access in difficult patients and is applicable in all UCA-based imaging techniques (such as real-time and perfusion imaging). Study parameters (UCA, dosage, infusion setup, and infusion rate) were selected to match clinical settings as best as possible. Our findings demonstrate that catheter and needle sizes smaller than 20 gauge can be used without compromising in vitro enhancement or concentrations, although the minimally allowable size appears to be UCA specific. Although the duration of enhancement observed in our flow phantom does not mimic expected in vivo conditions, relative results demonstrate no apparent changes in microbubble properties using smaller administration routes than currently recommended. 2 Both Sonazoid and SonoVue showed no significant decrease in enhancement or concentration after administration through 22- and 24-gauge catheters or a 21-gauge needle, but a drop off in each parameter was observed when administration was performed through a 25-gauge needle. No reduction was observed with Optison Figure 3. In vitro signal intensity over time after administration through varying needle sizes for Definity (top left), Optison (top right), Sonazoid (bottom left), and SonoVue (bottom right). J Ultrasound Med 2015; 34:

6 after administration through a 22-gauge catheter or 21- gauge needle. A reduction in signal enhancement over a 20-minute period was observed after administration through a 24-gauge catheter, although it was not evident 30 seconds after injection or during concentration measurements, indicating that longer-term stability of the bubbles may be compromised. Definity proved to be the most sensitive to changes in diameter, although no significant differences were observed between 20-gauge catheters (the current guideline recommendation) and 22- or 24- gauge catheters, and no differences in enhancement or concentration measurements were observed at initial time points except for 25-gauge needles. Little variation in in vitro enhancement or concentrations was observed when comparing similarly sized catheters or needles. Administration of UCAs has been recommended through both of these mechanisms, as well as through central lines, ureter catheters, and ports. 2,15 Our findings indicate that the inner diameter (which directly influences hydrostatic pressure during injection) is the main criterion for predicting microbubble destruction during administration, and central lines, ureter catheters, and ports all generally have inner diameters greater than those that were found to destroy microbubbles in this study. Talu et al 16 previously reported on the influence of infusion rate and needle size on an in-house made lipid microbubble. Focusing on small-animal based UCA research, the group showed a microbubble destruction dependency on concentration, infusion rate, and needle size. At the highest flow rate tested (0.5 ml/s), 70%, 98%, and 99% of microbubbles were destroyed after administration through 23-, 27-, and 30-gauge needles, respectively, Figure 4. In vitro microbubble concentration after administration through varying catheter and needle sizes for Definity (top left), Optison (top right), Sonazoid (bottom left), and SonoVue (bottom right). *P < J Ultrasound Med 2015; 34:

7 and this change was also accompanied by a reduction in the microbubble size distribution. 16 Similarly, Barrack and Stride 17 demonstrated that administration through a 25- gauge needle resulted in significant destruction of a homemade agent relative to an 18-gauge needle, although this effect could be partially rectified by suspending the particles in glycerol. In the only study using a commercially available UCA, Browning et al 18 showed that administration of SonoVue through progressively smaller needles (25 29 gauge) led to progressively lower ultrasound microbubble-assisted gene transfection in a mouse model, and this decrease in transfection was attributed to lower microbubble concentrations. These studies highlight the important consideration of needle size and infusion rate when performing microbubble small-animal research, particularly in drug and gene delivery applications. Additionally, these findings match our observations in that infusion through a 25-gauge needle (albeit at a higher infusion rate) resulted in significant destruction of commercially available UCAs. Figure 5. In vitro size distribution after administration through varying catheter sizes for Definity (A), Optison (B), and SonoVue (C) and varying needle sizes for Sonazoid (D). Size is presented in linear arbitrary units (a.u.) but consistently scaled for all plots. J Ultrasound Med 2015; 34:

8 Although this study demonstrates the feasibility of using smaller venous catheters or needles for UCA administration, several limitations exist. The effects of infusion rates were not investigated (slower infusions may potentially reduce microbubble destruction, as pointed out by Talu et al 16 ), but instead rates based on current clinical applications were used. Additionally, a reasonably fast infusion is also required for peak microbubble arrival (corresponding to peak enhancement in less vascular tissue) and for consistent time-intensity curve analysis. Findings were based on a limited number of independent samples to conserve time and resources. Flow cytometry is a relatively unproven technique for microbubble counting, and the inclusion of multiple size standards would allow for better quantification of microbubble sizes. However, calculated concentrations were similar to those provided by the manufacturers, and conclusions matched those observed during flow phantom experiments. Finally, effects of catheter and needle sizes on in vivo enhancement were not investigated. Although in vivo flow dynamics will vary considerably from in vitro settings, such an investigation would be technically challenging because avoiding inherent differences from injection sites and biovariability between animals would require the placement of numerous needles and catheters in close venous proximity to one another. Still, overall conclusions from this in vitro study are expected to correlate with in vivo scenarios, as both the flow phantom and flow cytometry experiments were set up to gauge the percentage of microbubbles surviving the route of administration. In conclusion, administration of commercial UCAs through catheters or needles smaller than 20 gauge does not alter in vitro enhancement or concentrations, although the minimal allowable size appears to be UCA specific. Thus, the use of smaller needles or catheters in patients for whom venous access is technically challenging should not dramatically alter the performance of these commercial UCAs. References 1. Goldberg BB, Raichlen JS, Forsberg F. Ultrasound Contrast Agents: Basic Principles and Clinical Applications. 2nd ed. London, England: Martin Dunitz Ltd; Claudon M, Dietrich CF, Choi BI, et al. Guidelines and good clinical practice recommendations for contrast enhanced ultrasound (CEUS) in the liver update 2012: a WFUMB-EFSUMB initiative in cooperation with representatives of AFSUMB, AIUM, ASUM, FLAUS and ICUS. Ultrasound Med Biol 2013; 39: Costantino TG, Parikh AK, Satz WA, Fojtuk JP. 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