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Technical Innovation |
1 All authors: Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
Received August 17, 2001;
accepted after revision October 30, 2001.
Address correspondence to E. K. Paulson.
Introduction
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A thin, biocompatible polymer coating has been produced that can be applied to metallic surfaces [7]. This polymer coating is applied by the manufacturer (STS Biopolymers, Henrietta, NY) by a process of dipping followed by exposure to water and air drying at slightly elevated temperatures. The polymer film has a porous microstructure that entraps microbubbles of air. As the coated needle is advanced into tissue, air bubbles trapped in the polymeric coating create multiple specular reflectors on the surface of the needle. This polymer coating has been shown to enhance needle visualization in an animal study [7]. The purpose of our study was to test this polymer-coated needle in clinical practice.
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We enrolled 27 patients between October 1, 2000 and February 28, 2001. Our study group consisted of 12 men and 15 women who ranged in age from 31 to 86 years (mean age, 56 years). The patients underwent the following biopsies: liver (n = 15), lymph node (n = 3), pelvis (n = 2), pancreas (n = 2), adrenal gland (n = 2), thyroid (n = 1), spleen (n = 1), and abdominal wall (n = 1). Of the 27 patients, four underwent a single needle pass, and the remainder underwent more than one needle pass.
A 20-gauge needle was used in all biopsies, but the operators were unaware of whether the needle was coated or uncoated. All biopsies were performed using a sonographic unit (700 Logiq; General Electric Medical Systems, Milwaukee, WI) with either a 3.5-MHz curved electronic phased array transducer or a 7- to 10-MHz linear array transducer, depending on the target organ. The appropriate needle guide for the transducer was used at each needle pass to ensure that the angle of the needle relative to the transducer was identical for biopsies with coated and uncoated needles. A cytopathologist was present at each biopsy who determined when sufficient tissue had been obtained for diagnostic purposes. Once the diagnostic material was obtained, no additional needle passes were performed.
At the end of each biopsy procedure, the operator completed a questionnaire indicating the transducer used, the target organ biopsied, and the lesion depth and size. The operator graded visibility of the needle tip and shaft at each needle pass as follows: grade 1, not visualized at all or poorly visualized, with the needle tip and shaft being isoechoic or only slightly more echogenic than the background parenchyma; grade 2, the tip or shaft was visualized with some difficulty, with the shaft and tip readily identified as being more echogenic than the background parenchyma but not seen in their entirety; grade 3, excellent visibility, with shaft and tip strongly echogenic relative to their background and visualized in their entirety.
The grade of visibility of the needle shaft and tip was assessed by the Wilcoxon-Mann-Whitney test. The Kendall's tau b correlation coefficient was determined for lesion depth and the grade of visualization of both the needle tip and the needle shaft.
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The operator visualized the needle tip (rated as grade 2 or grade 3 visualization) in 100% of passes with polymer-coated needles and 84% of passes with uncoated needles. The tip of the coated needle was clearly visualized (grade 3) by the operator in 66% of passes compared with only 32% of passes with the uncoated needle (p < 0.0009) (Fig. 2A,2B). The needle shaft was visualized (grade 2 or grade 3) by the operator in 79% of passes with the coated needle and 28% of passes with the uncoated needle. The shaft of the coated needle was visualized clearly throughout its length by the operator in 27% of passes compared with only 4% of passes made with the uncoated needle (p < 0.0001). We found no correlation between depth of lesion and operator visibility of the needle shaft (Kendall's tau b coefficient = 0.023, p = 0.83) or needle tip (Kendall's tau b coefficient = -0.05, p = 0.63).
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TopIntroductionSubjects and MethodsResultsDiscussionReferences |
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STS Biopolymers has produced a polymer coating, approved by the United States Food and Drug Administration, that can be applied to the surface of needles and other devices such as catheters. In this study, we found that the polymer-coated needle shaft and tip were better visualized by the operator than those of the standard needle (p < 0.0001 and p < 0.0009, respectively), independent of lesion depth.
Although many radiologists performing biopsies with sonographic guidance may have a preference for the freehand technique, our study found that using the needle guide created comparable angles between the needle and the transducer for biopsies with coated and uncoated needles [8].
It has been reported that polymer-coated needles may lose echogenicity when used for several passes, likely as a result of microbubbles of air being replaced by fluid [7]. The results of our study cannot be used to corroborate this observation because, in our practice, we routinely use a new needle for each pass. However, we did encounter a number of instances in which visualization of the shaft and tip of the polymer-coated needle was suboptimal. The shaft of the coated needle was poorly visualized or not visualized by the operator in 21% of cases, and it was seen with some difficulty (grade 2) in 52% of passes. Visualization of the shaft of both polymer-coated and uncoated needles was more difficult when the background parenchyma was echogenic, particularly in areas with an abundance of fatty tissue, such as in the retroperitoneum or in a fatty liver.
Although our study is limited to evaluation of only the 20-gauge polymer-coated needle, it can be suggested that polymer coating is likely to enhance visualization of larger bore needles as well. Larger bore needles are generally better visualized on sonography than smaller needles, and previous investigators reported improved visualization of 22-gauge needles with polymer coating [7].
In conclusion, we believe polymer coating of needles is a promising innovation that improves both needle shaft and tip visibility in clinical practice compared with a standard uncoated needle. Unlike many innovations, the polymer-coated needle does not require the development of a new skill by the radiologist or the acquisition of additional equipment [3,4,5,6]. The availability of these needles may further encourage the transition from CT guidance to sonographic guidance for percutaneous intervention. Further research and development are required to ensure a more consistent performance and consistent visibility for the interventional radiologist using this polymer coating for sonographically guided biopsies.
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  D. I. Jandzinski, N. Carson, D. Davis, D. J. Rubens, S. L. Voci, and R. H. Gottlieb Treated Needles: Do They Facilitate Sonographically Guided Biopsies? J. Ultrasound Med., November 1, 2003; 22(11): 1233 - 1237. [Abstract] [Full Text] [PDF]
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