Design of an Endoscopic Biopsy Needle With Flexural Members

[+] Author and Article Information
Stacy L. Figueredo, Alexander H. Slocum

 Massachusetts Institute of Technology, Precision Engineering Research Group, Cambridge, MA 02139

William R. Brugge

 Massachusetts General Hospital, Gastrointestinal Endoscopy Unit, Boston, MA 02114

J. Med. Devices 1(1), 62-69 (Jul 28, 2006) (8 pages) doi:10.1115/1.2355693 History: Received May 19, 2006; Revised July 28, 2006

As a minimally invasive means of extracting a tissue sample from a patient, current endoscopic biopsy needles generally do not preserve tissue histology and often require multiple attempts to obtain a tissue sample. This paper presents an endoscopic biopsy needle with internal flexures that enables tissue to enter the hollow needle and then be severed from the surrounding tissue when the needle is withdrawn. Using force-deflection and sample weight data from 10× scaled prototypes, variations of a flexural design captured 1.1grams of a tissue phantom on average, as compared to wedge-type designs that averaged 0.70.8grams. Sample mass exhibited an increase in mass as the feature angle decreased. Peak entrance forces (P2) for the flexure design were lower than for both wedge and extended wedge designs, and resistance forces (S2) were higher upon needle extraction. A low-angle (15 and 30deg) feature also produced a lower entrance friction (S1) and higher exit resistance (S2) compared with 45 and 60deg features. These results suggest that a biopsy needle with 15deg flexures could increase sample length and mass as well as sampling success rates for core biopsy procedures. Future tests of the flexural biopsy needle design will use this information to determine dimensions for laser cut features of 1× scale needles.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Functional requirements of endoscopic biopsy needle

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Figure 2

First-order estimates of cutting force and cutting strategies

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Figure 3

Needle prototype cross-sections

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Figure 4

Force displacement curve for a flexural design with characteristic drop during needle puncture and sharp decrease in force during tissue tearing. Peaks from piercing and design features are also present.

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Figure 5

Force displacement curve of pre-pierced site showing slope from friction of outer wall, which is estimated using a linear best-fit approximation

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Figure 6

Flexure deformation sequence while entering gelatin during test. (a) Piercing, (b) initial entrance, and (c) sample collected prior to withdrawal and severing.

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Figure 7

Average sample mass (g) versus design type with a sample size of 10. Standard deviation noted above each data set.

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Figure 8

Average sample mass (g) versus feature angle (degrees) with a sample size of 10. Standard deviation noted above each data set.

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Figure 9

Comparison of design type to characteristic peaks

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Figure 10

Comparison of feature angle to characteristic peaks

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Figure 11

Relationship between feature type and characteristic slopes

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Figure 12

Comparison of feature angle to characteristic slope




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