This document describes a low-cost 3D ultrasound system developed to image the brachial plexus for regional anesthesia procedures. The system uses two webcams and custom tracking hardware attached to an ultrasound probe to optically track its movement and reconstruct a 3D image from a series of 2D ultrasound images. Initial results demonstrated a proof of concept for generating a 3D image using freely available software, though processing was slow at 8 hours. Faster processing is expected once the software is compiled. The 3D ultrasound system has the potential to help physicians more accurately locate anatomy like the brachial plexus during regional anesthesia procedures.

1. A Low-Cost 3D Ultrasound System for Imaging of the Brachial Plexus for Regional Anesthesia
O. Bigdeli1
, M. Golden1
, K. B. Munir1
, T. Amarel2
, J. Yost2
, and J. H. McIsaac3
1
University of Connecticut, Storrs, CT, 2
Hartford Hospital, Hartford, CT, 3
Univ. of CT/Hartford Hospital, Avon, CT
Introduction: Ultrasound aided regional anesthesia is rapidly becoming a standard of care, with an increased rate of
successful nerve blocks and fewer complications. A 2-dimensional (2D) hand-held scan of the brachial plexus is performed
prior to needle placement. Physicians need to reorient these 2D pictures in their minds to correspond to the 3-dimensional
(3D) structure which is actually being imaged. Viewing the nerve plexus in three dimensions will increase the ability of
physicians to more accurately locate and administer local anesthesia. While 3D ultrasound systems exist, they typically are
too expensive (>$100k) for widespread employment. The aim of this study is to optically register the movement of the
ultrasound transducer during a 2D scan of the brachial plexus and then reconstruct a 3D image with low-cost hardware
($180) and freely available software.
Materials and Methods: The main limitation in converting a 2D ultrasound to 3D is that as ultrasound probe moves, it
produces a series of non-parallel images. In order to reconstruct these into a single 3D image, the movement of the ultrasound
probe needs to be known. Our team designed a “tracking pyramid,” attached to the ultrasound transducer, consisting of three
different colored spheres a known distance from each other and from the imaging surface of the transducer. This tracking
pyramid, while attached to the SLA transducer of a Sonosite M-Turbo®
ultrasound machine, is imaged with two Logitech®
Pro 9000 web cameras, also a known distance from each other. Using LabVIEW®
, a program was written to correlate images
of the tracking pyramid with a movie from the ultrasound probe, both recorded at the same time. Geometric and stereo
triangulation calculations enable us to determine the spatial location of the three spheres in each image, providing
information of the probe’s movement in each of the x, y, and z directions. This information enables us to determine the plane
in which each ultrasound image lays, which is necessary for reconstruction. A 4 second ultrasound MP4 movie was converted
to AVI format because LabVIEW®
cannot operate on the MP4 format. The AVI was loaded into LabVIEW,®
deconstructed
into a series of 30 non-parallel JPEG images and then converted to a series of parallel JPEG images based on the movement
of the ultrasound transducer. Finally these JPEG images were input to National Instrument’s Biomedical Startup Kit®
to
produce a 3D image.
Results and Discussion: The 3D image produced in National Instrument’s freely available Biomedical Startup Kit®
can be
viewed at any angle and from any plane. There will be no need for physicians to recreate in their minds the 3D structure of
the nerve during a procedure. As the images were processed within a non-compiled version of LabVIEW®
and then
reconstructed in Biomedical Startup Kit®
, the processing speed was very slow (8 hrs). If the number of images reconstructed
is decreased, it will take less time, but the resolution and quality of the produced image will be lower. We anticipate a
significant improvement when the LabVIEW®
program is compiled.
Conclusion: Using 3D ultrasound will enable physicians to more accurately locate the brachial plexus when administering
regional anesthesia. This low cost device will enable hospitals and clinics to easily retrofit existing ultrasound technology for
imaging the brachial plexus and other anatomy. With increased processing speed, a 3D image may be able to be produced in
real time during the procedure. It is expected that the rate of successful procedures will greatly improve and complications of
inappropriate needle placement will decrease.