Design of a Miniature Sonic Flashlight for Guidance of Superficial Subdermal Access

1
Design of a Miniature Sonic Flashlight for
Guidance of Superficial Subdermal Access Gaurav
Shukla1, Bing Wu3,4, David Schwartzmann2, George
Stetten1,2,3,5 1Department of Biomedical
Engineering, University of Pittsburgh, Pittsburgh
PA 15261, USA 2University of Pittsburgh Medical
Center, Pittsburgh PA 15261, USA 3Robotics
Institute, Carnegie Mellon University, Pittsburgh
PA 15213, USA 4Department of Psychology,
Carnegie Mellon University, Pittsburgh PA 15213,
USA 5Department of Biomedical Engineering,
Carnegie Mellon University, Pittsburgh PA 15213,
USA http//www.vialab.org
Motivation
Results
Many clinical procedures require obtaining
meaningful images at very superficial depths.
Surgery for carpal tunnel syndrome, for example,
involves tendons in the first subdermal
centimeter 1. Ophthalmologists are exploring
real-time ultrasonic guidance in corneal surgery
and in accessing structures in the anterior
chamber of the eye 2. Gaining vascular access
in premature neonates is impeded by their
vessels small size and mobility 3.
Ultrasound-guided localization of tumors in
superficial regions (e.g., thyroid) is standard
procedure in cancer biopsies. Motivated by these
applications, we have developed a visualization
device called the Sonic Penlight to provide
in-situ ultrasound guidance to a clinician for
attempting invasive procedures in superficial
regions.
Operators view of the miniature SF, or sonic
penlight (above). The ultrasound probe is
attached at the base of the device, and an
organic LED (OLED) screen displays the ultrasound
data from the probe, which is reflected into the
scanning field (above right). We are able to
clearly visualize structures in the first
centimeter of the scanning field. Here, we show
a 5mm artificial blood vessel embedded 6mm below
the surface in a gel phantom (right). We
demonstrate successful guidance of a needle into
the same model blood vessel (below).
Background
Our lab has developed a novel device for guiding
invasive procedures with ultrasound imaging
called the Sonic Flashlight. 4,5 We place a
half-silvered mirror between a display and the
target area imaged by an ultrasound probe. The
ultrasound image is processed in real time so
that it is displayed at its actual size. By
means of the half-silvered mirror, the ultrasound
slice on the display is reflected into the
scanned area, creating a virtual in situ image in
the patient.
Real-Time Tomographic Reflection
The RTTR system functions by fixing the relative
geometry of the ultrasound transducer, the
display, and a half-silvered mirror to produce a
virtual image at the scanned anatomy within the
body. Through the half-silvered mirror, the
ultrasound image is seen as if it "shines out"
from the probe and illuminates the inner tissue.
Thus the system has been referred to as the Sonic
Flashlight (SF).
A hand viewed through a mirror on the prototype
sonic flashlight
Methods
The organic LED MicrodisplayTM (eMagin) is
smaller than a postage stamp, with 15 mm pixels
and SVGA resolution.
Conclusion
We have successfully prototyped a functional
model of the Sonic Penlight, a device which uses
in-situ visualization of ultrasound data to
facilitate image guidance at superficial depths.
Future models of the SP will incorporate
high-frequency phased array ultrasound
transducers (20 MHz) to provide better
resolution. Also, the size of the SP will be
further reduced so that it will be handily used
in clinical practice. We have demonstrated that
it is possible to use the SP as a guide for
procedures like needle biopsy insertions. In
addition, we have shown that the SP is fully
compatible with surgeons magnifying loupes. In
principle, the operator may perform such
operations with greater accuracy and precision
with the help of the SP.
General schematic of sonic flashlight.
Ultrasound data is captured, processed in custom
software in real-time, and output to the organic
LED (OLED). The mirror is mounted halfway
between the tip of the probe and the bottom of
the OLED, causing the ultrasound video to be
reflected exactly into the scanning field.
The Acuson AcunavTM catheter-based ultrasound
probe (5-10 MHz), introduced for
intracardiovascular imaging, is adapted for the
sonic penlight (d3.25mm)
References
1. Chen P, Maklad N, Redwine M, Zelitt D.
Dynamic high-resolution sonography of the carpal
tunnel. In AJR. 168(2)533-7, (1997) 2.
Krasnik V, Cmelo J, Hasa J. Ultrasonic imaging
of the anterior segment of the eye. In
Ceskoslovenska Oftamologie, Vol 51(4)231-4,
(1995) 3. Nakayama S., Takahashi S., Toyooka H.
Curved-End Guidewire for Central Venous
Cannulation in Neonate. In Anesthesia
Analgesia, Vol 97 (3)917-8, (2003) 4. Stetten
G, Chib V, Overlaying Ultrasound Images on
Direct Vision, Journal of Ultrasound in Medicine
vol. 20, no. 3, pp. 235-240, 2001 5. Stetten G,
System and Method for Location-Merging of
Real-Time Tomographic Slice Images with Human
Vision, U.S. Patent no. 6,599,247, issued
7/29/2003.