FRIDAY MORNING, 20 MAY 2005 REGENCY E, 8:30 A.M. TO 12:00 ...

2:30
5pBB2. A system to evaluate and compare transducers used for lung sound research. Steve S. Kraman, George R. Wodicka,
Gary A. Pressler, and Hans Pasterkamp Kentucky Clinic J515, Univ. of Kentucky, Lexington, KY 40536 Purdue Univ., West
Lafayette, IN 47907 Purdue Univ., West Lafayette, IN 47907 Univ. of Manitoba, Winnipeg, MB, Canada
Since lung sounds were first recorded and analyzed in the 1960s, a variety of custom made or adapted transducers have been used
for detecting these sounds. There is no standard lung sound transducer nor have those in use been adequately compared. To address
this problem, a test platform was constructed that provides a stable and reproducible sound source coupled to a viscoelastic surface
that is mechanically and acoustically similar to human skin and subcutaneous tissue as judged from comparisons with similar
thicknesses of fresh meat and fat. The device was designed to be equally suitable for air-coupled microphones and for accelerometers.
When driven by a broadband noise source, the acoustic amplitude at the surface of the platform was found to be relatively uniform
from 100 to 1200 Hz. The system was used to evaluate a variety of lung sound transducers. They were found to vary significantly in
frequency response with no device appearing to be adequate as an all-purpose lung sound sensor. It is concluded that lung sound
characteristics are likely to be significantly affected by the type of sensor used to acquire the sound. This makes comparisons between
differently equipped laboratories difficult.
2:55
5pBB3. Vascular sounds as an indicator of hemodialysis access patency.
Sandler Rush Medical College, Chicago, IL 60607
Hansen Mansy, Silas Hoxie, Nilesh Patel, and Richard
Background: Vascular access for renal dialysis is a lifeline for about 200 000 individuals in North America. Stethoscope auscultation
of vascular sounds has some utility in the assessment of access patency, yet may be highly skill dependent. The objective of this
study is to identify acoustic parameters that are related to changes in vascular access patency. Methods: Fifteen patients participated
in the study. Their vascular sounds were recorded before and after angiography, which was accompanied by angioplasty in most
patients. The sounds were acquired using two electronic stethoscopes and then digitized and analyzed on a personal computer. Results:
Vessel stenosis changes were found to be associated with changes in acoustic amplitude and/or spectral energy distribution. Certain
acoustic parameters correlated well correlation coefficient0.98, p less than 0.0001 with the change in the degree of stenosis,
suggesting that stenosis severity may be predictable from these parameters. Parameters also appeared to be sensitive to modest
diameter changes greater than 20%, (p less than 0.005, Wilcoxon rank sum test. Conclusions: Computerized analysis of vascular
sounds may have utility in vessel patency surveillance. Further testing using longitudinal studies may be warranted. Work supported
by NIH/NIDDK DK 59685.
3:20–3:30 Break
Contributed Papers
3:30
5pBB4. Computational and experimental models for sound
transmission in the pulmonary system and chest to aid in medical
diagnosis. Serhan Acikgoz, Thomas J. Royston, M. Bulent Ozer Univ.
of Illinois at Chicago, 842 W. Taylor St. MC 251, Chicago, IL 60607,
Hansen A. Mansy, and Richard H. Sandler Rush Univ. Medical Ctr.,
Chicago, IL 60612
Acoustic wave propagation in the pulmonary system and torso is simulated
by coupling a numerical acoustic boundary element model that predicts
sound propagation throughout the solid tissues with a proven comprehensive
analytical model for sound wave propagation in the airways of
the bronchial tree that is valid up to at least 2 kHz. This approach enables
modeling various pathologies that result in structural changes in the lung
and/or changes in breath sound source and strength. The model may be
also used to predict the resulting acoustic changes measured by acoustic
sensors, e.g., stethoscopes, accelerometers, or other skin-contact sensors.
Experimental studies in a novel lung phantom model are used to partially
validate the computational model. This study focuses on low audible frequencies,
i.e., less than 2 kHz. This range encompasses naturally generated
respiratory sounds that have been shown to have diagnostic value, as well
as externally-introduced vibro-acoustic stimuli used for diagnosis. Work
supported by NIH EB 003286-01.
3:45
5pBB5. Recent developments in the characterization of anisotropic,
biological media utilizing magnetic resonance elastography. Anthony
J. Romano, Nicolas P. Valdivia, Philip B. Abraham, Joseph A. Bucaro
Naval Res. Lab., 4555 Overlook Ave, Washington, DC 20375-5320,
romano@pa.nrl.navy.mil, Philip J. Rossman, and Richard L. Ehman
Mayo Clinic and Foundation, Rochester, MN 55905
In this paper, we present recent developments in the characterization of
anisotropic, biological media utilizing displacements measured with dynamic
MRE. In one approach, a waveguide constrained analysis is applied
to physical structures such as muscle, which evaluates the velocities of
wave propagation along arbitrarily oriented fibers or fiber bundles in a
local fashion, utilizing a spectral filter and a sliding window, spatial Fourier
transform. In a second approach, the anisotropic equations of elasticity,
in variational form, are inverted for a determination of the complex
moduli comprising the medium. Issues concerning ill-conditioning, the
effects of boundary conditions, and multiaspect excitation requirements
will be addressed, as well as a discussion concerning the models which are
appropriate for various physical situations. These two complementary
methods of analysis will be demonstrated utilizing both phantom as well
as in vivo dynamic displacement measurements.
2615 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2615
5p FRI. PM