High frequency ultrasound in monitoring organ viability for transplantation
Roxana Vlad1, Anoja Giles1, 2, G.J Czarnota1, 2, J.W. Hunt1, 2, M.D. Sherar1, 2 and M.C. Kolios1, 3
of Medical Biophysics, University of Toronto; 2Ontario Cancer Institute, 3 Department of Mathematics, Physics and Computer Science, Ryerson University, Toronto, Ontario, Canada
The VS-40B ultrasound imager employs
two transducers f/2 and f/3 with
operating frequency of 40MHz and a
relative bandwidth of 93% and 95%,
respectively. RF signals are stored
digitally at a sampling rate of 500 MHz
associated with the captured image.
Analysis of normalized spectra on
collected RF data is carried out, Fig 1.
Fig 1
RESULTS
Fig 2, Liver Decay
0h
1h
2h
4h
8h
10h
0h
0h
10h
10h
10h
Liver Decay vs. Liver Preservation in University of Wisconsin solution
Decay
Preservation
Decay vs. Preservation, 0h and 10h
0h 4h
0h 4h
Decay 21C
6h 10h
6h 10h
UW
21C
UW
8C
Fig 3
Frequency, MHz
Fig 4
The normalized spectra are correlated Fig 5, UW 8°C UW 21°C Decay 21°C
with captured images at different time 0h
points and with (H&E) and Tunel
staining of analyzed organs, taken at 10h
the beginning and at the end of the
10h
experiments.
Fig 6, Kidney Decay
10h
0h
4h
6h
10h
9h
Fig 7, Decay
Preservation
The backscatter intensity increased by 5-16
dBr between freshly excised organs imaged
at 0h and the organs imaged after 10h (left to
decay at room temperature), Fig 3 and Fig 7.
This increase is consistent with nuclei
condensation and fragmentation observed in
H&E and Tunel staining of organs left to
decay, Fig 2 and Fig 6.
CONCLUSIONS
The preliminary results show a certain
increase in backscatter intensity comparing
unpreserved organs to preserved ones at the
same time points. This increase in
backscatter intensity is temperature and time
dependent (preserved organs are imaged at
4C and organs left to decay at 20-22C, room
temperature) and the values range in 2-16 dBr
interval, Fig 4, 5 and Fig 7.
• The backscatter intensity increase is more
pronounced in the interval of 20 to 30 MHz
with a peak at 30 MHz, Fig 3 and Fig 4.
• HFU can be considered as a tool for
detecting cell death and/or other changes
occurring during organ decay.
0h 4h
Power, dBr
OBJECTIVE
High frequency ultrasound (HFU) can be used to detect
structural changes in cells and tissues during cell death.
The changes in the ultrasound signal intensity and
frequency spectrum are related to the changes in size,
spatial distribution and acoustic impedance of the tissue
scatterers. We hypothesize that the mechanism behind this
ultrasonic detection is the condensation and fragmentation
that cell nuclei undergo during cell death. Our proposal is to
use high frequency ultrasound and spectroscopy analysis
techniques to follow the decay of organs once they are
harvested for the purpose of transplantation. The ultimate
goal is to assess organ viability for transplantation
procedures.
METHODS
Livers and kidneys from Wistar rats are surgically excised,
flushed with University of Wiscosin solution and stored at
4C for a specified period of time or left to decay at room
temperature. High-resolution images and the corresponding
raw (radio frequency) RF data are collected every one/two
hours from a region of interest located in the transducer
focal zone. At the end of the experiment, samples are fixed
for Hematoxylin & Eosin (H&E) and TUNEL staining.
Power, dBr
1Department
6h 10h
Frequency, MHz
Acknowledgments:
The Whitaker Foundation
Dr. Sherar’s lab