High frequency ultrasound in monitoring organ viability for transplantation

1
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 1Department of
Medical Biophysics, University of Toronto
2Ontario Cancer Institute, 3 Department of
Mathematics, Physics and Computer Science,
Ryerson University, Toronto, Ontario, Canada
RESULTS Fig 2, Liver Decay
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 (HE) and TUNEL staining.

• 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 HE 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.
• Acknowledgments
• The Whitaker Foundation
• Dr. Sherars lab

0h
0h
10h
0h 1h 2h
10h
10h
4h 8 h
10h
Liver Decay vs. Liver Preservation in University
of Wisconsin solution
Fig 5, UW 8C UW 21C Decay 21C

The normalized spectra are correlated with
captured images at different time points and with
(HE) and Tunel staining of analyzed organs,
taken at the beginning and at the end of the
experiments.
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
Fig 6, Kidney Decay
Fig 7, Decay Preservation
0h 4h 6h 10h
Power, dBr