1. Deep Real-Time Optoacoustic Imaging of Breast Tumors
Michael Jaeger, Michael Kitz, Stefan Preisser, Martin Frenz (frenz@iap.unibe.ch)
Institute of Applied Physics, University of Bern
Dieter Schweizer, Joël Niederhauser, Sébastien Sénégas
Fukuda Denshi Switzerland
OptoacousticOptoacoustic (OA) tomography provides(OA) tomography provides
optical images of biological tissuesoptical images of biological tissues
• NIR laser pulse (ns) is launched
into the tissue.
• The light gets absorbed by
structures with enhanced optical
contrast.
• Acoustic transients are
generated upon thermoelastic
effect.
• An image is reconstructed from
detected transients.
• Blood provides optical contrast to
growing cancer. Contrast can be
increased using gold nanoparticles.
• Optical penetration depth deter-
mines the theoretical imaging depth
to some centimeters (~5-10 cm).
Image background challenges OAImage background challenges OA
imaging of deep tissue structuresimaging of deep tissue structures
A novel method reduces backgroundA novel method reduces background
and enables clinical OA imagingand enables clinical OA imaging
ConclusionsConclusions
• Strong OA signals are generated
at the surface where the fluence
is the highest.
• These signals overlap with the
weak signal from a deep tumor.
• Therefore the weak tumor image
is obscured by background.
• The imaging depth is thus
reduced by background to
values much smaller than the
theoretical limit.
• Other sources of background:
- echoes
- reconstruction artifacts
Deep OA imaging of breast phantomsDeep OA imaging of breast phantoms
using DCAusing DCA
home built breast phantoms provide
both acoustic and optical contrast
Ultrasound imaging device (Fukuda
Denshi Switzerland ) adapted for
simultaneous echo and OA imaging
echo image of breast phantom with
optically absorbing artificial tumors
OA image in color scale without (above) and with (below) DCA
processing, overlaid to the corresponding part of the echo image. DCA
leads to strongly increased contrast of the optically absorbing tumors.
• Tumor image and background are differently affected under shear
deformation of the tissue: sources of bulk tissue background are
located close to the surface, and thus suffer less relative displacement.
• Using a combined imaging device, a map of the local tissue
displacement in the image plane can be derived from echo images
acquired simultaneously with OA images.
• The shear-distortion of the OA images is digitally reversed using the
local displacement map. The Distortion-Compensated images are
Averaged (DCA). In the distortion-compensated images, the image of
the tumor is strongly correlated, while background is decorrelated and
averaged out. DCA is computationally simple and real-time capable.
tumor
image
area
displacement of tumor
relative to
background
shear deformation
1st image 2nd image
+ =
1st image 2nd image, compensated resulting DCA image
• We developed a novel method for increased contrast and imaging depth in optoacoustic imaging of large tissue samples.
• The simplicity of this method makes it real-time capable and suitable for a combined OA and echo-ultrasound device.
• The potential impact on improved clinical imaging of breast tumors has been demonstrated using breast tissue phantoms.
1 cm
2 cm
3 cm tumor 1
array position,
depth zero
image of
absorbing structures
absorbing
structures
irradiating
light
ultrasound
transients
sensor
array
image plane
irradiating light
absorption in
irregular bulk tissue
signals detected
at the same time tumor image
background
tumor
reconstructed
OA image with
background
fluence distribution
perp. to image plane
financed by SNF 205320 - 116343 and the FP6 European project PROMET
2 cm
2.5 cm
2 cm
2.5 cm
2 cm
2.5 cm
2 cm
2.5 cmDCA DCA
tumor 1:
OA
echo
tumor 2:
OA
echo