Kp. Kostli et al., Optoacoustic tomography: time-gated measurement of pressure distributions and image reconstruction, APPL OPTICS, 40(22), 2001, pp. 3800-3809
Optoacoustic imaging is a potential novel medical imaging technology to ima
ge structures in turbid media to depths of several millimeters with a resol
ution of some tens of micrometers. Thereby short laser pulses generate ther
moelastic pressure waves inside a tissue, which are detected on the surface
with a wideband ultrasonic transducer. Image reconstruction has the goal o
f calculating the distribution of the absorbing structures in the tissue. W
e present a method in which the acoustic field distribution is captured as
a two-dimensional snapshot at the sample surface, using an optical-reflecta
nce-based detection principle with a detection resolution of 20 mum. A new
image reconstruction is accomplished by backprojection of the detected two-
dimensional pressure distributions into the sample volume by use of the del
ay between the laser pulse and the time the snapshot was taken. Two-dimensi
onal pressure-wave distribution and image reconstruction are demonstrated b
y simulations and experiments, in which small objects are irradiated with l
aser pulses of 6-ns duration. The method opens the possibility to irradiate
the sample hidden in a light-scattering medium directly through the detect
or plane, thus enabling front-surface detection of the optoacoustic signals
, which is especially important if structures close to the tissue surface h
ave to be imaged. Reconstructed tomography images with a depth resolution o
f 20 Lm and a lateral resolution of 200 mum are presented. (C) 2001 Optical
Society of America.