Diagnosis of edema, abnormal accumulation of water in tissue, is important for managing various traumatic injuries and
diseases. However, there is no established method for real-time, noninvasive monitoring of edema. In severe extensive
burn injuries, edema develops both topically and systemically due to the increased permeability of blood vessels. In this
study, we examined photoacoustic (PA) monitoring of edema formed in rat burn models. Deep dermal burn with a 20%
total body surface area was made in the dorsal skin of rats. Burn and its adjacent nonburn tissues were irradiated with
6-ns light pulses at 1430 nm, which is one of the absorption peak wavelengths of water in the near infrared. The PA signal
amplitude increased until 12 - 24 hr postburn, and thereafter it gradually decreased to its initial level; the latter phase
(after 24 hr postburn) coincided with a diuretic phase in the rats. There was a significant correlation between the PA
signal amplitudes and water contents in the tissue measured by wet/dry weight method. These findings demonstrate the
validity of PA measurement for real-time, noninvasive monitoring of edema.
We investigated the validity of photoacoustic (PA) measurement for monitoring granulation tissue formed in the grafted
artificial dermis (AD) in rats. We found that the depths of granulation tissue or neovascularities in the grafted AD can be
monitored by PA measurement. There was a significant correlation between the PA signal amplitude and the density of
neovascularities in the granulation tissue. These results suggest the usefulness of PA measurement for monitoring the
adhesion of grafted ADs.