Photoacoustic microscopy (PAM) has been used to obtain high-resolution, noninvasive images of the in vivo mouse brain. In this work, we exploit the high-depth and temporal resolutions of PAM to noninvasively image the blood-oxygenation dynamics of multiple cortex vessels in the mouse brain simultaneously in response to controlled hypoxic and hyperoxic challenges. These results confirm the ability of PAM to track blood oxygenation in the mouse brain, a critical aspect of imaging brain activity through the hemodynamic response.
In this work, we exploit the high depth and temporal resolutions of PAM to noninvasively image the blood-oxygenation
dynamics of multiple cortex vessels in the mouse brain simultaneously in response to controlled hypoxic and hyperoxic
challenges. The dark-field photoacoustic microscopy (PAM) technique was enhanced to image the cortex vasculature of
the mouse brain in vivo using endogenous hemoglobin contrast with one second temporal resolution. The maximum
values of about 20% with standard deviation ± 1.2% were found to vary significantly among the cortex vessels studied.
The hypoxic response time to rise from 10 % to 90 % of maximum was 63 ± 6 sec. The reverse response time for this
event was 16 ± 2 sec.
Sentinel lymph node biopsy (SLNB) has become the standard method of axillary staging for patients with breast cancer and clinically negative axillae. Even though SLNB using both methylene blue and radioactive tracers has a high identification rate, it still relies on an invasive surgical procedure with associated morbidity. Axillary ultrasound has emerged as a diagnostic tool to evaluate the axilla, but it can only assess morphology and cannot specifically identify sentinel lymph nodes (SLNs). In this pilot study, we propose a noninvasive photoacoustic SLN identification system using methylene blue injection in a rat model. We successfully image a SLN with high optical contrast (146±41, standard deviation) and good ultrasonic resolution (~500 µm) in vivo. We also show potential feasibility for clinical applications by imaging 20- and 31-mm-deep SLNs in 3-D and 2-D, respectively. Our results suggest that this technology would be a useful clinical tool, allowing clinicians to identify SLNs noninvasively in vivo.
Poly(ethylene glycol)-coated Au nanocages have been evaluated as a potential near-infrared (NIR) contrast agent for
photoacoustic tomography (PAT). Previously, Au nanoshells were found to be an effective NIR contrast agent for
PAT; however, Au nanocages, with their more compact sizes (<50 nm compared to >100 nm for Au nanoshells) and
larger optical absorption cross-sections, should be better suited for in vivo applications. In this study, we tested Au
nanocages as a contrast agent for PAT. The result suggests that Au nanocages are promising contrast agents for our
applications. We also present PAT results when novel, dye-containing nanoparticles are used as contrast agents.
Photoacoustic imaging techniques possess high optical contrast with ultrasonic resolution while exceeding imaging
depths of pure optical techniques, affording high resolution images deep within scattering biological tissues. In this
work, we employ reflection-mode photoacoustic microscopy to
non-invasively monitor hemodynamic contrasts and map
brain activity. Changes in vascular dynamics of the mouse somatosensory cortex were evoked through electrical
stimulation of the hindpaw, resulting in increased photoacoustic intensities spatially correlated with contra-lateral
vasculature. Results demonstrate the ability to map brain activation with vascular resolution in three-dimensions, as well
as monitor single-vessel hemodynamics with millisecond temporal resolution. Furthermore, these results implicate the
feasibility of photoacoustic microscopy to probe intra-cortical single-vessel hemodynamics and pave the way for more
extensive functional brain imaging studies.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.