Christopher Favazza

In vivo photoacoustic tomography of chemicals: high-resolution functional and molecular optical imaging at new depths

High-resolution volumetric optical imaging modalities, such as confocal microscopy, two-photon microscopy, and optical coherence tomography, have become increasingly important in the biomedical imaging field. However, due to strong light scattering, the penetration depths of these imaging modalities are limited to the optical transport mean free path in biological tissues, for example, ∼1 mm in the skin. Photoacoustic tomography (PAT), an emerging hybrid imaging modality that can provide strong endogenous and exogenous optical absorption contrasts with high ultrasonic spatial resolution using the photoacoustic (PA) effect, has overcome the fundamental depth limitation. The image resolution is scalable with the ultrasonic frequency. The imaging depth is limited to the reach of photons and up to a few centimeters deep in biological tissues. This Review will focus on the following aspects of PAT described in works published from 2003 to 2009: (1) multiscale PAT systems, (2) morphological and functional PAT using intrinsic contrasts (hemoglobin or melanin), and (3) functional and molecular PAT using exogenous contrast agents (organic dyes, nanoparticles, reporter genes, or fluorescence proteins).

In Vivo Molecular Photoacoustic Tomography of Melanomas Targeted by Bioconjugated Gold Nanocages

Early diagnosis, accurate staging, and image-guided resection of melanomas remain crucial clinical objectives for improving patient survival and treatment outcomes. Conventional techniques cannot meet this demand because of the low sensitivity, low specificity, poor spatial resolution, shallow penetration, and/or ionizing radiation. Here we overcome such limitations by combining high-resolution photoacoustic tomography (PAT) with extraordinarily optical absorbing gold nanocages (AuNCs). When bioconjugated with [Nle(4),D-Phe(7)]-alpha-melanocyte-stimulating hormone, the AuNCs can serve as a novel contrast agent for in vivo molecular PAT of melanomas with both exquisite sensitivity and high specificity. The bioconjugated AuNCs enhanced contrast approximately 300% more than the control, PEGylated AuNCs. The in vivo PAT quantification of the amount of AuNCs accumulated in melanomas was further validated with inductively coupled plasma mass spectrometry (ICP-MS).

Simultaneous functional photoacoustic and ultrasonic endoscopy of internal organs in vivo

At present, clinicians routinely apply ultrasound endoscopy in a variety of interventional procedures that provide treatment solutions for diseased organs. Ultrasound endoscopy not only produces high-resolution images, but also is safe for clinical use and broadly applicable. However, for soft tissue imaging, its mechanical wave–based image contrast fundamentally limits its ability to provide physiologically specific functional information. By contrast, photoacoustic endoscopy possesses a unique combination of functional optical contrast and high spatial resolution at clinically relevant depths, ideal for imaging soft tissues. With these attributes, photoacoustic endoscopy can overcome the current limitations of ultrasound endoscopy. Moreover, the benefits of photoacoustic imaging do not come at the expense of existing ultrasound functions; photoacoustic endoscopy systems are inherently compatible with ultrasound imaging, thereby enabling multimodality imaging with complementary contrast. Here we present simultaneous photoacoustic and ultrasonic dual-mode endoscopy and show its ability to image internal organs in vivo, thus illustrating its potential clinical application.

Pulsed-laser-induced dewetting in nanoscopic metal films : Theory and experiments

Hydrodynamic pattern formation (PF) and dewetting resulting from pulsed-laser-induced melting of nanoscopic metal films have been used to create spatially ordered metal nanoparticle arrays with monomodal size distribution on

Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films

\mathrm{Si}{\mathrm{O}}_{2}∕\mathrm{Si}

In vivo photoacoustic microscopy of human cutaneous microvasculature and a nevus

substrates. PF was investigated for film thickness

A 2.5-mm diameter probe for photoacoustic and ultrasonic endoscopy

h\ensuremath{\leqslant}7\phantom{\rule{0.3em}{0ex}}\mathrm{nm}l

Self-organized metal nanostructures through laser-interference driven thermocapillary convection

laser absorption depth

Laser-induced short- and long-range orderings of Co nanoparticles on SiO2

\ensuremath{\sim}11\phantom{\rule{0.3em}{0ex}}\mathrm{nm}

In vivo functional photoacoustic microscopy of cutaneous microvasculature in human skin

, and different sets of laser parameters, including energy density