Photoacoustic and Ultrasound Imaging with Nanosized Contrast Agents - Nanotechnology for Biomedical Imaging and Diagnostics - page 291

10.4 intrinsic contrasts for Pat

PAT has been successfully provided anatomical and functional information of
biological tissues using intrinsic contrasts. Major endogenous absorbents include
two types of hemoglobin (i.e., oxyhemoglobin and deoxyhemoglobin), melanin,
lipid, and water [80]. In addition, by using different optical wavelengths, PAT can
spectrally distinguish each chromophore. For example, two types of hemoglobin and
melanin dominantly absorb visible light, while water and lipid absorb near-infrared
(nIr) light. Figure 10.4 shows the agent-free morphological PA images. A single
melanoma (Fig. 10.4a) and red blood cell (Fig. 10.4b) are clearly imaged by using a
subwavelength optical-resolution PAM system in vitro , which confirms the capability
of agent-free PA imaging [81]. As shown in Figure 10.4c, PAT clearly visualizes the
morphologies of a B16 melanoma skin cancer and its surrounding vasculatures in
small animals in vivo based on these intrinsic contrasts [76]. Further, PAT can
provide the whole-body small animal images acquired with endogenous contrasts
and an array-based PACT system. Figure 10.4d shows volumetric PA rendering of

(a) (b)

5 µm

10 µm

CN

(c) (d)

Spleen

Partial lobe
of liver

Right
kidney

Left
kidney

Ovarian
vessel

Melanoma BV 3 mm

Ovarian
vessel

Interior
vena cava

5 mm

figure 10.4 PA images of intrinsic chromophores. In vitro PA images of (a) B16 melanoma
cells and (b) red blood cells. Cn, cell nuclei (reprinted with permission from ref. [81].
© optical Society of America.), (c) Volumetric anatomical PA image of B16 melanoma
(778 nm) and its feeding blood vessels (570 nm) (reprinted with permission from ref. [76].
© American Chemical Society.). BV, blood vessels, (d) In vivo noninvasive volumetric PA
image of the whole nude mouse body obtained at 755 nm. (Permission from ref. [71]. © SPIE.)