Photoacoustic and Ultrasound Imaging with Nanosized Contrast Agents - Nanotechnology for Biomedical Imaging and Diagnostics - page 289

(a) (b) (c)

Gas bubbles
escaping
diving bell
Mouse

Prism

Nd. YAG
laser

Tunable
dye-laser

Mirror

Laser

z

Ground glass

x Trigger Stop motor

y

Membrane

Water

PC

Concave lens
Ground glass
Membrane
Water
tank
Gas
proportioner
meter
O 2 + N 2 + CO 2

Oscilloscope

Fiber bundle

Breathing mask

Transducer
Animal
holder

Pre stressed
berglass rods
Black tape

cer array

Oxygen tube

Amplier

Probe

PA
image

(d) (e)

Hemi
spherical
US array

US
image
US
system

DAQ

US probe

Scanning
stage

Hand held
PA/US probe

Fiber bundles

Dye laser Nd: YAG laser

Laser

figure 10.2 Various types of PACT systems implemented by (a) a single-element ultra-
sound transducer with 360° full circular mechanical scanning (reprinted with permission from
ref. [69]. © SPIE, (b) a full-ring ultrasound array (reprinted with permission from ref. [70]. ©
SPIE, (c) an arc-shaped ultrasound array (reprinted with permission from ref. [71]. © SPIE
(reprinted with permission from ref. [72]. © optical Society of America, (d) a hemisphere
ultrasound array, and (e) a handheld probe modified from a clinical ultrasound array system.
(reprinted with permission from ref. [40]. © The American Association of Physicists Medicine.)

was greatly improved to a frame rate of 0.9 Hz (Fig. 10.2b) [70, 73]. Using this
system, functional brain [70] and whole-body imaging [74] of small animals have
been successfully performed. As another example, an arc array (64 elements and a
central frequency of 5 MHz) was implemented to provide whole-body imaging of
rodents (Fig. 10.2c) [71]. The acquisition time of one three-dimensional (3d) image
was 8 min. To further enhance clinical translation, clinically friendly PACT systems
have been recently developed such as tomographic PA breast scanners and linear-
array-based PA probes. Figure 10.2d shows the schematic of a tomographic PA and
US breast scanner consisting of 128 US elements with a center frequency of 5 MHz
[72]. This system can be potentially used to screen early stage of breast cancer
patients and map breast angiography. In addition, a handheld PA and US probe
(Fig. 10.2e), modified from a clinical US system (Philips iU22), is currently used in
phase I clinical studies to monitor early response of chemotherapy and identify
sentinel lymph nodes in breast cancer patients [40, 41]. The second type, PAM,
uses a single-element focused US transducer to directly collect one-dimensional
(1d) depth-sensitive images (referred to as A-lines) and 2d/3d images with
mechanical or optical raster scanning [50, 61, 62, 75]. Hardware-based acoustic or
optical focusing provides the transverse resolution, whereas the acoustic bandwidth