Novemb er 10, 2010 / Vol. 8, No. 11 / CHINESE OPTICS LETTERS 1075
Fluorescence molecular tomography system for in vivo
tumor imaging in small animals
Jianwei Fu (傅傅傅建建建伟伟伟), Xiaoquan Yang (杨杨杨孝孝孝全全全), Guotao Quan (全全全国国国涛涛涛), and Hui Gong (龚龚龚 辉辉辉)
∗
Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics,
Huazhong University of Science and Technology, Wuhan 430074, China
∗
E-mail: huigong@mail.hust.edu.cn
Received March 16, 2010
A fluorescence molecular tomography system for in vivo tumor imaging is develop ed using a 748-nm
continuous wave dio de laser as an excitation source. A high sensitivity cooled charge-coupled device (CCD)
camera with excitation and emission filters is utilized to obtain the excitation and fluorescence images.
The laser beam performs fast raster scanning using a dual-axis galvanometric scanner. The accuracy of the
laser spot position at the source window is within ±200 µm. Based on the phantom exp erimental results,
the spatial resolution is less than 1.7 mm, and the relative quantitation error is about 10%. In vivo imaging
of a tumor-b earing nude mouse tagged with near-infrared dye demonstrates the feasibility of the system.
OCIS codes: 170.6960, 170.6280, 170.0110.
doi: 10.3788/COL20100811.1075.
Nanocarriers serve as carriers that can visualize incipient
tumors in vivo in a non-invasive manner; these are also
used to transport large quantities of drug molecules into
cytosolic compartments of cells, helping achieve great
progress in drug development
[1−3]
. In this field of study,
it is essential to identify accurately the bio distribution
of nanocarriers in vivo after administration to animals.
Various imaging technologies, such as magnetic resonance
imaging (MRI), positron emission tomography (PET),
X-ray computed tomography (CT), and ultrasound, are
widely used in this field
[4−7]
. However, MRI applications
in molecular imaging are limited by its low sensitivity
[8]
.
The main disadvantages of PET are the involvement of
ionizing radiation and non-specific background
[9]
. Of the
abovementioned technologies, CT and ultrasound are the
most commonly used high-resolution anatomical imaging
techniques; however, they are unable to provide molecu-
lar and functional information
[10]
.
Optical imaging is important in conducting molecular
imaging, especially when combined with specific fluores-
cent probes; over the years, it has become an emerg-
ing trend in the fundamental research and application
areas
[11,12]
. Fluorescence molecular tomography (FMT)
aims to obtain realistic three-dimensional (3D) imag-
ing and quantification of fluorophore biodistribution in
deep tissue. Multiple points on the tissue surface are
illuminated successively, resulting in the identification of
diffuse fluorescence originating from specific fluorescent
probes. Spatially dependent fluorophore biodistribution
can be obtained when FMT system is combined with a
proper mathematical model describing light propagation
in tissue. FMT has the ability to perform tumor growth
and brain disease imaging; in addition, it can be used
for chemotherapeutic treatment study and multispectral
imaging
[8,13−16]
.
A biomimetic nanocarrier has been developed in previ-
ous work, and its ability to directly transport functional
cargo into the cytosol of cancer cells has been confirmed
through a type of near-infrared dye
[17]
. In this letter,
we present a slab geometry FMT system, which is tai-
lored to 3D imaging of tumor tagged with this new
nanocarrier. The laser spot positioning accuracy, spatial
resolution, and quantitation accuracy are also evaluated.
In vivo imaging of a tumor-bearing nude mouse is also
performed.
A schematic of the FMT system is shown in Fig. 1. A
748-nm continuous wave (CW) diode laser (B&W TEK,
Newark, Delaware) was used as the excitation source.
The output laser beam was collimated, expanded, and
then directed into the entrance of a dual-axis galvano-
metric scanner (Galvo Scanner ST8061, Shiji Tuotian,
Beijing). A custom-made 160-mm f–θ lens coated with
a 748-nm antireflection film was used to focus the laser
beam on the source window. The diameter of the laser
spot at the source window was about 400 µm. The
typical laser power delivered to the source window was
approximately 10 mW. The laser spot was directed on to
the source window by rotating the mirrors with change-
able input voltages. The voltages were provided by a
data acquisition card (Anmai Zecheng, Beijing), which
converted digital codes to analog voltages. The switching
time between the adjacent points was 0.7 ms.
The imaging objects were fixed in the imaging chamber
filled with optical property matching fluid. The chamber
was made of transparent plastic with high optical trans-
parency and low X-ray absorption. The thickness of the
chamber walls was 2 mm. The optical properties of the
matching fluid were approximately within the range of
Fig. 1. FMT system. M1, M2: mirrors; BE: beam expander;
DW: detection window; LD: laser diode; PC: personal com-
puter; SW: source window
1671-7694/2010/111075-04
c
° 2010 Chinese Optics Letters