Magnetomotive microscopy techniques are introduced to investigate cell dynamics and biomechanics. These techniques
are based on magnetomotive transducers present in cells and optical coherence imaging techniques. In this study,
magnetomotive transducers include magnetic nanoparticles (MNPs) and fluorescently labeled magnetic microspheres,
while the optical coherence imaging techniques include integrated optical coherence (OCM)and multiphoton (MPM)
microscopy,and diffraction phase microscopy (DPM). Samples used in this study are murine macrophage cells in culture
that were incubated with magnetomotive transducers. MPMis used to visualize multifunctional microspheres based on
their fluorescence, while magnetomotive OCM detects sinusoidal displacements of the sample induced by a magnetic
field. DPM is used to image single cells at a lower frequency magnetic excitation, and with its Fourier transform light
scattering (FTLS) analysis, oscillation amplitude is obtained, indicating the relative biomechanical properties of
macrophage cells. These magnetomotive microscopy method shave potential to be used to image and measure cell
dynamics and biomechanical properties. The ability to measure and understand biomechanical properties of cells and
their microenvironments, especially for tumor cells, is of great importance and may provide insight for diagnostic and
subsequently therapeutic interventions.
Breast cancer continues to be one of the most widely diagnosed forms of cancer in women and the second leading type
of cancer deaths for women. The metastatic spread and staging of breast cancer is typically evaluated through the nodal
assessment of the regional lymphatic system, and often this is performed during the surgical resection of the tumor mass.
The recurrence rate of breast cancer is highly dependent on several factors including the complete removal of the
primary tumor during surgery, and the presence of cancer cells in involved lymph nodes. Hence, developing means to
more accurately resect tumor cells, along with the tumor mass, and ensure negative surgical margins, offers the potential
to impact outcomes of breast cancer. The use of diffuse optical tomography has been applied for screening optical
mammography applications as an alternative to standard x-ray mammography. The use of coherence ranging and
coherent optical imaging in breast tissue has also found numerous applications, including intra-operative assessment of
tumor margin status during lumpectomy procedures, assessment of lymph node changes for staging metastatic spread,
and for guiding needle-biopsy procedures. The development, pre-clinical testing, and translation of techniques such as
low-coherence interferometry (LCI) and optical coherence tomography (OCT) into clinical applications in breast cancer
is demonstrated in these feasibility studies.
Optical coherence tomography (OCT) is an emerging biomedical imaging modality that has been developed over the last
15 years. More recently, OCT has been used for the intraoperative imaging of tumor margins in breast cancer and
axillary lymph nodes providing a real time in-vivo assessment of the tissue morphology. Traditional OCT images are
limited by only being able to observe morphological structures. As diagnostic medicine continues to push for earlier
detection, one must develop functional imaging modalities that would detect molecular information in-vivo allowing a
real-time microscopic analysis of the tissue specimen. A novel modality of OCT called magnetomotive-OCT (MMOCT)
has been developed by our group, employing an induced modulated magnetic field with a magnetic contrast agent
to create the added contrast to structural OCT images. Modified protein microspheres with a BSA protein shell
functionalized with RGD peptide sequences for targeting and an oil core have been designed and synthesized. Magnetic
nanoparticles (Fe3O4) and Nile Red dye have been encapsulated into its oil core. These microspheres have previously
been demonstrated to target cancer cells by functionalizing them with a layer of RGD peptides and could be
functionalized with monoclonal antibodies. Preliminary results show that these magnetic microspheres, which are 2.0-
5.0 microns in size, are readily detectable under MM-OCT when embedded in a 5% agarose gel, in a 3-D scaffold of
macrophage cells previously incubated with the microspheres, and when injected in-vivo into a tumor from an NMUcarcinogen
rat animal model for breast cancer.
Since its introduction, optical coherence tomography (OCT) technology has advanced from the laboratory bench to the clinic and back again. Arising from the fields of low coherence interferometry and optical time- and frequency-domain reflectometry, OCT was initially demonstrated for retinal imaging and followed a unique path to commercialization for clinical use. Concurrently, significant technological advances were brought about from within the research community, including improved laser sources, beam delivery instruments, and detection schemes. While many of these technologies improved retinal imaging, they also allowed for the application of OCT to many new clinical areas. As a result, OCT has been clinically demonstrated in a diverse set of medical and surgical specialties, including gastroenterology, dermatology, cardiology, and oncology, among others. The lessons learned in the clinic are currently spurring a new set of advances in the laboratory that will again expand the clinical use of OCT by adding molecular sensitivity, improving image quality, and increasing acquisition speeds. This continuous cycle of laboratory development and clinical application has allowed the OCT technology to grow at a rapid rate and represents a unique model for the translation of biomedical optics to the patient bedside. This work presents a brief history of OCT development, reviews current clinical applications, discusses some clinical translation challenges, and reviews laboratory developments poised for future clinical application.
KEYWORDS: Optical coherence tomography, Tissues, Tumors, Lymphatic system, Breast cancer, Cancer, Surgery, Imaging systems, Breast, Signal to noise ratio
Breast cancer continues to be one of the most widely diagnosed forms of cancer amongst women and the second leading
type of cancer deaths amongst women. The recurrence rate of breast cancer is highly dependent on several factors
including the complete removal of the primary tumor and the presence of cancer cells in involved lymph nodes. The
metastatic spread and staging of breast cancer is also evaluated through the nodal assessment of the regional lymphatic
system. A portable real-time spectral domain optical coherence tomography system is being presented as a clinical
diagnostic tool in the intraoperative delineation of tumor margins as well as for real time lymph node assessment. The
system employs a super luminescent diode centered at 1310 nm with a bandwidth of 92 nm. Using a spectral domain
detection system, the data is acquired at a rate of 5 KHz / axial scan. The sample arm is a galvanometer scanning
telecentric probe with an objective lens (f = 60 mm, confocal parameter = 1.5 mm) yielding an axial resolution of 8.3 &mgr;m
and a transverse resolution of 35.0 &mgr;m. Images of tumor margins are acquired in the operating room ex vivo on freshly
excised human tissue specimen. This data shows the potential of the use of OCT in defining the structural tumor margins
in breast cancer. Images taken from ex-vivo samples on the bench system clearly delineate the differences between
clusters of tumor cells and nearby adipose cells. In addition, the data shows the potential for OCT as a diagnostic tool in
the staging of cancer metastasis through locoregional lymph node assessment.
Needle-based devices, which are in wide clinical use for needle biopsy procedures, may be augmented by
suitable optical techniques for the localization and diagnosis of diseased tissue. Tissue refractive index is
one optical contrast mechanism with diagnostic potential. In the case of mammary tissue, for example,
recent research indicates that refractive index variations between tissue types may be useful for the
identification of cancerous tissue. While many coherence-based forward-sensing devices have been
developed to detect scattering changes, none have demonstrated refractive index measurement capabilities.
We present a novel needle-based device that is capable of simultaneously measuring refractive index and
scattering. Coupled to the sample arm of an optical coherence tomography system, the needle device
detects the scattering response and optical pathlength through tissue residing in a fixed-width channel.
Near-infrared measurements of tissues and materials with known optical properties using a prototype
device will be presented. This work demonstrates the feasibility of integrated in vivo measurement of
refractive index and scattering in conjunction with existing clinical needle-based devices.
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