A new handheld optical imager promises advances over current handheld optical mammography devices by providing a 3-D image of the entire breast on a flexible surface that better matches the natural curvature, according to study data presented on Tuesday at the 2008 meeting of the Radiological Society of North America (RSNA). Optical imaging using near infrared light between 700nm and 900nm where light tends to be readily absorbed and that involves inference from the deflection of light emitted from an infrared or laser source to an anatomic cell tissue. Currently available handheld optical imagers devices are flat and provide only spectroscopic imaging.

Existing hand held devices lack of a flexible surface does not match the natural curvature of the tissue, such as the NIRScannerTM under development by Drexel University and will be commercialized by NIRScan Inc. In the past few years, there has been a move towards developing hand held optical imagers. Also the existing hand held devices are designed for spectroscopic imaging where they are imaging only the local area of the breast tissue but not tomographically 3-D reconstructing the entire breast volume for diagnostic applications, such as EX1301 multi-beam OCT Microscope developed by Michelson Diagnostics Ltd. "These flat surfaces are then attempted to be applied to a curved surface and results in poor surface contact," explained Anuradha Godavarty, PhD, Assistant Professor in the Department of Biomedical Engineering of Florida International University, who conducted the study.

"Our goal is to come up with a portable device that matches breast curvature with a flexible probe head and also perform tomographic imaging where you can get a 3-D image," explained Dr. Godavarty. (Read the abstract here.) The unique features of this hand-held optical probe are the flexible probe head that can move from 0o degrees to 45o degrees on both arms, the simultaneous illumination from 6 independent sources and detection from 165 detectors for rapid data acquisition and the ability to image a 4x9 cm2 entire area. Here coregistration techniques are implemented via installing motion tracking facilities. Initially, a modulated NIR signal (50-200 MHz) is launched via a laser diode (785nm) base source. The intensified modulated fluorescence signal is collected by the ICCD based detector.  Two oscillators are used to modulate the source and detector ends. These oscillators are phase locked, and upon changing this phase delay between these two oscillators, phase sensitive images are acquired by the ICCD detector towards ultimately obtaining frequency-domain measurements in terms of AC and phase shift. "Unlike some other imaging techniques, optical signals tend to multiply and scatter requiring the use of complex models to reconstruct an image," stated Dr. Godavarty. A motion tracker is installed on this hand-held probe towards developing coregistration facilities.

Tissue phantoms—essentially a spherical indocyanine object inside a1% liposyn cube background—were used in a study that demonstrated real-time co-registered imaging. Then 3-D tomographic analysis was used to successfully recover the target. One example of a tomographic reconstruction performed for the first time was a 0.45 cc target at 1.5 cm deep under perfect uptake conditions. Multiple targets were also used at depths varying from 1 to 2.5 cm deep and they were able to reconstruct the targets without any artifacts. In addition, a heterogeneous scattering medium was used to simulate a real environment of a breast with cancer tumors and here also the objects were located in a 3-D manner. Preliminary in-vivo studies are now ongoing to demonstrate the effectiveness of real-time co-registration in actual tissues with curvatures. "Of course, these are just a few studies to initially demonstrate the ability to reconstruct targets without artifacts. The next step would then be to test the device on healthy subjects with simulated breast tumors on the surface of the breasts. Finally, we would perform studies with actual breast cancer subjects where we already know they have breast cancer from another imaging modality such as x-ray screening, and we perform the same study, with and without FDA-approved contrast agents measured with real time and tomographic mapping," Dr. Godavarty said in an audio interview with MedicExchange. (Listen to the interview here.)

"In conclusion, we have demonstrated tomographic reconstruction for the first time with a new hand held optical device. The work has been published, and there also are plans to publish some unpublished data that shows the ability to remove noise. Also we have demonstrated real-time coregistration in vitro as well as in vivo. The significance of the work is that there are implications for hand held noninvasive use in diagnosis, prognosis, and chemotherapeutics."

Dr. Godavarty is actively looking to enter clinical trials, seeking clinical partners and sources of funding to accelerate the program. "The technology would be a very good diagnostic tool which is more portable and relatively inexpensive compared to MRI," Dr. Godavarty told MedicExchange. "The doctor can run the test in their office very quickly and complement that with x-ray, which is more of a screening tool."

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