Optics & Photonics News - November 2009

microendoscopy system that can detect abnormal changes in the cervix with mild acetic acid staining of the tissue.

Research at the University of Arizona’s Biomedical Imaging Laboratory has focused on laparoscopic imaging of the abdomen, particularly the ovaries. Currently, there is no effective screening technique for ovarian cancer. Confocal microendoscopic imaging of this organ during laparoscopy might represent a viable option for women at high risk of developing the disease who do not want their ovaries removed.

We have developed a rigid confocal microlaparoscope for this purpose. It achieves real-time 30 frames per second imaging in grayscale mode. It can be switched nearly instantaneously to a multi-spectral imaging mode, which— in the current configuration—acquires image data from 500 to 750 nm with approximately 6-nm resolution in about 5 s. The system uses a 488-nm laser excitation source that is well suited to excite fluorophores such as fluorescein sodium and acridine orange. Motorized focus control and a computer-controlled dye delivery channel are incorporated into the device. The system is currently undergoing clinical evaluation.

Miniaturization is a
driving force that
will likely enable
access to even more
restricted locations in
the human body.

biopsy with several commercially available systems. Researchers at various institutions continue to improve upon the basic foundation of this technology by developing novel approaches and investigating new clinical applications. Miniaturization is a driving force that will likely enable access to even more restricted locations in the human body.

A key advantage of this technology is its ability to detect disease at an early stage. The ongoing development of new and effective contrast agents could revolutionize the way diseases are diagnosed by shedding light on the molecular changes that occur even before the onset of visible disease. The high sensitivity of fluorescence-based confocal microendoscopy, with its ability to image living tissue in situ and in real time, fits perfectly within this conceptual framework.

A fundamental challenge for confocal microendoscopy is imaging deeper below the tissue surface. New contrast agents and systems working in the near

infrared or new techniques less sensitive to scattered light could improve upon this c apability.

The large volume of image data produced by confocal microendoscopes and other optical biopsy techniques provides an opportunity for increased diagnostic accuracy but also poses a challenge for interpretation. Automated pattern recognition software in the data stream could help overcome this problem by automatically identifying disease and allowing more focused scrutiny of suspicious areas.

Ultimately, real-time diagnosis provided by optical biopsy creates the potential for integrated treatments that are specifically directed to the site of the disease. Combined diagnostic and therapeutic systems are a logical next step in this rapidly evolving technology. t

Arthur F. Gmitro (gmitro@radiology.

arizona.edu) is the director of the University of Arizona’s Biomedical Imaging Laboratory in Tucson, Ariz., U.S.A. Andrew R. Rouse is on the lab’s research faculty.

Member

Future directions

Confocal microendoscopy is an established imaging technique for optical

5-mm-diameter igid probe

Miniature lens

Focus motor

Syringe with contrast agent

Dye delivery motor

Surgical controls

Flexible cable to optical scan unit

Four push-button controls located on the handle allow the surgeon to adjust the focus, deliver contrast agents, save still images and record videos.

Inside the handle, two motors control focus and dye delivery.

[ References and Resources ]

>> A.F. Gmitro and D. Aziz. “Confocal microscopy through a fiber-optic imaging bundle,” Opt. Lett. 18( 8), 565-7 (1993).

>> D.L. Dickensheets and G.S. Kino. “ Microma-chined scanning confocal optical microscope,” Opt. Lett. 21( 10), 764-6 (1996).

>> G.J. Tearney et al. “Spectrally encoded confocal microscopy,” Opt. Lett. 23( 15), 1152-4 (1998).

>> K.B. Sung et al. “Fiber-optic confocal reflectance microscope with miniature objective for in vivo imaging of human tissues,” IEEE Transactions on Biomedical Engineering 49( 10), 1168-72 (2002).

>> T.D. Wang et al. “Dual-axis confocal microscope for high-resolution in vivo imaging,” Opt. Lett. 28( 6), 414-6 (2003).

>> R. Kiesslich et al. “Confocal laser endoscopy for diagnosing intraepithelial neoplasias and colorectal cancer in vivo,” Gastroenterology 127, 706-13 (2004).

>> A.R. Rouse et al. “Design and demonstration of a miniature catheter for a confocal microendoscope,” Appl. Opt. 43( 31), 5763- 71 (2004).

>> F. Jean et al. “Fibered Confocal Spectroscopy and Multicolor Imaging System for In Vivo Fluorescence Analysis,” Opt. Express 15( 7), 4008–17 (2007).