In February 2008, the publishers of BioOptics World and Laser Focus World magazines published the first market research report to quantify the rapidly growing market for optical coherence tomography (OCT) technologies and applications (see www.laserfocusworld.com/articles/318570). Among other things, the report accurately describes the rather complex patent situation in the OCT market:
For much of the time since the introduction of OCT, a handful of companies have controlled most of the intellectual property and key patents. In the ophthalmology market, Carl Zeiss Meditec controls the key patent (US Patent 5,321,501) via its acquisition of Advanced Ophthalmic Devices, the company founded by the inventors of the technology at MIT. LightLab Imaging, which also grew out of the original MIT group, controls the patent for all medical applications outside of ophthalmology.
These patents are quite strong and, even in the fast-growing ophthalmology market where Zeiss sold at least $300 million worth of instruments through 2006, competitors have been kept at bay. Zeiss has enjoyed a virtual monopoly during this time.
In Fourier-domain OCT, spectral-domain OCT does not appear to be covered by the original patent, although swept-source OCT may be. This new, open playing field has allowed a number of companies to introduce products.
However, the following statement in the report’s Executive Summary requires clarification: “Because the Fourier-domain technique is not protected under the original tightly held patents that have limited competition [with time-domain systems], a number of companies are now developing or marketing Fourier-domain OCT products.”
The key OCT patent (5,321,501), “Method and apparatus for optical imaging with means for controlling the longitudinal range of the sample,” was issued on June 14, 1994. Carl Zeiss Meditec (through its subsidiary, Humphrey Instruments) obtained the rights to this patent in ophthalmology in 1994 when it acquired Advanced Ophthalmic Instruments (founded in 1992 by Eric Swanson, Jim Fujimoto, and Carmen Puliafito). Lightlab Imaging (founded in 1997 by Swanson, Fujimoto, and Mark Brezinski and originally called Coherent Diagnostic Technology) retained the rights for other medical imaging applications and began pursuing nonophthalmic applications and granting application-specific licenses.
The ‘501 patent describes primarily time-domain OCT but also discloses some general concepts of Fourier-domain OCT. The ‘501 patent recently reissued, with 200 new claims on top of the original claim set. These new claims cover several aspects of basic Fourier-domain imaging as well as many application-specific claims, including ophthalmology, microscopy, and endoscopy. Because the spectroscopic version of Fourier-domain OCT has been described in the open literature (which may pre-date the original patents), the patent situation concerning spectral-domain OCT (a form of Fourier-domain OCT) appears more open to interpretation. Most of the new ophthalmic OCT systems use the spectral-domain technique. This may be related in part to the perception of patents and in part to the fact that spectral-domain systems technology led swept-source technology (particular in the 800 nm band) when the product-development efforts were launched several years ago.
“Collectively the MIT and subsequent separately invented and cross-licensed Zeiss and Lightlab patents describe broad concepts of broadband interferometric imaging into biological tissues and other specimens using time domain, frequency domain, and in many cases spectral domain, either from a system or application, perspective,” says Eric Swanson, one of the inventors of this technology and lead author on a number of patents related to OCT. “Some focus on core system concepts such as time domain, frequency domain, spectral domain, and in general broadband interferometric imaging, while others focus on implementation details (such as Faraday circulators, interferometer configurations, and the like), scanning methods (grating delay lines, rotating cams, spectrometers, swept sources, etc.), microlenses, probes (such as rotating, forward imaging, side imaging, integration with flushing catheters, balloons, guidewires, ultrasound, or therapeutic lasers), and other application details. All of these factors play into patent protection and positioning.” —KK