US Patent 8,185,176: Claim Scope, Patent Expiration, Litigation Risk and Fluorescence-Guided AVM Imaging Landscape

US Patent 8,185,176 protects intraoperative detection and confirmation of arteriovenous malformation (“AVM”) removal using a fluorescent dye, image capture, processor-based pixel analysis, and observation of downstream fluorescence. Its broadest commercial significance is concentrated in systems that combine indocyanine green (“ICG”), near-infrared excitation, an imaging camera, and software that compares fluorescence before and after surgical intervention.

The patent is a medical-method and imaging-system patent, not a patent covering ICG itself. It does not create FDA drug exclusivity, and it is not the type of patent normally listed in the FDA Orange Book for a drug product.

What technology does US Patent 8,185,176 protect?

The patent covers two principal operating concepts:

Locating an AVM intraoperatively by observing fluorescent leakage from a suspected vessel.
Confirming removal by determining that fluorescence stops at the resection point and that post-treatment fluorescence intensity and pixel count decline.

The claims require more than merely administering ICG and viewing blood flow. The claimed workflow includes a specific combination of clinical, optical, imaging, and computational steps.

Core claim architecture

Claim group	Subject matter	Principal limitations
Claims 1-27	Intraoperative confirmation of AVM removal	Dye administration, excitation, pixel capture, processor transmission, fluorescence imaging, surgical removal, downstream signal loss, relative maximum intensity and pixel comparison
Claims 28-54	Intraoperative location of an AVM	Fluorescent imaging of a suspected vessel and identification of leakage indicating AVM
Claims 55-64	Portable imaging system	Dye administration device, dual laser-beam source, imaging head, processor, field of view, irradiance, endoscope or surgical microscope

Claims 1 and 28 are the independent method claims. Claim 55 is the principal system claim.

How broad is independent method claim 1?

Claim 1 covers a computer-implemented method of confirming that an AVM-containing vessel has been removed. Every limitation must be satisfied for literal infringement.

Required elements of claim 1

A potentially infringing procedure would generally need to include:

Administration of a fluorescent dye to a subject.
Application of sufficient energy to excite fluorescence in a vessel.
Detection of pixel data within an imaging area.
Transmission of the pixel data to a processor.
Generation of a fluorescence image.
Identification of an AVM location from the image.
Surgical removal of the vessel containing the AVM.
Intraoperative confirmation that fluorescence stops downstream of the removal point.
Processor-based calculation of relative maximum fluorescent intensity.
Comparison of pre-treatment and post-treatment image data.
A conclusion based on reduced pixel count and reduced fluorescence intensity.

The claim therefore has both a physical-procedure component and a data-processing component. A system that uses ICG and visual inspection but does not perform the claimed processor-based comparison may avoid literal infringement of the final limitation, although the doctrine of equivalents could become relevant depending on the facts and prosecution history.

Claim 1's strongest limitation

The most commercially important limitation is the combined signal analysis:

A pre-treatment image and a post-treatment image correspond to the detection area.
The processor evaluates relative maximum fluorescent intensity.
The area of fluorescence is associated with a number of pixels.
Fewer pixels and lower intensity indicate removal.
More pixels and higher intensity indicate non-removal.

This limitation narrows the claim compared with a basic ICG angiography procedure. It creates potential design-around opportunities where the system:

Uses qualitative visual interpretation only.
Measures absolute intensity without comparing pre-treatment and post-treatment images.
Uses vessel segmentation, flow velocity, or time-intensity curves instead of pixel count.
Uses a different algorithm that does not calculate “relative maximum fluorescent intensity.”
Places the comparison in a separate imaging workstation rather than the intraoperative processor.

The enforceability of this limitation would depend heavily on the specification's definitions, prosecution amendments, and the meaning assigned to “relative maximum fluorescent intensity,” “area of fluorescence,” and “detection area.”

What does claim 28 add to the patent estate?

Claim 28 covers intraoperative location rather than post-resection confirmation.

Its central infringement test is whether a suspected vessel is observed for fluorescence leakage and whether that leakage is used to indicate an AVM.

Claim 28 compared with claim 1

Issue	Claim 1	Claim 28
Clinical objective	Confirm removal	Locate suspected AVM
Surgical removal required	Yes	No
Signal behavior	Fluorescence stops downstream of resection	Fluorescence leaks from suspected vessel
Image analysis	Pre/post pixel and intensity comparison	Same processor-based comparison language
Commercial use	Resection verification	AVM mapping and identification

Claim 28 can reach a procedure performed before excision. It may therefore create broader clinical coverage in an operating room where the surgeon uses fluorescence to identify an abnormal vessel but does not use the system to confirm successful removal.

The claim's inclusion of post-treatment comparison language in a locating claim may create construction issues. A defendant could argue that the method must include both the locating function and the specified pre-treatment/post-treatment processor calculation, even though the clinical purpose is locating rather than confirming removal.

What fluorescent dyes and imaging wavelengths are covered?

The claims expressly cover tricarbocyanine dyes and ICG, but claim 1 itself is not limited to ICG.

Claim	Dye or optical limitation
4	Tricarbocyanine dye or analog
5	Indocyanine green
6	Multiple fluorescent dyes or analogs
12	Light energy
13	Laser excitation
17	Incandescent light and filter
18	Infrared spectrum
19	Approximately 805 nm

ICG is the commercially important embodiment because it is an FDA-approved diagnostic dye with established use in vascular and ophthalmic imaging. The patent claims, however, are drafted to reach other fluorescent dyes unless a dependent claim limits the method to ICG.

A competing platform using a different fluorophore may avoid claims 4 and 5 but could still face claim 1 or claim 28 if the dye satisfies the broader “fluorescent dye” language.

Timing and administration limitations

Claims 7-11 and 34-38 cover administration details, including:

Intravenous delivery.
Catheter or cannula administration.
Bolus injection.
Administration less than one hour before confirmation.
Administration more than 30 seconds before confirmation.

These are dependent claims. They narrow the asserted scope but also align closely with common intraoperative ICG practice. A product or procedure that uses a non-bolus infusion, a different delivery route, or a different timing interval may avoid specific dependent claims without avoiding the independent claims.

What portable imaging systems are protected by claims 55-64?

Claim 55 covers a portable system with four required components:

A device for administering fluorescent dye.
An energy source capable of emitting two laser beams.
An imaging head.
A processor configured to perform claim 1 or claim 28.

The dependent claims add hardware and optical parameters.

Claim	System limitation
56	Field of view approximately 0.5-1.5 inches in two dimensions
57	Approximately 1-inch by 1-inch field of view
58	Irradiance of approximately 15-25 mW/cm²
59	Two laser beams converge at a common focal point
60	Green light
61	Infrared radiation
62	Second energy source for a second fluorescent dye
63	Imaging head in an endoscope
64	Imaging head in a surgical microscope

Claim 55's key vulnerability

Claim 55 refers to a processor “coupled to perform the method of claim 1 or claim 28.” That language imports the method limitations into the system claim but leaves potential questions concerning:

Whether the processor must automatically execute every recited method step.
Whether surgical removal can be a system limitation.
Whether the system must include software for both location and removal confirmation.
Whether the alternative “claim 1 or claim 28” formulation creates a claim-construction issue.
Whether a processor that only displays images satisfies the “coupled to perform” requirement.

A system manufacturer may reduce risk by separating imaging hardware from analysis software or by offering a platform that reports raw or processed fluorescence without performing the claimed AVM conclusion.

When does US Patent 8,185,176 lose exclusivity?

US Patent 8,185,176 issued on May 22, 2012. U.S. patent term generally runs for 20 years from the earliest effective nonprovisional or international application filing date, subject to patent-term adjustment, terminal disclaimers, and other statutory calculations under 35 U.S.C. §154.

The issue date alone does not determine expiration. The controlling date is the relevant application filing chain shown in the USPTO file history and the patent's front-page term information. A provisional priority claim does not itself start the 20-year patent term.

Exclusivity timeline

Event	Date or status
Patent issued	May 22, 2012
Statutory term	Generally 20 years from the applicable nonprovisional or PCT filing date
FDA drug exclusivity	Not applicable to this patent
Orange Book listing	Not expected because the claims cover surgical methods and imaging systems
Maintenance fees	Required at 3.5, 7.5 and 11.5 years after grant
Patent expiration	Must be determined from the application filing chain, PTA and maintenance-fee record

The patent's remaining enforceability cannot be inferred from the claims supplied in the question. Patent Center's continuity data, front-page term information and maintenance-fee records control the result.[1]

What is the FDA and Orange Book status of the patent?

US Patent 8,185,176 is not a drug patent in the Orange Book sense.

FDA status of ICG

ICG is marketed as a diagnostic agent, including products such as Indocyanine Green for Injection. The FDA-approved product labeling covers diagnostic imaging uses, including visualization of blood vessels in certain settings.[2]

The patent does not claim:

The ICG molecule.
A pharmaceutical composition of ICG.
A new ICG manufacturing process.
A new FDA-approved indication for ICG as a drug.
A drug-device combination product as such.

An ICG manufacturer would not ordinarily list this surgical imaging-method patent in the Orange Book because Orange Book patent listings generally relate to approved drug substances, drug products, formulations, compositions or methods of use submitted under the applicable NDA framework.[3]

Does a generic ICG applicant face a Paragraph IV challenge?

A Paragraph IV certification applies to patents listed in the Orange Book for a reference listed drug. Because the patent claims focus on intraoperative AVM imaging and portable imaging systems, it is not the type of patent that ordinarily creates a Paragraph IV barrier for an ICG injectable.

A generic ICG applicant could still face commercial or litigation risk if a product label actively encourages use of a patented method, but that is separate from Orange Book listing and Paragraph IV certification.

What patent landscape surrounds AVM fluorescence imaging?

The relevant landscape has four overlapping patent categories.

ICG and near-infrared vascular imaging

This group covers:

ICG angiography.
Near-infrared excitation and emission detection.
Surgical microscopes and endoscopes.
Vascular perfusion assessment.
Real-time video imaging.

These patents may overlap technically with the claimed use of ICG but do not necessarily cover AVM-specific leakage, downstream signal cessation, or the claimed pre/post pixel analysis.

Fluorescence-guided surgery

This category covers:

Tumor visualization.
Tissue perfusion.
Lymphatic mapping.
Identification of abnormal vasculature.
Image-guided surgical navigation.

A platform used for AVM surgery may practice patents in this category even if it avoids the specific claims of US 8,185,176.

AVM-specific surgical methods

AVM patents may claim:

Identification of an AVM nidus.
Differentiation between feeding arteries and draining veins.
Confirmation of complete nidus removal.
Intraoperative angiography.
Surgical treatment of cerebral, spinal or peripheral AVMs.

US 8,185,176 is strongest where the accused system uses fluorescence leakage or loss of downstream signal as the clinical indicator.

Imaging hardware and software

Relevant patents may cover:

Dual-beam illumination.
Laser convergence.
Optical filters.
Camera calibration.
Pixel segmentation.
Intensity normalization.
Fluorescence thresholding.
Endoscopic and microscope-mounted imaging heads.

The patent's claims combine several of these concepts, which may make individual component patents less relevant to a direct infringement analysis but important for freedom-to-operate review.

How strong is the patent estate?

The patent has meaningful but technically narrow protection.

Strengths

Claim 1 combines a defined surgical workflow with processor-based image analysis.
Claim 28 reaches intraoperative AVM localization before removal.
The claims expressly identify ICG and near-infrared excitation.
Claim 55 extends protection to a portable system.
The claims cover both clinical method and device implementation.

Weaknesses

The independent claims contain many limitations.
The processor-based intensity and pixel comparison may be difficult to prove from commercial system operation.
The claims use potentially ambiguous terms such as “relative maximum fluorescent intensity,” “area of fluorescence,” and “detection area.”
Claim 55 incorporates method language into a system claim.
Basic ICG angiography without AVM-specific signal interpretation may fall outside the claims.
A platform using alternative image metrics may create a design-around path.

The practical strength is highest against a system explicitly marketed for AVM detection and resection confirmation that uses ICG, near-infrared laser excitation, pre/post image comparisons and automated removal conclusions.

Which companies may face freedom-to-operate exposure?

Potentially exposed parties include:

Surgical microscope manufacturers offering integrated ICG imaging.
Endoscope manufacturers with near-infrared fluorescence modules.
Companies selling fluorescence-guided AVM navigation software.
Hospital systems developing proprietary AVM image-analysis tools.
Device companies bundling ICG administration, illumination, imaging and processor functions.
Manufacturers licensing image-guided surgery platforms for neurosurgery.

The exposure is lower for:

Conventional angiography systems using X-ray contrast.
Doppler-only systems.
Systems that display fluorescence without AVM-specific analysis.
Platforms using non-fluorescent dyes.
Software that measures perfusion but not the claimed pixel and intensity comparison.
Devices used for tumor or lymphatic imaging without AVM identification.

What patent litigation and settlement issues matter?

The supplied claims do not establish litigation history, settlement terms or current enforcement status. A litigation assessment must distinguish among:

Direct infringement by a device manufacturer.
Method infringement by a hospital or surgeon.
Induced infringement through product labeling or training.
Contributory infringement based on a system configured for AVM surgery.
Validity challenges based on prior ICG angiography, intraoperative angiography and image-processing references.

The most likely validity arguments would target anticipation or obviousness based on combinations of:

ICG fluorescence imaging.
Intraoperative visualization of abnormal vessels.
Detection of AVM leakage.
Confirmation of vascular occlusion or resection.
Computerized pixel and intensity analysis.

The most important prosecution-history issues are whether the applicant added the processor comparison, downstream signal cessation, leakage indication, dual laser beams or AVM-specific limitations to overcome prior art. Any such amendment could narrow claim interpretation and create prosecution-history estoppel.

What generic launch and competitive risks exist?

There is no conventional generic-launch event tied to this patent because it does not claim an orally administered drug or injectable drug product. The relevant competitive event is entry by a medical-device or software platform.

Competitor strategy	Risk under US 8,185,176
ICG imaging without automated analysis	Lower
ICG imaging with AVM leakage detection	Moderate to high
Automated pre/post pixel comparison	High
Near-infrared microscope with AVM workflow software	Moderate to high
Alternative fluorophore	Lower under ICG-specific claims, but claim 1 remains relevant
X-ray angiography	Low
Doppler ultrasound	Low
Manual surgeon interpretation	Lower if no processor calculation occurs
Separate hardware and software suppliers	Depends on inducement and system configuration

Key Takeaways

US Patent 8,185,176 covers fluorescence-guided intraoperative AVM localization and confirmation of AVM removal.
Its central technical combination is fluorescent dye imaging plus processor-based comparison of fluorescence intensity and pixel count.
ICG, infrared excitation near 805 nm, cameras, lasers, endoscopes and surgical microscopes are expressly addressed in dependent claims.
The patent does not claim ICG as a drug and should not be treated as an Orange Book drug patent.
Paragraph IV risk for a generic ICG injectable is generally distinct from this patent's surgical-method claims.
Claim 1 is strongest against automated AVM resection-confirmation systems.
Claim 28 is strongest against systems marketed for intraoperative AVM localization based on fluorescent leakage.
Claim 55 targets portable systems but may present construction issues because it incorporates the method of claim 1 or claim 28.
A design-around may rely on qualitative imaging, alternative fluorophores, different image metrics, or non-fluorescence modalities.
Patent expiration depends on the complete application chain, patent-term adjustment and maintenance-fee status, not the May 22, 2012 issue date alone.

FAQs About US Patent 8,185,176

Does US Patent 8,185,176 cover indocyanine green itself?

No. It covers methods and systems that use fluorescent imaging for AVM localization and removal confirmation. ICG is one expressly claimed dye embodiment.

Can a hospital infringe the patent by using ICG angiography?

Potentially, but routine ICG angiography alone may not satisfy every limitation. Risk increases if the hospital performs AVM-specific leakage analysis, downstream signal assessment and processor-based pre/post image comparison.

Is US Patent 8,185,176 relevant to neurosurgical microscopes?

Yes. Claim 64 expressly covers an imaging head contained in a surgical microscope, subject to the limitations of the incorporated system claim.

Can a fluorescence system avoid the patent by using a dye other than ICG?

Possibly, but changing the dye may avoid ICG-specific dependent claims without avoiding the broader fluorescent-dye language in the independent method claims.

Does the patent block FDA approval of an AVM imaging device?

No. FDA clearance or approval and patent freedom to operate are separate issues. A device can obtain FDA authorization while remaining subject to patent enforcement risk.

References

United States Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/
U.S. Food and Drug Administration. (n.d.). Indocyanine green for injection prescribing information. https://www.accessdata.fda.gov/
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
United States Code. (2023). 35 U.S.C. § 154: Contents and term of patent; provisional rights. https://uscode.house.gov/
United States Patent and Trademark Office. (n.d.). US8185176B2, Intraoperative imaging of arteriovenous malformations. https://patents.google.com/

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Novadaq Tech	SPY AGENT GREEN KIT	indocyanine green	POWDER;INTRAVENOUS, INTERSTITIAL	211580-001	Nov 21, 2018		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				VISUALIZATION OF VESSELS, BLOOD FLOW AND TISSUE PERFUSION OF VESSEL WITH ARTERIOVENOUS MALFORMATION IN VASCULAR,GASTROINTESTINAL, ORGAN TRANSPLANT, AND PLASTIC, MICRO- AND RECONSTRUCTIVE, INCLUDING MINIMALLY INVASIVE, SURGERY	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

PCT Information
PCT Filed	April 26, 2006	PCT Application Number:	PCT/US2006/016101
PCT Publication Date:	November 02, 2006	PCT Publication Number:	WO2006/116634

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
World Intellectual Property Organization (WIPO)	2006116634	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 8,185,176