United States Patent 5,573,751 (Drug Patent): Scope, Claim Structure, and US Patent Landscape
United States Patent 5,573,751 centers on ultrasound contrast media built around gaseous microbubbles or microbubble-containing carriers that use fluorine-containing gases, with specific embodiments covering perfluoropropane and perfluorobutane, plus derivative “microbubble-in-carrier” formulations (liposomes, encapsulated microspheres, protein microspheres, crystal/saccharide suspensions, and emulsions). The claims are drafted to (1) lock in a defined fluorinated-gas selection, and (2) expand coverage into multiple microbubble platforms through composition and particle-size limits (including “less than 8 microns” and “2-4 microns”).
What does the patent claim, in plain technical scope?
Core claim theme: fluorinated-gas ultrasound microbubbles
The patent’s independent scope is anchored by Claim 1, which covers ultrasound contrast media comprising gaseous microbubbles where the gas is chosen from a defined list:
- Hexafluoropropylene
- Octafluoropropane
- Octafluoro-2-butene
- Hexafluoro-2-butyne
- Hexafluorobuta-1,3-diene
- Hexafluorocyclobutane
- Decafluorobutane
Claims 2 and 3 narrow this list to octafluoropropane and decafluorobutane, respectively.
Platform expansion: microbubbles embedded in biocompatible carriers
Beyond the gas selection, the patent expands to “contrast agent” formats where the fluorinated gas is present as microbubbles (or is used to replace another gas) inside or as part of a carrier:
- Biocompatible carrier with perfluoropropane microbubbles in an aqueous liquid (Claims 4-7)
- Biocompatible carrier with perfluorobutane microbubbles in an aqueous liquid (Claims 8-11)
- Gas-filled liposomes, improved by including fluorine-containing microbubbles inside liposomes (Claims 12-14)
- Encapsulated air-filled microspheres, improved by replacing air with fluorine-containing gas (Claims 15-18)
- Crystals in saccharide diluent, improved by providing specific fluorinated gases as microbubbles (Claims 19-20)
- Emulsion of highly fluorinated organic compounds, improved by providing fluorine-containing microbubbles in the emulsion (Claims 21)
- Air-filled microbubble suspension, improved by filling microbubbles with fluorinated gases (Claim 22)
How broad is claim coverage across gases vs. carriers?
Gas scope is broad by enumeration
Claim 1 is broad in the sense that it lists multiple fluorinated gases, but the breadth is also bounded because coverage turns on whether the gas is one of the enumerated chemicals.
Enumerated gases in Claim 1 define the gas set that captures Claim 1 directly, and also serve as the basis for later dependent claims that further constrain to specific perfluorinated species.
Carrier scope is broad by platform coverage
The patent uses dependent claim ladders to capture multiple delivery formats for the gas microbubbles:
- simple contrast media comprising microbubbles (Claims 1-3)
- perfluoropropane/perfluorobutane as microbubble gas in a carrier, including aqueous liquid (Claims 4-7, 8-11)
- liposomes loaded with gas microbubbles of fluorinated gases (Claims 12-14)
- encapsulated microspheres where fluorinated gas replaces air, with size and protein formation constraints (Claims 15-18)
- crystals in saccharide diluent with defined crystal size and gas microbubble content (Claims 19-20)
- emulsions where fluorinated-gas microbubbles are provided in the emulsion (Claim 21)
- air-filled microbubble suspensions where gas content is swapped to fluorinated gases (Claim 22)
Particle size limitations narrow infringement opportunities but still leave room
Several claims include microbubble or microsphere size thresholds:
- Microbubbles less than 8 microns: Claims 7, 11, and 14
- Microspheres 2-4 microns: Claim 16
- Crystals range 5-10 microns: Claim 20
These size limits can be pivotal for design-around strategy because many ultrasound contrast products operate across overlapping size ranges.
Claim-by-claim scope map (what each claim actually covers)
Claims 1-3: enumerated fluorinated gases in microbubbles
| Claim |
What is claimed |
Key limitation(s) |
| 1 |
Contrast media for ultrasound imaging |
Gaseous microbubbles of one of the listed fluorine-containing chemicals |
| 2 |
Contrast media of Claim 1 |
Octafluoropropane |
| 3 |
Contrast media of Claim 1 |
Decafluorobutane |
Claims 4-7: perfluoropropane in biocompatible carrier; aqueous option; size cutoff
| Claim |
What is claimed |
Key limitation(s) |
| 4 |
Biocompatible ultrasound contrast agent |
Contains perfluoropropane |
| 5 |
Claim 4 |
At least a portion is present as gaseous microbubbles suspended in a carrier |
| 6 |
Claim 5 |
Carrier is an aqueous liquid |
| 7 |
Claim 5 |
Microbubbles are < 8 microns |
Claims 8-11: perfluorobutane mirror set
| Claim |
What is claimed |
Key limitation(s) |
| 8 |
Biocompatible ultrasound contrast agent |
Contains perfluorobutane |
| 9 |
Claim 8 |
Portion present as gaseous microbubbles suspended in carrier |
| 10 |
Claim 9 |
Carrier is an aqueous liquid |
| 11 |
Claim 9 |
Microbubbles are < 8 microns |
Claims 12-14: gas-filled liposomes with fluorine-containing microbubbles
| Claim |
What is claimed |
Key limitation(s) |
| 12 |
Biocompatible contrast agent with gas-filled liposomes |
Improvement: liposomes include microbubbles of at least one gaseous fluorine-containing chemical |
| 13 |
Claim 12 |
Fluorine chemical is from: perfluoroethane, perfluoropropane, perfluorobutane, sulfur hexafluoride, mixtures |
| 14 |
Claim 12 |
Liposomes are < 8 microns |
Claims 15-18: encapsulated air-filled microspheres, air replaced with fluorinated gas
| Claim |
What is claimed |
Key limitation(s) |
| 15 |
Biocompatible contrast agent suspension of encapsulated air-filled microspheres |
Improvement: replacing air with at least one gaseous fluorine-containing chemical |
| 16 |
Claim 15 |
Microspheres are 2-4 microns |
| 17 |
Claim 15 |
Fluorine chemical is from: perfluoroethane, perfluoropropane, perfluorobutane, sulfur hexafluoride, mixtures |
| 18 |
Claim 15 |
Microspheres are formed from denatured proteins |
Claims 19-20: crystals in saccharide diluent
| Claim |
What is claimed |
Key limitation(s) |
| 19 |
Contrast agent with suspension of crystals in saccharide diluent |
Improvement: providing microbubbles of perfluoroethane, perfluoropropane, perfluorobutane, sulfur hexafluoride |
| 20 |
Claim 19 |
Crystals sized 5-10 microns |
Claims 21-22: fluorinated organic emulsion; air-filled microbubbles with fluorinated gases
| Claim |
What is claimed |
Key limitation(s) |
| 21 |
Contrast agent with emulsion of highly fluorinated organic compounds |
Improvement: provide microbubbles of at least one gaseous fluorine-containing chemical in the emulsion |
| 22 |
Contrast agent with air-filled microbubble suspension |
Improvement: provide perfluoroethane, perfluorobutane, perfluoropropane, or sulfur hexafluoride gas within the microbubbles |
Where the patent draws the “legal hook”: gas identity + microbubble platform
This patent’s infringement posture is primarily driven by two axes:
- Gas identity: whether the ultrasound microbubbles contain one of the enumerated fluorinated gases (Claim 1 list; plus perfluoroethane/perfluoropropane/perfluorobutane/sulfur hexafluoride lists in later claims).
- Structural format: whether the gas microbubbles are present as:
- direct microbubble microdispersion in a carrier,
- contained inside liposomes,
- encapsulated microspheres where air is replaced,
- crystals in saccharide diluent,
- emulsion-associated microbubbles,
- air-filled microbubble suspension where gas is swapped.
That combination yields many potential claim paths for enforcement even when a competitor changes surfactants, stabilizers, or some excipient set, as long as the gas identity and the platform characteristics fall within the claim language.
Practical landscape assessment for competitors (design-around logic using claim constraints)
Design-around levers directly implied by claim text
| Claim constraint |
Competitor design change that can reduce literal overlap |
| Enumerated gas list in Claim 1 |
Use a fluorinated gas not listed in Claim 1 and not covered by later enumerations |
| Perfluoropropane/perfluorobutane dependent claims |
Use only other fluorinated gases outside perfluoroethane/perfluoropropane/perfluorobutane/sulfur hexafluoride sets where required |
| “Microbubbles < 8 microns” (Claims 7, 11, 14) |
Shift microbubble size distribution upward beyond 8 microns (while maintaining ultrasound performance) |
| Microspheres “2-4 microns” (Claim 16) |
Move microsphere size out of 2-4 microns range |
| Crystal size “5-10 microns” (Claim 20) |
Move crystal size out of that range |
| Aqueous carrier requirements (Claims 6, 10) |
Use non-aqueous or mixed solvent systems so carrier is not “aqueous liquid” |
High-risk zones
- Products that use perfluoropropane or perfluorobutane in aqueous carriers with sub-8 micron microbubbles.
- Liposome-based ultrasound contrast where fluorinated gas is present as microbubbles inside liposomes and liposomes are < 8 microns.
- Protein-based encapsulated microspheres in 2-4 micron range with air replaced by fluorinated gas.
- Crystal-in-saccharide formulations where fluorinated microbubbles are generated by the specified fluorine gases with 5-10 micron crystals.
US patent landscape positioning (what this patent blocks and where it likely coexists)
A rigorous landscape map requires prosecution history, priority dates, and citation/forward-citation sets. Those are not provided here, and the request is for a detailed analysis of “scope and claims and patent landscape” for US 5,573,751 specifically. Under the constraint set, this analysis stays confined to the claim scope you provided and derives landscape implications only from those claim features.
What the claims likely cover relative to competing ultrasound platforms
Given the platform diversity in dependent claims, US 5,573,751 appears positioned to overlap with multiple ultrasound contrast technology families:
- Perfluorocarbon microbubble agents (direct gas microbubbles)
- Liposome microbubble agents (gas-filled liposomes with embedded fluorinated microbubbles)
- Protein-shelled or protein-derived microsphere contrast agents (denatured protein microspheres with gas replacement)
- Crystallized payloads in carbohydrate diluents (crystal+saccharide microbubble systems)
- Emulsion-based fluorinated chemistry contrast (emulsion carrying fluorinated gas microbubbles)
- Air-bubble swap formulations (gas within existing microbubble architectures replaced with fluorinated gases)
That means the patent’s practical “landscape footprint” is not limited to one manufacturing approach. It reaches across multiple architectures through the claim’s “improvement” language.
Key Takeaways
- US 5,573,751 claims ultrasound contrast media built from fluorine-containing gaseous microbubbles using an enumerated gas list in Claim 1 and narrower enumerated perfluorocarbon/sulfur hexafluoride sets in later claims.
- Coverage expands across multiple delivery formats: direct microbubble suspensions, aqueous carriers, liposomes (<8 microns), protein-derived microspheres (2-4 microns), crystals in saccharide diluent (5-10 microns), and emulsion- or air-bubble-swap variants.
- The most attackable points for design-around are the particle-size thresholds and carrier type constraints (sub-8 micron microbubbles; 2-4 micron microspheres; 5-10 micron crystals; aqueous carrier).
- Enforcement leverage likely tracks gas identity plus structure: if either is outside the enumerated sets or outside the structural constraints, overlap drops materially.
FAQs
1) Which claims are the broadest in US 5,573,751?
Claim 1 is broadest on gas identity because it enumerates multiple fluorinated gases and covers contrast media comprising those gaseous microbubbles. Dependent claims broaden the platform coverage by adding carrier and packaging formats (Claims 4-22).
2) Do the claims require microbubbles to be under 8 microns?
Not across the full claim set. The <8 micron requirement appears in Claims 7, 11, and 14. Other claims omit this microbubble size limitation.
3) Are perfluoropropane and perfluorobutane specifically highlighted?
Yes. Claims 4-7 cover perfluoropropane and Claims 8-11 cover perfluorobutane, including optional aqueous carriers and optional <8 micron microbubble sizes.
4) Does the patent cover liposome-based ultrasound contrast?
Yes. Claims 12-14 cover gas-filled liposomes with microbubbles containing at least one gaseous fluorine-containing chemical, including a specific fluorine chemical list in Claim 13 and <8 micron liposome size in Claim 14.
5) What is the key manufacturing “platform” captured by Claims 15-18?
They target encapsulated air-filled microspheres where the improvement is replacing air with fluorine-containing gas, with further constraints on microsphere size (2-4 microns) and denatured protein formation.
References
No external sources were provided with the prompt, and none are used here.
