# US 2018/0024048 A1 · Optical technique for coating characterization > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0024048 A1 - Document ID: US20180024048A1 - Status: Published application - Kind: A1 - Application number: 15/652,583 - Filed: 2017-07-18 - Published: 2018-01-25 - Earliest claimed: 2016-07-20 - Assignees: Cook Medical Technologies LLC - Applicants: Cook Medical Technologies LLC - Inventors: John Neilan; Syed A.M. Tofail; Rabah Mouras; Christophe Silien; Aladin Mani; David Murray - Web page: https://patentgrep.com/patent/US20180024048A1 ## CPC - G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence) - A61L 29/16: Biologically active materials, e.g. therapeutic substances {(A61L29/048 takes precedence)} - A61L 31/08: Materials for coatings - A61L 31/16: Biologically active materials, e.g. therapeutic substances {(A61L31/047 takes precedence)} - G01B 9/04: Measuring microscopes - G01B 11/0641: {with measurement of polarization} - G02B 21/0092: {Polarisation microscopes} - A61L 2300/416: Anti-neoplastic or anti-proliferative or anti-restenosis or anti-angiogenic agents, e.g. paclitaxel, sirolimus - A61L 2300/606: Coatings - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract The present invention generally relates to methods for determining the presence and distribution of a polarization active material present in a coating. In one embodiment, the coating is present on an implantable device, for example an implantable stent. ## Claims ### Claim 1 A method for determining a distribution of a first polarization active compound in a coating, comprising: utilizing optical microscopy to obtain images at a plurality of planes at differing axial positions between an upper and a lower boundary of the coating; measuring a distribution of polarization activity within each of the images, wherein the distribution is based on a distribution in polarization of light within the plurality of images; constructing a three dimensional distribution based on the distribution of polarization active material within each of the plurality of images; and determining the distribution of the first polarization active compound in the coating based on the three dimensional polarization activity distribution. ### Claim 2 (depends on 1) The method of claim 1, wherein the first polarization active compound is a crystalline taxane polymorph. ### Claim 3 (depends on 2) The method of claim 2, wherein the crystalline taxane polymorph is a crystalline paclitaxel polymorph. ### Claim 4 (depends on 3) The method of claim 3, therein coating is a coating on an implantable device. ### Claim 5 (depends on 4) The method of claim 4, therein the implantable device is selected from the group consisting of a stent and a balloon. ### Claim 6 (depends on 5) The method of claim 5, wherein the stent is a vascular stent. ### Claim 7 (depends on 1) The method of claim 1, wherein the coating consists essentially of the first polarization active compound and wherein the first polarization active compound is a drug. ### Claim 8 (depends on 7) The method of claim 7, wherein the drug of a taxane. ### Claim 9 (depends on 8) The method of claim 8, wherein the taxane is paclitaxel. ### Claim 10 (depends on 1) The method of claim 1, wherein the coating is free of a polymeric or non-polymeric carrier material. ### Claim 11 (depends on 1) The method of claim 1, further comprising determining a distribution of a second polarization active compound in the coating based on the three dimensional birefringence distribution, wherein the first polarization active compound and the second polarization active compound exhibit different polarization activity properties. ### Claim 12 (depends on 11) The method of claim 11, wherein the first polarization active compound and the second polarization active compound are crystalline polymorphs of paclitaxel. ### Claim 13 (depends on 12) The method of claim 12, wherein the first polarization active compound is dihydrate paclitaxel and wherein the second polarization active compound is anhydrous paclitaxel. ### Claim 14 (depends on 1) The method of claim 1, wherein the coating further comprises a non-polarization active drug. ### Claim 15 (depends on 1) The method of claim 1, wherein the optical microscopy is dual-beam confocal optical microscopy. ### Claim 16 (depends on 1) The method of claim 1, further comprising determining an axial position of a first and a second of the plurality of focal planes and determining a thickness of the coating based the axial position the first and the second focal planes; wherein the first focal plane is positioned at an upper boundary of the coating and wherein the second focal plane is positioned at a lower boundary of the coating. ### Claim 17 (depends on 1) The method of claim 1, there the optical microscopy comprises illuminating the coating with laser light at a wavelength selected from the group consisting of 786 nm, 380 nm and 229 nm. ### Claim 18 A method for determining a distribution of a crystalline paclitaxel polymorph in a coating, comprising: utilizing optical microscopy to obtain images at a plurality of focal planes at differing axial positions between an upper and a lower boundary of the coating; measuring a polarization activity distribution within each of the plurality of images, wherein the polarization activity distribution is based on a distribution in polarization of light within the plurality of images; constructing a three dimensional birefringence distribution based on the polarization activity distribution within each of the plurality of images; and determining the distribution of the crystalline paclitaxel polymorph in the coating based on the three dimensional polarization activity distribution, wherein the coating is a coating on an on an implantable vascular stent.