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OCT inom ögonsjukvård: noggrannhet hos mätfunktion
Blekinge Institute of Technology, School of Engineering, Department of Signal Processing.
2008 (Swedish)Independent thesis Basic level (degree of Bachelor)Student thesisAlternative title
OCT in ophthalmology (English)
Abstract [sv]

Denna rapport handlar om optisk koherenstomografi, Optical Coherence Tomography (OCT), en relativt ny teknik som blivit allt mer attraktiv på sjukhusens ögonkliniker. En OCT-apparat används bland annat för diagnosticering av ögonsjukdomar lokaliserade i gula fläcken och runt optiska disken. I maj 2007 köpte Ögonkliniken på Blekingesjukhuset in en 3D OCT-1000 av märket Topcon. Hos denna OCT-apparat finns en mätfunktion, Caliper, som mäter näthinnetjocklek. Studien i denna rapport syftade till att ta reda på vad Caliper mäter, hur den mäter och om den går att lita på. En OCT-undersökning utfördes på tio testpersoner. Totalt togs åtta bilder per testperson. Sju bilder togs då fotografen medvetet gjorde felinställningar eller patienten felfixerade blicken. En bild togs som referensbild med alla parametrar korrekt inställda. På alla OCT-bilder mättes avståndet mellan botten på fovea och pigmentepitelet. Därefter jämfördes mätningarna med mätvärdet hos varje testpersons referensbild. Ytterligare mätningar gjordes för att kontrollera att manuella mätningar av näthinnans medeltjocklek gav samma resultat som automatiska mätningar gjorda av OCT-apparaten. Mätningarna visade att varken fotografens felinställning eller patientens felfixering av blicken påverkade Calipers mätresultat nämnvärt. Mätavvikelser på några få mikrometer kan vara ett resultat av mänskliga mätfel. Däremot upptäcktes en ökad svårighet att mäta på bilder som var sneda eller var tagna med dålig skärpa. Studien visade också att de manuella mätningarna gav samma resultat som de automatiska. Denna undersökning kan ej besvara frågan om hur Caliper mäter då mätalgoritmen är en företagshemlighet. Den mäter avståndet mellan två olika punkter och troligtvis räknas antalet pixlar däremellan. Enligt mätningarna i denna studie går Caliper-funktionen att lita på.

Abstract [en]

This report is about Optical Coherence Tomography (OCT), a new technology with an increasing popularity at eye clinics. The OCT equipment is used for diagnostic purposes and can detect eye diseases in the area of the yellow spot and the optic nerve. In May 2007 the eye clinic at Blekingesjukhuset invested in a Topcon 3D OCT-1000. This OCT instrument has a measurement function named Caliper, which measures the retinal thickness. This study investigates what Caliper is, how it works, and its reliability. A 3D OCT examination was performed on ten test persons. For each person eight OCT images were captured. One of the images was captured with correct adjustments of the parameters and was used as a reference image. The seven remaining images were captured when the operator deliberately adjusted the parameters incorrect or the patient was focusing away from the fixation point. For all OCT images Caliper measurements were made between the bottom of fovea and the retinal pigment epithelium. All image measurements from a certain test person were compared to that person’s reference image. Additional measurements were made to investigate if manual measurements of retinal thickness give the same results as automatic measurements executed by the OCT equipment. The measurements showed that neither the operator’s incorrect adjustments nor the patient’s incorrect fixation did affect the Caliper measurements in ways worth mentioning. The measurement deviation of a few micrometres can be a result from human measurement errors. During this study an increased difficulty was observed when trying to measure skew images or less sharp images. The results of this study also show that manual and automatic measurements of mean retinal thickness give the same value. This study can not answer the question about how Caliper accomplishes its retinal thickness measurements since the measurement algorithm is a corporate secret. Caliper measures the distance between two different spots and is probably calculating the number of pixels. Finally, the measurements in this study show that Caliper is reliable.

Place, publisher, year, edition, pages
2008. , 63 p.
Keyword [sv]
OCT, Optical Coherence Tomography, Optisk Koherenstomografi, mätnoggrannhet, ögonsjukvård, näthinnetjocklek, gula fläcken
National Category
Signal Processing Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:bth-5372Local ID: oai:bth.se:arkivex3FED447FFFC1CE41C125745F004DA668OAI: oai:DiVA.org:bth-5372DiVA: diva2:832752
Uppsok
Technology
Supervisors
Available from: 2015-04-22 Created: 2008-06-05 Last updated: 2015-06-30Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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