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Tactile resonance method for measuring stiffness in soft tissue - evaluation of piezoelectric elements and impression depth using a silicone model
Umeå University, Faculty of Science and Technology, Department of Physics.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Detektering av styvhet i mjukvävnad med taktil resonans - utvärdering av piezoelektriska element och intryckningsdjup i en silikonmodell (Swedish)
Abstract [en]

An instrument is being developed at the Department of Biomedical Engineering; Research and Development (MT-FoU), at the University Hospital of Umeå with the aim to detect prostate cancer ex vivo.

Using a combination of tactile resonance technology and Raman spectroscopy the instrument is intended to be used in the operating room during radical prostatectomy to identify positive surgical margins.

The hypothesis was that the length of the piezoelectric element used in the tactile resonance sensor affects the sensor's sensitivity and reproducibility when measuring the stiffness of soft tissue, and that there might be an optimal impression depth to measure at.

The specific aim of this study was to evaluate two piezoelectric elements, of different lengths, by the sensitivity and reproducibility of the measurements they performed.

Measurements were performed on five silicone samples of different stiffness, during a 2 mm impression. The standard deviation of the stiffness parameters, the R2 of the linear regression used to determine the stiffness parameter, and the depth at the which the most linear relationship between impression force and frequency shift was found were studied using linear mixed-effects models to identify any significant differences between the elements.

The long element had a significantly higher R2 of 0.98 compared to 0.93 for the short element, and a higher measurement depth of 0.47 mm compared to 0.37 mm for the short element. No difference between the elements were found on accuracy as measured by standard deviation of the stiffness parameter. It was concluded that this was not enough to claim that one element was better than the other.

Abstract [sv]

Ett instrument utvecklas på avdelningen för Medicinsk teknik, forskning och utveckling, vid Norrlands universitetssjukhus med målet att detektera prostatacancer ex vivo.

Instrumentet kombinerar taktil resonansteknologi med Ramanspektroskopi och är tänkt att användas i operationssalen under radikal prostatektomi för att identifiera positiv kirurgisk marginal.

Hypotesen var att längden av det piezoleketriska element som används i den taktila resonanssensorn påverkar sensorns känslighet och reproducerbarhet vid mätning av styvhet av mjukvävnad, och att det kan finnas ett optimalt intryckningsdjup att mäta på.

Målet med denna studie var att utvärdera två piezoelektriska element, av olika längd, utifrån känsligheten och reproducerbarheten av mätningarna de utförde.

Mätningarna gjordes på fem silikonsprover av olika styvhet, under 2 mm intryckning. Standardavvikelsen av styvhetsparametern, R2 av den linjära regression som användes för att bestämma styvhetsparametern, samt det intryckningsdjup på vilket det mest linjära förhållandet mellan intryckningskraft och frekvensskift hittades, studerade med så kallade linear mixed-effects modeller för att identifiera signifikanta skillnader mellan elementen.

Det långa elementet hade ett signifikant högre R2 på 0.98 jämfört med det korta elementets 0.93, och ett högre mätdjup på 0.47 mm jämfört med det korta elementets 0.37 mm. Ingen skillnad mellan elementens standardavvikelser av styvhetsparametern hittades. Slutsatsen drogs att resultatet inte var nog för att påstå att det ena elementet är bättre än det andra.

Place, publisher, year, edition, pages
2017. , 24 p.
Keyword [en]
Tissue stiffness, Resonance sensor, Prostate cancer, Piezoelectric, Tactile sensor
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:umu:diva-137114OAI: oai:DiVA.org:umu-137114DiVA: diva2:1115314
External cooperation
Subject / course
Examensarbete i teknisk fysik
Educational program
Master of Science Programme in Engineering Physics
Presentation
2017-06-09, 13:00 (Swedish)
Supervisors
Examiners
Available from: 2017-06-27 Created: 2017-06-26 Last updated: 2017-06-27Bibliographically approved

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Tactile resonance method for measuring stiffness in soft tissue - evaluation of piezoelectric elements and impression depth using a silicone model(2275 kB)14 downloads
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