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A flexible resonance sensor system for detection of cancer tissue: evaluation on silicon
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The most common form of cancer among men in Europe and the US is prostate cancer. When a radical prostatectomy has been found necessary, it is of interest to examine the prostate, as tumour tissue on the capsule might indicate that the cancer has metastased. This is commonly done by a microscope-based morphometric investigation. Tumour tissue is normally stiffer than healthy tissue. Sensors based on piezoelectric resonance technology have been introduced into the medical field during the last decade. By studying the change in resonance frequency when a sensor comes into contact with a material, conclusions can be drawn about the material.

A new and flexible measurement system using a piezoelectric resonance sensor has been evaluated. Three translation stages, two for horizontal movements and one for vertical movement, with stepper motors are controlled from a PC. A piezoelectric resonance element and a force sensor are integrated into a sensor head that is mounted on the vertical translation stage. The piezoelectric element is connected to a feed-back circuit and resonating at its resonance frequency until it comes into contact with a material, when a frequency shift can be observed. The force sensor is used to measure the applied force between the sensor and the material. These two parameters are combined into a third, called the stiffness parameter, which is important for stiffness evaluation. For measurements on objects with different geometries, the vertical translation stage can be aimed at a platform for flat objects or a fixture for spherical objects. The vertical translation stage is mounted on a manual rotational stage with which the contact angle between the sensor and the measured surface can be adjusted. The contact angles covered are between 0° and 35° from a line perpendicular to the surface of the measured object. The measured objects used were made from silicones of different stiffness and in the shape of flat discs and spheres. The indentation velocity of the sensor can be set at 1 mm/s to 5 mm/s. In the three papers that are the base for this licentiate thesis, we have investigated the dependence of the frequency shift, the applied force and the stiffness parameter on the contact angle, and the indentation velocity at different impression depths. The maximum error for the measurement system has also been determined.

The results of the measurements indicate that great care must be taken when aiming the sensor against the surface of the point where the measurements are to be performed. Deviations in contact angle of more than iv±10° from a line perpendicular to the surface will result in an underestimation of the frequency shift, meaning that the tissue will be regarded as stiffer than it really is. This result is important as the flat silicone models have a very even surface, which makes a controlled contact angle possible. Biological tissue can have a rough and uneven surface, which can lead to unintentional deviations in the contact angle. The magnitude of the stiffness parameter is favoured by a high indentation velocity compared to a low.

The evaluation of this measurement system has shown that it is possible to distinguish between soft and stiff silicone models, which have been used in this initial phase of the study. A new feature in this measurement system is the fixture that makes measurements on spherical objects possible and the possibility to vary the angle of contact. This is promising for future studies and measurements on whole prostate in vitro. A future application for this measurement system is to aid surgeons performing radical prostatectomy in the search for tumour tissue on the capsule of the prostate, as the presence of tumour tissue can indicate that the cancer has spread to the surrounding tissue.

Place, publisher, year, edition, pages
Umeå: Department of Applied Physics and Electronics, Umeå University , 2012. , 32 p.
Series
Resonance Sensor Lab, ISSN 1653-6789 ; 5
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-60818ISBN: 978-91-7459-477-5 (print)OAI: oai:DiVA.org:umu-60818DiVA: diva2:563418
Presentation
2012-09-21, Humanisthuset B204, Umeå universitet, Umeå, 10:00
Opponent
Supervisors
Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2015-08-11Bibliographically approved
List of papers
1. A flexible sensor system using resonance technology for soft tissue stiffness measurements: evaluation on silicone
Open this publication in new window or tab >>A flexible sensor system using resonance technology for soft tissue stiffness measurements: evaluation on silicone
2011 (English)In: 15TH NORDIC-BALTIC CONFERENCE ON BIOMEDICAL ENGINEERING AND MEDICAL PHYSICS (NBC 2011) / [ed] K. Dremstrup, S. Rees, M.Ø. Jensen, Aalborg: Springer , 2011, 21-24 p.Conference paper, Published paper (Refereed)
Abstract [en]

One of the most common forms of cancer amongmen in Europe and the United States is prostate cancer. Thecancerous tissue is less soft, and has different biomechanicalproperties compared to healthy tissue. It has been shown thattactile sensors can be used to distinguish this difference. If apiezoelectric sensor is set to oscillate at its resonance frequencythrough a feed back circuit, a frequency shift is observed whenthe sensor comes in contact with a surface. This shift can becorrelated to the stiffness of the tissue. A flexible instrumenthas been developed, with which it is possible to scan both flatand spherical bodies and where the sensor can be tilted to havedifferent contact angles. Measurements performed in thisstudy on flat silicone discs of different stiffness showed arelationship between both the frequency shift and theimpression depth for the different silicone discs, when aconstant force was applied. The results are promising forfuture studies on silicone with different geometries and finallyon prostate tissue to complete the evaluation.

Place, publisher, year, edition, pages
Aalborg: Springer, 2011
Series
IFMBE Proceedings, ISSN 1680-0737 ; 34
Keyword
Resonance sensor, Piezoelectric, Prostate cancer, Detection, Frequency shift
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:umu:diva-45160 (URN)10.1007/978-3-642-21683-1 (DOI)000308452500005 ()978-3-642-21682-4 (ISBN)
Conference
15th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics (NBC 2011), JUN 14-17, 2011, Aalborg, DENMARK
Available from: 2011-06-23 Created: 2011-06-23 Last updated: 2017-01-17Bibliographically approved
2. Stiffness measurements on spherical surfaces of prostate models using a resonance sensor
Open this publication in new window or tab >>Stiffness measurements on spherical surfaces of prostate models using a resonance sensor
2013 (English)In: World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China / [ed] Mian Long, Springer Berlin/Heidelberg, 2013, 1401-1404 p.Conference paper, Published paper (Refereed)
Abstract [en]

Prostate cancer is one of the most common formsof cancer among men in Europe and the United States.Piezoelectric resonance sensors can be used in medicalresearch for measurements of stiffness of human tissue.Cancer tissue is usually stiffer and has different biomechanicalproperties compared to healthy tissue. The frequency shiftobserved when a piezoelectric resonance sensor comes intocontact with a tissue surface has been suggested to correlatewith the stiffness variations, e.g. due to cancer. An instrumenthas been developed, with which it is possible to scan flat andspherical objects and where the sensor can be tilted fordifferent contact angles. Measurements performed in thisstudy on spherical tissue models made of silicone, showed theimportance of keeping the contact angle perpendicular to thesurface of the sphere. The results are promising for futurestudies on prostate tissue to complete the evaluation of theinstrument.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2013
Series
IFMBE Proceedings, ISSN 1680-0737 ; 39
Keyword
Resonance sensor, Piezoelectric, Prostate cancer, Detection, Frequency shift
National Category
Medical Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:umu:diva-55888 (URN)10.1007/978-3-642-29305-4_368 (DOI)978-3-642-29304-7 (ISBN)978-3-642-29305-4 (ISBN)
Conference
WC2012 World Congress on Medical Physics and Biomedical Engineering, Beijing, China, May 26-31, 2012
Available from: 2012-06-08 Created: 2012-06-08 Last updated: 2014-03-10Bibliographically approved
3. A flexible resonance sensor instrument for measurements of soft tissue: evaluation on silicone models
Open this publication in new window or tab >>A flexible resonance sensor instrument for measurements of soft tissue: evaluation on silicone models
(English)Manuscript (preprint) (Other academic)
National Category
Medical Engineering
Identifiers
urn:nbn:se:umu:diva-60821 (URN)
Available from: 2012-10-30 Created: 2012-10-30 Last updated: 2012-10-30Bibliographically approved

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