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Contact angle and indentation velocity dependency for a resonance sensor: Evaluation on soft tissue silicone models
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).
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).
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).
Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
2013 (English)In: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 37, no 3, 185-196 p.Article in journal (Refereed) Published
Abstract [en]

Human tissue stiffness can vary due to different tissue conditions such as cancer tumours. Earlier studies show that stiffness may be detected with a resonance sensor that measures frequency shift and contact force at application. Through the frequency shift and the contact force, a tissue stiffness parameter can be derived. This study evaluated how the probe application angle and indentation velocity affected the results and determined the maximum parameter errors. The evaluation was made on flat silicone discs with specified hardness. The frequency shift, the force and the stiffness parameter all varied with contact angle and indentation velocity. A contact angle of ≤10° was acceptable for reliable measurements. A low indentation velocity was recommended. The maximum errors for the system were <1.1% of the measured values. It was concluded that contact angle and indentation velocity have to be considered in the clinical setting. The angular dependency is especially important in clinical use for studying stiffness of human soft tissue, e.g. in prostate cancer diagnosis.

Place, publisher, year, edition, pages
Informa Healthcare, 2013. Vol. 37, no 3, 185-196 p.
Keyword [en]
Contact angle, Frequency shift, Indentation velocity, Resonance sensor, Tissue stiffness
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-68970DOI: 10.3109/03091902.2013.773097OAI: oai:DiVA.org:umu-68970DiVA: diva2:619212
Available from: 2013-05-02 Created: 2013-05-02 Last updated: 2017-12-06Bibliographically approved
In thesis
1. A Tactile Resonance Sensor System for Detection of Prostate Cancer ex vivo: Design and Evaluation on Tissue Models and Human Prostate
Open this publication in new window or tab >>A Tactile Resonance Sensor System for Detection of Prostate Cancer ex vivo: Design and Evaluation on Tissue Models and Human Prostate
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

The most common form of cancer among males in Europe and the USA is prostate cancer, PCa. Surgical removal of the prostate is the most common form of curative treatment. PCa can be suspected by a blood test for a specific prostate antigen, a PSA-test, and a digital rectal examination, DRE where the physician palpates the prostate through the rectum. Stiff nodules that can be detected during the DRE, and elevated levels of PSA are indications for PCa, and a reason for further examination. Biopsies are taken from the prostate by guidance of a transrectal ultrasound. Superficial cancer tumours can indicate that the cancer has spread to other parts of the body. Tactile resonance sensors can be used to detect areas of different stiffness in soft tissue. Healthy prostate tissue is usually of different stiffness compared to tissue with PCa.

Aim

The general aim of this doctoral thesis was to design and evaluate a flexible tactile resonance sensor system (TRSS) for detection of cancer in soft human tissue, specifically prostate cancer. The ability to detect cancer tumours located under the surface was evaluated through measurements on tissue phantoms such as silicone and biological tissues. Finally measurements on resected whole prostate glands were made for the detection of cancer tumours.

Methods

The sensor principle was based on an oscillating piezoelectric element that was indented into the soft tissue.  The measured parameters were the change in resonance frequency, Δf, and the contact force F during indentation. From these, a specific stiffness parameter  was obtained. The overall accuracy of the TRSS was obtained and the performance of the TRSS was also evaluated on tissue models made of silicone, biological tissue and resected whole human prostates in order to detect presence of PCa. Prostate glands are generally spherical and a special rotatable sample holder was included in the TRSS. Spherically shaped objects and uneven surfaces call for special attention to the contact angle between the sensor-tip and the measured surface, which has been evaluated. The indentation velocity and the depth sensitivity of the sensor were evaluated as well as the effect on the measurements caused by the force with which spherical samples were held in place in the sample holder. Measurements were made on silicone models and biological tissue of chicken and pork muscles, with embedded stiff silicone nodules, both on flat and spherical shaped samples. Finally, measurements were made on two excised whole human prostates.

Results

A contact angle deviating ≤ 10° from the perpendicular of the surface of the measured object was acceptable for reliable measurements of the stiffness parameter. The sensor could detect stiff nodules ≤ 4 mm under the surface with a small indentation depth of 0.4 to 0.8 mm.

Measurements on the surface of resected human prostate glands showed that the TRSS could detect stiff areas (p < 0.05), which were confirmed by histopathological evaluation to be cancer tumours on, and under the surface.

Conclusions

A flexible resonance sensor system was designed and evaluated on soft tissue models as well as resected whole prostate glands. Evaluations on the tissue models showed that the TRSS can detect stiffer volumes hidden below the surface on both flat and spherical samples. The measurements on resected human prostate glands showed that PCa could be detected both on and under the surface of the gland. Thus the TRSS provides a promising instrument aimed for stiffness measurements of soft human tissue that could contribute to a future quantitative palpation method with the purpose of diagnosing cancer. 

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 47 p.
Series
Resonance Sensor Lab, ISSN 1653-6789 ; 6
National Category
Medical Equipment Engineering
Research subject
Electronics
Identifiers
urn:nbn:se:umu:diva-86322 (URN)978-91-7601-006-8 (ISBN)
Public defence
2014-03-20, MA 121, MIT-huset, Umeå universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2014-02-26 Created: 2014-02-24 Last updated: 2014-03-24Bibliographically approved

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Publisher's full texthttp://informahealthcare.com/doi/abs/10.3109/03091902.2013.773097

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Åstrand, AndersJalkanen, VilleAndersson, Britt M.Lindahl, Olof A.
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