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Prostate tissue stiffness as measured with a resonance sensor system: a study on silicone and human prostate tissue in vitro.
Umeå University, Faculty of Science and Technology, Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics.
Umeå University, Faculty of Science and Technology, Applied Physics and Electronics. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics.
Umeå University, Faculty of Medicine, Medical Biosciences.
Umeå University, Faculty of Medicine, Surgical and Perioperative Sciences.
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2006 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 7, 593-603 p.Article in journal (Refereed) Published
Abstract [en]

Prostate cancer is the most common form of cancer in men in Europe and in the USA. Some prostate tumours are stiffer than the surrounding normal tissue, and it could therefore be of interest to measure prostate tissue stiffness. Resonance sensor technology based on piezoelectric resonance detects variations in tissue stiffness due to a change in the resonance frequency. An impression-controlled resonance sensor system was used to detect stiffness in silicone rubber and in human prostate tissue in vitro using two parameters, both combinations of frequency change and force. Variations in silicone rubber stiffness due to the mixing ratio of the two components could be detected (p<0.05) using both parameters. Measurements on prostate tissue showed that there existed a statistically significant (MANOVA test, p<0.001) reproducible difference between tumour tissue (n=13) and normal healthy tissue (n=98) when studying a multivariate parameter set. Both the tumour tissue and normal tissue groups had variations within them, which were assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces and different levels of dehydration for the prostates. Our results indicated that the resonance sensor could be used to detect stiffness variations in silicone and in human prostate tissue in vitro. This is promising for the development of a future diagnostic tool for prostate cancer.

Place, publisher, year, edition, pages
2006. Vol. 44, no 7, 593-603 p.
Keyword [en]
prostate tissue, stiffness, resonance sensor
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:umu:diva-19125DOI: 10.1007/s11517-006-0069-6PubMedID: 16937195OAI: oai:DiVA.org:umu-19125DiVA: diva2:201430
Available from: 2009-03-04 Created: 2009-03-04 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
Open this publication in new window or tab >>Tactile sensing of prostate cancer: a resonance sensor method evaluated using human prostate tissue in vitro
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Prostate cancer is the most frequent type of cancer in men in Europe and the USA. The methods presently used to detect and diagnose prostate cancer are inexact, and new techniques are needed. Prostate tumours can be regarded as harder than the surrounding normal healthy glandular tissue, and therefore it is of interest to be able to reliably measure prostate tissue stiffness. In this dissertation the approach was to evaluate tactile resonance sensor technology and its ability to measure mechanical properties and to detect cancer in human prostate tissue.

The tactile resonance sensor is based on a piezoelectric transducer element vibrating at its resonance frequency through a feedback circuit. A change in the resonance frequency is observed when the sensor contacts an object. This feature has been utilized to measure tissue stiffness variations due to various pathophysiological conditions.

An impression-controlled tactile resonance sensor system was first used to quantify stiffness and evaluate performance on silicone. Then the sensor system was used on fresh human prostate tissue in vitro to measure stiffness using a combination of frequency change and force measurements. Significant differences in measured stiffness between malignant and healthy normal tissue were found, but there were large variations within the groups.

Some of the variability was explained by prostate tissue histology using a tissue stiffness model. The tissue content was quantified at four depths in the tissue specimens with a microscope-image-based morphometrical method involving a circular grid. Numerical weights were assigned to the tissue data from the four depths, and the weighted tissue proportions were related to the measured stiffness through a linear model which was solved with a least-squares method. An increase in the proportion of prostate stones, stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Stroma and cancer had the greatest effect and accounted for 90 % of the measured stiffness (45% and 45%, respectively).

The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. A sensing depth was extrapolated from the numerical weights for the measurements performed at different impression depths. Horizontal surface tissue variations were studied by altering the circular grid size relative to the contact area between the sensor tip and the tissue. The results indicated that the sensing area was greater than the contact area. The sensor registered spatial tissue variations.

Tissue density-related variations, as measured by the frequency change, were weakly significant or non-significant. The measured force registered elastic-related tissue variations, to which stroma and cancer were the most important variables.

A theoretical material-dependent linear relation was found between frequency change and force from theoretical models of frequency change and force. Tactile resonance sensor measurements on prostate tissue verified this at small impression depths. From this model, a physical interpretation was given to the parameters used to describe stiffness.

These results indicate that tactile resonance sensor technology is promising for assessing soft tissue mechanical properties and especially for prostate tissue stiffness measurement with the goal of detecting prostate cancer. However, further studies and development of the sensor design must be performed to determine the full potential of the method and its diagnostic power. Preferably, measurements of tissue mechanical properties should be used in combination with other methods, such as optical methods, to increase the diagnostic power.

Place, publisher, year, edition, pages
Umeå: Tillämpad fysik och elektronik, 2007. 70 p.
Series
Resonance Sensor Lab, ISSN 1653-6789 ; 4
Keyword
tactile resonance sensor, prostate tissue, prostate cancer, stiffness, density, elastic, variations, tissue histology
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:umu:diva-1445 (URN)978-91-7264-461-8 (ISBN)
Public defence
2007-12-14, N430, Naturvetarhuset, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2007-11-22 Created: 2007-11-22 Last updated: 2011-03-30Bibliographically approved
2. Resonance sensor technology for detection of prostate cancer
Open this publication in new window or tab >>Resonance sensor technology for detection of prostate cancer
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Prostate cancer is the most common type of cancer in men in Europe and the USA. Some prostate tumours are regarded as stiffer than the surrounding normal tissue, and therefore it is of interest to be able to reliably measure prostate tissue stiffness. The methods presently used to detect prostate cancer are inexact, and new techniques are needed. In this licentiate thesis resonance sensor technology, with its ability to measure tissue stiffness, was applied to normal and cancerous prostate tissue.

A piezoelectric transducer element in a feedback system can be set to vibrate at its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various pathophysiological conditions.

An impression-controlled resonance sensor system was used to quantify stiffness in human prostate tissue in vitro using a combination of frequency change and force measurements. Measurements on prostate tissue showed statistically significant (p < 0.001) and reproducible differences between normal healthy tissue and tumour tissue when using a multivariate parameter analysis. Measured stiffness varied in both the normal tissue and tumour tissue group. One source of variation was assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces, different levels of dehydration of the prostates, and actual differences between patients.

The prostate specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5–1.7 mm, the maximum coefficient of determination was R2 ≥ 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed.

It is concluded that prostate cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differentiate from cancer. Furthermore, the results of this study indicated that the resonance sensor could be used to detect stiffness variations in human prostate tissue in vitro, and especially due to prostate cancer. This is promising for the development of a future diagnostic tool for prostate cancer.

Place, publisher, year, edition, pages
Umeå: Fysik, 2006. 47 p.
Series
Resonance Sensor Lab, ISSN 1653-6789 ; 2
Keyword
resonance sensor, prostate tissue, stiffness, detecting prostate cancer
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:umu:diva-896 (URN)91-7264-153-3 (ISBN)
Presentation
(English)
Supervisors
Available from: 2006-10-17 Created: 2006-10-17 Last updated: 2010-02-01Bibliographically approved

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